A recording material for producing offset printing plates includes: a support having a hydrophilic surface, and an infrared-imageable layer including a) a component which is capable of absorbing infrared radiation and converting the infrared radiation to heat, b) a compound which is capable of releasing acid under the action of the heat generated by component a), and c) a polymeric binder having at least one group which is cleaved by the acid released from the compound b), and at least one hydrophilic group, and wherein the layer becomes soluble in an aqueous-alkaline developer in areas struck by infrared radiation.

1. Field of the Invention
The invention relates to infrared-imageable recording materials for producing offset printing plates, as well as to processes for producing offset printing plates from the recording material.
2. Description of Related Art
In conventional processes for producing offset printing forms, a film original is placed on a radiation-sensitive layer. The layer is then irradiated through the original with ultraviolet and/or visible light. More recent developments enable laser beams to act on the radiation-sensitive layer under computer control. In this way direct transfer of digital data to an imagewise-irridated recording material is possible; that is, a film original is no longer required.
Recording materials whose radiation-sensitive layer is sensitized for laser beams with wavelengths in the visible light range generally are known, as disclosed, for example, in EP-A 0 704 764. Lasers which emit in the visible range, however, are relatively expensive. Thus such recording materials have not been widely established.
Infrared lasers, on the other hand, especially laser diodes, are substantially less expensive. However, the use of infrared lasers requires the availability of recording materials which are xe2x80x9cthermally imageablexe2x80x9d, i.e., materials which are sensitized in a wavelength range from about 700 to 1100 nm.
Some thermally imageable materials for producing printing plates are likewise already known. For example, EP-A 0 625 723 discloses a material whose radiation-sensitive layer comprises a mixture of a resol, a novolak, an infrared absorber and a compound which gives a Brxc3x6nsted acid upon dissociation. The infrared absorbers are typically dyes or pigments which fragment on exposure to radiation, thereby producing an exposure contrast, especially cyanines, merocyanines, indolizines, pyrylium compounds or squarylium compounds. Onium salts, in particular, are often used as acid donor compounds. On irradiation, the infrared absorber and acid former are broken down, as a result of which the irradiated areas become soluble in an aqueous-alkaline developer.
However, the above-described solubility behavior is reversed if the material is heated following irradiation, in which case the Brxc3x6nsted acid then catalyzes a crosslinking reaction between the resol and the novolak. Under these conditions, it is the irradiated areas of the layer that are insoluble in an aqueous-alkaline developer solution. In this embodiment, therefore, the material is negative-working. EP-A 0 672 954 describes a very similar recording material. Instead of the onium salt, it employs a haloalkyl-substituted s-triazine as acid former.
EP-A 0 652 483 describes a material which is thermally imageable with IR lasers and from which a printing plate is produced without development. The radiation-sensitive layer of this material is hydrophobic in the nonirradatiated state and accepts offset printing ink. It includes a substance which absorbs infrared radiation and converts it to heat. It also includes a polymer having groups which on exposure to heat and/or acid, are transformed into more hydrophilic and more strongly polar groups. Reactive groups mentioned are tert-alkyl carboxylates, tert-alkyl carbonates, benzyl carboxylates, cyanobenzyl esters, dimethylbenzyl esters and alkoxyalkyl esters (especially tetrahydropyran-2-yl esters). The layer preferably also includes a compound which produces an acid on exposure to heat. In the irradiated areas, the layer accepts an aqueous dampening solution and repels the printing ink. Overall, however, the layer is retained. Printing (hydrophobic) and nonprinting (hydrophilic) areas differ only in their wettability with the dampening solution/ink mixture in the printing press. With a printing plate of this type, however, it is possible only to achieve a very low print run (a few thousand prints). Moreover, the hydrophilic areas of the layer exhibit much poorer acceptance of the dampening solution than an aluminum oxide surface, resulting in a poorer water supply. Since exposed and unexposed (still heat-sensitive) layer areas are present alongside one another, generally it is also not possible to render such a plate more mechanically resistant by baking (which would lead to a higher print run). As IR absorbers, preference is given to those substances which on exposure to IR radiation generate heat and acid. Examples given are aromatic diammonium salts of strong acids. Trihalomethyl-s-triazines are preferred as additional acid donors.
WO 90/12342 describes a thermally imageable material for colorproofing techniques which uses polymeric binders that break down on exposure to heat and/or acid. The expansion of the gaseous breakdown products evolved in the IR-exposed areas of the material leads to an ablation. By transferring the ablated material from an IR-transparent support film to a receiver sheet it is possible to obtain the desired color image. This process, of course, operates without wet development. As IR absorbers preference is given to substances which give off heat and acid under the influence of IR radiation (examples being diammonium salts of strong acids). Also mentioned as an IR absorber is carbon black, whose disadvantage, however, is seen in its usefulness only for black progressives. Binders used are those which are broken down rapidly by acid, preferably at temperatures below 100xc2x0 C.; for example, nitrocellulose, polycarbonates and certain polyurethanes, and also other binders which can be thermolized to form tertiary carbonium ions with subsequent proton elimination (autocatalysis of the breakdown reaction). As a model of the latter, mention is made of the known thermally and/or acid-catalyzed decomposition of phenols with tert-butyloxycarbonyl groups to form carbon dioxide, isobutene and protons (see also Frxc3xa8chet et: al., J. Imaging Sci. 30 (2) [1986] 59). The formation of the gaseous decomposition products brings about the ablation of the material on IR irradiation.
Materials which are subjected to wet development following acid-catalyzed thermolysis are disclosed, for example, in EP-A 0 366 590 and in Ito et al., Polym. Eng. Sci. 23 [1983] 1012. They form the basis of highly sensitive photoresists that are sensitized for the UV range. A preferred polymer is poly(tert-butoxycarbonyloxystyrene). A disadvantage of these materials is their low thermal stability, brought about by autocatalytic decomposition with the participation of acidic phenolic hydroxyl groups that are still present in the polymer (see Ito et al., J. Polym. Sci. 24 [1986] 2971). This Ito reference does not disclose or mention the use of these materials in connection with the production of printing plates which place special requirements on polymers in terms both of the developer resistance and in terms of the print run. There is also no disclosure in this Ito reference regarding the sensitization of such materials for radiation in the IR range.
The use of polymers having acid-labile groups as binders for printing plates is described, for example in EP-A 0 683 435. The polymers preferably include monomer units comprising 4-tert-butoxycarbonyloxystyrene (BOCST). Utmost sensitivity for UV/VIS, extremely low removal of material from unexposed areas and very high thermal stability are achieved if the binder includes not only the monomer units (I) having acid-labile groups, e.g., BOCST, but also monomer units (II) having phenolic hydroxyl groups and monomer units (III) having at least one aliphatic hydroxyl group. The content of (II+III) is responsible for good developability in aqueous-alkaline solution. If the content of (II) is too high, the auto-catalytic effect described above reduces the thermal stability of the binder and increases the removal of material from unexposed areas. If some of the monomer units having phenolic hydroxyl groups are replaced by those having aliphatic hydroxyl groups, the thermal stability is improved. The thermal stability is also of particular importance because printing plates produced with this binder, after imaging and before development, require subsequent heating at about 100xc2x0 C. The best results are obtained when the proportion of (I+III) is from 10 to 80%. The material described, although of excellent stability on storage at elevated temperatures, is nevertheless not thermally imageable, since it does not include any IR absorbers.
An object of the present invention was therefore to provide a recording material which can be imagewise irradiated with IR radiation sources, especially IR lasers, and subsequently developed to produce plates for conventional offset printing, i.e., wet offset printing. It was further an object to provide offset printing plates, as well as processes for preparing recording materials and offset printing plates.
These other objects are achieved, inter alia, by use of a radiation sensitive layer including an IR absorber, a thermal acid former and a polymeric binder that carries not only acid-labile but also hydrophilic groups. The present invention accordingly provides a recording material suitable for producing offset printing plates comprising: a support having a hydrophilic surface, and an infrared-imageable layer comprising a) a component which is capable of absorbing infrared radiation and converting the infrared radiation to heat; b) a compound which is capable of releasing acid under the action of the heat generated by component a); and c) a polymeric binder including at least one group which is cleaved by the acid released from the compound b), and further including at least one hydrophilic group, and wherein the infrared-imageable layer becomes soluble in an aqueous-alkaline developer in areas struck by infrared radiation. It is believed that imaging is effected as described. However, applicants do not wish to be bound by any theory.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
