KR20210029113A - Optical film, polarizing plate, and organic el display device - Google Patents

Abstract

An optical film contains a cycloolefin-based polymer having a structural unit derived from a norbornene-based monomer having an ester-containing group, and a dye compound represented by chemical formula (1). The thermal expansion coefficient measured in the range of 50-120°C in the direction of 45° with respect to the in-plane slow axis of the optical film is 100 ppm/°C or less.

Description

Optical film, polarizing plate, and organic EL display device TECHNICAL FIELD

The present invention relates to an optical film, a polarizing plate, and an organic EL display device.

An organic EL display device usually includes an organic EL element in which a metal electrode (cathode), a light emitting layer, a transparent electrode (anode), and a transparent substrate (sealing layer) are stacked in this order. In such an organic EL display device, not only the light emitted from the light emitting layer but also the external light incident through the transparent substrate is mirror-reflected from the surface of the metal electrode and is extracted as the exit light, so that external light such as indoor lighting is projected and the visibility is easily deteriorated. In order to suppress such a decrease in visibility due to projection of external light, a circularly polarizing plate is usually disposed on the visual side of the organic EL element.

The circularly polarizing plate has a polarizer and a λ/4 retardation film disposed between the polarizer and the organic EL element. As the λ/4 retardation film, for example, a cellulose ester film, a cycloolefin resin film, a polycarbonate film, a polyester film, or the like is used.

In addition, in the organic EL display device, there is a problem that the organic EL element or the like is liable to deteriorate due to external light. In order to suppress the deterioration of the organic EL element due to such external light, in an organic EL display device having an organic EL element and a circularly polarizing plate, an organic EL containing a light-absorbing dye in at least one of a plurality of functional layers constituting the circularly polarizing plate A display device has been proposed (for example, Patent Document 1).

In addition, it is an organic EL display device having a polarizing plate having a first adhesive layer, a protective film, a polarizer, a second adhesive layer, a retardation film, and a third adhesive layer in this order, and a first adhesive layer, a second adhesive layer, and a third adhesive layer. An organic EL display device in which a dye compound having an absorption wavelength of 380 to 430 nm is contained in any of the pressure-sensitive adhesive layers has been proposed (for example, Patent Document 2).

Japanese Patent Publication No. 2017-198991 Japanese Patent Publication No. 2017-165941

By the way, as a λ/4 retardation film, a cycloolefin resin film may be used from the viewpoint of having low hygroscopicity and good dimensional stability.

However, since the cycloolefin resin film exhibits a flat wavelength dispersion characteristic, for example, when used as a λ/4 retardation film of a circular polarizing plate in an organic EL display device, the reflected light is reduced in a specific wavelength region (short wavelength side region). It is easy to leak. If the leakage of such reflected light is significant, the color of the reflected light is liable to deteriorate.

In order to suppress such a decrease in the color sense of the reflected light, the inventors of the present invention investigated adding a dye compound that absorbs light in the wavelength region to a film, and found a new problem that the thermal expansion coefficient of the film is thereby increased. A polarizing plate comprising an optical film having a large coefficient of thermal expansion is liable to bend (easy to curl) under high temperature and high humidity, and is liable to cause display unevenness in an organic EL display device.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical film, a polarizing plate, and an organic EL display device capable of suppressing a decrease in color sense of reflected light of an organic EL display device without increasing a coefficient of thermal expansion.

The above problem can be solved by the following configuration.

The optical film of the present invention is an optical film comprising a cycloolefin-based polymer having a structural unit derived from a norbornene-based monomer having an ester-containing group, and a dye compound represented by the following formula (1), and the surface of the optical film The coefficient of thermal expansion measured in the range of 50 to 120°C in the direction of 45° with respect to the inner slow axis is 100 ppm/°C or less.

(In formula (1),

R ₁ is a hydrogen atom, a cyano group or an alkyl group,

R ₂ is a hydrogen atom or a substituent,

m is a natural number from 1 to 5,

Y is an electron withdrawing group,

Z is a group represented by any of the following formulas (2) to (4))

(In formulas (2) to (4),

R ₃ to R ₅ are each a hydrogen atom or a substituted or unsubstituted alkyl group,

R ₆ to R ₈ are each a substituted or unsubstituted alkyl group, or an organic group including N, O, S or two or more of them,

n is each an integer of 0 to 4,

p is an integer from 0 to 5,

q is an integer from 0 to 3)

The polarizing plate of the present invention is a polarizing plate having a polarizer and an optical film of the present invention disposed on at least one side thereof, and the reflectance of light having a wavelength of 460 nm of the polarizing plate when the aluminum reflector is fixed on the optical film is T1, and the wavelength is 650 nm. When the reflectance of light of is T2, the following equation (5) is satisfied.

Equation (5): 0<T1/T2<2.6

The organic EL display device of the present invention has an organic EL element and a polarizing plate of the present invention, and the optical film is disposed between the organic EL element and the polarizer.

According to the present invention, it is possible to provide an optical film, a polarizing plate, and an organic EL display device capable of suppressing a decrease in color sense of reflected light of an organic EL display device without increasing a coefficient of thermal expansion.

1A is a cross-sectional view showing a configuration of a polarizing plate, and FIG. 1B is an exploded perspective view showing an arrangement relationship between a polarizer constituting a polarizing plate and each film.
2 is an exploded cross-sectional view of an organic EL display device.

The inventors of the present invention believe that the optical film containing the dye compound (specific dye compound) represented by the following formula (1) has a thermal expansion coefficient that is a problem when it contains a conventional dye compound as disclosed in Patent Documents 1 or 2. It has been found that the increase can be suppressed, thereby suppressing heating during processing of the polarizing plate and curling of the polarizing plate when the display device having the polarizing plate is stored under high temperature and high humidity.

Although this reason is not clear, it is estimated as follows. That is, the carbonyl group of the cycloolefin-based polymer having an ester-containing group is polarized into C δ+ and O δ-. On the other hand, in the specific dye compound having a conjugated system as represented by the formula (1), electrons are localized and the portion is in an electron-rich state. Therefore, an electrostatic interaction occurs between C δ+ of the carbonyl group of the ester-containing group of the cycloolefin polymer and the conjugated portion of the electron of the dye compound. It is considered that the intermolecular free volume of the cycloolefin-based polymer decreases due to this interaction, and the Van der Waals force increases, so that the coefficient of thermal expansion decreases. That is, by combining the "cycloolefin-based polymer having an ester-containing group" and the "specific dye compound having a conjugated system", the free volume between molecules can be reduced and the thermal expansion coefficient of the film can be reduced.

In order to generate such an interaction, it is preferable to further cause polarization of the double bond portion, and for that purpose, it is preferable that one end group Y of the double bond portion of formula (1) is an electron withdrawing group, and R ₁ is a cyano group Or an alkyl group is more preferable (rather than a hydrogen atom). In addition, the other end group Z of the double bond portion is not particularly limited, but from the viewpoint of forming a structure that absorbs light in a specific wavelength range and allowing it to enter between molecules of the cycloolefin-based polymer, the excluded volume It is preferable that it is a ring-containing group that is not too large (that is, a group represented by formulas (2) to (4)). Hereinafter, the present invention will be described.

1. Optical film

The optical film of the present invention contains a cycloolefin-based polymer and a specific dye compound.

1-1. Cycloolefin polymer

The cycloolefin-based polymer is a polymer containing a structural unit derived from a norbornene-based monomer having an ester-containing group.

The norbornene-based monomer having an ester-containing group is represented by the following formula (6).

It is preferable that at least one ^{of R 1} to R ⁴ in formula (6) is an ester-containing group. Examples of the ester-containing group include groups to which these groups are bonded through a linking group such as an alkoxycarbonyl group, an aryloxycarbonyl group, and a methylene group. The cycloolefin-based polymer having a structural unit derived from a norbornene-based monomer having such an ester-containing group is not only easily dissolved in a solvent when forming a film by a solution casting method, but also can increase the glass transition temperature of the obtained film. Among these, the ester-containing group is preferably an alkoxycarbonyl group, and more preferably an alkoxycarbonyl group having 1 to 10 carbon atoms.

It is preferable that the rest of R ¹ to R ⁴ are each a hydrogen atom or a hydrocarbon group. The hydrocarbon group may be a hydrocarbon group having 1 to 10, preferably 1 to 4, more preferably 1 or 2 carbon atoms. Examples of the hydrocarbon group include an alkyl group and an aryl group. The hydrocarbon group may further have a substituent. Examples of the substituent include polar groups such as a carboxyl group, a hydroxy group, an amino group, an amide group, and a cyano group.

