TWI491907B - Optical film - Google Patents

Description

Optical film

The present invention relates to an optical film, and more particularly to an optical film which is suitable as a polarizing plate or a touch panel, has excellent wear resistance, and has good image clarity and moderate protection. Dizziness.

In a display such as a brown tube (CRT) or a liquid crystal display (LCD) or a plasma display (PDP), light is incident on the screen from the outside, and the reflection of the light makes the display image difficult to see, especially in recent years accompanied by a large display. To solve the above problems, it has become an important issue. One of the means for solving this problem is exemplified by using a member having an antiglare hard coat layer. Next, the method for forming the anti-glare hard coat layer is roughly classified into three types: (1) a method of physically roughening the surface when hardening a hard coat layer is formed, and (2) forming a hard coat layer. The hard coating agent is mixed with the filler, and (3) the hard coating agent for forming a hard coat layer is mixed with the non-miscible two components, and the phase separation method is utilized. All of these methods suppress the regular reflection of external light by forming fine irregularities on the surface, and prevent glare of external light such as a fluorescent lamp. In these cases, the method of mixing the filler into the hard coating agent in (2) is the mainstream. In the case of a filler, inorganic fine particles represented by conventional cerium oxide are generally used. In the reason of using the cerium oxide particles, the whiteness of the hard-coated film obtained can be suppressed to be low, and the abrasion resistance due to insufficient hardening of the hard coat layer is not caused.

On the one hand, in the case of using organic fine particles as a filler, for example, Patent Document 1 discloses an abrasion-resistant antiglare film which forms a resin bead and ionization from a refractive index of 1.40 to 1.60 on a transparent substrate. An anti-glare layer which is essentially composed of a radiation-curable resin composition, and an anti-glare film disclosed in Patent Document 2 is a transparent base film; and two or more kinds of light-transmitting particles are contained in the light-transmitting resin. The anti-glare layer is formed, and the difference between the refractive index of the light-transmitting fine particles and the light-transmitting resin is 0.03 or more and 0.20 or less, and the surface of the anti-glare layer is formed by the two or more kinds of light-transmitting fine particles. A concave-convex shape is formed.

As a result, various anti-glare films have been studied so far, but the purpose is to provide an anti-glare hard coat layer in order to make the image developed from the screen clearly visible. The anti-glare hard coat layer has a diffusing property due to the unevenness of the surface thereof, and as a result, the image clarity is lowered and the visibility is lowered.

Advanced technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open No. Hei 6-18706

Patent Document 2 Japanese Patent No. 3515401

The present invention is an invention completed under such circumstances, and an object thereof is to provide an optical film which is excellent as a polarizing plate or a touch panel, has excellent abrasion resistance, and has good image clarity and moderate anti-glare. Sex.

The present inventors have repeatedly studied in order to achieve the object, and as a result, it has been found that, on at least one side of the transparent base film, a coating composition containing an active energy ray-curable compound and organic fine particles is formed to form a hard The coating layer and the external haze value and the internal haze value of the hard coat layer are set to a specific range, and the 60° specular gloss ratio is set to a specific range, thereby achieving the object of the invention. The present invention has been accomplished in light of such insights.

That is, the present invention provides:

(1) An optical film characterized in that a hard coat layer is formed on at least one side of a transparent base film by a coating composition containing an active energy ray-curable compound and organic fine particles, and the outer portion of the hard coat layer is formed The haze value is 7% or less, the internal haze value is 1 to 12%, and the 60° specular gloss ratio is 100 to 150.

(2) The optical film of item (1) above, wherein the hard coat layer has a thickness of 7 to 20 μm;

(3) The optical film of the above item (1) or (2), wherein the average particle diameter of the organic fine particles is smaller than the thickness of the hard coat layer;

(4) The optical film according to any one of the above (1) to (3), wherein the low refractive index layer is further laminated on the hard coat layer;

(5) The optical film according to any one of the above items (1) to (4), which is formed by laminating an adhesive layer on a surface of the transparent base film on which the hard coat layer is not formed;

(6) The optical film according to any one of the above (1) to (4), which is formed by laminating a hard coat layer on a surface of the transparent base film on which the hard coat layer is not formed.

Further, preferred embodiments of the optical film of the present invention may be exemplified by:

(a) an optical film having a total image resolution of 300 or more slits;

(b) an optical film containing 1 to 15 parts by mass of the spherical particles having an average particle diameter of 1 to 15 μm with respect to 100 parts by mass of the hardening resin in the hard coat layer;

(c) an optical film having a specific gravity of the active energy ray-curable compound at a temperature of 25 ° C which is greater than the specific gravity of the organic fine particles by 0.15 or more;

(d) an optical film having a refractive index of 1.43 or less and a thickness of 50 to 200 nm of the low refractive index layer of the above (4), and

(e) An optical film for a touch panel or a polarizing plate.

According to the present invention, there is provided an optical film which sets a 60° specular gloss rate to a specific range while setting an external haze value and an internal haze value of at least one surface of a transparent substrate film to a specific range. It is extremely suitable as a polarizing plate or a touch panel, and is excellent in abrasion resistance, and has good image clarity and moderate anti-glare property.

Form of implementing the invention

The optical film of the present invention forms a hard coat layer on at least one side of the transparent base film by a coating composition containing an active energy ray-curable compound and organic fine particles, and the external haze value and the inside of the hard coat layer are formed. The haze value was set to the range shown below, and the 60° specular gloss ratio was set to the range shown below.

[paint composition]

The coating composition of the present invention contains an active energy ray-curable compound and organic fine particles.

(active energy ray-hardening compound)

In the active energy ray-curable compound, a polyfunctional (meth) acrylate monomer and/or a (meth) acrylate prepolymer is used.

Further, in the present invention, the active energy ray means an energy quantum having an electromagnetic wave or a charged particle ray, that is, an ultraviolet ray or an electron beam.

