The invention relates to substantially single phase silicone copolycarbonates suitable for use in optical articles such as digital versatile disks. The silicone copolycarbonates contain residues of silicone containing and nonsilicone containing bisphenols and have properties particularly suited for use in high density optical data storage media. The invention further relates to the preparation and properties of substantially single phase silicone copolycarbonates having either a blocky or a random structure. The structure of the compositions of the invention is determined by the method of preparation used and may be used to control physical properties.

This invention relates to substantially single phase silicone copolycarbonates suitable for use in optical articles, methods for making such silicone copolycarbonates and methods for controlling the physical properties of silicone copolycarbonates. Material properties of silicone copolycarbonates are found to be controlled both by composition and method of preparation. Control of product properties by method of preparation is provided by two methods which provide identically constituted materials having different physical properties. This invention further relates to optical articles, and methods for making optical articles from the silicone copolycarbonates.
The past two decades have seen tremendous growth in the use of optical plastics in information storage and retrieval technology. Polycarbonates and other polymer materials are utilized widely in optical data storage media, such as compact disks. In optical data storage applications, it is desirable that the plastic material chosen have excellent performance characteristics such as high transparency, low water affinity, good molding characteristics, substantial heat resistance and low birefringence. Low water affinity is particularly desirable in optical data storage media applications in which disk flatness is affected by water absorption. In xe2x80x9cread throughxe2x80x9d applications successful employment of a particular optical plastic requires that it be readily molded into disks embossed with a series of very fine grooves and pits which govern critical aspects of data storage and retrieval. Replication of these grooves and pits during molding must occur with high precision and a high level of disk to disk uniformity must be achieved. Moreover the material itself must not stick to or foul the mold surfaces. Water affinity, molding characteristics, thermal and optical properties are properties of the material itself and will ultimately depend upon the structure of the optical polymer. Efforts to maximize desirable properties and repress undesirable properties in optical polymers have been intense. The chief means of discovery in this area has been through chemical synthesis and testing of new materials. Many different polymer types and structures have been prepared and evaluated. However, because each new application may require a different balance of material characteristics not currently provided by known materials, efforts directed to the discovery of new polymers has continued.
Silicone copolycarbonates as a class exhibit poor miscibility of the silicone and polycarbonate repeat units and a marked tendency toward segregation into predominantly silicone-containing and polycarbonate containing phases. This behavior limits the utility of silicone copolycarbonates. There exists a need for silicone copolycarbonate compositions which are, as defined herein, substantially single phase, which have excellent processability and low water affinity, and are suitable for use in high density optical recording media.
The present invention provides substantially single phase silicone copolycarbonates suitable for use in optical data storage applications. These and further embodiments of the invention will be more readily appreciated when considering the following disclosure and appended claims.
In one aspect, the invention relates to a substantially single phase silicone copolycarbonate comprising:
a. a repeat unit having structure I
xe2x80x83wherein R1 and R2 are each independently at each occurrence halogen, C1-C6 alkyl or aryl,
m and n are each independently integers from 0-4,
W is a linking moiety selected from the group consisting of: a bond, a C2-C18 alkylidene group, a C3-C12 cycloalkylidene group, a carbon atom optionally substituted by one or two hydrogen atoms or one or two C6-C10 aryl groups or one or two C1-C18 alkyl groups; an oxygen atom, a sulfur atom, a sulfonyl (SO2) group and a carbonyl (CO) group; and
b. repeat units having structure II
xe2x80x83wherein R3 is a C2-C10 alkylene group optionally substituted by one or more C1-C10 alkyl or one or more aryl groups; an oxygen atom or an oxyalkyleneoxy moiety such as:
xe2x80x94Oxe2x80x94(CH2)txe2x80x94Oxe2x80x94
xe2x80x83or an oxyalkylene moiety such as:
xe2x80x94)xe2x80x94(CH2)txe2x80x94xe2x80x83xe2x80x83
xe2x80x83where t is an integer from 2-20;
and where R4 and R5 are each independently at each occurrence C1-C6 alkoxy, C1-C6 alkyl or aryl;
z and q are independently integers from 0-4; and further
R6, R7, R8 and R9 are each independently at each occurrence C1-C6 alkyl, aryl, C2-C6 alkenyl, cyano, trifluoropropyl or styrenyl;
and p is an integer from 0-20.
This invention further relates to methods of making these silicone copolycarbonates and methods for controlling physical properties of identically constituted silicone copolycarbonates by choice of preparation method. Two methods of preparation are disclosed. In Method 1 interfacial polymerization of the starting monomers with phosgene affords a product having a blocky structure and higher glass transition temperature than an identically constituted product produced by Method 2. In Method 2, reaction of an oligomeric, non-silicone-containing bischloroformate with a silicone-containing bisphenol affords a product with a random structure and glass transition temperature lower than an identically constituted product produced by Method 1. Still further, this invention relates to optical articles made from the silicone copolycarbonates and methods of making said optical articles.
The present invention may be understood more readily by reference to the following description of preferred embodiments of the invention and the Examples included herein.
It is to be understood that this invention is not limited to specific synthetic methods or to particular compositions falling within the class of substantially single phase silicone copolycarbonates. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The singular forms xe2x80x9ca,xe2x80x9d xe2x80x9canxe2x80x9d and xe2x80x9cthexe2x80x9d include plural referents unless the context clearly dictates otherwise.
xe2x80x9cOptionalxe2x80x9d or xe2x80x9coptionallyxe2x80x9d means that the subsequently described event or circumstance may or may not occur, and that description includes instances where the event or circumstance occurs and instances where it does not.
xe2x80x9cBPAxe2x80x9d is herein defined as bisphenol A or 2,2-bis(4-hydroxyphenyl)propane. xe2x80x9cBCCxe2x80x9d is herein defined as 1,1-bis(4-hydroxy-3-methylphenyl) cyclohexane.
xe2x80x9cBPIxe2x80x9d is herein defined as 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
xe2x80x9cBPZxe2x80x9d is herein defined as 1,1-bis-(4-hydroxyphenyl)cyclohexane
xe2x80x9cCgxe2x80x9d is the stress optical coefficient of a polymeric material in the glassy state, measured in Brewsters (10xe2x88x9213 cm2/dyne)
xe2x80x9cCpxe2x80x9d represents the heat capacity of a material.
xe2x80x9cDegree of oligomerizationxe2x80x9d as used herein refers to the value of r in structural formula IV.
xe2x80x9cIdentically constitutedxe2x80x9d as used herein refers to silicone copolycarbonates which have roughly the same molecular weight and which contain the same relative number of moles of repeat units I and II, said relative number of moles of repeat units I and II being determined by nuclear magnetic resonance spectroscopy (NMR). Two silicone copolycarbonates are defined herein as having roughly the same molecular weight when each exhibits an Mw value which is within 10% of the Mw value measured for the other composition by gel permeation chromatography (gpc) using polystyrene standards.
xe2x80x9cMTBACxe2x80x9d is herein defined as methyltributyl ammonium chloride.
xe2x80x9cOptical data storage mediaxe2x80x9d or an xe2x80x9coptical data storage mediumxe2x80x9d refers to an article which may be encoded with data and which is read by optical means.
xe2x80x9cOptical articlesxe2x80x9d as used herein include optical disks and optical data storage media, for example a rewritable or read only compact disk (CD), a digital versatile disk, also known as DVD, random access memory disks (RAM), magneto optical (MO) disks and the like; optical lenses, such as contact lenses, lenses for glasses, lenses for telescopes, and prisms; optical fibers; information recording media; information transferring media; high density data storage media, disks for video cameras, disks for still cameras and the like; as well as the substrate onto which optical recording material is applied. In addition to use as a material to prepare optical articles, the substantially single phase silicone copolycarbonate may be used as a raw material for films or sheets.
xe2x80x9cOptical polymer xe2x80x9d refers to a polymeric material having physical characteristics compatible with use in optical data storage devices wherein light is passed through the polymeric material as part of a data reading or writing operation such as in read through optical data storage devices. The term xe2x80x9coptical polymerxe2x80x9d is used interchangeably with the term xe2x80x9coptical plasticxe2x80x9d.
xe2x80x9cSilicone copolycarbonatexe2x80x9d refers to a copolycarbonate containing both carbonate and silicone structural units. It is used herein to describe both the substantially single phase silicone copolycarbonates of the present invention as well as copolycarbonates containing silicone structural units which fall outside of the scope of the present invention.
xe2x80x9cSubstantially single phase silicone copolycarbonatexe2x80x9d is defined as a silicone copolycarbonate prepared from both silicone-containing bisphenols of formula V and non-silicone-containing bisphenols of formula III the copolycarbonate having a Tg which follows the mixing rule:
1/Tg=w1(1/Tg1)+w2(1/Tg2)
where w1 and w2 are the weight fractions of silicone containing and non-silicone containing bisphenols employed and Tg1 and Tg2 are the glass transition temperatures of the homopolycarbonates derived from the silicone-containing and non-silicone-containing bisphenols respectively.
xe2x80x9cStyrenylxe2x80x9d is defined as a 2-phenyleth-1-yl or a 1-phenyleth-1-yl group.
xe2x80x9cTrifluoropropylxe2x80x9d is defined as the 3,3,3-trifluoroprop-1-yl group.
Unless otherwise stated, xe2x80x9cmole percentxe2x80x9d in reference to the composition of a silicone copolycarbonate or polycarbonate in this specification is based upon 100 mole percent of the repeating units of the silicone copolycarbonate or polycarbonate. For instance, xe2x80x9ca silicone copolycarbonate comprising 90 mole percent of BPAxe2x80x9d refers to a silicone copolycarbonate in which 90 mole percent of the repeating units are residues derived from BPA or its corresponding derivative(s). Corresponding derivatives include but are not limited to, the polycarbonate oligomers of BPA terminated by chloroformate groups, referred to here as xe2x80x9coligomeric bischloroformatexe2x80x9d and xe2x80x9coligomeric bischloroformatesxe2x80x9d.
The terms xe2x80x9cmole percentxe2x80x9d, xe2x80x9cmole %xe2x80x9d and xe2x80x9cmol %xe2x80x9d are used interchangeably throughout this application and have the meaning given above for xe2x80x9cmole percentxe2x80x9d.
xe2x80x9cWt % Sixe2x80x9d (Weight percent siloxane) denotes the weight of [R8R9 SiO] units in a given silicone copolycarbonate polymer relative to the total weight of the silicone copolycarbonate polymer. It is obtained by multiplying the weight in grams of the silicone containing bisphenol used times the weight fraction of [R8R9 SiO] units in the bisphenol and dividing the product by the total weight in grams of all of the bisphenol monomers used in the preparation of the silicone copolycarbonate.
The terms xe2x80x9cresiduesxe2x80x9d and xe2x80x9cstructural unitsxe2x80x9d, used in reference to the constituents of the silicone copolycarbonate, are synonymous throughout the specification.