Any support with a hydrophilic surface can be used in the present recording material. The support with a hydrophilic surface is preferably a mechanically, chemically and/or electrochemically roughened and anodized foil or plate, and can suitably be made from aluminum or an aluminum alloy. The weight of the hydrophilic aluminum oxide layer produced by the anodizing is in general from 0.5 to 5.0 g/m2, preferably from 1.0 to 3.0 g/m2.
The infrared-absorbing component a) is generally capable of absorbing IR radiation and converts it to heat, generally without itself giving off any acid. Preferably, component a) comprises or consists of particles of carbon black. Particularly suitable carbon blacks include lamp, furnace or channel blacks, suitably with an average primary particle size of up to 80 nm. The primary particle size is preferably, however, not more than 60 nm and, with particular preference, not more than 30 nm. The surface area as measured by the widely known method of Brunauer, Emmett and Teller (BET surface area) is preferably at least 30 g/m2.
In a preferred embodiment carbon blacks are employed as component a) that have been subjected to (post)oxidation, producing acidic units on the surface of the carbon black particles. Aqueous dispersions of such carbon blacks preferably exhibit a pH of less than 7, in particular a pH in the range of from 3 to 6.5. Particularly suitable carbon black particles are those that have been dispersed with a polymer beforehand. Prior dispersing can be carried out, for example, using the binder c). Alternatively it is possible to use other binders, particularly those that are soluble in aqueous-alkaline solution, such as phenolic resins (novolaks), polyvinyl acetates, polyvinyl acetals, polyvinyl-pyrrolidones, polyvinyl ethers, poly(hydroxystyrenes) or cellulose derivatives.
The proportion of the IR-absorbing component a) is a result effective amount and preferably is from 1.0 to 30.0% by weight, with particular preference from 5.0 to 10.0% by weight, based in each case on the overall weight of the nonvolatile constituents of the mixture which will form the layer.
Suitable substances that can be used as acid formers b) include those which release a strong acid under the action of the heat generated by the IR absorber a). Preferred acid formers include diazonium, phosphonium, sulfonium, and iodonium salts of strong acids. Particular preference is given to hexafluorophosphates, hexafluoroantimonates and halogenated alkanesulfonates (preferably aromatic or heteroaromatic mono- or bisdiazonium 1,1,2,3,3,3-hexafluoropropanesulfonates). The acidity of the hydrogen chloride that is released in the breakdown of trichloromethyl-s-triazines, on the other hand, is generally not sufficient to cleave the acid-labile group without subsequent heating. Thus, surprisingly these compounds typically should not be utilized as acid donors for the purposes of the present invention.
The proportion of the acid-forming compound b) is an amount effective to give desired results and preferably from 0.1 to 20.0% by weight, with particular preference from 1.0 to 10.0% by weight, based in each case on the overall weight of the nonvolatile constituents of the mixture forming the layer.
The acid-labile group in the polymeric binder c) preferably contains at least one acid-cleavable Cxe2x80x94Oxe2x80x94C bond. Particularly suitable acid-cleavable groups of this kind include those of the formula xe2x80x94Oxe2x80x94COxe2x80x94OR2 in which R2 is a (C3-C11)alkyl, (C3-C11)alkenyl or (C7-C11)aralkyl radical, preferably a C4-alkyl radical and with particular preference a tert-butyl radical. The acid-cleavable group of the formula xe2x80x94Oxe2x80x94COxe2x80x94OR2 is judiciously attached to a substituted or unsubstituted phenyl or phenylene group located in a main chain or a side chain of the polymer.
The hydrophilic groups of the polymeric binder c) can be any hydrophilic group and preferably comprise phenolic or aliphatic hydroxyl groups, carboxyl, mercapto, sulfonamido or amino groups, with particular preference being given to binders having two types of hydrophilic groups which show a difference in pKa-values of at least 3 units. Especially preferred are phenolic and aliphatic hydroxyl groups. Very particular preference is given to binders c) which comprise phenolic and aliphatic hydroxyl groups at the same time in addition to the acid-cleavable groups. Between phenolic and aliphatic hydroxyl groups there is generally a pKa difference of more than 3.
Suitable aliphatic hydroxyl groups to be used in the polymeric binder c) include hydroxy(C2-C8)alkoxy groups or dihydroxy(C2-C8)alkoxy groups. In a particularly preferred embodiment the polymeric binder c) is a copolymer including monomer units comprising at least one acid-cleavable Cxe2x80x94Oxe2x80x94C bond, monomer units comprising at least one aliphatic hydroxyl group, and monomer units comprising at least one phenolic hydroxyl group. Such binders are described, for example, in EP-A 0 683 435, hereby incorporated by reference in its entirety. The proportions of the monomer units having aliphatic and the monomer units having phenolic hydroxyl groups are together preferably at least 65%, based on the sum of all monomer units. The binder c) also may suitably comprise a terpolymer consisting essentially or consisting only of these monomer units.
In one embodiment, the proportion of monomer units having acid-labile groups (groups cleaved by acid) is preferably from 20 to 30%, that of the monomer units having phenolic hydroxyl groups is preferably from 50 to 60%, and that of the monomer units having aliphatic hydroxyl group is preferably from 15 to 25%, based in each case on the overall number of monomer units. The comonomer having aliphatic hydroxyl groups can be, with particular preference, 4-(2,3-dihydroxypropoxy)styrene.
A suitable synthesis of the binders of the invention is described, for example, in EP-A 0 683 435. The copolymer may, however, also feature further monomer units provided they do not impair the developability or other critical aspects of the layer.
The proportion of the polymeric binder c) is preferably from 20 to 80% by weight, more preferably from 30 to 60% by weight, based in each case on the overall weight of the nonvolatile constituents of the mixture forming the layer.
The IR sensitized layer may also optionally include customary additives in customary amounts. To improve the surface texture, for example, a small amount of silicone oil may be added. Further suitable additives include surfactants and the like.
The recording material of the invention can be prepared by any desired method. For example, a suitable recording material can be prepared by coating a support with a dispersion of the thermally sensitized mixture. The liquid phase of the dispersion preferably comprises customary coating solvents, such as tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate or butanone. The constituents dissolved therein (components b) and c)) should generally be soluble in the coating solvent. Drying can then be carried out until the layer is virtually free from solvent. Heating at about 100xc2x0 C. for one minute is generally sufficient, although the time can be adjusted depending on the application and materials used. Coating can be carried out, for example, by spin coating, casting or the like. The weight of the dried, thermally sensitized layer on the support can be varied as desired and is preferably from about 0.5 to 5 g/m2, more preferably from 1.0 to 3.0 g/m2 and, with particular preference, from 1.8 to 2.5 g/m2.
The present invention also provides a process for producing offset printing plates from the recording material of the invention. The printing plates should generally permit a high print run even without requiring subsequent baking.
Any known process can be used to produce offset printing plates using the instant recording material. In a suitable process, the recording material is first subjected to imagewise irradiation and then developed in an aqueous-alkaline developer, whereupon the irradiated areas of the imageable layer are removed and the hydrophilic surface of the support is exposed. Particularly suitable exposure apparatus comprises customary IR lasers, e.g., diode lasers or Nd-YAG lasers which emit radiation, preferably in a wavelength range from 700 to 1500 nm, more preferably from 700 to 1100 nm. For irradiation, the recording material can be positioned, for example, in a flatbed unit, in an external-drum or in an internal-drum exposure unit.
The aqueous-alkaline developer should generally have a pH of at least 8, more preferably from 10 to 14. As alkaline component it can comprise, in particular, amines (especially ethanolamine), borates, carbonates (especially Na2CO3), hydroxides (especially NaOH or KOH), silicates (especially ortho- or metasilicates) or phosphates (especially trisodium phosphate). In the case of silicate developers, the proportion of silica to alkali metal oxide is preferably greater than or equal to 1. The use of such a ratio helps to ensure that the aluminum oxide layer of the support is not damaged.
In addition, the developer may comprise buffer substances, complexing agents, defoamers, (organic) solvents, corrosion inhibitors, colorants, surfactants, and/or hydrotropes, as well as other additives or the like.
After development, the printing plate can be clamped directly into a printing press. If this is not to be the case, the plate can be judiciously protected with a gumming solution comprising, for example, synthetic or natural water-soluble (co)polymers, such as polyvinyl alcohol, poly(meth)acrylic acid, poly(meth)acrylamide, polyhydroxyethyl (meth)acrylate, polyvinyl methyl ether, gelatin, dextran, pullulan, cellulose, gum arabic, or alginic acid.
Finally, the present invention also provides the actual printing plate produced from the recording material of the invention.
The invention is described further by the following examples, whose intention is to illustrate the invention but not to restrict it.
The abbreviation xe2x80x9cpbwxe2x80x9d herein denotes parts by weight. Percertages are by weight unless stated otherwise.