For example, R ^{1 in} formula (6) may be an ester-containing group, and R ² , R ³ and R ⁴ may each be a hydrogen atom or a hydrocarbon group; R ¹ and R ³ are each an ester-containing group, and R ² and R ⁴ may each be a hydrogen atom or a hydrocarbon group.

p and m are each an integer of 0 to 3. Among these, m+p is preferably 0 to 4, more preferably 0 to 2, and even more preferably m = 1 and p = 0. A cycloolefin-based polymer containing a structural unit derived from a norbornene-based monomer having an ester-containing group of m = 1 and p = 0 can provide an optical film having a high glass transition temperature and good mechanical strength.

Examples of the norbornene-based monomer having an ester-containing group include the following.

The content of the structural unit derived from the norbornene-based monomer having an ester-containing group is preferably 20 to 100% by mass, and more preferably 30 to 100% by mass with respect to all structural units constituting the cycloolefin-based polymer.

The cycloolefin-based polymer may further contain a structural unit derived from another monomer copolymerizable with a norbornene-based monomer having an ester-containing group.

Examples of other copolymerizable monomers include cycloolefin-based monomers having no norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene. Among these, the number of carbon atoms in the cycloolefin-based monomer is preferably 4 to 20, and more preferably 5 to 12.

As the cycloolefin-based polymer, a commercial item may be used. Examples of commercial products include Aton (ARTON: a registered trademark) G, Aton F, Aton R, and Aton RX manufactured by JSR.

The weight average molecular weight Mw of the cycloolefin-based polymer is not particularly limited, but it is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and still more preferably 40,000 to 200,000. When the weight average molecular weight Mw of the cycloolefin-based polymer is in the above range, the mechanical properties of the optical film can be improved without impairing the molding processability.

The weight average molecular weight Mw of the cycloolefin-based polymer can be measured by gel permeation chromatography (GPC).

Specifically, gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) was used as a measuring device, and TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation was serially used as a column.

Then, 20±0.5 mg of a sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was poured into the column (temperature 40° C.), measured at a detector RI, temperature 40° C., and converted into styrene to obtain a weight average molecular weight.

The glass transition temperature Tg of the cycloolefin-based polymer is usually preferably 110°C or higher, more preferably 110 to 350°C, and even more preferably 120 to 250°C. When the Tg of the cycloolefin-based polymer is 110° C. or higher, deformation is difficult to occur even under high temperature conditions. If the Tg is 350°C or less, it is difficult to impair the molding processability, and the thermal deterioration of the cycloolefin-based polymer during molding processing can be further suppressed.

The glass transition temperature can be measured by a method conforming to JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

The number of cycloolefin-based polymers may be used alone or in combination of two or more.

1-2. Pigment compound

The dye compound may be a compound represented by formula (1).

In formula (1), R ₁ is a cyano group or an alkyl group. The alkyl group may be preferably an alkyl group having 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. Among them, it is preferable that _{R 1} is a cyano group from the viewpoint of facilitating polarization of the double bond portion.

R ₂ is a hydrogen atom or an alkyl group. Among them, R ₂ is preferably a hydrogen atom from the viewpoint of making it difficult to cause steric hindrance with Z.

m is a natural number from 1 to 5. Especially, it is preferable that m is 1 from the viewpoint of making it easy to interact with the ester-containing group of the cycloolefin-based polymer by not making the volume to be excluded from the dye compound too large.

Y is an electron withdrawing group. Examples of the electron withdrawing group include a cyano group, a nitro group, an aldehyde group (-C(=O)H), an alkoxycarbonyl group, an aryloxycarbonyl group (-C(=O)OR, R is an alkyl group or an aryl group). Among them, from the viewpoint of being easy to interact with the ester-containing group of the cycloolefin-based polymer because it has high electron attraction and easy to properly polarize the double bonded portion, and from the viewpoint that it is easy to enter between the molecules of the cycloolefin-based polymer because the steric hindrance is not too large. And the electron withdrawing group is preferably a cyano group or an alkoxycarbonyl group, and more preferably a cyano group.

Z is a group represented by any of the following formulas (2) to (4).

In formulas (2) to (4), R ₃ to R ₅ are each a hydrogen atom or a substituted or unsubstituted alkyl group. Each of R ₆ to R ₈ is a substituted or unsubstituted alkyl group, or an organic group containing two or more of N (nitrogen atom), O (oxygen atom), S (sulfur atom). Examples of the organic group include a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, and -NR'R". Examples of the substituents that the alkyl group or alkoxy group may have include a substituted or unsubstituted aryloxy group, a substituted Or an unsubstituted heteroaryloxy group is included. R'and R" in -NR'R" may each be a substituted or unsubstituted alkyl group.

In addition, n is an integer of 0 to 4, p is an integer of 0 to 5, and q is an integer of 0 to 3. When there are a plurality of R ₃ to R ₈ respectively, they may be the same or different.

Among these, it is preferable that Z is a group represented by formula (2) or (4). The following are included in a preferable example of the group represented by Formula (4).

In the above formula, R ₉ may be an alkylene group having 1 to 7 carbon atoms or an arylene group having 6 to 7 carbon atoms.

Examples of the compound represented by formula (1) include the following.

(* indicates bonding position)

The molecular weight of the dye compound is not particularly limited, but it is preferably not too large, and for example, it is preferably 100 to 1000 in order to easily enter the cycloolefin-based polymer between molecules. The molecular weight of the dye compound can be calculated from the food of the chemical structural formula by specifying a chemical structure by, for example, NMR or the like.

The maximum absorption wavelength of the dye compound is preferably 370 to 460 nm, more preferably 400 to 440 nm. When the maximum absorption wavelength of the dye compound is within the above range, since the optical film is likely to adequately absorb light in the wavelength range, for example, when the optical film is used as a λ/4 retardation film in an organic EL display device , Leakage of reflected light in the wavelength region can be further suppressed. The maximum absorption wavelength of the dye compound can be determined by measuring the absorption spectrum of the dye compound in dichloromethane using an ultraviolet-visible spectrophotometer UV-2450 manufactured by Shimadzu Corporation.

The dye compound may be synthesized and obtained, or a commercial item may be used. Examples of commercially available products include Yamada Chemical Co., Ltd. FDB-003 (maximum absorption wavelength 438 nm) and FDB-004 (maximum absorption wavelength 445 nm). For example, synthesis of a dye compound in which Y is -COOR, Z is a group represented by formula (4), and R ₁ is R can be synthesized by, for example, the following method.

In the above reaction, compound III can be obtained by, for example, dehydrating condensation reaction of compound I and compound II.

The content of the dye compound is preferably 0.01 to 3% by mass based on the cycloolefin-based polymer. When the content of the dye compound is 0.01% by mass or more, it is possible to adequately absorb light in a specific wavelength region and sufficiently suppress an increase in the coefficient of thermal expansion of the optical film, while suppressing leakage of reflected light in, for example, an organic EL display device. have. When the content of the dye compound is 3% by mass or less, not only can bleed-out be difficult to occur, but also the decrease in luminance can be suppressed because the absorption of light in a specific wavelength region of the optical film is not too high. From the same viewpoint, the content of the dye compound is more preferably 0.015 to 2% by mass with respect to the cycloolefin-based polymer.

1-3. Other ingredients

The optical film of the present invention may further contain components other than the above within a range not impairing the effects of the present invention. Examples of other components include a mat agent, an ultraviolet absorber, a phase difference adjuster (a phase difference increasing agent, a phase difference reducing agent), a plasticizer, an antioxidant, a light stabilizer, an antistatic agent, a release agent, and a thickener. Among them, it is preferable that the optical film contains a matting agent from the viewpoint of imparting unevenness to the surface of the optical film and imparting an appropriate sliding property.

(Mat)

The mat agent is fine particles. The fine particles may be inorganic fine particles or resin fine particles. Examples of inorganic fine particles include fine particles of inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Is included. Among them, the inorganic fine particles are preferably silicon dioxide fine particles from the viewpoint of being difficult to increase the haze of the optical film and effectively lowering the coefficient of friction.

Examples of the silicon dioxide fine particles include Aerosil 200V, Aerosil R972V, and Aerosil R812 (above made by Nippon Aerosil Co., Ltd.).

Examples of the resin fine particles include fine particles such as a silicone resin, a fluororesin, and an acrylic resin. Among them, silicone resin fine particles are preferable, and resin fine particles having a three-dimensional network structure are particularly preferable. Examples of the resin fine particles include Toss Pearl 103, Copper 105, Copper 108, Copper 120, Copper 145, Copper 3120, and Copper 240 (manufactured by Toshiba Silicon Co., Ltd.).