Silicone copolycarbonates as a class are prized for their improved ductility, flow and mold release behavior relative to polycarbonates which do not contain silicone. However, it is observed that silicone copolycarbonates typically phase segregate into silicone and polycarbonate phases. In many applications separation of a copolymer into separate phases presents a critical limitation upon its utility. The use of silicone copolycarbonates in read through optical data storage devices is limited by the tendency of these materials to phase separate. Phase separation negatively affects the percentage of light transmitted by the material (% light transmission) during disk reading and writing which correspondingly limits utility. Silicone copolycarbonates which were not phase separated would be useful as substrates for optical data storage devices since they would possess the excellent ductility, flow and molding properties of known phase separated silicone copolycarbonates but might additionally possess excellent light transmission, birefringence and water absorption behaviors.
Phase separation is detected by various means including percent light transmission measurements, scanning electron microscopy and glass transition temperature (Tg) behavior. Glass transition temperature is a convenient means to monitor phase behavior in silicone copolycarbonates. Known silicone copolycarbonates exhibit two glass transition temperatures, because they possess separate silicone and polycarbonate phases. This is particularly so in the case of silicone copolycarbonates possessing polydimethylsiloxane and bisphenol A polycarbonate repeat units. Such a silicone copolycarbonate behaves as though it were an immiscible blend of polycarbonate and polydimethylsiloxane polymers. Distinct Tg""s characteristic of the polycarbonate and silicone homopolymers are observed. A consequence of this behavior is that for known silicone copolycarbonates the Tg of the polycarbonate phase is essentially unaffected by the relative amount of the silicone-containing component employed.
The tendency of a silicone copolycarbonate to behave as though it were an immiscible blend of a silicone polymer and polycarbonate represents an important limitation on its utility. The present invention overcomes this limitation by providing substantially single phase silicone copolycarbonates. It has been discovered that by carefully controlling the structure of the silicone-containing bisphenol corresponding to repeat unit II silicone copolycarbonates are obtained which unexpectedly behave as though they were substantially single phase materials. The Tg""s of the substantially single phase silicone copolycarbonates of this invention are found to be intermediate between the glass transition temperatures of the corresponding homopolycarbonates of the silicone-containing bisphenol and non-silicone-containing bisphenol, Tg1 and Tg2 respectively. Moreover, the Tg""s of the silicone copolycarbonates of the present invention are consistent with the following expression (mixing rule):
xe2x80x831/Tg=w1(1/Tg1)+w2(1/Tg2)
where w1 and w2 are the weight fractions of silicone containing and non-silicone containing bisphenol respectively and Tg1 and Tg2 are defined as above. Thus the substantially single phase silicone copolycarbonates of the present invention exhibit a glass transition temperature which is dependent upon the weight fractions of the component silicone-containing and non-silicone containing bisphenols. In some instances the Tg mixing rule described above may become nonlinear and curvature at high values of w1 or w2 can be detected. In such cases the mixing rule need not accurately predict the observed Tg but rather need only predict the direction of the Tg change brought about by changing the weight fractions of the silicone-containing and non-silicone-containing bisphenols employed.
In one of its embodiments the present invention provides a substantially single phase silicone copolycarbonate exhibiting a Tg which is not only dependent upon composition, the relative amounts of residues I and II, but is also dependent upon the method of polymer preparation employed. The method of preparation may sometimes mask the effect of varying the relative amounts of the component monomers upon the Tg of the product silicone copolycarbonate. As such, the mixing rule described above has predictive value within a series of compositions in which the relative amounts of repeat units I and II vary when the materials are prepared by the same chemical process. This aspect of the present invention is further illustrated in the sections which follow.
When the substantially single phase silicone copolycarbonate containing repeat units I and II is prepared from a silicone containing bisphenol such as eugenol siloxane bisphenol and a non-silicone containing bisphenol such as BPA, it has been found that the value of p in structure II, the number of [Me2SiO] units present, must be in the range from about 0 to about 20. Otherwise, a phase segregated silicone copolycarbonate is obtained, regardless of the method of polymer preparation employed.
In a further embodiment the present invention provides a substantially single phase silicone copolycarbonate composition having increased utility in the preparation of molded optical articles relative to known silicone copolycarbonates in which the silicone and polycarbonate components phase segregate and the material behaves like an immiscible blend of a silicone polymer and a polycarbonate wherein the Tg of the polycarbonate phase is largely unaffected by the presence of, or amount of, the silicone containing phase. Thus, unlike known phase segregated silicone copolycarbonates, the compositions of the present invention are susceptible to the adjustment of glass transition temperature and those processing characteristics dependent upon glass transition temperature by varying the amount of the silicone comonomer employed in their preparation.
The present invention also provides an additional tool which augments compositional control of physical properties of substantially single phase silicone copolycarbonates. Thus, the inventors have discovered that the physical properties of certain substantially single phase silicone copolycarbonates of the invention are dependent not only upon the structure and amount of the monomers employed but also upon the method of polymer synthesis employed. The inventors have discovered, for example, that the glass transition temperature and other physical properties of two substantially single phase silicone copolycarbonates prepared using identical amounts of eugenol siloxane bisphenol and BPA may vary depending on whether the copolycarbonate was prepared by reaction of the mixture of these two monomers with phosgene directly or whether the copolycarbonate was prepared by reaction of eugenol siloxane bisphenol with an oligomeric bischloroformate prepared from the BPA (See, for example, Table 4, Examples 34-37).
In some instances it has been found that when a mixture comprising the bisphenol monomers III and V is combined with a solvent and reacted with phosgene in the presence of water, an acid acceptor and optionally a phase transfer catalyst (i.e. interfacial conditions), the rates of reaction of the bisphenol monomers III and V with phosgene or a chloroformate end group on a growing polymer chain are different enough to give compositions which are blocky. The degree to which a polymer has a blocky, or in the alternative, a random structure is determined by NMR. For the purposes of the present invention a blocky silicone copolycarbonate is defined as one in which the average block length of repeat unit II is greater than about 2. Bisphenols bearing substituents ortho to the OH group, such as eugenol siloxane bisphenol, are typically less reactive than unsubstituted bisphenols such as BPA. Phosgenation of a mixture of eugenol siloxane bisphenol having pxe2x89xa620 and BPA gives a blocky, substantially single phase silicone copolycarbonate.
The blocky substantially single phase silicone copolycarbonates comprising repeat units having structure I and repeat units having structure II are prepared by reaction of a mixture of bisphenols III and V and from about 0 to about 7 mole percent monophenol VI, based on total moles of III and V, with phosgene in the presence of an organic solvent, water, an acid acceptor and optionally a phase transfer catalyst. Thus, a mixture of bisphenols III and V together with monophenol VI is combined with an organic solvent and water and optionally a phase transfer catalyst. Sufficient aqueous alkali metal hydroxide or alkaline earth metal hydroxide is added to bring the pH of the reaction mixture to a pH value in the range between about 9 and about 12 with a pH of about 10.5 being preferred. Phosgene is then introduced into the reaction mixture together with sufficient hydroxide to maintain a pH of about 10.5. When the desired amount of phosgene has been introduced, usually an amount in the range of between about 100 mole % and about 200 mole % based on total moles of bisphenols III and V employed, the reactor is purged of any excess phosgene and the product substantially single phase silicone copolycarbonate having a blocky structure is isolated.
Suitable organic solvents which can be used are, for example, chlorinated aliphatic hydrocarbons, such as methylene chloride, carbon tetrachloride, dichloroethane, trichloroethane and tetrachloroethane; substituted aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene, and the various chlorotoluenes. The chlorinated aliphatic hydrocarbons, especially methylene chloride, are preferred.
Alkali metal or alkaline earth metal hydroxides which can be employed are, for example, sodium hydroxide, potassium hydroxide, and calcium hydroxide. Sodium and potassium hydroxides, and particularly sodium hydroxide are preferred.
Suitable phase transfer catalysts (PTC) are illustrated by but are not limited to the following: Et3N, [CH3(CH2)3]4NZ, [CH3(CH2)3]4PZ, [CH3(CH2)5]4NZ, [CH3(CH2)6]4NZ, [CH3(CH2)4]4NZ CH3[CH3(CH2)2]3NZ, and CH3[CH3(CH2)3]3NZ, where Z is selected from Cl or Br.
Alternatively bisphenol component III is first oligomerized in the presence of excess phosgene to a give an oligomeric bischloroformate IV wherein r has a value in a range between about 1 and about 20 and preferably in a range a range between about 5 and about 10. The bischloroformate IV is then reacted with the silicone containing bisphenol V in a solvent in the presence of water, an acid acceptor and optionally a phase transfer catalyst to give a silicone copolycarbonate having a random structure. A silicone copolycarbonate having a random structure is defined herein as one in which the average block length of repeat unit II is about 1. In order to achieve incorporation of all of the components and an average block length of repeat unit II of about 1 there must be a preponderance of chloroformate groups of bischolorformate oligomer IV relative to the number of OH groups of silicone-containing bisphenol V. In some instances, as when a very small amount of the silicone-containing bisphenol is employed, for example less than 1 mole percent relative to the number of moles of repeat units I present in the oligomeric bischloroformate IV, the number of chloroformate end groups remaining after the reaction of bischloroformate IV with bisphenol V and monophenol VI may be substantial and the molecular weight of the product insufficient to afford the properties desired. Chloroformate end groups may be hydrolyzed by base to afford phenolic end groups which react further with remaining chloroformate end groups to build molecular weight of the product silicone copolycarbonate. For these reasons the average block length of repeat unit I in substantially single phase silicone copolycarbonates having a random structure prepared by reaction of an oligomeric bischloroformate IV with a silicone-containing bisphenol V and a monophenol VI is always at least the value of r.
In structures III and IV R1 and R2 each represent independently at each occurrence halogen, C1-C6 alkyl or aryl groups; m and n are independently integers from 0-4; and r is an integer from 1-20. W is a linking moiety selected from the group consisting of: a bond, a C2-C18alkylidene group, a C3-C12 cycloalkylidene group, a carbon atom optionally substituted by one or two hydrogen atoms or C6-C10 aryl groups or C1-C18 alkyl groups;
