TWI785703B - Optical film, polarizing plate and liquid crystal display device - Google Patents

Abstract

The optical film of the present invention contains cycloolefin resin. The area from one side of the optical film to the depth of 30% of the thickness is the surface area (Sa), the area from the other side to the depth of 30% of the thickness is the surface area (Sb), and the surface area (Sa) and the surface area (Sb) ) as the inner region (C), at least the ratio As of the absorption coefficient As of the light with a wavelength of 9.6 μm in the surface region (Sa) to the absorption coefficient Ac of light with a wavelength of 9.6 μm in the inner region (C) /Ac is 1.1 to 20, and the absorption coefficient of light with a wavelength of 9.6 μm of the optical film is 1.5×10 ^-5 /μm or more.

Description

Optical film, polarizing plate and liquid crystal display device

The invention relates to an optical film, a polarizing plate and a liquid crystal display device.

A display device such as a liquid crystal display device includes a polarizing plate. The polarizer includes a polarizer and a protective film for the polarizer. Cycloolefin resin films may be used for polarizer protective films due to their excellent transparency and high moisture resistance.

Such a polarizing plate is usually used after bonding a polarizer and a polarizer protective film with an adhesive or the like, and then cutting it into a specific size. The cutting of the polarizing plate is, for example, a mechanical cutting method using a knife or a laser cutting method using laser light. The mechanical cutting method tends to have fine scratches and the residual stress tends to become uneven. Therefore, in recent years, the laser cutting method is often used.

Cycloolefin resin films generally have a low absorption rate of laser light, so it is difficult to cut them off with laser light.

On the other hand, in order to enable cutting by a laser cutting method, a polarizing plate using a polarizer protective film including a base material containing a laser absorber is known (see, for example, Patent Document 1). [Prior Art Literature] [Patent Document]

[Patent Document 1] International Publication No. 2018/139638

[Problem to be Solved by the Invention]

However, the polarizer protective film comprising cycloolefin resin in Patent Document 1 is insufficient in cuttability by laser light. Therefore, when it is desired to cut the polarizer protective film with laser light, it is necessary to irradiate with high-intensity laser light. Therefore, polarizers with a high absorption rate of laser light are easy to burn, generate soot, and pollute the polarizer. In order to improve the cut-off property by laser light, when a large amount of laser absorber (light-absorbing material) is added, the transparency of the optical film is likely to be damaged.

In contrast, the inventors of the present invention have found that the laser light cut-off rate can be improved without compromising the transparency of the optical film by locally increasing the absorption rate of the laser light in the surface layer region of the polarizer protective film (optical film). sex. On the other hand, when the absorptivity of laser light in the surface layer region is excessively increased, there is a new problem that light leakage is likely to occur in the display device.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an optical film, a polarizing plate, and a liquid crystal display device that can improve the cutting performance by laser light without causing light leakage in the display device. [Means to solve the problem]

The present invention relates to the following optical film, polarizing plate and liquid crystal display device.

The optical film of the present invention is an optical film comprising cycloolefin resin, the area from one surface of the optical film to the depth of 30% of the thickness of the optical film is defined as the surface region Sa, and the area from the other surface of the optical film to the optical film is When the area at the depth of 30% of the thickness of the film is defined as the surface area Sb, and the area between the aforementioned surface area Sa and the aforementioned surface area Sb is used as the inner layer area C, at least the wavelength of the aforementioned surface area Sa measured by the ATR method is 9.6 μm The ratio As/Ac of the absorption coefficient As of light to the absorption coefficient Ac of light with a wavelength of 9.6 μm measured by the ATR method in the inner layer region C is 1.1 to 20, and the absorption coefficient of light with a wavelength of 9.6 μm of the aforementioned optical film is 1.5×10 ^-5 /μm or more.

The polarizing plate of the present invention has a polarizer, and the optical film of the present invention disposed on at least one side of the polarizer.

The liquid crystal display device of the present invention has a liquid crystal cell, and a first polarizer and a second polarizer sandwiching the liquid crystal cell, and at least one of the first polarizer and the second polarizer is the polarizer of the present invention. [Invention effect]

According to the present invention, it is possible to provide an optical film, a polarizing plate, and a liquid crystal display device capable of improving cutting performance by laser light without causing light leakage in a display device.

[Mode of Implementing the Invention]

As mentioned above, by locally increasing the absorption rate of laser light in the surface region of the optical film, the transparency of the optical film can be improved, and the cutting performance by laser light can be improved. Therefore, it is easy to cause light leakage when used as a display device.

Although the reason for this is unknown, it is presumed as follows. That is, when the absorption rate of laser light in the surface region of the optical film is excessively increased locally, the heat generated by the absorption of laser light in the surface region is much greater than the heat generated in the inner layer region, which is likely to cause stress differences. .

On the other hand, in the present invention, the absorptivity of laser light in the surface region of the optical film is moderately increased. That is, the absorption coefficient of light with a wavelength of 9.6 μm in the entire optical film is set to a certain value or more, and the absorption coefficient As of light with a wavelength of 9.6 μm in the surface region Sa and the absorption coefficient Ac of light with a wavelength of 9.6 μm in the inner region C The ratio As/Ac is set at 1.1-20, preferably 3-15. Thereby, the cutting property by laser light is improved, and the stress difference caused by the heat generated by the absorption of laser light can be reduced between the surface layer region Sa and the inner layer region C, so that light leakage in the display device can be suppressed. Hereinafter, the configuration of the present invention will be described.

1. Optical film The optical film of the present invention contains a cycloolefin resin. Furthermore, the absorptivity of laser light in at least one surface layer region of the optical film becomes locally high (higher than that in the inner layer region).

FIG. 1 is a schematic cross-sectional view showing the surface regions Sa and Sb and the inner region C of an optical film 10 .

The regions from one side 10a and the other side 10b of the optical film 10 to the depth of 30% of the thickness of the optical film 10 are the surface regions Sa and Sb respectively, and when the region between them is used as the inner layer region C, at least one surface layer The absorptivity of the laser light in the region Sa is higher than the absorptivity of the laser light in the inner layer region C. Specifically, the ratio As/Ac of the absorption coefficient As of light with a wavelength of 9.6 μm in at least one surface region Sa and the absorption coefficient Ac of light with a wavelength of 9.6 μm in the inner region C is preferably 1.1-20.

When As/Ac is 1.1 or more, the absorptivity of laser light in the surface layer region Sa can be relatively increased, so it is easy to improve the cutting property by laser light. When As/Ac is less than 20, the calorific value caused by the laser light absorption in the surface region Sa will not be much greater than the calorific value caused by the laser light absorption in the inner layer region C, so the heat generated by the laser light absorption can be reduced. Stress difference due to heat generation. Therefore, light leakage of the display device can be suppressed. From the same viewpoint, As/Ac is more preferably 3-15.

As/Ac can be measured using the following method. 1) First, using a microscope FTIR ("UMA600" and "FTS3000" manufactured by Agilent), by the ATR method, the incident light path: 100μm, the galvanic: Ge (incident angle 45°), the detector: MCT-A, the resolution : 4.0 cm ^-1 , accumulation: 64 times, the infrared absorption spectrum was measured. From the obtained infrared absorption spectrum, the absorbance of a portion corresponding to a wavelength of 9.6 μm (frequency 1041 cm ⁻¹ ) was read, and the absorbance A of the entire optical film 10 was measured. 2) Next, cut 30% of the thickness from one side 10a of the optical film 10 . Then, the absorbance A1 of the cut surface was measured in the same manner as in the above 1). 3) Also, cut 30% of the thickness from the other surface 10b of the optical film 10 . Then, the absorbance A2 of the cut surface was measured in the same manner as in 1) above. 4) Put the absorbances A, A1 and A2 obtained in the above 1) to 3) into the following formula to calculate the light absorption coefficient As of the surface region Sa and the light absorption coefficient Ac of the inner layer region C, respectively. The light absorption coefficient As=(A-A1)×loge10÷(0.3T) of the surface area Sa, the light absorption coefficient Ac=A2×loge10÷(0.4T) of the inner area C (T: the thickness of the optical film 10 A: the optical film 10 Absorbance A1: Cut 30% of the thickness T of the optical film 10 from one side 10a of the optical film 10, and measure the absorbance A2: Cut 30% of the thickness T of the optical film 10 from the other side 10b of the optical film 10 , the absorbance at which the measurement was performed)

The absorption coefficient of laser light in the other surface region Sb of the optical film 10 can be higher than that of the inner layer region C or can be equal. That is, the ratio As/Ac of the absorption coefficient As of the light with a wavelength of 9.6 μm in the surface region Sb of the optical film 10 to the absorption coefficient Ac of light with a wavelength of 9.6 μm in the inner region C can be 1 to 20, or 1.1 ~20.

