JP4580802B2 - Photosensitive composition, optical element using the same, and method for producing the same - Google Patents

Description

  The present invention relates to a photosensitive composition for an optical element having stable optical characteristics used for a liquid crystal display, an optical element using the same, and a method for producing the same.

  In a liquid crystal display, a retardation film is widely used as a retardation control functional layer. For example, in a reflective LCD, a linearly polarizing plate and a 1 / 4λ phase difference plate are used in combination to obtain circularly polarized light. Further, in a vertical alignment mode LCD which has been widely applied to liquid crystal TVs in recent years, a retardation film having a negative birefringence anisotropy (a negative film having a negative birefringence anisotropy) in order to reduce the viewing angle dependency. C plate) and a retardation film (positive A plate) having an optical axis horizontal to the substrate and having positive birefringence anisotropy are used.

  In addition, many retardation films such as a viewing angle compensation film using a discotic liquid crystal are put on the market. These retardation films are used by being bonded to the outside of the liquid crystal cell by bonding the other optical retardation plate and the polarizing plate to each other at a certain angle. In that case, since the refractive index of the adhesive used for bonding is different from that of the retardation plate and the polarizing plate, reflection of external light occurs at the bonding interface. This external light reflection lowers the display contrast and remarkably deteriorates the image quality.

Such a problem can be solved by forming a retardation control function layer in the cell using a liquid crystal material instead of the retardation film described above. That is, a liquid crystalline polymer having a glass transition point and capable of freezing the liquid crystal structure below the glass transition temperature, and having a reactive group such as an unsaturated bond in the molecular structure, the unsaturated bond By cross-linking in a liquid crystal layer state, a phase difference control function layer can be provided by using a polymerizable liquid crystal that can freeze the liquid crystal structure. Various materials have been proposed as the polymerizable liquid crystal material (see, for example, Patent Document 1).
Japanese National Patent Publication No. 11-513019

  However, conventionally, when a retardation control function layer is provided between a glass substrate and a color filter layer using a polymerizable liquid crystal in order to form a retardation control function layer in a cell, heating in the production of a color filter is performed. There is a problem that the performance of the phase difference control function layer deteriorates depending on the process. Further, even when the phase difference control function layer is provided on the color filter layer, there is a problem that cracks are generated in the phase difference control function layer due to the subsequent electrode installation step by sputtering of the transparent conductive film ITO.

  The present invention has been made in view of the above problems, and its purpose is to perform the performance of the phase difference control functional layer even against heating when manufacturing a color filter used in an image display device such as a liquid crystal display. Is provided, and a photosensitive composition for an optical element having stable optical characteristics, an optical element using the same, and a method for producing the same are provided. is there.

  The present inventors have found that the above problems are caused by the low crosslinking density of the retardation control function layer, and the distance between the crosslinking points is increased because each polymerizable liquid crystal is crosslinked by terminal groups. It is considered that the molecular orientation of the phase difference control function layer is disturbed, and as means for solving the above problems, at least a polymerizable liquid crystal material, a photopolymerization initiator, a compound having two or more alkylol groups, and two By using a crosslinking agent and a solvent composed of a mixture of the above compounds having an alkoxy group, a photosensitive composition excellent in compatibility can be obtained, and the photosensitive composition is further coated on a support material to obtain a liquid crystal state. After being cured by irradiating and curing with ultraviolet rays while being oriented at, the mesogenic skeleton of the polymerizable liquid crystal cured product is cross-linked by the action of a cross-linking agent with excellent compatibility, and a retardation control function Heat resistance of the layer Those with improved fine resistance ITO resistance.

  The invention of claim 1 is a photosensitive composition comprising at least a polymerizable liquid crystal material, a photopolymerization initiator, a crosslinking agent, and a solvent, wherein the crosslinking agent has two or more alkylol groups, It consists of a mixture with a compound having two or more alkoxy groups.

  According to a second aspect of the present invention, in the photosensitive composition according to the first aspect, the photosensitive composition contains an acid generator.