Infrared-imageable recording material and offset printing plates produced from it


The present invention relates to a process for coating a substrate by applying to a substrate a coating composition containing

1. Field of the Invention
The present invention relates to a process for coating a substrate in which certain liquid coating compound compositions, after being applied to a body (substrate), are cured by irradiation with ultraviolet (UV) light and thermal post-reaction.
2. Description of the Prior Art
Curing coating compositions or lacquers, by UV light, is very efficient due to the low energy and solvent consumption and the high speed. A disadvantage often cited, however, is that of inadequate adhesion of the coatings to certain substrates, inter alia, metal. For example, EP-A 0 928 800 describes a coating system of urethane (meth)acrylate isocyanates, which contains free isocyanate (NCO) groups and groups which react with NCO groups. For this reason the coating system is prepared as two components which are mixed only shortly before application of the coatings. After mixing the pot life is limited to a few hours.
A one-component system (with regard to the storage of the coating composition) is described, e.g., in U.S. Pat. No. 4,961,960. The system contains a) a light-curing monomer or polymer having a plurality of ethylenically unsaturated groups and b) an adduct of a polyisocyanate, a blocking agent for polyisocyanates and a photo-polymerizable alcohol having at least one ethylenically unsaturated group. Moreover, the requirement is made that component a) is free from NCO groups or blocked NCO groups and that the sum of the ethylenically unsaturated groups contained in a) and b) is at least 4. It is described that the use of polyisocyanates b) that do not contain ethylenically unsaturated group(s), without thermal post-curing, leads to non-resistant films, and with thermal post-curing to films with an inadequate appearance.
Because polyisocyanate products that contain both ethylenically unsaturated groups and blocked NCO groups are difficult to prepare, an object of the present invention is to provide a process for coating which, even with the use of blocked polyisocyanates in combination with UV-curing oligomers or polymers, leads to coatings which are resistant after UV curing and, after additional thermal curing, to optically perfect coatings.
This object may be achieved according to the present invention as described hereinafter.
The present invention relates to a process for coating a substrate by applying to a substrate a coating composition containing
A) at least one compound which contains at least two (meth)acrylate groups and at least one isocyanate-reactive group and which is free from isocyanate groups and blocked isocyanate groups,
B) at least one blocked polyisocyanate, which does not contain any ethylenically unsaturated groups and
C) at least one photoinitiator,
curing the coating composition by the action of UV light and post-curing by increasing the temperature of the coating.
The term xe2x80x9c(meth)acrylatexe2x80x9d, within the meaning of the invention, relates to esters of acrylic acid and/or methacrylic acid.
Component A) is selected from known radiation-curing binders, provided that the binders contain at least isocyanate-reactive group, preferably at least one hydroxyl group. Examples of these binders include epoxy acrylates, polyester acrylates, polyether acrylates or partially (meth)acrylated trifunctional or higher functionality alcohols having a molecular weight below 600. The use of epoxy acrylates preferably having an average of 1.5 to 3 hydroxyl groups is preferred. Component A) may preferably contains 2 to 4 ethylenically unsaturated groups.
The preparation of epoxy acrylates is described, for example, in P.K.T. Oldring (Ed.), Chemistry and Technology of UV and EB Formulations For Coatings, Inks and Paints, Vol. 2, 1991, SITA Technology, London, p. 37 -68 and in EP-A 816 412. Glycidyl ethers are usually reacted with carboxylic acids and the resulting products contain secondary hydroxyl groups. These products are preferred for the process according to the invention.
Polyester acrylates containing hydroxyl groups and having an OH number of 60 to 300 mg KOH/g may also be used as component A). To prepare the hydroxy-functional polyester acrylates, the following monomers may be used:
1. (Cyclo)alkane diols (i.e., dihydric alcohols with (cyclo)aliphatically bound hydroxyl groups) having a molecular weight of 62 to 286, such as ethane diol, propane 1,2- and 1,3-diol, butane 1,2-, 1,3-and 1,4-diol, pentane 1,5-diol, hexane 1,6-diol, neopentyl glycol, cyclohexane-1,4-dimethanol, cyclohexane 1,2- and 1,4-diol, 2-ethyl-2-butylpropane diol. Also suitable are diols containing ether oxygens such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene, polypropylene or polybutylene glycols having a maximum number average molecular weight of 2000, preferably 1000, and more preferably 500. Reaction products of the above-mentioned diols with xcex5-caprolactone or other lactones may also be used as diols.
2. Trihydric and higher functionality alcohols having a molecular weight of 92 to 254 such as glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol. Also suitable are polyethers started on these alcohols such as the reaction product of 1 mole of trimethylolpropane with 4 moles of ethylene oxide.
3. Monoalcohols such as ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, hexan-1-ol, 2-ethylhexanol, cyclohexanol and benzyl alcohol.
4. Dicarboxylic acids having a molecular weight of 104 to 600 and/or the anhydrides thereof, such as phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, cyclohexane dicarboxylic acid, maleic anhydride, fumaric acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid and hydrogenated dimer fatty acids.
5. Higher functionality carboxylic acids and the anhydrides thereof such as trimellitic acid and trimellitic anhydride.
6. Monocarboxylic acids such as benzoic acid, cyclohexane carboxylic acid, 2-ethylhexanoic acid, caproic acid, caprylic acid, capric acid, lauric acid, natural and synthetic fatty acids.
7. Acrylic acid, methacrylic acid and dimeric acrylic acid.
Polyester acrylates containing hydroxyl groups contain the reaction product of at least one compound from group 1 or 2 with at least one compound from group 4 or 5 and at least one compound from group 7.
It is also possible to react a portion of (excess) carboxyl groups, particularly (meth)acrylic acid, with mono-, di- or polyepoxides. This reaction may be used particularly to increase the OH number of the polyester acrylate since one OH group is produced during the epoxide-acid reaction. The acid number of the resulting product is less than 20 mg KOH/g, preferably less than 10 mg KOH/g and more preferably less than 5 mg KOH/g.
The preparation of polyester acrylates is described, for example, in P.K.T. Oldring (Ed.), Chemistry and Technology of UV and EB Formulations For Coatings, Inks and Paints, Vol. 2, 1991, SITA Technology, London, p. 123-135.
It is also possible to use reaction products of the above-mentioned epoxy acrylates, polyester acrylates, polyether acrylates or partially (meth)acrylated trifunctional or higher functionality alcohols having a molecular weight below 600 with di- or polyisocyanates as long as the reaction products contain at least one isocyanate-reactive group, preferably at least one hydroxyl group. Suitable di- or polyisocyanates include (cyclo)aliphatic, araliphatic and aromatic compounds, such as butylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (2,2,4 and/or 2,4,4-trimethylhexamethylene diisocyanate), bis(isocyanatocyclohexyl)methane, toluene diisocyanate, diphenylmethane diisocyanate, isocyanatomethyl-1,8-octane diisocyanate and derivatives of these diisocyanates containing urethane, isocyanurate, allophanate, biuret, uretdione and/or iminooxadiazine dione groups.
Suitable blocked polyisocyanates for use as component B), which contain no ethylenically unsaturated groups, are known and described, for example, in Progress in Organic Coatings, Vol. 36, 3, 1999, 148-172. Blocked polyisocyanates are generally prepared by reacting a polyisocyanate with a blocking agent.
Suitable polyisocyanates include (cyclo)aliphatic, araliphatic and aromatic compounds, preferably (cyclo)aliphatic compounds. Examples include butylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (2,2,4 and/or 2,4,4-trimethylhexamethylene diisocyanate), bis(isocyanatocyclo-hexyl)methane, isocyanatomethyl-1,8-octane diisocyanate, derivatives of these diisocyanates containing urethane, isocyanurate, allophanate, biuret, uretidione and/or iminooxadiazine dione groups and mixtures thereof. The derivatives of HDI and/or IPDI containing isocyanurate groups are particularly preferred.
Suitable blocking agents are known and include monofunctional blocking agents such as malonates, acetates, lactams, oximes, pyrazoles, triazoles, imidazoles, amines and mixtures thereof. The use of blocking agents that dissociate at a temperature of up to 180xc2x0 C., preferably of up to 160xc2x0 C., is particularly preferred. Diisopropylamine, butanone oxime, cyclohexanone oxime and/or 3,5-dimethylpyrazole are preferred. Diisopropylamine is particularly preferred.
The equivalent ratio of blocked NCO groups in B) to isocyanate-reactive groups in A) is 1:0.2 to 1:2, preferably 1:0.5 to 1:1.2 and more preferably 1:0.9 to 1:1.
Photoinitiators C) are known and include initiators which are able to initiate free-radical polymerization after irradiation with high-energy radiation such as UV light. Suitable photoinitiators are described, for example, in P.K.T. Oldring (Ed.), Chemistry and Technology of UV and EB Formulations For Coatings, Inks and Paints, Vol. 3, 1991, SITA Technology, London, p. 61-325. Examples include 2-hydroxyphenyl ketones such as 1-hydroxycyclohexyl-phenyl ketone; benzil ketals such as benzil dimethyl ketal; acylphosphine oxides such as bis-(2,4,6-trimethylbenzoyl)phenylphosphine oxide; diacylphosphine oxides; benzophenone; and derivatives thereof. They are used individually or in mixtures, optionally together with accelerators or co-initiators. They are used in amounts of 0.1 to 10 parts by wt., preferably 2 to 7 parts by wt. and more preferably 3 to 4 parts by wt, based on solids content of the coating composition.
In order to prepare the coating composition, components A), B) and C) are mixed by conventional methods. Known additives used in coating technology, particularly the technology of radiation-curable coatings and polyurethane chemistry, may also added to the coating compositions.
In order to obtain weathering resistance for the cured coating and optionally the substrate, a UV absorber, preferably with an absorption range up to max. 390 nm and a known as HALS (HALS=hindered amine light stabiliser) stabilizer may be added. Suitable UV absorbers include triphenyltriazines such as Tinuvin 400 (Ciba) or oxalic acid dianilides such as Sanduvor 3206 (Clariant). The UV absorbers are preferably added in amounts of 0.5% to 3.5%, based on solid binder.
Suitable HALS include Tinuvin 292 or Tinuvin 123 (Ciba) or Sanduvor 3058 (Clariant). These HALS are preferably added in amounts of 0.5% to 2.5%, based on solid binder. The use of HALS and UV absorbers in combination with photoinitiators is well known and described, for example, in A. Valet, Lichtschutzmittel fxc3xcr Lacke, Vincentz Verlag, Hanover, 1996.
The addition reaction of the isocyanate groups liberated during post-curing with the isocyanate-reactive groups may be accelerated in an known manner using suitable catalysts such as tin octoate, dibutyltin dilaurate or tertiary amines.
Examples of other coating additives include deaerating agents such as polyacrylates, coupling agents such as aminoalkyltrialkoxy silanes and flow control agents such as polysiloxanes.
In addition to the preparation of clear coats, it is also possible to prepare colored coatings by adding dyes or pigments. As is known, the photoinitiator must be adapted to colored coating compounds e.g., by proportional use of a photoinitiator with a long-wave ( greater than 350 nm) absorption band.
Depending upon the method of application selected, the viscosity of the coating composition may be suitably adjusted by adding solvents. Suitable solvents include those that are inert towards blocked isocyanate groups and Cxe2x95x90C double bonds such as esters, ketones, ethers, ether esters, alkanes and aromatic solvents such as xylenes or toluene.
When a substrate is coated in accordance with the invention, the coating composition is applied to various substrates by conventional methods such as spraying, roller coating, knife coating, pouring, brushing, centrifugal force, or dipping, preferably by spraying or roller coating. Examples of suitable substrates include glass, metals (such as aluminium or steel sheets which have optionally undergone a pretreatment or metal in the form of coils), non heat-sensitive wood or plastic materials, mineral materials (such as cement, clay, minerals or ceramics), or substrates that have already been coated or primed, e.g., automobiles or automobile parts. It is also possible to coat substrates composed of several of the materials mentioned.
The coating system is cured in successive steps:
Step 1: By flashing off optionally added solvents. This takes place at room temperature or at elevated temperature, preferably up to 80xc2x0 C. Optionally also by means of a stream of heated gas (e.g. air). The temperature increase may be brought about by known methods such as infrared or near-infrared radiators or by ovens heated in other ways.
Step 2: By UV curing using, for example, commercial mercury high- or medium-pressure radiators. These radiators may be doped by other elements and preferably have an output of 80 to 240 W/cm lamp length. Excimer radiators which emit UV light with wavelengths of 160 nm to 400 nm are also suitable. Surprisingly, it was found that although the coating at this time still contains the uncrosslinked constituent B), the surfaces obtained are already dust-dry and resistant to many solvents.
Step 3: By crosslinking the NCO-containing constituents with the isocyanate-reactive compounds. At elevated temperatures in the coating, reactive groups, preferably NCO groups, are produced initially from the blocked isocyanates. This takes place at temperatures above 80xc2x0 C. and below 450xc2x0 C. The residence times of the coatings at these temperatures is at least 10 seconds, advantageously at least 60 seconds to 60 minutes and more preferably at least 2 to 10 minutes. The temperature may be increased by known methods such as infrared or near-infrared radiators or by ovens heated in other ways. When post-curing is complete, a cooling phase may follow before the coated articles undergo further handling.
It was surprising that, during post-curing, the blocking agents formed when the NCO groups are unblocked and which are volatile at these temperatures do not lead to disturbance of the film or surface. As the examples below illustrate, defect-free, optically attractive coatings are obtained.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.