In addition, the absorption coefficient of light with a wavelength of 9.6 μm of the optical film 10 is preferably 1.5×10 ^-5 /μm or more, more preferably 2.0×10 ^-5 to 50×10 ^-5 /μm.

As/Ac or the absorption coefficient A of the optical film 10 can be adjusted by the distribution, type, content, etc. of the material (light-absorbing material) that absorbs laser light. That is, when As/Ac is desired to be raised above a certain value, the optical film 10, preferably, the surface region Sa and the inner layer region C each contain a light-absorbing material; the content Ms of the light-absorbing material in the surface region Sa is more than that of the inner layer The content Mc of the light-absorbing material in the region C (specifically, Ms/Mc is 2.5-20, preferably 3.5-15). Hereinafter, the light-absorbing material will be described in detail.

Such an optical film 10 may be a laminated film having a base layer and a surface layer, or may be a single-layer film.

The following embodiments will be described as examples in which the optical film is a laminated film having a base layer and a surface layer.

FIG. 2A is a cross-sectional view showing the structure of the optical film 10 of this embodiment.

As shown in FIG. 2A , the optical film 10 of this embodiment has a base layer 11 and two surface layers 12 and 13 sandwiching the base layer 11 .

The substrate layer 11 includes cycloolefin resin and light absorbing material.

1-1. Substrate layer 1-1-1. Cycloolefin resin Cycloolefin resins are polymers comprising structural units derived from norbornene-based monomers.

The norbornene-based monomer system is represented by the following formula (1).

R ¹ to R ⁴ in formula (1) respectively represent a hydrogen atom, a halogen atom, a hydrocarbon group, or a polar group.

Examples of halogen atoms include fluorine atoms, chlorine atoms and the like.

The hydrocarbon group is a hydrocarbon group with 1-10 carbon atoms, preferably 1-4, more preferably 1 or 2 carbon atoms. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, and butyl. The hydrocarbon group may further have a divalent linking group including a linking group of an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom (for example, a carbonyl group, an imino group, an ether bond, a silicon ether bond, a thioether bond, etc.).

Examples of polar groups include linking groups (-(CH ₂ ) _n - , n is an integer of 1 or more), the group that bonds these groups. Among them, an alkoxycarbonyl group and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group is more preferable.

Among them, at least one of R ¹ to R ⁴ is preferably a polar group. Cycloolefin resins containing structural units derived from norbornene-based monomers having polar groups are easily dissolved in solvents when film-forming by solution casting, for example, and tend to increase the glass transition temperature of the resulting film. On the other hand, in the melt film-forming method, a cycloolefin resin not containing a structural unit derived from a norbornene-based monomer having a polar group may be used.

Also, among R ¹ to R ⁴ , both of R ¹ and R ² (or both of R ³ and R ⁴ ) may be hydrogen atoms.

p in formula (1) represents an integer of 0-2. From the viewpoint of improving the heat resistance of the optical film, p is preferably 1-2.

Specific examples of the norbornene-based monomer represented by formula (1) are shown below. Among them, examples of the norbornene-based monomer having a polar group include the following.

Examples of the norbornene-based monomer having no polar group include the following.

The content of structural units derived from norcamphene-based monomers may be 50-100 mol% relative to the total structural units constituting the cycloolefin resin.

The cycloolefin resin may further contain structural units derived from other monomers that are copolymerizable with structural units derived from norbornene-based monomers. Examples of other monomers that can be copolymerized include norbornene-based monomers that do not have a polar group (in the case of the above-mentioned norbornene-based monomer having a polar group), or do not have cyclobutene, cyclopentene, cyclobutene, or cyclobutene. Cycloolefin-based monomers such as heptene, cyclooctene, and dicyclopentadiene with a norbornene skeleton.

A commercial item can also be used for cycloolefin resin. Examples of commercially available products include ARTON (ARTON: registered trademark) G, ARTON F, ARTON R, and ARTON RX manufactured by JSR Corporation.

The weight average molecular weight Mw of the cycloolefin resin is not particularly limited, but is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and more preferably 40,000 to 200,000. When the weight-average molecular weight Mw of the cycloolefin resin is within the above-mentioned range, the mechanical properties of the optical film can be improved without impairing moldability.

The weight average molecular weight Mw of cycloolefin resin can be measured by gel permeation chromatography (GPC). Specifically, the measurement device used gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation), and the column system used TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation in series. Then, 20±0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran, and filtered with a 0.45 mm filter. 100 ml of this solution was poured into the above-mentioned column (temperature 40° C.), measured with a detector RI at a temperature of 40° C., and the weight average molecular weight was calculated in terms of styrene.

The glass transition temperature Tg of cycloolefin resin is usually above 110°C, preferably 110~350°C, more preferably 120~250°C. When the Tg of cycloolefin resin is 110°C or higher, it is not easy to deform even under high temperature conditions. When the Tg is 350°C or lower, the molding processability is less likely to be damaged, and the heat degradation of the cycloolefin resin during molding processing can be suppressed.

The glass transition temperature can be measured using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry) in accordance with the method of JIS K 7121-2012.

The content of the cycloolefin resin is not particularly limited, but it is preferably at least 50% by mass, more preferably 70-99% by mass, relative to the optical film.

1-1-2. Light-absorbing material The light-absorbing material may be a light-absorbing material having an absorption coefficient of 4.0×10 ^-3 /μm or more for light having a wavelength of 9.0 to 11.0 μm. The light-absorbing material is generally a compound having a carbonyl group, preferably an ester compound, or (meth)acrylic polymer particles.

＜Ester compound＞ The ester compound may be any of a sugar ester compound, a polycondensation ester compound, and a polyol ester compound.

(Sugar ester compound) The sugar ester compound is a compound obtained by esterifying all or part of OH groups of monosaccharides, disaccharides, or trisaccharides. Such a sugar ester compound is preferably a compound represented by the following formula (FA).

R ₁ to R ₈ in formula (FA) represent substituted or unsubstituted alkylcarbonyl, or substituted or unsubstituted arylcarbonyl. R ₁ to R ₈ may be the same or different from each other.

The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of substituted or unsubstituted alkylcarbonyl include methylcarbonyl (acetyl), ethylcarbonyl and the like. Examples of the substituent that the alkyl group has include aryl groups such as phenyl groups.

The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of arylcarbonyl include phenylcarbonyl. Examples of the substituent that the aryl group has include alkyl groups such as methyl groups.

Examples of R ₁ to R ₈ in formula (FA) include the following.

The average degree of substitution of the sugar ester compound is preferably 3-6. The average degree of substitution of sugar ester compounds represents the average ratio of esterification among the total number of OH groups of sugars used as raw materials.

(polyol ester compound) The polyol ester is an esterification product of an aliphatic polyol with a valence of 2 or more (preferably an aliphatic polyol with a valence of 2-20) and a monocarboxylic acid.

Examples of polyols include Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, Tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol , 1,6-hexanediol, hexanetriol, galactitol (Galactitol), pyrogallol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, Trimethylolpropane, trimethylolethane, xylitol, etc., preferably triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, xylitol .

The monocarboxylic acid is not particularly limited, and may be aliphatic monocarboxylic acids such as acetic acid and propionic acid, alicyclic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid, benzoic acid, toluic acid, etc. Any of aromatic monocarboxylic acids.

The carboxylic acid used for the polyol ester compound may be one type or a mixture of two or more types. In addition, all the OH groups in the polyol may be esterified, or part of them may remain as OH groups.