  The invention of claim 3 is an optical element comprising a support material, and a retardation control function layer obtained by curing a polymerizable liquid crystal material on the support material with a predetermined liquid crystal regularity. An optical element, wherein the phase difference control functional layer is formed using the photosensitive composition according to claim 1.

  According to a fourth aspect of the present invention, in the optical element according to the third aspect, the polymerizable liquid crystal material constituting the retardation control function layer is crosslinked between mesogenic skeletons via end groups and the crosslinking agent. It is characterized by being.

  According to a fifth aspect of the present invention, in the optical element according to the third or fourth aspect, the support material is a transparent substrate having an alignment film.

  According to a sixth aspect of the present invention, in the optical element according to the third or fourth aspect, the support material is a color filter substrate having an alignment film.

  According to a seventh aspect of the present invention, in the optical element according to the sixth aspect, a protective film is provided on the color filter of the color filter substrate.

  The invention of claim 8 is a method for producing an optical element, comprising: a support material; and a retardation control function layer formed by curing a polymerizable liquid crystal material on the support material with a predetermined liquid crystal regularity. The photosensitive composition according to claim 1 or 2 is coated on the support material, and the polymerizable liquid crystal material is irradiated with ultraviolet rays while being aligned in a liquid crystal state, and then subjected to heat treatment for crosslinking. And forming a phase difference control function layer.

  According to a ninth aspect of the present invention, in the method for manufacturing an optical element according to the eighth aspect, the support material is a transparent substrate having an alignment film.

  According to a tenth aspect of the present invention, in the optical element manufacturing method according to the eighth aspect, the support material is a color filter substrate having an alignment film.

  According to an eleventh aspect of the present invention, in the optical element manufacturing method according to the tenth aspect, a protective film is provided on the color filter of the color filter substrate.

According to the present invention, a photosensitive composition that forms good orientation is used, photocrosslinked while maintaining the orientation of the polymerizable liquid crystal, and further thermally crosslinked, thereby providing high hardness and excellent ITO resistance. An optical element having a phase difference control function layer with stable optical characteristics can be obtained. In addition, since the optical element of the present invention has the phase difference control function layer in the liquid crystal cell, the number of parts of the liquid crystal display is reduced and the cost can be reduced.
The manufacturing method of the optical element of the present invention is simple because it is fixed by photopolymerization with the polymerizable liquid crystal aligned by pre-baking and crosslinked by heat.

  Hereinafter, embodiments of the photosensitive composition for an optical element of the present invention, an optical element using the same, and a method for producing the optical element will be described in detail.

<Photosensitive composition>
The photosensitive composition of the present invention includes at least a polymerizable liquid crystal material, a photopolymerization initiator, a crosslinking agent, and a solvent, and includes a chiral agent, an acid generator, and a surfactant as necessary. Hereinafter, each component will be described.

(Polymerizable liquid crystal material)
In the present invention, a nematic liquid crystal can be used as the polymerizable liquid crystal layer, and such a material may contain a single monomer or two or more compounds of a polymerizable monomer molecule, a polymerizable oligomer molecule, a liquid crystal polymer, and the like.

As an example of such a polymerizable liquid crystal material, for example, a compound (I) represented by the following general formula (1) in the following (Chemical Formula 1) and a compound represented by the following (Chemical Formula 2) can be given. As the compound (I), it is also possible to use a mixture of two compounds included in the general formula (1).
Moreover, as a polymeric liquid crystal material, 2 or more types of the compound included in General formula (1) and the compound shown in following (Chemical formula 2) can also be mixed and used.

In the general formula (1) representing the compound (I), R ¹ and R ² each represent hydrogen or a methyl group, but R ¹ and R ² are both hydrogen due to the wide temperature range showing the liquid crystal phase. preferable. X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably a chlorine or methyl group. Moreover, a and b which show the chain length of the alkylene group which is a spacer with the (meth) acryloyloxy group of the molecular chain both ends of a compound (I), and an aromatic ring are respectively arbitrary integers in the range of 2-12. Although it can take, it is preferable that it is the range of 4-10, and it is more preferable that it is the range of 6-9. The compound of the general formula (1) in which a = b = 0 is poor in stability, easily subjected to hydrolysis, and the compound itself has high crystallinity. In addition, the compound of the general formula (1) in which a and b are each 13 or more has a low isotropic transition temperature (TI). For this reason, both of these compounds are not preferred because the temperature range showing liquid crystallinity is narrow.

