Radar apparatus in which output RF signals are modulated on an optical signal prior to transmission. Incoming optical echo signals are converted into RF signals using a detector. The original functionality of the radar apparatus is to a large extend retained, including the Doppler processing. The target radar cross section is determined by the wavelength of the optical signal.

The invention relates to a detection arrangement for the remote detection of targets, comprising a radar signal generator for generating coded RF radar signals, a transmitter unit controlled by the coded RF radar signals, a radar receiver unit and a video processor connected to the radar receiver unit.
A detection arrangement of this type implemented as a radar apparatus is known in many versions. The drawback of a radar apparatus is that the emitted RF waves can be easily detected by means of ESM receivers which reveal the location and usually also the identity of the transmitting object. Besides, once detected, the radar apparatus may be subjected to deliberate interference.
The present invention obviates this drawback and is characterized in that the transmitter unit is designed to transmit optical signals modulated by the coded RF radar signals and that an optical detector is positioned in front of the radar receiver unit for converting echo signals from the transmitted optical signals into coded RF radar signals, possibly containing target information.
The optical signal consequently acts as carrier for the RF radar signals and the original functionality of the radar apparatus is to a large extent retained.
An advantageous embodiment of the invention, which obviates the necessity of using coherent optical signals is characterized in that the transmitter unit is designed for the amplitude modulation of the optical signals.
An incidental advantage of this embodiment is that the optical detector can be implemented as a relatively low-cost envelope detector.
A detection arrangement according to the invention is eminently suitable for Doppler processing, in which it is not the Doppler shift of the optical signals that is utilized, but the Doppler shift of the coded RF radar signals. A further fact is that a target""s radar cross-section is mainly determined by the wavelength of the optical signals. This provides an additional degree of freedom; if, for instance, the dispersion of a gas cloud is to be followed, the RF frequency should be selected such that a good Doppler processing is ensured and optical signals that provide a good reflection on the gas cloud.
A further advantageous embodiment of the invention is characterized in that the signal generator is designed to generate pulse bursts. The use of pulse bursts in radar is well-known, just like the fact that this yields an optimal Doppler processing. The disadvantage of radar is that a burst can easily be jammed by a repeater jammer, which does not apply to the detection arrangement according to the invention, because optical repeater jammers are not available.
A further advantageous embodiment of the invention, which makes optimal use of the pulse bursts, is characterized in that the video processor includes a Doppler processor of the moving target indication (MTI) or moving target detection (MTD) type to enable the detection of moving targets.
A further advantageous embodiment of the invention is characterized in that the signal generator is designed to generate FMCW radar signals and that the receiver comprises a mixer stage for combining the echo signals detected by the optical detector with signals generated by the signal generator. The detection arrangement will then incorporate all the advantages normally inherent in an FMCW radar apparatus, but is virtually undetectable. Besides, the problem involving the isolation between the transmitter unit and the receiver unit can be solved more easily, because the actual radar beam is then generated by means of optical components.
A further advantageous embodiment of the invention is characterized in that the optical detector incorporates at least two optical diodes for producing RF monopulse signals and that the radar receiver unit is a monopulse receiver. Thus, the direction of a target can be determined on the basis of the phase or amplitude difference between the RF radar signals. In this embodiment, with two diodes disposed in the horizontal plane, the invention can be used to advantage as a collision avoidance radar for vehicles.
A further advantageous embodiment of the invention is characterized in that the optical detector incorporates four optical diodes for producing an RF sum signal, an RF xcex94-azimuth difference signal and an RF xcex94-elevation difference signal. In this embodiment, the detection arrangement is equivalent to a monopulse fire control radar well-known in the art, on the understanding that the arrangement is now capable of tracking an aircraft without the aircraft""s lock-on warning system being activated.
A further advantageous embodiment of the invention is characterized in that the detection arrangement is designed for underwater applications. This is feasible because a wavelength of the optical signals can be chosen such that a good penetration depth can be attained. This makes it possible to detect the approach of, for instance, torpedoes on the basis of their Doppler velocity. Mounted underneath a helicopter for instance, the detection arrangement would make it possible to locate objects below the water surface and, for instance, to track a submarine on the basis of its Doppler velocity.
As the general radar equation is in fact relevant to the detection arrangement according to the invention, an increase of the effective range can be realized by either increasing the transmitted power or by enhancing the receiver unit sensitivity. An advantageous embodiment of the invention is characterized in that a light amplifier is positioned in front of the optical detector so that the transmitted power can be kept at a relatively low level.


A control panel assembly having a plurality of buttons located in a bezel and supported by a switch mat. A bezel and/or button is formed using a vacuum forming technique and has a transparent inner surface layer and a middle translucent color layer and an opaque outer surface layer. A portion of the opaque outer surface layer is removed to define a desired indicia on an outer surface of the bezel or button. In addition, the bezel or button can be backlit to allow visibility in low light conditions. A method of making a control panel component, such as a bezel or button, is also disclosed.

The present invention relates to control panel assemblies and a method of making components such as buttons and bezels for use in control panels. More particularly, the present invention is directed to backlit control panel assemblies having indicia that is visible during daytime and nighttime usage.
Control panels having backlit buttons are known for use in the interior of automotive vehicles, including radio control buttons and door lock buttons. The purpose of backlit buttons is to allow a user to see the button and its function even in low light situations. Typically, a radio button will have a graphic image or other indicia to indicate a particular purpose. For example, the word xe2x80x9cscanxe2x80x9d or a number such as xe2x80x9c3xe2x80x9d is provided on a button to indicate that button""s purpose. One known button is made by injection molding a clear plastic material in the form of a button. The button is then painted with a layer of white paint and dried by an oven or other conventional technique. Next, a layer of black paint is applied over the white paint and is subsequently dried. A laser is used to etch away a desired portion of the black paint to form a white graphic image. In a low light situation, the button is illuminated from behind such that the graphic image is visible to a user through the white paint layer.
Another known method of making buttons for a control panel involves providing a transparent member with a black layer on one side and vacuum forming the transparent member with the black layer into a desired shape. Thereafter, a laser passes through the transparent member and etches away a desired portion of the black layer to form a graphic image. Next, a daytime color is pad printed over the black layer side and dried in an oven followed by pad printing a nighttime color on top of the daytime color and oven drying the nighttime color. Finally, the subassembly is placed in an injection molding apparatus and an interior recess of the button is filled with resin during injection molding to make the button more rigid.
It is further known to provide control panels having backlit buttons on a switch pad for resilient switching action. However, the known buttons have a generally flat upper surface to be sure that light can fully reach and evenly illuminate a graphic image on the button. In addition, the graphic image may be partially blocked from illuminating light by part of the switch mat because of the way the button rests on the switch mat. Thus, the graphic image will not be fully visible when backlit.
The present invention is directed to a control panel assembly and to individual components of that assembly, including, a bezel containing at least one opening and at least one button associated with the bezel. The bezel and/or the button have a main body vacuum formed into a predetermined shape and having an inner surface and an outer surface. The main body includes coextruded first and second layers and a third layer applied to the second layer. Further, the first layer is generally transparent, the second layer is generally translucent, and the third layer is generally opaque. In addition, a resilient switch mat is associated with the at least one button and comprises a generally planar base portion with at least one generally hollow projection for contacting the button. The projection has first and second ends and inner and outer surfaces. Further, the first end of the projection includes a stepped portion for receiving a portion of the button.
Additionally, the present invention can include indicia on the outer surface of the main body of the bezel and/or button. Preferably, the indicia is laser etched into the opaque layer thereby exposing the translucent layer. The transparent first layer can have a thickness of approximately 0.040 inch. Next, the translucent second layer is a color layer and can have a thickness of approximately 0.008 inch. The opaque third layer can have a thickness of approximately 0.002 inch. Moreover, the opaque third layer is thermally bonded to the coextruded first and second layers, according to one version of the present invention. In a preferred embodiment of the present invention, the transparent first layer is an interior layer, the translucent second layer is a middle layer, and the opaque third layer is an exterior layer.
The switch mat of the present invention further includes the stepped portion having a shoulder located a predetermined distance away from the first end of the projection for limiting travel of a button relative to the projection. And, the second end of the projection is connected to the generally planar sheet. In addition, the inner surface of the projection has variable thickness that is created by at least one axial groove provided on the projection for increasing interior cross-sectional area for light to pass to the at least one button for fully illuminating any indicia thereon. Further, the projection includes corners having a cross-sectional thickness greater than an adjacent side wall portion for insuring lateral strength of the projection. One disclosed version includes the projection having a generally rectangular cross-sectional shape.
The present invention is also directed to a method of making a component of a control panel comprising the steps of: providing a first layer of material, providing a second layer of material and coextruding the first layer of material to the second layer of material. The method also includes forming the coextruded first and second layers into a predetermined shape.
