WO2022168834A1

WO2022168834A1 - Optical film, polarization plate, and display device

Info

Publication number: WO2022168834A1
Application number: PCT/JP2022/003853
Authority: WO
Inventors: 翠木暮; 晋平畠山
Original assignee: コニカミノルタ株式会社
Priority date: 2021-02-08
Filing date: 2022-02-01
Publication date: 2022-08-11
Also published as: TW202237383A; JPWO2022168834A1; CN116848442A; TWI831126B

Abstract

This belt-like optical film includes, in a film surface, an obliquely stretched film that has a slow axis inclined with respect to the width direction of the optical film, and an easily adhesive layer that is disposed on a surface of the obliquely stretched film. When the middle points in the width direction of the obliquely stretched film at 0m position, 10m position, and 20m position in a direction orthogonal to the width direction of the film are defined as m0, m1, and m2, a saber form which is represented by a distance of the m1 to the center line connecting the m0 and the m2 in the width direction of the film is not less than 10 mm and the indentation elastic modulus of the easily adhesive layer is 1.5-3.0 GPa.

Description

Optical films, polarizing plates and display devices

The present invention relates to optical films, polarizing plates and display devices.

Polarizing plates are usually used in displays such as organic EL displays (OLED) and liquid crystal displays (LCD). A polarizing plate includes a polarizer and an optical film having a function to protect it and an optical compensation function.

A polarizing plate is produced by bonding a polarizer and an optical film together. In that case, an optical film having an easy-adhesion layer is sometimes used in order to facilitate adhesion to the polarizer.

As an optical film containing an easy-adhesion layer, for example, an easy-adhesion film containing a transparent film substrate and an easy-adhesion layer is known (for example, Patent Document 1). The transparent film substrate is an acrylic resin film stretched in the horizontal and vertical directions, and the easy-adhesion layer contains urethane resin as a binder resin and fine particles.

Thus, many of the optical films containing the easy-adhesion layer contain film substrates that are either stretched in the horizontal direction or the vertical direction, or are not stretched. The saber-form, which is used as an index of distortion of such a film substrate, is usually set to be less than 10 mm.

Japanese Patent Application Laid-Open No. 2020-23170

By the way, in recent years, the image quality of displays has improved, and the development of high-definition display devices such as 4K and 8K is underway. Optical films used in polarizing plates of high-definition display devices are required to have a higher surface quality than ever before, so fine scratches and the like, which have not been regarded as a problem in the past, are likely to become defects.

In particular, the polarizing plate is produced by unrolling a strip-shaped polarizing plate wound into a roll and cutting it to a predetermined length. Therefore, it is required to prevent the formation of fine scratches on the surface of the optical film as much as possible when the strip-shaped polarizing plate is wound into a roll.

Loosely winding the film is effective in suppressing scratches when the film is wound into a roll. It is effective to However, there is a problem that when such a saber foam is wound in a state where an easy-adhesion layer is laminated on a large film substrate, white traces (white traces) tend to remain. Such white marks are likely to occur remarkably particularly when an obliquely stretched film is used as the film substrate, because the saber form tends to be larger than that of a longitudinally stretched or transversely stretched film. In addition, a polarizing plate having such white marks tends to deteriorate the display characteristics of the 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 a display device that can suppress fine scratches due to winding and make it difficult for white marks to occur.

The optical film of the present invention is a strip-shaped film comprising an obliquely stretched film having a slow axis tilted with respect to the width direction of the film in the plane of the film, and an easy-adhesion layer disposed on the surface of the obliquely stretched film. In the optical film, when the midpoints in the width direction of the film are respectively m0, m1, and m2 at the 0 m position, 10 m position, and 20 m position in the direction perpendicular to the width direction of the obliquely stretched film, m0 and the above The saber form represented by the distance of m1 in the width direction of the film from the center line connecting m2 is 10 mm or more, and the indentation elastic modulus of the easily adhesive layer is 1.5 to 3.0 GPa.

The polarizing plate of the present invention includes a polarizer, the optical film of the present invention arranged on at least one surface of the polarizer, and an adhesive layer arranged between the polarizer and the easily adhesive layer.

The display device of the present invention includes a display element and the polarizing plate of the present invention, and the optical film is arranged between the display element and the polarizer.

According to the present invention, it is possible to provide an optical film, a polarizing plate, and a display device that can prevent fine scratches and make it difficult for white traces to occur due to winding.

FIG. 1 is a schematic cross-sectional view showing the configuration of an optical film according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a method for measuring saber form. FIG. 3 is a schematic diagram showing the configuration of an obliquely stretched film manufacturing apparatus. FIG. 4 is a schematic diagram showing the configuration of the extending portion of FIG. FIG. 5A is a cross-sectional view showing the configuration of a polarizing plate according to one embodiment of the present invention, and FIG. 5B is an exploded view showing the arrangement relationship of a polarizer, a retardation film, and a protective film that constitute the polarizing plate of FIG. 5A. It is a perspective view. FIG. 6 is a schematic cross-sectional view showing the configuration of an organic EL display device according to one embodiment of the present invention.

Although the cause of the occurrence of white marks (white mark defects) when an optical film using an obliquely stretched film with saber form above a certain level is wound up in a roll and stored, is not clear, it is speculated as follows. be.

A film with a large saber form tends to have uneven winding hardness in the width direction of the film. That is, in the width direction of the film, there are likely to be areas where the winding hardness is relatively high and areas where the winding hardness is relatively low. The portion with low winding hardness tends to sag the film, and tends to cause local torsional deformation during winding (or unwinding). Since the torsionally deformed portion is convex, it easily comes into contact with the adjacent easy-adhesion layer. Since the easy-adhesion layer is relatively soft, twist deformation is likely to be transferred, and it is considered that white marks are formed.

On the other hand, the present inventors have found that by setting the indentation modulus of the easy-adhesion layer to a certain value or higher (moderately high), it is possible to suppress the white marks that tend to occur when a diagonally stretched film having a large saber form is used. I found

That is, by setting the indentation elastic modulus of the easy-adhesion layer to 1.5 GPa or more, white marks can be suppressed. Further, by setting the indentation elastic modulus of the easy-adhesion layer to 3.0 GPa or less, the adhesion to the polarizer can be less likely to be impaired.

The indentation modulus of the easy-adhesion layer can be adjusted, for example, by the composition of the easy-adhesion layer and the degree of cross-linking. For example, by using polyolefin or a cross-linked product thereof as the easy-adhesion layer, the indentation modulus of the easy-adhesion layer can be increased. The configuration of the present invention will be described in detail below.

1. 1. Optical Film FIG. 1 is a schematic cross-sectional view showing the configuration of an optical film 10 according to one embodiment of the present invention. As shown in FIG. 1, the optical film 10 includes an obliquely stretched film 11 and an easily adhesive layer 12 disposed on its surface.

1-1. Obliquely stretched film 11
The obliquely stretched film contains a thermoplastic resin. Although the thermoplastic resin is not particularly limited, it is preferably a resin transparent to a desired wavelength from the viewpoint of use in optical applications. Examples of such resins include polycarbonates (PC), polyesters, cycloolefinic resins (COP), polyethersulfones, polyimides, (meth)acrylic resins, polysulfones, polyarylates, polyolefins, polyvinyl chloride, fumaric acid Diester resins are included. Among them, cycloolefin resin (COP), diester fumarate resin, and polyester are preferred.

<Cycloolefin resin (COP)>
The cycloolefin-based resin may be a homopolymer or copolymer containing structural units derived from cycloolefin (cyclic olefin).

The cycloolefin may be either a polycyclic cycloolefin or a monocyclic cycloolefin, preferably a polycyclic cycloolefin. Examples of polycyclic cycloolefins include norbornene, methylnorbornene, dimethylnorbornene, ethylnorbornene, ethylidenenorbornene, butylnorbornene (norbornene monomers), dicyclopentadiene, dihydrodicyclopentadiene, methyldicyclopentadiene. , dimethyldicyclopentadiene, tetracyclododecene, methyltetracyclododecene, dimethylcyclotetradodecene, tricyclopentadiene, tetracyclopentadiene. Among them, norbornene-based monomers are preferred.

That is, the cycloolefin-based resin is a polymer containing structural units derived from norbornene-based monomers. A norbornene-based monomer is represented by the following formula (1).

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

Examples of halogen atoms include fluorine atoms and chlorine atoms.

