JP4135364B2 - Manufacturing method of optical film - Google Patents

Description

【００３２】
【表１】

【００３３】
【発明の効果】
本発明は、基材上にハードコート層を設けた光学フィルムにおいて、基材を溶解又は膨潤させる溶剤を含む樹脂を用いてハードコート層を該基材に塗布することによって、ハードコート層と基材の界面に微小な凹凸が形成されることにより、干渉ムラ防止の光学フィルムを簡便に且つ安価に提供できる。その結果、本発明の光学フィルムをディスプレイに使用した場合、従来よりも視認性を向上させることができる。
【００３４】
また、このようにして製造された光学フィルムは、ハードコート層の塗液が基材表面を溶解して塗布されているため、耐久性や密着性を通常のものよりも上がるという効果も奏する。
【図面の簡単な説明】
【図１】本発明の界面に微小な凹凸が形成された光学フィルムの断面図である。
【図２】従来の技術による光学フィルムの断面図である。
【符号の説明】
１・・・ハードコート層
２・・・基材
Ｌ・・・入射光
Ｒ₁・・・ハードコート層表面での反射光
Ｒ₂・・・界面での反射光[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical film provided with a hard coat layer on a substrate used for the purpose of protecting the surface of a display such as a liquid crystal display, a CRT display, a projection display, a plasma display, and an EL display, and a method for producing the same.
[0002]
[Prior art]
Conventionally, optical films used for various displays such as anti-reflection use active energy ray-curable resin on the substrate surface in consideration of scratch resistance, chemical resistance and weather resistance in addition to optical characteristics. A hard coat layer was often provided. However, since the refractive index of the hard coat layer obtained by this active energy ray curing is often far from the refractive index of the substrate used, as shown in FIG. Because of interference of light reflected at the interface between the hard coat layer and the substrate, rainbow-colored unevenness (interference unevenness) is generated, the visibility of the display is deteriorated, and the appearance of the display is impaired.
[0003]
For example, the resin used for the hard coat layer usually has a refractive index of about 1.5 to 1.6. On the other hand, the refractive index of the substrate is, for example, about 1.65 for polyethylene terephthalate and about 1.45 for triacetyl cellulose. Accordingly, when the interface between the hard coat layer and the substrate is clear, reflection of light at the interface occurs due to the difference in refractive index. For this reason, interference between the reflected light R _{1 on the} surface of the hard coat layer and the reflected light R ₂ at the interface occurs, resulting in rainbow-colored interference unevenness.
[0004]
Accordingly, in order to suppress this interference unevenness, a technique as disclosed in Japanese Patent Application Laid-Open No. 8-197670 or Japanese Patent Application Laid-Open No. 2000-11706 has been invented and disclosed. The technique for reducing interference unevenness described in JP-A-8-197670 is a technique for scattering light reflection at the interface between a hard coat layer and a substrate by providing irregularities on the substrate. However, before applying the hard coat layer to provide unevenness on the substrate, a step of providing unevenness on the surface of the substrate is included, and this method has the disadvantage that the number of steps increases, leading to an increase in cost. .
[0005]
In addition, the interference non-uniformity prevention technology described in Japanese Patent Application Laid-Open No. 2000-111706 is to provide an intermediate layer between the base material and the hard coat layer in order to reduce the difference in refractive index between the base material and the hard coat layer. is there. In this technique, even if an intermediate layer is provided, the refractive index changes only in stages, and interference unevenness does not disappear even if it decreases. Moreover, since the process of providing an intermediate | middle layer is needed, there existed a malfunction of leading to a cost increase.
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and an object thereof is to provide an optical film that is simple, low-cost, and free from uneven interference.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, a method for producing an optical film having a hard coat layer on the substrate, on the substrate made of cellulose acetate, a polyfunctional monomer or oligomer, a photopolymerization initiator, chloroform , A step of applying and drying a hard coat layer coating solution containing a solvent selected from methylene chloride, tetrahydrofuran, ethyl acetate, and methyl acetate and a solvent consisting of ketones, and applying and drying the hard coat layer coating solution A step of irradiating the layer with ultraviolet rays, curing the layer to form a hard coat layer, and having micro unevenness at the interface between the base material and the hard coat layer, so that there is no interference unevenness. An optical film manufacturing method is provided.