an oxygen atom, a sulfur atom, a sulfonyl (SO2) group and a carbonyl (CO) group.
Thus, a bisphenol III is mixed with an organic solvent and optionally a phase transfer catalyst. Sufficient aqueous alkali metal hydroxide or alkaline earth hydroxide is added to raise the pH of the bisphenol reaction mixture prior to phosgenation, to a value of about 10.5. This can result in the dissolution of some of the bisphenol into the aqueous phase. Aqueous alkali, or alkaline earth metal hydroxide is used to maintain the pH of the phosgenation mixture near the desired pH for the reaction, which is in a range of between about 8 and about 10.5. The pH can be regulated by recirculating the reaction mixture past a pH electrode which regulates the rate of addition of the aqueous alkali metal or alkaline earth metal hydroxide.
When the bisphenol III has been converted to the oligomeric bischloroformate IV the silicone containing bisphenol V and monophenol VI may be introduced
wherein R3 is a C2-C10 alkylene group optionally substituted by one or more C1-C10 alkyl or aryl groups, an oxygen atom or an oxyalkyleneoxy moiety such as
xe2x80x94)xe2x80x94(CH2)txe2x80x94Oxe2x80x94
or an oxyalkylene moiety such as
xe2x80x94)xe2x80x94(CH2)txe2x80x94
where t is an integer from 2-20;
R4 and R5 are each independently at each occurrence C1-C6 alkoxy, C1-C6 alkyl or aryl;
z and q are independently integers from 0-4;
R6, R7, R8 and R9 are each independently at each occurrence C1-C6 alkyl, aryl, C2-C6 alkenyl, cyano, trifluoropropyl, styrenyl;
p is an integer from 0-20;
R10 is a C1-C20 alkyl group optionally substituted by one or more C6-C10 aryl groups; a C1-C20 alkoxy group optionally substituted by one or more C6-C10 aryl groups; and
s is an integer from 0-5.
The pH of the mixture then may be raised to between about 10 and about 12 and additional phase transfer catalyst added. Reaction of bischloroformate IV with a silicone containing bisphenol having structure V and a monofunctional phenol VI in the presence of a solvent, water, an acid acceptor and optionally a phase transfer catalyst affords a silicone containing copolycarbonate incorporating repeat units I and II and terminal groups derived from VI having a random structure. Suitable solvents, alkali metal hydroxides and phase transfer catalysts are those described herein as being useful in the preparation of substantially single phase silicone copolycarbonates having a blocky structure.
After reaction between the silicone containing bisphenol V, monophenol VI and the oligomeric bischloroformate IV is complete the reaction mixture may be checked for the presence of unreacted chloroformate end groups. These may be eliminated by the introduction of a small amount of a tertiary amine, such as triethylamine, or additional bisphenol III or V or additional monophenol VI.
In one embodiment the present invention provides substantially single phase silicone copolycarbonates in which repeat unit I is preferably
represented by structure VII wherein W is defined as in formula I; and repeat unit II is preferably represented by formula VIII wherein R3, R4, R5 and p are defined as in formula II. In addition, it has been found that it is particularly
preferred that repeat unit I be represented by structure IX and that repeat unit II be represented by formula X.
In another embodiment the present invention provides substantially single phase silicone copolycarbonates in which it is preferred that repeat unit I be represented by structure XI and that repeat unit II be represented by formula X.
Representative units of bisphenol III used in the preparation of both blocky and random substantially single phase silicone copolycarbonates include, but are not limited to residues of 2,2-bis(4-hydroxyphenyl)propane (BPA); 2,2-bis(4-hydroxyphenyl)butane; 2,2-bis(4-hydroxyphenyl)pentane; 2,2-bis(4-hydroxy-3-methylphenyl)propane; 2,2-bis(3-ethyl-4-hydroxyphenyl)propane; 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane; 1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane; 1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane. Residues of BPA are preferred as bisphenol III.
Representative examples of siloxane-containing bisphenols V include, but are not limited to eugenol siloxane bisphenol and other siloxane containing bisphenols shown below in which p is an integer from 0 to 20.
The representative siloxane bisphenols 4-allyl-2-methylphenol siloxane bisphenol, 4-allylphenol siloxane bisphenol, 2-allylphenol siloxane bisphenol, 4-allyloxyphenol siloxane bisphenol and 4-vinylphenol siloxane bisphenol are named after the aliphatically unsaturated phenols from which they are prepared. Thus, the name eugenol siloxane bisphenol denotes a siloxane bisphenol prepared from eugenol (4-allyl-2-methoxyphenol). Similarly the name 4-allyl-2-methylphenol siloxane bisphenol indicates the siloxane bisphenol prepared from 4-allyl-2-methylphenol. The other names given follow the same naming pattern.
Siloxane bisphenols are prepared by hydrosilylation of an aliphatically unsaturated phenol with a siloxane dihydride in the presence of a platinum catalyst. This process is illustrated below for eugenol siloxane bisphenol.
In one of its embodiments the present invention is directed to the use of siloxane dihydrides having up to 20 [Me2OSi] repeat units in the preparation of siloxane containing bisphenols. Siloxane dihydrides having up to 20 repeat units may be prepared by equilibration of tetramethyldisiloxane with a cyclic siloxane such as octamethylcyclotetrasiloxane in the presence of an acid catalyst. Reaction of the siloxane dihydride with an aliphatically unsaturated phenol in the presence of a platinum catalyst affords the siloxane-containing bisphenol.
Alternatively, an aliphatically unsaturated phenol may be reacted with tetramethyldisiloxane in the presence of a platinum catalyst to give a siloxane bisphenol V in which p has a value of 1. Equilibration of said siloxane bisphenol with a source of [Me2SiO] units such as octamethylcyclotetrasiloxane in the presence of an acid catalyst then affords a siloxane bisphenol V having a value of p greater than 1.
Aliphatically unsaturated phenols are illustrated by but not limited to 4-allyl-2-methoxyphenol (eugenol), 2-allylphenol, 4-allyl-2-methylphenol, 4-allylphenol, 4-allyloxyphenol and 4-vinylphenol.
Monophenols VI are typically added as a means of controlling the molecular weight of the siloxane copolycarbonate and the identity of the polymer end groups. Typically the amount of monophenol VI employed is in a range from about 0 mole percent to about 7 mole percent based on the total moles of repeat units I and II. Suitable monophenols are exemplified by, but not limited to, the following: phenol; 4-t-butylphenol; 4-cumylphenol; 3,5-dimethylphenol and 2,4-dimethylphenol.
The substantially single phase silicone copolycarbonates of the present invention may comprise repeat units I in a range between about 60 mole % and about 99.9 mole % and repeat units II in a range between about 0.1 mole % and about 40 mole %. Generally it is preferred that the silicone copolycarbonates of the present invention comprise repeat units I in a range between about 80 mole % and about 99.9 mole % and repeat units II in a range between about 20 mole % and about 0.1 mole %. Substantially single phase silicone copolycarbonates comprising repeat units I in a range between about 90 mole % and about 99.5 mole % and repeat units II in a range between about 0.5 mole % and about 10 mole % are especially preferred.
In one of its embodiments the present invention provides substantially single phase silicone copolycarbonates in which the value of the integer p in repeat unit II is more preferably less than about 5. In such cases it has been discovered that repeat units I and II show enhanced compatibility with one another in copolymers containing them and such copolymers are especially resistant to phase segregation. However, when the value of p is in the range between about 10 and about 20 the use of more than about 20 mole % of the silicone containing comonomer V may result in compositions in which the silicone and polycarbonate phases tend to segregate. Thus, it has been discovered that when preparing the compositions of the present invention where the value of p is in the range from about 10 to about 20 the silicone containing bisphenol V be limited to no more than about 20 mole % of the total amount of bisphenol employed and preferably no more than about 10 mole %.
In one of its embodiments the present invention provides substantially single phase silicone copolycarbonates in which the value of the integer p in repeat unit II is more preferably about 2 or less. In such cases it has been discovered that the stress optical coefficient, Cg, is substantially reduced relative to BPA polycarbonate by an amount greater than would be predicted by a simple dilution model whereby the relatively highly birefringent BPA polycarbonate is diluted with a non-birefringent diluant. This effect is illustrated in Table 5 of the examples for substantially single phase silicone copolycarbonates containing repeat units based upon BPA and eugenol siloxane bisphenol respectively.
The substantially single phase silicone copolycarbonates of the present invention may optionally be blended with other polymers such as polycarbonates, copolycarbonates, copolyestercarbonates and polyesters which are illustrated by but not limited to the following: bisphenol A polycarbonate, BCC polycarbonate, BPZ polycarbonate, copolycarbonates of BPA and BPI, BPA-dodecanedioic acid copolyestercarbonate, and polyethylene terephthalate.
The substantially single phase silicone copolycarbonates of the present invention may optionally be blended with any conventional additives used in various applications such as the preparation of optical articles. Said conventional additives include but are not limited to UV absorbers, antioxidants, heat stabilizers, anti static agents and mold release agents, slip agents, antiblocking agents, lubricants, anticlouding agents, coloring agents, natural oils, synthetic oils, waxes, organic fillers and mixtures thereof.
In particular, it is preferable to form a blend of the substantially single phase silicone copolycarbonate and additives which aid in processing the blend to form the desired molded article such as an optical article. The blend may optionally comprise from about 0.0001 to about 10% by weight of the desired additives, more preferably from about 0.0001 to about 1.0% by weight of the desired additives.
Examples of the aforementioned heat stabilizers, include, but are not limited to, phenol stabilizers, organic thioether stabilizers, organic phosphite stabilizers, hindered amine stabilizers, epoxy stabilizers and mixtures thereof. The heat stabilizer may be added in the form of a solid or liquid.
Examples of UV absorbers include, but are not limited to, salicylic acid UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, cyanoacrylate UV absorbers and mixtures thereof.
Examples of the mold release agents include, but are not limited to natural and synthetic paraffins, polyethylene waxes, fluorocarbons, and other hydrocarbon mold release agents; stearic acid, hydroxystearic acid, and other higher fatty acids, hydroxy fatty acids, and other fatty acid mold release agents; stearic acid amide, ethylenebisstearamide, and other fatty acid amides, alkylenebisfatty acid amides, and other fatty acid amide mold release agents; stearyl alcohol, cetyl alcohol, and other aliphatic alcohols, polyhydric alcohols, polyglycols, polyglycerols and other alcoholic mold release agents; butyl stearate, pentaerythritol tetrastearate, and other lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, polyglycol esters of fatty acids, and other fatty acid ester mold release agents; silicone oil and other silicone mold release agents, and mixtures of any of the aforementioned.
The coloring agent may be either pigments or dyes. Organic coloring agents may be used separately or in combination in the invention.
The desired optical article may be obtained by molding the substantially single phase copolycarbonate or alternatively molding a blend of the substantially single phase copolycarbonate with a polycarbonate, a copolycarbonate, a copolyestercarbonate or a polyester by injection molding, compression molding, extrusion methods and solution casting methods. Injection molding is the more preferred method of forming the article.