Although the molecular weights of the sugar ester compound and the polyol ester compound vary depending on the production method of the optical film, they are preferably moderately low from the viewpoint of easily obtaining good compatibility with the cycloolefin resin. Specifically, the molecular weight of the sugar ester compound or the ester compound is, for example, 300-1500, preferably 600-1200.

(Polycondensed ester compound) The polycondensation ester compound is a polycondensate (polymer) including a structural unit obtained by reacting a dicarboxylic acid and a diol.

The dicarboxylic acid may be any one of aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid, preferably aromatic dicarboxylic acid. One type of dicarboxylic acid may be used, or a mixture of two or more types may be used. Preferably, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid are mixed.

The diol may be any one of aromatic diol, aliphatic diol, and alicyclic diol, preferably aliphatic diol, more preferably a diol with 1 to 4 carbon atoms. One type of diol may be used, or a mixture of two or more types may be used.

That is, the polycondensation ester compound preferably contains a structural unit obtained by reacting a dicarboxylic acid containing an aromatic dicarboxylic acid with a diol having 1 to 8 carbon atoms, and more preferably contains a compound containing an aromatic dicarboxylic acid and a diol having a carbon number of 1 to 8. The structural unit obtained by reacting dicarboxylic acid of aliphatic dicarboxylic acid with diol with 1 to 8 carbon atoms. Both ends of the molecule of the polycondensed ester may be end capped or uncapped.

Among these ester compounds, sugar ester compounds are particularly preferred from the viewpoint of moderately low molecular weight and excellent compatibility with cycloolefin resins.

＜(Meth)acrylic polymer particles＞ The (meth)acrylic polymer particle is a particle containing a polymer of a structural unit derived from (meth)acrylate, preferably a particle containing a polymer of a structural unit derived from methyl methacrylate.

A polymer comprising structural units derived from methyl methacrylate may further comprise structural units of other comonomers. Examples of other comonomers include alkyl (meth)acrylates with 1 to 18 carbon atoms other than methyl methacrylate; α, β-unsaturated acids such as (meth)acrylic acid; maleic acid , fumaric acid, itaconic acid and other unsaturated dicarboxylic acids; styrene, α-methylstyrene and other styrenes; (poly)ethylene glycol di(meth)acrylate, butylene glycol di( Meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, etc., having two or more (methyl) ) polyfunctional (meth)acrylates of acryl; allyl (meth)acrylates of allyl (meth)acrylate, allyl alkyl (meth)acrylate, etc. and other multifunctional monomers, etc.

Among them, the above-mentioned polymer is preferably a cross-linked polymer, that is, a copolymer comprising structural units derived from methyl methacrylate and structural units derived from multifunctional monomers; more preferably comprising The structural unit of styrene is a copolymer of structural units from styrene and structural units from multifunctional monomers.

From the viewpoint of increasing the absorptivity of laser light of the base material layer 11, the content of the structural unit derived from (meth)acrylates containing a carbonyl group is preferably a certain amount or more. From this point of view, the total of the structural units derived from methyl methacrylate is preferably 30 mol% or more, more preferably 50 to 80 mol%, based on the total structural units constituting the polymer.

The content of structural units derived from polyfunctional monomers is preferably 3-50 mol%, more preferably 10-35 mol%, relative to the total structural units constituting the polymer.

The (meth)acrylic polymer particles are preferably polymers having a refractive index difference with the cycloolefin resin of 0.01 or less. Such (meth)acrylic polymer particles are less likely to lower the transparency of the resulting optical film.

The refractive index of the cycloolefin resin and the (meth)acrylic polymer particle may be the refractive index of light with a wavelength of 550 nm. For the refractive index of light with a wavelength of 550nm, for example, a sample film containing each component alone is made, and the refractive index of the sample film with a wavelength of 550nm can be obtained by measuring it with a spectroscopic ellipsometer UVSEL manufactured by Horiba.

The Tg of the (meth)acrylic polymer particles is preferably 80°C or higher. Tg of (meth)acrylic polymer particles can be measured in accordance with JIS K 7121-2012 or ASTM D 3418-82 in the same manner as above.

The average particle diameter of the (meth)acrylic polymer particles is not particularly limited, for example, it is preferably 50-500 nm. When the average particle diameter is within the above-mentioned range, the absorption rate of laser light can be increased, and moderately sized unevenness can be formed on the surface of the film, so slipperiness can be imparted. The average particle diameter of the (meth)acrylic polymer particles is more preferably 0.07 to 0.28 μm from the above viewpoint.

The average particle diameter of (meth)acrylic polymer particles can be measured according to the following procedure.

The average particle diameter of (meth)acrylic polymer particles in the optical film can be measured by the following method. First, the optical film is cut, and the obtained cut surface is observed with TEM. Then, the particle size was measured for 100 particles of arbitrary particles. The particle size is measured by the diameter of 100 particles equivalent to a circle obtained by TEM photography in the same manner as above. Then, the average value of the obtained particle diameters was taken as "average particle diameter". In addition, in the TEM image, a portion whose lightness is equal to or greater than the average lightness of the visual field×150% was judged to be a particle.

The content of the light-absorbing material in the substrate layer 11 can be set so that Ms/Mc, especially As/Ac of the optical film 10 satisfies the above-mentioned range, and the light absorption coefficient A of the optical film 10 as a whole satisfies the above-mentioned range.

That is, the content Mc' of the light-absorbing material in the substrate layer 11 is preferably less than the content Ms' of the light-absorbing material in the surface layer 12 (or 13). Specifically, the content Mc' of the light-absorbing material in the base layer 11 is preferably 0.1 to 4.5% by mass, more preferably 0.3 to 3.5% by mass relative to the base layer 11. When the content Mc' of the light-absorbing material in the substrate layer 11 is within the above-mentioned range, the light absorption coefficient A of the entire optical film 10 is adjusted to the above-mentioned range, and Ms/Mc (or Ms'/Mc'), especially As/Ac Easy to adjust to the above range. Therefore, by improving the cut-off property of laser light by the optical film 10, the difference in the calorific value of laser light between the base layer 11 and the surface layer 12 (or 13) can be reduced, so it is easy to suppress light leakage in the display device.

1-1-3. Other ingredients The base material layer 11 may further contain other components such as inorganic fine particles as necessary.

Inorganic fine particles have the function of improving the slipperiness of optical films. Examples of inorganic materials constituting the inorganic fine particles include oxides such as silicon dioxide (SiO ₂ ), titanium dioxide, aluminum oxide, and zirconium oxide. Among them, silicon dioxide is preferable from the viewpoint of reducing the increase in haze of the film.

Examples of commercially available silica particles include AEROSIL R812, R972 (manufactured by Aerosil Japan), NanoTek SiO2 (manufactured by C.I. Kasei), and the like.

The average primary particle size of the inorganic fine particles is preferably 5-50 nm. When the average primary particle diameter of the inorganic fine particles is 5 nm or more, the surface of the film can be roughened, so it is easy to impart slipperiness, and when it is 50 nm or less, it is easy to suppress the increase of haze. The average primary particle size of the inorganic fine particles is preferably 5-30 nm. The average primary particle diameter of the inorganic fine particles in the optical film 10 can be measured by the same method as above.

The content of the inorganic fine particles is not particularly limited, but it is 0-5% by mass, preferably 0-2% by mass relative to the optical film.

1-1-4. Physical properties The thickness of the substrate layer 11 is set so that As/Ac and the light absorption coefficient of the optical film as a whole are within the above-mentioned range, and there is no special limitation, for example, it is preferably 30-60 μm, more preferably 35-55 μm.

1-2. Surface layers 12 and 13 The surface layer 12 is included in the surface area Sa from one side 10a of the optical film 10 to 30% of the thickness; the surface layer 13 is included in the surface area Sb from the other side 10b of the optical film 10 to 30% of the thickness (see FIG. and 2A). The surface layers 12 and 13 are each composed of a thermoplastic resin composition including a thermoplastic resin and a light-absorbing material (aspect 1), and may also include a hardening compound having light-absorbing properties (hardening compound as a light-absorbing material) and a hardening compound. It is composed of the cured product of the curable composition of the agent (state 2).

＜About Form 1＞ The surface layers 12 and 13 are each made of a resin composition including a thermoplastic resin and a light-absorbing material. In addition, a thermoplastic resin may also serve as a light-absorbing material.