The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl and butyl groups. The hydrocarbon group further has a divalent linking group such as a linking group containing an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom (e.g., a carbonyl group, an imino group, an ether bond, a silyl ether bond, a thioether bond, etc.). may

Examples of polar groups include linking groups such as carboxy groups, hydroxy groups, alkoxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, amido groups, and methylene groups (—(CH ₂ ) _n —, where n is 1 Groups in which these groups are bonded via the above integers) are included. 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. A cycloolefin resin containing a structural unit derived from a norbornene monomer having a polar group is easily dissolved in a solvent, for example, when forming a film by a solution casting method, and tends to increase the glass transition temperature of the resulting film. . Also, R ¹ and R ² of R ¹ to R ⁴ may be hydrogen atoms.

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

Examples of norbornene-based monomers having polar groups include the following.

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

The cycloolefin-based resin may further contain a structural unit derived from another monomer copolymerizable with the structural unit derived from the norbornene-based monomer. Examples of other copolymerizable monomers include norbornene-based monomers having no polar groups, and cycloolefin-based monomers having no norbornene skeleton such as cyclobutene, cyclopentene, cycloheptene, and dicyclopentadiene. be

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 even more preferably 40,000 to 200,000. . When the Mw of the cycloolefin resin is within the above range, the mechanical properties of the film can be enhanced without impairing the moldability.

The Mw of the cycloolefin resin can be measured by gel permeation chromatography (GPC). Specifically, it can be measured under the following conditions using HLC8220GPC manufactured by Tosoh Corporation.
(Measurement condition)
Eluent: THF
Column: TSKgel GMHXL x 2 manufactured by Tosoh Corporation Flow rate: 1.0 mL/min
Sample concentration: 0.1% by mass
Injection volume: 100 μL
Detector: RI
Calibration curve: standard polystyrene Column temperature: 40°C

The glass transition temperature Tg of the cycloolefin resin is generally preferably 110°C or higher, more preferably 110 to 350°C, and more preferably 120 to 250°C. When the Tg of the cycloolefin-based resin is 110°C or higher, the heat resistance of the resulting film is likely to be enhanced, and when it is 350°C or lower, thermal deterioration of the cycloolefin-based resin during molding can be easily suppressed.

Tg can be measured by a method based on JIS K 7121-2012 or ASTM D 3418-82 using DSC (Differential Scanning Colorimetry).

<Fumarate diester resin>
The fumarate diester-based resin may be a resin containing a structural unit derived from diisopropyl fumarate and a structural unit derived from a fumarate diester having an alkyl group having 1 or 2 carbon atoms.

The alkyl group having 1 or 2 carbon atoms in the fumarate diester having an alkyl group having 1 or 2 carbon atoms is a methyl group or an ethyl group, which is a halogen atom such as a fluorine atom or a chlorine atom, an ether group, an ester group, or It may be substituted with an amino group. Examples of fumarate diesters having an alkyl group having 1 or 2 carbon atoms include dimethyl fumarate and diethyl fumarate.

From the viewpoint of retardation properties and strength, the content of structural units derived from diisopropyl fumarate is preferably 50 to 99 mol%, more preferably 60 to 95 mol%; The content of the structural unit derived from the fumaric acid diester may preferably be 1 to 50 mol %, more preferably 5 to 40 mol %.

Examples of diester fumarate resins include diisopropyl fumarate/dimethyl fumarate copolymer and diisopropyl fumarate/diethyl fumarate copolymer.

The fumaric acid diester resin may further contain structural units derived from other monomers. Examples of other monomers include styrene, styrenes such as α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc. ( meth)acrylic acid esters; vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide olefins such as ethylene and propylene; and fumarate diesters other than fumarate diesters such as di-n-butyl fumarate and bis(2-ethylhexyl) fumarate.

The number average molecular weight of the fumaric acid diester resin is preferably 50,000 to 250,000. The number average molecular weight of the diester fumaric acid resin can be measured by the same method as described above.

<Polyester>
The polyester is a polymer obtained by polycondensation reaction of a diol component and a dicarboxylic acid component (however, it is different from a diester fumaric acid resin), and known ones can be used. Among them, the polyester is preferably a polyester having an aromatic ring. For example, a polyester containing a fluorene group-containing monomer unit described in Japanese Patent No. 6495075 can be used.

That is, a diol component comprising 9,9-bis(aryl-hydroxy(poly)alkoxyaryl)fluorene and optionally further comprising a C2-10 (preferably C2-4) aliphatic diol; A polyester obtained by a polycondensation reaction of a dicarboxylic acid and a dicarboxylic acid component including a non-fluorene aromatic dicarboxylic acid can be used. Films comprising such polyesters can provide films with birefringence and reverse wavelength dispersion.

The content of the thermoplastic resin is preferably 50% by mass or more, more preferably 70 to 99% by mass, relative to the obliquely stretched film.

(other ingredients)
The obliquely stretched film may further contain other components as necessary. Examples of other components include various additives (plasticizers, ultraviolet absorbers, retardation modifiers, antioxidants, deterioration inhibitors, release aids, surfactants), dyes, fine particles, and the like.

The fine particles (matting agent) can form unevenness on the surface of the obliquely stretched film and impart lubricity. The fine particles may be inorganic fine particles or resin fine particles. Examples of inorganic fine particles include fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, and calcium carbonate, preferably silicon dioxide particles (for example, Nippon Shokubai Co., Ltd., "Seahoster Series" KE-P20 , KE-P30, etc.). Examples of resin fine particles include (meth)acrylic crosslinked resin fine particles (for example, "Eposter series" MX100W, etc.). The average particle size of the microparticles can be, for example, 50-500 nm, preferably 100-300 nm. Within the above range, both transparency and anti-blocking properties can be achieved.

(thickness)
Although the thickness of the obliquely stretched film is not particularly limited, it is, for example, 10 to 200 μm, preferably 10 to 60 μm, more preferably 10 to 50 μm.

(saber form)
The saber form of the obliquely stretched film is preferably 10 mm or more. When the saber form of the obliquely stretched film is 10 mm or more, it has moderate distortion, so that the winding hardness when wound into a roll can be moderately loosened, and the optical film or the polarizing plate including the same can be wound. Occasionally, it is easy to suppress scratches on the optical film. Although the upper limit of the saber foam is not particularly limited, it can be set to, for example, 30 mm from the viewpoint of not impairing handling performance. The saber form of the obliquely stretched film is more preferably 10 to 30 mm, more preferably 15 to 30 mm.

Fig. 2 is a schematic diagram showing a method for measuring saber form. Saber form can be measured by the following method. When the midpoints in the width direction at the 0 m position, 10 m position, and 20 m position in the longitudinal direction of the film (direction perpendicular to the width direction of the film) are m0, m1, and m2, respectively, It is measured as the distance X across the width of the film of m1 (see Figure 2).

The saber form can be adjusted, for example, by adjusting the temperature of the stretching zone during oblique stretching or the difference between the temperature of the stretching zone and the temperature of the heat setting zone. For example, the temperature (T2) of the stretching zone during oblique stretching should be near the Tg of the film, and the temperature (T3) of the heat setting zone Z3 should be about the same as or higher than the temperature (T2) of the stretching zone. Practically, it is preferable to increase the saber form by reducing ΔT (=T2−T3) (preferably by setting it to a negative value with a large absolute value).

(Thickness deviation)
The thickness unevenness in the width direction of the obliquely stretched film is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 0.5 to 1.5 μm. If the thickness unevenness in the width direction is 3 μm or less, contact unevenness in the locally contacting portion can be reduced when the easy-adhesion layer is further provided and wound up. Further, when the thickness unevenness in the width direction is 0.5 μm or more, when the film is wound, the winding hardness can be moderately loosened, and scratches can be made more difficult to occur.

The thickness deviation can be measured using a known film thickness meter, for example, an offline contact film thickness meter (manufactured by YAMABUN). Specifically, the thickness of the film is measured at intervals of 1 mm along the width direction from one end to the other end in the width direction of the film. Then, the value of maximum value - minimum value is taken as the thickness deviation in the width direction of the film.

(orientation angle θ)
In the plane of the obliquely stretched film, the angle of the slow axis with respect to the width direction of the film (orientation angle θ) may be more than 0° and less than 90° with respect to the width direction of the film. Among them, when used as a λ / 4 retardation film, the orientation angle θ is preferably 20 to 70 ° with respect to the width direction of the film from the viewpoint of productivity when processing a polarizing plate and visibility when used as a display device. , preferably 40-50°. When the orientation angle θ is 40 to 50°, the anti-reflection performance against external light is excellent when processed into a circularly polarizing plate and mounted on a display device, which is particularly preferable.

