EP0772662A1 - Verres a cristaux liquides - Google Patents

Verres a cristaux liquides

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Publication number
EP0772662A1
EP0772662A1 EP95928480A EP95928480A EP0772662A1 EP 0772662 A1 EP0772662 A1 EP 0772662A1 EP 95928480 A EP95928480 A EP 95928480A EP 95928480 A EP95928480 A EP 95928480A EP 0772662 A1 EP0772662 A1 EP 0772662A1
Authority
EP
European Patent Office
Prior art keywords
liquid
crystalline glass
crystalline
glass according
group
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95928480A
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German (de)
English (en)
Inventor
Paulus Pieter De Wit
Erwin Wilhelmus Petrus Erdhuisen
Stephen James Picken
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Akzo Nobel NV
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Akzo Nobel NV
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Publication date
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Publication of EP0772662A1 publication Critical patent/EP0772662A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/22—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and nitrogen atoms as chain links, e.g. Schiff bases
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/12—Compounds containing oxirane rings with hydrocarbon radicals, substituted by singly or doubly bound oxygen atoms
    • C07D303/18—Compounds containing oxirane rings with hydrocarbon radicals, substituted by singly or doubly bound oxygen atoms by etherified hydroxyl radicals
    • C07D303/20—Ethers with hydroxy compounds containing no oxirane rings
    • C07D303/22—Ethers with hydroxy compounds containing no oxirane rings with monohydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C225/00—Compounds containing amino groups and doubly—bound oxygen atoms bound to the same carbon skeleton, at least one of the doubly—bound oxygen atoms not being part of a —CHO group, e.g. amino ketones
    • C07C225/22—Compounds containing amino groups and doubly—bound oxygen atoms bound to the same carbon skeleton, at least one of the doubly—bound oxygen atoms not being part of a —CHO group, e.g. amino ketones having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
    • C08G59/22—Di-epoxy compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C08G59/50—Amines
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/28—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and sulfur atoms as chain links, e.g. thioesters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
    • C09K19/3086—Cyclohexane rings in which at least two rings are linked by a chain containing nitrogen atoms
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/60—Pleochroic dyes
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3016—Polarising elements involving passive liquid crystal elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
    • G11B7/25—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing liquid crystals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2601/00—Systems containing only non-condensed rings
    • C07C2601/06—Systems containing only non-condensed rings with a five-membered ring
    • C07C2601/10—Systems containing only non-condensed rings with a five-membered ring the ring being unsaturated
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G02F1/133637—Birefringent elements, e.g. for optical compensation characterised by the wavelength dispersion

Definitions

  • the present invention is directed to liquid-crystalline glasses for optical applications and retardation layers.
  • Liquid-crystalline glasses are well-known.
  • the term glasses refers to compositions which when cooling (at a faster rate than 0.01°/s) from the melting point or from 3/2 Tg (if no melting point is observed) do not crystallise but are transformed into the glassy state and remain frozen in that state.
  • liquid-crystall ne glasses are meant, glasses where the liquid- crystalline phase is frozen in.
  • the liquid-crystalline glasses described here all have a nematic structure.
  • J. Mater. Chem. 1, 3 (1991), 347-356 provides an overview of the presently known liquid- crystalline glasses. The article shows that it is hard to prepare liquid-crystalline glasses which are stable and also have a high transition temperature (Tg above room temperature).
  • stable glasses refers to glasses which are not subject to cold crystallisation upon being heated.
  • 47-62 dimeric li uid-crystalline molecules are described which are interconnected via a sulphinyl or sulphonyl bridge.
  • These compounds having a Tg in the range of 12° to 50°C display cold crystallisation between Tg and Tc.
  • DD-A1-242627 discloses the same compounds as described above, including mixtures thereof. In the mixtures the cold crystallisation is suppressed.
  • Mol . Cryst. Liq. Cryst. 191 (1990) describes naphthalene-containing liquid-crystalline glasses. These glasses are not stable.