Abstract: C) at least one photoinitiator,


A method and corresponding apparatus for authenticating a client for a server when the client and server have different security mechanisms. An intermediary system known as an authentication gateway provides for authentication of the client using the client security mechanism, and impersonation of the client in a call to a server that the client wishes to access. The client logs in to the authentication gateway and provides a user name and password. Then the authentication gateway obtains and saves security credentials for the client, returning an access key to the client. When the client wishes to call the server, the client calls the authentication gateway acting as a proxy server, and passes the access key, which is then used to retrieve the security credentials and to impersonate the client in a call to the server. Any output arguments resulting from the call to the server are returned to the client through the authentication gateway.

This invention relates generally to distributed computing systems, or computer networks, and more particularly to techniques for authentication of users of computing resources in the distributed computing context. Networks of computers allow the sharing of computer resources among many users. In this type of distributed computing environment, some systems function as "servers" and others function as "clients" of the servers. A server provides some type of service to client systems. The service may involve access to a database or other file system, access to printers, or access to more powerful computing resources. A client system makes requests for service from a server system and, in many instances, the server requires "authentication" of the user before the service will be provided and, in some cases, the client will require that the server be authenticated, to make sure that someone is not posing as the server. Client authentication implies the presence of a security mechanism whereby the server can verify that the client is authorized to receive the requested service.
Security mechanisms for client authentication tend to evolve separately and independently for different types of systems and network hardware. As networks grow in size and diversity, there is a significant problem in being able to authenticate client systems easily. The problem is most apparent in the integration of personal computers (PCs) with networks of larger computer systems. For example, if the larger systems employ Distributed Computing Environment (DCE) security protocols, it will in general be inconvenient and costly to provide each connected PC with the appropriate software necessary for authentication in accordance with DCE security. Consequently, PCs do not provide DCE security and a PC client cannot directly access DCE servers.
Stated more generally, the problem is to provide a mechanism that would allow a server to authenticate a client that had no knowledge of the server's security protocol. The present invention is directed to this end.