The in-plane slow axis of the obliquely stretched film is measured by a known phase difference measuring device, such as an automatic birefringence meter AxoScan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) or an automatic birefringence meter KOBRA-21ADH (Oji Measurement It can be confirmed at a measurement wavelength of 550 nm or 590 nm by a device (manufactured by Kikiki Co., Ltd.).

(In-plane retardation Ro)
The in-plane retardation Ro of the obliquely stretched film can be appropriately set according to the application. For example, the in-plane retardation Ro measured at a measurement wavelength of 550 nm at 23° C. and 55% RH is preferably 95 to 170 nm, more preferably 130 to 150 nm. When Ro is within the above range, it is possible to appropriately adjust the black tint in a non-luminous state when processed into a circularly polarizing plate and mounted in a self-luminous display device, which is preferable.

Ro is defined by the following formula.
Formula (1): Ro = (nx-ny) x d
(In formula (1),
nx represents the refractive index in the in-plane slow axis direction of the film (the direction in which the refractive index is maximized),
ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the film,
d represents the thickness (nm) of the film. )

Ro can be measured by the following method.
1) The obliquely stretched film is conditioned in an environment of 23°C and 55% RH for 24 hours. The average refractive index of this obliquely stretched film is measured with an Abbe refractometer, and the thickness d is measured with a commercially available micrometer.
2) The in-plane retardation Ro of the film after humidity conditioning at a measurement wavelength of 550 nm is measured using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) in an environment of 23 ° C. and 55% RH. Measure below.

The in-plane retardation Ro of the obliquely stretched film can be adjusted by, for example, the type of resin, the type and amount of additives, stretching conditions, and the like.

1-2. Easy adhesion layer 12
The easy-adhesion layer has a function of enhancing adhesion between the obliquely stretched film and the polarizer. The indentation modulus of the easily adhesive layer is 1.5 to 3.0 GPa. When the indentation elastic modulus is 1.5 GPa or more, the film has appropriate hardness, so that when the optical film is wound into a roll, it is possible to prevent the formation of white marks due to the occurrence of local contact portions. When it is 3.0 GPa or less, the adhesiveness to the polarizer is less likely to be impaired. From the same point of view, the indentation elastic modulus of the easily adhesive layer is more preferably 2.0 to 2.5 GPa.

The indentation modulus of the easily adhesive layer can be measured by an indentation test by a nanoindentation method in accordance with ISO14577, specifically by Oliver-Pharr analysis. The indentation elastic modulus (composite elastic modulus Er) was measured using a nanoindentation (Triboscope) (manufactured by HYSITRON, indenter Berkovich type) as a measuring device, with a maximum indentation depth of 20 nm. It can be obtained by measuring the relationship between the thicknesses.

The indentation modulus of the easy-adhesion layer can be adjusted by adjusting the composition of the easy-adhesion layer (such as the type of resin) and the degree of cross-linking. For example, the indentation modulus can be increased by including polyolefin or a crosslinked product thereof in the composition constituting the easy adhesion layer, or by increasing the degree of crosslinkage of the crosslinked product.

The composition of the easy-adhesion layer should improve the adhesion between the obliquely stretched film and the polarizer, and should satisfy the above range for the indentation elastic modulus. The easy-adhesion layer contains a resin-containing composition (easy-adhesion layer composition) or a crosslinked product thereof.

(resin)
Resins include polyurethane, polyolefin, polyester, polyvinylidene chloride, acrylic polymer, modified silicone polymer, styrene-butadiene rubber, and the like. These resins may be used singly or in combination of two or more. For example, polyolefins and polyurethanes can be combined.

Polyurethane:
Polyurethane is a polymer obtained by reaction of, for example, a polyol compound and a polyisocyanate compound. Polyether polyol is included as a polyol component constituting polyurethane. Polytetramethylene glycol is more preferable as the polyether polyol.

Examples of commercially available polyurethane products include DIC Corporation, trade names "Hydran Series" AP-201, AP-40F, HW-140SF, WLS-202, and Daiichi Kogyo Seiyaku Co., Ltd., trade names. “Super Flex Series” SF-210, SF460, SF870, SF420, SF-420NS, manufactured by Mitsui Chemicals, Inc., trade name “Takelac Series” W-615, W6010, 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 Co., Ltd. ), developed product “SPX-0882”.

Polyolefin:
The polyolefin is preferably an acid-modified polyolefin. The acid-modified polyolefin is an olefin polymer containing structural units derived from unsaturated carboxylic acid, and may be a random copolymer or a graft copolymer. Examples of unsaturated carboxylic acids can be (meth)acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, and the like. The content of structural units derived from unsaturated carboxylic acid may be 0.1 to 25% by weight, preferably 0.5 to 15% by weight, based on the total structural units. The olefin can be an alkene of 2-6 carbon atoms such as ethylene, propylene. The content of structural units derived from olefins may be 50% by mass or more, preferably 70% by mass or more, based on all structural units.
The olefinic polymer may further contain structural units derived from other copolymer components such as (meth)acrylic acid esters.

Examples of acid-modified polyolefins include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid-maleic anhydride copolymer, acid-modified polyethylene, acid-modified polypropylene, acid-modified ethylene-propylene resin, acid Modified ethylene-butene resins, acid-modified propylene-butene resins, acid-modified ethylene-propylene-butene resins, and the like are included.
Examples of commercially available polyolefin products include Unitika Ltd., trade name "Arrow Base Series" SB-1200, SE-1010, SE-1013N, SE-1030N, SD-1010, TC-4010, TD-4010, Toho Chemical Co., Ltd., "High Tech Series" S3148, S3121, S8512, P-5060N, P-9018, Mitsui Chemicals, Inc., trade name "Unistall Series" S-120, S-75N, V100, H -200, H-300, EV210H, manufactured by Mitsui Chemicals Co., Ltd., trade name "Chemipearl Series" XHP-400, manufactured by Sumitomo Seika Co., Ltd., trade name "Saixen Series" Zaixen A, Zaixen L, Toyobo ( NZ-1004, NZ-1005, NZ-1022, etc. manufactured by Co., Ltd. under the trade name of “Hardren Series”.

polyester:
Examples of polyester include Toyobo Co., Ltd., trade names "Vylonal Series" MD1400, MD1480, MD1245, MD1500; Z-730, RZ-142, Z-687 and the like.

Polyvinylidene chloride:
Examples of polyvinylidene chloride include Asahi Kasei Co., Ltd.'s trade name "Saran Latex Series" L509. Examples of acrylic polymers include those manufactured by Nippon Shokubai Co., Ltd. under the trade name of "Epocross WS Series" WS-700, and manufactured by Shin-Nakamura Chemical Co., Ltd. under the trade name of "New Coat Series". Examples of modified silicone-based polymers include DIC Corporation's trade names "Ceranate Series" WSA1060 and WSA1070, and Asahi Kasei Chemicals Corporation's H7620, H7630 and H7650. Examples of styrene-butadiene rubber include NIPOL LX415, NIPOL LX407, NIPOL V1004, NIPOL MH8101, and SX1105 manufactured by Zeon Corporation.

(crosslinking agent)
The resin is preferably crosslinked with a crosslinking agent. Examples of cross-linking agents include oxazoline compounds, carbodiimide compounds, isocyanate compounds, epoxy compounds, and the like.

The oxazoline compound can be a compound having two or more oxazoline groups in the molecule. Examples of oxazoline compounds include Epocross (registered trademark) series (manufactured by Nippon Shokubai Co., Ltd.) such as WS-700 manufactured by Nippon Shokubai Co., Ltd.

A carbodiimide compound can be a compound having two or more carbodiimide groups in the molecule. Examples of carbodiimide compounds include Nisshinbo Chemical Co., Ltd., trade name "Carbodilite Series" V-02, V-02-L2, SV-02, V-04 and E-02.

The isocyanate compound is a compound containing two or more isocyanate groups in one molecule, and may be any of aliphatic isocyanate, aromatic isocyanate, and alicyclic isocyanate. Examples of isocyanate compounds include hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate. Also, the isocyanate compound may be masked with a blocking agent.