Substantially single phase silicone copolycarbonates, methods, and optical articles made therefrom


A method for splitting carbon dioxide via a two-step metal oxide thermochemical cycle by heating a metal oxide compound selected from an iron oxide material of the general formula AxFe3-xO4, where 0≦x≦1 and A is a metal selected from Mg, Cu, Zn, Ni, Co, and Mn, or a ceria oxide compound of the general formula MaCebOc, where 0<a<1, 0<b<1, and 0<c<2, where M is a metal selected from the group consisting of at least one of a rare earth metal and an alkaline earth metal, to a temperature greater than approximately 1400° C., thereby producing a first solid-gas mixture, adding carbon dioxide, and heating to a temperature less than approximately 1400 C, thereby producing carbon monoxide gas and the original metal oxide compound.

The present invention relates generally to a method of splitting of carbon dioxide using a thermochemical cycle and, more particularly, to a method of splitting carbon dioxide using ferrite and ceria compositions in the thermochemical cycle.
CO is one fundamental component, the other being H2, of syngas, the key intermediate for synfuel production. Reactions of syngas to form hydrocarbons are thermodynamically downhill. Hydrogen can be produced renewably with commercially available technologies, for example via photovoltaic (PV)-driven electrolysis. A reasonable starting estimate for the solar-to-hydrogen efficiency is about 9% (0.12(PV)×0.75(electrolysis)=0.09). Hydrogen can then be reacted with CO2 to directly produce methanol, or indirectly to produce CO and then methanol, for example. Many of the important reactions of CO2 and H2 are not thermodynamically favorable (defined here as having a negative Gibbs free energy of reaction). (For example, the reverse water gas shift reaction is favorable only at very high temperatures and the direct synthesis of methanol is favorable only at temperatures lower than those required to carry out the conversion.) Nonetheless, it has been calculated that current technology would allow hydrocarbons to be manufactured from CO2 and electrolytic H2 with an electrical to hydrocarbon efficiency of roughly 40-50%. Thus a 5% sunlight-to-fuel efficiency is plausible for a PV-driven fuel production process.
Thermochemical cycles for water splitting are under development and avoid the efficiency-sapping sunlight to electrical energy conversion require for electrolysis and may somewhat improve the overall efficiency of both hydrogen and subsequent hydrocarbon production. Additionally, at high temperatures, CO2 is thermodynamically less stable than H2O. Thus, thermochemically splitting CO2 in a process analogous to water splitting is thermodynamically feasible and also provides a direct route to manufacture CO for syngas and hydrocarbon production.
Cycles for splitting CO2 (or H2O) are endothermic and generally require at least one high temperature step to drive the reaction. Concentrating solar power (CSP) and can efficiently supply heat in excess of 800° C. and is potentially suited to operation of thermochemical cycles. Thermochemical cycles are typically categorized by temperature range. High temperature (HT) cycles are those that operate within the limits of most engineering materials and typically involve temperatures between 600 and 1000° C. Ultra-high temperature (UHT) cycles require heat input at temperatures in excess of 1000 and up to 3000° C. Only CSP can be applied to these cycles as materials constraints preclude NE above about 900° C.
Thermochemical cycles have conventionally been studied as potentially a more straightforward, efficient, and lower cost approach to hydrogen production than using electric power to electrolyze water. In the water splitting (WS) scenario, thermochemical cycles employ reactive materials or fluids in a series of chemical reactions that sum to the overall water splitting reactionH2O→H2+½O2
One class of thermochemical cycles utilizes metal oxides as the internally recycled working material. Fe3O4 is the prototypical working material for these cycles. The overall idealized reaction scheme is:Fe3O4→3FeO+½O2 3FeO+H2O→Fe3O4+H2
In practice, the temperature required to thermally reduce Fe3O4 to any significant extent is in excess of the melting point of both the oxide reactant and product, while the temperature of the hydrogen producing step is below the melting points. This inherent phase change renders the process unworkable as written. One strategy that has been developed to overcome this problem is to substitute other (A) metals into the Fe3O4 framework that have the effect of lowering the reduction temperature while maintaining the overall spinel structure.
Useful would be a method of splitting CO2 using a similar thermochemical conversion cycle reaction and metal oxides that can be suitable used at operating conditions that favor CO2 splitting.


A laser marking device that irradiates a laser beam on a workpiece (W) to transform a portion inside the workpiece at a focal point of the laser beam, thus putting a dot in each predetermined area. The laser marking device includes acquiring mechanism (10, 20) that acquires, as information on the dot, at least two-dimensional position information of an exposed section of the workpiece (W), and density information of the dot, coordinate setting mechanism (30) that calculates, for each dot according to the density information, dot depth information showing the distance from the surface of the workpiece (W) to the dot in the thickness direction of the workpiece (W), and sets three-dimensional coordinates for each dot based on a position specified by the dot depth information and the two-dimensional position information, and laser marking mechanism (40) that performs marking with the three-dimensional coordinates as a laser beam focal point.

There has been known a conventional technology which uses a marking device to mark two-dimensional codes, characters, logo marks, images, and the like on a transparent polycarbonate material.
The polycarbonate is a transparent material in a pure state, and is generally excellent in shock resistance, weather resistance, electrical insulation, dimensional stability, and the like.
A conventional method to mark characters and the like on the polycarbonate often employs inkjet printing.
However, the conventional printing by means of the inkjet directly attach ink to a surface of the transparent polycarbonate, and there pose such problems that the applied ink is separated by a contact, is subject to a secular change, and is inferior in durability.
In order to solve these problems, there has been developed a technology which performs marking by means of a laser beam on the polycarbonate material (refer to Japanese Laid-Open Patent Publication (Kokai) No. H5-337659, line 7 of second column to line 10 of third column, for example: Document 1).
The patent document 1 describes laser marking on the polycarbonate material in the following way.
Namely, there is described a method and a marking device, which perform marking by irradiating a repetitively pulsed YAG laser beam on a workpiece made of a polycarbonate material, thereby transforming the color of a component material at the irradiated position to black.
However, according to the conventional laser marking method for the polycarbonate, even if the marked portion has changed the color thereof to brown to black, marked images, characters, and the like have high light transmittance, and thus have a defect of inferior visibility, and there poses such a problem that the sole polycarbonate can hardly be applied to products such as cards.
Moreover, since the visibility of the marked images and characters is low, it is difficult to mark an image such as a photograph which requires a fine adjustment of density changes on the polycarbonate.
It is an object of the present invention to solve the above problems by providing a laser marking device and a laser marking method which, upon marking an image or the like read by a scanner or the like on the polycarbonate, mark the image which bares comparison with the original image by adjusting the dot depth and the dot diameter.
Moreover, it is another object of the present invention to provide a laser marking device and a laser marking method which build up a polycarbonate material and a resin material, and perform marking such that two-dimensional codes, characters, logo marks, images, and the like appear clearly and hovering three-dimensionally.

Laser marking device, laser marking method, and object to be marked


A multioscillator ring laser gyro having a Faraday Cell with an optical wedge in one of its branches. Variations in the MCDL of the optical wedge with temperature are reduced to substantially zero. The internally specularly reflected and backscattered beams from said primary beam have path lengths such that the internally double-bounced reflected and scattered beams of each mode have path lengths wherein the differences between the mode directions are adjusted in a particular manner to reduce cyclic variations with temperature in MCDL substantially to zero.