(thermoplastic resin) The thermoplastic resin contained in the thermoplastic resin composition is not particularly limited as long as it has light-transmitting properties, and may be cycloolefin resin, (meth)acrylic resin, or the like.

The cycloolefin resin contained in the surface layer 12 (or 13 ) may be the same as the cycloolefin resin contained in the base material layer 11 .

The (meth)acrylic resin contained in the surface layer 12 (or 13) functions not only as a thermoplastic resin but also as a light absorbing material.

The (meth)acrylic resin is preferably a polymer comprising structural units derived from methyl methacrylate. The polymer may further comprise structural units from monomers copolymerizable with methyl methacrylate. Examples of other monomers that can be copolymerized with methyl methacrylate include alkyl (meth)acrylates with 1 to 18 carbon atoms other than methyl methacrylate such as 2-ethylhexyl methacrylate ; α, β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrenes such as styrene and α-methylstyrene; Maleic anhydride; maleimides such as maleimide and N-phenylmaleimide; glutaric anhydride, etc.

The content ratio of the structural unit derived from methyl methacrylate is preferably at least 50% by mass, more preferably at least 70% by mass, relative to all structural units constituting the copolymer. Also, the weight average molecular weight of the (meth)acrylic resin is more preferably 40,000 to 500,000.

Among them, the interlayer adhesion with the substrate layer 11 is good, and the thermoplastic resin contained in the surface layer 12 (or 13) is preferably a cycloolefin resin from the viewpoint of not being easily damaged and transparent.

The composition of the cycloolefin resin contained in the surface layer 12 (or 13 ) may be the same as or different from the composition of the cycloolefin resin contained in the base layer 11 . From the standpoint of improving interlayer adhesion or production efficiency, it is preferable that the composition of the cycloolefin resin contained in the surface layer 12 (or 13 ) is the same as the composition of the cycloolefin resin contained in the base layer 11 .

(light absorbing material) As the light-absorbing material contained in the surface layer 12 (or 13), the same light-absorbing material as that contained in the substrate layer 11 can be used.

The type of light-absorbing material contained in the surface layer 12 (or 13 ) may be the same as or different from the type of light-absorbing material contained in the substrate layer 11 . From the viewpoint of improving manufacturing efficiency, it is preferable that the type of light-absorbing material contained in the surface layer 12 (or 13 ) is the same as the type of light-absorbing material contained in the base layer 11 .

The content of the light-absorbing material in the surface layer 12 (or 13) is preferably set so that Ms/Mc, especially As/Ac of the optical film 10 satisfies the above range, and the light absorption coefficient A of the entire optical film 10 satisfies the above range.

That is, the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is preferably greater than the content Mc' of the light-absorbing material in the base layer 11. Specifically, although the content Ms' of the light-absorbing material in the surface layer 12 (or 13) varies, Ms'/Mc' is preferably 2.5-50, more preferably 7-15. For example, the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is preferably 1-30% by mass, more preferably 3-10% by mass relative to the surface layer 12 (or 13). When the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is in the above range, the light absorption coefficient A of the optical film 10 as a whole is adjusted to the above range, and Ms/Mc (Ms'/Mc'), especially As/Ac It is easy to adjust to the above-mentioned range. Thereby, the cutting property of the optical film 10 by laser light is improved, and the difference in the calorific value of laser light can be reduced between the base layer 11 and the surface layer 12 (or 13), so it is easy to suppress light leakage in the display device . That is, from the viewpoint of suppressing light leakage in the display device, Ms'/Mc' is preferably not too large, and Ms' is not too large.

(other ingredients) The surface layer 12 (or 13 ) is the same as the base material layer 11, and may further contain other components such as inorganic fine particles.

＜About Form 2＞ The surface layer 12 (or 13) may be composed of a hardened composition of a light-absorbing hardening compound and a hardening agent.

The light-absorbing curable compound contained in the curable composition is preferably a urethane compound having a group reactive with a curing agent.

(urethane compound) Urethane compounds having functional groups reactive with hardeners are obtained by reacting polyols with polyisocyanates. The urethane compound may be a monomer or a prepolymer. Such a urethane compound has, for example, a functional group (hydroxyl group, acrylate group, carboxyl group, acrylamide group, etc.) that remains unreacted as a group that reacts with a curing agent after polyol and polyisocyanate are reacted.

Examples of polyols include polyol compounds (for example, ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, glycerol, trimethylolpropane, etc.) dicarboxylic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, etc. Polyester polyols obtained by the reaction of polycarboxylic acids containing tricarboxylic acids or their anhydrides, etc.); polyether polyols (such as poly(oxypropylene ether) polyols, poly(oxyethylene-propylene ether) polyols); polyols Carbonate polyols, etc. Among them, polycarbonate polyurethane is preferred.

The curing agent is a compound having two or more functional groups that react with (unreacted) functional groups contained in the urethane compound in the molecule. For example, examples of hardeners of urethane compounds containing (as a group reactive with hardeners) hydroxyl groups include epoxy compounds, isocyanate compounds, tertiary amine compounds, and carbodiimide compounds; Examples of hardening agents of acrylamide-based urethane compounds include active hydrogen compounds such as dicarboxylic acids.

In addition, the urethane compound (urethane acrylate) having an acrylate group (as a group that reacts with a hardener) is one in which a polyol having an acrylate group is reacted with a polyisocyanate, or a polyol After reacting with polyisocyanate, the unreacted isocyanate group of the resulting urethane compound is esterified with (meth)acrylic acid.

Urethane acrylate can also be used together with another (meth)acrylate compound. Examples of other (meth)acrylate compounds include isocyanurate acrylates such as isocyanurate diacrylates and isocyanurate triacrylates.

The hardener for urethane acrylate may be a free radical hardener. Examples of radical curing agents include intramolecular cleavage initiators such as α-hydroxyalkylphenones.

(other ingredients) The curable composition may further contain other components such as a curing accelerator, a curing aid, and fine particles, if necessary.

For example, when an epoxy compound is used as a curing agent, a tertiary amine compound or a boron trifluoride zirconium compound can be used as a curing accelerator. Examples of fine particles include inorganic fine particles such as silica particles.

＜Common Items of Forms 1 and 2＞ The surface layer 12 (or 13) can be composed of a thermoplastic resin composition including a thermoplastic resin and a light-absorbing material as described above (aspect 1), and can be hardened by a hardening composition of a hardening compound and a hardener having light-absorbing properties. constituted by things (state 2). Among them, in terms of good interlayer adhesion with the substrate layer 11 and not easy to peel off, the surface layer 12 (or 13) is preferably Aspect 1, that is, a thermoplastic resin composition comprising a thermoplastic resin and a light-absorbing material What constitutes; (the same as the base material layer 11 ), is more preferably composed of a thermoplastic resin composition including a cycloolefin resin and a light-absorbing material.

1-1-4. Physical properties The thickness of the surface layer 12 (or 13) is not particularly limited as long as the light absorption coefficient A of As/Ac and the optical film as a whole is within the above-mentioned range. Preferably it is 0.3-30%, more preferably 2-10%. Specifically, the total thickness of the substrate layer 11 and the surface layer 12 (or the surface layer 13 ) is preferably 20-100 μm, more preferably 35-60 μm. Moreover, the thickness of the base material layer 11 is preferably 15-60 μm, more preferably 30-50 μm.

1-3. Physical properties of optical films (total light transmittance) The total light transmittance of the optical film is not particularly limited as long as it has sufficient light transmittance. It is preferably at least 80%, more preferably at least 85%, and even more preferably at least 88%. The total light transmittance of the optical film can be measured according to JIS K7361-1:1997.

The total light transmittance of the optical film can be adjusted by, for example, the content of light-absorbing materials. When it is desired to increase the total light transmittance of the optical film, for example, it is preferable to set the content of the light-absorbing material to a certain value or less.