<Polyfunctional (meth)acrylate monomer and/or (meth)acrylate prepolymer>

The polyfunctional (meth)acrylate monomer may, for example, be 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate or the like. Neopentyl glycol (meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl (meth)acrylate, Caprolactone modified dicyclopentene di(meth)acrylate, ethylene oxide modified di(meth)acrylate, allylated cyclohexyl di(meth)acrylate, isomeric cyanide Acid di(meth)acrylate, trimethylolpropyl tri(meth)acrylate, dineopentaerythritol tris(meth)acrylate, propionic acid modified trispentaerythritol Ester, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropyl tris(meth)acrylate, hexamethyleneoxyethyl isomeric cyanurate, propionic acid Modification of polyfunctionality such as dipentaerythritol penta(meth)acrylate, dineopentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate (Meth) acrylate. These monomers may be used alone or in combination of two or more.

On the other hand, the (meth)acrylate prepolymer may, for example, be a polyester acrylate type, an epoxy acrylate type, a urethane acrylate type, or a polyalcohol acrylate type. Here, as the polyester acrylate-based prepolymer, (meth)acrylic acid esterification can be exemplified by a hydroxyl group of a polyester oligomer having a hydroxyl group at both terminals obtained by condensing a polyvalent carboxylic acid and a polyvalent alcohol. Or obtained by esterifying a hydroxyl group at the terminal of the oligomer obtained by adding an alkylene oxide to a polyvalent carboxylic acid, and (meth)acrylic acid.

An epoxy acrylate-based prepolymer, for example, by reacting (meth)acrylic acid on an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or a novolak type epoxy resin Obtained. The urethane acrylate-based prepolymer may be exemplified by a (meth) acrylate by a polyurethane oligomer obtained by reacting a polyether polyol or a polyester polyol with a polyisocyanate. obtain. Further, the polyhydric acrylate prepolymer can be obtained by esterifying a hydroxyl group of a polyether polyol with (meth) acrylate. These prepolymers may be used singly or in combination of two or more kinds, or may be used in combination with the polyfunctional (meth) acrylate monomer.

In the present invention, as the active energy ray-curable compound, the above-described cerium oxide-based fine particles can be used in combination with the polyfunctional (meth) acrylate monomer and/or the (meth) acrylate-based prepolymer.

<cerium oxide particles>

As the cerium oxide-based fine particles, colloidal cerium oxide fine particles and/or cerium oxide fine particles having surface functional groups can be used.

The colloidal cerium oxide microparticles have an average particle diameter of about 1 to 400 nm, and further, cerium oxide microparticles having a surface functional group, for example, a surface functional group, may be cerium oxide microparticles having a (meth) acrylonitrile group. (hereinafter referred to as reactive cerium oxide microparticles).

The reactive cerium oxide microparticles may, for example, be a stanol group on the surface of the cerium oxide microparticles having an average particle diameter of about 0.005 to 1 μm, and a polymerizable unsaturated group having a functional group reactive with the stanol group. Obtained by the reaction of an organic compound. The polymerizable unsaturated group may, for example, be a radically polymerizable (meth) acrylonitrile group.

As such a compound, for example, acrylic acid, chloro acrylate, 2-isocyanatoethyl acrylate, glycidyl acrylate, 2,3-iminopropyl acrylate, 2-hydroxyethyl acrylate, propylene propylene oxide can be used. A trimethoxane or the like, and a methacrylic acid derivative corresponding to an acrylic acid derivative. These acrylic acid derivatives or methacrylic acid derivatives may be used singly or in combination of two or more.

The cerium oxide fine particles obtained by combining the organic compound containing a polymerizable unsaturated group and the active energy ray-hardening component are crosslinked and hardened by irradiation with an active energy ray.

The reactive cerium oxide fine particles have an effect of improving the abrasion resistance of the obtained optical film.

Such an active energy ray-curable compound contains a compound obtained by binding an organic compound having a polymerizable unsaturated group to cerium oxide fine particles, and is commercially available, for example, under the trade name "opstar Z7530". "opstar Z7524", "opstar TU4086", etc.

In the present invention, the content of the cerium oxide-based fine particles is usually from about 5 to 90% by mass in the solid content of the active energy ray-curable compound (cerium oxide-containing fine particles). It is preferably from 10 to 70% by mass.

(organic particles)

The organic fine particles used in the coating composition of the present invention may, for example, be argon-based fine particles, melamine-based resin fine particles, or acrylic resin fine particles (for example, polymethyl methacrylate-based fine particles (hereinafter referred to as PMMA-based fine particles). ), acrylic acid-styrene copolymer fine particles, polycarbonate fine particles, polyethylene fine particles, polystyrene fine particles, benzoguanamine resin fine particles, and the like. Further, the shape of the organic fine particles used in the present invention is not limited, and from the viewpoint of improving the reproducibility of the antiglare property, it is preferable that the spherical material can homogenize the light scattering state. Further, from the same viewpoint, the organic fine particles are particularly excellent in a narrow particle size distribution. The average particle diameter of the organic fine particles is preferably from 1 to 15 μm, particularly preferably from 2 to 5 μm from the viewpoint of antiglare property, and, from the same viewpoint, the particle size distribution is measured by Coulter particle size analyzer (coulter) It is preferable that the mass fraction of the particle diameter of ±55% or more of the peak top value measured by the counter method) is 70% or more of the total mass.

In the present invention, the organic fine particles may be used alone or in combination of two or more.

Moreover, from the viewpoint of exhibiting anti-glare performance, 100 parts by mass of the solid component of the active energy ray-curable compound (in the case where cerium oxide-based fine particles are used) is preferably used. It is contained in an amount of 0.1 part by mass or more. Moreover, from the viewpoint of suppressing the external haze value of the obtained optical film to 7% or less, the solid component 100 of the active energy ray-curable compound (which is also contained in the case of using ceria-based fine particles) The content of the organic fine particles is preferably 15 parts by mass or less. From such a viewpoint, the content of the organic fine particles per 100 parts by mass of the solid component of the active energy ray-curable compound (in the case where the cerium oxide-based fine particles are used) is preferably from 1 to 10 parts by mass. It is preferably 2 to 7 parts by mass.

In the present invention, in order to disperse the organic fine particles in the vicinity of the surface of the hard coat layer and to improve the antiglare property, the active energy ray-curable compound is preferably contained at a temperature of 25 ° C (in the case of using lanthanoid particles) The specific gravity of the compound) is preferably 0.15 or more larger than the specific gravity of the organic fine particles. As long as the specific gravity difference is less than 0.15, the ratio of the organic fine particles existing in the vicinity of the surface of the hard coat layer is lowered, and it is difficult to obtain desired antiglare performance. The difference in specific gravity is more preferably 0.20 or more, and still more preferably 0.25 or more.

