WO2015159679A1 - Polarizing plate, method for manufacturing polarizing plate, liquid-crystal display, and organic electroluminescent display - Google Patents

Abstract

This invention addresses the problem of providing a polarizing plate that is provided with an obliquely-oriented optical film and minimizes physical distortion. Said polarizing plate (12), which comprises a polarizer (21), a first optical film (22) provided so as to face one surface of the polarizer (21), and a second optical film (24) provided so as to face the other surface of the polarizer (21), is characterized in that the slow axis of the first optical film (22) and the absorption axis of the polarizer (21) intersect at an angle (θ) in the 30-60° range and the dimensional change rate (L(θ)) of the slow-axis direction of the first optical film (22) and the dimensional change rate (L(θ+90)) of the direction perpendicular thereto are adjusted so as to satisfy relations (1) and (2). Relation (1) 0.50 ≤ L(θ)/L(θ+90) ≤ 0.95 Relation (2) 0.1 (%) ≤ L(θ) ≤ 1.5 (%)

Description

Polarizing plate, manufacturing method of polarizing plate, liquid crystal display device, and organic electroluminescence display device

The present invention relates to a polarizing plate, a method for manufacturing a polarizing plate, a liquid crystal display device, and an organic electroluminescence display device. In particular, a polarizing plate comprising an obliquely stretched optical film, in which the occurrence of physical distortion is suppressed, a method for producing such a polarizing plate, and a liquid crystal display device comprising the polarizing plate, The present invention relates to an organic electroluminescence display device.

In recent years, the market for thin displays using liquid crystal displays and organic electroluminescence has been growing rapidly. In particular, the market for small and medium-sized mobile devices called smartphones and tablets is growing significantly.

Such a thin display has a polarizing plate. The polarizing plate generally has a structure in which a polarizer is sandwiched between two optical films.

As a method of manufacturing a polarizing plate, for example, a technique for manufacturing a circularly polarizing plate by using an optical film stretched in an oblique direction with respect to the width direction and bonding with a polarizer by a roll-to-roll method has been proposed. (For example, refer to Patent Document 1). The optical film is stretched in an oblique direction (hereinafter also referred to as “oblique stretching”) at a predetermined angle with respect to the width direction, thereby giving a desired phase difference. As such an optical film, a polycarbonate or a cycloolefin resin is preferably used, but it is also proposed to use a cellulose ester resin (see, for example, Patent Document 2).

However, when a polarizing plate is produced by laminating the above-described obliquely stretched optical film on a polarizer, physical distortion may occur in the polarizing plate depending on the usage environment of the polarizing plate. When physical distortion occurs in the polarizing plate, it is not preferable because physical distortion also occurs in a display device or the like on which the polarizing plate is mounted.

JP 2006-224618 A JP 2008-83307 A

The present invention has been made in view of the above-mentioned problems and situations, and the problem to be solved is a polarizing plate comprising an optical film stretched obliquely, and the polarizing plate in which the occurrence of physical distortion is suppressed, The manufacturing method of such a polarizing plate, and also providing a liquid crystal display device and an organic electroluminescent display device provided with the said polarizing plate.

As a result of investigating the cause of the above-mentioned problem in order to solve the above-mentioned problems according to the present invention, the polarizer, the first optical film disposed on one surface of the polarizer, and the other surface of the polarizer A second optical film disposed on the polarizing plate, wherein the crossing angle θ between the slow axis of the first optical film and the absorption axis of the polarizer is in the range of 30 to 60 °, The dimensional change rate L (θ) in the slow axis direction of the optical film 1 and the dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis were adjusted to satisfy a predetermined numerical range. The present inventors have found that a polarizing plate in which the occurrence of physical distortion is suppressed can be provided.
That is, the subject concerning this invention is solved by the following means.

1. A polarizing plate comprising: a polarizer; a first optical film provided to face one surface of the polarizer; and a second optical film provided to face the other surface of the polarizer. And
The crossing angle θ between the slow axis of the first optical film and the absorption axis of the polarizer is in the range of 30-60 °,
The dimensional change rate L (θ) in the slow axis direction of the first optical film and the dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis satisfy the following expressions (1) and (2). A polarizing plate characterized by being adjusted to.
Formula (1): 0.50 ≦ L (θ) / L (θ + 90) ≦ 0.95
Formula (2): 0.1 (%) ≦ L (θ) ≦ 1.5 (%)

2. The dimensional change rate L (MD) in the longitudinal direction of the first optical film and the dimensional change rate L (TD) in the width direction satisfy the following formula (3). Polarizer.
Formula (3): 0.50 ≦ L (MD) / L (TD) <1.00

3. The polarizing plate according to item 1 or 2, wherein the first optical film contains a polymer having a cellulose skeleton.