Method and apparatus for authenticating a client to a server in computer systems which support different security mechanisms


A device and a process for tempering at least parts of the cross section of sequentially produced profiled rolling stock from the rolling heat and for the subsequent cooling thereof to room temperature. The device comprises a hardening device comprising at least to liquid cooling devices arranged next to each other and a transport device having rests for the rolling stock that can be moved across the entire hardening device. Thereby the liquid cooling devices can simultaneously and independently be supplied with rolling stock to be hardened.

The present application claims priority under 35 U.S.C. xc2xa7119 of Austrian Patent Application No. 1442/2001, filed Sep. 13, 2001.
1. Field of the Invention
The invention relates to a device for the hardening of rolling stock having a large lengthwise extension at a high throughput. More precisely defined, the invention relates to a device for the thermal tempering of at least portions of the cross section over the lengthwise extension of sequentially produced profiled rolling stock from the rolling heat, in particular for hardening at least the head of rails having a length greater than 50 m, and subsequent cooling to room temperature, consisting essentially of a roller table, a means for arranging the rolling stock in axial alignment, a transport means having a rest for the rolling stock for the transport thereof in transverse direction, a hardening device with a manipulation arrangement, and a cooling bed.
2. Discussion of Background Information
In order to improve the properties of the material, a rolling stock is usually subjected to a thermal tempering treatment that advantageously is carried out with the use of the rolling heat. This tempering, which essentially affords an increase in the mechanical properties of the material such as hardness, abrasion resistance, and the like, can be performed over the entire cross section or, as is common with a running rail, only over partial sections of the same. Here, the rolling stock which is in its austenitic microstructural state, or partial sections of the cross section of the same, is dipped into a cooling medium over its entire length and, in this manner, a transformation of the microstructure is achieved in the desired manner.
Devices for carrying out such tempering processes are known (EP-0441766 B1) and have proven suitable with regard to an improvement of the use properties of railroad rails.
Depending on the final rolling temperature and depending on the specific mass or mass per length unit, respectively, of the rolling stock, thermal tempering thereof requires a corresponding submersion time or residence time in the cooling liquid, such that the throughput through the tempering device is limited. In other words, the maximum possible throughput through a submersion tempering installation with a cooling basin limits the output of the rolling device arranged before it.
Modern roll-forming lines with prearranged heating furnaces particularly for continuous casting input stock usually have potential rolling outputs that are greater than the throughput of known submersion tempering installations, so that with a sequential production of hardened rails, the rolling output has to be reduced.
In order to avoid this disadvantage, which is in particular an economic one, it has already been recommended to temper the rolling stock as it moves through a cooling path provided with spraying means. However, this continuous pass process requires long lengths of the installation and usually does not result in the required material quality of the rolling stock.
The invention aims at avoiding the deficiencies and, in particular, the economic disadvantages, of known thermal treatment installations for rolling stock of the type mentioned at the outset and at providing a device that ensures a high quality and good use properties of the rolling stock produced and has a high output and renders possible the treatment and thermal tempering of sequentially produced bar stock, particularly of rails having lengths of more than 50 m, on roll lines with high output while using rolling heat.
This goal is attained in a generic device in that the roller table has a device for longitudinally positioning the rolling stock which is supplied supported in at least one cross-sectional region, and an assigned alignment means, in that the hardening device is formed of at least two liquid cooling devices arranged next to one another essentially parallel in their lengthwise direction to the alignment means with manipulators for a movement of the rolling stock, in that the deposit region of the cooling bed is located next to, and parallel to the lengthwise extension of, the liquid cooling devices, and in that the means for transport in transverse direction has at least two supporting arms that are simultaneously movable between the roller table rolls, each having rolling stock rests arranged on the end side, that these rests on the supporting arms can be moved in transverse direction from the alignment position in the region of the roller table into the deposit region of the cooling bed, lowered, and raised in such a way that exclusively the rests protrude beyond the transport surface of the roller table and the upper edge of the roller table, respectively.
The present invention provides a device for tempering at least parts of the cross section of sequentially produced profiled rolling stock from the rolling heat and for the subsequent cooling thereof to room temperature. This device consists essentially of (a) a roller table that comprises rolls and receives said rolling stock, (b) an alignment device for axially aligning the rolling stock, (c) a transport device for transporting the rolling stock in transverse direction, (d) a hardening device for hardening the rolling stock which comprises a manipulator arrangement for manipulating the rolling stock to be hardened, and (e) a cooling bed for the hardened rolling stock, said cooling bed comprising a deposit region. The roller table (a) further comprises a positioning device for positioning in longitudinal direction the rolling stock which is supplied thereto, which positioning device comprises said alignment device (b). The transport device (c) comprises at least two supporting arms that are simultaneously movable between the rolls of the roller table. Each of these arms, in turn, comprises at an end section thereof a rest for supporting said rolling stock. The rests on the supporting arms can be moved in transverse direction from an alignment position in the region of the roller table into the deposit region of the cooling bed (e) and can be raised in such a way that only the rests are above an upper surface of the roller table. The hardening device (d) comprises at least two liquid cooling devices and manipulators for moving the rolling stock. These liquid cooling devices are arranged next to one another and essentially parallel to the alignment device (b). Furthermore, the deposit region of the cooling bed is arranged next to and parallel to the lengthwise extension of the liquid cooling devices.
In one aspect of the device, the rolling stock is a rail, e.g., a rail having a length of greater than 50 m. This rail may, for example, be a running rail or a railroad rail. In another aspect, at least the head of the rail is hardened. In yet another aspect, the roller table can support the rail in two cross-sectional regions thereof.
According to another aspect of the device, the positioning device comprises an electronically controllable device and/or an alignment bar and/or a stop.
According to still another aspect, the liquid cooling devices comprise submersion basins. These submersion basins may comprise stops for leveling and aligning the rolling stock. The stops may be arranged, for example, horizontally and/or vertically. In another aspect, a holding-down device for pressing down the rolling stock against said stops may additionally be provided.
According to a further aspect, each submersion basin has manipulators assigned to it. Each of said manipulators may be capable of, e.g., taking the rolling stock off the rests of the transport device (c), introducing the rolling stock into a submersion basin, lifting the rolling stock out of a submersion basin, and/or placing the rolling stock back on said rests. Moreover, said manipulators may be capable of introducing a rail xe2x80x9chead downxe2x80x9d into a submersion basin.
According to yet another aspect of the device, each of said supporting arms has exactly one rest arranged thereon. In another aspect, the supporting arms originate in the region of the roller table. Alternatively, the transport device (c) may be arranged in the region of the cooling bed.
The present invention also provides a process for tempering at least parts of the cross section of sequentially produced profiled rolling stock from the rolling heat and for subsequently cooling said rolling stock to room temperature. This process comprises axially aligning said rolling stock, transporting the rolling stock to a hardening device and treating at least parts of the cross section of the rolling stock therewith, and allowing the rolling stock so treated with the hardening device to cool to room temperature. In this process, the residence time in the hardening device exceeds the supply frequency of the rolling stock to be tempered and the process is carried out by means of a device as described above.
The advantages attained by the invention lie especially in the fact that, using the device, it is possible to position and axially align the rolling stock in a simple manner in sequence in the transverse transport region of the roller table with a high degree of precision, it being possible, by means of the rolling stock rests of the means for transport in transverse direction, to simultaneously, i.e., without interfering with the adjustment and the axial alignment process, transport a previously aligned and provided piece of rolling stock into the deposit regions of the cooling devices or from there into the deposit region of the cooling bed or from the roller table directly onto the cooling bed. In this connection, it is important that only the rolling stock rests of the supporting arms of the means for transport in transverse direction, which arms are movable between the rolls, are capable of being raised above the upper level of the rolls of the roller table or their transport surface, respectively. With this embodiment of the device, it is possible to arrange at least two hardening devices on one side of the roller table such that a cooling bed must be provided on one side only, which yields economic advantages. A piece of rolling stock that is positioned on the roller table and axially aligned can be lifted off the roller table by means of the rests of the supporting arms and, for example, be laid down in a deposit region of a liquid cooling device that is embodied as a manipulator. Thereafter the means for transport in transverse direction is freed up for transporting further pieces of rolling stock, where the manipulator can, alone and independently, orient the deposited rolling stock in its cross-sectional position, place it in the cooling medium at least partially, lift it out, and provide it for transport to the cooling bed. This separation of the transport in transverse direction of the rolling stock, which is essential to the invention, even past occupied cooling devices with, eventually, a deposit on the cooling bed, and a precise placement of the rolling stock in the cooling medium improves the precision of the manipulation as well as of the cooling treatment and reliably affords hardened rolled products with consistently high quality. In an advantageous and economical manner, the output and throughput, respectively, of the device is approximately doubled when using two hardening devices next to one another.
If the device is intended for a rolling stock in the form of a running rail or a railroad rail that rests on the roller table in two cross-sectional regions and the positioning device is embodied as an electronically controllable means and/or has an alignment bar or a lateral stop, it is possible in a favorable fashion for the residence time of the rails on the roller table to be reduced, for the temperature control to be improved, and, optionally, for the output of the installation to be increased. Moreover, this position is particularly well suited for a so-called xe2x80x9chead downxe2x80x9d vertical positioning of the rail by means of the manipulators.
If, as may be provided in one embodiment of the invention, the liquid cooling devices are formed as submersion basins that have horizontally and vertically oriented stops acting on the bottom and, optionally, laterally for leveling and aligning the rolling stock, it is possible, in particular in the case of the cooling of parts of the cross section of a rail, for a highly consistent cooling and distribution of hardness to be achieved over its length, which helps to ensure the quality of the product.
It is advantageous for consistent and good use properties if holding-down means for the rolling stock, in particular for a rail, are provided in the device, with which means the rolling stock/rail can be pressed down against the leveling stops in the submersion basin during cooling because this can effectively prevent a bending caused by the cooling and keep the respective local cooling of the surface completely constant.
Particular economic advantages are provided by using the device described above for hardening at least the head of rails having a length of greater than 50 m and subsequent cooling to room temperature at a pass-through time of a rail through the hardening device that exceeds the supply frequency because large increases in performance are possible at comparably low investment costs.