  • Liquid Crystals Vol. 11, No. 5 (1992), 785-789 describes a number of liquid-crystalline glasses based on a inopyrene which have a Tg (glass transition temperature) ranging from 35° to 66°C. Several of these glasses do not exhibit any crystallisation between Tg and Tc. However, it is clear from Chem. Mater. 4 (1992), 1246-1253 that these liquid-crystalline glasses have negative dielectric anisotropy and hence cannot be properly oriented in an electric field, which is a drawback in the case of some optical applications. The same publication discloses other liquid-crystalline glasses based on aminopyrene of fairly high transition temperatures (Tg ranging from 29° to 54°C) .
  • Tg glass transition temperature
  • the invention provides (hydrolytically and thermally) stable liquid- crystalline glasses which have a high Tg and are readily orientable.
  • liquid-crystalline glasses according to the invention comprise compounds according to formula 1:
  • R* represents an aromatic group having 5 to 24 carbon atoms, an aromatic group-containing aliphatic group having 6 to 24 carbon atoms, a heterocyclic group having 4 to 24 carbon atoms, or a cyclic aliphatic group having 6 to 24 carbon atoms;
  • R* represents -H, a non-mesogenic group or a mesogenic group with a spacer
  • Ra may represent the same groups as R*, but may be chosen independently from R*, R* and R* ;
  • R * may represent the same groups as R*. but may be chosen independently from R*, R ⁇ , and R»;
  • R may represent the same groups as R*, but may be chosen independently from R 2 , R* and R*. with not more than 25% of all R*.
  • the liquid-crystalline glasses according to formula 1 were found to have a high transition temperature (the LC glasses in the examples all have a Tg above 50°C) . Furthermore, the viscosity of the glasses is sufficiently low between Tg and Tc to give trouble-free rapid orientation. In addition, the glasses are so stable that even after multiple heating cycles cold crystallisation does not occur. Moreover, these li uid-crystalline glasses do not contain any Schiff's bases and so are hydrolytically stable.
  • liquid-crystalline glasses according to the invention are pre-eminently suited for use in a wide range of optical applications, e.g., in optical data storage and retardation layers for LCDs.
  • the glasses according to the invention are obtained by reacting a dia ine of the Ri group with mesogenic group-containing epoxides.
  • X stands for -0-, -S0 -, -CH -, -S-, -C(0)-, or
  • n stands for 1 or 0, and m stands for 0, 1, or 2.
  • Suitable mesogenic groups with spacers are depicted in the formulae below. Glasses having such mesogenic groups are obtained by reacting the epoxides corresponding to the groups below with a diamine.
  • C C
  • C C
  • R stands for -0-R», -OCO-R>, -COOR» , -CN, -NO2, or
  • R' stands for an alkyl group having 1 to 5 carbon atoms
  • R» stands for an alkyl group having 1 to 5 carbon atoms
  • R» stands for an alkyl group having 1 to 15 carbon atoms
  • t is 1-6
  • u is 1-7
  • v is 0-3;
  • Rio stands for -H or -CH3; R11 stands for-H or alkyl, and n has the same meaning as in the formulae above.
  • groups which act as a mesogenic group in combination with a specific diamine may act as a non- esogenic group in combination with another diamine. This unpredictability of liquid- crystalline materials is known to the artisan. The artisan can easily choose the suitable side-groups for a specific diamine.
  • R groups include: -(CH 2 ) ⁇ -CH 3 ,
  • Suitable non-mesogenic groups are groups obtained from the ring- opening reaction of epoxides of methoxy biphenyls, cyanobiphenyls, and biphenyls. It shouldnbe-noted that methoxy bephenyl epoxides can both act as mesogenics and as non-mesogenics depending on the diamine used.
  • i s given to l iquid-crystal l ine glass containing a pol abl e mesogeni c group Polable groups contai n one or more permanent dipole moments di rected more or less along the l ong axi s of the mesogenic group , such that there i s positive di electri c anisotropy.