With such a configuration, an optical film free from reflection from the interface between the base material and the hard coat layer and free from uneven interference can be provided simply and inexpensively.
[0008]
Moreover , the base material provides the optical film which consists of cellulose acetate.
Polyester is inexpensive and easy to obtain, so it can provide an optical film without interference unevenness at low cost. Cellulose acetate is expensive compared to polyester, but optically has little birefringence, high transparency, and has a high haze. Since there is an advantage that it can be lowered, an optical film with good optical characteristics can be provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
An optical film having a hard coat layer formed on a substrate is shown in FIG.
As the substrate 2 for forming the optical film, films or sheets made of various organic polymers can be used. The base material usually used for optical members such as displays is a polyolefin-based (polyethylene) considering optical properties such as transparency and refractive index of light, as well as various physical properties such as impact resistance, heat resistance and durability. , Polypropylene, etc.), polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene nallate, etc.), celluloses (cellulose acetate (triacetylcellulose, diacetylcellulose, etc.), cellophane, etc.), polyamides (nylon-6, nylon-66, etc.) Etc.), organic polymers such as acrylic (PMMA, etc.), polystyrene, polyvinyl chloride, polyimide, polyvinyl alcohol, ethylene vinyl alcohol and the like are used.
[0010]
Furthermore, known additives such as antistatic agents, ultraviolet absorbers, infrared absorbers, plasticizers, lubricants, colorants, antioxidants, flame retardants and the like are added to these organic polymers to add functions. Can also be used. In addition, the base material may be a single substance or a laminate or mixture of a plurality of substances.
Moreover, the thickness of a base material can be suitably selected according to the use which uses an optical film, and 25-300 micrometers is preferable. However, the present invention is not limited to this.
[0011]
For the purpose of surface modification of the base material, the hard coat layer 1 has various properties such as scratch resistance of the optical film by steel wool rubbing test, hardness by pencil scratch test, adhesion by tape peel test, crack property by minimum bending test, etc. The resin can be selected and used so as to satisfy the required specifications.
[0012]
As the resin for forming the hard coat layer, active energy ray curable resins are often used, and polyfunctional monomers and oligomers can be used. Examples of the polyfunctional monomer include 1,4-butanediol (meth) acrylate, 1,6-hexadiol (meth) acrylate, neopentyl glycol (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di ( (Meth) acrylate, tripropylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, 3-methylpentanediol di (meth) acrylate, diethylene glycol bis β- (meth) acryloyloxypropionate, trimethylolethanetri ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (2- Roxyethyl) isocyanate di (meth) acrylate, pentaerythritol tetra (meth) acrylate, 2,3-bis (meth) acryloyloxylethyloxymethyl [2.2.1] heptane, poly 1,2-butadiene di (meth) acrylate 1,2-bis (meth) acryloyloxymethylhexane, nonaethylene glycol di (meth) acrylate, tetradecane ethylene glycol di (meth) acrylate, 10-decanediol (meth) acrylate, 3,8-bis (meth) acryloyl Oxymethyltricyclo [5.2.10] decane, hydrogenated bisphenol A di (meth) acrylate, 2,2-bis (4- (meth) acryloyloxydiethoxyphenyl) propane, 1,4-bis ((meta ) Acryloyloxymethyl Cyclohexane, hydroxypivalic acid ester neopentyl glycol di (meth) acrylate, bisphenol A diglycidyl ether (meth) acrylate, epoxy-modified bisphenol A di (meth) acrylate.