Device for tempering rolled stock of great length


A semiconductor laser (22) with a semiconductor substrate (11), a laser layer (13) arranged on the semiconductor substrate, a waveguide ridge (15) arranged at a distance from the laser layer, and a strip-shaped lattice structure (23) arranged in parallel to the laser layer is disclosed. The lattice structure (23) includes two structural regions (24, 25) which are arranged on both sides of the waveguide ridge (15) and are formed at a distance from the laser layer (13) above the laser layer (13). A process for the production of such a semiconductor laser is also disclosed.

The present invention relates to a semiconductor laser with a semiconductor substrate, a laser layer arranged on the semiconductor substrate, a waveguide ridge arranged at a distance from the laser layer, and a strip-shaped lattice structure arranged in parallel to the laser layer. The present invention further relates to a process for the production of such a semiconductor laser.
Known semiconductor lasers of the type defined in the introduction, also referred to in the art as so-called DFB (distributed feedback) laser diodes, have a lattice structure which extends through the laser layer and which facilitates the construction of a monomode laser diode in which, in contrast to multi-mode laser diodes, laser radiation with one specified laser mode is emitted and other modes are suppressed by the lattice structure. The production of the DFB laser diodes constructed in the known manner proves extremely costly, in particular due to the production and test process employed and the high reject quota associated therewith. For the production of the known DFB laser diodes on the basis of a wafer on a semiconductor substrate base, epitaxy is used to form the structure of the semiconductor wafer on the semiconductor substrate. For the formation of the lattice structure in the laser layer, when approximately half the layer height of the epitaxial structure has been reached the epitaxial growth is interrupted and the lattice structure is introduced in a lithographic- and removal process. Then the epitaxial growth is continued. The interruption of the epitaxy in the formation of the laser layer and the following overgrowth of the lattice structure introduced into the half-layer induces defects in the laser layer which disadvantageously affect the properties of the laser layers and possibly manifest in a higher current consumption or a reduced life of the laser diodes.
As a result of the mutual influences between the laser layer and the lattice structure formed in the laser layer in terms of the amplification properties of the semiconductor laser wafer, the properties of a semiconductor laser wafer produced in the described way cannot be predetermined in an exact manner. As the properties of the semiconductor laser wafer cannot be determined until after the conclusion of the epitaxial growth and the complete formation of the laser layer in the test operation, the amplification spectrum of the semiconductor laser wafer also cannot be determined until after the formation of the lattice structure in the laser layer, with the result that the lattice structure cannot be accurately adapted to the amplification spectrum of the laser layers and consequently the known DFB laser diodes also cannot be produced in a precise manner in accordance with predefined specifications relating to the desired laser mode or the desired wavelength. Rather, the structure of the known DFB laser diodes described in the foregoing requires a production process in which different lattice structures must be formed in the laser layer of a semiconductor laser wafer in order that, by checking the laser diodes separated from the semiconductor laser wafer, precisely those laser diodes which emit the desired laser mode with the desired wavelength can be retrospectively determined. It is thus apparent that the structural design of the known DFB laser diodes necessitates the production of a plurality of laser diodes in order that the laser diodes suitable for the intended application, i.e. those laser diodes which emit a laser radiation with the desired wavelength, can be selected from this plurality of laser diodes by testing of their laser properties.
The primary object of the present invention is to propose a laser diode with a structure which facilitates a simple and reproducible manufacture of laser diodes with a defined wavelength. It is also an object of the present invention to propose a DFB laser diode with improved power output. A further object of the present invention is to propose a process particularly suitable for the production of a DFB laser diode according to the invention.
According to the invention, a semiconductor laser is provided with a semiconductor substrate. A laser layer is arranged on the semiconductor substrate. A waveguide ridge is arranged at a distance from the laser layer, and a strip-shaped lattice or grating structure is arranged in parallel to the laser layer. The lattice structure includes two structural regions which are arranged on both sides of the waveguide ridge and are formed at a distance from the laser layer above the laser layer.
An embodiment of the invention provides a DFB laser diode with a lattice structure produced following the conclusion of the epitaxial growth of the laser layer for completion of the semiconductor laser wafer and following the formation of the waveguide ridge. By virtue of this structurally required, subsequent production of the lattice structure it is possible to determine the individual amplification spectrum of the laser layer and semiconductor laser wafer before the production of the lattice structure in order then, by selective predefinitions of the parameters of the lattice structure, to be able to subsequently produce the desired laser profile in an exact manner and thus to be able to reproducibly manufacture DFB laser diodes with a precisely defined wavelength or laser mode.
The structural design according to the invention also facilitates an undisturbed, continuous formation of the laser layer in the epitaxial process so that unnecessary defects, which can impair the power output characteristic of the laser layer or the DFB laser diode, do not arise at all. The arrangement of the lattice structure at a distance from the active laser layer also prevents the subsequent impairment of the laser layer. The lattice structure modulates periodically the losses and the refractive power for light propagating through the laser. In this way the DFB laser diode according to the invention facilitates a complex coupling of the laser radiation with the lattice structure with lateral modulation of the real- and imaginary parts of the refractive index. Laser diodes according to the invention therefore have a high degree of insensitivity to back-reflections, which enables them to be used without an optical isolator, for example in applications for glass fiber transmission.
To permit the precisest possible setting of the distance or relative position between the lattice structure and the active laser layer of the DFB laser diode in the production of the DFB laser diode, the lattice structure can be arranged on a barrier layer arranged in parallel to the laser layer.
If a metal, for example chromium, aluminum, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, tin, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, thallium, lead, bismuth, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and alloys thereof is used to form the lattice structure, the advantageous effects described in the foregoing can be achieved to a particularly comprehensive extent. Irrespectively of the material selected to construct the lattice structure, the lattice structure can also be formed by material removal, thus not only by material application.
It proves particularly advantageous for the structural regions of the lattice structure to be arranged adjacent to sides of the waveguide ridge and for the width of the waveguide ridge to be dimensioned such that base points of the sides are located in the peripheral region of the radiation emitted from the active zone of the laser layer. This ensures that the amplification power of the laser is influenced to the least extent possible by the lattice structure and in particular ensures effective coupling between the laser radiation and the lattice structure.
In order to improve the electrical injection the metallic lattice structure is placed on a thin insulator layer (e.g. native or artificial oxide). The insulator layer should be chosen in such a way that the refractive index is closer to that of the semiconductor and that the insulation is obtained a small thickness (typically a few nanometers). This layer is also used to suppress a potential penetration of the grating material into the semiconductor material of the laser layers and therefore serves as a barrier layer too.
For the optimization of the electrical injection surface and the effects of the lattice structure, it also proves advantageous for the sides of the waveguide ridge to be arranged substantially at right angles to the plane in which the lattice structure extends, within the accuracy attainable by the manufacturing process.
In a process according to the invention, on the basis of a semiconductor substrate a complete semiconductor laser structure is produced in an epitaxial process with the subsequent formation of a waveguide ridge by subjecting the semiconductor laser structure to a material removal process to form carrier surfaces arranged on both sides of the waveguide ridge and subsequent application of a lattice structure to the carrier surfaces.
Irrespectively of the material selected to form the lattice structure, the lattice structure can also be produced by material removal, thus not only by material application.
The processes according to the invention described in the foregoing thus facilitate the production of functional laser diodes in a first process phase, thereby facilitating the precise checking and determination of the electrical and optical properties, thus for example determination of the individual amplification spectrum of the semiconductor wafer used for the laser fabrication. Only thereafter in a second process phase, by the formation of lattice structures alongside the waveguide ridge with defined parameters, are the originally multi-mode laser diodes converted into monomode DFB laser diodes with properties in each case defined as a function of the parameters of the lattice structures.
In the event that the lattice structure is produced by the application of a lattice structure to the carrier surfaces, the use of a lithographic process, in particular the use of an electron beam lithographic process with subsequent metallization of the lithographic structure, proves particularly advantageous.
A variant of the production process which is particularly advantageous from the economic standpoint is possible if, for the production of a plurality of DFB laser diodes with different properties, a semiconductor laser wafer is firstly produced by applying an epitaxial structure to a semiconductor substrate, whereupon the waveguide ridges associated with the individual laser diodes are produced in the composite wafer by forming a strip-shaped waveguide structure which is arranged on the surface of the semiconductor laser wafer and which comprises waveguide ridges extending in parallel to one another and interlying carrier surfaces. Only thereafter is the semiconductor laser wafer divided up into separate semiconductor laser chip units, whereby the properties associated with the individual laser diodes are then precisely defined by the application or implantation of a lattice structure with corresponding structural parameters on the surface of a selected number of the laser diodes.
It is thus possible for the laser diodes which have been produced in the composite wafer and are already provided with the waveguide ridge to be used as basic laser diodes or xe2x80x9cunfinishedxe2x80x9d laser diodes with defined electrical and optical properties whereupon, from this reservoir of identically formed basic laser diodes, the required number of laser diodes can then be selected and, by the application or implantation of defined lattice structures, the desired number of monomode DFB laser diodes with precisely defined optical and electrical properties can be produced substantially without rejects.
In the following the construction of an embodiment of a DFB laser diode according to the invention and a possible process for the production thereof will be explained in detail making reference to the drawing.