4. The retardation value Ro (550) in the in-plane direction at a wavelength of 550 nm of the first optical film is in a range of 75 to 150 nm, according to any one of items 1 to 3, The polarizing plate as described.

5. The polarizing plate according to any one of Items 1 to 4, wherein the first optical film contains cellulose acetate propionate.

6. The polarizing plate according to any one of items 1 to 5, wherein a slow axis of the second optical film and an absorption axis of the polarizer are parallel or orthogonal to each other.

7. The polarizing plate according to any one of Items 1 to 6, wherein the second optical film contains cellulose acetate or cellulose acetate propionate.

8. From the first item, a hard coat layer or an antiglare layer is provided on a surface on the viewing side of the optical film disposed on the viewing side of the first optical film and the second optical film. The polarizing plate according to any one of items up to 7.

9. A manufacturing method for manufacturing the polarizing plate according to any one of Items 1 to 8,
The manufacturing method of the polarizing plate characterized by having the bonding process which bonds the said polarizer, a said 1st optical film, and a said 2nd optical film by a roll to roll system.

10. A casting step of casting a dope on a support to form a casting film;
A transverse stretching step of stretching the cast film having a residual solvent amount of 1 to 20% by mass in the width direction at a stretching ratio of 1.01 to 1.3 times;
An oblique stretching step of stretching the casting film in an oblique direction with respect to the width direction;
A heat treatment step of obtaining the first optical film by performing the following heat treatment (i) or (ii) on the cast film,
The manufacturing method of the polarizing plate of Claim 9 which performs the said bonding process after the said heat processing process.
(I) The end of the cast film is embossed in the range of 180 to 220 ° C., and then wound in a roll shape, and the condition is 3 to 60 ° C. and 20% RH or less. Heat for ~ 5 days.
(Ii) The cast film is heat-treated at 140 to 170 ° C. for 40 to 600 seconds through the transport roller while transporting the cast film with a tension of 120 to 150 N by a transport roller.

11. A liquid crystal display device comprising the polarizing plate according to any one of items 1 to 8.

12. An organic electroluminescence display device comprising the polarizing plate according to any one of items 1 to 8.

According to the present invention, a polarizing plate comprising an obliquely stretched optical film, in which the occurrence of physical distortion is suppressed, a method for producing such a polarizing plate, and the polarizing plate are provided. A liquid crystal display device and an organic electroluminescence display device can be provided.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
In general, the dimensions of an optical film may change due to moisture absorption in an environment in which it is used, for example, in a high humidity environment. Here, in the case of an obliquely stretched optical film, the dimensional change rate in the width direction or the longitudinal direction is different from the dimensional change rate in the oblique direction. Specifically, the stretched optical film is stretched more than the dimensional change rate in the stretched direction. The dimensional change rate in the direction (width direction or longitudinal direction) that is not increased. Such characteristics tend to be observed in an optical film having a dimensional change rate in a stretching direction of a certain level or more, and is particularly remarkable when oblique stretching is performed at a high magnification. It is considered that physical distortion occurs in the polarizing plate due to the difference in the dimensional change rate in the surface direction of the optical film.
Therefore, the dimensional change rate in the slow axis direction of the first optical film and the dimensional change rate in the direction perpendicular to the slow axis satisfy the above formulas (1) and (2). The difference in the dimensional change rate in the surface direction of the optical film can be reduced, and it is considered that physical distortion can be suppressed by reducing the stress generated in the polarizing plate.

The top view which shows typically schematic structure of the manufacturing apparatus of the 1st optical film used for the polarizing plate of this invention. The top view which shows typically an example of the rail pattern of the extending | stretching part of the manufacturing apparatus shown in FIG. Sectional drawing which shows schematic structure of the liquid crystal display device of this invention Sectional drawing which shows schematic structure of the organic electroluminescence display of this invention