  • Thi s makes it possible to orient fi lms of the l iquid-crystal l ine glass using a static electri c field.
  • R pol able mesogenic groups contain, e.g., a -CN or -NO2 group.
  • Vertogen and en de Jeu Thermotropic liquid crystals, fundamentals (Springer, 1987), pp. 195-201.
  • the liquid-crystalline glasses according to the invention are especially suited to be used in optical applications.
  • the liquid-crystalline glasses according to the invention are pre-eminently suited to be used in LCD retardation layers.
  • the functioning of retardation layers is described in EP-A1-0 565 182 and EP-A3-0380 338, which describe liquid-crystalline polymers for use in retardation layers.
  • the liquid-crystalline glasses according to the invention have a low viscosity between Tg and Tc. This low viscosity permits rapid homogeneous arrangement of the liquid-crystalline glasses into a nematic structure having an angle of rotation as desired.
  • the film In the case of an angle of rotation of 90° (or -90), the film is called “twisted nematic"; if the angle of rotation is greater, the film is called “supertwisted nematic.”
  • the liquid-crystalline glasses according to the invention are suitable for use in retardation layers without twist. In that case the arrangement of the liquid-crystalline layer will be homeotropical or uniform planar. At angles of rotation exceeding 360° the structure goes through more than one full rotation within a single layer. The length covered by the structure in a full rotation is called the pitch.
  • the liquid-crystalline glasses according to the invention can be used to make retardation layers which have a thickness of more than five times the pitch. It was even found possible to make retardation layers which have a thickness of 20 times the pitch.
  • the orientation of this type of layers is usually called cholesteric.
  • the liquid-crystalline glasses according to the invention have a Tg of well above room temperature, the liquid-crystalline glass does not have to be incorporated into a rigid cell, as is the case with low-molecular weight liquid-crystalline material. Since the different compounds according to formula 1 are easily iscible, and also different mesogenic groups can be present within one compound according to formula 1, the birefringence and the dispersion of the retardation layers can be exactly matched with the appropriate active liquid-crystalline cell. By varying the mesogenic group the dispersion can be varied. In this way the use of mesogenic groups containing a cyclohexyl group or a bicyclooctane group instead of a phenyl group will make it possible to alter the dispersion. The birefringence can be lowered by reducing the mesogenic group density.
  • the invention is also directed to retardation layers containing liquid-crystalline glasses according to the invention.
  • the retardation layers may be prepared as follows: a thin layer of liquid-crystalline glass is applied between two orienting substrates. Generally, a thin layer of liquid-crystalline glass will be provided on either or both of the orienting substrates by means of spin coating, screen printing, meter bar coating, melt coating, or some other conventional coating technique. The two substrates are then placed one on top of the other. To set the thickness of the retardation layer, spacers of a specific diameter may be provided between the two substrates. As a rule, spheres of glass, polymer or silica are used to this end. Next, the whole is heated to a temperature between Tg and Tc (usually to about 10°C below Tc), which causes the glass to start arranging itself.
  • Tg and Tc usually to about 10°C below Tc
  • the substrates may be of either glass or plastic. If they are of glass, it is preferred to use thin glass substrates of a thickness of 20 to 500 micrometers. This allows retardation layers to be made which are lightweight, thin, and somewhat flexible.
  • Various techniques are known for making an orienting substrate. For instance, the substrate itself may be rubbed in a single direction. The substrate in that case may be made of, e.g., polyimide, polyvinyl alcohol, glass, etc. Alternatively, the substrate may be provided with a thin orienting layer.
  • This may be a thin polymer layer which can be rubbed, e.g., polyimide, polyvinyl alcohol, etc.
  • this thin orienting layer may be a Si0 x layer evaporated at an angle of less than 90°, usually of 60° or 86°.
  • a substrate of poor flexibility is used for SiO x evaporation, such as glass or quartz.
  • a twisted structure is obtained by giving one of the two substrates a different orientation direction from that of the other substrate.
  • the liquid-crystalline material is frequently mixed with a chiral material: the so-called chiral dopant.