The epoxy compound is a compound having one or more epoxy groups in the molecule, or when using a polymer (epoxy resin) having two or more epoxy groups in the molecule, a functional group having reactivity with the epoxy group. A compound having two or more groups in the molecule may be used in combination. Examples of functional groups reactive with epoxy groups include carboxy groups, phenolic hydroxyl groups, mercapto groups, and primary or secondary aromatic amino groups. Considering three-dimensional curability, it is particularly preferable to have two or more of these functional groups in one molecule.
Polymers having one or more epoxy groups in the molecule include, for example, epoxy resins, bisphenol A type epoxy resin derived from bisphenol A and epichlorohydrin, bisphenol F type epoxy derived from bisphenol F and epichlorohydrin. resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F novolak type epoxy resin, alicyclic epoxy resin, diphenyl ether type epoxy resin, hydroquinone type epoxy resin, Naphthalene type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, polyfunctional epoxy resin such as trifunctional epoxy resin and tetrafunctional epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin , isocyanurate type epoxy resins, aliphatic chain epoxy resins, etc. These epoxy resins may be halogenated or hydrogenated. Examples of commercially available epoxy resin products include JER Coat 828, 1001, 801N, 806, 807, 152, 604, 630, 871, YX8000, YX8034, YX4000 manufactured by Japan Epoxy Resin Co., Ltd., and Epiclon manufactured by DIC Corporation. 830, EXA835LV, HP4032D, HP820, ADEKA Co., Ltd. EP4100 series, EP4000 series, EPU series, Daicel Chemical Co., Ltd. celoxide series (2021, 2021P, 2083, 2085, 3000, etc.), Epolead series, EHPE series, Nippon Steel Chemical Co., Ltd. YD series, YDF series, YDCN series, YDB series, phenoxy resin (polyhydroxy polyether synthesized from bisphenols and epichlorohydrin and having epoxy groups at both ends; YP series, etc.), Denacol series manufactured by Nagase Chemtex Co., Ltd., Epolite series manufactured by Kyoeisha Chemical Co., Ltd., and the like, but are not limited to these. These epoxy resins may be used in combination of two or more.

The content of the cross-linking agent may be set so that the indentation modulus of the easy-adhesion layer is within the above range. ~20 parts by mass.

(other ingredients)
The easy-adhesion layer may further contain other components than the above as needed. Examples of other ingredients include fine particles (matting agents), leveling agents, polymerization initiators, polymerization accelerators, viscosity modifiers, slip agents, dispersants, plasticizers, heat stabilizers, light stabilizers, lubricants, Oxidizing agents, flame retardants, colorants, antistatic agents, compatibilizers and the like are included.

Above all, the easy-adhesion layer preferably contains polyolefin or a crosslinked product thereof from the viewpoint of making the indentation elastic modulus equal to or higher than a certain level. The crosslinked product of polyolefin is more preferably a crosslinked product of acid-modified polyolefin (a crosslinked product of a composition containing acid-modified polyolefin and a cross-linking agent).

For example, the polyolefin content is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more relative to the resin contained in the composition. Moreover, the resin contained in the composition may be of one type, or may be of two or more types, and may include, for example, a polyolefin and a urethane-based resin. When polyolefin and urethane-based resin are included, their mass ratio can be, for example, polyolefin/urethane-based resin=90/10 to 40/60 mass ratio, preferably 90/10 to 50/50 mass ratio.

For example, the easy-adhesion layer preferably further contains fine particles (matting agent) in order to impart anti-blocking properties. Fine particles similar to those described above can be used.

The thickness of the easy-adhesion layer is not particularly limited, and is preferably 10-1000 nm, more preferably 20-500 nm, and still more preferably 50-400 nm.

2. Method for Producing Optical Film The method for producing an optical film of the present invention includes the steps of 1) preparing an obliquely stretched film, and 2) forming an easily adhesive layer on the surface of the obliquely stretched film, preferably 3). A step of winding the obtained optical film into a roll is further included.

About the process of 1) The diagonally stretched film can be obtained, for example, by diagonally stretching the original film.

(Preparation of raw film)
The original film can be obtained by a solution casting film forming method or a melt casting film forming method.

<Solution Casting Film Forming Method>
In the solution casting film forming method, the above resin and any other components are dissolved in a solvent to prepare a dope. A step of obtaining an anti-film is performed.

The solvent used for the dope contains at least an organic solvent (good solvent) capable of dissolving the resin. Examples of good solvents include chlorinated organic solvents such as methylene chloride; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone and tetrahydrofuran, preferably methylene chloride. The solvent to be used may further contain a poor solvent such as an aliphatic alcohol having 1 to 4 carbon atoms such as methanol and ethanol, from the viewpoint of enhancing the releasability of the cast film from the support.

The support used is not particularly limited, and may be, for example, a drum-shaped or belt-shaped metal support. Specifically, the metal support can be a mirror-finished stainless steel belt or a cast metal plated-surfaced drum. The surface temperature of the metal support is set to -50°C to a temperature at which the solvent does not boil and foam, preferably 0 to 100°C, more preferably 5 to 30°C.

In order for the obtained film to exhibit good flatness, the amount of residual solvent in the film when peeled from the metal support is preferably within the desired range. Here, the residual solvent amount is defined by the following formula.
Residual solvent amount (mass% or %) = {(MN) / N} × 100
Note that M is the mass (g) of a sample taken at an arbitrary point during or after the production of the film, and N is the mass (g) after heating M at 115° C. for 1 hour. In the film drying process, a roll drying method (a method in which the web is alternately passed through a number of rolls arranged vertically to dry) or a method in which the web is dried while being conveyed by a tenter method is adopted.

In this embodiment, an example in which the dope is cast on a metal support is shown, but the dope is not limited to this, and may be cast on a peelable temporary support (releasable support).

"Peelable" means that the object can be peeled off without damaging the other films and layers included in the laminated structure, and that the tensile stress due to the peeling is smaller than the breaking point stress of the other films and layers. The peelable support is used for the purpose of imparting self-holding properties to the film substrate and improving handleability. The peelable support is not particularly limited as long as it is a film that can maintain self-holding properties, but it is preferable to use a resin film. It is preferably composed of a resin (for example, a polyester-based resin) that is insoluble in water.

<Melt casting film forming method>
In the melt-casting film forming method, a resin composition containing the above resin is melted by heating to a fluidity temperature and then cast in a melted state, and then solidified by cooling to obtain a raw film.

Melt-casting film-forming methods include melt extrusion (molding), press molding, inflation, injection molding, blow molding, and stretch molding. The melt extrusion method is preferable from the viewpoint that it is easy to melt.

The raw materials used in the melt extrusion method are usually preferably kneaded and pelletized in advance. Pelletization is performed, for example, by supplying the above resin and any other components to an extruder with a feeder, kneading using a single-screw or twin-screw extruder, extruding from a die into strands, water-cooling or air-cooling, It can be done by cutting. The other components may be mixed with the resin before being supplied to the extruder, or the resin and the other components may be supplied to the extruder by separate feeders.

Next, the obtained pellets are used to form a film. The melting temperature when extruding the pellets using a single-screw or twin-screw extruder is (Tg + 30) ~ (Tg + 70) °C (Tg: glass transition temperature of the resin), or about 200 ~ 300 °C. Then, after filtering with a leaf disk type filter or the like to remove foreign matter, it is cast into a film form from a T-die.

Next, the cast melt is nipped between a cooling roll and an elastic touch roll, and the melt is solidified on the cooling roll. When the film is nipped between the cooling roll and the elastic touch roll, the film temperature on the side of the touch roll is preferably Tg (glass transition temperature) of the film or higher and Tg+110° C. or lower. A known roll can be used as the roll having an elastic surface for such purpose. The elastic touch roll is also called a pinching rotary body.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

(Diagonal stretching)
Next, the raw film thus obtained is stretched in an oblique direction to obtain an obliquely stretched film. Diagonal stretching can be performed using a known apparatus as disclosed in JP-A-2018-180163, for example.

FIG. 3 is a schematic diagram showing the configuration of the obliquely stretched film manufacturing apparatus 20. As shown in FIG. FIG. 4 is a schematic diagram showing the configuration of the extending portion 25. As shown in FIG.

In the present embodiment, the manufacturing apparatus 20 includes, in order from the upstream side in the film transport direction, a film feeding unit 22, a transport direction changing unit 23, a guide roll 24, a stretching unit 25, a guide roll 26, a transport direction changing unit 27, a film It includes a cutting device 28 and a film take-up 29 (see FIG. 3).

Then, as shown in FIGS. 3 and 4, one end side of the film in the width direction is gripped by a plurality of gripping tools (including gripping tools Ci), and the other end side is gripped by a plurality of gripping tools (including gripping tools Co). ), one of the gripping tools on the one end side and the other end side (for example, a plurality of gripping tools running along the rail Ri) is relatively advanced, and the other gripping tool (for example, running along the rail Ro By conveying the film while relatively delaying the plurality of grippers, the film is stretched in a direction oblique to the width direction.