Another method step of the present invention involves applying a third layer of material onto the coextruded first and second layers. The step of applying can be carried out by at least one of thermally bonding, spraying, or printing. Still further, the forming step is optionally, but preferably performed after the step of applying the third layer to improve processing and quality. More specifically, the step of forming can include vacuum forming.
The coextruding step further includes the first layer of material being generally transparent and the second layer of material being generally translucent. The forming step can include vacuum forming either a bezel, a button or both. Also, the method of the present invention includes providing indicia on the component.
Yet another method according to the present invention includes forming a component for a control panel comprising the steps of: providing a first layer of material, providing a second layer of material, coextruding the first layer of material to the second layer of material, vacuum forming the coextruded first and second layers into a predetermined shape, applying a third layer of material to the second layer, and selectively removing a portion of the third layer of material to expose a portion of the second layer for forming indicia on the component.
The present invention provides a control panel assembly and components that are more cost effective to fabricate and eliminates extra steps that are required to make previously known components. Control panel components provided in accordance with the present invention have an inner transparent layer, a middle translucent color layer, and an opaque outer surface layer. Indicia can be provided on the button or bezel using a laser etching technique that removes a predetermined portion of the opaque outer surface layer. The component can be vacuum formed from a multi-layer sheet that includes a co-extruded substrate having a generally transparent layer co-extruded with one or more translucent color layers. A thin outer opaque layer is thermally bonded to the co-extruded substrate using residual heat remaining from the co-extrusion process. Next the multi-layer sheet is vacuum formed to create a any number of components. As a result, the steps of painting multiple coats and drying each coat has been eliminated. Thus, environmental concerns associated with painting are eliminated. Further, the present invention provides a more uniform thickness to the outer opaque layer than is provided by painting. Moreover, the inner transparent layer is made sufficiently thick to provide adequate strength for the button, thereby eliminating the need to injection mold resin behind the button as in the prior art. By eliminating the injection molding step, the present invention substantially reduces tooling costs and tooling time versus known button making processes. In addition, cycle time to process the button is reduced from approximately 30 seconds to approximately 6 seconds. Therefore, costs of fabricating buttons is substantially reduced in accordance with the present invention.
The control panel assembly of the present invention further includes an elastomeric switch mat having a planar sheet portion with a plurality of projections that correspond to locations of buttons. Each projection has first and second ends and are generally hollow having side walls with inner and outer surfaces. The switch mat covers a printed circuit board having a light source. A projection channels light from the light source up to the button mounted thereon and allows the button to be backlit. Preferably, a stepped portion is provided at the first end of the projection for receiving the button. A shoulder is provided to act as a stop which limits the travel of the button onto the projection and spaces the inner surface layer of the button away from the first end of the projection to enable the light source to fully illuminate any indicia located on the button. Moreover, the side walls of the projections have variable thickness and include axial grooves to allow light to reach the inner surface layer of the button. The present invention therefore allows buttons having greater arcuately shaped or contoured top surfaces to be used without the drawback of having idicia being blocked off from light by a side wall of the projection.
As a result, the present invention provides a control panel assembly such as those used on the interior of automotive vehicles that are cost effective, have improved feel to the user and have indicia that will not be rubbed off during its service life.

Control panel assembly and method of making same


The invention relates to chiral compounds of formula I,

The invention relates to chiral compounds with a high helical twisting power, to liquid crystal mixtures comprising them, and to chiral linear or crosslinked liquid crystal polymers obtained from a polymerizable mixture comprising one or more chiral compounds. The invention further relates to the use of the chiral compounds and the mixtures and polymers obtained thereof in liquid crystal displays, active and passive optical elements, adhesives, synthetic resins with anisotropic mechanical properties, cosmetic and pharmaceutical compositions, diagnostics, liquid crystal pigments, for decorative and security applications, nonlinear optics, optical information storage or as chiral dopants.
For many applications it is desirable to have LC (Liquid Crystal) mixtures with a twisted phase. Among these are e.g. phase-change displays, guest-host displays, passive and active matrix TN and STN displays like AMD-TN, ferroelectric displays and cholesteric displays like SSCT (surface stabilized cholesteric texture) or PSCT (polymer stabilized cholesteric texture) displays, including displays with temperature compensated characteristics, e.g. by appropriate selection of the cholesteric compounds according to the invention either alone or in combination with further chiral dopants. For these applications it is advantageous to have available a chiral dopant with a high HTP (Helical Twisting Power) in order to reduce the amount of dopant needed to induce the desired pitch.
For some applications it is desired to have LC mixtures that exhibit a strong helical twist and thereby a short pitch length. For example in liquid crystal mixtures that are used in selectively reflecting cholesteric displays like SSCT or PSCT, the pitch has to be selected such that the maximum of the wavelength reflected by the cholesteric helix is in the range of visible light. Another possible application is in polymer films with a chiral liquid crystal phase for optical elements, such as cholesteric broadband polarizers or retardation films.
In a cholesteric LC material, the pitch p of the molecular helix in the first approximation, which is sufficient for most practical applications, is inversely proportional to the concentration c of the chiral dopant in the liquid crystal host mixture according to equation (1):
The proportionality factor is the helical twisting power (HTP) of the chiral dopant.
As can be seen from equation (1), a short pitch can be achieved by using high amounts of dopant or-by using a dopant with a high HTP. However, the chiral dopants of prior art often exhibit low values of the HTP, so that high amounts of dopant are needed. This is a disadvantage because chiral dopants can be used only as pure enantiomers and are therefore expensive and difficult to synthesize.
Furthermore, when using chiral dopants of prior art in high amounts, they often negatively affect the properties of the liquid crystal host mixture, e.g., the clearing point, the dielectric anisotropy AE, the viscosity, the driving voltage or the switching times.
The chiral dopants often show a high temperature dependence of the helical twisting power. When used in cholesteric mixtures this leads to a strong temperature dependence of the reflection wavelength of the mixture. This is especially disadvantageous for application in cholesteric displays, such as SSCT displays, where usually a low temperature dependence of the reflection wavelength is required.
Another disadvantage of prior art chiral compounds is that they often show low solubility in the liquid crystal host mixture, which leads to undesired crystallization at low temperatures. To overcome this disadvantage, typically two or more different chiral dopants have to be added to the host mixture. This implies higher costs and also requires additional effort for temperature compensation of the mixture because different dopants have to be selected such that their temperature coefficients of the twist compensate each other.
There is thus a considerable demand for chiral compounds with a high HTP which are easy to synthesize, can be used in low amounts, show low temperature dependence of the twisting power, e.g., for utilizing a constant reflection wavelength, do not affect the properties of the liquid crystal host mixture and show good solubility in the host mixture.
One of the first aims of the invention is providing chiral compounds having these properties, but which do not have the disadvantages of the chiral dopants of the state of the art as discussed above. Another aim of the invention is to extend the pool of chiral dopants available to the expert.
These aims and others can be achieved by providing chiral isosorbide derivatives as described below.
WO 95/16007 and WO 98/00428 disclose chiral mesogenic compounds with a high HTP based on 1,4:3,6-Dianhydro-D-sorbitol (isosorbide). However, many of these compounds do only have a limited solubility in liquid crystal host mixtures.
Chiral compounds derived from isosorbide
which are substituted unsymmetrically with two different mesogenic groups in the 2- and 5-position show a higher solubility in liquid crystal host mixtures compared to isosorbide derivatives that are substituted symmetrically with two identical mesogenic groups. Furthermore, the unsymmetrically substituted isosorbides show a remarkable difference in solubility depending on the respective position of the mesogenic groups. An isosorbide derivative with a larger mesogenic group, like a two-ring group, attached in 5-position and a smaller mesogenic group, like a one-ring group, attached in 2-position, for example, has a considerably higher solubility than its corresponding isomer where the two-ring group is attached in 2-position and the one-ring group in 5-position. This is a considerable unexpected improvement over the prior art.