[0013]
Only one type of polyfunctional monomer may be used, or two or more types may be used in combination. Further, if necessary, it can be copolymerized with a monofunctional monomer. Examples of monofunctional monomers include acrylic esters such as N-vinylpyrrolidone, ethyl acrylate, and propyl acrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, isooctyl methacrylate, 2-hydroxyethyl methacrylate, and cyclohexyl. Examples thereof include methacrylates such as methacrylate and nonylphenyl methacrylate, derivatives such as tetrafurfuryl methacrylate, and caprolactone-modified products thereof, styrene, α-methylstyrene, acrylic acid and the like, and mixtures thereof.
[0014]
When ultraviolet rays are used for the active energy rays, it is necessary to use a photopolymerization initiator. Photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl methyl ketal and other benzoins and their alkyl ethers; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl Acetophenones such as phenyl ketone; anthraquinones such as methylanthraquinone, 2-ethylanthraquinone, 2-amylanthraquinone; thioxanthones such as thioxan, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone; benzophenone, 4,4- Benzophenones such as bismethylaminobenzophenone and azo compounds, peroxides, ketals, disulfide compounds, fluoroamines Compounds, aromatic sulfonium, and the like phosphine oxides. These can be used alone or in combination of two or more.
[0015]
Furthermore, tertiary amines such as triethanolamine and methyldiethanolamine; photoinitiators such as 2-dimethylaminoethylbenzoic acid and benzoic acid derivatives such as ethyl 4-dimethylaminobenzoate can be used in combination. I can do it. The amount of these radical polymerization initiators used is 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the polymerization component of the active energy ray-curable resin.
[0016]
Moreover, a well-known general coating additive can be mix | blended as needed. For example, a leveling agent for obtaining a good coated surface and a silicone-based or fluorine-based lubricant for imparting slip properties are examples. Appropriate amounts of these additives are 0.01 to 1 part by weight per 100 parts by weight of the active energy ray-curable resin.
[0017]
When the polyfunctional or monofunctional monomer is applied on a substrate, it can be diluted with a solvent to form a coating solution. In the present invention, it is necessary to select a solvent having the property of dissolving or swelling the substrate. This is because, when such a solvent is used when adjusting the coating liquid, the resin layer is formed while dissolving the substrate immediately after coating, so that it is possible to discontinuously form minute irregularities at the interface. Because. For example, when polyethylene terephthalate is used as the base material, it is relatively stable against organic solvents, but phenol, nitrobenzene, chlorophenol, chlorobenzene, hexafluoroisopropanol, etc., and when the base material is triacetyl cellulose. include chloroform, methylene chloride, tetrahydrofuran, ethyl acetate, a solvent such as acetic acid methylation is suitable.
[0018]
As described above, the solvent is selected in consideration of the combination of dissolving or swelling the base material, the stability of the composition, the wettability with respect to the base material, volatility, etc., and methanol, ethanol, isopropyl alcohol, butanol, 2-methoxy Alcohols such as ethanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl, ketone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethers such as diisopropyl ether, ethylene glycol, propylene glycol, hexylene glycol, etc. Glycols such as glycol ethers, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, etc., aliphatic hydrocarbons such as hexane, heptane, octane, etc., aromatics such as halogenated hydrocarbons, benzene, toluene, xylene Hydrocarbons, N- methylpyrrolidone, dimethylformamide or the like can be used.
[0019]
Moreover, not only one type but also two or more types of diluent solvents can be mixed and used. Further, when the resin itself has a relatively low viscosity and has a property of dissolving or swelling the base material, it may not be necessary to use a solvent. Moreover, it can also be used by mixing with a solvent that is stable with respect to the substrate.
[0020]
In this way, the resin, additives, solvent, and, if necessary, the photopolymerization initiator are mixed and stirred to obtain a hard coat layer coating solution. As a method of applying this coating liquid to a substrate, wet coating methods such as gravure coating method, roll coating method, reverse coating method, die coating method, knife coating method, wire bar coating method, dip coating method, spray coating method are used. And an air knife coating method, a curtain coating method, etc., are applied to a desired thickness. Thereafter, the solvent component is evaporated by a dryer, and a resin layer is formed on the substrate. If the thickness is too thick, curling or cracking may occur, and if it is too thin, the desired hardness cannot be obtained. Therefore, it is usually about 1 to 20 μm, preferably 2 to 10 μm. It is thickness.