The average particle diameter of the primary particles of the fine particles is preferably 0.005 to 0.4 µm, more preferably 0.01 to 0.3 µm. These fine particles may be contained as secondary aggregates having a particle diameter of 0.05 to 0.3 µm.

It is preferable that it is 0.01-3.0 mass% with respect to an optical film, and, as for content of a fine particle, it is more preferable that it is 0.01-2.0 mass %. In addition, it is preferable that the coefficient of kinetic friction on the surface of the optical film is 0.2 to 1.0.

1-4. Floor composition

The optical film of the present invention may be composed of a single layer or may be composed of multiple layers. When the optical film of the present invention is composed of multiple layers, for example, it may have a base layer including a cycloolefin-based polymer and another layer disposed thereon.

Examples of other layers include an easy-to-adhesion layer for enhancing adhesiveness with a polarizer. The easy-adhesion layer may be disposed only on one side of the substrate layer or may be disposed on both sides as necessary.

(Easy adhesion layer)

The easy-adhesion layer may include any material capable of improving adhesion or adhesion to a polarizer. Such materials include resins such as polyurethane, polyolefin, polyester, polyvinylidene chloride, acrylic polymer, modified silicone polymer, styrene butadiene rubber, carbodiimide compound, and isocyanate.

Examples of polyurethanes include DIC Co., Ltd.'s brand name "Hyran series" AP-201, AP-40F, HW-140SF, WLS-202, Daiichi Kogyo Seyaku Co., Ltd. brand name "Super Flex Series" SF-210 , SF-460, SF-870, SF-420, SF-420NS, Mitsui Chemical Co., Ltd. brand name "Takelag series" W-615, W-6010, W-6020, W-6061, W-405, W-5030, W-5661, W-512A-6, W-635, WPB-6601, WS-6021, WS-5000, WS-5100, WS-4000, WSA-5920, WF-764, Adeka ), the developed product "SPX-0882" is included. Further, a resin such as polyurethane having a carboxyl group in the side chain can be crosslinked with a crosslinking agent such as isocyanate, oxazoline, or carbodiimide, thereby improving the strength of the easily bonding layer.

Examples of polyolefins include the brand name "Allobase Series" manufactured by Unitika Corporation SE-1010, SE-1013N, SE-1030N, SD-1010, TC-4010, TD-4010, and "Hi-Tech Series" manufactured by Toho Chemical Corporation. '' S3148, S3121, S8512, P-5060N, P-9018, Mitsui Chemical Co., Ltd. brand name "Unistol series" S-120, S-75N, V100, H-200, H-300, EV210H, Mitsui Kaga Co., Ltd. brand name "Chemi-pearl series" XHP-400, Sumitomo Seika Co., Ltd. brand name "Saiksen series" Saiksen A, Saiksen L, Toyobo brand name "Hadelen series" NZ-1004 , NZ-1005, and NZ-1022.

Examples of polyester include the brand names of Toyobo Co., Ltd. "Vironal Series" MD1400, MD1480, MD1245, MD1500, and the brand names "Plascote Series" manufactured by Kogaku Kogyo Co., Ltd. Z-221, Z-561, Z-730, RZ-142, and Z-687 are included. Examples of polyvinylidene chloride include Asahi Kasei Co., Ltd. brand name "Saran Latex Series" L509. Examples of acrylic polymers include Nippon Shokubai Co., Ltd. brand name "Epocross WS series" WS-700, Shin Nakamura Chemical Co., Ltd. brand name "Newcoat series" developed product CP-0101. Examples of the modified silicone-based polymer include DIC Corporation brand names "Seranate Series" WSA1060, WSA1070, and Asahi Kasei Chemicals Corporation H7620, H7630, and H7650. Examples of the styrene butadiene rubber include Nippon Xeon Corporation's NIPOL LX415, NIPOL LX407, NIPOL V1004, NIPOL MH8101, and SX1105. Examples of the carbodiimide compound include Nisshinbo Chemical Co., Ltd. brand names "Carbodilite series" V-02, V-02-L2, SV-02, V-04, and E-02. Examples of the isocyanate compound include compounds containing two or more isocyanate groups per molecule, such as hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate. Further, the isocyanate may have been subjected to a masking process using a blocking agent.

The easy-adhesion layer may further contain fine particles as necessary in order to impart anti-blocking properties. Examples of fine particles include Nippon Shokubai Co., Ltd. "Seahosta series" KE-P20 and KE-P30, developed product KE-W20, and "Eposta series" MX100W. The average particle diameter of the fine particles is preferably 50 to 500 nm, more preferably 100 to 300 nm. When the average particle diameter of the fine particles is within the above range, the transparency of the easy-to-adhesive layer and anti-blocking properties can be achieved.

The easy-adhesion layer may further contain arbitrary additives as needed. Examples of additives include leveling agents, photoinitiators, thermal polymerization initiators, polymerization accelerators, viscosity modifiers, slip agents, dispersants, plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers. , A crosslinking agent is included. The content of the additive is, for example, 30% by mass or less, preferably 20% by mass or less with respect to the easily bonding layer.

The glass transition temperature Tg of the easily bonding layer is preferably -40 to 130°C, more preferably -30 to 50°C, and still more preferably 0 to 20°C. The glass transition temperature can be measured by reading the maximum value of the loss tangent (tanδ) by dynamic viscoelasticity measurement.

The thickness of the easily bonding layer is not particularly limited, but is preferably 0.01 to 0.1 µm, and more preferably 0.02 to 0.5 µm.

1-5. Properties

(Coefficient of thermal expansion)

It is preferable that the thermal expansion coefficient (linear expansion coefficient) measured in the range of 50 to 120°C in the direction of 45° with respect to the in-plane slow axis of the optical film is 100 ppm/°C or less. If the thermal expansion coefficient of the optical film is 100 ppm/°C or less, for example, even when exposed to high temperatures by drying or heating for curing the adhesive during manufacture of the polarizing plate, the thermal expansion of the optical film can be reduced. The curl of the polarizing plate caused by can be suppressed. It is more preferable that it is 90 ppm/degreeC or less, and, as for the thermal expansion coefficient of an optical film, it is still more preferable that it is 40-85 ppm/degreeC.

The coefficient of thermal expansion of the optical film can be measured according to the method of testing the coefficient of linear expansion by thermomechanical analysis of JIS K 7197:1991 plastics. Specifically, the optical film is cut out to a size of 10 mm (length) x 1 mm (width) to obtain a sample film. When the obtained sample film was heated and lowered at 10° C./min in the range of 30 to 140° C. using a TMA (thermo-mechanical analysis) tester (TMA7100 manufactured by Hitachi High-Tech Science) in a 23° C. environment, 50 to 120° C. The amount of dimensional change Δl in the range is measured. The obtained dimensional change amount Δl is applied to the following equation to calculate the coefficient of thermal expansion α (ppm/°C).

(l: length of the sample film (length in the vertical direction; 10 mm)

Δt: change in temperature (70℃)

Δl: the amount of dimensional change of the sample film)

(Haze)

It is preferable that it is 2.0 or less, and, as for the haze of an optical film, it is more preferable that it is 1.0 or less. The haze of the optical film can be measured using a haze meter (NDH 2000: manufactured by Nippon Denshoku Kogyo Co., Ltd.) after conditioning for 24 hours in an environment of 25°C and 60% RH.

(Glass transition temperature)

It is preferable that the glass transition temperature Tg of an optical film is 110-250 degreeC, for example. When Tg of an optical film is 110 degreeC or more, heat resistance of an optical film can be improved. When the Tg of the optical film is 250°C or less, it is difficult to impair workability such as further stretching of the optical film. The glass transition temperature of the optical film can be measured by a method similar to the above.

The glass transition temperature of the optical film is adjusted, for example, by the monomer composition of the cycloolefin-based polymer.

(Phase difference Ro and Rt)

From the viewpoint of using the optical film as, for example, a λ/4 retardation film, the retardation Ro in the in-plane direction measured in an environment of a measurement wavelength of 550 nm and 23° C. 55% RH is preferably 100 to 170 nm, and is 130 to 150 nm. It is more preferable.

Ro is defined by the following formula.

Equation (7): Ro=(nx-ny)×d

(In equation (7),

nx represents the refractive index of the film in the in-plane slow axis direction (the direction in which the refractive index becomes the maximum),

ny represents the refractive index in a direction orthogonal to the in-plane slow axis of the film,

d represents the thickness (nm) of the film)

The in-plane slow axis of the optical film can be confirmed by an automatic birefringence meter Axo Scan (manufactured by Axo Scan Mueller Matrix Polarimeter). When the optical film is used as a λ/4 retardation film, the angle of the in-plane slow axis of the optical film with respect to the width direction of the optical film is preferably 40 to 50°, more preferably 43 to 47°.

