JPH11287902A5 - - Google Patents

Description

B. Binder Resin for Roughened Surface Layer (a) Next, the roughened surface layer in the present invention will be described. The resin constituting the roughened surface layer in the present invention can be a resin that is cured by either radiation or heat, or a combination thereof.
The radiation-curable resin may be a composition obtained by appropriately mixing monomers, oligomers, and prepolymers having polymerizable unsaturated bonds such as acryloyl groups, methacryloyl groups, acryloyloxy groups, and methacryloyloxy groups. Examples of the monomers include styrene, methyl acrylate, methyl methacrylate , methoxypolyethylene methacrylate, cyclohexyl methacrylate, phenoxyethyl methacrylate, ethylene glycol dimethacrylate, dipentaerythritol hexaacrylate, and trimethylolpropane trimethacrylate. Examples of the oligomers and prepolymers include acrylates such as polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, alkyd acrylate, melamine acrylate, and silicone acrylate, as well as unsaturated polyesters and epoxy compounds. These may be used alone or in combination. When flexibility of the cured film is required, it is preferable to use a small amount of monomer, and to further reduce the crosslinking density, it is preferable to use a monofunctional or difunctional acrylate monomer. Conversely, when severe durability such as heat resistance, abrasion resistance, and solvent resistance is required for the cured film, it is preferable to increase the amount of monomer and use a trifunctional or higher functional acrylate monomer.

To cure the radiation-curable resin as described above, it is sufficient to irradiate it with radiation such as ultraviolet rays, electron beams, or X-rays, and if necessary, a polymerization initiator can be added appropriately. Note that when curing with ultraviolet rays, it is necessary to add a photopolymerization initiator. Examples of the photopolymerization initiator include acetophenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, and 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, benzophenone, methyl o-benzoylbenzoate, Examples include benzophenones such as 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide , and (4-benzoylbenzyl)trimethylammonium chloride; thioxanthones such as 2,4-diethylthioxanthone and 1-chloro-4-dichlorothioxanthone; and 2,4,6-trimethylbenzoyldiphenylbenzoyl oxide. These can be used alone or in combination. Furthermore, amine compounds such as N,N-dimethyl-p-toluidine and 4,4'-diethylaminobenzophenone can also be used as accelerators (sensitizers). The content of the photopolymerization initiator is preferably in the range of 0.1 to 10 wt.% based on the radiation-curable resin. Amounts greater or less than this range result in poorer effects.

In the present invention, as described above, it is preferable to use an ultraviolet-curable epoxy compound as the radiation-curable resin and a photocationic polymerization initiator as the polymerization initiator, but in this case, it is preferable to mix an ultraviolet-curable acrylic compound in order to control the properties of the paint and the coating film, such as viscosity, crosslink density, heat resistance, chemical resistance, etc. Examples of such acrylic compounds include monofunctional acrylates such as lauryl acrylate, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxy-3-phenoxy acrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate , pentaerythritol triacrylate, dipentaerythritol hexaacrylate, trimethylolpropane acrylic acid benzoate, and trimethylolpropane. Examples of monomers and oligomers include acrylic acid derivatives such as polyfunctional acrylates such as benzoic acid esters; monofunctional methacrylates such as 2-ethylhexyl methacrylate, n-stearyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxybutyl methacrylate; methacrylic acid derivatives such as polyfunctional methacrylates such as 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, and glycerin dimethacrylate; and urethane acrylates such as glycerin dimethacrylate hexamethylene diisocyanate and pentaerythritol triacrylate hexamethylene diisocyanate.

(b) Pigment The roughened layer of the present invention contains a resin filler and silica, roughening the surface of the roughened layer to improve abrasion resistance and anti-reflection effects. Spherical silica is suitable, and examples of spherical silica include those obtained by hydrolyzing a silicate ester in an alcohol solution using ammonia as a catalyst, and those obtained by adhering silicic acid obtained from water glass through processes such as ion exchange and dialysis to fine silica particles. Silica is preferably used alone as the inorganic pigment, but pigments such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide can also be used as needed. In this case, it is preferable that the average particle size of the pigment used in combination is smaller than that of the silica. Examples of resin fillers include organic transparent or white pigments such as acrylic resin, polystyrene resin, polyethylene resin, epoxy resin, silicone resin, and beads. In particular, a resin filler that is spherical and does not absorb oil is preferred. By using a spherical filler, the parts that protrude from the surface of the roughened layer become smoother, making it difficult for dirt such as oil to adhere and making it easier to wipe off any dirt that does adhere.