The polarizing plate of the present invention includes a polarizer, a first optical film provided to face one surface of the polarizer, and a second optical film provided to face the other surface of the polarizer. The crossing angle θ between the slow axis of the first optical film and the absorption axis of the polarizer is in the range of 30 to 60 °, and the slow phase of the first optical film The dimensional change rate L (θ) in the axial direction and the dimensional change rate L (θ + 90) in the direction orthogonal to the slow axis are adjusted so as to satisfy the expressions (1) and (2). . This feature is a technical feature common to or corresponding to each of claims 1 to 12.
Moreover, in this invention, it is preferable that the dimensional change rate L (MD) of the longitudinal direction of the said 1st optical film and the dimensional change rate L (TD) of the width direction satisfy | fill said Formula (3). Thereby, it can be set as the polarizing plate by which generation | occurrence | production of the surface failure and the planarity failure was suppressed.
In the present invention, the first optical film preferably contains a polymer having a cellulose skeleton. Thereby, the planarity of the first optical film can be improved, and the planarity of a polarizing plate using the first optical film can also be improved.
In the present invention, the retardation value Ro (550) in the in-plane direction at a wavelength of 550 nm of the first optical film is in the range of 75 to 150 nm. It is preferable from the viewpoint of visibility.
Moreover, in this invention, it is preferable from a viewpoint which suppresses generation | occurrence | production of the physical distortion of a polarizing plate that the said 1st optical film contains a cellulose acetate propionate.
In the present invention, it is preferable that the slow axis of the second optical film and the absorption axis of the polarizer are parallel or perpendicular to each other from the viewpoint that the roll-to-roll method can be manufactured inexpensively and with good flatness.
In the present invention, the second optical film contains cellulose acetate or cellulose acetate propionate, from the viewpoint of improving the visibility and ensuring the flatness of the display device equipped with the polarizing plate. To preferred. In addition, these resins can be films having a high retardation expression rate per film thickness and good visibility.
In the present invention, a hard coat layer or an antiglare layer may be provided on the viewing side of the optical film disposed on the viewing side of the first optical film and the second optical film. preferable. When a hard coat layer is provided, the surface of the polarizing plate can be protected, and when an antiglare layer is provided, the visibility of the reflected image is reduced and reflection of the reflected image is suppressed. can do.

Moreover, the manufacturing method of the polarizing plate of this invention is a manufacturing method of the said polarizing plate, Comprising: Pasting which bonds the said polarizer, a said 1st optical film, and a said 2nd optical film by a roll to roll system. It has a combination process.
Further, in the present invention, a casting process in which a dope is cast on a support to form a casting film, and the casting film having a residual solvent amount of 1 to 20% by mass is provided in the width direction by 1 A transverse stretching step of stretching at a draw ratio of 0.01 to 1.3 times, an oblique stretching step of stretching the cast film in an oblique direction with respect to the width direction, and the following ( further comprising a heat treatment step of obtaining the first optical film by performing the heat treatment of i) or (ii), and performing the bonding step after the heat treatment step. Is preferable in manufacturing.
(I) The end of the cast film is embossed in the range of 180 to 220 ° C., and then wound in a roll shape, and the condition is 3 to 60 ° C. and 20% RH or less. Heat for ~ 5 days.
(Ii) The cast film is heat-treated at 140 to 170 ° C. for 40 to 600 seconds through the transport roller while transporting the cast film with a tension of 120 to 150 N by a transport roller.

In addition, a liquid crystal display device of the present invention includes the polarizing plate.
In addition, an organic electroluminescence display device of the present invention includes the polarizing plate.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

"Polarizer"
The polarizing plate of the present invention includes a polarizer, a first optical film provided to face one surface of the polarizer, a second optical film provided to face the other surface of the polarizer, It has.
In addition, as will be described later, a functional layer such as a hard coat layer or an antiglare layer is provided on the surface on the viewing side of the optical film disposed on the viewing side of the first optical film and the second optical film. It is good as a thing. An adhesive layer may be provided between the polarizer and the first optical film and between the polarizer and the second optical film.
Hereinafter, each element which comprises the polarizing plate of this invention is demonstrated in detail.

[1] Polarizer A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a polarization plane in a certain direction to pass through. A typical known polarizer is a polyvinyl alcohol polarizing film. . The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

As the polarizer, a polyvinyl alcohol aqueous solution can be formed and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The thickness of the polarizer is preferably from 1 to 30 μm, more preferably from 1 to 20 μm, even more preferably from 1 to 15 μm, and even more preferably from 2 to 15 μm, from the viewpoint of thinning the polarizing plate.

Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has little color unevenness, and is particularly preferably used for a large liquid crystal display device.

Also, a coating type polarizer may be produced by the methods described in JP 2011-10081 A, JP 4691205 A, JP 4751481 A, and JP 4804589 A.