Further, when the difference in specific gravity is too large, the floating volume of the organic fine particles from the surface of the hard coat layer becomes excessively large, and as a result, the uneven shape of the surface of the hard coat layer becomes excessively large, and the specular gloss ratio of 60° is less than 100. Therefore, the specific gravity difference is preferably less than 0.40, more preferably less than 0.38, still more preferably less than 0.35.

Further, the specific gravity of the active energy ray-curable compound at a temperature of 25 ° C is a value measured by a specific gravity measuring method of a pycnometer of JIS Z 8804, which is a material which is hardened by irradiation with an energy ray. Further, the specific gravity of the organic fine particles at a temperature of 25 ° C is a measured value of a specific gravity measuring method by a pycnometer of JIS Z 8807-1976.

On the one hand, in order to achieve the reduction of the anti-glare property due to the reduction of the external haze value in the technical idea of the present invention, it is preferable to set the active energy ray-curable compound (in the case of using a cerium oxide system). In the case of fine particles, the refractive index difference between the compound and the organic fine particles is a certain value or more. That is, the difference in refractive index is preferably from 0.02 to 0.5, particularly preferably from 0.03 to 0.1. When the difference in refractive index is 0.02 or more, the internal haze value can be made 1% or more, and if the difference in refractive index is 0.5 or less, the internal haze value can be suppressed to 12% or less.

Further, the refractive index of the organic fine particles is a calculated value from the refractive index of the contained monomer and the mass ratio according to the composition of the monomer. Further, the refractive index of the active energy ray-curable compound is a measured value of JIS K 7142 which is hardened by irradiation with an active energy ray.

(photopolymerization initiator)

The coating composition of the present invention may contain a photopolymerization initiator as desired. The photopolymerization initiator may, for example, be benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoethyl benzene, 2, 2 -dimethoxy-2-phenylethyl benzene, 2,2-diethoxy-2-phenyl acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl benzophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy) Phenyl-2(hydroxy-2-propyl)one, benzophenone, p-benzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylhydrazine, 2 - acetamidine, 2-tertiary butyl hydrazine, 2-amine hydrazine, 2-methyl 9-oxo sulphur 2-ethyl 9-oxosulfur 2-chloro 9-oxosulfur 2,4-dimethyl 9-oxosulfur 2,4-diethyl 9-oxosulfur Benzyl ketal, acetophenone ketal, p-dimethylamine benzoate and the like.

These may be used singly or in combination of two or more kinds, and the amount thereof is usually in the range of 0.2 to 10 parts by mass based on 100 parts by mass of the total active energy ray-curable compound. Here, the fully active energy ray-curable compound means that the compound is contained when the reactive cerium oxide fine particles are used in the case of the cerium oxide-based fine particles.

(antistatic agent)

The coating composition of the present invention may contain an antistatic agent as desired. By containing an antistatic agent, dust adhesion of the optical film can be prevented, and the visibility of the optical film can be further improved.

Examples of the antistatic agent include tin oxide, antimony-doped tin oxide (ATO), indium oxide, tin-doped indium oxide (ITO), zinc oxide, aluminum-doped zinc oxide, zinc antimonate, and five. Various cationic compounds having a cationic group such as metal oxide particles such as cerium oxide, a quaternary ammonium salt, a pyridinium salt, or a primary to tertiary amino group; a sulfonic acid base, a sulfate base, a phosphate base, a phosphonic acid base, etc. An anionic compound having an anionic group, an amphoteric compound such as an amino acid or an amine sulfate, a nonionic compound such as an amino alcohol, a glycerin or a polyethylene glycol, or an alkoxide of tin and titanium The organometallic compound and the metal chelate compound such as the ethyl acetoacetoxyacetate salt.

The above antistatic agent can be used in an appropriate amount in an appropriate range without departing from the scope of the invention.

(modulation of coating composition)

The coating composition used in the present invention may be added with the active energy ray-curable composition, the organic fine particles, and the desired cerium oxide particles in a predetermined ratio, and photopolymerization may be added in a suitable solvent as needed. The agent, the antistatic agent or various additional components such as an antioxidant, a UV absorber, a decane coupling agent, a light stabilizer, a leveling agent, an antifoaming agent, etc., are prepared by dissolving or dispersing them.

The solvent to be used in this case may, for example, be an aliphatic hydrocarbon such as hexane or heptane, an aromatic hydrocarbon such as toluene or xylene, a halogenated hydrocarbon such as dichloromethane or chlorinated ethylene, or methanol, ethanol or propanol. An alcohol such as butanol or propylene glycol monomethyl ether, a ketone such as acetone, methyl ethyl ketone, 2-pentanone, isophorone or cyclohexanone, an ester such as ethyl acetate or butyl acetate, or ethyl cellosolve. The cellosolve is a solvent or the like.

The concentration and viscosity of the coating composition to be prepared are not particularly limited as long as they can be applied, and can be appropriately selected depending on the conditions.

[Transparent substrate film]

In the optical film of the present invention, a hard coat layer is formed on at least one side of the transparent base film by using a hard coat layer forming material prepared as described above.

The transparent base film is not particularly limited, and can be suitably selected from conventionally known plastic films which are optical hard coat film substrates. The plastic film may, for example, be a polyester film such as polyethylene terephthalate, polybutylene terephthalate or polyethylene naphthalate, a polyethylene film, a polypropylene film, or cellophane. , diethyl phthalocyanine film, triethylene fluorene cellulose film, acetonitrile cellulose butyrate film, polyvinyl chloride film, polyvinyl chloride film, polyvinyl alcohol film, ethylene-vinyl acetate film , polystyrene film, polycarbonate film, polymethylpentene film, polyfluorene film, polyetheretherketone film, polyether fluorene film, polyether quinone film, polyimide film, fluororesin film, A plastic film such as a polyamide film, an acrylic resin film, a norbornene resin film, or a cycloolefin resin film.