(a) Low Refractive Index Layer In the present invention, in order to obtain a superior anti-reflection function, it is preferable to provide a low refractive index layer on the roughened layer. In particular, it is preferable to provide a two-layer surface layer by providing a high refractive index layer on the roughened layer, followed by a low refractive index layer with a lower refractive index than the high refractive index layer. The low refractive index layer will be described below. The composition of the low refractive index layer is not particularly limited, but it is preferably configured so that its critical surface tension is 20 dyne/cm or less. If the critical surface tension is greater than 20 dyne/cm, it becomes difficult to remove dirt adhering to the low refractive index layer. Furthermore, in order to improve the anti-reflection effect, the refractive index of the low refractive index layer is preferably 1.45 or less. Examples of materials having these characteristics include inorganic low-reflection materials obtained by microparticulating inorganic materials such as LiF (refractive index n=1.4), _MgF2 (n=1.4), _3NaF.AlF3 (n=1.4), _AlF3 (n=1.4) _{Na3AlF6 (} n=1.33) _SiO2 (n=1.45) and incorporating them into acrylic resins, epoxy resins, etc., and organic low-reflection materials such as fluorine-based and silicone-based organic compounds, thermoplastic resins, thermosetting resins, and radiation-curable resins. Among these, fluorine-based fluorine-containing materials are particularly preferred in terms of preventing contamination.

Other examples include fluorine-containing methacrylates such as 2-(perfluorodecyl)ethyl methacrylate, 2-( perfluoro -7-methyloctyl)ethyl methacrylate, 3-( perfluoro -7-methyloctyl)-2-hydroxypropyl methacrylate, 2-( perfluoro -9-methyldecyl)ethyl methacrylate, 3-( perfluoro -8-methyldecyl)2- hydroxypropyl methacrylate, fluorine-containing acrylates such as 3-perfluorooctyl -2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-9-methyldecyl)ethyl acrylate, epoxides such as 3-perfluorodecyl-1,2-epoxypropane, 3-( perfluoro -9-methyldecyl)-1,2-epoxypropane, and radiation-curable fluorine-containing monomers, oligomers, and prepolymers such as epoxy acrylates.These can be used alone or in combination.

In addition, examples of film-forming agents that can be used include alkoxysilanes, hydrolyzates of metal alkoxides or metal salts, and fluorine-modified polysiloxanes. By using such film-forming agents, the critical surface tension of the low refractive index layer is reduced, thereby suppressing adhesion of oil. In the present invention, the low refractive index layer can be obtained by diluting the above-described material in a solvent, applying it to the roughened layer or the high refractive index layer using a spin coater, roll coater, printing, or other method, drying it, and then curing it with heat, radiation (in the case of ultraviolet light, the above-mentioned photopolymerization initiator is used), or the like. Radiation-curable fluorine-containing monomers, oligomers, and prepolymers have excellent stain resistance, but poor wettability, and therefore, depending on their composition, problems may arise such that the low refractive index layer is repelled by the roughened layer or high refractive index layer, or the low refractive index layer peels off from the roughened layer or high refractive index layer. Therefore, it is desirable to use an appropriate mixture of monomers, oligomers, and prepolymers having a polymerizable unsaturated bond such as an acryloyl group, methacryloyl group, acryloyloxy group, or methacryloyloxy group, which were explained above as the radiation-curable resin used for the roughened layer.
When the transparent substrate is a resin film such as TAC or PET, it is susceptible to damage from heat, and therefore the material for the low refractive index layer is preferably a radiation curable resin.

The resin used in the high refractive index layer may be any transparent resin, such as a thermosetting resin, a thermoplastic resin, a radiation (including ultraviolet) curable resin, etc. Examples of the thermosetting resin include a phenolic resin, a melamine resin, a polyurethane resin, a urea resin, a diallyl phthalate resin, a guanamine resin, an unsaturated polyester resin, an aminoalkyd resin, a melamine-urea co-condensation resin , a silicon resin, a polysiloxane resin, etc., and these resins may contain, as necessary, a crosslinking agent, a curing agent such as a polymerization initiator, a polymerization accelerator, a solvent, a viscosity modifier, etc.

Examples of radiation-curable resins that can be used include oligomers or prepolymers such as (meth)acrylates of polyfunctional compounds such as polyester resins, polyether resins, acrylic resins, epoxy resins, alkyd resins, polybutadiene resins, spirol acetal resins, urethane resins, and polyhydric alcohols, and reactive diluents such as monofunctional and polyfunctional monomers such as ethyl (meth)acrylate, ethylhexyl (meth)acrylate, styrene , methylstyrene, and N-vinylpyrrolidone.

The antireflection material 10 was used to prepare a polarizing film 20 having the configuration shown in Fig. 2. Next, the polarizing film 20 was attached to a glass substrate 33 as shown in Fig. 3 to obtain a liquid crystal display 30. The image size of each liquid crystal display 30 was 10.4 inches, the resolution was 800 x 600 dots, and the image contrast was evaluated by the following method.

[Explanation of symbols]
10...anti-reflection material, 11...transparent substrate, 12...roughened layer, 20...polarizing film with roughened layer, 21...transparent substrate, 22...roughened layer, 23...first protective material, 24...polarizing substrate, 25...second protective material, 30...liquid crystal display, 31...liquid crystal panel, 32...backlight source, 33, 34...glass substrate , 33', 34'...transparent electrode surface, 35...nematic liquid crystal, 36...polarizing film, 40...liquid crystal display, 41...liquid crystal panel, 42...backlight source, 43, 44...glass substrate , 45...nematic liquid crystal, 46, 47...polarizing film, 60...light source, 61...liquid crystal panel, 62...photometer.