(Absorptance Coefficient) The light absorption coefficient A of the optical film is as described above, and the light absorption coefficient A of light with a wavelength of 9.6 μm is preferably 1.5×10 ^-5 /μm or more. When the light absorption coefficient A of the optical film is 1.5×10 ^-5 /μm or more, laser light can be absorbed moderately, so the cutting property by laser light can be improved. The light absorption coefficient A of the optical film is preferably 2.0×10 ^-5 ~50×10 ^-5 /μm, more preferably 5.0×10 ^-5 from the viewpoint of not being easily damaged and transparent, and not easily causing light leakage in the display device ~20×10 ^-5 /μm. The absorption coefficient A of the optical film can be calculated by measuring the absorbance under the above-mentioned conditions using the ATR method as described above.

The light absorption coefficient A of the optical film can be adjusted by the type or content of the light-absorbing material. From the viewpoint of increasing the light absorption coefficient A of the optical film, it is preferable to increase the content of the light-absorbing material.

(Phase difference Ro and Rt) Optical thin films may have retardation values Ro and Rt depending on their usage. For example, when the optical film is used as a zero-retardation film of a polarizing plate, the retardation Ro in the in-plane direction measured at a wavelength of 590nm and an environment of 23°C and 55%RH preferably satisfies 0nm≦Ro≦5nm, and the thickness direction The phase difference Rt preferably satisfies -5nm≦Rt≦5nm.

Ro and Rt of the optical film are respectively defined by the following formulas. Formula (2a): Ro=(nx-ny)×d Formula (2b): Rt=((nx+ny)/2-nz)×d (where, nx represents the refractive index of the in-plane slow axis direction (the direction in which the refractive index becomes the largest) of the optical film, ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the optical film, nz represents the refractive index in the thickness direction of the optical film, d represents the thickness of the optical film (nm))

The in-plane slow axis of an optical film refers to the axis where the refractive index becomes the largest in the film surface. The in-plane slow axis of the optical film can be confirmed with an automatic birefringence meter AxoScan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics).

Ro and Rt of the optical film can be measured by the following method. 1) Condition the optical film for 24 hours in an environment of 23°C and 55%RH. The average refractive index of the optical film was measured with an Abbe refractometer, and the thickness d was measured with a commercially available micrometer. 2) Using an automatic birefringence meter AxoScan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics Co., Ltd.), the retardation Ro and Rt at a measurement wavelength of 590 nm of the optical film after humidity control were measured in an environment of 23° C. and 55% RH.

The retardation Ro and Rt of the optical film can be adjusted mainly by the stretching ratio. When it is desired to increase the retardation Ro and Rt of the optical film, it is preferable to increase the stretching ratio.

(thickness) The thickness of the optical film is not particularly limited, preferably 20-100 μm, more preferably 35-70 μm.

1-4. Manufacturing method The optical film of the present invention can be produced by any method. For example, the optical film 10 having the surface layer 12 (or 13) can be obtained by co-casting the substrate layer 11 and the surface layer 12 (or 13) (co-casting method). After the substrate layer 11 is produced, the surface layer is coated 12 (or 13), and obtained by hardening (coating method).

＜Co-casting method＞ The optical film 10 of the above-mentioned aspect 1 is preferably produced by a co-casting method. The co-casting method may be a solution co-casting method, or may be a melt co-casting method.

(melt co-casting method) Melt co-casting is to co-cast the hot melt of the thermoplastic resin composition for the base layer and the hot melt of the thermoplastic resin composition for the surface layer, and then cool and solidify to obtain a co-cast film. Specifically, the optical film of the present invention can be obtained through the following steps A1) to A3), wherein A1) prepares the thermoplastic resin composition for the substrate layer and the thermoplastic resin composition for the surface layer, A2) prepares the substrate After co-casting the hot melt of the thermoplastic resin composition for the layer and the hot melt of the thermoplastic resin composition for the surface layer, the step of cooling and solidifying, and if necessary, A3) extending the obtained film step.

The step of A1) is to dry mix the ingredients, and then melt and knead them with a twin-screw extruder to obtain granules.

The step of A2) is to melt and knead the particles of the thermoplastic resin composition for the base layer and the thermoplastic resin composition for the surface layer with a two-screw extruder respectively, and then use a cocasting die (cocasting die) co-casting. The melting temperature in melt co-casting is (Tg+30)~(Tg+70)℃ when the glass transition temperature of the resin is Tg.

In the step of A3), stretching may be carried out according to the required optical characteristics, and stretching is preferably carried out in one or more directions among the width direction (TD direction), the conveying direction (MD direction), and the oblique direction.

The elongation ratio is set according to the required optical characteristics, for example, it can be 1.01 to 1.3 times from the viewpoint of the function of producing a low-retardation film. The stretch ratio is defined by (stretching direction of film after stretching)/(stretching direction of film before stretching). Stretching temperature (drying temperature during stretching) is preferably (Tg-20)~(Tg+30)°C.

(Solution co-casting method) Solution co-casting is to co-cast the solution (dope) in which the components for the substrate layer are dissolved in the solvent and the solution (dope) in which the components for the surface layer are dissolved in the solvent, and then dry to obtain a co-cast film. Specifically, the optical film of the present invention can be produced through steps B1) to B3), wherein B1) prepares a dope comprising a cycloolefin resin, a light-absorbing material, and a solvent, and B2) casts the obtained dope After being placed on the support body, drying and peeling are performed to obtain a cast film, and if necessary, B3) a step of extending the obtained cast film.

The step of B1) is dissolving or dispersing the cycloolefin resin and the light absorbing material in a solvent to prepare a glue.

The solvent used contains at least an organic solvent (good solvent) capable of dissolving the cycloolefin resin. Examples of good solvents include chlorine-based organic solvents such as dichloromethane or non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, etc., preferably dichloromethane.

The solvent used may also further contain a weak solvent. Examples of weak solvents include aliphatic alcohols with 1 to 4 carbon atoms such as methanol and ethanol, preferably ethanol. The glue that may further contain aliphatic alcohol tends to gel, so it is easy to peel off from the metal support.

The step of B2) is to spit out the obtained glue from the casting die, etc., and cast it onto the support body. The dope cast on the support was allowed to evaporate the solvent until it could be peeled off from the support by a peeling roller.

Then, the cast film obtained by evaporating the solvent was peeled off with a peeling roll. The amount of residual solvent in the cast film on the support at the time of peeling varies depending on the drying conditions, the length of the support, etc., and may be, for example, 50 to 120% by mass. The residual solvent amount is defined by the following formula. Amount of residual solvent (mass%) = (mass of cast film before heat treatment - mass of cast film after heat treatment) / (mass of cast film after heat treatment) × 100 The heat treatment for measuring the amount of residual solvent is at 115°C for 1 hour.

The step of B3) is to extend the casting film. Stretching ratio or stretching temperature can be the same as the above-mentioned step of A3).

The amount of residual solvent in the cast film at the start of stretching is preferably the same as the amount of residual solvent in the cast film at the time of peeling, for example, preferably 20 to 30% by mass, more preferably 25 to 30% by mass.

＜Coating method＞ The optical film 10 of the above-mentioned aspect 2 is preferably manufactured by a coating method. Specifically, the optical film 10 of Aspect 2 is manufactured through steps C1)~C2), wherein C1) the step of manufacturing the base material layer 11, C2) imparting a light-absorbing material on the obtained base material layer 11 A step of hardening the curable composition of the hardening compound and the hardening agent to form the surface layer 12 (or 13).

In the step of C1), the substrate layer 11 is the same as above, and can be produced by melt casting or solution casting.

In step C2), a curable composition including a light-absorbing curable compound and a curing agent is applied to the surface of the base material layer 11 . The application of the curable composition may be performed by any coating method, for example, roll coating or the like.

Then, the curable composition is cured to obtain the surface layer 12 (or 13). The hardening of the curable composition may be heat hardening or light hardening, preferably light hardening.

1-5. Modified example In addition, in the above-mentioned embodiment, the optical film 10 shows an example having two surface layers (see FIG. 2A ), but is not limited thereto, and may have one surface layer (see FIG. 2B ).

FIG. 2B is a diagram showing the configuration of an optical film 10 according to a modified example. As shown in FIG. 2B , the optical film 10 may have only one surface layer 12 . Especially when the surface layer 12 (or 13) is a cross-linked product containing a curable composition (the above-mentioned aspect 2), the optical film 10 preferably has only one surface layer.