These base film may be colored or not colored, and may be appropriately selected depending on the application. For example, when used for protection of a liquid crystal display, a colorless transparent film is suitable.

The thickness of the base film is not particularly limited and may be appropriately selected depending on the situation, but is usually in the range of 15 to 300 μm, preferably 30 to 200 μm. Further, in order to improve the adhesion between the base film and the layer provided on the surface thereof, the base film may be subjected to a surface treatment by an oxidation method or a roughening method depending on whether it is on one side or both sides. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid treatment (wet type), flame treatment, hot air treatment, ozone ‧ ultraviolet irradiation treatment, and the like, and the embossing method may, for example, blasting ( Sand blast) method, solvent treatment method, and the like. These surface treatment methods can be appropriately selected depending on the type of the plastic film to be used as the base film. However, in general, from the viewpoints of effects and workability, it is preferred to use a corona discharge treatment method. Further, an undercoat layer may also be provided.

[Formation of hard coating]

Coating the coating composition on at least one surface of the transparent base film by a conventionally known method such as a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like After forming a coating film, after drying, the active energy ray is irradiated to harden the coating film to form a hard coating layer.

The active energy ray may, for example, be an ultraviolet ray or an electron beam. The irradiation amount of the ultraviolet light obtained by a high pressure mercury lamp, an electrodeless lamp, a metal halide lamp, a xenon lamp or the like is usually 100 to 500 mJ/cm ² . On the one hand, the electron beam can be obtained by an electron beam accelerator or the like, and the irradiation amount is usually 150 to 350 kV. . Among these active energy rays, ultraviolet rays are particularly preferred. Further, when an electron beam is used, a cured film can be obtained without adding a photopolymerization initiator.

The thickness of the hard coat layer thus formed must be larger than the average particle diameter of the organic fine particles used in the present invention, and therefore is preferably from 7 to 20 μm, more preferably from 10 to 15 μm.

By making the film thickness of the hard coat layer larger than the average particle diameter of the organic fine particles, the organic fine particles are not in surface contact with the transparent base film in the hard coat layer, and are fixed in a so-called floating state, so that the uneven surface is made At the same time of homogenization, the concavities themselves can also be moderately inclined. As a result, it is extremely effective from the viewpoint that the external haze value of the obtained optical film is 7% or less and the 60° specular gloss ratio is 100 or more.

From such a viewpoint, the film thickness of the hard coat layer is preferably 1.5 times or more, more preferably 2.0 times or more, of the average particle diameter of the organic fine particles. When the internal haze value of the optical film obtained is set to be 1% or more, the film thickness is preferably less than 10 times with respect to the average particle diameter.

[Optical film]

(optical properties)

As described above, the optical film of the present invention has excellent optical image clarity and moderate anti-glare property because the hard coat layer has the optical characteristics shown below.

From the viewpoint of image sharpness and visibility, the external haze value of the hard coat layer is 7% or less, and from the viewpoint of anti-glare property, it is preferably 1.0% or more, more preferably 3.5 to 5.0%. On the one hand, the internal fog value is from 1 to 12%, preferably from 5 to 12%, more preferably from 8 to 12%, from the viewpoint of maintaining image clarity on one side and improving anti-glare property.

Further, the internal haze value indicates a haze value caused only by internal light scattering, and the outer surface haze value refers to a haze value caused only by light scattering due to surface unevenness, and the total haze value indicates the internal haze value and external fog. The sum of the values. Further, the total haze value corresponds to the value of the haze value of JIS K 7136 of the transparent base film unit of the constituent member of the optical film minus the haze value defined by JIS K 7136 of the optical film.

The calculation method of the internal fog value, the external fog value, and the total fog value is described below.

<Calculation of internal haze value, external haze value and total haze value of hard coating layer>

First, the haze value of the optical film of the present invention and the haze value of the transparent substrate film monomer were measured in accordance with JIS K 7136.

The total haze value is the value obtained by subtracting the haze value of the transparent substrate film monomer from the haze value of the optical film.

Next, a transparent adhesive sheet having a thickness of 20 μm was adhered to the hard coat layer side of the optical film as a sample for calculating the internal haze value. The haze value of the transparent adhesive sheet and the haze value of the internal haze value calculation sample were measured in accordance with JIS K 7136.

Next, the internal haze value of the hard coat layer of the optical film was calculated by subtracting the haze value of the transparent adhesive sheet and the haze value of the transparent base film unit from the haze value of the internal haze value calculation sample.

Finally, the internal fog value is subtracted from the total fog value as the external fog value.

In addition, the haze value of the transparent adhesive sheet is as described above, and is subtracted during the calculation, so that there is no direct influence on the internal haze value, the external haze value, and the total haze value, and there is no particular limitation, but the viewpoint of improving the measurement accuracy is improved. It is better to use a haze value of less than 5%.

In the optical film of the present invention, the 60° specular gloss ratio measured in accordance with JIS K 7105 is in the range of 100 to 150, preferably 100 to 140, more preferably 120 to 130.

In the conventional optical film having anti-glare property, the 60° specular gloss ratio is preferably 80 or less, and it is considered that the 60° specular gloss ratio of the present invention is too high, and it is not suitable as an anti-glare film. However, from the viewpoint of designing the external haze value and the internal haze value within the above range, if the 60° specular gloss ratio is designed to be in the above range, it is possible to design the antiglare property in the vertical direction which can be visually confirmed by the human body without any The level of the problem is apparent, and an optical film excellent in anti-glare property can be obtained.

Further, the image clarity of the five types of slits measured in accordance with JIS K 7374 is usually 300 or more, preferably 300 to 350, and more preferably 320 to 350. As a result, the optical film of the present invention has high image clarity and excellent visibility.

Further, the total light transmittance measured in accordance with JIS K 7136 is usually 90% or more.

In addition, the details of the measurement methods of the above optical characteristics will be described later.

(surface resistivity)

The optical film of the present invention is preferably a surface resistivity of 5 × 10 ⁹ Ω/□ or less as measured in accordance with JIS K 6911. By the surface resistivity, adhesion of dust can be prevented, and the visibility of the optical film of the present invention can be maintained for a long period of time. Further, the lower limit is not particularly limited, and is usually 1 × 10 ⁷ Ω/□ or more.