1. Field of the Invention
This invention pertains to multioscillator ring laser gyros and particularly to an optical wedge used in a Faraday Cell therein.
2. Description of Related Art
The optical wedge is used in Faraday Cells in multioscillators. Preferably the path of the multioscillator is a rectangle, usually substantially square, that is folded about a diagonal into two planes. It should be noted, however, that some multioscillators have other than four path legs and mirrors and may be planar, and the invention using the corrected optical wedge described and claimed herein contemplates its use in such other ring lasers.
In this application, a "mode" is defined as a primary beam of a multioscillator ring laser gyro, plus two reflected double bounce beams produced inside an optical wedge by such primary beam. Thus, each multioscillator ring laser has four modes. Energizing the ring laser creates four primary beams, and they are resonant within the laser cavity. The two double-bounce beams of each of the modes are reflected and scattered beams within an optical wedge of a Faraday Cell, and they have very little energy compared to the energy in the primary beam because most of the beam is transmitted at the wedge-to-gas interface. The double-bounce beams create significant errors when the multioscillator is used to sense angular position, despite their low energy content.
The four primary beams of a multioscillator ring laser gyro may be slightly elliptically polarized, but with that understanding of their exact nature, for convenience let them be be described as circularly polarized. Polarize two of the primary beams with one polarity direction, and the other two beams with the other polarity direction. At each corner mirror of the ring laser, the polarity direction of each primary beam reverses, but since all beams reverse polarity it produces no confusion to ignore the polarity reversal.
Two of the primary beams traverse the ring laser in one direction, and the other two primary beams traverse the ring laser in the other direction. Arbitrarily designate the directions clockwise and counterclockwise. The primary beam combinations are arranged such that for each polarization polarity there is both a clockwise and an anticlockwise beam.
As a result of a nonplanar geometry and/or optical components such as a Faraday wedge, the beams are further displaced in frequency, one from another. The ring laser gain medium is capable of sustaining oscillations over a band of frequencies, and the four frequencies are within that band. The oscillations are produced by various means (not shown). For example, the oscillations may be produced by an electric d.c. gradient between a cathode and anode through part of the laser path; or the oscillations may be produced by an electromagnetic radio frequency field acting on a gas such as a neon gas mixture within a portion of the ring laser path. Designate the excitation region of the path the "gain bore".
In a multioscillator there operate two gyros. Two of the oppositely propagating beams produce signals for one gyro, and the other two oppositely propagating beams produce signals for the other gyro.
Because the two frequencies of each gyro do not coincide in the presence of zero angular velocity about the sensing axis of the gyro, each gyro is frequency biased. As the measured angular velocity increases, the two frequencies of one of the gyros diverge, and the two frequencies of the other of the gyros converge. The differences in sense of polarization allow the two gyro signals to be identified and converted into electrical signals which are measures of sensed angular velocity.
The output signal of a ring laser gyro is a heterodyne signal between the optical frequencies of the two beams comprising that gyro. The bias frequency is subtracted out, and the difference is proportional to the measured angular velocity. The use of a multioscillator avoids certain problems such as frequency locking of the two frequencies of the primary beams of a gyro when their difference frequency is small.
Designate the four beams herein, from lowest frequency to highest frequency, left circularly polarized anticlockwise, "La," left circularly polarized clockwise, "Lc," right circularly polarized clockwise, "Rc," and right circularly polarized anticlockwise, "Ra" beams.
There are means for extracting the beams and beating them against each other to produce signals which are a measure of angular velocity. For example, a portion of the two beams may be extracted and the extracted beam or beams folded and superimposed to produce fringes which are readily countable as they move across an optical field. It is most convenient to use the Lc, Ra beams for one gyro and the La, Rc beams for the other gyro.
There are three types of differential losses among the four lasing modes of a multioscillator ring laser gyro. When the left-circularly polarized modes (La, Lc) suffer different round-trip cavity loss from the right-circularly polarized modes (Ra, Rc) the differential loss is called, "differential polarization loss" (DPL).
When the clockwise modes (Lc, Rc) suffer different round-trip cavity loss from the anticlockwise modes (La, Ra) the differential loss is called, "differential directional loss" (DDL).
When the modes of one helicity (La,Rc) suffer different round-trip cavity loss than the modes of the other helicity (Lc,Ra) the differential loss is called, "magnetic circular dichroic loss" (MCDL).
Of the three types of loss, the multioscillator frequency bias is most sensitive, perhaps by a factor of a thousand, to MCDL. The operation of the invention could be used to reduce DDL and DPL, but for the best performance improvement in the multioscillator gyro, it is used to reduce MCDL.
Change in MCDL with temperature variation causes unwanted change in the multioscillator ring laser gyro frequency biases. Some of the frequency bias changes are such that their amplitudes vary monotonically with temperature, but others cycle, varying first upward or downward with changed temperature, then changing direction as the temperature further changes.
One possible way of removing all the differential loss effects (DPL, DDL and MCDL) caused by the double-bounce beams in the wedge would be to arrange the first and second double-bounce beams always to be anti-phased so their phasor sum is zero. In practice this is not likely because the scatter and reflection amplitudes from the two Faraday wedge faces are not equal, and because selection of the differential phase shifts between the two wedge faces, for scattering and reflection, likely cannot be guaranteed. Faraday-wedge fabrication techniques are believed not available to achieve the required accuracy.

Multioscillator ring laser gyro using compensated optical wedge

Litton Systems Inc., Guidance & Control Division, Mail Stop, 5500 Canoga Ave.


A PLL including a phase comparator, a VCO, and a charge pump further includes a reset circuit. The reset circuit detects whether both of the charge pump transistors are in an ON state, and if so, generates a reset signal which inhibits the UP and DOWN signals generated by the phase comparator. The reset circuit includes first and second detection circuits and a signal generating circuit.

1. Field of the Invention
The present invention relates generally to Phase-Locked Loop (PLL) frequency synthesizers, and more particularly, to PLL frequency synthesizers which operate to decrease the difference between the ideal and the realized output energy of a PLL frequency synthesizer's charge pump circuit, and a method of performing the same.
2. Description of the Related Art
PLL frequency synthesizers are frequently used in mobile communication devices such as portable telephones, cordless telephones, and a variety of other well known applications. A PLL frequency synthesizer generates a comparison signal by frequency-dividing a frequency signal output from a voltage controlled oscillator. Based on the difference between the phase of the comparison signal and the phase of a reference signal, a charge pump circuit outputs a voltage signal. The voltage controlled oscillator outputs a controlled frequency signal in accordance with the voltage signal. The controlled frequency signal from the voltage controlled oscillator is then frequency-divided again, yielding another comparison signal. The PLL frequency synthesizer repeatedly executes this operation to output a frequency signal whose level is locked to some multiplication of the level of the reference signal.
An ideal PLL frequency synthesizer operates such that the output energy of the charge pump circuit is a truly linear function (i.e., linear with no offset) of the phase difference between the reference signal and the output signal. FIG. 8A is a graph of a curve 300 of the ideal PLL frequency synthesizer. The curve 300 plots the output energy along the vertical axis as a function of the phase difference plotted along the horizontal axis.
However, due to delay actually occurring in the charge pump circuit, the realized PLL frequency synthesizer only responds to an absolute phase difference greater than some small, but substantial, amount. As a result, the charge pump circuit has a deadband wherein the output energy is substantially zero regardless of the phase difference, as shown by a curve 305 in FIG. 8B. To prevent the occurrence of such a deadband, the charge pump circuit is generally designed in such a manner that the output energy overlaps near the origin and the phase difference characteristic, although non-linear, no longer has a deadband, as indicated by a two-dot chain line 310 in FIG. 8C.
FIG. 17 shows a conventional PLL frequency synthesizer 200. A reference frequency divider 201 frequency-divides a crystal oscillation signal having a predetermined frequency output from a crystal oscillator (not illustrated) to yield a reference signal fr and outputs the reference signal fr to a phase comparator 203. A comparison frequency divider 202 frequency-divides a frequency signal fv output from a voltage controlled oscillator (VCO) 206 to yield a comparison signal fp and outputs the comparison signal fp to the phase comparator 203.
The phase comparator 203 compares the phase of the reference signal fr with that of the comparison signal fp, and, in response, outputs a first phase difference signal .phi.R and a second phase difference signal .phi.P to a charge pump circuit 204.
As shown in FIG. 18, the charge pump circuit 204 has a pMOS transistor 210 and an nMOS transistor 211 connected in series between a power supply V.sub.CC and a ground GND. The drains of the pMOS transistor 210 and the nMOS transistor 211 are connected to an output terminal 212 of the charge pump circuit 204. Low-Pass Filter (LPF) 205, as shown in FIG. 17, is connected to the output terminal 212.
The first phase difference signal .phi.R is input to the gate of the pMOS transistor 210, and the second phase difference signal .phi.P is input to the gate of the nMOS transistor 211. Based on the voltage potentials of the first and second phase difference signals .phi.R and .phi.P, the pMOS transistor 210 and the nMOS transistor 211 are turned either on or off. Hence, the charge pump circuit 204 outputs an analog voltage signal Do from the output terminal 212 based on the first and second phase difference signals .phi.R and .phi.P.
The LPF 205 smoothes the voltage signal Do from the charge pump circuit 204 to yield a control voltage signal V.sub.T having a high frequency component removed therefrom, and outputs this signal V.sub.T to the VCO 206. The VCO 206 outputs the frequency signal fv according to the voltage of the control voltage signal V.sub.T. This frequency signal fv is fed back to the comparison frequency divider 202. As this operation is repeatedly and continuously executed, the conventional PLL frequency synthesizer 200 will, theoretically, reach a steady-state where the frequency signal fv of the VCO 206 is locked to a set frequency.
As shown in FIG. 18, the phase comparator 203 has six 2-input NAND gates 221 to 223 and 231 to 233, two 3-input NAND gates 224 and 234, a single 4-input NAND gate 237, three inverters 225, 226 and 235 and a delay circuit 238.
The NAND gate 221 receives the reference signal fr and the output signal, S24, of the NAND gate 224. The NAND gate 221 outputs a signal S21 based on both signals fr and S24. The NAND gate 223 receives the output signal, S22, of the NAND gate 222 as well as the signal S21. The NAND gate 223 outputs a signal S23 based on both signals S21 and S22.
The NAND gate 224 receives the output signal, S38, of the delay circuit 238 as well as the signals S21 and S23. The NAND gate 224 outputs a signal S24 based on the three signals S21, S23 and S38. The inverters 225 and 226 are connected in series to the output terminal of the NAND gate 224, and the inverter 226 outputs the first phase difference signal .phi.R which is in phase with the signal S24.
The NAND gate 222 receives the two signals S23 and S38 and outputs a signal S22 based on both signals S23 and S38. The NAND gate 231 receives the output signal, S34, of the NAND gate 234 as well as the comparison signal fp. The NAND gate 231 outputs a signal S31 based on both signals fp and S34. The NAND gate 233 receives the output signal, S32, of the NAND gate 232 as well as the signal S31. The NAND gate 233 outputs a signal S33 based on both signals S31 and S32.
The NAND gate 234 receives the three signals S31, S33 and S38, and outputs a signal S34 based on those three signals. The inverter 235, which is connected to the output terminal of the NAND gate 234, inverts the signal S34 to output the second phase difference signal .phi.P.
The NAND gate 232 receives the two signals S33 and S38, and outputs a signal S32 based on those two signals. The NAND gate 237 receives the four signals S21, S23, S31 and S33, and outputs a signal S37 based on those signals to the delay circuit 238. The delay circuit 238, which comprises even-numbered inverters connected in series, delays the signal S37 and outputs the signal S38 which in phase with the delayed signal S37.
In the thus constituted phase comparator 203, when the reference signal fr goes low, the signal S21 goes high, based on which the signal S24 goes low, causing the first phase difference signal .phi.R to go low, as shown in FIG. 19. Further, when the reference signal fr goes low, the signal S31 goes high. As a result, after the delay time of the NAND gate 234, the signal S34 goes low and the second phase difference signal .phi.P goes high.
When the signals S21 and S31 go high, the signal S37 goes low. Consequently, the signal S38 goes low after a delay time D1 of the delay circuit 238. The transition of the signal S38 to the low level causes both the signals S24 and S34 to go high. As a result, the first phase difference signal .phi.R goes high and the second phase difference signal .phi.P goes low.
In accordance with the phase difference between the reference signal fr and the comparison signal fp and the delay time D1 of the delay circuit 238, the phase comparator 203 outputs the first and second phase difference signals .phi.R and .phi.P. When the two phase difference signals .phi.R and .phi.P are output as overlapped, the output energy of the charge pump circuit 204 has an overlap non-linear area as indicated by the two-dot chain line 310 in FIG. 8C. Because this overlap non-linear area occurs, the desired ideal phase characteristics of the ideal PLL frequency synthesizer cannot be obtained.
Further, it is difficult to mass-produce semiconductor chips equipped with the aforementioned various elements such that they have uniform quality. Therefore, the delay time D1 of the delay circuit 238 varies from semiconductor chip to semiconductor chip even within a single production run. Still further, when the delay time D1 becomes longer to increase the overlap range, the output waveform of the charge pump circuit becomes larger, thus generating spurious noise.