One object of the present invention is chiral compounds of formula I
wherein
R1 and R2 are, independently of each other, Pxe2x80x94Spxe2x80x94X, F, Cl, Br, I, CN, SCN, SF5, or a straight chain or branched alkyl with up to 30 C atoms that is unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, and wherein one or more non-adjacent CH2 groups are optionally replaced, in each case independently from one another, by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94NR0xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOxe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94 in a manner that O and/or S atoms are not linked directly to one another,
R0 is H or alkyl with 1 to 4 C atoms,
P is a polymerizable group,
Sp is a spacer group or a single bond,
X is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94NR0xe2x80x94, xe2x80x94NR0xe2x80x94COxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94SCH2xe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond,
X1 isxe2x80x94COxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94NR0xe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94COxe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94C2H4xe2x80x94, xe2x80x94CF2xe2x80x94 or a single bond,
X2 is xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94NR0xe2x80x94, xe2x80x94COxe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94C2H4xe2x80x94, xe2x80x94CF2xe2x80x94 or a single bond,
Z1 and Z2 are independently of each other xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94Oxe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94NR0xe2x80x94, xe2x80x94NR0xe2x80x94COxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94SCH2xe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94CF2Oxe2x80x94, xe2x80x94OCF2xe2x80x94, xe2x80x94CF2Sxe2x80x94, xe2x80x94SCF2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CF2CH2xe2x80x94, xe2x80x94CH2CF2xe2x80x94, xe2x80x94CF2CF2xe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94Nxe2x95x90CHxe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94CFxe2x95x90CHxe2x80x94, xe2x80x94CHxe2x95x90CFxe2x80x94, xe2x80x94CFxe2x95x90CFxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond,
A1 and A2 are, independently of each other, an aliphatic or aromatic carbocyclic or heterocyclic group with up to 16 C atoms that optionally contains one or more fused rings and is unsubstituted, mono- or polysubstituted with L,
L is halogen or a cyano, nitro, alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 7 C atoms, wherein one or more H atoms are optionally substituted by F or Cl,
m1 is 1, 2 or 3, and
m2 is 0, 1, 2 or 3,
with the proviso that the total number of fused or unfused rings in the (Z1-A1)m1 group is larger than in the (A2-Z2)m2 group.
Another object of the invention is a liquid crystal mixture containing at least one compound of formula I.
Another object of the present invention is a polymerizable liquid crystal mixture comprising at least one compound of formula I.
Another object of the invention is a linear or crosslinked anisotropic polymer with twisted structure obtainable from a polymerizable liquid crystal mixture comprising one or more compounds of formula I.
A further object of the invention is the use of compounds of formula I or a liquid crystal mixture or anisotropic polymer film comprising them in liquid crystal displays, such as STN, TN, AMD-TN, temperature compensation, ferroelectric, guest-host, phase change or surface stabilized or polymer stabilized cholesteric texture (SSCT, PSCT) displays, in active and passive optical elements like polarizers, compensators, alignment layers, color filters or holographic elements, in adhesives, synthetic resins with anisotropic mechanical properties, cosmetic and pharmaceutical compositions, diagnostics, liquid crystal pigments, for decorative and security applications, in nonlinear optics, optical information storage or as chiral dopants.
Yet another object of the invention is a liquid crystal display comprising a liquid crystal mixture comprising at least one chiral compound of formula I.
The inventive chiral compounds bear numerous advantages, for example,
they exhibit a high HTP,
they exhibit a good solubility in liquid crystal mixtures,
when inventive compounds are used as chiral dopant in a liquid crystal mixture, due to their high solubility, higher amounts of dopant can be used to produce a high twist (=a low pitch),
due to their high HTP, lower amounts of inventive dopants are needed to achieve a high pitch, and thereby the liquid crystalline properties of the mixture are less negatively affected,
enantiomerically pure inventive chiral compounds are easy to prepare.
The inventive chiral compounds are mesogenic or even liquid crystalline, i.e., they can induce or enhance mesophase behavior, for example, in admixture with other compounds, or even exhibit one or more mesophases themselves. It is also possible that the inventive compounds show mesophase behavior only in mixtures with other compounds, or, in case of polymerizable compounds, when being (co)polymerized. Mesogenic inventive chiral compounds are especially preferred.
In formula I, Z1 adjacent to R1 and Z2 adjacent to R2 are preferably a single bond.
Preferred groups A1 and A2 in formula I are, for example, cyclopentane, 1,1,-dimethylcyclopentane, tetrahydrofuran, pyrrolidine, furan, pyrrol, thiophene, oxazole, thiazole, thiadiazole, imidazole, pyrrolidinone, cyclohexane, cyclohexene, tetrahydropyran, piperidine, tetrahydrothiopyrane, dioxane, dithiane, oxathiane, thiomorpholine, morpholine, phenylene, pyridine, pyrimidine, pyrazine, bicyclohexane, bicyclohexene, cyclohexane-1,4-dione, bicyclo[2,2,2]octylene, cyclohexenone, indane, naphthalene, decahydronaphthalene, 1,2,3,4-tetrahydronaphthalene, anthracene and phenanthrene.
Particularly preferably A1 and A2 are 1,4-phenylene in which one or more CH groups may be replaced by N, 1,4-cyclohexylene in which one or two non-adjacent CH2 groups may be replaced by O and/or S, 1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo-(2,2,2)-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl and indane-2,5-diyl, it being possible for all these groups to be unsubstituted, mono- or polysubstituted by L as defined above.
Especially preferred are compounds of formula I wherein the groups (Z1-A1)m1 and (A2-Z2)m2 contain only monocyclic groups A1 and A2, with m1 greater than m2.
Of these preferred compounds, especially preferred are those wherein A1 and A2 are selected from aliphatic and aromatic six-membered carbocycles that may also contain one or more hetero atoms, very preferably from 1,4-phenylene in which, in addition, one or more CH groups may be replaced by N, 1,4-cyclohexylene in which, in addition, one or two non-adjacent CH2 groups may be replaced by O and/or S, 1,3-dioxolane-4,5-diyl, 1,4-cyclohexenylene and piperidine-1,4-diyl, it being possible for all these groups to be unsubstituted, mono- or polysubstituted with L as defined in formula I.
A group of preferred groups (Z1-A1)m1 and (A2-Z2)m2 is listed below. For reasons of simplicity, Phe in these groups is 1,4-phenylene which may be also substituted by one or more L groups as defined in formula I, and Cyc is 1,4-cyclohexylene. The following list of groups is preferred as well as their mirror images
-Phe-xe2x80x83xe2x80x83II-1
-Cyc-xe2x80x83xe2x80x83II-2
-Phe-Z-Phe-xe2x80x83xe2x80x83II-3
-Phe-Z-Cyc-xe2x80x83xe2x80x83II-4
-Cyc-Z-Cyc-xe2x80x83xe2x80x83II-5
-Phe-Z-Phe-Z-Phe-xe2x80x83xe2x80x83II-6
-Phe-Z-Phe-Z-Cyc-xe2x80x83xe2x80x83II-7
-Phe-Z-Cyc-Z-Phe-xe2x80x83xe2x80x83II-8
-Cyc-Z-Phe-Z-Cyc-xe2x80x83xe2x80x83II-9
-Cyc-Z-Cyc-Z-Phe-xe2x80x83xe2x80x83II-10
-Cyc-Z-Cyc-Z-Cyc-xe2x80x83xe2x80x83II-11
Especially preferred are formulae II-1, II-2, II-3, II-4 and II-5. Further preferred are groups (Z1-A1)m1 and (A2-Z2)m2 comprise at least one Phe group that is substituted with one or two L groups, preferably in the 2- and/or 3-position, and L is F, Cl, CH3, OCH3, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F or CN.
Further preferred are compounds of formula I, wherein
m1 is 1 and m2 is 0 or 1.
m1 is 2 and m2 is 1.
X1 and X2 are xe2x80x94COxe2x80x94.
Z1 and Z2 are independently of each other xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94 or a single bond.
R1 and/or R2 is a polymerizable Pxe2x80x94Spxe2x80x94X group.
R1 and R2 are straight chain or branched alkyl or alkoxy with 1 to 12 C atoms.
L is F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F or OC2F5.
A1 and A2 are, independently of each other, trans-1,4-cyclohexylene or 1,4-phenylene, the latter being unsubstituted or substituted with up to 4, preferably 1 or 2 L groups, preferably in the 3- and/or 5-position or in the 2- and/or 3-position, with L being preferably F, C1, CH3, OCH3, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F or CN.
A1 and A2 are unsubstituted 1,4-phenylene.
L is preferably F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F, OC2F5, in particular F, Cl, CN, CH3, CHF2, C2H5, OCH3, OCHF2, CF3 or OCF3, most preferably F, CH3, CF3, OCH3, OCHF2 or OCF3.
If R1 or R2 in formula I is an alkyl or alkoxy radical, i.e. where the terminal CH2 group is replaced by xe2x80x94Oxe2x80x94, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.
Oxaalkyl, i.e., where one CH2 group is replaced by xe2x80x94Oxe2x80x94, is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-oxadecyl, for example.
Halogen is preferably F or Cl.
R1 or R2 in formula I can be a polar or a non-polar group. In case of a polar group, it is CN, SF5, halogen, OCH3, SCN, COR5, COOR5, or a mono-, oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R5 is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferred polar groups are F, Cl, CN, OCH3, COCH3, COC2H5, COOCH3, COOC2H5, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, C2F5 and OC2F5, in particular F, Cl, CN, CF3, OCHF2 and OCF3. In case of a non-polar group, it is preferably alkyl with up to 15 C atoms or alkoxy with 2 to 15 C atoms.