(effect)

Further, a better constitution of the optical film of the present invention and its effects are as follows.

(1) In the present invention, by using a coating composition in which the external haze value and the internal haze value of the hard coat layer and the 60° specular gloss ratio are adjusted to the above range, a hard coat layer is formed, and it can be obtained as a polarizing plate or An optical film that is extremely suitable for touch panels and has both image clarity and moderate anti-glare properties.

(2) By setting the active energy ray-curable compound, the specific gravity of the organic fine particles is inferior to a specific range, and the organic fine particles are unevenly dispersed in the vicinity of the surface of the hard coat layer to exhibit desired antiglare performance. By controlling the difference in specific gravity, the external haze value and the 60° specular gloss rate can be controlled to a desired value.

(3) By setting the specific gravity difference to a specific range, in the film thickness larger than the average particle diameter of the organic fine particles, organic fine particles may be present in the vicinity of the surface of the hard coat layer, and the anti-glare property can be improved while obtaining no Uneven homogenized uneven surface.

(4) By using an active energy ray-curable compound containing cerium oxide-based fine particles, an optical film having a low degree of curing shrinkage and little curling can be obtained. Further, when an active energy ray-curable compound containing cerium oxide-based fine particles is used, the difference in specific gravity from the organic fine particles can be designed to increase.

(other functional layers)

In the optical film of the present invention, a low refractive index layer as an antireflection layer may be provided on the hard coat layer as needed, and the low refractive index layer is preferably from a refractive index of 1.43 or less, and has a thickness of A layer of about 50 to 200 nm.

By providing the anti-reflection layer, it is possible to cancel the phenomenon of reflection of the image by reflection by sunlight, a fluorescent lamp, or the like, and to improve the total light transmittance and visibility by suppressing the reflectance of the surface. Further, antistatic properties can be improved in response to the type of the antireflection layer.

Further, in the optical film of the present invention, a hard coat layer may be laminated as needed on the side of the hard coat layer on which the transparent base film is not formed. The hard coat layer is generally preferably a glossy hard coat.

The glossy hard coat layer is a polyfunctional (meth) acrylate monomer and/or a (meth) acrylate prepolymer as an active energy ray-curable compound, and may contain a photopolymerization initiator as needed. The bright-surface hard coat forming material can be formed by coating a predetermined surface of the transparent base film by a conventionally known method, drying it, and then curing it by irradiating an active energy ray, preferably by irradiation with ultraviolet rays.

The polyfunctional (meth)acrylate monomer, the (meth)acrylate prepolymer, and the photopolymerization initiator are as shown in the description of the coating composition described above. Further, the above-mentioned bright surface hard coat forming material may contain various additive components as needed.

The thickness of the glossy hard coat layer is usually about 2 to 10 μm, preferably 3 to 6 μm.

(adhesive layer)

In the optical film of the present invention, an adhesive layer for adhering to an adherend such as a liquid crystal display can be formed on the surface of the hard coat layer on which the transparent base film is not formed. As the adhesive constituting the pressure-sensitive adhesive layer, for example, an acrylic pressure-sensitive adhesive, an urethane-based pressure-sensitive adhesive, or a polyoxynoxy-based pressure-sensitive adhesive which is suitable for optical use is preferably used. The thickness of the adhesive layer is usually in the range of 5 to 100 μm, preferably 10 to 60 μm.

Further, on the adhesive layer, a release sheet can be provided as needed. The release sheet may be coated with a release agent such as a polyoxymethylene resin or the like on various plastic films such as polyethylene terephthalate or polypropylene. The thickness of the release sheet is not particularly limited, but is usually about 20 to 150 μm.

The optical film forming such an adhesive layer is suitably used for a display such as a CRT, an LCD, or a PDP, and can be provided with an anti-glare property or an abrasion-resistant property, and is particularly suitable for use in a polarizing plate for LCD or the like.

Example

Next, the present invention will be described in detail by way of examples, but the invention is not limited to the examples.

Further, the average particle diameter and specific gravity of the organic fine particles, the specific gravity of the active energy ray-curable compound, and the performance of the optical film are determined by the following methods.

<Organic Particles>

(1) Average particle size

Using a Coulter Particle Size Analyzer [manufactured by Beckman Coulter Co., Ltd., device name "Multisizer 3"], a dispersion of 0.5% ion-exchanged water was measured at 25 ° C by a Coulter Particle Size Analyzer method.

(2) Specific gravity at a temperature of 25 ° C

Determination of specific gravity according to the pycnometer of JIS Z 8807-1976.

<Active energy ray-hardening compound>

(3) Specific gravity at a temperature of 25 ° C

The specific gravity measurement by the pycnometer of the active energy ray-curable compound JIS Z 8804 before the active energy ray irradiation.

Further, in the case of using cerium oxide-based fine particles, the specific gravity of the active energy ray-curable compound containing these states is measured.

<Optical film>

(4) Full light transmittance

The total light transmittance of the optical film produced in the examples and the comparative examples was measured using a haze meter "NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS K 7136.

(5) Internal fog value, external fog value and total fog value

The optical film produced in the examples and the comparative examples and the fog of the transparent base film of the constituent members of the optical film were measured using a haze meter "NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS K 7136. value. Further, regarding the optical films of Examples 4 to 6, an adhesive layer or a glossy hard coat layer was also laminated on the surface opposite to the hard coat layer on which the transparent base film was formed, but regarding the internal haze value and the external The calculation of the haze value and the total haze value is performed using the optical film before the lamination of the layers.

The total haze value of the hard coat layer of the optical film can be calculated by subtracting the haze value of the transparent base film from the haze value of the optical film obtained by the measurement.

Then, 2 parts by mass of an isocyanate crosslinking agent (manufactured by Toyo Ink Co., Ltd., trade name "BHS-8515"), and toluene were added to 100 parts by mass of an acrylic adhesive (manufactured by Nippon Carbide Co., Ltd., trade name "PE-121"). 100 parts by mass of an adhesive solution was prepared. A polyethylene terephthalate film having a thickness of 50 μm (manufactured by Toyobo Co., Ltd., "trade name: A4300") was applied with an adhesive solution so as to have a thickness of 20 μm after drying, and dried at 100 ° C for 3 minutes to prepare a transparent adhesive sheet. .