Semiconductor laser with a lattice structure


The present invention relates to an improved casting process of mass producing complete lightweight cementitious house walls. More specifically, the invention relates to the manner in which thin cementitious skins are separately cast on either face of the wall against a sub-assembly of thick panels of insulation material shaped and located in a manner to control the movement of displaced cementitious fluid so that the exposed top and bottom chords of small vertical structural trusses, sandwiched between these the panels of insulation and other perimeter reinforcing members are encased with the least amount of cementitious material. The size and strength of each wall component can be varied to achieve the specific characteristics of the wall. Smooth or textured faces in the casting beds reproduce whatever profiles are of required on the finished walls. Accurate window and door openings are cast in such a manner as to eliminate the need for trim. These completed wall panels enable the rapid assembly of many houses, with factory controlled quality and cost controls.

The present invention relates to an improved method of progressively and horizontally casting lightweight sandwich panels to create house wall panels.
Conventional house construction traditionally consists of obtaining many small components from many sources and physically assembling these many components in a predetermined sequence, usually out in the prevailing weather conditions with skills of many different tradesmen divided up into many sub-contracts. Supervision is infrequent, consequently the quality of the finished house is largely determined by the skills and integrity of each of the tradesmen. These are very inefficient methods of assembling any product, especially products as expensive and complex as large housing projects.
The selection of house construction materials has evolved slowly and usually combines the least expensive acceptable materials with the skills of available tradesmen. The building industry has focused on establishing standards for each component, for example framing lumber, siding, insulation, The size of each of these components is standardized in order to control costs and reduce waste.
There is a great need to for a simple method of combining all of these components into one product and manufacturing this product on a mass production basis, creating houses that are more durable, much easier to assemble, yet retain the appearance of a typical house.
One such invention, U.S. Pat. No. 5,697,189 granted to John and Andrew Miller on Dec. 16 1997 describes a wall suitable for casting in a mass production process.
This specific patent discloses a type of cementitious wall with blocks of insulative material each completely surrounded by a monolithically poured cementitious material with a continuous upper track and a projecting floor connection means. Other claims include vertical cementitious ribs reinforced with vertical steel reinforcing bars, accurately cast window and door openings. The subsequent assembly of these completed walls on site simplifies house construction
The actual method of assembling and casting this said wall is not described in detail, however anyone skilled in the art of creating very thin cementitious skins on a large sandwich wall panel, with a central core of expanded polystyrene, will realize the necessity to progressively cast this wall in a horizontal position. The first thin skin is applied evenly to a horizontal form tray, then an assembly of expanded polystyrene panels and steel reinforcing is applied to this first fluid cementitious skin, followed by the application of second fluid cementitious skin applied over the upper face. This application of this second cementitious skin includes filling the voids between the expanded polystyrene panels and completely encasing each panel. This second skin also provides a method of bonding both skins together and encasing the steel reinforcing on both faces of the wall. The face of the first skin cast against the form tray reproduces whatever texture is on the face of this form tray. The face of the second exposed skin is mechanically finished with trowels, usually with a smooth finish.
The manufacture of this particular product as described in this existing patent has a number of inherent manufacturing and design problems. The use of monolithically poured cementitious material as a means of connecting both faces of the wall panel together at the vertical ribs. In addition the structural design of the rib necessitates of total encasement of these vertical steel reinforcing elements. More specific details are as follows;
The first disadvantage of this existing patent is the necessity to and inability of ensuring that voids do not occur in the central portion of these ribs. Considerable difficulty is experienced in ensuring that the fiber filled cementitious fluid continuously flows into the narrow joints between blocks of insulative material and upper steel reinforcing bar without creating air pockets. Voids in the rib area greatly impairs the structural integrity of the entire wall panel.
Another disadvantage of this existing patent is the necessity to and inability of ensuring a continuous bond along the wet joint line between the first wet lower skin of the wall panel and the second skin the cementitious fluid designed to flow between the blocks of insulation and bond both sides of the panel together with cementitious fluid. Failure to continuously bond both sides of the panel together in this rib area also greatly impairs the structural integrity of the entire wall panel.
Another disadvantage is the reliance on the tensile strength of the fibers in the cementitious rib area providing the only tensile connection between the steel reinforcing bars on either face of the panel. It was not possible to achieve the full potential of the strength of the steel reinforcing bars in solid ribs and the strength of the fibers proved to be inconsistent
Another disadvantage is that the wall as described in this existing patent is limited in its application to single level houses with solid concrete floors, cast on the ground. There is no connection provision for walls for upper floors and no provision for floors above ground or between floors for any other type of construction.
Another disadvantage is that the projecting connecting bars at the bottom of the wall protrude beyond the wall face, creating difficulties in the manufacturing process and difficulties with temporary storage when panels are stacked against each other.
Another disadvantage is the method of obtaining a smooth finish on the upper face of the second skin of cementitious fluid. It is necessary to this wait for the surface of the second skin of the cementitious material to partially solidify and then repeatedly trowel this surface as it hardens. The timing of this solidifying process is unpredictable and the finishing procedure is a time consuming process, not suitable for an industrial process. The trowelled upper surface results in an undulating imperfect surface, in contrast to the precision of the face of the first skin cast down against the surface of the form tray.
The primary object of this invention is to eliminate the foregoing manufacturing and structural flaws found in this prior patent, and although this present invention retains the external appearance of the wall as described in the prior patent, the method of manufacture and the technical description of this new invention is very different.
One improvement to the prior patent is the use of a vertical welded steel truss in the vertical ribs between the edges of the beveled insulation blocks that replaces the individual vertical steel reinforcing bars on either face of the wall. These rib trusses are constructed out of small diameter deformed steel chords, electrically welded to interconnecting small diameter steel diagonal bracing members. These trusses are ultimately provided with lateral stiffness by both locally thickened cementitious skins, with the truss ends restrained in solid cementitious material at the top and bottom of the wall. Both chords of these trusses initially remain fully exposed and are subsequently encased with the cementitious fluid.
Another improvement to the prior patent is the use of the many interconnecting diagonal bracing members of the vertical trusses as the means of connecting both independent skins of the wall together. The small diameter steel diagonal bracing members of these trusses are sandwiched between the sides of the beveled blocks of insulation. This eliminates the use of wet cementitious material of the second skin to bond to the wet face of the first skin and the use of the fiber in the cementitious material in the central rib area providing the tensile connection between the steel reinforcing bars on either face of the panel.
Another improvement is encasing the lower chord of these rib trusses with cementitious fluid of the first skin by submersing the face of the subassembly of insulating panels and trusses until the lower chord of the trusses are fully encased in cementitious fluid. This also eliminates the need to encase the reinforcing steel on the lower first face with cementitious fluid from the second skin.
Another improvement is the method of controlling the thickness of the first skin by forcing down this internal subassembly down to a predetermined position, with the excess cementitious fluid being displaced to ends of the insulation panels.
Another improvement is casting the second face of the wall panel by waiting until the first skin has solidified then rotating this entire first assembly into a second wet cementitious skin on a separate casting bed in a similar manner to casting the first skin. This provides an excellent predictable finish to the second skin. This avoids waiting for the surface of the second skin to solidify and eliminates all surface trowelling, greatly improving the quality of this second face of the wall.
Another improvement is providing the bottom of the wall with an temporary aligning and connecting device that ultimately provides a permanent connection to the structure below this wall, that does not protrude beyond the wall face, so that walls can be temporarily stacked against each other during handling and shipping.
Another improvement is providing the top of the wall with recesses to accommodate the permanent attachments to the top of this wall, including floors above ground level, second floors, walls on walls, and roof structures including preassembled roofs. A continuous track to accommodate temporary handling devices and other permanent connections is desirable but not essential.
During the making and testing experimental panels it was discovered that it was not necessary to encase the diagonal bracing members of the rib trusses in concrete and only necessary to encase the top and bottom chord of these rib trusses in concrete skins. This in turn isolated the cementitious skins on either face of the panel from each other and improved the value of the insulation panels in this wall.
The specific design of this sandwich wall panel is substantially different from the prior art. The panel manufacturing procedure is greatly improved by avoiding the use of cementitious material in the rib area. The cast surface finish on the second wall face is superior. The strength of this panel increased and the weight of this wall panel reduced The casting of separate skins allows the use of different types of cementitious materials, such as fire rated or high impact skin on one or more wall faces.