  • any optically active compound may be used to this end.
  • cholesterol derivatives and 4-(4-hexyloxy-benzoyloxy) benzene acid 2-octyl-ester.
  • retardation layers up to 5 wt.% of chiral dopant is employed in relation to the total amount of liquid-crystalline material.
  • some of the compounds according to formula 1 may be provided with chiral centres.
  • this is done by providing the mesogenic group with a chiral chain (group Ri) or spacer, since in this way the transition temperatures will hardly if at all be adversely affected.
  • groups of mesogenic groups with chiral chains have already been described above. Since the carbon originally at the ⁇ -position of the epoxide group is asymmetrical also, its chiral version may be used as well. In that case, use is made of an epoxy-containing mesogenic group with a chiral centre in the epoxide group. Of course, the chiral centre may also be located in the diamine. It is not necessary to use two substrates to make a retardation layer.
  • liquid-crystalline assumes a sufficiently twisted structure of its own accord, a single orienting substrate will suffice.
  • a sufficiently twisted structure can be obtained if the liquid-crystalline material contains a sufficient quantity of chiral dopant, and the layer thickness is accurately controlled.
  • cholestric layers can also be used as cholesteric reflectors or cholesteric polarisers. In these cases, more chiral dopant is employed than for the application in retardation layers.
  • liquid-crystalline glasses according to the invention may be used for digital data storage such as in Compact Discs (CDs, both recordable and rewritable) or digital films.
  • Digital films may be of different shapes, e.g., tape, cards, and disks which cannot be written or read as specified by the CD standard.
  • the orientation in these CDs or films may be either ho eotropic or uniform planar.
  • various read out principles may be employed. For instance, in the case of homeotropic orientation (i.e., perpendicular to the substrate), dichroic dye may be blended in, making it possible to read out data via the difference in absorption.
  • dichroic dye refers to a dye which in an oriented medium (e.g., a nematic liquid-crystalline phase) will have a dichroic ratio (absorption
  • Dichroic dyes in other words, will absorb one polarisation direction of linearly polarised light to a much greater extent than the other one.
  • the mesogenic groups, and hence the dichroic dye molecules are oriented perpendicular to the film's surface, and there is only low absorption of the incident light by the dichroic dye molecules.
  • the polarisation direction of the light is perpendicular to its propagation direction as the incident light travels in many cases perpendicularly towards the film ' s surface.
  • the homeotropic orientation is converted into an isotropic one. Rapid cooling causes this local isotropic orientation to be frozen in.
  • the dichroic dye molecules will likewise be isotropically oriented, resulting in a substantially higher absorption of the incident light.
  • 2/3 of the dichroic dye molecules -on average- is positioned with the long axis parallel with the CD surface (i.e. on average 1/3 along the x-axis of the plane of the film, and 1/3 along the y-axis ).
  • the polarisation direction of the incident light (either x_ or y-polarised) is now parallel with the long axis of the dichroic dye molecules, and thus a high absorption is realised.
  • the dichroic dye may be mixed or incorporated into the liquid- crystalline glass.
  • an epoxy- functionalised dichroic dye may be co-reacted with the other mesogenic group-containing epoxides.
  • any dichroic dye may be employed, providing it is sufficiently stable to be mixed or incorporated into the liquid-crystalline glass.
  • azo dyes, anthraquinone dyes, croconium and squarilium based dyes are suitable.
  • the invention is also directed to novel croconium compounds with mesogenic groups.
  • dichrioc dyes are not necessary and the liquid-crystalline glass may be oriented differently, e.g. uniform planar.
  • Writing out data with the aid of a solid state laser requires that the liquid-crystalline glass film be, or be rendered, near-infrared light absorbing. Generally, this is done by blending in or incorporating a near-infrared absorbing dye. Preferably, the same (diode) laser can be employed for writing as well as reading.
  • CDs as specified by the CD standard are read out by a solid state laser. In the case of a CD wherein the read out principle is based in the difference in absorption of dichroic dye in a homeotropic medium, use is made of a dichroic dye which absorbs the laser light during writing and creates a difference in absorption during reading.