Ro can be measured by the following method.

1) The optical film is humidified in an environment of 23°C and 55% RH for 24 hours. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) Measurement of the film after humidity control The retardation Ro at a wavelength of 550 nm is measured in an environment of 23°C and 55% RH using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter).

The retardation Ro of the optical film can be adjusted by, for example, the monomer composition of the cycloolefin-based polymer and stretching conditions.

(Amount of residual solvent)

The optical film may further contain a residual solvent in that it is preferably formed by a solution casting method. It is preferable that it is 700 ppm or less with respect to an optical film, and, as for the amount of residual solvent, it is more preferable that it is 30-700 ppm. The content of the residual solvent can be adjusted by the drying conditions of the dope cast on the support in the manufacturing process of the optical film.

The amount of residual solvent in the optical film can be measured by head space gas chromatography. In the headspace gas chromatography method, a sample is enclosed in a container and heated, and the gas in the container is rapidly injected into a gas chromatograph while the container is filled with volatile components, and the volatile component is identified while performing mass spectrometry. It is to quantify. In the head space method, it is possible to observe all peaks of volatile components by a gas chromatograph, and by using an analysis method using electromagnetic interaction, it is possible to quantify volatile substances and monomers with high precision.

(thickness)

Although the thickness of the optical film is not particularly limited, it is preferably 10 to 80 µm, and more preferably 10 to 60 µm.

2. Manufacturing method of optical film

The optical film of the present invention includes 1) a step of preparing a dope containing the cycloolefin-based polymer, the dye compound, and a solvent, 2) casting the obtained dope on a support, followed by drying and peeling to obtain a cast film, And 3) a process of stretching the obtained cast film. In addition, the optical film of the present invention may be further produced through 4) a step of drying the stretched cast film, 5) a step of cutting the both ends of the obtained optical film and embossing, and 6) a winding step.

About the process of 1) (doping preparation process)

A cycloolefin-based polymer and a dye compound are dissolved or dispersed in a solvent to prepare a dope.

The solvent used for dope contains at least an organic solvent (good solvent) capable of dissolving a cycloolefin-based polymer. Examples of good solvents include chlorine-based organic solvents such as methylene chloride; Non-chlorine organic solvents, such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran, are contained. Among them, methylene chloride is preferred.

The solvent used for dope may further contain a poor solvent. Examples of poor solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope increases, the film-like substance is likely to gel, and peeling from the metal support is likely to be facilitated. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, ethanol is preferred from the viewpoint of stability of dope, a relatively low boiling point, and good drying properties.

About the process of 2) (flexible process)

The obtained dope is flexible on a support. The casting of dope can be performed by discharging it from the casting die.

The solvent is evaporated until the dope cast on the support body can be peeled off by a peeling roll from the support body. As a method of evaporating the solvent, there are a method of blowing air through a cast dope, a method of conducting heat transfer with a liquid from the back surface of a support, and a method of conducting heat transfer from the front and back by radiant heat.

After that, the cast film obtained by evaporating the solvent is peeled off with a peeling roll.

The amount of residual solvent of the cast film on the support during peeling varies depending on drying conditions, the length of the support, and the like, but may be, for example, 50 to 120% by mass. When peeling off in a state where there is a large amount of residual solvent, the flexible film is too flexible and the planarity is easily damaged during peeling, and wrinkles or vertical stripes are likely to occur due to peeling tension, and thus the amount of residual solvent at the time of peeling is determined in consideration of these points. The amount of residual solvent is defined by the following formula.

Residual solvent amount (mass%) = (mass before heat treatment of flexible film-mass after heat treatment of flexible film)/(mass after heat treatment of flexible film) x 100

The heat treatment when measuring the amount of residual solvent is a heat treatment at 115°C for 1 hour.

About the process of 3) (stretching process)

The cast film obtained by peeling from the support is stretched.

Stretching may be performed in accordance with required optical properties, and stretching is preferably performed in one or more of the width direction (TD direction), the conveyance direction (MD direction), and the oblique direction. For example, when manufacturing an optical film functioning as a λ/4 retardation film, it is preferable to stretch in the oblique direction.

The draw ratio is also different depending on the optical properties required, for example, when used as a λ/4 retardation film, it is preferably 1.05 to 4.0 times, and more preferably 1.5 to 3.0 times.

The draw ratio (times) is defined as the size in the stretching direction of the film after stretching/the size in the stretching direction of the film before stretching. Moreover, when performing biaxial stretching, it is preferable to set it as the said stretching ratio for each of the TD direction and the MD direction.

The stretching temperature (drying temperature during stretching) is preferably (Tg+2) to (Tg+50)°C, and (Tg+5) to (Tg+5), when the glass transition temperature of the cycloolefin-based polymer is Tg as described above. It is more preferable that it is (Tg+30) degreeC. When the stretching temperature is (Tg+2)°C or higher, it is easy to properly volatilize the solvent, so it is easy to adjust the stretching tension to an appropriate range. When it is (Tg+50)°C or less, the stretching property is impaired because the solvent does not volatilize excessively. It's hard to be. As for the stretching temperature, as described above, (a) it is preferable to measure the ambient temperature such as the temperature inside the stretching machine.

The amount of residual solvent in the film-like material at the start of stretching is preferably about the same as the amount of residual solvent in the film-like product at the time of peeling, for example, it is preferably 20 to 30% by mass, and more preferably 25 to 30% by mass. Do.

The stretching of the film-like material in the TD direction (width direction) can be performed by, for example, fixing both ends of the film-like material with clips or pins, and widening the gap between the clips and the pins in the traveling direction (tenter method). The stretching of the film-like material in the MD direction can be performed by, for example, a method (roll method) by giving a circumferential speed difference to a plurality of rolls and using the roll circumferential speed difference between them. In particular, a tenter method in which both ends of the flexible film are gripped and stretched with a clip or the like is preferable because it improves the flatness and dimensional stability of the film. It is preferable to stretch (diagonal stretching) in a direction obliquely crossing the MD direction and the TD direction by stretching the cast film in both directions in the MD direction and the TD direction.

About the process of 4) (drying process)

The stretched flexible film is further dried to obtain an optical film.

Drying of the cast film can be performed, for example, while transporting the cast film with a plurality of transport rolls (eg, a plurality of transport rolls arranged in a zigzag shape as viewed from the side). The drying means is not particularly limited, and hot air, infrared rays, heating rolls or microwaves are used. Hot air drying is preferable in terms of its simplicity.

5) Process (Cutting/Embossing Process)

Both ends in the width direction of the obtained optical film are cut. The cutting of both ends of the optical film can be performed with a slitter.

Next, embossing (knurling processing) is performed on both ends of the optical film in the width direction. The embossing process can be performed by pressing the heated embossing roller on both ends of the optical film. Small irregularities are formed on the surface of the embossing roller, and irregularities are formed on both ends by pressing the embossing roller on both ends of the optical film. By such embossing, it is possible to suppress as much as possible the winding misalignment and blocking (sticking between films) in the next winding step.

About the process of 6) (winding process)

And the obtained optical film is wound up and a roll body is obtained.

That is, it is set as a roll body by winding up on a winding core, conveying an optical film. The winding method of the optical film may be a method using a generally used winder, and there are methods of controlling tension such as a constant torque method, a static tension method, a taper tension method, and a program tension control method with a constant internal stress.

It is preferable that the winding length of the optical film in the roll body is 1000 to 7200 m. It is preferable that the width of the optical film is 1000 to 3000 mm.

The manufacturing method of the optical film of the present invention may further include other steps other than the above 1) to 6). For example, when the optical film contains an easy-adhesion layer, you may further perform the process of 7) forming an easy-adhesion layer between the process of 3) or 4) and the process of 5). Alternatively, after manufacturing the roll body of the base film containing the cycloolefin-based polymer in the above 1) to 6), the base film is released again, and the step 7) may be performed.

About the process of 7) (the easy-to-adhesion layer formation process)

The easy-adhesion layer can be formed by, for example, applying a coating liquid for an easy-adhesion layer on a base film containing a cycloolefin-based polymer, followed by drying.

The coating liquid for an easy-to-adhesion layer may be a solution containing the above-described thermoplastic resin and a solvent. Examples of the solvent contained in the coating liquid include water, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME (propylene glycol monomethyl ether), ethylene glycol, acetone, and methyl. Ethyl ketone, diisobutyl ketone, diethyl ketone, cyclohexanone, cyclopentanone, toluene, xylene, benzene, methylene chloride, chloroform, carbon tetrachloride, hexane, cyclohexane, dimethylformamide, dimethylacetamide, N-methylpi Rolidone, diethyl ether, dioxane, tetrahydrofuran, cyclopentyl methyl ether, methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, and acetic acid are included. These may be used alone, or may be mixed and used.