R1 or R2 in formula I can be an achiral or a chiral group. In case of a chiral group it is preferably of formula III:
wherein
Q1 is an alkylene or alkylene-oxy group with 1 to 9 C atoms or a single bond,
Q2 is an alkyl or alkoxy group with 1 to 10 C atoms which may be unsubstituted, mono- or polysubstituted by F, Cl, Br or CN, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94N(CH3)xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOxe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94COxe2x80x94 or xe2x80x94COxe2x80x94Sxe2x80x94 in such a manner that oxygen atoms are not linked directly to one another,
Q3 is F, Cl, Br, CN or an alkyl or alkoxy group as defined for Q2, but being different from Q2.
In case Q1 in formula III is an alkylene-oxy group, the O atom is preferably adjacent to the chiral C atom.
Preferred chiral groups of formula III are 2-alkyl, 2-alkoxy, 2-methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy, 2-(2-ethin)-alkyl, 2-(2-ethin)-alkoxy, 1,1,1-trifluoro-2-alkyl and 1,1,1-trifluoro-2-alkoxy.
Particularly preferred chiral groups are 2-butyl (=1-methylpropyl), 2-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-methylbutyryloxy, 3-methylvaleroyloxy, 4-methylhexanoyloxy, 2-chlorpropionyloxy, 2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy, 1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-trifluoro-2-octyl and 1,1,1-trifluoro-2-octyloxy.
Compounds of formula I containing an achiral branched group R1 or R2 are of importance, for example, due to their reduction in the tendency towards crystallization. Branched groups of this type generally do not contain more than one branch. Preferred achiral branched groups are isopropyl, isobutyl (=methylpropyl), isopentyl (=3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3-methylbutoxy.
The polymerisable group P is preferably
CH2xe2x95x90CW1xe2x80x94COOxe2x80x94
CH2xe2x95x90CW2xe2x80x94(O)k1xe2x80x94, CH3xe2x80x94CHxe2x95x90CHxe2x80x94Oxe2x80x94, HOxe2x80x94CW2W3xe2x80x94, HSxe2x80x94CW2W3xe2x80x94, HW2Nxe2x80x94, HOxe2x80x94CW2W3xe2x80x94NHxe2x80x94, CH2xe2x95x90CW1xe2x80x94COxe2x80x94NHxe2x80x94, CH2xe2x95x90CHxe2x80x94(COO)k1-Phe-(O)k2xe2x80x94, Phe-CHxe2x95x90CHxe2x80x94, HOOCxe2x80x94, OCNxe2x80x94 and W4W5W6Sixe2x80x94, wherein W1 is H, Cl, CN, phenyl or alkyl with 1 to 5 C-atoms, in particular H, C1 or CH3, W2 and W3 are, independently of each other, H or alkyl with 1 to 5 C-atoms, in particular methyl, ethyl or n-propyl, W4, W5 and W6 are, independently of each other, Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phe is 1,4-phenylene, and k1 and k2 are, independently of each other, 0 or 1.
More preferably P is a vinyl group, an acrylate group, a methacrylate group, a propenyl ether group or an epoxy group, especially preferably, an acrylate or a methacrylate group.
Spacer group Sp can be any group that is known for this purpose to the skilled in the art. Spacer group Sp is preferably a linear or branched alkylene group having 1 to 20 C atoms, in particular 1 to 12 C atoms, in which one or more non-adjacent CH2 groups may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94NR0xe2x80x94, xe2x80x94SiR0R00xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOxe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94 in such a manner that O and/or S atoms are not linked directly to one another, wherein R0 and R00 are, independently of each other, H or alkyl with 1 to 4 C-atoms.
Typical spacer groups are, for example, xe2x80x94(CH2)pxe2x80x94, xe2x80x94(SiR0R00xe2x80x94O)pxe2x80x94, xe2x80x94(CH2CH2O)rxe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94Sxe2x80x94CH2CH2xe2x80x94 or xe2x80x94CH2CH2xe2x80x94NHxe2x80x94CH2CH2xe2x80x94, wherein p is an integer of 2 to 12, and r is an integer of 1 to 3.
Preferred spacer groups, for example, are ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylene-thioethylene, ethylene-N-methyl-iminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
Especially preferred are chiral compounds of formula I wherein Sp-X is alkylene or alkylene-oxy with 2 to 6 C atoms. Straight-chain groups are especially preferred.
In another preferred embodiment of the invention the chiral compounds contain at least one spacer group Sp that is a chiral group of formula IV:
wherein
Q1 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond,
Q2 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, which is different from Q1, and
Q3 is halogen, a cyano group or an alkyl or alkoxy group with 1 to 4 C atoms, which is different from Q2.
In case Q1 in formula IV is an alkylene-oxy group, the O atom is preferably adjacent to the chiral C atom.
Particularly preferred compounds of formula I are
wherein R and Rxe2x80x2 have one of the meanings of R1 in formula I and wherein any phenylene ring may be substituted by 1, 2 or 3 L groups.
In these preferred compounds R and Rxe2x80x2 are preferably alkyl or alkoxy with 1 to 12 C atoms or Pxe2x80x94Spxe2x80x94Xxe2x80x94 as defined above. Compounds having one or more substituted phenylene rings are preferably substituted in 2-, 3-2- and 3- or 3- and 5-position with F, Cl, CH3, OCH3 or CN.
The inventive chiral compounds can be synthesized according to, or in analogy to, known methods as described, for example, in WO 98/00428.
The preparation of unsymmetrical isosorbides of formula I is possible due to a difference in reactivity between the two hydroxy groups on the isosorbide. The 2-position in the isosorbide is least hindered and therefore reacts preferentially. Selective esterification of 1,4:3,6-Dianhydro-D-glucitol is described in Z. Cekovic and Z. Tokic, Communications, Synthesis, p. 610-612 (1989). It is possible to utilize this method to prepare, e.g., monoesters of isosorbide, and then to react the other hydroxy groups with a different acid.
Further methods of synthesis are illustrated in the examples.
The chiral compounds of formula I can be used in a liquid crystal mixture for displays exhibiting a helically twisted molecular structure of the liquid crystal matrix, for example, TN displays of the active or passive matrix type, STN, phase-change, guest-host, ferroelectric or cholesteric displays like SSCT (surface stabilized cholesteric texture) or PSCT (polymer stabilized cholesteric texture).
Thus, another object of the invention is a liquid crystal mixture, in particular a chiral smectic or cholesteric liquid crystal mixture, comprising at least one chiral compound of formula I.
Yet another object of the invention is a liquid crystal display comprising a liquid crystal medium containing at least one chiral compound of formula I.
The chiral compounds of formula I exhibit high values of the HTP. Preferred values of the HTP are xe2x89xa720, more preferably xe2x89xa740, in particular xe2x89xa760 xcexcmxe2x88x921. This enables the preparation of liquid crystal mixtures with a high helical twist, i.e., a low pitch, by using only low amounts of chiral compounds of formula I. This is a considerable advantage, as it is often observed that the addition of high amounts of chiral dopants to a liquid crystal mixture negatively affects its liquid crystal phase behavior and electrooptical properties, such as the dielectric anisotropy, the viscosity, or the clearing point. Thus, by using chiral compounds of formula I in a liquid crystal mixture or display, its properties are altered only to a minor extent; compared to prior art dopants, resulting, for example, in a lower threshold voltage and faster switching times of the display.
The chiral compounds of formula I are further characterized by a high solubility in a liquid crystal host mixture. Undesired spontaneous crystallization at low temperatures is reduced, and the operating temperature range of the mixture can be broadened. The use of a second dopant, which is often added to avoid crystallization, can thus be avoided.
A particularly preferred embodiment of the present invention therefore relates to a liquid crystal mixture comprising only one chiral compound, which is a compound of formula I, and to a display comprising such a mixture.
The chiral compounds of formula I also show a low temperature dependence of the HTP when added to a liquid crystal host mixture. They are thus useful as chiral dopants for liquid crystal mixtures and displays with a low temperature dependence of the pitch.
A liquid crystal mixture according to the invention comprises preferably 0.1 to 30%, in particular 1 to 25% and very particularly preferably 2 to 15% by weight of chiral compounds of formula I. It preferably comprises 1, 2 or 3 chiral compounds of formula I.
The compounds of formula I are especially suitable for use in cholesteric liquid crystal mixtures for cholesteric displays, in particular SSCT or PSCT displays. Cholesteric displays are described, for example, in WO 92/19695, WO 93/23496, U.S. Pat. No. 5,453,863 and U.S. Pat. No. 5,493,430.
It was found that, when using chiral compounds of formula I as dopants in liquid crystal mixtures for cholesteric displays, due to their high solubility and low temperature dependence of the HTP, a mixture with high helical twist and low temperature dependence can be achieved. Cholesteric mixtures with high brightness and low temperature dependence of the reflection color can thus be achieved even by using only one chiral dopant according to formula I. This is a considerable advantage over prior art, where it is often necessary to use two or more dopants to prevent crystallisation, and to use two dopants with opposite temperature dependence of the helical twist (e.g. one with positive temperature dependence and one with negative temperature dependence) to achieve good temperature compensation of the reflection wavelength.