Method of assembling lightweight sandwich wall panel


Apparatus and method for reading optical discs containing information in the form of tracks of high-spacial-frequency, phase-modulating marks (e.g., depressions or pits) includes means for directing the zero and one first diffraction order of read light returned from the scanned track into superimposed relation on a photodetector and means for predeterminedly masking a portion of the zero diffraction order light so that its magnitude is more equal to that of the first diffraction order light.

1. Field of the Invention
The present invention relates to apparatus and methods for photo-electrically detecting (i.e., reading) high density information from optical storage media such as optical discs, and more specifically to such apparatus and methods particularly adapted to detect phase differences imparted to reading light by recorded tracks on the storage media.
2. Description of the Prior Art
One currently preferred approach to high density optical information storage is to record tracks of minute (usually on the order of a micron or less in size) marks on the storage medium. The most popular format is for such storage medium to be of disc shape and for the tracks to be spiral or concentric so that optical scanning can be effected by rotating the disc relative to a small focused spot of read-light (e.g., from a laser). However, there are various other equivalent formats to disc shape and reference herein to optical discs is intended to include all such equivalent optical storage medium.
In general, there are two kinds of systems for storing and retrieving information on optical discs, distinguished primarily by the construction of the recording medium. These can be termed amplitude systems (wherein a read signal is obtained primarily from the difference in amplitude of read light reflected from marked and non-marked portions of the optical disc) and phase systems (wherein a read signal is obtained primarily from the difference in phase of light reflected from marked and non-marked portions of the optical disc). Although the present invention can be utilized with advantage in reading both amplitude and phase systems, it is particularly useful for reading optical discs of the phase system kind. The record tracks of this kind of optical disc are usually comprised of discrete pits or indentations of predetermined depth below the intervening non-pitted track portions. Land portions, of height equal to the non-pitted track portions are located between adjacent tracks to prevent cross-talk. Heretofore, read-out of phase system optical discs has most commonly been practiced by one of two approaches, which can be termed "central aperture" and "split-detector".
In central aperture reading of optical discs, a reading spot, of effective width greater than the track width, is located in a centered relation along a track so that pitted and non-pitted portions of the track scan therepast at a rate determined by the disc rotation speed. The photo-electric detector is located in the center (i.e., on the axis) of the light beam reflected from the scanned disc and receives all such reflected light that is collected by the read-out objective (e.g., by focusing such collected light onto the detector). The pitted portions of the track are of a predetermined optical depth (.lambda./4 with respect to the reading light wavelength .pi.) so that a .lambda./2 or .pi. phase difference will be imparted to light rays respectively reflected from pitted and non-pitted regions. The peak-to-peak detector signal for the central aperture system is obtained between a maximum constructive interference condition (when light passing to the photodetector is maximally from non-pitted track portions and adjacent lands) and the maximum destructive interference condition (when light passing to the photodetector contains its largest proportion of light from pitted portions that destructively interfers with light from adjacent lands). This technique is described in more detail in an article entitled The Optical Scanning System of the Philips "VLP" Record Player, at pages 186-189 of Volume 33 of the Philips Technical Review, No. 7, 1973.
One example of the "split-detection" approach for reading phase difference information from optical discs is disclosed in U.S. Pat. No. 4,065,786. That patent indicates an objective to utilize a read-spot of lesser cross track dimension (width) than the central aperture approach, so as to minimize the likelihood of cross-talk between adjacent information tracks. In order to utilize such a reduced read-spot width and still maintain the high resolution obtainable with the central aperture detection, the patent suggests that two light detectors be located in a non-centered position with respect to the central axis of the light beam returned from the interrogated track on the disc. Specifically, the light detectors are located respectively to respond to the light intensity in two overlap zones of the light retroreflected from the disc, viz., the overlaps of the zero diffraction order beams returned from the disc with each of the + and - first diffraction order beams returned from the disc. The outputs of the two light detectors are combined (subtracted) to double the amplitude of the recovered signal.
Besides reducing the likelihood of cross-talk, the split detection approach provides an additional potential advantage over the central aperture detection approach. Specifically, split detection provides a maximum signal when the phase of light reflected from pitted and non-pitted portions of the disc differs by .pi./2, rather than .pi. as in central aperture detection. Thus, in systems in which phase shift depends on pit depth, optical depths of only .lambda./8 can be used with split detection (in contrast to the .lambda./4 optical pit depths that optimize central aperture detection); and the use of "shallower" pits can be very advantageous for real-time recording approaches where desired pit depth dictates the laser recording power and/or speed of operation.
However, split detection is not without disadvantages. As mentioned, that approach requires precise placement of two detectors with respect to the two overlap zones between zero and first diffraction order light beams. In addition, the detector must be placed in a plane in space in which such overlap zones are accessible, e.g., at a plane that is image conjugate to the exit pupil of the read-out objective, and only light in the overlap regions contributes to the signal recovered from the disc. In general, the amplitudes of the interfering zero and first order beams are not equal in the regions where these beams overlap; and the depth of modulation of the signal resulting from the mutual interference of those beams is limited by this fact. Moreover, since the signal generated by the zero/plus first order overlap is 180.degree. out of phase with that generated by the zero/minus first order overlap, two detectors must be used to obtain maximum signal depth of modulation; and these detectors cannot be at the focus of a field lens. This situation complicates system alignement.