The coating liquid for an easy-to-adhesion layer may be a commercially available solution or dispersion. You may have added a solvent to a commercially available solution or dispersion. Further, the solid content such as the above-described thermoplastic resin may be dissolved or dispersed in various solvents.

The total solid content concentration of the coating liquid for an easy-to-adhesion layer can be appropriately set depending on the type, solubility, viscosity, wettability, thickness after coating, and the like of the thermoplastic resin. In order to obtain an easy-to-adhesive layer having high surface uniformity, the total solid content concentration of the coating liquid for an easy-to-adhesive layer is 1 to 100 parts by mass, preferably 1 to 50 parts by mass, based on 100 parts by mass of the solvent.

The viscosity of the coating liquid for an easy-to-adhesive layer should be within the range that can be applied, and the viscosity measured at a shear rate of 1000 (1/s) at 23°C is preferably 1 to 50 mPa·s, more preferably 2 to 10 mPa·s. to be.

The application method of the coating liquid is not particularly limited, and, for example, a gravure die or coater can be used.

When the easy-adhesion layer is applied on the cast film, as a pretreatment for improving wettability, solvent modification, corona treatment, and plasma treatment on the surface of the substrate layer can be performed.

The base film on which the easy-adhesion layer was formed may be further stretched as necessary. Stretching can be performed in any one or more of a width direction, a conveyance direction, and an oblique direction. In addition, stretching may be performed before and after the formation of the easy-to-adhesion layer, respectively. The stretching temperature after forming the easy-to-adhesion layer is preferably (Tg+2) to (Tg+50)°C, more preferably (Tg+5) to (Tg+5) when, for example, the glass transition temperature of the flexible film is Tg. It can be made into (Tg+30) degreeC.

3. Polarizer

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

1A is a cross-sectional view showing a configuration of a polarizing plate 100. 1B is an exploded perspective view showing an arrangement relationship between a polarizer constituting the polarizing plate 100 and each film.

As shown in Fig. 1A, the polarizing plate 100 of the present invention includes a polarizer 101, an optical film 102 of the present invention disposed on one side thereof, a counter film 103 disposed on the other side, and It may have two adhesive layers 104 disposed between the polarizer 101 and the optical film 102 and between the polarizer 101 and the counter film 103.

3-1. About the polarizer 101

The polarizer 101 is an element that passes only light having a polarization surface in a predetermined direction, and is a polyvinyl alcohol-based stretched film doped with iodine or a dichroic dye.

The thickness of the polarizer 101 is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

3-2. About the optical film 102

The optical film 102 can function as a retardation film, for example, a λ/4 retardation film used for a circularly polarizing plate of an organic EL display device.

In the plane of the optical film 102, the angle of the in-plane slow axis of the optical film 102 with respect to one side of the outer shape of the rectangular film (for example, the side 102a) is preferably 30 to 60° , More preferably 45° (see Fig. 1B). In addition, the side 102a corresponds to the width direction of the long optical film 102. In addition, the angle formed by the in-plane slow axis of the optical film 102 and the absorption axis (or transmission axis) of the polarizer 101 is preferably 30 to 60°, and more preferably 45°.

The optical film 102 may further have another layer (for example, a hard coat layer, a low refractive index layer, or an antireflection layer) disposed on a surface opposite to the polarizer 101 depending on the application. Further, the optical film 102 may further have an easy-to-adhesion layer (not shown) disposed on the surface of the polarizer 101 side.

3-3. About the counter film 103

The counter film 103 may be an optical film of the present invention, or other optical films (ie, protective films). Examples of the protective film include commercially available cellulose ester films (e.g., Konica Minolta Tac KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC8UY, KC4UE, KC4UY, KC4UE, KC4UY, -HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, and above Konica Minolta Co., Ltd., Fuji-Tac T40UZ, Fuji-Tac T60UZ, Fuji-Tac T80UZ, Fuji-Tac TD80UL, Fuji-Tac TD60UL, Fuji-Tac TD60UL, Fuji-Tac Taek R02, Fuji Taek R06, Sang Fujifilm (manufactured by Fujifilm Co., Ltd.) are included.

The thickness of the counter film 103 may be, for example, 5 to 100 μm, preferably 40 to 80 μm.

3-4. About the adhesive layer 104

The adhesive layer 104 may be disposed between the polarizer 101 and the optical film 102, and between the polarizer 101 and the counter film 103, respectively.

The adhesive layer 104 may be a layer obtained from a water-based adhesive described later, or may be a cured layer of an ultraviolet curable adhesive.

The thickness of the adhesive layer 104 is not particularly limited, but may be, for example, 0.01 to 10 μm, preferably about 0.01 to 5 μm.

The polarizing plate 100 may have a long shape or a sheet shape obtained by cutting a long polarizing plate along the width direction.

3-5. Properties

(T1/T2)

When an aluminum reflector is laminated on the optical film of a polarizing plate with an adhesive layer interposed therebetween, the reflectance of light at a wavelength of 460 nm of the polarizing plate is T1 (%), and the reflectance of light at a wavelength of 650 nm is T2 (%), It is desirable to satisfy (5).

Equation (5): 0<T1/T2<2.6

If T1/T2 is less than 2.6, the reflectance of light having a wavelength of 460 nm is not too high, that is, leakage of reflected light in the vicinity of the wavelength can be suppressed, so that, for example, the color sense of reflected light in an organic EL display device can be improved. . In addition, when T1/T2 exceeds 0, for example, since light emission in the wavelength region in the organic EL display device is hardly inhibited by the dye compound, a decrease in luminance can be suppressed. It is more preferable that T1/T2 is 2.5 or less.

(Color difference ΔE(a ^* b ^* ))

In addition, the color difference ΔE (a ^* b ^* ) of the polarizing plate is preferably less than 25, and more preferably less than 20. When the color difference ΔE (a ^* b ^* ) of the polarizing plate is within the above range, for example, the color sense of reflected light in an organic EL display device can be improved.

The T1/T2 and the color difference ΔE (a ^* b ^* ) of the polarizing plate can be measured in the following order.

1) On the optical film of the polarizing plate, an aluminum reflector is laminated through an adhesive layer to obtain a polarizing plate sample. As the pressure-sensitive adhesive, use an acrylic pressure-sensitive adhesive.

2) The spectral reflectance and color difference ΔE (a ^* b ^* ) of the obtained polarizing plate sample were measured by the SCI method with a spectrophotometer (CM3700d manufactured by Konica Minolta).

The T1/T2 and color difference ΔE (a ^* b ^* ) of the polarizing plate can be adjusted by the type and content of the dye compound represented by the formula (1).

3-6. Method of manufacturing the polarizing plate 100

The polarizing plate 100 can be obtained through a step of bonding the polarizer 101 and the optical film 102 of the present invention through an adhesive. As the adhesive, a water-based adhesive or an ultraviolet curable adhesive is used.

(Water-based adhesive)

Examples of the water-based adhesive include a water adhesive (such as a completely saponified polyvinyl alcohol aqueous solution) containing a polyvinyl alcohol-based resin.

(UV curable adhesive)

The ultraviolet curable adhesive composition may be a photo radical polymerization type composition, a photo cationic polymerization type composition, or a hybrid type composition using them in combination.

Examples of the photo-radical polymerizable composition include a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxyl group described in Japanese Patent Laid-Open No. 2008-009329, and a composition containing a radical polymerizable compound not containing a polar group. do.

It is preferable that the radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization. Preferred examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth)acryloyl group. Examples of the compound having a (meth)acryloyl group include N-substituted (meth)acrylamide-based compounds and (meth)acrylate-based compounds. (Meth)acrylamide means acrylamide or methacrylamide.

Examples of the photo cationic polymerization type composition include (α) cationic polymerizable compounds, (β) photocationic polymerization initiators, and (γ) light having a wavelength longer than 380 nm as disclosed in Japanese Patent Laid-Open No. 2011-028234. An ultraviolet-curable adhesive composition comprising a photosensitizer exhibiting maximum absorption and a (δ) naphthalene-based photosensitizing aid.

Hereinafter, an example in which an ultraviolet curable adhesive is used will be described. In the polarizing plate 100 of the present invention, 1) a process of performing pretreatment for easy adhesion to the adhesive surface of an optical film and a counter film (pre-treatment process), 2) bonding a polarizer and an optical film (or counter film) through an ultraviolet adhesive And 3) irradiating ultraviolet rays to the laminate obtained by bonding to cure the ultraviolet adhesive (curing step).