Here, the solvent for dissolving the base material is put in the coating liquid for the hard coat layer, but a method for applying the solvent for dissolving the base material in advance immediately before applying the coating liquid for the hard coat layer is taken. Is also possible.
[0021]
Thus, the active energy ray used for hardening of the resin layer which apply | coated and dried the hard-coat layer coating liquid on the base material uses an electromagnetic wave and a particle beam. In general, ultraviolet rays are often used for electromagnetic waves, and electron beams are often used for particle beams.
As the ultraviolet light source, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, or a metal halide lamp can be used. Moreover, although there exist an electroded lamp and an electrodeless lamp as a form of a lamp | ramp, either may be used. Dose of ultraviolet light varies with the resin composition and the film thickness of the hard coat layer is cured, it is suitably 100~5000mJ / cm ² and preferably 500~2000mJ / cm ^2.
[0022]
Furthermore, the space to be cured when ultraviolet irradiation is performed may be replaced with nitrogen gas. Substitution with nitrogen has an effect of suppressing oxygen inhibition during curing of the resin, and in particular, the crosslink density at the outermost surface of the resin layer can be increased, and the surface hardness is improved.
[0023]
In the case of curing using an electron beam, 50 to 1000 KeV emitted from various electron beam accelerators such as a Cockloftwald type, a bandegraph type, a resonance transformation type, an insulating core transformation type, a linear type, a dynamitron type, and a high frequency type. An electron beam having the following energy can be used.
[0024]
As shown in FIG. 1, the optical film formed in this way discontinuously forms minute irregularities at the interface between the hard coat layer and the substrate. Therefore, the reflected light R ₂ at the interface is irregularly reflected, and interference with the reflected light R ₁ on the hard coat layer surface does not occur. Therefore, the obtained optical film is very excellent in visibility.
[0025]
【Example】
Hereinafter, examples will be described in detail, but the present invention is not limited to the examples.
<Example 1>
Using polyethylene terephthalate with a thickness of 188 μm as a substrate,
Pentaerythritol triacrylate 5 parts by weight Dipentaerythritol hexaacrylate 5 parts by weight Irgacure 184 0.3 part by weight Methyl ethyl ketone 9 parts by weight Hexafluoroisopropanol 1 part by weight was stirred and mixed, and a WET film thickness of 10 μm was obtained by gravure coating. It was applied and dried so as to have a DRY film thickness of 5 μm after drying, and a hard coat layer was formed by irradiating with 1000 mJ of ultraviolet light with a high-pressure mercury lamp, and an optical film was produced.
[0026]
【Example】
Hereinafter, examples will be described in detail, but the present invention is not limited to the examples.
< Reference Example 1>
Using polyethylene terephthalate with a thickness of 188 μm as a substrate,
Pentaerythritol triacrylate 5 parts by weight
Dipentaerythritol hexaacrylate 5 parts by weight
Irgacure 184 0.3 parts by weight
9 parts by weight of methyl ethyl ketone
A coating solution in which 1 part by weight of hexafluoroisopropanol is stirred and mixed is applied and dried to a WET film thickness of 10 μm (DRY film thickness after drying of 5 μm) by a gravure coating method, and irradiated with 1000 mJ of ultraviolet light from a high-pressure mercury lamp. A hard coat layer was formed to produce an optical film.
[0027]
<Example>
Using triacetyl cellulose with a thickness of 80 μm as a base material,
Pentaerythritol triacrylate 5 parts by weight
Dipentaerythritol hexaacrylate 5 parts by weight
Irgacure 184 0.3 parts by weight
5 parts by weight of methyl ethyl ketone
A coating solution obtained by stirring and mixing 5 parts by weight of methyl acetate is applied and dried to a WET film thickness of 10 μm (DRY film thickness after drying of 5 μm) by a gravure coating method, and irradiated with 1000 mJ ultraviolet light from a high-pressure mercury lamp. A coating layer was formed to produce an optical film.