2. Polarizer FIG. 3 is a cross-sectional view showing the structure of the polarizing plate 100 of the present embodiment. In this embodiment, an example using the optical film 10 of FIG. 2A as the optical film 10 is shown.

As shown in Fig. 3, the polarizing plate 100 of the present embodiment has a polarizer 20, the optical film 10 of the present invention arranged on one side thereof, and other optical films 30 arranged on the other side are arranged on the polarizer 20 and the other optical film 30 respectively. A plurality of adhesive layers 40 are arranged between the optical films 10 and between the polarizer 20 and other optical films 30 .

2-1. Polarizer 20 The polarizer is an element that only passes the light of the polarized wave plane in a certain direction, and the polyvinyl alcohol is a polarizing film. Polyvinyl alcohol-based polarizing films include those dyed with iodine and those dyed with dichroic dyes.

The polyvinyl alcohol-based polarizing film can be a film dyed with iodine or a dichroic dye after the polyvinyl alcohol-based film is uniaxially stretched (preferably a film that is subjected to a durability treatment with a boron compound); A polyvinyl alcohol-based film dyed with a dichroic dye is uniaxially stretched (preferably a film subjected to a durability treatment with a boron compound). The absorption axis of the polarizer is parallel to the direction of maximum extension.

The thickness of the polarizer is preferably 5-30 μm, and more preferably 5-20 μm for thinning the polarizer.

2-2. Optical film 10 The optical film of the present invention is arranged on at least one side of the polarizer (at least the side opposite to the liquid crystal cell). Specifically, the optical film 10 of the present invention is disposed so that the surface layer 12 or 13 (in FIG. 3 , the surface layer 12 ) faces the polarizer 20 side.

2-3. Other optical films 30 For other optical films, the optical film 10 of the present invention can also be used, and for other optical films, for example, polarizer protective films can be used. Examples of other optical films include polyester films and cellulose ester films (TAC films, etc.).

2-4. Next layer 40 Then, the layer system is arranged between the optical film 10 (or other optical film 30 ) and the polarizer 20 , so that they are bonded. The adhesive constituting the adhesive layer is not particularly limited, and may be a fully saponified polyvinyl alcohol aqueous solution (water paste) dried or a cured product of an active energy ray-curable adhesive. The active energy ray-curable adhesive may be a photoradical polymerizable composition that utilizes photoradical polymerization, a photocationic polymerizable composition that utilizes photocationic polymerization, or any of these combinations.

The thickness of the bonding layer may be, for example, 0.01-10 μm, preferably about 0.03-5 μm.

2-5. Manufacturing method 4A and B are cross-sectional views showing a method of manufacturing the polarizing plate shown in FIG. 3 .

As shown in Fig. 4A and B, the polarizing plate 100 of the present embodiment is to obtain the optical film 10 of the present invention comprising a polarizer 20 arranged on one side (bonded), and other optical film 10 arranged on the other side (bonded). After the laminate 200 of the thin film 30 (see FIG. 4A ), the obtained laminate 200 is irradiated with laser light L from the optical film 10 side, and the laminate 200 is cut into a predetermined size (see FIG. 4B ).

The lamination of the polarizer 20 and the optical film 10 of the present invention improves the cut-off property by laser light. The surface layer 12 or 13 of the optical film 10 of the present invention has a high light absorption coefficient (in FIG. 2, the surface layer 12) After bonding the polarizer 20 sideways, it is cut into a predetermined size by laser light. Also, bonding can be performed through an adhesive.

Cutting by laser light is to irradiate laser light from the optical film 10 side (in FIG. 4A , the surface layer 13 side of the optical film 10 ). At this time, the optical film 10 has high absorption of laser light on the surface layers 12 and 13, so the optical film 10 can be cut with less irradiation energy. Thereby, the polarizer 20 does not need to be exposed to excessive laser light, so the polarizer 20 will not be burnt due to absorbing too much laser light, and generation of soot can be suppressed. Therefore, contamination of the polarizing plate can be suppressed.

3. Liquid crystal display device The liquid crystal display device of the present invention comprises a liquid crystal cell, a first polarizer arranged on one side of the liquid crystal cell, and a second polarizer arranged on the other side of the liquid crystal cell.

The display mode of the liquid crystal cell is not particularly limited, such as STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment), MVA (Multi- domain Vertical Alignment), PVA (Patterned Vertical Alignment), IPS (In-Plane-Switching), etc. Among them, the IPS mode is preferred.

One or both of the first polarizing plate and the second polarizing plate are the polarizing plate of the present invention. In the polarizing plate of the present invention, it is preferable to arrange the optical film of the present invention on the side of the liquid crystal cell.

As mentioned above, the polarizing plate 100 of the present invention has good cutting property of laser light, not only reduces contamination of the polarizing plate, but also adjusts As/Ac to an appropriate range. Therefore, the calorific value caused by the absorption of laser light in the surface layer 12 (or 13) of the optical film 10 will not be too large relative to the calorific value caused by the absorption of laser light in the base layer 11, so it is difficult to produce the above-mentioned The resulting stress difference. Therefore, light leakage when used as a display device can be suppressed. [Example]

The present invention will be specifically described below by way of examples, but the present invention is not limited thereto.

1. Materials of optical film (1) Cycloolefin resin Prepare the following COP1~6 as cycloolefin resin.

In addition, the structural units A to D derived from the monomer are as follows, respectively.

Tg and Mw of COP1-6 were measured using the following methods.

[Glass transition temperature (Tg)] The glass transition temperature of the resin was measured in accordance with JIS K 7121-2012 using DSC (Differential Scanning Colorimetry: Differential Scanning Calorimetry).

[Weight average molecular weight (Mw)] The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series manufactured by Tosoh Corporation). Dissolve 20±0.5 mg of the sample in 10 ml of tetrahydrofuran, and filter with a 0.45 mm filter. 100 ml of this solution was poured into a column (at a temperature of 40° C.), measured with a detector RI at a temperature of 40° C., and the weight average molecular weight was calculated in terms of styrene.

(2) Light-absorbing material <Light-absorbing material A>

＜Light absorbing material B＞ Methyl methacrylate (MMA)/styrene (St)/ethylene glycol dimethacrylate (EGDMA) (70/10/20 molar ratio) copolymer particles (refractive index 1.51, average particle size 0.14μm)

＜Light absorbing material C＞ Methyl methacrylate (MMA)/styrene (St)/ethylene glycol dimethacrylate (EGDMA) (70/10/20 molar ratio) copolymer particles (refractive index 1.51, average particle size 0.35μm)

＜Light absorbing material D＞ Pentaerythritol tetrabenzoate (molecular weight 552)

＜Light absorbing material E＞ Methyl methacrylate (MMA) / styrene (St) / ethylene glycol dimethacrylate (EGDMA) (70/10/20 molar ratio) copolymer particles (refractive index 1.51, average particle size 0.3 μm)

＜Light absorbing material F＞ Water-based urethane resin (Superflex 210 manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.)

＜Light absorbing material G＞ Urethane acrylate (UA-1100 manufactured by Shin-Nakamura Chemical Co., Ltd.) Isocyanuric acid EO modified di and triacrylate

＜Light absorbing material H＞ (Meth)acrylic resin (MMA/N-phenylmaleimide/2-ethylhexyl methacrylate polymer, Mw800000)

＜Light Absorbing Material I＞ Pentaerythritol tetrabenzoate (molecular weight 552)

The absorptivity of the light absorbing materials A~I with a wavelength of 9.0~11.0 μm was measured by the ATR method, and the measured value was 4.0×10 ^-3 ~6.0×10 ^-3 /μm.

2. Production of optical film <Example 1> (Making of substrate film) Melt knead the resin in Table 2 and 2% by mass of additives relative to the resin, and melt it with a hanger-shaped T-die (width 150mm) using a single-screw extruder (φ=20mm, L/D=25) Extrusion, forming on the film, stretching while conveying, and producing a substrate film (substrate layer) with a thickness of 50 μm.

(formation of surface layer) First, Superflex 210 (water-based urethane resin, light-absorbing material F) manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., adipic acid and epoxy resin as a hardener were dissolved in pure water to obtain a concentration of Superflex 210 of 10 mass % hardening composition.