The prepared transparent adhesive sheet was adhered to the inside of the hard coat side of the optical film as a sample for calculating the internal haze value. The respective haze values of the transparent adhesive sheet and the internal haze value calculation sample were measured, and the measurement was carried out in accordance with JIS K 7136.

Next, the internal haze value of the hard coat layer of the optical film was calculated by subtracting the haze value of the transparent adhesive sheet and the haze value of the transparent base film from the haze value of the internal haze value calculation sample.

Finally, the external haze value of the hard coat of the optical film is calculated by subtracting the internal haze value from the total haze value.

(6) Evaluation of anti-glare

The optical film was attached to a sample of an acrylic resin blackboard [manufactured by Sumitomo Chemical Co., Ltd.] via an acrylic adhesive, and visually observed on a fluorescent lamp, and the anti-glare property was evaluated by the following criteria.

A: No anti-glare.

B: It has anti-glare properties.

C: Although it has anti-glare properties, it will be whitened.

(7) 60° specular gloss rate

The gloss meter "VG2000" manufactured by Nippon Denshoku Industries Co., Ltd. was used, and the measurement was carried out in accordance with JIS K 7105.

(8) Image clarity

The image clarity measuring instrument "ICM-10P" manufactured by Suga Test Machine Co., Ltd. was used, and it was measured in accordance with JIS K 7374. The total of the five kinds of slits (slit width: 0.125 mm, 0.25 mm, 0.5 mm, 1 mm, and 2 mm) is represented by image sharpness.

(9) Anti-glare

The surface of the polarizing plate was peeled off on the surface of the liquid crystal display "AQUOS LC-20AX5" manufactured by Sharp Corporation, and a polarizing plate produced by using the optical films obtained in the examples and the comparative examples was placed, and the flicker of the brightness was visually observed. Further, the polarizing plate is bonded to the optical film by adsorbing iodine on one side of the polarizing element of the stretched polyvinyl alcohol, and the other side is attached to a film of triacetyl cellulose (hereinafter referred to as [TAC]) [Konica Minoltaopt shares Made by the company, the product name "KC8UX2M"].

◎: No flicker of brightness.

○: There is little flicker in brightness, and there is no practical problem.

△: There are some flicker of brightness, and there are practical problems.

×: There is a lot of flicker in brightness, which is unqualified.

(10) Character recognition

The surface film of the liquid crystal display "AQUOS LC-20AX5" manufactured by Sharp Corporation was evaluated for the color recognition of the liquid crystal display by the optical film obtained in the examples and the comparative examples.

◎: The degree of recognition is good.

○: The degree of recognition is slightly inferior, but there is no practical problem.

△: The degree of recognition is somewhat deteriorated, and there are practical problems.

×: The degree of recognition is poor and is unqualified.

(11) Surface resistivity

The JIS K 6911 was used to measure the parallel electrode of a resistivity meter "MCP-HT450" manufactured by Mitsubishi Chemical Corporation.

(12) Reflectivity

The reflectance at wavelengths of 500 nm, 600 nm, and 700 nm was measured using a spectrophotometer ["Shimadzu Corporation", "UV-3101PC").

(13) Evaluation of the surface state

The surface of the hard coat layer was visually observed, and the unevenness of the unevenness of the hard coat layer was evaluated in accordance with the following criteria.

○: The entire surface of the hard coat layer can be uniformly seen.

X: On the surface of the hard coat layer, a portion having high antiglare property and a low portion were mixed therein, and it was observed that the whole was uneven.

(14) Thickness of hard coating

The thickness of each of the optical film produced in the examples and the comparative examples and the transparent base film used in the production of the optical film was measured using a constant pressure thickness meter [MH-15M, manufactured by Nikon Co., Ltd.], and the difference was used as a difference. The thickness of the hard coat.

(15) Refractive index

‧Organic particles

It is calculated from the composition of the monomer of the organic fine particles from the refractive index and the mass ratio of the contained monomers.

‧Refractive index of active energy ray-hardening compound

Each of the coating agents 1 , 2 and 6 for the hard coat layer was prepared by preparing a coating agent in a state in which no organic fine particles were added, and a corresponding hard coat layer was produced in the same manner as in Example 1. The refractive index of the hard coat layer was measured by an ABC refractometer [manufactured by Atago, model name "Abe Flex 4T", Na light source, wavelength: about 590 nm], and JIS K 7142. The measured value is defined as the refractive index of the active energy ray-curable compound.

(16) Evaluation of anti-dust adhesion

The optical films obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were placed side by side in a certain room through which people passed for one month. One month later, the dust adhesion of the surface of the hard coat layer was evaluated by visual observation from the following criteria.

○: There is no adhesion to dust at all.

×: Dust adheres to one side of the hard coat layer.

Preparation Example 1 Coating Agent for Hard Coating 1

The active energy ray-curable compound is a hard coating agent having antistatic properties [manufactured by Nippon Kasei Co., Ltd., trade name "UV-ASHC", a solid concentration of 70% by mass, and a total active energy ray-curable compound of 65 % by mass. Photopolymerization initiator: 5% by mass, propylene glycol monomethyl ether: 30% by mass, solid content: specific gravity: 1.35, refractive index after curing 1.53] 100 parts by mass, and organic fine particles using acrylic fine particles [manufactured by Soken Chemical Co., Ltd., trade name "SX500HMR" The average particle diameter is 3.5 μm, the specific gravity is 1.10, the refractive index is 1.57] 3.75 parts by mass, and the dilution solvent is 90 parts by mass of propylene glycol monomethyl ether, and uniformly mixed to prepare a coating agent 1 for a hard coating layer having a solid content of 40% by mass. .

Preparation Example 2 Coating Agent for Antireflection Layer 2

The active energy ray-curable compound is a UV-curable hard coating agent (manufactured by Arakawa Chemical Co., Ltd., trade name "Beamset 575CB", solid content: 100%], 100 parts by mass, and methyl group of porous cerium oxide particles. Isobutyl ketone (MIBK) dispersion [manufactured by Catalyst Chemical Industries, Ltd., trade name "ELCOM RT-1002SIV", solid content 21% by mass, porous cerium oxide particles: specific gravity 1.8, refractive index after hardening 1.30, The average particle diameter of 60 nm] was mixed with 80 parts by mass, and the coating agent 2 for an antireflection layer was prepared by diluting with MIBK so that the solid content concentration of the entire diluted portion was 2% by mass.