As described above, the saber form of the obliquely stretched film can be adjusted by adjusting the temperature of the stretching zone and the heat setting zone during oblique stretching, the stretching ratio, the transport speed, and the like.

(Stretching conditions)
The heating zone Z of the stretching section 25 may consist of a preheating zone Z1, a stretching zone Z2 and a heat setting zone Z3 (see FIG. 4).

The preheating zone Z1 is a section at the entrance of the heating zone Z in which the grippers Ci and Co gripping both ends of the film travel while maintaining a constant spacing (in the film width direction) on the left and right. The stretching zone Z2 is a section in which the diagonal stretching process described above is performed. At this time, if necessary, the film may be stretched in the longitudinal direction or the transverse direction before and after the diagonal stretching. The heat setting zone Z3 is a section in which a heat setting process for fixing the optical axis (slow axis) of the film is performed after the oblique stretching process. The heat setting zone Z3 can facilitate fixing the orientation state of the resin molecules.

When the glass transition temperature of the original film is Tg, the temperature (T1) of the preheating zone Z1 is preferably Tg-(Tg+30)°C. The temperature (T2) of the drawing zone Z2 is preferably Tg-(Tg+30)°C, more preferably Tg-(Tg+25)°C. The temperature (T3) of the heat fixing zone Z3 is preferably (Tg-20) to (Tg+30)°C, more preferably (Tg-10) to (Tg+25)°C.

From the viewpoint of setting the saber form of the resulting film within the above range, in the stretching zone 25, the temperature (T2) of the stretching zone Z2 is brought as close as possible to the Tg of the film, and the temperature (T3) of the heat setting zone Z3 is set to It is preferably equal to or higher than the temperature of the draw zone (T2). Specifically, by setting the temperature difference ΔT (=T2−T3) to preferably −10 to 5° C., more preferably −10 to 2° C., the saber foam can be made moderately large. That is, by setting the temperature difference ΔT to a small value (preferably a negative value with a large absolute value), a difference in elongation of the film between the rail Ro side and the rail Ri side during diagonal stretching tends to occur (Fig. 4), the saber form tends to be large.

The temperature (T1 to T3) in each zone indicates the temperature of the atmosphere in each zone. In addition, the ambient temperature and the surface temperature of the film can be substantially the same.

The temperature distribution in the width direction of the film in the stretching zone Z2 can be controlled, for example, by adjusting the opening of nozzles for sending hot air into the thermostatic chamber so that there is a difference in the width direction, or by arranging heaters in the width direction and controlling the heating. can be done with

Further, if the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the stretching ratio R (W/Wo) in the stretching step is preferably 1.3 to 3.0. 0, more preferably 1.5 to 2.8 (see FIG. 4). When the draw ratio is within this range, thickness unevenness in the width direction of the film is reduced, which is preferable. In the stretching zone Z2 of the diagonal stretching tenter, if the stretching temperature is different in the width direction, it is possible to bring the thickness unevenness in the width direction to a better level. The above draw ratio R is equal to the ratio (W2/W1) when the interval W1 between both ends of the clip gripped at the entrance of the tenter becomes the interval W2 at the exit of the tenter.

About the process of 2) An easy-adhesion layer is formed on the surface of the obtained diagonally stretched film. For example, the easy-adhesion layer can be formed by applying (applying) the composition for the easy-adhesion layer to the surface of the obliquely stretched film, followed by drying or heating. The easy-adhesion layer may be formed only on one side of the obliquely stretched film, or may be formed on both sides.

The easy-adhesion layer composition can be a solution in which the aforementioned components (resin, optional cross-linking agent, other components, etc.) are dispersed or dissolved in a solvent (eg, water). The total solid content concentration of the easy adhesion layer composition can be set according to the type of components, solubility, coating viscosity, wettability, thickness after coating, and the like. In order to obtain an easily adhesive layer with high surface uniformity, the total solid content concentration is preferably 1 to 100 parts by mass, more preferably 1 to 50 parts by mass with respect to 100 parts by mass of the solvent.

Any appropriate viscosity can be adopted as the viscosity of the easy-adhesion layer composition within a range that allows coating. The viscosity is preferably 1 to 50 (mPa·sec), more preferably 2 to 10 (mPa·sec) when measured at a shear rate of 1000 (1/s) at 23°C. If it is said range, the easy-adhesion layer excellent in surface uniformity can be formed.

The easy-adhesion layer composition can be prepared by any method. For example, a commercially available solution or dispersion may be used, a solvent may be added to a commercially available solution or dispersion, or a solid content may be dissolved or dispersed in various solvents and used.

Any method may be used to apply the composition for the easy-adhesion layer, and for example, a method using a gravure die or a coater may be used. When providing the easy-adhesion layer to the obliquely stretched film, the surface of the obliquely stretched film may be subjected to solvent modification, corona treatment, plasma treatment, or the like as preliminary treatment for improving wettability.

Regarding Step 3) The obtained optical film may be further wound into a roll. Winding of the optical film can be performed by a known method (for example, constant torque method, constant tension method, taper tension method, etc.).

The winding length of the optical film can be, for example, 1000 to 7200 m. The width of the optical film can be, for example, 1000-3000 mm.

3. Polarizing Plate The polarizing plate of the present invention includes a polarizer and the optical film of the present invention arranged on at least one surface of the polarizer.

FIG. 5A is a cross-sectional view showing the configuration of the polarizing plate 30 according to one embodiment of the present invention. FIG. 5B is an exploded perspective view showing the positional relationship among the polarizer 31, the optical film 10, and the protective film 32 that constitute the polarizing plate 30. FIG.

As shown in FIG. 5A, the polarizing plate 30 includes a polarizer 31, an optical film 10 arranged on one side thereof, a protective film 32 arranged on the other side, a polarizer 31 and the optical film 10 and two adhesive layers 33 disposed between the polarizer 31 and the protective film 33 .

The polarizing plate 30 may be a long polarizing plate, or may be a sheet-like polarizing plate obtained by cutting a long polarizing plate along the width direction perpendicular to the longitudinal direction.

3-1. Polarizer 31
A polarizer is an element that passes only light with a plane of polarization in a certain direction. A polarizer can generally be a polyvinyl alcohol-based polarizing film. Examples of polyvinyl alcohol-based polarizing films include polyvinyl alcohol-based films dyed with iodine and those dyed with dichroic dyes.

The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a dichroic dye (preferably a film further subjected to durability treatment with a boron compound); A film obtained by dyeing an alcohol-based film with iodine or a dichroic dye and then uniaxially stretching the film (preferably, a film further subjected to a durability treatment with a boron compound) may be used. The absorption axis of a polarizer is usually parallel to the direction of maximum stretch.

The thickness of the polarizer is 5-40 μm, preferably 5-30 μm.

3-2. optical film 10
The optical film is arranged so that the easy-adhesion layer faces the polarizer (see FIG. 5A).

The in-plane slow axis of the obliquely stretched film constituting the optical film is inclined, for example, by 10 to 80° with respect to one side (eg, side 10a) of the rectangular film outline in the film plane (see FIG. 5B). ). The side 10a is a side corresponding to the width direction of the obliquely stretched strip film. The angle of the in-plane slow axis with respect to the side 10a in the film plane is preferably 30 to 60°, more preferably 40 to 50°. That is, the angle between the in-plane slow axis of the obliquely stretched film and the absorption axis (or transmission axis) of the polarizer is, for example, 10 to 80°, preferably 30 to 60°, more preferably 40 to 50°.

Other layers (for example, a hard coat layer, a low refractive index layer, an antireflection layer, and a liquid crystal (positive C-type plate) are appropriately provided on the surface of the obliquely stretched film opposite to the polarizer, depending on the application. good too.

3-3. Protective film 32
The protective film may be a transparent resin film (eg, cellulose ester film, cycloolefin resin, acrylic resin, etc.). Also, the protective film may be an optical compensation film that compensates for optical properties such as viewing angle expansion. For example, the protective film may be the optical film described above.

3-4. Adhesive layer 33
An adhesive layer can be disposed between the polarizer and the optical film and between the polarizer and the protective film, respectively. The adhesive layer can be a layer obtained from a water-based adhesive or a cured product layer of an ultraviolet curable adhesive.

The water-based adhesive can be, for example, an adhesive containing a vinyl alcohol-based polymer; an adhesive containing a water-soluble cross-linking agent for a vinyl alcohol-based polymer such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. These adhesives may further contain other additives and catalysts such as acids as necessary.