(1) pretreatment process

A bonding facilitation treatment is performed on the bonding surface of the optical film and the counter film to the polarizer. Examples of adhesion facilitation treatment include corona treatment and plasma treatment.

(2) bonding process

An ultraviolet curable adhesive is applied to at least one of a polarizer and an optical film (or a counter film). The method of applying the ultraviolet curable adhesive is not particularly limited, and may be, for example, a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, or the like.

And the polarizer and the optical film or the counter film are bonded through an ultraviolet curable adhesive. Then, both sides of the laminated product are pressed by pressing them with a pressing roller or the like. Metal or rubber may be used as the material of the pressure roller.

(3) curing process

Next, the UV-curable adhesive is cured by irradiating ultraviolet rays to the laminated product bonded through the UV-curable adhesive. Thereby, a polarizer and an optical film or a counter film are bonded through an ultraviolet curable adhesive. In addition, curing of the ultraviolet-curable adhesive on one side of the polarizer and the ultraviolet-curable adhesive on the other side of the polarizer may be performed sequentially or at the same time. From the viewpoint of enhancing the manufacturing efficiency of the polarizing plate, it is preferable to simultaneously cure the ultraviolet-curable adhesive on one side of the polarizer and the ultraviolet-curable adhesive on the other side of the polarizer.

The irradiation conditions of ultraviolet light may be conditions under which the ultraviolet curable adhesive is cured, for example, the accumulated light amount is preferably 50 to 1500 mJ/cm 2, more preferably 100 to 500 mJ/cm 2.

The line speed at the time of manufacturing the polarizing plate varies depending on the curing time of the adhesive, but is preferably 1 to 500 m/min, and more preferably 5 to 300 m/min, for example. When the line speed is 1 m/min or more, it is easy to increase the productivity and the damage to the optical film or the counter film can be reduced. Further, when the line speed is 500 m/min or less, curing of the ultraviolet curable adhesive becomes sufficient and good adhesion is easy to be obtained.

In this way, in the curing process, there is a case where a high-temperature environment is obtained by irradiation with ultraviolet rays or heating for accelerating curing. In addition, even when the adhesive is a water-based adhesive, there is a case where it becomes a high temperature environment due to adhesion promotion or heating for drying the adhesive.

On the other hand, since the increase in the coefficient of thermal expansion of the optical film of the present invention is suppressed, curling of the polarizing plate can be suppressed because the optical film of the present invention has little thermal expansion even in an environment where the temperature becomes high when the polarizer and the optical film are bonded. . By suppressing curl of the polarizing plate, in the organic EL display device having the polarizing plate, slight light leakage due to reflection of external light during black display can be suppressed.

4. Image display device

The optical film of the present invention can be used as an optical film (phase difference film, protective film) of an image display device such as an organic EL display device or a liquid crystal display device. Among them, the optical film of the present invention can be preferably used as a retardation film (λ/4 retardation film) of an organic EL display device.

(Organic EL display device)

2 is an exploded cross-sectional view of the organic EL display device 200.

The organic EL display device 200 has an organic EL element 300 (display cell), a polarizing plate 100 (circular polarizing plate), and an adhesive layer 400 disposed therebetween.

The organic EL device 300 has a metal electrode 302, a light emitting layer 303, a transparent electrode (ITO, etc.) 304 and a sealing layer 305 in this order on a substrate 301 such as glass or polyimide. . The metal electrode 302 may be composed of a reflective electrode and a transparent electrode.

The metal electrode 302 can function as a cathode. For the metal electrode 302, it is preferable to use a material having a small work function in order to facilitate electron injection to increase luminous efficiency, and usually Mg-Ag or Al-Li is used.

The light-emitting layer 303 is a stack of organic thin films, and includes, for example, a stack of a hole injection layer containing a triphenylamine derivative, and a light-emitting layer containing a fluorescent organic solid such as anthracene, or such a light-emitting layer and a perylene derivative. It may be a stack of electron injection layers, these hole injection layers, light emitting layers, stacks of electron injection layers, and the like.

The transparent electrode 304 can function as an anode. The transparent electrode 304 may be generally made of a transparent conductor such as indium tin oxide (ITO).

In addition, by applying a voltage between the metal electrode 302 and the transparent electrode 304, holes and electrons are injected into the light emitting layer 303, and the energy generated by the recombination of the holes and electrons excites the fluorescent material and is excited. When the fluorescent substance returns to its ground state, it emits light and emits light.

The polarizing plate 100 is disposed on the surface of the organic EL element 300 on the visible side. The polarizing plate 100 is the polarizing plate 100 described above (see FIG. 1A), and the optical film 102 (λ/4 retardation film) is disposed between the organic EL element 300 and the polarizer 101. The angle formed by the transmission axis (or absorption axis) of the polarizer 101 and the in-plane slow axis of the optical film 102 is bonded to be preferably 45° (or 135°) as described above.

It is preferable that the counter film 103 further has a cured layer (not shown) disposed on a surface on the viewing side thereof (a surface opposite to the polarizer 101). The cured layer not only prevents scratches on the surface of the organic EL display device, but also reduces warpage of the polarizing plate 100. Further, an antireflection layer may be further formed on the cured layer.

The adhesive layer 400 is disposed between the organic EL element 300 and the polarizing plate 100, and bonds them. Examples of adhesives constituting the adhesive layer 400 include thermosetting adhesives (epoxy thermosetting adhesives, urethane thermosetting adhesives, acrylic thermosetting adhesives, etc.), hot melt adhesives (rubber hot melt adhesives, polyester hot melt adhesives, etc.) , Polyolefin-based hot melt adhesives, ethylene-vinyl acetate resin-based hot melt adhesives, polyurethane resin hot melt adhesives, etc.) are included.

(Action)

In such an organic EL display device 200, when a voltage is applied to the metal electrode 302 and the transparent electrode 304, electrons are injected from the metal electrode 302 serving as a cathode to the light emitting layer 303 and become an anode. Holes are injected from the transparent electrode 304 and both recombine in the light-emitting layer 303, thereby generating visible light emission corresponding to the light-emitting characteristics of the light-emitting layer 303. The light generated from the light-emitting layer 303 is directly or reflected by the metal electrode 302 and then extracted to the outside through the transparent electrode 304 and the polarizing plate 100.

The light emitting layer 303 is formed of a very thin film having a thickness of about 10 nm. For this reason, the light emitting layer 303 also transmits light almost completely like the transparent electrode 304. As a result, light incident from the outside of the organic EL display device 200 during non-emission, passing through the sealing layer 305, the transparent electrode 304, and the light emitting layer 303 to reach the metal electrode 302 is metal It is reflected from the electrode 302, passes through the light emitting layer 303, the transparent electrode 302, and the sealing layer 305 again, and attempts to come out to the surface side of the organic EL device 200. In this case, the optical film 102 suppresses leakage of light reflected from the metal electrode 302 to the surface side of the organic EL display device 200, and thus external light reflection can be reduced.

That is, of the external light incident from the outside of the organic EL display device 200 by indoor lighting or the like during non-emission, half is absorbed by the polarizer 101 of the polarizing plate 100, but the remaining half is not absorbed and is used as linearly polarized light. It transmits and enters the optical film 102 (λ/4 retardation film). The light incident on the optical film 102 is converted into circularly polarized light because the transmission axis of the polarizer 101 and the in-plane slow axis of the optical film 102 cross 45° (or 135°). do.

When the circularly polarized light emitted from the optical film 102 is mirror-reflected by the metal electrode 302 of the organic EL element 300, the phase is inverted by 180 degrees to become circularly polarized light of reverse rotation. When this reflected light enters the optical film 102, it is converted into linearly polarized light that is perpendicular to the transmission axis of the polarizer 101 (parallel to the absorption axis), so that it can be suppressed from being absorbed by the polarizer 101 and being emitted to the outside. .

And in the present invention, the optical film 102 containing a specific dye compound is used. Thereby, the optical film 102 is perpendicular to the transmission axis of the polarizer 101 (absorption) even for light in a specific wavelength region (in a cycloolefin resin film not containing a coloring compound, which cannot be converted to a desired linear polarization). It can be converted to linearly polarized light (parallel to the axis). Thereby, it is possible to suppress a decrease in the color sense of the reflected light caused by leakage of the reflected light in a specific wavelength region through the transmission axis of the polarizer 101. In addition, even if the optical film 102 contains a dye compound, an increase in the coefficient of thermal expansion is suppressed. Therefore, even when the polarizing plate 101 is exposed to high temperature and high humidity, curling is difficult to occur, and the resulting display unevenness can also be suppressed.