In the example described above, an example of a polymerizable liquid crystal monomer has been described. However, in the present invention, a polymerizable liquid crystal oligomer, a polymerizable liquid crystal polymer, or the like can be used. As such a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, those conventionally proposed can be appropriately selected and used.
Here, since the retardation amount and the alignment characteristics are determined by the birefringence Δn and the film thickness of the liquid crystal molecules, Δn is preferably about 0.03 to 0.20, more preferably about 0.05 to 0.15.

(Chiral agent)
In the present invention, a chiral nematic liquid crystal having a cholesteric regularity obtained by adding a chiral agent to a nematic liquid crystal can also be suitably used. The chiral agent is a low molecular compound having an optically active site and means a compound having a molecular weight of 1500 or less. The chiral agent is mainly used for the purpose of inducing a helical pitch in the positive uniaxial nematic regularity expressed by the compound (I). As long as this purpose is achieved, the liquid crystallinity of the polymerizable liquid crystal material which is compatible with the compound (I) or the compound represented by the above (Chemical Formula 2) in a solution state or a molten state and can take the nematic regularity is impaired. As long as the desired helical pitch can be induced without any particular limitation, the type of low-molecular compound as a chiral agent shown below is not particularly limited, but it is necessary to have a polymerizable functional group at both ends of the molecule. It is preferable for obtaining a good optical element.

  It is essential that the chiral agent used for inducing a helical pitch in the liquid crystal has at least some chirality in the molecule. Accordingly, the chiral agent that can be used in the present invention includes, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine, a chiral sulfoxide, Alternatively, compounds having axial asymmetry such as cumulene and binaphthol can be exemplified. More specifically, commercially available chiral nematic liquid crystal, for example, S-811 manufactured by Merck Co., etc. may be mentioned.

  However, depending on the properties of the selected chiral agent, the nematic regularity formed by the compound (I) is deteriorated, the orientation is lowered, or when the compound is non-polymerizable, the curability of the liquid crystalline composition is lowered. There is a possibility that the reliability of the cured film is lowered. Furthermore, the use of a large amount of a chiral agent having an optically active site causes an increase in the cost of the composition. Therefore, in the case of producing a circularly polarized light controlling optical element having a short pitch cholesteric regularity, the chiral agent having an optically active site contained in the liquid crystalline composition of the present invention has an effect of inducing a helical pitch. It is preferable to select a large chiral agent, and specifically, a low molecular compound having axial asymmetry in the molecule as represented by the general formula (2), (3) or (4) shown in (Chemical Formula 3) The use of (II) is preferred.

In the general formula (2), (3) or (4) representing the chiral agent (II), R ⁴ represents hydrogen or a methyl group. Y is any one of the formulas (i) to (xxiv) shown in the above (Chemical Formula 4) or (Chemical Formula 5), and among them, the formulas (i), (ii), (iii), (v ) And (vii). Moreover, although c and d which show the chain length of an alkylene group can each take arbitrary integers in the range of 2-12, it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable. The compound of the general formula (2) or (3) in which the value of c or d is 0 or 1 lacks stability, is susceptible to hydrolysis, and has high crystallinity. On the other hand, a compound having a value of c or d of 13 or more has a low melting point (Tm). These compounds have low compatibility with the compound (I) exhibiting liquid crystallinity or with the compound (I), and there is a possibility that phase separation or the like may occur depending on the concentration.

  The amount of the chiral agent blended in the polymerizable liquid crystal material of the present invention is determined in consideration of the helical pitch inducing ability and the cholesteric property of the finally obtained polarization selective reflection layer. Specifically, although it varies greatly depending on the polymerizable liquid crystal material to be used, 0.01 to 60 parts by weight, preferably 0.1 to 40 parts by weight, more preferably 100 parts by weight of the total amount of the polymerizable liquid crystal material. Is selected in the range of 0.5 to 30 parts by weight, most preferably 1 to 20 parts by weight. When the blending amount is less than the above range, the polymerizable liquid crystal material may not be provided with sufficient cholesteric properties. When the blending amount exceeds the above range, the orientation of the molecule is inhibited and adversely affects when cured by actinic radiation. There is a risk of affecting.