Thus, a particularly preferred embodiment of the present invention relates to a cholesteric liquid crystal medium, in particular, for use in SSCT and PSCT displays, comprising one chiral dopant, which is a compound of formula I, preferably in an amount of 1 to 20%, in particular 2 to 15%.
The liquid crystal mixture preferably contains a chiral component which contains at least one chiral compound of formula I, and a nematic component comprising one or more nematic or nematogenic compounds.
Preferably the liquid crystal mixture contains 2 to 25, preferably 3 to 15 compounds, at least one of which is a chiral compound of formula I. The other compounds, forming the nematic component, are preferably low molecular weight liquid crystal compounds which are nematic or nematogenic substances, for example, azoxybenzenes, benzylidene-anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclohexanecarboxylic acid and of cyclo-hexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexyl-biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 1,4-bis-cyclohexylbenzenes, 4,4xe2x80x2-bis-cyclohexylbiphenyls, phenyl- or cyclo-hexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclo-hexylpyridazines, phenyl- or cyclohexyldioxanes, phenyl- or cyclo-hexyl-1,3-dithianes, 1,2-diphenyl-ethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenylcyclohexyl)-ethanes, 1-cyclohexyl-2-biphenyl-ethanes, 1-phenyl2-cyclohexyl-phenylethanes, optionally halogenated stilbenes, benzyl phenyl ether, tolanes, substituted cinnamic acids and further classes of nematic or nematogenic substances. The 1,4-phenylene groups in these compounds may also be laterally mono- or difluorinated.
The liquid crystal mixture of the preferred embodiment described above is preferably based on the above listed achival compounds.
In another embodiment, compounds that can be components of the above liquid crystal mixtures are of formula
Rxe2x80x2-Lxe2x80x2-Gxe2x80x2-E-Rxe2x80x3
wherein Lxe2x80x2 and E, which may be identical or different, are in each case, independently from one another, a bivalent radical of the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -B-Phe- or -B-Cyc- or their mirror images, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl and B is 2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.
Gxe2x80x2 is a bivalent group of xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94N(O)Nxe2x80x94, xe2x80x94CHxe2x95x90CYxe2x80x94, xe2x80x94CHxe2x95x90N(O)xe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94CH2xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94, xe2x80x94CH2xe2x80x94Sxe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94COO-Phe-COOxe2x80x94 or a single bond, wherein Y is halogen, preferably chlorine, or xe2x80x94CN.
Rxe2x80x2 and Rxe2x80x3 are, in each case, independently of one another, alkyl, alkenyl, alkoxy, alkenyloxy, alkanoyloxy, alkoxycarbonyl or alkoxycarbonyloxy with 1 to 18, preferably 3 to 12 C atoms, or alternatively one of Rxe2x80x2 and Rxe2x80x3 is F, CF3, OCF3, Cl, NCS or CN.
In most of these compounds Rxe2x80x2 and Rxe2x80x3 are, in each case, independently of each another, alkyl, alkenyl or alkoxy with different chain length, wherein the sum of C atoms in nematic media generally is between 2 and 9, preferably between 2 and 7.
Many of these compounds or mixtures thereof are commercially available. All of these compounds are either known or can be prepared by methods which are known per se, as described in the literature (for example, in Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), under reaction conditions which are known and suitable for said reactions. Use may also be made here of variants which are known per se, but are not mentioned here.
Polymerizable compounds of formula I or polymerizable liquid crystal mixtures comprising one or more compounds of formula I are useful for the preparation of polymerizable mixtures, which can be used, for example, in polymer stabilized liquid crystal displays, such as PSCT (polymer stabilized cholesteric texture) and anisotropic polymer gels, which can be used, for example, in scattering type displays. Anisotropic polymer gels and displays comprising them are disclosed, for example, in DE 195 04 224 and GB 2 279 659.
The chiral compounds of formula I and polymerizable liquid crystal mixtures comprising them are particularly useful for the preparation of anisotropic polymer films having helically twisted molecular structure with uniform planar orientation, i.e., wherein the helical axis is oriented perpendicular to the plane of the film.
Oriented cholesteric polymer films, for example, can be used as broad waveband reflective polarizers, for example, described in EP 0 606 940, WO 97/35219 and EP 0 982 605, as color filters, for security markings, or for the preparation of liquid crystal pigments for decorative or security uses.
For the preparation of anisotropic polymer gels or oriented polymer films, the liquid crystal mixture should comprise at least one polymerizable compound, which can be a compound of formula I or an additional polymerizable mesogenic or liquid crystalline compound.
Thus, another object of the invention is polymerizable liquid crystal mixtures comprising at least one chiral compound of formula I.
Examples of suitable polymerizable mesogenic compounds that can be used as components of the polymerizable liquid crystal mixture, are disclosed, for example, in WO 93/22397; EP 0,261,712; DE 195,04,224; WO 95/22586 and WO 97/00600. The compounds disclosed in these documents, however, are to be regarded merely as examples that shall not limit the scope of this invention.
Preferably, the polymerizable liquid crystal mixture comprises at least one polymerizable mesogenic compound having one polymerizable functional group and at least one polymerizable mesogenic compound having two or more polymerizable functional groups.
Examples of especially useful monoreactive chiral and achiral polymerizable mesogenic compounds are shown in the following list of compounds, which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention:
wherein, P has one of the meanings given above, x is an integer from 1 to 12, A and D are 1,4-phenylene or 1,4-cyclohexylene, v is 0 or 1, Y0 is a polar group, R0 is a non-polar alkyl or alkoxy group, Ter is a terpenoid radical, e.g., menthyl, Chol is a cholesteryl group, and L1 and L2 are, each independently, H, F, Cl, CN, OH, NO2 or an optionally halogenated alkyl, alkoxy or carbonyl group with 1 to 7 C atoms.
The polar group Y0 is preferably CN, NO2, halogen, OCH3, OCN, SCN, COR5, COOR5 or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R5 is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferably the polar group Y0 is F, Cl, CN, NO2, OCH3, COCH3, COC2H5, COOCH3, COOC2H5, CF3, C2F5, OCF3, OCHF2, or OC2F5, in particular, F, Cl, CN, OCH3 or OCF3.
The non-polar group R0 is preferably an alkyl group with 1 or more, preferably 1 to 15 C atoms or an alkoxy group with 2 or more, preferably 2 to 15 C atoms.
Examples of useful direactive chiral and achiral polymerizable mesogenic compounds are shown in the following list of compounds, which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention
wherein P, x, D, L1 and L2 have one of the meanings given above and y is an integer of 1 to 12, the same as or different from x.
A polymerizable liquid crystal material as described above comprises one or more chiral dopants which themselves do not necessarily have to show a liquid crystal phase and give good planar alignment themselves, in particular non-polymerizable chiral dopants.
The mono- and difunctional polymerizable mesogenic compounds of above formulae V and VI can be prepared by methods which are known per se and which are described in the documents cited above and, for example, in standard works of organic chemistry, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.
In a preferred embodiment of the invention the polymerizable liquid crystal mixtures comprise at least one inventive chiral compound, at least one monofunctional compound of formulae Va-Vm and at least one bifunctional polymerizable compound of formulae VIa-VIe.
In another preferred embodiment the polymerizable liquid crystal mixtures comprise at least one inventive chiral compound and at least two monofunctional compounds of formulae Va-Vm.
Another object of the invention is an anisotropic polymer film with an oriented chiral liquid crystalline phase obtainable by (co)polymerizing a liquid crystal mixture comprising at least one chiral compound of formula I and at least one polymerizable mesogenic compound preferably of formula Va-Vm, and VIa-VIe, and/or at least one polymerizable chiral compound of formula I.
To prepare an anisotropic polymer film having a chiral liquid crystalline phase with uniform orientation, the polymerizable liquid crystal can be coated onto a substrate, aligned, and polymerized in situ, for example, by exposure to heat or actinic radiation, to fix the uniform orientation of the liquid crystal molecules. Alignment and curing are carried out in the liquid crystalline phase of the mixture.
Actinic radiation means irradiation with light, e.g., UV light, IR light or visible light, irradiation with X-rays or gamma rays, or irradiation with high energy particles, such as ions or electrons. As a source for actinic radiation, for example, a single UV lamp or a set of UV lamps can be used. Another possible source for actinic radiation is a laser, e.g., a UV laser, an IR laser or a visible laser.
For example, when polymerizing by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or ions that start the polymerization reaction.
It is also possible to use a cationic photoinitiator, when curing reactive mesogens with, for example, vinyl and/or epoxide reactive groups, that photocures with cations instead of free radicals.