<Example>

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

1. The material of the film

(1) Cycloolefin-based polymer

<Synthesis of Cycloolefin Polymer 1>

100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylic acid methyl ester (refer to the following formula) were put into a reaction pot. Next, 25 mmol% of ethylhexanoate-Ni dissolved in toluene (large monomer mass), 0.225 mol% of tri(pentafluorophenyl) boron (large monomer mass), and 0.25 mol% of triethylaluminum dissolved in toluene (large Monomer mass) was put into a reaction pot, and reacted for 18 hours while stirring at room temperature. After completion of the reaction, the reaction mixture was added to excess ethanol to generate a polymer precipitate. The precipitate was purified, and the obtained solid was dried at 65°C for 24 hours by vacuum drying to obtain a cycloolefin polymer (P-1) (weight average molecular weight Mw: 140,000, Tg: 140°C). In addition, the weight average molecular weight was measured by the method mentioned above.

(2) dye compound

<Color compound 1>

Yamada Chemical Co., Ltd. FDB-023 was used as the dye compound 1.

<Color compound 2>

(Synthesis of IM2)

In the synthesis of 2-dimethylamino-4-hydroxy-6-methylpyrimidine described in [Journal of American Chemical Society 1954, 76, 1879] in a 1L four-necked eggplant flask equipped with a cooling tube and a thermometer, Compound IM1 was obtained in the same manner except that N,N-dimethylguanidine sulfate was replaced with 1,1-dibutylguanidine hydrochloride. Using compound IM1, it was formylated by a Reimer-Tiemann reaction in the same procedure as described in Journal of the Chemical Society 1957, 4845, and compound IM2 (10.4 g, yield 61%) was obtained. Got it.

(Synthesis of IM3)

Compound IM2 (4.8 g), 1,5-dibromopentane (2.1 g), potassium carbonate (3.0 g), and DMF (30 mL) were added into a 50 mL four-necked eggplant flask equipped with a cooling tube and a thermometer, The mixture was stirred at 60° C. for 120 minutes. It discharged to water (60 mL), and the precipitated crystal|crystallization was taken out by filtration, and it washed with water. The obtained crude crystal was washed with methanol to obtain compound IM3 (3.6 g, yield 75%).

(Synthesis of pigment compound 2)

Compound IM3 (2.5 g), propionnitrile (0.6 g), piperidine (0.1 g), ethanol (20 mL), and DMF (6 mL) were added into a 50 mL four-necked eggplant flask equipped with a cooling tube and a thermometer. It was stirred at °C for 5 hours. The reaction solution was allowed to stand to cool to room temperature, and then precipitated crystals were filtered out and taken out. This crystal was washed with methanol to obtain a dye compound 2 (2.4 g, yield 81%).

<Color compound 3>

The compound IM3 (2.1g), methyl cyanoacetate (1.5g), piperidine (0.03g), and ethanol (15mL) were mixed in a 50 mL four-necked eggplant flask equipped with a cooling tube and a thermometer, and 75°C The mixture was stirred for 18 hours. After standing to cool to room temperature, the precipitated crystals were collected by filtration, and washed with ethanol to obtain a dye compound 3 (3.6 g, yield 89%).

<Color compound 4>

FDB-003 manufactured by Yamada Chemical Co., Ltd. was used as the dye compound 4.

<Color compound 5>

FDB-004 manufactured by Yamada Chemical Co., Ltd. was used as the dye compound 5.

<Color compound 6>

SOM-5-0103 (cinnamic acid) manufactured by Orient Chemical Co., Ltd. was used as the dye compound 6.

<Color compound 7>

FDB-001 (porphyrin) manufactured by Yamada Chemical Co., Ltd. was used as the dye compound 7.

<Color compound 8>

The dye compound 8 was obtained by the method described in Japanese Patent Application Laid-Open No. 2011-184414.

<Color compound 9>

Dye compound 9 was obtained in the same manner as in the dye compound 8, except that the amino group was changed to a phenyl group.

<Color compounds 10 to 12>

In the synthesis of the dye compound 2, the number of carbon atoms and the degree of unsaturation of the alkyl chain of propionnitrile reacted with the compound IM3 are adjusted (for example, in the case of m=2, (CH ₃ )CN-C=CH-CH ₂ using -CH ₃ to) m was changed to other than the value indicated in the following table to obtain a dye compound 10-12 as a dye compound 2 with the same method.

Dye compounds 1 to 6 and 8 to 12 are shown below.

(* indicates bonding position)

In addition, the maximum absorption wavelength was measured by the following method.

(Measurement of maximum absorption wavelength)

The maximum absorption wavelength of the compound was determined by measuring the absorption spectrum of the dye compound in dichloromethane using an ultraviolet-visible spectrophotometer UV-2450 manufactured by Shimadzu Corporation. In addition, all of the dye compounds 1 to 5, 8 and 9 were in the range of 370 to 460 nm.

2. Preparation and evaluation of optical films

<Production of Optical Film 101>

(Preparation of an additive liquid for fine particles)

After stirring and mixing the following components for 50 minutes with a dissolver, dispersion was performed with Manton Gaulin. Further, dispersion was performed with an attritor so that the particle diameter of the secondary particles became a predetermined size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid.

Fine particles (Aerosil R812: manufactured by Nippon Aerosil, primary average particle diameter: 7 nm, apparent specific gravity 50 g/L): 4 parts by mass

Dichloromethane: 48 parts by mass

Ethanol: 48 parts by mass

(Preparation of dope)

After the following ingredients were introduced into a sealed container while sufficiently stirring, the temperature was raised to 80° C. and maintained for 1 hour. Next, after cooling this to 30 degreeC, it filtered with a filter of 5 micrometers pore diameter, and obtained dope A-1.

Cycloolefin polymer (P-1): 100 parts by mass

Dichloromethane: 302 parts by mass

Ethanol: 18 parts by mass

Dye compound 1: 0.1 parts by mass

Particle addition liquid: 10 parts by mass

(Production of optical film)

On an endless metal support driven at a speed of 30 m/min, the prepared dope is cast from a casting die, and a dry air at 40°C is blown on the support to obtain a flexible film (membrane) having self-supporting properties. Dry until quality. Then, it cooled to 10 degreeC, and the cast film was peeled from a support body. Thereafter, the peeled cast film was dried at 110° C. for 30 minutes, and then stretched at 170° C. in a direction of 45° with respect to the width direction (oblique direction) at twice the draw ratio. Thereby, an optical film 101 having a thickness of 40 µm and having an in-plane slow axis in a direction of about 45° with respect to the width direction was obtained.

<Production of optical films 102 to 109>

Except having changed the dye compound 1 to the dye compound shown in Table 1, it carried out similarly to the optical film 101, and obtained the optical films 102-109.

<Production of optical films 110 to 114>

Except having changed the content of the dye compound 4 as shown in Table 1, it carried out similarly to the optical film 104, and obtained the optical films 110-114.

<Production of optical film 115>

Except having changed the content of the dye compound 1 as shown in Table 1, it carried out similarly to the optical film 101, and obtained the optical film 115.

<Production of optical films 116 to 118>

Except having changed m of dye compound 2 as shown in Table 1, it carried out similarly to optical film 102, and obtained optical films 116-118.

<Evaluation>

The thermal expansion coefficient and retardation of the obtained optical films 101 to 118 were measured by the following method.

(Coefficient of thermal expansion)

The prepared optical film was cut into a size of 10 mm (length) x 1 mm (width) to obtain a sample film. The obtained sample film was heated and lowered in a temperature range of 30 to 140°C using a TMA (thermo-mechanical analysis) tester (TMA7100 manufactured by Hitachi High-Tech Science) under an environment of 23°C, and the amount of dimensional change in the temperature range of 50 to 120°C Δl was measured. And the obtained dimensional change amount Δl was applied to the following formula to calculate the coefficient of thermal expansion α (ppm/°C).

(l: length of the sample film (length in the vertical direction; 10 mm)

Δt: change in temperature (70℃)

Δl: dimensional change value of the sample film)

(Phase difference)

The retardation (Ro) of the optical film was measured by the following method.

1) The optical film is humidified in an environment of 23°C and 55% RH for 24 hours. The average refractive index of this film was measured with an Abbe refractometer, and the thickness d was measured using a commercially available micrometer.

2) Measurement of the film after humidity control The retardation Ro and Rt at a wavelength of 550 nm were measured in an environment of 23°C and 55% RH using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter), respectively. I did.

Table 1 shows the evaluation results of the optical films 101 to 118.