  • dichroic dye be greatly dichroic but not fully oriented, so that a sufficient quantity of light will be absorbed during the writing.
  • the objective is a light absorption percentage in the range of 2 to 40% of the incident light in the homeotropic (virgin) state.
  • Dichroic near-infrared dyes which can be blended in are, among others, anthraquinone dyes: IR-750 ® , ex Nippon Kayaku Co. Ltd, squarilium dyes: NK-2772®, ex Nippon Kankoh - Shikiso Kenkyusho Co.
  • liquid-crystalline glasses according to the invention can be employed also to make high-density CDs based on the difference in absorption principle when dichroic dyes having an absorption maximum in this range are used.
  • dichroic dyes having an absorption maximum in this range include: azo dyes: SI-361 ® , ex Mitsui Toatsu Chemicals GmbH, anthraquinone dyes: LCD 116 ® and LCD 118 ® , ex Nippon Kayaku Co.
  • the reading out and writing of data in the liquid- crystalline glass/dye system can take place at different wavelengths.
  • a dichroic dye as mentioned-above
  • said writing light absorbing dye is hardly susceptible to orientation, or is not very dichroic, since otherwise absorption during the writing would be unsatisfactory. For that reason preference is given to dyes which are not elongated in shape (e.g., molecules in platelet form or spherical molecules).
  • These writing light absorbing dyes may be incorporated into the liquid-crystalline glass by co-reacting the dye diamines with the other diamines.
  • a film or CD is made by applying a solution of the glass onto a substrate and evaporating the solvent.
  • Suitable substrates include PET, PET-ITO, metal, glass, cellulose acetate, polycarbonate, polycarbonate-Al , silicon, amorphous polyolefins, etc.
  • these substrates are provided with a thin layer of metal such as aluminium or gold or a layer of material with a high dielectric constant such as silicium nitride, silicium oxide or ZNSe.
  • films having a thickness of 0.2 to 10 micrometers are employed.
  • surfactants may be, int. al., silanes, higher alcohols, and the like, e.g., n-dodecanol and Liquicoat® PA, ex Merck.
  • the liquid-crystalline layer By poling the liquid-crystalline layer in a magnetic or electric field.
  • the electric field may be generated by corona poling (using a sharp needle or a thin wire as electrode).
  • a counter-electrode on the other side of the liquid-crystalline layer (e.g., an ITO-layer, a metal layer, or a conductive polymer layer), so that the poling field will be positioned over the liquid-crystalline layer.
  • the liquid-crystalline layer may be provided with a conductive layer on either side, and an electric field applied thereto.
  • Uniform planar orientation can likewise be obtained by surface treatment. Since the liquid-crystalline glasses according to the invention have a low viscosity between Tg and Tc, they can be made into fine uniform planar films or CDs.
  • liquid-crystalline glasses according to the invention can easily be made into homogeneously scattering films which permit local isotropic writing after the addition of suitable dyes, with a laser or some other source of heat.
  • the liquid-crystalline glasses according to the invention are rendered serviceable also for low density digital storage and analog data storage.
  • analog data storage refers both to human readable rewritable displays such as smart cards and thermal paper and to machine readable media (such as media which can be read with a bar code reader).
  • the films can be prepared by spin coating, meter bar coating, melt coating, screen printing, and any other conventional technique for coating on a substrate.
  • Suitable substrates are of PET, glass, polycarbonate, PVC, ABS, polystyrene, metal, and paper.
  • the films may have different formats, such as .disks, cards, and tape.
  • a homogeneously scattering film is obtained by heating the film to above Tc and then leaving it to cool to room temperature.
  • the creation of small domains gives a scattering texture. It was found that films of liquid-crystalline glasses according to the invention can be initialised within 2 seconds in this way. This, in its turn, means that written films can be erased within 2 seconds in this way and prepared for rewriting.