As a photoinitiator for radical polymerization, for example, the commercially available Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (all from Ciba Geigy AG) can be used, whereas in case of cationic photopolymerization the commercially available UVI 6974 (Union Carbide) can be used.
Preferably the polymerizable liquid crystal mixture comprising polymerizable chiral compounds of formula I and/or polymerizable mesogenic compounds of formulae V and/or VI additionally comprises 0.01 to 10%, in particular 0.05 to 8%, very preferably 0.1 to 5% by weight of a photoinitiator, especially preferably a UV-photoinitiator.
Polymerization is preferably carried out under an atmosphere of inert gas, preferably under a nitrogen atmosphere.
As a substrate, for example, a glass or quartz sheet, as well as a plastic film or sheet can be used. It is also possible to put a second substrate on top of the coated mixture prior to, during and/or after polymerization. The substrates can optionally be removed after polymerization. When using two substrates in case of curing by actinic radiation, at least one substrate has to be transmissive for the polymerization.
Isotropic or birefringent substrates can be used. In case the substrate is not removed from the polymerized film after polymerization, preferably isotropic substrates are used.
Preferably at least one substrate is a plastic substrate, for example, a film of polyester such as polyethyleneterephthalate (PET), of polyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC), especially preferably a PET film or a TAC film. As a birefringent substrate, for example, an uniaxially stretched plastic film can be used. For example PET films are commercially available from ICI Corp. under the trade name Melinex.
Preferably the polymerizable liquid crystal mixture I is coated as a thin layer on a substrate or between substrates, and aligned in its chiral mesophase into planar orientation, wherein the axis of the molecular helix extends transversely to the layer.
Planar orientation can be achieved, for example, by shearing the mixture, e.g., by means of a doctor blade. It is also possible to put a second substrate on top of the coated material. In this case, the shearing caused by putting together the two substrates is sufficient to give good alignment. Alternatively it is possible to apply an alignment layer, for example a layer of rubbed polyimide or sputtered SiOx, wherein x is 1 to 2, on top of at least one of the substrates, or to apply an electric or magnetic field to the coated mixture, in order to induce or enhance planar alignment. In a preferred method, planar alignment is induced or enhanced by addition of one or more surface-active compounds to the polymerizable mixture.
In some cases it is of advantage to apply a second substrate not only to aid alignment of the polymerizable mixture, but also to exclude oxygen that may inhibit the polymerization. Alternatively, the curing can be carried out under an atmosphere of inert gas. Curing in air, however, is also possible by using one or more suitable photoinitiators and high lamp power. When using a cationic photoinitiator, oxygen exclusion most often is not necessary, but water should be excluded.
A detailed description of the in situ polymerization of polymerizable mesogenic compounds can be found, for example, in D. J. Broer et al., Makromolekulare Chemie 190, 2255 (1989).
A polymerizable liquid crystal mixture for the preparation of anisotropic polymer films comprises preferably 0.1 to 35%, in particular 0.5 to 15% and very particularly preferably 0.5 to 5% by weight of one or more polymerizable chiral compounds of formula I.
Polymerizable liquid crystal mixtures are preferred that comprise 1 to 3 chiral compounds of formula I.
The inventive polymerizable liquid crystal mixtures can additionally comprise one or more other suitable components, for example, catalysts, sensitizers, stabilizers, co-reacting monomers or surface-active compounds.
In a preferred embodiment of the invention, the inventive polymerizable liquid crystal mixture comprises a stabilizer that is used to prevent undesired spontaneous polymerization, for example, during storage of the composition. As stabilizers, in principal, all compounds can be used that are known to the skilled in the art for this purpose. These compounds are commercially available in a broad variety. Typical examples for stabilizers are 4-ethoxyphenol or butylated hydroxytoluene (BHT).
It is also possible, in order to increase crosslinking of the polymers, to add up to 20% of a non mesogenic compound with two or more polymerizable functional groups to the polymerizable composition alternatively or additionally to the multifunctional polymerizable mesogenic compounds.
Typical examples for difunctional non mesogenic monomers are alkyldiacrylates or alkyldimethacrylates with alkyl groups of 1 to 20 C atoms. Typical examples for non mesogenic monomers with more than two polymerizable groups are trimethylpropanetrimethacrylate or pentaerythritoltetraacrylate.
Polymerization of inventive compositions comprising compounds with only one polymerizable functional group leads to linear polymers, whereas in the presence of compounds with more than one polymerizable functional group crosslinked polymers are obtained.
For the preparation of anisotropic polymer gels, the liquid crystal mixtures can be polymerized in situ as described above, however, in this case alignment of the polymerizable mixture is not necessary.
The inventive chiral compounds of formula I and liquid crystal mixtures, liquid crystal polymers or liquid crystal pigments comprising them are also suitable for use in cosmetic and pharmaceutical compositions, for example, in colored make-up as described in EP 815 826 or as UV-filters for the protection of human skin or hair, in particular, protection against UV-A and UV-B-radiation, as described, for example, in DE 196 29 761 or EP 1 038 941. The inventive dopants have a high HTP, therefore only small amounts are needed to yield a short pitch, resulting in a material that shows reflection in the UV range and is thus suitable as a UV-filter.
A liquid crystal mixture, liquid crystal polymer or liquid crystal pigment comprising a chiral compound of formula I which reflects UV light, in particular of a wavelength of 200 to 400 nm, is another object of the invention. Another object is a cosmetic composition, in particular, a cosmetic or pharmaceutical composition for protection of human skin or hair, comprising as UV-filter a liquid crystal mixture, a liquid crystal polymer or a liquid crystal pigment comprising a chiral compound of formula I which reflects UV light, in particular in a wavelength range of 200-440 nm, especially 280-400 nm, 200-230 nm (UV-C) and 280-330 nm (UV-B).
The values of the helical twisting power HTP of a chiral compound in a liquid crystal host are given according to the equation HTP=(pxc2x7c)xe2x88x921 in xcexcmxe2x88x921, wherein p is the pitch of the molecular helix, given in xcexcm, and c is the concentration by weight of the chiral compound in the host given in relative values (thus, e.g., a concentration of 1% by weight corresponds to a value of c of 0.01.)
The following abbreviations are used to illustrate the liquid crystalline phase behavior of the compounds: C=crystalline; N=nematic; S=smectic; N*, Ch=chiral nematic or cholesteric; I=isotropic. The numbers between these symbols indicate the phase transition temperatures in degree Celsius. Furthermore, mp. is the melting point, xcex94n is the birefringence at 589 nm and 20xc2x0 C., and xcex94xcex5 is the dielectric anisotropy at 20xc2x0 C. C* in a chemical formula denotes a chiral C atom. DCC is N,Nxe2x80x2-Dicyclohexylcarbodiimide, DMAP is 4-Dimethylaminopyridine, DCM is dichloromethane. xe2x80x9cConventional workupxe2x80x9d means: water is added if necessary, the mixure is extracted with methylene chloride, diethyl ether or toluene, the phases are separated, the organic phase is dried and concentrated by evaporation, and the product is purified by crystallization and/or chromatography.
Unless indicated otherwise, the HTP values of the examples were determined in the commercially available liquid crystal host mixture
BL087 (Merck KGaA, Darmstadt, Germany) at a concentration of 5% and a temperature of 20xc2x0 C.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following examples are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight.
The entire disclosure[s] of all applications, patents and publications, cited above or below, and of corresponding European application No. 01114896.2, filed Jul. 2, 2001, is hereby incorporated by reference.

Abstract: to liquid crystal mixtures comprising at least one chiral compound of formula I, to chiral linear or crosslinked liquid crystal polymers obtainable by polymerizing a polymerizable mixture comprising at least one chiral compound of formula I, to the use of chiral compound of formula I and mixtures and polymers obtained thereof in liquid crystal displays, active and passive optical elements, adhesives, synthetic resins with anisotropic mechanical properties, cosmetic and pharmaceutical compositions, diagnostics, liquid crystal pigments, for decorative and security applications, nonlinear optics, optical information storage or as chiral dopants, and to a liquid crystal display comprising a mixture comprising at least one chiral compound of formula I.


A bicycle is provided on which a person can efficiently ride in a comfortable posture along a slope and effectively utilize the strength of the legs while pedaling along a level road. This bicycle includes: a stem fixing a handle on an upper-end part thereof and including a front wheel-shaft supporting member in a lower part thereof; a front wheel attached pivotally via a front wheel shaft to a lower-end part of the front wheel-shaft supporting member; a front frame supporting a middle part of the stem in such a way that a front-end part thereof makes a handling turn freely, and extending rearward; a rear frame fixing a saddle on an upper-end part thereof, including a rear wheel-shaft supporting member in a lower part thereof, and attached pivotally at a lower-end part of the rear wheel-shaft supporting member via joint members to a rear-end part of the front frame in such a way that the rear frame sways back and forth freely; and a rear wheel disposed via a rear wheel shaft a predetermined height above the joint members at the rear wheel-shaft supporting member in such a way that the rear wheel rotates freely, and rotated by a pedal-attached crank on each side.