  In the present invention, it is not essential that such a chiral agent has polymerizability. However, in consideration of the thermal stability and the like of the obtained retardation control function layer, it is preferable to use a polymerizable chiral agent that can be polymerized with the above-described polymerizable liquid crystal material and fix the cholesteric regularity. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain an optical element having good heat resistance.

(Photopolymerization initiator)
When these polymerizable liquid crystal layers are formed, it is necessary to add a photopolymerization initiator within a range that does not significantly impair the alignment of the liquid crystals. As the photopolymerization initiator, a radical polymerizable initiator can be used. Radical polymerizable initiators are compounds that generate free radicals by the energy of ultraviolet rays, for example, and are derivatives such as benzophenone derivatives such as benzoin and benzophenone or their esters; xanthones and thioxanthone derivatives; chlorosulfonyl, chloromethyl polynuclear aromatics Halogen-containing compounds such as compounds, chloromethyl heterocyclic compounds and chloromethylbenzophenones; triazines; fluorenones; haloalkanes; redox couples of photoreductive dyes and reducing agents; organic sulfur compounds; is there. Preferably, Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 907 (all manufactured by Ciba Specialty Chemicals), Darocur (Merck), Adeka 1717 (Asahi Denka Kogyo Co., Ltd.), 2 , 2′-bis (o-chlorophenyl) -4,5,4′-tetraphenyl-1,2′-biimidazole (manufactured by Kurokin Kasei Co., Ltd.) it can. These initiators can be used alone or in combination of two or more. When two or more kinds are used in combination, it is preferable not to inhibit the absorption spectral characteristics. In addition to the photopolymerization initiator, a sensitizer can be added within a range that does not impair the object of the present invention.
The amount of the polymerization initiator added is generally 0.01 to 15% by weight, preferably 0.1 to 12% by weight, more preferably 0.5 to 10% by weight. Can be added.

(Crosslinking agent)
In the present invention, as the crosslinking agent, a mixture of a compound having two or more alkylol groups and a compound having two or more alkoxy groups is used. Although it is possible to use a compound having two or more alkylol groups or a compound having two or more alkoxy groups as a cross-linking agent, an optimal phase for various liquid crystal combinations can be obtained by using a mixture. A molten state can be obtained. Crosslinking agents are alkylols and alkoxy compounds that cause an electrophilic substitution reaction on the aromatic ring. Specific examples of alkylols include 1,2-benzenedimethanol, 1,3-benzenedimethanol, Polyfunctional alkanol aromatic compounds such as 1,4-benzenedimethanol and 1,3,5-benzenedimethanol, polyfunctional alkanolureas such as dimethylolurea, dimethylolethyleneurea and dimethylolpropyleneurea, trimethylolpropane and trimethylol Multifunctional alkyl alkanol compounds such as propane monoallyl ether, polyfunctional alkanol melamine compounds such as trimethylol melamine, triethylol melamine, hexamethylol melamine, hexaethylol melamine, dimethylol benzoguanamine, trimethylol benzoguana And alkanol benzoguanamine compounds such as tetramethylol benzoguanamine. Specific examples of alkoxy compounds include 1,4-dimethoxymethylbenzene, 1,3,5-trimethoxymethylbenzene, 1,3,5-triazine-2. , 4,6-tri (dimethoxymethylamine), 1,3,5-triazine-2-methoxymethylamine-4,6-di (dimethoxymethylamine), 1,4-bis (methoxyphenoxy) benzene, trimethoxy Examples thereof include methyl melamine, hexamethoxymethyl melamine, N, N′-dimethoxymethyl urea, N, N′-dimethoxymethyl-4,5-dimethoxy-2-imidazolidione and the like.
The amount of such a crosslinking agent added is generally 1 to 50% by weight, preferably 5 to 30% by weight, and can be added to the polymerizable liquid crystal material.