  • a contrast layer can be applied beneath the liquid-crystalline glass layer.
  • This may be a refelecting layer, which may be of any material reflecting light. Examples include metal substrates or foils of copper, aluminium, gold, silver, nickel, steel, metallised plastic substrates or foils such as aluminised PET, metallised paper, metal coated metal or plastic substrates such as used in the car industry.
  • the contrast layer may be made up of a layer having a low index of refraction, e.g., a thin layer of air.
  • the liquid- crystalline glass layer may be provided with a protective coating.
  • the dyes should be dichroic and co-oriented with the liquid-crystalline glass.
  • the liquid-crystalline glass according to the invention is applied onto an optically transparant substrate, after which the liquid-crystalline glass layer is oriented uniformly planarly.
  • the invention is also directed to polarisers comprising a liquid-crystalline glass containing dye according to the invention.
  • UV-stabilisers may be incorporated into the glasses.
  • An example of such an epoxy- functionalised UV-stabiliser is listed in Macromol . 26 (1993), 3227-3229.
  • the epoxide of methoxyphenyl benzoate (epoxide 4) was prepared, except that only half the amount of caustic solution was used for epoxide 4.
  • Using various diamines glasses were prepared by the general method for the synthesis of LC glasses specified above.
  • epoxide of cyanostilbene (epoxide 5), and the epoxide of nitrotolane (ph ⁇ ph-N02, epoxide 6) were prepared in a manner analogous to that for the synthesis of the epoxide of cyanobiphenyl.
  • the epoxides 7 and 8 were used in the liquid-crystalline glasses according to the invention to alter the dispersion of retardation layers made of these liquid-crystalline glasses.
  • Liquid-crystalline cyanobiphenyl glasses containing different diamines were intermixed.
  • the results in TABLE II show that by varying the diamines the Tg and the Tc can be set as desired. Further, the use of mixtures in optimal mixing ratios was found to promote the stability of the liquid-crystalline glasses.
  • Blends were made of liquid-crystalline glasses of epoxide 1 and 3-SDA (glass 1) and liquid-crystalline glasses of epoxide 6 and m-XDA (glass 2). The results are given in TABLE III. From the results it can be seen that the Tg and Tc can be set by using blends of liquid- crystalline glasses.
  • Liquid-crystalline glasses were obtained by reacting ODA with epoxide 1 and another epoxy.
  • the results in TABLE IV show that the incorporation of different epoxides in one liquid-crystalline glass molecule does not destroy the liquid-crystalline behaviour and the Tg and TC can be set by varying the amount of epoxides of a specific ty e-
  • Liquid-crystalline glasses were obtained by reacting 3-SDA with epoxide 1 and another epoxy.
  • the results in TABLE V again show that the incorporation of different epoxides in one liquid-crystalline glass molecule does not destroy the liquid-crystalline behaviour and the Tg and Tc can be set by varying the amount of a specific epoxide.
  • Liquid-crystalline glasses were obtained by reacting SDA with epoxide 1 and a non-mesogenic group-containing epoxy.
  • the non-mesogenicBepoxides were obtained in a manner analogous to the preparation of epoxide 1.
  • the results in TABLE VI show that by incorporating non-mesogenic groups in the liquid-crystalline glass the liquid crystalline behaviour is not destroyed. It was further noticed that a reduction of the scattereing of single domain films of these liquid-crystalline glasses was obtained after heating during the orientation process.
  • ph is a phenyl group
  • the solution of liquid-crystalline glass with spacers was spin coated onto the two pretreated glass substrates.
  • the layer thickness obtained was 4 micrometers.
  • the two glass films were dried in a vacuum oven for 16 hours at 20°C. They were then placed one on top of the other under a 60° difference in orientation direction and moulded at a temperature of 160°C. Next, the sample was cooled to 115°C, and after 5 minutes to room temperature. The quality of the resulting retardation film was determined with the aid of various optical techniques such as described in E.P. Raynes, "Molecular Crystals,” Liquid Crystals Letters 4(3-4) (1987), 69-75.