1. Field of the Invention
The present invention relates to a bicycle on which a person can efficiently ride in a comfortable posture along a slope and effectively utilize the strength of the legs while pedaling along a level road.
2. Description of the Background Art
In general, when going up a slope on a bicycle, as shown in FIG. 9, a rider along with the bicycle inclines backward with its uphill gradient. This forces the rider to pedal while bending the upper body more forward than when riding along a level road. This posture hinders the rider from exerting the strength of the legs effectively. Or, the rider may come apart from the saddle, thus forcing the rider to use significantly more labor.
In order to reduce labor taken to ride along an uphill, therefore, a bicycle in which the position of a saddle can be adjusted has conventionally been developed. However, any such bicycle is difficult to operate and handle (refer to Registered Utility Model Publication No. 36881, Japanese Patent Laid-Open Publication No. 57-114773 and Japanese Patent Laid-Open Publication No. 8-282562).
In addition, a chainless bicycle has also been developed in which the shaft of the rear wheel can be directly rotated using crank-attached pedals. This helps lighten the bicycle and simplify its structure. In such a bicycle, however, its body may turn over backward around a rear wheel on an uphill slope.
The above described conventional bicycle in which the position of the saddle can be adjusted has the problem of making it harder for the rider to operate and handle it. On the other hand, the chainless bicycle in which the shaft of the rear wheel can be directly rotated using crank-attached pedals has the problem of turning its body back around the rear wheel on an uphill slope.


A device and a method for the photolithographic exposure of biological substances is described, which comprises at least one light source, a bundle of optical fibers and a control unit, whereby each of the optical fibers can be controlled by light independently from one another and/or light can be coupled to each fiber independently.

The invention concerns a device and a method for the photolithographic exposure of biological substances.
DNA chips are ultra-small, generally planar surfaces, on which a large number of different oligomers (short, single-stranded DNA molecules) are introduced in a spatially organized manner. Such chips are used, for example, for the parallel recognition of numerous DNA sequences in a prepared tissue specimen. For this purpose, the chip surface is wetted with a solution of single-stranded DNA segments from the tissue specimen. Complementary DNA segments from the solution are deposited on the corresponding oligomers introduced on the chip surface (hybridization). After this, a determination is made of which places on the chip a hybridization has occurred by means of suitable methods, such as, e.g., fluorescent labeling. If one knows where on the chip the respective oligomers are introduced, conclusions can be made relative to the DNA sequences in the tissue specimen. For this purpose, usually a dense rectangular grid is defined on the chip support surface. One type of oligomer is introduced at each grid point in the form of a small spot. The maximum possible number of different DNA sequences on the chip is consequently equal to the number of grid points. Since one wishes to introduce as many types of oligomers as possible on one chip, but the chips must be as small as possible at the same time in order to be able to effectively hybridize, it is an important objective in the production of DNA chips to achieve as high a grid density as possible.
Different methods for DNA chip production are known in the prior art:
1) All oligomers are synthesized individually in a conventional manner in the test tube and then are pipetted onto the provided grid points on the support, typically by an automatic micropipetting device. This method is very time-consuming and expensive, since each oligomer must be prepared or purchased individually and must be introduced by hand into the pipetting device. The grid density is limited by the high angular imprecision of the typical piezoelectric micropipettes that are presently available.
2) The oligomers are synthesized directly on the chip by means of an automatic pipetting device. The oligomer chain provided on each grid point is built up base by base (nucleobases). The chemical method is basically the same as in conventional oligomer synthesis in the test tube. The difference is that all oligomers are produced simultaneously directly at the provided determination site by a single automatic device. The separate operating steps of oligomer synthesis and micropipetting of method 1) are thus combined into one uniform operating step. This in-situ synthesis normally proceeds as follows: The automatic pipetting device sequentially drops the first nucleobase provided for each grid point onto a prepared substrate. This is mechanically not very time-consuming or expensive, since there are only 4 different nucleobases (C, T, G, A). For example, 4 micropipettes coupled to one another can be used for this purpose. After applying the first nucleoside building block at each grid point, the substrate is washed and after a xe2x80x9ccapping stepxe2x80x9d, the protecting groups at the 5xe2x80x2xe2x80x94OH functions are removed, in order to make possible the reaction with the respective subsequent nucleoside building block. After this, the second nucleobase is pipetted onto each grid point. The substrate is then washed again and deprotected. In this way, the necessary oligomer chains are constructed step by step on each grid point. This method is not particularly rapid, since each nucleobase must be newly pipetted one after the other onto each grid point. As in the case of method 1), the grid density is limited by the imprecision of the micropipettes. The imprecision is even worse here, since each grid point must be contacted several times sequentially in a way that is as identical as possible.
3) The oligomers are synthesized directly on the support as in 2), but the targeted binding of the correct nucleobases to the correct grid points is done by means of a completely parallel, photolithographic technique instead of sequential, target-precise pipetting steps. The method is based on the fact that the 5xe2x80x2xe2x80x94OH protecting groups of oligonucleotides can be removed in a targeted manner by light of a specific wavelength. By suitable local irradiation patterns, oligonucleotide ends can thus be made capable of reaction at precisely those grid points at which one wishes to introduce a new nucleoside in the next step. By complete wetting of the chip surface with a nucleotide building-block solution, a nucleotide base is thus bound only to the sites that have been previously exposed, and all unexposed sites remain unchanged. The local exposure patterns are produced by positioning a photomicrographic black-white mask between the substrate and the light source. The mask covers all of the grid points, which are not to be made capable of reaction. The elongation of the oligomer chains by one nucleobase at all grid points is then conducted as follows: Those grid points which must be extended by the first of the 4 possible types of nucleobases (e.g., C) are precisely exposed by means of a first mask. Then the chip is wetted with a solution of the corresponding nucleotide base, whereupon only the exposed points are elongated by this base. Since the newly bound bases all have a protecting group, they do not further react in the following steps until their protecting groups are cleaved by another exposure. The chip is washed after this reaction step. Now, those grid sites, which must be elongated by the second of the 4 possible types of nucleobases (e.g., T) are precisely exposed by means of a second mask. Then the chip is again wetted with a solution of the corresponding nucleotide building block and the exposed sites in this way are elongated by this base. The procedure is the same for the remaining two bases (e.g., G and A). For the elongation of all oligomers by one nucleobase, one consequently requires four exposure steps and 4 photomasks. This method is very efficient due to the high parallel operation, and it is also suitable for obtaining very high grid densities, due to the high precision that can be obtained with photolithography. Of course, the method is very time-consuming and thus expensive, since a large number of photomasks must first be created for the production of a specific type of chip. Also, rigid requirements are placed on the positioning accuracy of the masks during exposure in the case of high grid densities, and these requirements can be fulfilled efficiently only by using very expensive apparatus.
4) The same method is applied as in 3), but instead of the large number of photographic masks, only a single, transmissive, liquid crystal display, which is controlled electronically and serves as a dynamic mask, is used. This method is simple and inexpensive, since photographic masks need not be produced and there is thus no positioning problem. One possible problem of this method is the limited optical contrast of the liquid crystal displays that are currently available (maximum 1:100). The light intensity ratio between exposed and covered points is thus reduced, which can have as a consequence a reduction in yield in the case of oligomer synthesis.
These methods of the prior art have a number of disadvantages. Of the above-described production methods for DNA chips, the photolithographic method with dynamic liquid crystal masks is the only one that permits a simple, inexpensive and reliable production of chips with high grid density. The deficient contrast of liquid crystal displays, however, has as a consequence a reduction in the quality of the oligomer points, which in the final analysis reduces the detection sensitivity of the chip.
The object of the present invention is thus to create a device, which overcomes the disadvantages of the prior art. Another object of the invention is the creation of another method for the photolithographic exposure of biological substances.
The object is solved by the characterizing features of the main claim. Advantageous embodiments of the invention are characterized in the dependent subclaims.
The object is solved according to the invention in that a device for the photolithographic exposure of biological substances is created, comprising at least one light source, a bundle of light-guiding optical fibers and a control unit, whereby each of the optical fibers can be controlled by light and/or light can be coupled to these fibers, independently of one another.
It is preferred that the light source emits monochromatic or continuous light in a wavelength range of 100 to 800 nm. It is particularly preferred that the light source is a laser, a luminous diode, a metal-vapor lamp, a gas-discharge lamp, a gas-excitation lamp, an incandescent-filament lamp or an arc lamp.
It is further advantageous that luminous diodes and/or optical switches are arranged for controlling the individual optical fibers.