(Acid generator)
In the present invention, as a preferred form, an acid generator is included as a catalyst. The acid generator is not particularly limited as long as it generates an acid directly or indirectly by light or heat, but various kinds of aromatic diazonium salt, diaryl iodonium salt, triarylsulfonium salt, triaryl selenium salt, etc. Examples thereof include onium salt compounds, sulfonic acid esters, and halogen compounds.
Specific examples of the aromatic diazonium salt include chlorobenzene diazonium hexafluorophosphate, dimethylaminobenzenediazonium hexafluoroantimonate, naphthyldiazonium hexafluorophosphate, dimethylaminonaphthyldiazonium tetrafluoroborate, and the like.
Diaryl iodonium salts include diphenyl iodonium tetrafluoroborate, diphenyl iodonium hexafluoroantimonate, diphenyl iodonium hexafluorophosphate, diphenyl iodonium triflate, 4,4′-di-t-butyl-diphenyl iodonium triflate, 4,4 Examples include '-di-t-butyl-diphenyliodonium tetrafluoroborate, 4,4'-di-t-butyl-diphenyliodonium hexafluorophosphate, and the like.
Examples of the triarylsulfonium salts include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, tri (p-chlorophenyl) sulfonium tetrafluoroborate, tri (p -Chlorophenyl) sulfonium hexafluorophosphate, tri (p-chlorophenyl) sulfonium hexafluoroantimonate, 4-t-butyltriphenylsulfonium hexafluorophosphate, and the like.
Triaryl selenium salts include triaryl selenium tetrafluoroborate, triaryl selenium hexafluorophosphate, triaryl selenium hexafluoroantimonate, di (chlorophenyl) phenyl selenium tetrafluoroborate, di (chlorophenyl) phenyl selenium hexafluorophosphate And di (chlorophenyl) phenyl selenium hexafluoroantimonate.
Examples of sulfonic acid esters include benzoin tosylate, p-nitrobenzyl-9,10-ethoxyanthracene-2-sulfonate, 2-nitrobenzyl tosylate, 2,6-dinitrobenzyl tosylate, 2,4-dinitrobenzyl tosylate Etc.
Examples of the halogen compound include 2-chloro-2-phenylacetophenone, 2,2 ′, 4′-trichloroacetophenone, 2,4,6-tris (trichloromethyl) -s-triazine, 2- (p-methoxystyryl)- 4,6-bis (chloromethyl) -s-triazine, 2-phenyl-4,6-bis (trichloromethyl) -s-triazine, 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) -S-triazine, 2- (4'-methoxy-1'-naphthyl) -4,6-bis (trichloromethyl) -s-triazine, bis-2- (4-chlorophenyl) -1,1,1-trichloroethane Bis-1- (4-chlorophenyl) -2,2,2-trichloroethanol, bis-2- (4-methoxyphenyl) -1,1,1-trichloroethane, etc. can give.

(Surfactant)
In the case of forming a polymerizable liquid crystal layer, it is preferable to add a surfactant as long as it does not significantly impair the alignment of the liquid crystal in order to improve the coating properties of the photosensitive composition solution. Surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, polyoxyethylene / polyoxypropylene block copolymers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters , Nonionic surfactants such as polyoxyethylene fatty acid esters and polyoxyethylene alkylamines, fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates Salt, alkyl phosphate, polyoxyethylene alkyl sulfate ester salt, naphthalene sulfonic acid formalin condensate, special polycarboxylic acid type polymer interface Sexual agents, anionic surface active agents such as polyoxyethylene alkyl phosphoric acid ester can be used.
The amount of such a surfactant added is generally 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight, and can be added to the polymerizable liquid crystal material.

(solvent)
The polymerizable liquid crystal and each of the above components can be dissolved in various organic solvents to form a solution, which can be applied on a predetermined support material. The solvent used in the photosensitive composition solution is a solvent that can dissolve the above-described polymerizable liquid crystal material and the like, and a solvent that does not hinder the alignment performance on the substrate provided with the alignment material. There is no particular limitation as long as it is present.