As shown in Table 1, the optical films 101 to 105 and 111 to 117 (the present invention) have a thermal expansion coefficient of 100 ppm/°C or less, which is lower than that of the optical films 106 to 109 (Comparative Example). In addition, the retardation Ro of the optical films 101-105 and 111-117 (the present invention) were all 140 nm.

3. Fabrication and evaluation of polarizing plate

<Manufacture of polarizing plate 201>

(1) Fabrication of polarizer

A long polyvinyl alcohol film having a thickness of 60 µm was continuously conveyed through a guide roll, immersed in a dyeing bath (30°C) of iodine and potassium iodide, followed by dyeing treatment and 2.5 times stretching treatment, and then boric acid and potassium iodide. In an acidic bath (60° C.) to which is added, stretching treatment and crosslinking treatment are performed, and the resulting iodine-PVA polarizer having a thickness of 12 μm is dried in a dryer at 50° C. for 30 minutes, and a polarizer having a moisture content of 4.9% Got it.

(2) Preparation of UV-curable adhesive

Each of the following components was mixed to obtain a liquid ultraviolet curable adhesive (UV adhesive).

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate: 40 parts by mass

Bisphenol A type epoxy resin: 60 parts by mass

Diphenyl[4-(phenylthio)phenyl]sulfoniumhexafluoroantimonate (cationic polymerization initiator): 4.0 parts by mass

(3) Fabrication of polarizing plate

After corona treatment was performed on the bonding surface of the optical film 101, the prepared ultraviolet curable adhesive was applied to a dry thickness of 3 μm by a coating apparatus equipped with a chamber doctor. In addition, after corona treatment was similarly applied to the bonding surface of Konica Minolta Tack KC4CT (thickness 40 μm, manufactured by Konica Minolta) as a counter film, the UV-curable adhesive was applied to a dry thickness of 3 μm.

Immediately after that, the optical film 101 was attached to one side of the prepared polarizer, and the TAC film, which was a counter film, was bonded to the other side by a roll-to-roll method via an ultraviolet curable adhesive. The bonding was performed so that the width direction of the optical film 101 and the absorption axis (or transmission axis) of the polarizer coincide (the angle formed by the in-plane slow axis of the optical film 101 and the absorption axis of the polarizer was 45°). Thereafter, while conveying the bonded product at a line speed of 20 m/min, ultraviolet rays were irradiated from the optical film 101 side with a metal halide lamp so that the accumulated amount of light at a wavelength of 280 to 320 nm was 320 mJ/cm 2. Thereby, the ultraviolet curable adhesive was hardened and the polarizing plate 201 was obtained. Further, since the polarizing plate 201 is produced by a roll-to-roll method, finally, a long polarizing plate was cut along the width direction to obtain a sheet-shaped polarizing plate 201.

<Production of polarizing plates 202-218>

Except having changed the optical film 101 to what appears in Table 2, it carried out similarly to the polarizing plate 201, and obtained the polarizing plates 202-218.

<Evaluation>

The curl of the obtained polarizing plates 201 to 218, the ratio of the color sense and reflectance of the reflected light (T1/T2) were evaluated by the following method.

(curl)

The obtained polarizing plate was cut out into a width direction of 35 mm and a conveyance direction of 1 mm to obtain a sample. The obtained sample was allowed to stand for 30 minutes in an 80°C atmosphere, and then the degree of curl was measured. The curling degree is expressed as the reciprocal of the radius of curvature, and specifically, it was measured according to the method A of ISO18910:2000. And the polarizing plate curl was evaluated based on the following criteria.

◎: The degree of curl (the reciprocal of the radius of curvature) is less than ^{30m -1}

○: The degree of curl (the reciprocal of the radius of curvature) is 30m ^-1 or more and less ^{than 40m -1}

△: The degree of curl (the reciprocal of the radius of curvature) is 40m ^-1 or more and 50m ^{-1 or} less

×: The degree of curl (the reciprocal of the radius of curvature) is 50 m ^-1 or more

If it was △ or more, it was judged as good.

(Reflected light color)

A reflective material was prepared by bonding a commercially available aluminum foil (manufactured by Nakamura, 13 µm thick aluminum foil) to a commercially available acrylic plate (CLAREX manufactured by Nitto Jushi Kogyo) through an adhesive sheet (LUCIACS manufactured by Nitto Denko, acrylic adhesive). Next, the obtained reflective material was bonded to the optical film of the above-produced polarizing plate through an adhesive sheet to obtain a polarizing plate sample.

The color difference ΔE (a ^* b ^* ) of the obtained polarizing plate sample was measured by the SCI method using a spectrophotometer (CM3700d manufactured by Konica Minolta). And the color of the reflected light was evaluated based on the following criteria.

◎: ΔE(a ^* b ^* ) is 0 or more and less than 15

○: ΔE (a ^* b ^* ) is 15 or more and less than 20

△: ΔE (a ^* b ^* ) is 20 or more and less than 25

×: ΔE(a ^* b ^* ) is 25 or more

If it was △ or more, it was judged as good.

(Reflectance ratio (T1/T2))

The spectral reflectance of the polarizing plate sample was measured by the SCI method with a spectrophotometer (CM3700d, manufactured by Konica Minolta). Then, the reflectance of light having a wavelength of 460 nm was T1 (%), and the reflectance of light having a wavelength of 650 nm was T2 (%), and the ratio T1/T2 of the reflectance was calculated.

If T1/T2 exceeds 0 and is 2.5 or less, it was considered favorable.

Table 2 shows the evaluation results of the polarizing plates 201 to 218.

As shown in Table 2, the polarizing plates 201 to 205 and 210 to 217 (the present invention) were found to have reduced curls. This is considered to be because the thermal expansion coefficient of the optical film containing the dye compound represented by general formula (1) is low. Moreover, the reflection color sense of the polarizing plates 201 to 205 and 210 to 217 (the present invention) was also good, and T1/T2 was also in an appropriate range.

In contrast, it can be seen that curling occurs in all of the polarizing plates 206 to 209 (Comparative Example). It is thought that this is because the thermal expansion coefficient of an optical film is large. In addition, it was found that the luminance of the reflected light was lowered in the polarizing plate 218 (Comparative Example).

This application claims priority based on Japanese Patent Application No. 2019-162237 filed on September 5, 2019. All of the contents described in the application specification and drawings are incorporated herein by reference.

According to the present invention, it is possible to provide an optical film, a polarizing plate, and an organic EL display device capable of suppressing a decrease in color sensation of reflected light of an organic EL display device without increasing a coefficient of thermal expansion.

100: polarizer
101: polarizer
102: optical film
103: counter film
104: adhesive layer
200: organic EL display device
300: organic EL element
301: substrate
302: metal electrode
303: light-emitting layer
304: transparent electrode
305: sealing layer
400: adhesive layer

Claims (8)

A cycloolefin-based polymer having a structural unit derived from a norbornene-based monomer having an ester-containing group, and
Dye compound represented by the following formula (1)
It is an optical film containing,
An optical film having a thermal expansion coefficient of 100 ppm/°C or less, measured in a range of 50 to 120°C in a direction of 45° with respect to the in-plane slow axis of the optical film.

(In formula (1),
Each R ₁ is a cyano group or an alkyl group,
Each R ₂ is a hydrogen atom or a substituent,
m is a natural number from 1 to 5,
Y is an electron withdrawing group,
Z is a group represented by any of the following formulas (2) to (4))

(In formulas (2) to (4),
R ₃ to R ₅ are each a hydrogen atom or a substituted or unsubstituted alkyl group,
R ₆ to R ₈ are each a substituted or unsubstituted alkyl group, or an organic group including N, O, S or two or more of them,
n is each an integer of 0 to 4,
p is an integer from 0 to 5,
q is an integer from 0 to 3) The method of claim 1,
An optical film wherein the electron withdrawing group is a cyano group or an alkoxycarbonyl group. The method of claim 2,
The electron withdrawing group is a cyano group. The method according to any one of claims 1 to 3,
R ₁ is a cyano group. The method according to any one of claims 1 to 4,
m is an optical film of 1. The method according to any one of claims 1 to 5,
The content of the dye compound is 0.01 to 3% by mass based on the cycloolefin-based polymer. With polarizer,
The optical film according to any one of claims 1 to 6 disposed on at least one side thereof
It is a polarizing plate having,
When the reflectance of light having a wavelength of 460 nm of the polarizing plate is T1 and the reflectance of light having a wavelength of 650 nm is T2 when the aluminum reflector is fixed on the optical film, a polarizing plate that satisfies the following formula (5).
Equation (5): 0<T1/T2<2.6 An organic EL device,
Polarizing plate according to claim 7
Have,
The optical film is an organic EL display device disposed between the organic EL element and the polarizer.

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