It is particularly advantageous that the substances to be exposed are introduced directly at the ends of the optical fibers. However, it is also preferred that substances to be exposed are arranged on a separate support.
It is most especially preferred that substances to be exposed are arranged on a separate support, and that this support is a DNA chip, a PNA chip or a peptide chip.
According to the invention, the device preferably also has at least one detector.
It is thus preferred that at least one of the detectors is arranged in such a way that the latter detects the light used for exposure and/or at least one detector is arranged in such a way that it detects light reflected from the exposed substances and/or produced by fluorescence and that optical fibers and/or bundles of optical fibers are optionally provided for conducting light for the detectors. It is particularly preferred that the detectors are CCD detectors and/or CCD cameras.
It is very particularly preferred that a dynamic mask is provided for controlling the individual optical fibers. It is also particularly preferred that a set of static masks is provided for controlling the individual optical fibers.
A device according to the invention is most preferred, wherein the light source emits a spectrum of wavelengths that can effect the deprotection of nucleotides, nucleotide analogs and peptide nucleic acid building blocks for chain elongation and for constructing oligomers, and that a bundle of optical fibers is arranged between this light source and the substrate, in which light can be coupled selectively by targeted control, and that the solid phase on which the oligomer synthesis occurs is positioned precisely and rigidly behind the bundle of optical fibers, and that the solid phase on which the oligomer synthesis occurs is arranged in a chamber in which the solutions and/or reagents necessary for DNA or PNA synthesis can be introduced to this solid phase by additional devices.
It is preferred according to the invention that a separate support is arranged as the solid phase on which the oligomer synthesis occurs. It is further preferred according to the invention that the ends of the optical fibers themselves are the solid phase for conducting the oligomer synthesis.
Another subject of the present invention is a method for the photolithographic exposure of biological substances, wherein these substances are arranged on a surface or at the end of an optical fiber and exposed by means of light, which is guided by the optical fiber and originates from a light source, which is arranged at the other end of the optical fiber, whereby each point which lies opposite one end of the optical fiber is exposed independently of the other points, whereby the exposure pattern is selected in advance by means of a control unit.
It is specifically preferred, for exposure of DNA or PNA chips, that light of wavelengths which cause the deprotection of nucleotides, nucleotide analogs and peptide nucleic acid building blocks for chain elongation and for construction of oligomers be used, and that a bundle of optical fibers is arranged between this light source and the substrate, in which [fibers], light is selectively coupled to each fiber by targeted control, and that the solid phase on which oligomer synthesis occurs is positioned precisely and rigidly behind the bundle of optical fibers, and that the solid phase on which the oligomer synthesis occurs is arranged in a chamber in which solutions and/or reagents that are necessary for DNA or PNA synthesis are introduced onto the solid phase by additional devices.
It is further preferred according to the invention that subsequent hybridizations are conducted with a target DNA after the oligomerization has been produced on the DNA or PNA chips.
Another subject of the invention is a method, wherein one uses a device according to the invention for conducting the method.
It has been found surprisingly that the device according to the invention makes possible a simple and moderately priced photolithographic production of DNA chips of high grid density with an exposure contrast of far greater than 1:100. In this way, the simple production of qualitatively superior DNA chips in any laboratory is made possible for the first time.
The device according to the invention and the method solve the object that was set forth in a completely novel manner by combination of commercially available components. It makes possible the inexpensive production of DNA chips in a quality that has not been previously possible.
The basic concept of the device and of the method according to the invention consists of the fact that a specific exposure pattern is produced on the substrate not by targeted masking of grid points by means of a static or dynamic mass, but rather light is introduced directly by means of an optical fiber light guide individually to each of the grid points to be exposed. Therefore, the end of an optical fiber must be introduced over each grid point such that when light is coupled to the fiber, the light exiting at the end precisely illuminates the corresponding grid point. Consequently, the number of optical fibers that are necessary corresponds precisely to the grid points that are provided. In order to be able to produce any desirable exposure pattern, an independent control of each individual optical fiber must be made of whether or not light is coupled to it at a given time point. By coupling or not coupling light in a targeted manner to the correct fibers, those grid points that must be activated can be exposed exclusively at each exposure step, while all others remain unexposed.
The targeted coupling of light into the correct fibers each time must be controlled in a fully automatic electronic manner, and thus the method can be conducted in a simple way. One possible technical solution is to introduce a light source that can be turned on and off at the beginning of each optical fiber, which belongs to just this one fiber (e.g., a laser diode of the correct wavelength). Another possibility is the use of commercially available optical switches that can be controlled electrically. These involve a hardware component with 2 terminals or 2 optical fibers and an electrical control input. It can be determined by an electrical signal at the control input whether or not the two optical fibers will be optically combined. One optical switch and two optical fibers are thus necessary for each grid point. Light is permanently coupled to the free end of the first fiber, while the free end of the second fiber serves as the light output and is attached over the respective grid point. A single light source is sufficient for light coupling, if all input fibers are bundled correspondingly.
Both methods of targeted light coupling are equivalent for the electrical control. Only one control electronics unit is required, which can individually address each grid point. Basically, it does not matter whether light diodes or optical switches are controlled.
Another possibility for the targeted light coupling in the individual fibers of the optical fiber bundle is the use of automatically positioned static masks (e.g., photomasks or shadow masks) or an electronically controllable dynamic mask (e.g., an LCD), which is introduced between the light source and the input side of the fiber bundle. Any fiber inputs into which light will not be coupled at the respective exposure step can be masked in a targeted manner with the masks. The masks can be arranged geometrically in a different manner and particularly may be much larger than the array surface to be exposed, since the bundle of optical fibers can be fanned out or can be separated into individual fibers on the coupling side, as desired.
For the maximally attainable grid density of the chip, it does not matter how much space the light coupling system (individual light sources, optical switches, static or dynamic masks) requires. The grid density is only dependent on how densely the fiber ends on which the light emerges can be bundled. This possibility of geometrical packing represents the most essential advantage of the invention. In the case of a typical fiber diameter of approximately 100 micrometers, approximately 1000 grid points can be obtained per square centimeter on the exposure side, which is sufficient for many applications.
If it is too time-consuming to arrange the ends of the optical fibers that are to be introduced over the substrate in a uniform, rectangular lattice grid, one may also attach an unarranged fiber bundle over the substrate. The points on a chip produced in this way are then no longer grid-shaped, but are arranged randomly and irregularly. Nevertheless, for all chips, which have been produced by the same arrangement of optical fibers, the positions of the points are identical. Basically, one can know which type of oligomer has been synthesized at which position of the chip. It is sufficient for a given synthesis arrangement with a random bundling of light fibers to couple light sequentially to each individual optical fiber a single time and to establish the positions of the emitted light cone with a high-resolving CCD detector, which is placed in the plane of the substrate. A complete table with the assignment of all control addresses to the corresponding x-y substrate positions can be prepared in this way. This information is later used for evaluating all chips that are prepared with the corresponding arrangement.
For an evaluation according to the method of fluorescent labeling, one may optionally use the same unrastered arrangement of optical fibers, which has been used in the production, but in this case light is now not coupled to the other end of the fiber, but rather the fluorescent light occurring now in points on the substrate side is measured by means of photodetectors. For this purpose, a separate photodetector must be introduced at the position of the light source(s) at each fiber end. Such an optical reading system with optical fibers can considerably simplify chip detection in comparison with conventional detection methods by means of CCD detectors.
A very interesting and novel variant of application of the DNA chip synthesis method described here is the synthesis of oligomers directly onto the ends of the optical fibers instead of onto a separate substrate. This can be achieved by chemically preparing the end surfaces of the optical fibers through which the light is emitted in a way similar to the preparation of conventional DNA chip support surfaces. In this way, each end of the optical fiber is itself a small, independent support, on which one type of oligomer can be synthesized precisely with the usual photolithographic chemistry. The photoactivating light is thus no longer irradiated from outside onto the support surface, but is emitted directly at the support surface from the transparent, light-guiding support material. Instead of a single support surface with many different, small oligomer points, one now has a plurality of separate small support surfaces, each with one type of oligomer thereon. As in the case of conventional chips, the oligomer points must lie densely next to one another, and thus they can be used for an efficient hybridization. This can be achieved, as described above, by dense bundling of the fiber ends.
With such a synthesis on the ends of optical fibers, the family of oligomer points that is produced remains inseparably connected to the device used for the production. Hybridization and subsequent detection are then also conducted at the ends of the optical fibers, whereby the optical fibers are again used for a fluorescent detection in the direction opposite to the readout of the fluorescent signals. After one synthesis-hybridization-detection cycle, the tips of the optical fibers can be chemically cleaned and the device can thus be made ready for a new synthesis.

Device and method for photolithographically irradiating biological substances

Abstract: The device is particularly suitable for the exposure of DNA, PNA or peptide chips.