Preparation Example 3 Coating Agent for Adhesive Layer 3

The coating composition 3 for an adhesive layer is prepared by mixing the adhesive composition of the following composition.

<Adhesive composition>

100 parts by mass of the acrylic copolymer / 25 parts by mass of the ultraviolet curable polyfunctional acrylate / 1 part by mass of the photopolymerization initiator / 2 parts by mass of the isocyanate crosslinking agent

‧Acrylic copolymer: butyl acrylate / methyl acrylate / acrylic acid (mass ratio 77:20:3), weight average molecular weight 800,000

‧ UV-curable polyfunctional acrylate: propylene (propylene oxyethyl) iso-cyanate, molecular weight 578 [manufactured by Toagosei Co., Ltd., trade name "Aronics M-315"]

‧Photopolymerization initiator: 1:1 mixture of diphenyl ketone and 1-hydroxycyclohexyl phenyl ketone [manufactured by Ciba Specialty Chemical Co., Ltd., trade name "Irgacure 500"]

‧Isocyanate cross-linking agent: Trimethylolpropane-modified diphenyl isocyanate [made by Japan Polyurethane Co., Ltd., trade name "Coronet L"

Preparation Example 4 Bright Coating Agent for Hard Coating 4

For the active energy ray-curable compound, an ultraviolet (UV) hardening type hard coating agent (manufactured by Arakawa Chemical Co., Ltd., trade name "Beamset 575CB"), a polyurethane acrylate 95% by mass, and a photopolymerization initiator 15 are used. 100% by mass of 100% by mass of solid content, 100 parts by mass of propylene glycol monomethyl ether, and a coating agent 4 for a bright surface hard coat layer having a solid content of about 40% by mass.

Preparation Example 5 Coating Agent for PMMA Sheet 5

A coating agent 5 for PMMA sheets was prepared by preparing a 19% by mass ethyl acetate solution of polymethyl methacrylate (PMMA) [weight average molecular weight: about 110,000, molecular weight distribution: about 2.3].

Preparation Example 6 Coating Agent for Hard Coating Layer 6

A compound obtained by bonding an organic compound having a polymerizable unsaturated group is a hard coating agent [manufactured by JSR Corporation, trade name "opstar Z7524", and has a solid concentration of 70% by mass, and contains reactive cerium oxide particles and The active energy ray-curable compound of the polyfunctional acrylate is 65 mass%, the photopolymerization initiator is 5% by mass, the methyl ethyl ketone is 30% by mass, the solid component is specific gravity 1.51, and the refractive index after curing is 1.50] 100 parts by mass; the organic fine particles are PMMA particles. [Made in Chemical Co., Ltd., trade name MX-500, average particle diameter 5 μm, specific gravity 1.19, refractive index 1.49] 7.5 parts by mass; dilution solvent is uniformly mixed with cerium oxide particles using 90 parts by mass of propylene glycol monomethyl ether A coating agent 6 for a hard coat layer having a solid content of about 40% by mass was prepared.

Preparation Example 7 Coating Agent for Hard Coating Layer 7

A coating agent for producing an anti-glare hard coat layer of an amorphous ceria having an average particle diameter of about 5 μm (product name "Seikabeam EXF L-203 (MBS1), manufactured by Daisei Seika Co., Ltd.), solid content concentration 70% by mass, 60% by weight of an active energy ray-curable compound containing a reactive monomer and a polyfunctional acrylate, 3% by mass of a photopolymerization initiator, 75% by mass of an amorphous ceria, propylene glycol monomethyl acetate 30 100% by mass of the propylene glycol monomethyl ether as a diluent solvent was uniformly mixed to prepare a coating agent 7 for a hard coat layer having a solid content of about 40% by mass.

Preparation Example 8 Coating Agent for Hard Coating Layer 8

An anti-glare hard coating agent (manufactured by Tokushiki Co., Ltd., trade name "HCA-150D", which is obtained by dispersing an amorphous ceria having an average particle diameter of about 2 μm, has a solid content concentration of 70% by mass, and contains a reactive monomer and a large amount. 60% by mass of active energy ray-curable compound of functional acrylate, 3 mass% of photopolymerization initiator, 7% by mass of amorphous ceria, 30% by mass of propylene glycol monomethyl acetate; 100 parts by mass; as a diluent solvent 90 parts by mass of propylene glycol monomethyl ether was uniformly mixed to prepare a coating agent 8 for a hard coat layer having a solid content of about 40% by mass.

Example 1

The transparent base film was coated on a surface of a polyethylene terephthalate (PET) film having a thickness of 100 μm (manufactured by Toyobo Co., Ltd., trade name "PET 100A4300", and coated with a mayer bar coater). The obtained coating agent 1 for a hard coat layer had a cured film thickness of about 8 μm. After drying in an oven at 70 ° C for 1 minute, ultraviolet rays having a light amount of 300 mJ/cm ² were irradiated with a high pressure mercury lamp to form a hard coat layer, and an optical film was produced.

The properties of the optical film are shown in Table 1.

Example 2

A transparent base film was produced in the same manner as in Example 1 except that a triacetyl cellulose (TAC) film (manufactured by Fuji Film Co., Ltd., trade name "TAC-TD80UL (H)") having a thickness of 80 μm was used. Optical film.

The properties of the optical film are shown in Table 1.

Example 3

On the hard coat layer formed in Example 2, the film was coated with a Meyer bar coater so that the anti-reflective coating agent 2 obtained in Preparation Example 2 had a cured film thickness of 0.1 μm. After drying in an oven at 70 ° C for 1 minute, ultraviolet rays having a light amount of 300 mJ/cm ^{2 were} irradiated with a high-pressure mercury lamp to prepare an optical film having a low refractive index layer.

The properties of the optical film are shown in Table 1.