  Specifically, hydrocarbons such as benzene, toluene, xylene, n-butylbenzene, diethylbenzene, tetralin, ethers such as methoxybenzene, 1,2-dimethoxybenzene, diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketones such as cyclohexanone and 2,4-pentanedione, ethyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, esters such as γ-butyrolactone, 2-pyrrolidone, N-methyl Amide solvents such as -2-pyrrolidone, dimethylformamide, dimethylacetamide, chloroform, dichloromethane, carbon tetrachloride, dichloroethane Halogen solvents such as tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve One kind or two or more kinds of alcohols such as butyl cellosolve and phenols such as phenol and parachlorophenol can be used.

  If only a single type of solvent is used, the solubility of the polymerizable liquid crystal material or the like may be insufficient, or the substrate having the alignment performance may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents. Among the above-mentioned solvents, preferred as a single solvent are a hydrocarbon solvent and a glycol monoether acetate solvent, and preferred as a mixed solvent is a mixed system of ethers or ketones and glycols. It is. The concentration of the solution varies depending on the solubility of the liquid crystalline composition and the desired film thickness of the optical functional layer, but is usually 1 to 60% by weight, preferably 3 to 40% by weight.

<Optical element>
The optical element of the present invention is an optical element having a support material and a retardation control function layer formed by curing a polymerizable liquid crystal material with a predetermined liquid crystal regularity on the support material, The control function layer is formed using the above photosensitive composition. Furthermore, the polymerizable liquid crystal material constituting the retardation control function layer is characterized in that it is crosslinked between end groups and between mesogenic skeletons.

(Support material)
As a support material of the present invention, a substrate having an alignment film formed on a transparent substrate, a color filter substrate having an alignment film formed on a color filter layer, or a protective film provided on the color filter layer, A color filter substrate on which an alignment film is formed is used.

(Alignment film material)
As the alignment film provided on the support material, polyimide or the like, which is a conventionally known alignment film material, is used, and is obtained by laminating on a substrate and then performing a rubbing process or a photo-alignment process. Alternatively, silicon oxide may be obliquely deposited on the substrate to form an alignment film. A commercially available alignment film material can be used as the alignment film material used in the present invention. Specifically, alignment film material (Sunever) manufactured by Nissan Chemical Co., Ltd., alignment film material (QL, LX series) manufactured by Hitachi Chemical DuPont Microsystems Co., Ltd., alignment film material (AL series) manufactured by JSR Co., Ltd. ), An orientation agent (Rixon Aligner) manufactured by Chisso Corporation can be used.

(Phase difference control function layer)
The retardation control functional layer constituting the optical element of the present invention is formed using the above-described photosensitive composition, and the polymerizable liquid crystal material polymerized while being oriented in a certain direction is formed by a crosslinking agent. The mesogenic skeleton is crosslinked to form a three-dimensional structure, which improves heat resistance and characteristics during ITO film formation.
In the present invention, the thickness of the retardation control function layer is not particularly limited, but is preferably about 0.5 to 10 μm in view of productivity and the like.

(Measurement)
The birefringence of the optical element of the present invention can be measured by measuring retardation and film thickness. For measuring retardation, a commercially available apparatus such as KOBRA-21 series (Oji Scientific Instruments) can be used. The measurement wavelength is preferably in the visible light range (380 to 780 nm), and is preferably measured in the vicinity of 550 nm where the relative luminous sensitivity is the highest.
For film thickness measurement, a commercially available apparatus such as a stylus type step meter such as DEKTAK (Sloan) can be used.
Furthermore, for measuring the surface hardness of the coating film, it is possible to use a commercially available device such as an ultra-micro hardness meter such as a Fischer scope.

<Method for manufacturing optical element>
FIG. 1 is a process cross-sectional view showing an example of a method for producing an optical element of the present invention, and shows a method for producing an optical element in which a phase difference control function layer is formed on a transparent substrate provided with an alignment film. Hereafter, the manufacturing method of the optical element of this invention is demonstrated using FIG.