As the UV-curable adhesive composition, a photo-radical polymerization type composition using photo-radical polymerization, a photo-cationic polymerization type composition using photo-cationic polymerization, and a hybrid composition using both photo-radical polymerization and photo-cation polymerization. things are known.

As the photoradical polymerizable composition, a radically polymerizable compound containing a polar group such as a hydroxy group or a carboxyl group and a radically polymerizable compound containing no polar group described in JP-A-2008-009329 are contained in a specific proportion. composition) and the like are known. In particular, the radically polymerizable compound is preferably a compound having a radically polymerizable ethylenically unsaturated bond. Preferred examples of compounds having a radically polymerizable ethylenically unsaturated bond include compounds having a (meth)acryloyl group. Examples of compounds having a (meth)acryloyl group include N-substituted (meth)acrylamide compounds and (meth)acrylate compounds. (Meth)acrylamide means acrylamide or methacrylamide.

As the photocationically polymerizable composition, as disclosed in JP-A-2011-028234, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) light having a wavelength longer than 380 nm and (δ) a naphthalene-based photosensitizing aid. However, other ultraviolet curable adhesives may be used.

Although the thickness of the adhesive layer is not particularly limited, it can be, for example, 0.01 to 10 μm, preferably about 0.01 to 5 μm.

3-5. Manufacturing Method of Polarizing Plate 30 A polarizing plate can be obtained through a process of laminating an optical film, a polarizer and a protective film via an adhesive. As the adhesive, the above-described water-based adhesive or ultraviolet curing adhesive is used.

For example, a method for producing a polarizing plate using an ultraviolet curable adhesive includes 1) a step of pretreating a retardation film or a protective film, and 2) laminating a retardation film, a polarizer and a protective film with an ultraviolet curable adhesive. Step 3) includes a step of curing the ultraviolet curable adhesive.

1) Pretreatment process The surface of the optical film or protective film to be adhered to the polarizer is subjected to an easy-adhesion treatment. The easy-adhesion treatment includes corona treatment, plasma treatment, and the like. As for the optical film, the easy-adhesion layer is pretreated.

2) Bonding Step Next, an ultraviolet curable adhesive is applied to the adhesive surface of at least one of the polarizer and the optical film (or protective film). The method of applying the UV-curable adhesive is not particularly limited, and for example, a doctor blade, wire bar, die coater, comma coater, gravure coater, or the like can be used. Alternatively, after applying (casting) the ultraviolet curable adhesive between the polarizer and the optical film (or the opposing film), the ultraviolet curable adhesive may be uniformly spread by applying pressure with a roller or the like.

Next, the polarizer and the optical film (or protective film) are pasted together via an ultraviolet curable adhesive. The lamination can be performed, for example, by sandwiching and pressurizing a polarizer and an optical film (or a facing film) laminated with an ultraviolet curable adhesive interposed therebetween with pressure rollers or the like.

3) Curing step Next, the ultraviolet curable adhesive is irradiated with ultraviolet rays to obtain a cationically polymerizable compound (e.g., an epoxy compound or an oxetane compound) or a radically polymerizable compound (e.g., an acrylate compound, an acrylamide compound, etc.). The UV curable adhesive is cured to adhere the polarizer and the optical film (or the opposing film).

The irradiation conditions of the ultraviolet rays may be any conditions as long as the ultraviolet curing adhesive can be cured. For example, the dose of ultraviolet rays (accumulated light dose) is, for example, 50 to 1500 mJ/cm ² , preferably 100 to 500 mJ/cm ² .

4. Display Device The display device of the present invention includes a display element and the polarizing plate of the present invention.

The display element can be an organic EL element, an inorganic EL element, a liquid crystal element, or the like.

The polarizing plate is arranged on the viewing side of the display element. In the polarizing plate, the optical film is arranged between the polarizer and the display element; specifically, it is preferably arranged so that the obliquely stretched film faces the display element side.

In the polarizing plate, the protective film is arranged on the viewing side of the polarizer. The protective film may be further subjected to surface treatments such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment, if necessary. Alternatively, the protective film may be treated, if necessary, to improve visibility when viewed through polarized sunglasses (typically, imparting (elliptical) circular polarization function, imparting ultra-high retardation ) may be applied. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. That is, the polarizing plate is also suitable for display devices that can be used outdoors. In that case, the optical film described above may be used as the protective film.

FIG. 6 is a cross-sectional schematic diagram showing the configuration of an organic EL display device 40 (display device) according to one embodiment of the present invention. The organic EL display device 40 includes an organic EL element 50 (display element) and a polarizing plate 30 (circularly polarizing plate).

(Organic EL element 50)
The organic EL element 50 has a metal electrode 52, a light emitting layer 53, a transparent electrode (such as ITO) 54, and a sealing layer 55 in this order on a transparent substrate 51 such as a glass plate or a transparent film.

The metal electrode 52 can function as a cathode. For the metal electrode 52, a substance with a small work function is preferably used in order to facilitate electron injection and increase luminous efficiency, and Mg--Ag and Al--Li are usually used.

The light-emitting layer 53 is a laminate of organic thin films. It may be a laminate with an electron injection layer made of a perylene derivative or the like, or a laminate of these hole injection layers, light emitting layers, and electron injection layers.

The transparent electrode 54 can function as an anode. The transparent electrode 54 can typically be composed of a transparent conductor such as indium tin oxide (ITO).

The sealing layer 55 can be a transparent substrate such as a glass plate or a transparent film, or a sealing film such as a sealant.

By applying a voltage between the metal electrode 52 and the transparent electrode 54, holes and electrons are injected into the light-emitting layer 53, and the energy generated by the recombination of these holes and electrons excites the fluorescent material. , and emits light when the excited fluorescent substance returns to the ground state, resulting in luminescence.

(Polarizing plate 30)
The polarizing plate 30 may be a circularly polarizing plate (the polarizing plate described above) arranged on the surface of the organic EL element 50 on the viewing side. The polarizing plate 30 can suppress reflection of external light entering from the outside of the organic EL display device 40 due to indoor lighting or the like.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

1. Materials and production of obliquely stretched film <Materials>
・Cycloolefin-based resin ARTON/G7810 manufactured by JSR Corporation (cycloolefin-based resin containing the following structural units, Tg = 178°C, Mw = 140,000)

- Polyester A fluorene group-containing polyester synthesized by the method described in Example 1 (paragraph 0181) of Japanese Patent No. 6495075 was used. The composition of the fluorene group-containing polyester is as follows: diol component: 9,9-bis[4-(2-hydroxyethoxy)3-phenylphenyl]fluorene (BOPPEF) 80 mol%, ethylene glycol (EG) 20 mol%, dicarboxylic acid component : 85 mol % of 1,4-cyclohexanedicarboxylic acid (CHDA) and 15 mol % of terephthalic acid (TPA). The resulting polyester had a Tg of 139° C. and an Mw of 29,700.
Fumaric acid diester-based resin Polyfumaric acid diester (diisopropyl fumarate homopolymer, Mw = 364000, Mn = 118000) synthesized by the method described in Synthesis Example 3 of paragraph 0081 of JP-A-2016-98371 was used. .

The Tg and Mw of the resin were measured by the following methods.

(Tg)
The Tg of the resin was measured according to JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

(Mw)
The Mw of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) under the following conditions.
(Measurement condition)
Eluent: THF
Column: TSKgel GMHXL x 2 manufactured by Tosoh Corporation
Flow rate: 1.0 mL/min
Sample concentration: 0.1% by mass
Injection volume: 100 μL
Detector: RI
Calibration curve: standard polystyrene

<Preparation of raw film 1>
(Preparation of fine particle addition liquid)
After stirring and mixing the following components with a dissolver for 50 minutes, the mixture was dispersed with a Manton Gaulin. Further, dispersion was carried out using an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid.
Fine particles (Aerosil R972V: manufactured by Nippon Aerosil Co., Ltd.): 4 parts by mass Dichloromethane: 48 parts by mass Ethanol: 48 parts by mass

(Preparation of dope)
Next, a dope having the following composition was prepared. First, dichloromethane and ethanol were added to a pressurized dissolution tank. The above cycloolefin resin (G7810) was put into a pressurized dissolution tank containing a mixed solution of dichloromethane and ethanol while stirring. Furthermore, 15 minutes after the start of the addition of the solvent, the microparticle addition liquid prepared above was added, heated to 80° C., and completely dissolved with stirring. At this time, the temperature was raised from room temperature at a rate of 5°C/min, dissolved in 30 minutes, and then lowered at a rate of 3°C/min. The resulting solution was filtered through a filter to prepare a dope.
Cycloolefin resin: 100 parts by mass Dichloromethane: 230 parts by mass Ethanol: 15 parts by mass Microparticle additive liquid: 5 parts by mass

(film formation)
Then, using an endless belt casting apparatus, the dope was uniformly cast on a stainless steel belt at a temperature of 31° C. and a width of 1800 mm. The temperature of the stainless steel belt was controlled at 20°C. Then, the solvent was evaporated on the stainless belt until the residual solvent amount in the cast dope reached 100% by mass, and the dope was peeled off from the stainless belt to obtain a film. At the time of peeling, the film was stretched 1.16 times in the transport direction, and then stretched 1.3 times in the width direction at 128°C.
The obtained film is dried at 120° C. for 15 minutes while being transported by a number of rollers in a drying zone, and the end portion sandwiched between tenter clips is slit with a laser cutter and wound up to obtain a raw film 1 having a thickness of 78 μm. made.