Example 4

In the optical film obtained in Example 1, the adhesive layer obtained in Preparation Example 3 was coated with a Meyer bar coater on the surface of the PET film which is the transparent base film on the side where the hard coat layer was not formed. The agent 3 was dried and hardened to have a film thickness of 20 μm. After drying in an oven at 70 ° C for 1 minute, ultraviolet rays having a light amount of 300 mJ/cm ^{2 were} irradiated with a high-pressure mercury lamp to prepare an optical film having an adhesive layer.

The properties of the optical film are shown in Table 1.

Example 5

In the optical film obtained in Example 1, the surface of the PET film which is the transparent base film was not coated with the hard coat layer, and the film was coated with a Meyer bar coater to prepare the bright surface hard coat layer obtained in Preparation Example 4. The coating agent 4 was set so that the thickness of the cured film became 5 μm. The surface opposite to the hard coat layer after drying in an oven of 70 deg.] C for 1 minute, high pressure mercury lamp, irradiation light amount 300mJ / cm ² of ultraviolet rays, having antiglare properties to produce an optical film having a hard coat layer glossy .

The properties of the optical film are shown in Table 1.

Example 6

The engineering film was coated on a PET film ("Diafoil T-100" (registered trademark), manufactured by Mitsubishi Plastics Co., Ltd.), and coated with a coating machine to prepare a PMMA sheet coating agent 5 obtained in Example 5 to have a thickness after drying. After it became 30 μm, it was dried at 100 ° C for 1 minute to form a PMMA layer which became a transparent base film.

Next, on the PMMA layer, the coating agent 1 for a hard coat layer obtained in Example 1 was prepared by coating with a Meyer bar coater so as to have a thickness of 8 μm after drying, and then irradiated with ultraviolet rays at a light amount of 300 mJ/cm ^{2 to} form a hard coat. Floor. Next, a protective film having a thickness of 20 μm (manufactured by Lintec Co., Ltd., trade name "SPF/AlA", PET protective film] was adhered to the surface of the hard coat layer.

Then, the adhesive layer coating agent 3 obtained by preparing the film preparation example 3 by a Meyer bar coater coating method on a release-treated surface of a PET-made release film having a thickness of 38 μm (manufactured by Lintec Co., Ltd., trade name "SP-PET381031") The thickness after drying was 10 μm, and it was dried to form an adhesive layer.

Finally, the "Diafoil T-100" (registered trademark) of the step film was peeled off, and bonded to the adhesive layer of the PMMA sheet of the transparent base film to be bonded to the adhesive layer to form an adhesive layer/ The PMMA sheet/hard coat layer is formed into a three-layer laminated optical film.

The properties of the optical film are shown in Table 1.

Comparative example 1

The coating agent 6 for a hard coat layer obtained in Preparation Example 6 was coated with a Meyer bar coater, and an optical film was produced in the same manner as in Example 2 except that the cured film thickness was 3.5 μm.

The properties of the optical film are shown in Table 1.

Comparative example 2

The coating agent 6 for a hard coat layer obtained in Preparation Example 6 was coated with a Meyer bar coater, and an optical film was produced in the same manner as in Example 2 except that the cured film thickness was 4.8 μm.

The properties of the optical film are shown in Table 1.

Comparative example 3

The coating agent 7 for a hard coat layer obtained in Preparation Example 7 was coated with a Meyer bar coater, and the optical film was produced in the same manner as in Example 2 except that the cured film was 5 μm thick.

The properties of the optical film are shown in Table 1.

Comparative example 4

The coating agent 8 for a hard coat layer obtained in Preparation Example 8 was coated with a Meyer bar coater, and the optical film was produced in the same manner as in Example 2 except that the cured film was made to have a thickness of 5 μm.

The properties of the optical film are shown in Table 1.

Table 1 below shows the items shown below.

The optical films of the present invention (Examples 1 to 6) each have a range of external haze of 7% or less (3.95 to 5.24%) and an internal haze value of 1 to 12% (10.89 to 11.39%). And the 60° specular gloss rate is in the range of 100 to 150 (120.8 to 129.4). The image clarity is high, exceeding 300. The result is not only moderately glare-proof, but also excellent in visibility and anti-glare. The state of the hard coat surface is also excellent.

In Example 3, an optical film having a low refractive index layer provided on the hard coat layer was excellent in antireflection property as compared with the optical film of Example 1.

On the one hand, in Comparative Example 1, the average particle diameter of the organic fine particles was larger than the thickness of the hard coat layer, and the image sharpness was less than 15.4, and the visibility was extremely poor. In Comparative Example 2, the average particle diameter of the organic fine particles was substantially equal to the thickness of the hard coat layer, and the degree of discrimination was not deteriorated, and unevenness occurred on the surface of the hard coat layer. In Comparative Example 3, a type (widely used type) of a cerium oxide gel filler was used, and the image clarity was low and the visibility was poor. In Comparative Example 4, the type of the cerium oxide gel filling agent (high-definition type) was used, and the image sharpness was higher than that of Comparative Examples 1 to 3, but less than 300, and the degree of recognition was not good.

[Industrial availability]

The optical film of the present invention has a hard coat layer, is excellent in abrasion resistance, and has good image clarity and moderate anti-glare property, and is particularly suitable as a polarizing plate or a touch panel.

Claims (6)

An optical film characterized in that a hard coat layer is formed on at least one side of a transparent base film by an active energy ray-curable compound and an organic fine particle having an average particle diameter of 1 to 5 μm to form a hard coat layer. The coating has an external haze value of 7% or less, an internal haze value of 1 to 12%, and a 60° specular gloss ratio of 100 to 150. The optical film of claim 1, wherein the hard coat layer has a thickness of 7 to 20 μm. An optical film according to claim 1 or 2, wherein the average particle diameter of the organic fine particles is smaller than the thickness of the hard coat layer. An optical film according to claim 1 or 2, which is obtained by further laminating a low refractive index layer on a hard coat layer. An optical film according to claim 1 or 2, which is formed by laminating an adhesive layer on a surface of the transparent base film on the side where the hard coat layer is not formed. An optical film according to claim 1 or 2, which is formed by laminating a hard coat layer on a surface of a transparent base film on a side where a hard coat layer is not formed.