  A transparent substrate 1 is prepared (FIG. 1A). As the transparent substrate 1, a glass substrate or a heat-resistant transparent resin substrate conventionally used for a color filter is used. Next, an alignment film material such as polyimide is applied on the transparent substrate 1 and a rubbing process is performed to obtain a support material 3 provided with an alignment film 2 imparted with alignment performance (FIG. 1B).

  Next, a photosensitive composition containing at least a polymerizable liquid crystal material 4, a photopolymerization initiator, a crosslinking agent 5, and a solvent is applied onto the alignment film 2 to form a coating film (FIG. 1C). Examples of the method for applying the photosensitive composition include spin coating, roll coating, slide coating, printing, and die coating.

  Next, the substrate on which the coating film has been formed is pre-baked to remove the solvent. At this time, the polymerizable liquid crystals 4 are arranged in a certain direction by utilizing the fluidity of the prebaking heating (FIG. 1D). The pre-baking temperature and time depend on the characteristics of the material contained in the photosensitive composition and cannot be generally specified, but are usually 70 ° C. to 120 ° C. for several minutes to 30 minutes.

Next, ultraviolet rays 6 are exposed while the polymerizable liquid crystals 4 are arranged in a certain direction, and the terminal groups of the polymerizable liquid crystals 4 are crosslinked with each other and cured (FIG. 1E). As the ultraviolet rays 6, high-pressure mercury lamps, xenon lamps, metal halide lamps, and the like are used with irradiation light having a wavelength of about 300 to 500 nm. The amount of irradiation light varies depending on the type and composition of the polymerizable liquid crystal 4 and the type and amount of the photopolymerization initiator, but is usually in the range of about 10 to 3000 mJ / cm ² .

  Next, by performing a heat treatment, the mesogenic groups of the polymerized polymerizable liquid crystal 4 are cross-linked by a cross-linking part 8 with a cross-linking agent, and a polymerizable liquid crystal having a three-dimensional structure is arranged in a certain direction, The phase difference control function layer 9 is formed, and the optical element 10 having the phase difference control function layer 9 is formed on the support material 3 (FIG. 1 (f)). The heating temperature and time depend on the type and composition of the polymerizable liquid crystal 4 and the reaction start temperature of the crosslinking agent 5, but are usually 150 ° C. to 260 ° C. for about 10 minutes to 60 minutes.

  The optical element 10 can be a liquid crystal display in which an optical element is provided inside the liquid crystal cell by further providing a color filter layer having a black matrix layer thereon.

  In the embodiment of the above manufacturing method, the case where the support material is provided with the retardation control function layer on the transparent substrate having the alignment film has been described. However, in the optical element manufacturing method of the present invention, the support material is the alignment film. In the case of a color filter substrate having a color filter substrate, it can be similarly applied to a case where a protective film is provided on the color filter of the color filter substrate.

Example 1
An alignment film AL1254 manufactured by JSR Co., Ltd. was applied on a 100 × 100 mm glass substrate to a film thickness of 0.065 μm using a spin coater, and baked in an oven at 230 ° C. for 1 hour. Then, alignment treatment was performed on the substrate using a rubbing apparatus.

  Next, RMM34 (manufactured by Merck; 21.25 parts by weight) as a polymerizable liquid crystal exhibiting a nematic liquid crystal phase, Irgacure 907 (manufactured by Ciba Specialty Chemicals; 1.25 parts by weight) as a photopolymerization initiator, and crosslinking 1,4-benzenedimethanol (manufactured by Kanto Chemical Co., Ltd .; 1.0 part by weight) and Nicalac MW-30HM (manufactured by Sanwa Chemical Co., Ltd .; 1.5 parts by weight) as an agent, and MP-triazine (Sanwa Chemical Co., Ltd.) as an acid generator A photosensitive composition comprising 2.5 parts by weight) and diethylene glycol dimethyl ether (75 parts by weight) was prepared as a polymerizable liquid crystal solution. Further, a glass substrate with an alignment film was set on a spin coater, and the liquid crystal solution was spin-coated with a film thickness of about 1.5 μm (after firing).