[0028]
< Reference Example 2>
Using polyethylene terephthalate with a thickness of 188 μm as a substrate,
Pentaerythritol triacrylate 5 parts by weight
Dipentaerythritol hexaacrylate 5 parts by weight
Irgacure 184 0.3 parts by weight
A coating solution obtained by stirring and mixing 10 parts by weight of methyl ethyl ketone is applied and dried to a WET film thickness of 10 μm (DRY film thickness after drying of 5 μm) by a gravure coating method, and 1000 mJ ultraviolet rays are irradiated with a high-pressure mercury lamp and hard-coated. Layers were formed to produce an optical film.
[0029]
<Comparative example>
Using triacetyl cellulose with a thickness of 80 μm as a base material,
Pentaerythritol triacrylate 5 parts by weight
Dipentaerythritol hexaacrylate 5 parts by weight
Irgacure 184 0.3 parts by weight
A coating solution obtained by stirring and mixing 10 parts by weight of methyl ethyl ketone is applied and dried to a WET film thickness of 10 μm (DRY film thickness after drying of 5 μm) by a gravure coating method, and 1000 mJ ultraviolet rays are irradiated with a high-pressure mercury lamp and hard-coated. Layers were formed to produce an optical film.
[0030]
Pencil hardness: evaluated based on the test method shown in JIS K5401.
Scratch resistance: Using a # 0000 steel wool, it was rubbed back and forth 10 times while applying a load of 250 g / cm 2, and the presence or absence of scratches was evaluated.
Adhesiveness: After the surface of the hard coat layer was cut at 100 points of 1 mm square, it was adhered with a cellophane tape [manufactured by Nichiban Co., Ltd., industrial 24 mm width adhesive tape], then the cellophane tape was peeled off, and the number of peels was evaluated.
Appearance: The opposite surface of the optical film on which the hard coat layer was formed was rubbed with sandpaper, then a matte black paint was applied, and the optical film was observed from the hard coat layer forming side.
[0031]
[Table 1]

[0032]
[Table 1]

[0033]
【The invention's effect】
In the optical film in which a hard coat layer is provided on a substrate, the hard coat layer and the substrate are coated with the hard coat layer using a resin containing a solvent that dissolves or swells the substrate. By forming minute irregularities on the interface of the material, an optical film for preventing interference unevenness can be provided simply and inexpensively. As a result, when the optical film of the present invention is used for a display, visibility can be improved as compared with the conventional case.
[0034]
In addition, the optical film produced in this way also has an effect of improving durability and adhesiveness more than usual because the hard coat layer coating solution is applied by dissolving the substrate surface.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical film in which minute irregularities are formed at an interface of the present invention.
FIG. 2 is a cross-sectional view of a conventional optical film.
[Explanation of symbols]
Reflected light at R ₂ ... interfaces at 1 ... hard coat layer 2 ... substrate L ... incident light R ₁ ... hard coat layer surface

Claims (2)

A method for producing an optical film provided with a hard coat layer on a substrate,
A hard material containing a polyfunctional monomer or oligomer, a photopolymerization initiator, a solvent selected from chloroform, methylene chloride, tetrahydrofuran, ethyl acetate, and methyl acetate on a substrate made of cellulose acetate, and a solvent made of ketones Applying and drying a coating layer coating solution; and
Applying the hard coat layer coating solution, irradiating the dried layer with ultraviolet rays, curing the layer to form a hard coat layer, and forming fine irregularities on the interface between the substrate and the hard coat layer. There is no interference unevenness and there is no interference unevenness. In the coating and drying step, the hard coat layer coating solution is applied so that the thickness of the hard coat layer after curing is 2 to 10 μm;
In the ultraviolet irradiation method of manufacturing an optical film according to claim 1, wherein the irradiation amount of the ultraviolet rays, characterized in that in the range of 500~2000mJ / cm ^2.

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