Next, the above-prepared curable composition was coated on the surface of the obtained substrate film using an extrusion coater, and then dried at 80° C. for 5 minutes to form a surface layer with a thickness of 0.2 μm. Thereby, an optical film having a two-layer structure of base film (base layer)/surface layer was obtained.

<Example 2> (Making of substrate film) In the same manner as in Example 1, a substrate film (substrate layer) having a thickness of 50 μm was obtained.

(formation of surface layer) First, the following materials were stirred and mixed, and then filtered through a polypropylene filter with a pore size of 0.4 μm to obtain a curable composition. Urethane acrylate (UA-1100 manufactured by Shin-Nakamura Chemical Co., Ltd.): 12% by mass Isocyanuric acid EO-modified di- and triacrylates (M-315 manufactured by Toagosei Co., Ltd.): 8% by mass (above, light-absorbing material G) Silica microparticle dispersion (V-8804 manufactured by Nikki Catalyst Chemicals Co., Ltd.): 60 parts by mass IRGACURE184 (manufactured by BASF JAPAN): 2.4% by mass KF-351A (polyether modified silicone oil, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4% by mass Methanol 18% by mass Propylene glycol monomethyl ether acetate (PGME): 12% by mass

Next, apply the curable composition prepared above on the surface of the substrate film using an extrusion coater, dry it at 80°C, and use it while purging it with nitrogen gas in an environment where the oxygen concentration is 1.0% by volume or less. The ultraviolet lamp was used to irradiate ultraviolet rays under the conditions of illuminance of irradiated part 100mW/cm ² and irradiation dose of 0.2J/cm ² to harden and form a surface layer with a thickness of 0.5μm. Thereby, an optical film having a two-layer structure of base film/surface layer was obtained.

<Example 3> (Preparation of particles for substrate layer) The content of the light-absorbing material A is 0.5% by mass. Mix COP1 and the light-absorbing material A with a vacuum Nauta mixer (Nauta Mixer), dry it, and melt it using a 2-axis extruder to obtain a resin mixture. particles.

(Preparation of particles for the surface layer) Except for using the light absorbing material H ((meth)acrylic resin), pellets of the resin mixture were obtained in the same manner as above.

(co-cast) The obtained pellets for the base layer and the pellets for the surface layer were respectively supplied to two twin-screw extruders in a nitrogen atmosphere, melted and co-cast. That is, melt co-casting is performed using a co-extrusion die with the base layer as the center and the surface layers on both sides. The set temperature of the 2-axis extruder is 180°C, and the co-extrusion die is set at 190°C. The co-extrusion mold is a coat hanger type 3-layer laminated type multiple branch pipe mold. Then, the melt-extruded film is pinched and formed between a cooling roll and an elastic touch roll (touch roll), cooled by the cooling roll, and peeled off by a peeling roll to obtain a two-layer structure having a base layer/surface layer. Optical film.

<Examples 4 to 17 and Comparative Example 1> Except changing the compositions and thicknesses of the base layer and the surface layer as shown in Table 2, an optical film having a three-layer structure of surface layer/base layer/surface layer was obtained in the same manner as in Example 3.

<Example 18> (Preparation of light-absorbing material additive solution) 95 parts by mass of dichloromethane was put into an airtight container, and 5 parts by mass of light absorbing material B ((meth)acrylic acid polymer particles) was added with stirring. Then, stir and mix in the dissolver for 50 minutes. 2000 g of the obtained mixed solution was passed through a high-pressure dispersing device (trade name: ultra-high pressure homogenizer M110-E/H, manufactured by Microfluidics Corporation), and treated once at 175 MPa to prepare a light-absorbing material dispersion. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a light-absorbing material additive solution.

(Preparation of glue for the surface layer) A dope of the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. COP6 (cycloolefin resin) and the above-mentioned light-absorbing material additive solution (light-absorbing material) were poured into the above-mentioned pressurized dissolution tank while stirring, and heated and stirred to completely dissolve. This was filtered using Azumi filter paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. to prepare dope. Dichloromethane: 300 parts by mass Ethanol: 19 parts by mass COP6 (cycloolefin resin): 100 parts by mass Light-absorbing material additive solution (light-absorbing material B): 75 parts by mass

(Preparation of glue for substrate layer) In the preparation of the dope mentioned above, the dope was prepared in the same manner except that the light-absorbing material additive liquid was not added.

(film making) Next, using an endless-belt casting device, the glue for the surface layer and the glue for the substrate layer were evenly co-cast on the stainless steel belt support at a temperature of 33° C. and a width of 1500 mm. The temperature of the stainless steel strip is controlled at 30°C. The solvent was evaporated until the amount of residual solvent in the dope co-cast on the stainless steel tape support reached 30% by mass, and then peeled from the stainless steel tape support at a peeling tension of 130 N/m. The cast film obtained by peeling was stretched at an elongation rate of 50% in the width direction (TD direction) under the condition of 160°C (Tg-10°C of the resin). The residual solvent at the start of elongation was 10% by mass. Next, drying was carried out at 130° C. while being conveyed by many rollers in the drying zone. Then, an optical film having a three-layer structure of surface layer/substrate layer/surface layer was obtained by winding.

＜Examples 19~21＞ An optical film was obtained in the same manner as in Example 18, except that the compositions of the substrate layer and the surface layer were changed as shown in Table 2.

<Examples 22 to 26, Comparative Example 10> An optical film having a three-layer structure of surface layer/substrate layer/surface layer was obtained in the same manner as in Example 4, except that the types and thicknesses of the light-absorbing materials of the substrate layer and surface layer were changed as shown in Table 3.

＜Comparative examples 2~4＞ Optical films were obtained in the same manner as Production Examples 3, 4, and 7 of International Publication No. 2018/139638.

＜Comparative example 5＞ An optical film was obtained in the same manner as in Example 4 of International Publication No. 2015/098956.

＜Comparative example 6＞ An optical film (single-layer film) was obtained in the same manner as in Example 12, except that the content of the light-absorbing material E in the substrate layer was changed as shown in Table 3, and no surface layer was formed.

＜Comparative example 7＞ An optical film (single-layer film) was obtained in the same manner as in Comparative Example 6 except that the content of the light-absorbing material B was changed as shown in Table 3.

＜Comparative example 8＞ The thermoplastic resin (J0) used in Production Example 1 of International Publication No. 2018/139638 was dried at 100° C. for 5 hours. The dried thermoplastic resin (J0) is supplied to an extruder and melted in the extruder. The melted thermoplastic resin (J0) passes through a polymer pipe (pipe) and a polymer filter, and is extruded in thin sheets from a T-die onto a casting drum (casting drum). The extruded thermoplastic resin (J0) was cooled to obtain a 70 μm thick base material before stretching. The obtained substrate was stretched 1.4 times to obtain an optical film with a thickness of 50 μm.

＜Comparative example 9＞ The optical film of Comparative Example 8 was coated with the same curable composition as the curable composition of Example 2 except that no light-absorbing material was included, and then dried and cured to form a surface layer to obtain an optical film.

＜Evaluation＞ The absorption coefficient and the presence or absence of bleeding of the obtained optical film were evaluated by the following methods. Bleeding was carried out only for a part of Examples and Comparative Examples.

(1) Ratio of Absorption Coefficient (As/Ac) 1) First, using a microscope FTIR ("UMA600" and "FTS3000" manufactured by Agilent), by ATR method, the incident light path: 100 μm, 騜鏡: Ge (incident angle 45 °), detector: MCT-A, resolution: 4.0cm ^-1 , integration: 64, the infrared absorption spectrum was measured. From the obtained infrared absorption spectrum, the absorbance at a portion corresponding to a wavelength of 9.6 µm (frequency 1041 cm ^-1 ) was read to obtain the absorbance A of the entire optical film. 2) Next, cut 30% of the thickness from one side a of the optical film. Then, the absorbance A1 of the cut surface was measured in the same manner as in the above 1). 3) Also, cut 30% of the thickness from the other side b of the optical film. Then, the absorbance A2 of the cut surface was measured in the same manner as in 1) above. 4) Put the absorbance A, A1 and A2 obtained in the above 1) to 3) into the following formula to calculate the light absorption coefficient As of the surface area and the light absorption coefficient Ac of the inner area respectively. Surface absorption coefficient As=(A-A1)×loge10÷(0.3T) Internal absorption coefficient Ac=A2×loge10÷(0.4T) (T: Thickness of optical film A: Absorbance of optical film A1: From one side of optical film 10a, the absorbance measured by cutting 30% of the thickness T of the optical film A2: the absorbance measured by cutting 30% of the thickness T of the optical film from the other surface 10b of the optical film)

(2) Seepage The obtained film was put into a high-temperature heating device (thermo) at 90° C. and a humid heat heating device at 80° C. 90% RH for 3000 hours. After taking it out at any time, observe whether there are precipitates on the surface of the film. Observations were made in a dark room under a green light. Then, the time required until the precipitate was observed is shown in Tables 2 and 3.