Next, the film was heated at 80 ° C. for 3 minutes for orientation treatment, and the liquid crystal transition point at which the cloudy state became a transparent state was visually confirmed. Then, a liquid crystal layer is formed by irradiating ultraviolet rays at 20 mW / cm ² for 5 seconds with an ultraviolet irradiation apparatus having an ultra-high pressure mercury lamp on the liquid crystal layer as it is, and then baked for 60 minutes using an oven at 230 ° C. for phase difference control function A cured film as a layer was formed. Using a Fischer Scope H-100 manufactured by Fischer Instruments Co., Ltd. equipped with a Vickers indenter, a load of 1.5 mN was applied to the universal hardness of the resulting cured film at a rate of 37.5 μN / sec in the thickness direction at room temperature. It was about 300 N / mm ² when calculated from the indentation amount when held for 5 seconds.

Further, the obtained cured film was subjected to a pressure of 6.0 × 10 ⁻¹³ Torr, an argon gas flow rate of 78.0 sccm, an oxygen gas flow rate of 0.9 sccm, and an applied power of 5 kW at 200 ° C. using an ULVAC sputtering device (SV9540). Then, ITO sputtering was performed for 14 minutes, and an ITO film having a thickness of 1400 mm and a surface resistance of 30Ω □ was formed on the cured film. The obtained ITO film did not generate cracks and had good surface quality.

(Example 2)
This example was carried out except that 1,4-benzenedimethanol (manufactured by Kanto Chemical Co .; 1.0 part by weight) and Nicalac MX-280 (manufactured by Sanwa Chemical Co., Ltd .; 1.5 part by weight) were used as the crosslinking agent. When a liquid crystal layer was formed in the same manner as in Example 1, the surface hardness of the coating film was 290 N / mm ² . Further, no crack was generated in the ITO film obtained after the ITO film formation, and the surface quality was good.

(Comparative Example 1)
When the liquid crystal layer was formed in the same manner as in Example 1 except that the cross-linking agent of Example 1 was not used, the surface hardness of the coating film was 200 N / mm ² , and cracks occurred in the ITO film after ITO film formation. The coating film became cloudy.

It is process sectional drawing which shows an example of the manufacturing method of the optical element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Alignment film 3 Support material 4 Polymerizable liquid crystal 5 Crosslinking agent 6 Ultraviolet ray 7 Polymerization part 8 Crosslinking part 9 Phase difference control functional layer 10 Optical element

Claims (11)

  A photosensitive composition comprising at least a polymerizable liquid crystal material, a photopolymerization initiator, a crosslinking agent and a solvent, wherein the crosslinking agent comprises a compound having two or more alkylol groups, and two or more alkoxy groups. A photosensitive composition comprising a mixture with a compound having the same.   The photosensitive composition according to claim 1, wherein the photosensitive composition contains an acid generator.   An optical element having a support material and a retardation control function layer obtained by curing a polymerizable liquid crystal material on the support material with a predetermined liquid crystal regularity, wherein the retardation control function layer is claimed. An optical element formed by using the photosensitive composition according to claim 1.   The optical element according to claim 3, wherein the polymerizable liquid crystal material constituting the retardation control function layer is crosslinked between end groups and between mesogenic skeletons via the crosslinking agent.   The optical element according to claim 3, wherein the support material is a transparent substrate having an alignment film.   5. The optical element according to claim 3, wherein the support material is a color filter substrate having an alignment film.   The optical element according to claim 6, wherein a protective film is provided on the color filter of the color filter substrate.   A method for producing an optical element, comprising: a support material; and a retardation control function layer obtained by curing a polymerizable liquid crystal material on the support material with a predetermined liquid crystal regularity. The photosensitive composition according to 2 is coated on the support material, and the polymerizable liquid crystal material is irradiated with ultraviolet rays while being aligned in a liquid crystal state, and then subjected to heat treatment to be crosslinked to form a retardation control functional layer. Forming an optical element.   The method for manufacturing an optical element according to claim 8, wherein the support material is a transparent substrate having an alignment film.   The method of manufacturing an optical element according to claim 8, wherein the support material is a color filter substrate having an alignment film. The method for manufacturing an optical element according to claim 10, wherein a protective film is provided on the color filter of the color filter substrate.

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