The present invention provides a manufacturing method of a semiconductor module which enables the joining at a low temperature within a short time and can obtain more reliable joining portions by performing the joining without using a solder joining medium. The manufacturing method of a semiconductor module includes a first joining step for joining first circuit electrodes which are formed on a circuit board and back-surface-side die electrodes of a semiconductor die, a second joining step for joining the front-surface-side electrodes of the semiconductor die and one ends of lead frames, and a third joining step for joining another ends of the lead frame and second circuit electrodes which are formed on the circuit board, wherein a low-melting-temperature metal layer is formed on one conductive portion of a pair of conductive portions to be joined and, thereafter, the low-melting-temperature metal layer is heated and pressurized thus diffusing the low-melting-temperature metal layer into the pair of conductive portions by solid-liquid diffusion whereby the conductive portions are joined to each other.

A power conductor is a large-capacity semiconductor which exhibits a voltage or a current larger than a voltage or a current used in a semiconductor for a personal computer or the like and has been popularly used in an electric power field, rail roads, automobiles, household electric appliances and the like,
Among modules which use such a power semiconductor, in a module-of a power transistor semiconductor of a general-purpose inverter having a capacitance of 0.1 kW to 5.5 kW which is used as a control device for various motors, power transformers or the like, a lead frame made of copper alloy has been conventionally used to decrease an electric resistance value of wiring and, at the same time, to obtain the excellent thermal characteristics.
FIG. 4 shows one example of the conventional structure of the semiconductor module which uses a semiconductor chip which constitutes one of power semiconductors and is referred to as an insulation gate type bipolar transistor (IGBT).
The semiconductor module is mainly constituted of a heat radiation plate 83 which is joined to a substrate 80, a semiconductor chip 90 which is joined to the heat radiation plate 83, and a lead frame 95 which has one end thereof joined to the semiconductor chip 90.
Electrodes are formed on both front and back surfaces of the semiconductor chip 90, wherein the collector electrode 91 is formed on the back surface of the semiconductor chip 90 and an emitter electrode 92 is formed on the front surface of the semiconductor chip 90. Further, the heat radiation plate 83 is joined to the collector electrode 91 on the back surface of the semiconductor chip 90 using a high-temperature solder layer 71. Still further, a lower surface of the heat radiation plate 83 is joined to a collector-side electrode 81 formed on the printed wiring board 80 using a low-temperature solder layer 72.
On the other hand, to an emitter electrode 92 formed on the surface of the semiconductor chip 90, one end of the lead frame 95 is joined using a high-temperature solder layer 73. Further, another end of the lead frame 95 is joined to a lead frame electrode 82 formed on the printed wiring board 80 using a low-temperature solder layer 74.
The manufacturing method of this power semiconductor module is as follows. First of all, in a non-oxidizing atmosphere using a carbon jig, the heat radiation plate 83, the semiconductor chip 90 and one end of the lead frame 95 are integrally formed by a joining step using the high-temperature solder layers 71, 73.
Next, in a reflow step which uses cream solder, the lower surface of the heat radiation plate 83 and another end of the lead frame 95 are respectively joined to the collector-side electrode 81 and the lead frame electrode 82 which are formed on the printed wiring board 80 by the low-temperature solder layers 72, 74 whereby a power semiconductor module having the structure shown in FIG. 4 is manufactured.
Here, as a conventional structural example of the semiconductor module which uses the semiconductor chip of insulation gate type bipolar transistor (IGBT) but differs from the semiconductor module shown in FIG. 4, the constitution shown in FIG. 5 is also known.
The semiconductor module shown in FIG. 5 mainly includes a circuit board 280 which is joined to a heat radiation plate 283 and is formed of a DBC substrate, a semiconductor die 290 which is joined to the circuit board 280 and is formed of a semiconductor chip, and a bonding wire 295 which has one end thereof joined to the semiconductor die 290.
Electrodes are formed on both front and back surfaces of the semiconductor die 290, wherein a back-surface die electrode 291 which constitutes a collector electrode is formed on the back surface of the semiconductor die 290 and a front-surface die electrode 292 which constitutes an emitter electrode is formed on a surface of the semiconductor die 290. Further, the heat radiation plate 283 is made of a metal material such as Cu or the like, while the circuit board 280 which is formed of the DBC substrate is constituted by forming electrodes 280 B, 280 C and 280 D formed of a conductive layer made of Cu or the like on both surfaces of a ceramic substrate 280A.
To the back surface die electrode 291 of the semiconductor die 290, a first circuit electrode 280 B which constitutes a collector conductive layer on an upper surface of the circuit board 280 is joined by means of a joining portion 271, and a third circuit electrode 280 D which constitutes a heat-radiation-plate conductive layer formed on a lower surface of the circuit board 280 is joined to the heat radiation plate 283 by means of a joining portion 272.
On the other hand, a front-surface die electrode 292 of the semiconductor die 290 and a second circuit board 280 C which constitutes a lead-frame conductive layer formed on an upper surface of the circuit board 280 are joined by a bonding wire 295.
Then, the above-mentioned joining portions 271, 272 constitute joining portions formed by solder joining.
Further, with respect to a technique relevant to the formation of the above-mentioned solder layer, a method which forms solder bumps made of alloy by a vapor deposition method has been known. For example, as a method for forming lead-free solder bumps due to the formation of a multilayered film, JP-A-2002-43348 discloses a technique in which an Sn film and an M film whose film thicknesses are set to obtain the composition of Sn1−XMX (M: containing at least one of Au, In and x being set to satisfy the relationship of 0<x<0.5) are alternately vapor-deposited to form a multilayered film and, thereafter, a mask is removed to form a solder bump precursor which is formed of the above-mentioned multilayered film, subsequently, annealing is applied to the solder bump precursor to make the composition of the solder bump precursor uniform and, further, the solder bump precursor is subject to the reflow at an eutectic temperature of the precursor thus forming the solder bumps.
Further, JP-A-5-9713 discloses an alloy vapor deposition method in which base alloy whose composition and quantity are adjusted to obtain an alloy film of desired composition and desired thickness is preliminarily prepared in a crucible for vapor deposition, and the base alloy is completely evaporated to form a targeted alloy film on a substrate and, at the same time, the base alloy composition for vapor-depositing alloy having the targeted composition is preliminarily obtained thus obtaining a vapor deposited film of alloy having the arbitrary composition.
In the above-mentioned manufacturing method of a power semiconductor module using the solder which constitutes the prior art, as explained in conjunction with the example shown in FIG. 4, for example, the manufacturing method includes steps which perform heating twice, that is, the joining step which uses the high-temperature solder and the step which performs solder joining using the cream solder having a melting point lower than a melting poring of the high-temperature solder. Here, particularly in the joining step which uses the high-temperature solder, a high temperature of approximately 300° C. is required and hence, there arises a drawback that the semiconductor die is liable to be easily damaged by heat generated at the time of joining. Further, there also exists a drawback that the steps become complicated since two kinds of solders, that is, the high-temperature solder and the low-temperature solder are used.
Further, the power semiconductor module allows a large current to pass therethrough and hence, the power semiconductor module generates heat remarkably whereby a thermal stress arises due to the difference in thermal expansion rate among respective constitutional materials. For example, in the conventional solder joining used in the examples shown in FIG. 4 and FIG. 5, there has been a drawback that a joining interface is broken by this thermal stress.
Still further, the reliability of the joining portion such as the strength, fatigue lifetime depends on the property of a material which is interposed between parts to be joined and a solder material has a drawback with respect to the high-temperature property and the thermal fatigue lifetime. Particularly, with respect to a die such as the power semiconductor module to which a large current is applied, there exists a possibility of the lowering of the insulating property of the power semiconductor module attributed to an organic material and hence, it is impossible to use a flux which serves to remove surface oxide of a joining material thus joining the parts. Accordingly, in the conventional solder joining, there has been a drawback that a defect of several 100 μm level may occur in the joining portion attributed to contamination or oxide during a joining step.
Further, in the method for forming the lead-free solder bumps disclosed in JP-A-2002-43348, the joining at a low temperature for a short time is insufficient. For example, the joining at a low temperature of 200° C. or less and for a short time is difficult.
Further, in the alloy vapor deposition method of the JP-A-5-9713, it is necessary to obtain the relationship between the composition of the base alloy in the crucible and the alloy composition in the vapor-deposited film and, it is necessary to determine the composition of the base alloy based on a correction curve thus giving rise to a drawback that the preparation steps up to the vapor deposition becomes cumbersome.
The present invention has been made in view of these drawbacks and it is an object of the present invention to provide a manufacturing method of a semiconductor module which enables the joining of an electrode of a semiconductor die, an electrode on a circuit board, a connecting member such as a lead frame and, further, a heat radiating member at a low temperature within a short time, and can obtain a highly reliable joining portion by performing the joining without using a solder joining medium.