Moreover, using the obtained optical film, a polarizing plate and a display device were produced. Then, the polarizing plate quality and light leakage were evaluated by the following methods.

(3) Evaluation of polarizers (quality of polarizers) (Making of Polarizers) A PVA resin film with a degree of polymerization of 2400, a degree of saponification of 99.7 mol%, and a thickness of 75 μm was prepared. The film was stretched 3 times in the film conveying direction while being dyed in an iodine aqueous solution at 30°C, and then the total stretching ratio was brought to the original length in 4 mass % boric acid and 5 mass % potassium iodide aqueous solution at 60 °C. 6 times to extend. In addition, the stretched film was dipped in a 2% by mass potassium iodide aqueous solution at 30° C. for several seconds and washed. The obtained stretched film was dried at 90° C. to obtain a polarizer.

(Production of Polarizing Plate) On the surface layer (or light-absorbing layer) of the optical film, the adhesive agent is interposed, and the polarizer is pasted, and the adhesive agent is interposed on the back side, and the PET film is pasted to make a polarizing plate.

(Laser cutting property) The obtained polarizing plate was irradiated on the optical film with a carbon dioxide laser having a wavelength of 9.6 μm, and the polarizing plate was cut. Cutting conditions were frequency 20 kHz, output: 59 W, and speed: 60 m/min. Microscopically confirmed and evaluated the vicinity of the surface with a cut length of 10 cm. S: No pollution or soot at all A: Pollution or soot can be seen slightly only at the cut part B: Pollution or soot is slightly visible only around the cut portion C: Pollution or soot is evident, but washable ×: Severely polluted and unusable When C or more, it judged as favorable.

(4) Evaluation of display devices (light leakage) First, carefully peel off the polarizing plate of Wooo W32L-H90, a liquid crystal display device manufactured by Hitachi, which has been attached to the IPS liquid crystal display device in advance. Then, stick the laser-cut polarizing plate in line with the penetration axis of the previously attached polarizing plate to make a liquid crystal display device. The lamination of the laser-cut polarizing plate is carried out by making the optical film of the present invention the side of the liquid crystal cell.

Then, the obtained liquid crystal display device was visually observed in a dark room in a state where the entire surface was displayed in black, and 10 persons evaluated the light leakage at the edge. SS: None of the 10 people saw the light leak at all S: 1 out of 10 people can see faint light leakage A: 2~3 out of 10 people can see weak light leakage B: 4~6 out of 10 people can see faint light leakage C: Out of 10 persons, 7 or more persons could see faint light leakage. There is no problem practically. ×: Strong light leakage can be seen by 10 people When C or more, it judged as favorable.

The compositions and evaluation results of the optical films of Examples 1-21 are shown in Table 2, and the compositions and evaluation results of the optical films of Examples 22-26 and Comparative Examples 1-10 are shown in Table 3.

As shown in Tables 2 and 3, the optical films of Examples 1 to 26 with the light absorption ratio As/Ac adjusted to 1.1 to 20 have good laser cutting properties and high quality polarizers (less contamination). Also, it was found that the obtained display device had no light leakage.

On the other hand, the optical films of Comparative Examples 1 to 3 and 6 to 8 in which the absorptivity ratio As/Ac was less than 1.1 showed poor laser cutting properties and poor quality of polarizing plates. As for the optical films of Comparative Examples 4, 5, 9, and 10 whose As/Sc exceeds 20, it is known that light leakage occurs in the display device.

This application claims priority based on Japanese Patent Application No. 2020-128426 filed on July 29, 2020. All the content recorded in the petition statement and drawings are quoted in the statement of this case. [Industrial availability]

According to the present invention, it is possible to provide an optical film, a polarizing plate, and a liquid crystal display device capable of cutting off by laser light without causing light leakage in a display device.

10:Optical film 11: Substrate layer 12,13: surface layer 20: Polarizer 30:Other optical films 40: Next layer 100: polarizer 200: laminate Sa, Sb: surface area C: inner area L: laser light

[Fig. 1] Fig. 1 is a schematic cross-sectional view showing the surface layer region and the inner layer region of an optical film. [FIG. 2] FIG. 2A is a cross-sectional view showing the structure of the optical film of this embodiment, and FIG. 2B is a cross-sectional view showing the structure of the optical film of the modified example. [ Fig. 3] Fig. 3 is a cross-sectional view showing the configuration of a polarizing plate according to this embodiment. [FIG. 4] FIGS. 4A and B are cross-sectional views showing a method of manufacturing the polarizing plate shown in FIG. 3. [FIG.

10:Optical film

Sa, Sb: surface area

C: inner area

Claims (13)

An optical film, which is an optical film comprising a cycloolefin resin, the area from one surface of the optical film to the depth of 30% of the thickness of the optical film is defined as the surface area (Sa), and the area from the other surface of the optical film to the optical When the area at the depth of 30% of the thickness of the film is the surface area (Sb), and the area between the aforementioned surface area (Sa) and the aforementioned surface area (Sb) is the inner area (C), at least the aforementioned surface area (Sa) The ratio As/Ac of the absorption coefficient As of the light with a wavelength of 9.6 μm measured by the ATR method and the absorption coefficient Ac of the light of the wavelength of 9.6 μm measured by the ATR method in the inner layer region (C) As/Ac is 1.1~20. The film has an absorption coefficient of light with a wavelength of 9.6 μm of 1.5×10 ^-5 /μm or more. The optical film according to claim 1, wherein the aforementioned ratio As/Ac is 3-15. The optical film according to claim 1, wherein the surface region (Sa) and the inner region (C) respectively contain light-absorbing materials with an absorption coefficient of 4.0×10 ^-3 /μm or more for light with a wavelength of 9.6 μm. The optical film according to claim 3, wherein the content Ms of the light-absorbing material in the surface region (Sa) is greater than the content Mc of the light-absorbing material in the inner layer region (C). Such as the optical film of claim 4, wherein Ms/Mc is 2.5~20. Such as the optical film of any one of claims 3 to 5, which is A substrate layer comprising a cycloolefin resin and the light-absorbing material, and at least one side of the substrate layer, comprising a cycloolefin resin and the light-absorbing material, or a (meth)acrylic resin as the light-absorbing material In the surface layer, the content of the light-absorbing material Ms' in the surface layer is greater than the content Mc' of the light-absorbing material in the base layer. Such as the optical film of claim 6, wherein Ms'/Mc' is 2.5~50. The optical film according to any one of Claims 3 to 5, which has a substrate layer comprising the aforementioned cycloolefin resin and the aforementioned light-absorbing material, and is laminated on at least one side of the aforementioned substrate layer, and comprises the aforementioned light-absorbing material as A surface layer composed of a cured product of a curable composition of a hardening compound and a hardening agent, wherein the hardening compound is a urethane compound having a group reactive with the hardening agent. The optical film according to claim 8, wherein the light-absorbing material comprises ester compounds or (meth)acrylic polymer particles. The optical film according to claim 9, wherein the light-absorbing material is a sugar ester compound. A polarizing plate, which has a polarizer, and the optical film according to any one of claims 1-10 arranged on at least one side of the polarizer. The polarizing plate according to claim 11, wherein the surface contained in the surface region (Sa) of the optical film is bonded to the polarizer. A liquid crystal display device comprising a liquid crystal cell, a first polarizer and a second polarizer holding the liquid crystal cell, at least one of the first polarizer and the second polarizer is the polarizer according to claim 11 or 12.

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