  • Liquid-crystalline glass of m-XDA and epoxide 1 was dissolved in cyclopentanone and filtered. Using a meter bar, the solution was applied onto a 100 micrometers thick Alu-PET substrate (based on Melinex 401®, ex ICI). The solvent was removed by drying at room temperature for 5 minutes and heating to 60°C for 15 minutes. Obtained was a film with a thickness of about 6 micrometers. The liquid- crystalline layer was provided with a protective coating based on Actilane 200®, ex Akcros Chemicals.
  • the film was rendered homogeneously light scattering by heating to 134°C, followed immediately by cooling to about 20°C in >2 seconds. Writing with a thermal printing head gave a very good contrast. The film was erased by the same method.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Liquid Crystal Substances (AREA)
  • Polarising Elements (AREA)
  • Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)

Abstract

La présente invention concerne des verres à cristaux liquides stables ayant une température de transition élevée et facilement orientables. De tels verres conviennenent pour des applications en optique. On obtient les verres décrits par l'invention en faisant réagir un diamine avec des époxydes contenant des groupes mésogènes. Ils conviennent notamment pour les couches de retard optique des affichages, les supports de données numériques tels que disques compacts, les supports de données analogiques et les polariseurs.
EP95928480A 1994-07-26 1995-07-26 Verres a cristaux liquides Withdrawn EP0772662A1 (fr)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
NL9401217 1994-07-26
NL9401217 1994-07-26
NL9500489 1995-03-13
NL9500489 1995-03-13
NL1000314 1995-05-08
NL1000314 1995-05-08
PCT/EP1995/002981 WO1996003476A1 (fr) 1994-07-26 1995-07-26 Verres a cristaux liquides

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EP0772662A1 true EP0772662A1 (fr) 1997-05-14

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CN (1) CN1157631A (fr)
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WO (1) WO1996003476A1 (fr)

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ATE201514T1 (de) * 1995-12-22 2001-06-15 Dejima Tech Bv Temperatur-angepasste verzögerungsschicht
JPH1124078A (ja) * 1997-07-04 1999-01-29 Sekisui Chem Co Ltd 光学機能フィルム及びその製造方法並びに液晶表示装置
ATE490299T1 (de) 2007-03-02 2010-12-15 Basf Se Zur antistatikausrüstung und verbesserung der elektrischen leitfähigkeit von unbelebtem organischen material geeignete additivformulierung

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JPS6131490A (ja) * 1984-07-24 1986-02-13 Mitsubishi Chem Ind Ltd 液晶組成物
JPS62267755A (ja) * 1986-05-16 1987-11-20 Fuji Xerox Co Ltd 電子写真感光体
US5112759A (en) * 1989-03-30 1992-05-12 Canon Kabushiki Kaisha Electrophotographic photosensitive member
US5389285A (en) * 1989-12-11 1995-02-14 Hercules Incorporated Liquid crystal coupled dichroic dyes
DE4007056A1 (de) * 1990-03-07 1991-09-12 Bayer Ag Polymere epoxidnetzwerke mit ueberstruktur
EP0475238A3 (en) * 1990-09-13 1994-05-25 Dow Chemical Co Mesogenic glycidyl esters
ES2067848T3 (es) * 1990-09-24 1995-04-01 Akzo Nobel Nv Poliesteres cristalinos liquidos y sensibles al infrarrojo, adecuados para uso en almacenamiento optico de datos, procedimientos para la preparacion de los mismos, y aparato que contiene un poliester cristalino liquido sensible al infrarrojo.
US5605732A (en) * 1992-01-06 1997-02-25 Canon Kabushiki Kaisha Aminium salt compound and optical recording medium
GB9209047D0 (en) * 1992-04-27 1992-06-10 Minnesota Mining & Mfg Thermal transfer materials

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WO1996003476A1 (fr) 1996-02-08
KR970704856A (ko) 1997-09-06
CA2195866A1 (fr) 1996-02-08

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