Manufacturing method of semiconductor module including solid-liquid diffusion joining steps


The laser reference tool of the invention consists of a base that can be releasably mounted to a surface. A housing is mounted on the base such that it can be repositioned relative to the base in a direction parallel to the surface. A turret carrying the laser module is rotatable about first and second orthogonal axes. The laser module is also rotatable relative to the turret about a third axis orthogonal to the first and second axes.

The invention relates generally to a laser reference device and more particularly to a laser reference tool that may be wall mounted and that can be accurately aligned to user selectable orientations.
Traditional reference tools, such as levels, consist of one or more level vials mounted in a level body. The level body has one or more leveling faces that are calibrated with reference to the level vials such that one of the leveling faces can be placed against a surface and level readings made from the level vials. Laser level devices consist of a body supporting a laser generating device and a lens for focusing the laser. The lens can focus the laser into a beam of light that is projected as a dot on a surface or a plane of light that is projected as a line on a surface. The light pattern projected on the surface may be used as a reference point for locating and orienting articles.
Devices exist to project a plane of light onto a vertical surface such as a wall. One type of device sits on a horizontal surface and is oriented relative to vertical. Other laser reference devices may be mounted directly to the vertical surface to project light on that surface and/or on other surfaces. In order to orient the device on the vertical surface at least one level vial is mounted on the device to provide the user with a visual indication of the orientation of the device relative to true plumb or true level to control the projection of the light onto the surface. Because the device is manually oriented and the device relies on the ability of the user to orient the device by visually inspecting the level vial while simultaneously mounting the entire device on the surface, these devices can be difficult to orient to true plumb and/or level. Errors may be introduced as a result. Moreover, because the surface on which the device is supported may not be perfectly level or plumb, leveling the laser module in only one plane may not properly orient the device with respect to true level or true plumb.
Other devices that attach directly to a vertical surface use a pendulum device to orient the device to true level. Typically, the use of the pendulum type arrangement only allows the device to be properly oriented to one position. A pendulum based device is also known that is intended to allow the device to be oriented to multiple positions. The positions are predefined and limited, however, thus limiting the flexibility of the device. Moreover, the use of a pendulum to orient the device in multiple positions has not proved to be sufficiently accurate.
Thus, an improved laser reference device that can be fixed to a vertical surface and accurately oriented to a wide variety of positions is desired.


The image forming apparatus preferably includes a process unit, an acquisition unit, a detection unit, and a selection unit. The process unit executes processes in a plurality of modes corresponding to identification information for identifying a user. The acquisition unit acquires identification information for identifying a user. The detection unit detects presence or absence of an object to be used in at least any one of the plurality of modes. The selection unit selects a mode corresponding to the presence or absence of the object detected by the detection unit from the plurality of modes corresponding to the identification information acquired by the acquisition unit.

The present invention relates to an image forming apparatus which has a plurality of functions such as a scanner function and a photocopy function.
An image forming apparatus known in the art has a plurality of functions such as a scanner function, a photocopy function (printer function), and a facsimile function. The scanner function is used for reading image information recorded on a manuscript. The photocopy function is used for printing image information on a sheet or other printing media. The facsimile function is used for transmitting and receiving image information through a telephone line. This image forming apparatus has a plurality of modes of processes executed by using at least one of these functions. This image forming apparatus is adjusted to obtain information for identifying a user (i.e., an ID of the user) from an RFID chip for execution of processes in the modes.
This image forming apparatus has a mode selection key, an ID acquisition key, and a start key. The mode selection key is pushed to select modes. The ID acquisition key is pushed to obtain an ID from the RFID chip. The start key is pushed to execute processing in each mode. The image forming apparatus stores various settings associated with an ID. The settings includes a FAX setting such as destinations of transmission, a manuscript reading setting, and a sheet printing setting.
When the process in the mode corresponding to the facsimile function of the image forming apparatus (hereinafter abbreviated as facsimile mode) is executed, for example, the facsimile mode is initially selected from the plural modes by operating the mode selection key. Then, an ID is obtained from the RFID chip by operating the ID acquisition key to access the FAX setting. The process in the facsimile mode is thus executed according to the FAX setting by operating the start key.


An optical head including a first dielectric layer having a first refractive index, a pair of second dielectric layers located adjacent to the first dielectric layer on both sides thereof, each of the second dielectric layers having a second refractive index larger than the first refractive index, a pair of third dielectric layers located adjacent to the second dielectric layers, and a pair of fourth dielectric layers located adjacent to the third dielectric layers, each of the fourth dielectric layers having a third refractive index larger than the first refractive index. Light is incident on the optical head in a direction orthogonal to a layering direction of the first to fourth dielectric layers. The first dielectric layer and each of the third dielectric layers have different refractive indices or different thicknesses.