<Preparation of raw film 2>
A raw film 2 having a thickness of 90 μm was obtained in the same manner as the raw film 1 except that the cycloolefin-based resin was changed to the polyester (fluorene group-containing polyester).

<Preparation of raw film 3>
(Preparation of Peelable Support)
After solution casting the dope used in the preparation of raw film 1, it was dried and peeled off to obtain a film-like material. The resulting film-like material was stretched 1-fold in the transport direction and 1.1-fold in the width direction at 128°C. After stretching, the film was dried at 120° C., and the edges were slit with a laser cutter to obtain a peelable support (thickness: 84 μm).

(Production of laminated film)
5 parts by mass of LA-F70 manufactured by ADEKA Co., Ltd. was added to 100 parts by mass of the polyester (diisopropyl polyfumarate), and dissolved in a mixed solvent of MEK/toluene (7/3 mass ratio) at a solid content of 20% by mass. , as a solution. Subsequently, the above-prepared solution was applied on the surface of the peelable support prepared above with a comma coater and dried to form a resin layer having a thickness of 40 μm. As a result, a strip-shaped laminated film (original film 3) was obtained in which the resin layer was laminated on the peelable support.

<Preparation of diagonally stretched film 1>
The raw film 1 thus obtained is set in the film feeding section 22 of the obliquely stretched film manufacturing apparatus 20 shown in FIG. to obtain a belt-like obliquely stretched film 1 having a thickness of 45 μm.
Then, the obliquely stretched film 1 was conveyed to the film winding section 29 and wound into a roll. The saber foam was adjusted by the temperatures of the stretching zone (T2) and the heat setting zone (T3). Specifically, the draw ratio is 1.73 times, the temperature in the drawing zone (T2) of the drawing section 25 is (Tg+23)° C., and the temperature in the heat setting zone (T3) is Tg+22° C. (Tg is the film glass transition temperature) (see FIG. 4).

<Production of obliquely stretched films 2 to 8 and 10>
Diagonally stretched films 2 to 8 and 10 were prepared in the same manner as for diagonally stretched film 1, except that the stretching conditions (stretching temperature in the stretching zone and heat setting zone) and the type of raw film were changed as shown in Table 1. Obtained.

<Production of obliquely stretched film 9>
The obtained roll body of the raw film 3 (laminated film) is set in the film feeding unit 22 of the obliquely stretched film manufacturing apparatus 20 shown in FIG. and diagonally stretched in the stretching section 25 to obtain a long diagonally stretched film 9 having a thickness of 75 μm as a laminated film.
Then, the obliquely stretched film 10 was conveyed to the film winding section 29 and wound into a roll. The draw ratio is 2.0 times, the temperature in the drawing zone (T2) of the drawing section 25 is (Tg+0)° C., and the temperature in the heat setting zone (T3) of the drawing section 25 is (Tg-3 )° C. (Tg is the glass transition temperature of the peelable support) (see FIG. 4).

<Evaluation>
The optical properties (orientation angle, in-plane retardation Ro), saber form and thickness deviation of the obtained obliquely stretched film were measured by the following methods.

(1) Optical properties (in-plane retardation Ro, orientation angle θ)
(In-plane retardation Ro)
Under the environment of 23° C. and 55% RH, the birefringence at a wavelength of 550 nm was measured using Axoscan manufactured by Axometrics, and the in-plane retardation value Ro was calculated from the above formula (1).

(orientation angle θ)
Measured at a wavelength of 590 nm using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.). θ.

The in-plane retardation Ro and the orientation angle θ of the obliquely stretched film 10 were measured by peeling off the peelable support and using a single layer made of diisopropyl fumarate.

(2) Saber Form As shown in FIG. 2, 20 m of the film was cut in the longitudinal direction, and the center points m0, m1 and m2 in the width direction of the film were marked at the 0 m, 10 m and 20 m positions, respectively. A thread was stretched so as to pass through the center points (m0 and m2) at the 0 m position and the 20 m position, and the distance X between the mark of the center point m1 at the 10 m position and the thread was measured, and this was defined as "saber form". In addition, the measurement of the saber form of the obliquely stretched film 10 was performed with the peelable support attached (laminated state).

(3) Thickness deviation Using an offline contact film thickness gauge (manufactured by YAMABUN), the thickness of the film is measured at intervals of 1 mm along the width direction of the obliquely stretched film from one end to the other end in the width direction. was measured. Then, (maximum value of film thickness - minimum value of film thickness) was defined as "thickness deviation in width direction". The thickness deviation of the obliquely stretched film 10 was measured with the peelable support attached (laminated state).

2. Preparation of easy-adhesion layer composition (manufacture of polyolefin resin aqueous dispersion E-1)
60.0 g of polyolefin resin [Bondine HX-8290, Sumitomo Chemical Co., Ltd.], 60.0 g of isopropanol (Wako Pure Chemical Industries, Ltd.) ), 2.2 g of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) and 177.8 g of distilled water were placed in a glass container and stirred at a rotation speed of 300 rpm. It was confirmed that it was in a floating state. Therefore, while maintaining this state, the power of the heater was turned on after 10 minutes to heat. Then, the temperature in the system was kept at 120° C. and the mixture was further stirred for 20 minutes. Then, after cooling to room temperature (approximately 25° C.) with air cooling while stirring at a rotation speed of 300 rpm, pressure filtration (air pressure 0.2 MPa) through a 300-mesh stainless steel filter (wire diameter 0.035 mm, plain weave). to obtain a milky white homogeneous polyolefin resin aqueous dispersion E-1.

(Production of polyurethane resin aqueous dispersion U-1)
345 parts by mass of polytetramethylene glycol having an average molecular weight of 1970, 77.8 parts by mass of isophorone diisocyanate, and 0.03 parts by mass of dibutyltin dilaurate were charged into a reactor equipped with a stirrer, thermometer, nitrogen seal tube, and cooler. and 80° C. for 2 hours. After cooling the reaction solution to 50° C., 11.7 parts by mass of dimethylpropanolamine, 8.85 parts by mass of triethylamine and 177 parts by mass of acetone were added and reacted for 3 hours. Further, 175 parts by mass of acetone was added to the reaction solution and cooled to 30° C., resulting in 13.4 parts by mass of isophorone diisocyanate, 1.07 parts by mass of monoethanolamine, 87.9 parts by mass of isopropyl alcohol, and 1039 parts by mass of water. A mixed liquid consisting of three parts was added and stirred at high speed, and acetone and IPA were distilled off from this liquid to obtain a polyether type polyurethane resin aqueous dispersion U-1.

(crosslinking agent)
WS-700 manufactured by Nippon Shokubai Co., Ltd.
Denacol EX-313 manufactured by Nagase ChemteX Co., Ltd.

(others)
Fine particles: KE-P30 manufactured by Nippon Shokubai Co., Ltd.

<Preparation of Composition A for Easy Adhesion Layer>
The following components were diluted with a diluent (water/methanol = 50/50 (% by mass)) so that the solid content was 2.8% by mass to prepare a composition A for an easy adhesion layer.
Polyolefin resin aqueous dispersion E-1: (in polyolefin resin amount) 100 parts by mass Crosslinking agent (WS-700 manufactured by Nippon Shokubai Co., Ltd.): 5 parts by mass Fine particles (KE-P30 manufactured by Nippon Shokubai Co., Ltd.): 8 parts by mass

<Preparation of Composition B for Easy Adhesion Layer>
The compounding ratio of the polyolefin resin aqueous dispersion E-1 and the polyurethane resin aqueous dispersion U-1 was changed so that the content ratio of the polyolefin resin and the polyurethane resin was the value shown in Table 2, and Nagase ChemteX was used as the cross-linking agent. An easy-adhesion layer composition B was prepared in the same manner as the easy-adhesion layer composition A except that Denacol EX-313 manufactured by Co., Ltd. was changed to 3 parts by mass.