1. Field of the Invention
The present invention relates to an optical head and an information storage device using the optical head.
2. Description of the Related Art
With the evolution of information society, the amount of information is increasing more and more. In response to such an increasing amount of information, it is desired to develop an information recording method capable of recording information at a very high recording density and a recording/reproducing device based on this information recording method. In an optical disk drive as one kind of information recording/reproducing device, a focused beam diameter related to a recording capacity is limited by the wavelength of light. As measures for increasing the recording density in the optical disk drive, shortening of the wavelength of laser to be used and increasing of the numerical aperture (NA) of an optical lens are known. However, there is a limit to high-density recording due to the diffraction limit. As means for increasing the numerical aperture of an optical lens, there has been proposed a method of using a solid immersion lens to increase the numerical aperture to not less than 1 and utilizing evanescent light leaked from the bottom surface of the solid immersion lens to record information on an optical disk medium. However, this method naturally has a limit to high-density recording because the NA is increased by the refractive index of the solid immersion lens.
As a recording method for realization of high-density recording, attention is focused on a near-field optical recording method such that a minute opening smaller than the wavelength of incident light is formed to utilize near-field light generated from this minute opening, thereby forming a beam spot smaller than the wavelength of the incident light. As a structure (near-field light probe) for generating the near-field light, a pointed optical fiber (optical fiber probe) having a minute opening smaller than the wavelength of light is widely used. Such an optical fiber probe is fabricated by drawing one end of an optical fiber with heat or using chemical etching to thereby point the one end of the optical fiber and next coating the pointed optical fiber except the tip thereof with metal. By introducing light into this optical fiber, near-field light can be generated near the minute opening formed at the tip of the pointed optical fiber. However, this optical fiber probe has a disadvantage such that the light use efficiency is low. For example, when the diameter of the minute opening is 100 nm, the ratio of the intensity of light emerging from the tip of the optical fiber to the intensity of incident light entering the optical fiber is 0.001% or less.
As means for improving the light use efficiency, the following probes have been proposed.
(1) Multistep Pointed Fiber Probe
This probe is an optical fiber probe such that the tapering angle of the tip of the optical fiber is stepwise changed from the root to the tip in two or three steps (Applied Physics Letters, Vol. 68, No. 19, p2612–2614, 1996; Applied Physics letters, Vol. 73, No. 15, p2090–2092, 1998).
(2) Metal Stylus Probe
The stylus of a scanning tunneling microscope (STM) is used as a probe. By irradiating the tip of the stylus with light, intense near-field light is generated near the tip of the stylus (Japanese Patent Laid-open No. Hei 6-137847).
(3) Minute Opening Fiber Probe with Microscopic Metal Ball
This fiber probe is a fiber probe such that a microscopic metal ball is formed at the center of the minute opening at the tip of an optical fiber. Plasmon is excited in the microscopic metal ball by means of light emerging from the minute opening, thereby generating intense near-field light near the metal ball (Japanese Patent Laid-open No. Hei 11-101809).
(4) Glass Piece Probe Coated with Metal
A metal film having a thickness of about 50 nm is formed on a glass piece cut into a triangular prism to excite surface plasmon on the metal film. The surface plasmon propagates toward the apex of the triangular prism to thereby generate intense near-field light near the apex (Physical Review B, Vol. 55, No. 12, p7977–7984, 1997).
(5) Glass Substrate Probe with Metal Scattering Member
This probe is a probe having a glass substrate and a metal scattering member attached to the bottom surface of the glass substrate. Intense near-field light is generated near the metal scattering member (Japanese Patent Laid-open No. Hei 11-250460).
In a near-field optical system, the spacing between a minute structure for generating near-field light and the surface of a sample must be set to several nanometers to tens of nanometers. Accordingly, in the case of using a probe configured by an optical fiber or a glass piece as mentioned above, a special control system is required to control the spacing between the tip of the probe and the sample surface. In general, the spacing is measured by using an interatomic force acting between the probe tip and the sample, and servo control is performed by using a measured value for the spacing. However, in the case of utilizing this servo control, a probe scanning speed is limited because there is a limit to a servo band. Particularly in an optical recording/reproducing device required to have a high data transfer rate, the probe must be scanned over an optical disk at a high speed, and high-frequency spacing variations due to warpage or inclination of the optical disk cannot be controlled by the above servo control method.
To solve this problem, the following probes have been proposed.
(1) Planar opening probe
This probe has a minute opening formed in a silicon substrate by anisotropic etching. Since a peripheral portion about the minute opening is flat, the spacing can be kept constant by pressing the probe on the sample (The Pacific Rim Conference on Lasers and Electro-Optics, WL2, 199).
(2) Opening probe with pad
A quadrangular pyramidal projection having a minute opening at the tip is formed on the bottom surface of a glass substrate, and a pad is formed around the projection. The spacing between the probe tip and the sample can be kept constant by the pad (Japanese Patent Laid-open No. Hei 11-265520).
(3) Surface emitting laser probe with metal minute projection
A metal minute opening and a metal minute projection are formed on the light emitting end surface of a surface emitting laser. Since the minute structure is flat, the spacing can be kept constant by pressing the probe on the sample (Applied Physics, Vol. 68, No. 12, p1380–1383, 1999). It is expected that the light use efficiency can also be improved because of the metal minute projection and the resonance structure.
(4) A patch antenna and a coaxial cable are applied to light, thereby generating near-field light with a high efficiency (Optics Communications Vol. 69, No. 3, 4, p219–224, 1989).
(5) A bow-tie metal piece is used as a minute dipole antenna to thereby generate minute near-field light with a high efficiency (U.S. Pat. No. 5,696,372).
As the performance of an optical memory using near-field light, the following three points are required.    (a) The spacing between the minute structure and the recording medium is controlled precisely on the order much smaller than the wavelength of light.    (b) The beam spot is minute.    (c) The light use efficiency is high, that is, high-speed data transfer is allowed.
The fiber probe having a pointed end whose tapering angle is multi-stepwise changed has a high efficiency 10 to 100 times that of a general fiber probe. However, the efficiency of this fiber probe is yet insufficient in the case of application to an optical recording/reproducing device required to have a light use efficiency of 0.5% or more. Further, since an optical fiber is used, the fiber probe is mechanically brittle and high-speed scanning is therefore impossible. All of the metal stylus probe, the minute opening fiber probe with microscopic metal ball, the glass piece probe coated with metal, and the glass substrate probe with metal scattering member utilize the characteristics of metal to improve the efficiency, and a high light use efficiency can be expected. However, the probe tip in each probe is mechanically brittle in shape, so that each probe is not fit for high-speed scanning. In particular, the metal stylus probe and the glass substrate probe with metal scattering member have a disadvantage such that background light is largely detected because light not applied to the tip of the stylus or the scattering member is also incident on the sample.
As mentioned above, various probes capable of scanning at high speeds have been proposed. However, in the case of the planar opening probe and the opening probe with pad, high-speed scanning is allowed, but the light use efficiency is low. By using a model such that a tapering angle of 30° for the minute opening is formed in an aluminum substrate having a thickness of 560 nm, that the diameter of the minute opening is set to 100 nm, and that light having a wavelength of 400 nm is incident, precise electromagnetic calculation was performed by an FDTD (Finite Difference Time Domain) method. As shown in FIG. 1, in the case that a beam is incident on the metal minute opening having a diameter of 100 nm, the beam diameter in a near-field region just after emergence from the minute opening becomes 160 nm (full width at half maximum) larger than the opening size, and the beam profile has an angular shape especially in the polarization direction of the incident light. Accordingly, high-density recording is difficult.
In the surface emitting laser probe with metal minute projection, it is expected that high-speed scanning is allowed, that the light use efficiency is high, and that the background light is less detected. In the case of generating intense near-field light by using the metal minute projection, the shape of such a metal member must be optimized. However, such shape optimization is not disclosed in Japanese Patent Laid-open No. Hei 11-101809. Further, a manufacturing method for such a metal member is also not disclosed in this publication.
In the method of applying a patch antenna and a coaxial cable to light to thereby generate near-field light with a high efficiency or in the method of using a bow-tie metal piece as a minute dipole antenna to thereby generate minute near-field light with a high efficiency, the light intensity is amplified by using a plasmon resonance condition due to the free electrons of metal. FIG. 2 shows the result of precise electromagnetic calculation by the FDTD method in this case as similar to the above. As apparent from FIG. 2, unless a recording surface is placed within a distance of 2 to 3 nm from the bow-tie antenna plane, the effect of light intensity amplification becomes the same as that in a perfect conductor not using plasmon amplification. That is, the light intensity amplification is not observed and a necessary light quantity of 0.5% or more cannot be obtained. Further, an allowable value for the shape of the bow-tie antenna that can satisfy the plasmon condition is small.
There has been reported a method of increasing a recording density by including a lens-shaped substrate in an optical disk medium (Optical Data Storage 2001 Technical Digest pp277–279, Guerra et al., Apr. 22–25, 2001). The object of this method is to solve the problems on dust, head disk interface, etc., and information is recorded/reproduced to/from a recording film by using light focused by a microlens included in the optical disk medium rather than by using near-field light. The recording density can be increased by increasing the refractive index of the lens material. However, there is a limit to increasing of the refractive index, and the recording density in the circumferential direction of the disk cannot be improved.

Optical head and information storage device


A silicone adhesive composition includes 100 parts by weight of a peroxide-curable silicone, 1.2 to 3.2 parts by weight of an organic peroxide curing agent, and 2 to 9 parts by weight of an addition reaction-curable silicone rubber. An adhesive tape includes a base and an adhesive layer placed on the base, the adhesive layer being formed from the above silicone adhesive composition. The adhesive composition exhibits high load bearing capacity even in higher-temperature environments than ever before. The adhesive tape exhibits high load bearing capacity and good shelf life even in such high-temperature environments.

Known adhesives (pressure-sensitive adhesives) include adhesives based on silicones (silicone adhesives). Silicone adhesives are superior to acrylic adhesives and rubber adhesives in properties such as heat resistance, cold resistance, weather resistance, chemical resistance, and electrical insulation, and adhere well to various adherends. Silicone adhesives are thus used in various adhesive tapes such as heat-resistant tapes, electrically-insulating tapes, heat sealing tapes, and plating masking tapes. When an adhesive tape is used in an application that requires heat resistance, a base with excellent heat resistance such as a fluororesin base or a glass cloth base impregnated with a fluororesin is often used with the silicone adhesives. Silicone adhesives include peroxide-curable adhesives and addition reaction-curable adhesives.
To increase the heat resistance of an adhesive tape, not only the properties of a base but also those of a silicone adhesive need to be improved. In view of applications of the adhesive tape, it is desired to improve, in particular, the ability to maintain the adhesive strength in high-temperature environments (load bearing capacity in high-temperature environments) among the properties of the silicone adhesive. Patent Literature 1 (JP 2010-6918 A) discloses a peroxide-curable silicone adhesive composition, the composition capable of maintaining its adhesive strength even at a high temperature above 150° C.

Silicone adhesive composition, adhesive tape, and method for producing adhesive tape


A system and method are provided for routing content requests. On a given server network, content requests comprising a character string may be routed up a hierarchical network topology until a linear chain, corresponding to the character string, is identified. Thus, the content request is forwarded up the hierarchy until an intersecting server network is reached. Then the content request is forwarded down the hierarchy until, along a published linear chain corresponding to the character string, until a content source is reached. Content is provided to the requestor along a reverse path of the content request.

The increase on the number of top-level domains is soon to cause overloading in top-level routers. Domain Name System (DNS) is currently used to resolve a domain name to its corresponding IP address. DNS resolution typically involves a top-level domain name server in communication with several lower-level servers, all of which require domain name registration and then spreading of the domain name (or parts thereof) to the lower-level servers.
Moreover, the Internet Protocol (IP) address to which a domain name resolves, may not be one that ensures the fastest delivery of the requested content. For example, the IP address may not be associated with a server within an optimal proximity to the requestor. Increasing the number of content sources can speed up content delivery. However, DNS does not easily support delivery from multiple sources. Furthermore, many domains do not include geo-locational hints to enable the current DNS system to deduce a region in which the requested content is located. Accordingly, while the existing Internet architecture, and current DNS-based distribution, may be efficient for communication, issues surrounding mass content distribution are becoming increasingly apparent.

System and method for facilitating routing


A device for connecting two clamps, each of which has a rail, including a housing that has two insertion openings, which point away from each other and each of which has an adjoining insertion channel, for inserting a respective rail. The device also includes at least one adapter piece which can be inserted into one of the insertion openings and which reduces the free opening cross section of the insertion channel in order to insert a rail with a different cross-sectional area. The adapter piece has a lining which adjoins a collar. The lining rests against the wall of the insertion channel at least in some regions and forms an insertion channel with a reduced cross section in the inserted state, and the collar rests on an end face of the housing.

The invention relates to a device for connecting two clamps each having a rail, comprising a housing which has two insertion openings which point away from one another and which each have an adjoining insertion channel for inserting a respective rail.
A generic device is described by DE 195 29 268 A1. The document describes clamping tools constructed in different ways, which each form a rail to which a fixed clamping jaw is fastened. A movable clamping jaw bearing a thrust piece which is movable by suitable means in the direction of the fixed clamping jaw. The thrust piece can be moved by a screw spindle. However it is also possible for the movable clamping jaw to be displaced by means of a step clamping mechanism in the direction of the fixed clamping jaw. Clamping tools in this connection are described inter alia in DE 89 03 875, DE 84 09 755, U.S. Pat. No. 6,962,918 and DE 197 31 579 A1.
The two free ends of the rails two clamps can be connected to one another with the generic rail connector. The clamps which are on the market have rails which have different cross-sections from one another.