<Preparation of Compositions C to E for Easy Adhesion Layer>
The easy-adhesion layer composition except that the compounding ratio of the polyolefin resin aqueous dispersion E-1 and the polyurethane resin aqueous dispersion U-1 was changed so that the content ratio of the polyolefin resin and the polyurethane resin was the value shown in Table 2. Easy adhesion layer compositions C to E were prepared in the same manner as in product A.

Table 2 shows the compositions of the easily adhesive layer compositions A to E thus obtained.

3. Preparation and Evaluation of Optical Film <Preparation of Optical Film 1>
While conveying the obliquely stretched film 1 at a speed of 20 m/min, the obliquely stretched film 1 was subjected to surface treatment by irradiation under the condition of an output of 2 kW using a corona treatment device (manufactured by Kasuga Denki Co., Ltd.). Then, using a vacuum extrusion die coater, the easy-adhesion layer composition B is applied, dried and cured in an atmosphere of 120° C. to form an easy-adhesion layer having a thickness of 0.22 μm, and the optical film 1 is obtained. Obtained.

<Production of optical films 2 to 14>
Optical Films 2 to 14 were obtained in the same manner as Optical Film 1, except that the combination of the obliquely stretched film and the easy-adhesion layer composition was changed as shown in Table 3. The optical film 13 was prepared by applying the easy-adhesion layer composition to the diisopropyl polyfumarate layer side of the obliquely stretched film 10 (laminated film).

<Evaluation>
The indentation elastic moduli of the easily adhesive layers of the obtained optical films 1 to 14 were measured by the following method.

(indentation modulus)
The indentation elastic modulus of the easily adhesive layer of the obtained laminate was measured using a nanoindentation (Triboscope) (manufactured by HYSITRON, indenter Berkovich type) at a maximum indentation depth of 20 nm. Measurements were taken at N=5 and the average value was adopted.

In addition, the white marks, scratches (on the polarizing plate), and display characteristics (on the display device) of the optical films 1 to 14 were evaluated by the following methods.

(1) White Marks A 3-m long film was unwound from the roll body on which the obtained optical film was wound, and its surface was observed using a halogen lamp to evaluate the presence and degree of white marks.
⊚: less than 5% of the film observed area ○: 5% or more and less than 10% of the film observed area ×: 10% or more of the film observed area

(2) Scratches (Fabrication of polarizer)
A polyvinyl alcohol film with a thickness of 80 μm was dyed in a 0.3% iodine aqueous solution. After that, the dyed polyvinyl alcohol film was stretched up to 5 times in a 4% boric acid aqueous solution and a 2% potassium iodide aqueous solution, and then dried at 50° C. for 4 minutes to produce a polarizer.

(Preparation of polarizing plate)
Then, the optical film prepared above, the polarizer prepared above, and a TAC film (40 μm thick) were adhered via a UV adhesive to obtain a layer configuration of TAC film/UV adhesive layer/polarizer/UV adhesive layer/optical film. Polarizing plates (circularly polarizing plates) 1 to 12 and 14 were obtained. As the UV adhesive, the adhesive composition described in Production Example 2 of Japanese Patent No. 5971498 was used. The optical film was arranged so that the surface on the easy adhesion layer side was on the UV adhesion layer side. The angle between the slow axis of the obliquely stretched optical film and the absorption axis of the polarizer was 45°. As for the optical film 13, after peeling off the peelable support, the optical film 13 was attached to the polarizer so that the easy-adhesion side faces the UV adhesive layer side, thereby producing the circularly polarizing plate 13.

The obtained circularly polarizing plate was taken out with a length of 3 m, and S-light was applied to evaluate the presence or absence and degree of scratches on the surface.
◯: less than 5% of the observed area △: 5% or more of the observed area and less than 10% of the observed area, a level that does not pose a practical problem ×: 10% or more of the observed area, which is a practical problem A level of △ or higher was judged to be good.

(3) Display characteristics The circularly polarizing plate was removed from a commercially available organic electroluminescence display panel OLED55B9PJA (manufactured by LG). The circularly polarizing plate prepared above was pasted onto the light-emitting panel with an adhesive NCF-N632 (manufactured by Lintec) so that the obliquely stretched film side faced the light-emitting panel. This was displayed in black, observed under a bright field, and evaluated according to the following evaluation criteria.
○: Less than 5% of the entire screen area where light leakage is observed. ×: 5% or more of the entire screen area where light leakage is observed.

Table 3 shows the evaluation results of the optical films 1 to 14.

As shown in Table 3, the optical films 1 to 4, 6 to 11, 13 and 14 (Examples) in which the indentation elastic modulus of the easily adhesive layer is 1.5 GPa or more have a saber foam of 10 mm or more in the obliquely stretched film. It can be seen that white traces can be suppressed in spite of the large . However, the optical film 11 with a saber form exceeding 30 mm was slightly inferior in handleability.

On the other hand, the optical film 12 (comparative example) in which the saber form of the obliquely stretched film is less than 10 mm has many scratches on the film surface and many light leaks in the display device. On the other hand, optical film 5 (comparative example) in which the saber form of the obliquely stretched film is 10 mm or more and the indentation elastic modulus of the easy-adhesive layer is less than 1.5 GPa has white marks.

This application claims priority based on Japanese Patent Application No. 2021-018479 filed on February 8, 2021. All contents described in the 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 a display device that can suppress fine scratches due to winding and make it difficult for white marks to occur.

REFERENCE SIGNS LIST 10 optical film 11 obliquely stretched film 12 easy-adhesive layer 20 manufacturing device 22 film feeding section 23 conveying direction changing section 24 guide roll 25 stretching section 26 guide roll 27 conveying direction changing section 28 film cutting device 29 film winding section 30 polarizing plate 31 Polarizer 32 Protective film 33 Adhesive layer 40 Organic EL display device 50 Organic EL element

Claims

A strip-shaped optical film comprising an obliquely stretched film having a slow axis inclined with respect to the width direction of the film in the plane of the film, and an easy-adhesion layer disposed on the surface of the obliquely stretched film,
When the midpoints in the width direction of the film are m0, m1, and m2 at the 0 m position, 10 m position, and 20 m position in the direction perpendicular to the width direction of the obliquely stretched film, the center line connecting the m0 and the m2. , the saber form represented by the distance in the width direction of the film of the m1 is 10 mm or more,
The indentation modulus of the easily adhesive layer is 1.5 to 3.0 GPa,
optical film.
The indentation modulus of the easy-adhesion layer is 2.0 to 2.5 GPa,
The optical film according to claim 1.
The easy-adhesion layer contains polyolefin or a crosslinked product thereof,
The optical film according to claim 1 or 2.
When the thickness is measured at intervals of 1 mm in the width direction of the obliquely stretched film, the thickness deviation represented by the difference between the maximum thickness and the minimum thickness is 0.5 to 1.5 μm.
The optical film according to any one of claims 1 to 3.
The obliquely stretched film contains a cycloolefin-based resin, a fumaric acid diester-based resin, or a polyester (but different from the fumaric acid diester-based resin).
The optical film according to any one of claims 1 to 4.
In the plane of the obliquely stretched film, the angle of the slow axis with respect to the width direction of the film is 40 to 50 °.
The optical film according to any one of claims 1 to 5.
The in-plane retardation Ro of the obliquely stretched film at a wavelength of 550 nm represented by the following formula (1) is 95 to 170 nm.
The optical film according to any one of claims 1-6.
Formula (1): Ro = (nx-ny) x d
(In formula (1),
nx represents the refractive index in the slow axis direction,
ny represents the refractive index in the direction perpendicular to the slow axis in the film plane,
d represents the film thickness (nm))
a polarizer;
The optical film according to any one of claims 1 to 7, disposed on at least one surface thereof;
An adhesive layer disposed between the polarizer and the easy-adhesion layer,
Polarizer.
a display element;
A polarizing plate according to claim 8,
The optical film is arranged between the display element and the polarizer,
display device.
The display element is an organic EL element or an inorganic EL element,
The display device according to claim 9.