[2] First optical film The first optical film according to the present invention is provided to face one surface of the polarizer. Since the first optical film is stretched obliquely, the crossing angle θ between its slow axis and the absorption axis of the polarizer is in the range of 30 to 60 °. In addition, the first optical film has a dimensional change rate L (θ) in the slow axis direction and a dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis in the following formulas (1) and (2). It has been adjusted to meet.
Formula (1): 0.50 ≦ L (θ) / L (θ + 90) ≦ 0.95
Formula (2): 0.1 (%) ≦ L (θ) ≦ 1.5 (%)

In the optical film according to the present invention, the slow axis in the film plane is inclined with respect to the longitudinal direction (width direction), but in particular, the slow axis in the film plane is relative to the longitudinal direction (width direction). Thus, since it is within the range of 30 to 60 °, it is suitably provided in a circularly polarizing plate that converts linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light).

In order to produce a practical circularly polarizing plate, the optical film according to the present invention is preferably a λ / 4 plate. The λ / 4 plate is designed such that the in-plane retardation value Ro is about ¼ for a predetermined wavelength of light (usually in the visible light region). The λ / 4 plate has Ro (590) measured at a wavelength of 590 nm in the range of 120 to 160 nm.

“Retardation of approximately 1/4 in the wavelength range of visible light” means a retardation value represented by the following formula (A) measured at a wavelength of 450 nm, with a larger retardation at a wavelength of 400 to 700 nm. It is preferable that Ro (590) which is a retardation value measured at a certain Ro (450) and a wavelength of 590 nm satisfies 1 <Ro (590) / Ro (450) ≦ 1.6. Furthermore, it is preferable that 1 <Ro (590) / Ro (450) ≦ 1.3. In order to function effectively as a λ / 4 plate, Ro (450) is preferably in the range of 60 to 125 nm, and the retardation value Ro (550) measured at a wavelength of 550 nm is 75 to 150 nm. In particular, it is preferably in the range of 125 to 142 nm, and Ro (590) is preferably in the range of 130 to 152 nm.

In addition, Formula (B) is a formula for obtaining a retardation value Rt in the film thickness direction. The retardation value Rt measured at a wavelength of 550 nm is preferably in the range of 60 to 100 nm, and more preferably in the range of 70 to 90 nm.

Formula (A): Ro = (n _x −n _y ) × d
Formula (B): Rt = {(n _x + n _y ) / 2−n _z } × d
In the formula, nx, ny, and _nz are refractive indexes nx (maximum in-plane refractive index and refractive index in slow axis direction at 23 ° C. and 55% RH, 450 nm, 550 nm, and 590 nm, respectively. ), Ny (refractive index in the direction perpendicular to the slow axis in the film plane), _nz (refractive index in the film thickness direction), and d is the thickness (nm) of the film.

Ro and Rt can be measured using an automatic birefringence meter. Using an automatic birefringence meter KOBRA-21AWR (manufactured by Oji Scientific Instruments), Ro is calculated by measuring the birefringence at each wavelength in an environment of 23 ° C. and 55% RH.

A circularly polarizing plate is obtained by laminating so that the angle between the slow axis of the λ / 4 plate and the transmission axis (or absorption axis) of the polarizer is substantially 45 °. “Substantially 45 °” means a range of 40 to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizer is preferably in the range of 41 to 49 °, more preferably in the range of 42 to 48 °, and 43 to 47. A range of ° is more preferable, and a range of 44 to 46 ° is most preferable. Therefore, in order to produce a circularly polarizing plate by the roll-to-roll method, the direction of the slow axis of the optical film according to the present invention is preferably the above “substantially 45 °” direction.

The thickness of the first optical film according to the present invention is in the range of 15 to 50 μm and in the range of 20 to 40 μm because demand for thinner polarizing plates and display devices is increasing. More preferred. Within this range, an optical film that is thin and lightweight and has a stable winding shape can be obtained.

In consideration of productivity, the winding length in the optical film of the present invention is preferably in the range of 1500 to 8000 m, more preferably in the range of 2000 to 6000 m.

[2-1] Characteristics of the first optical film (surface roughness)
The arithmetic average roughness Ra of the surface of the first optical film according to the present invention is generally in the range of 1.3 to 4.0 nm, and preferably in the range of 1.6 to 3.5 nm.

(Fault tolerance)
In the first optical film according to the present invention, it is preferable that there are few failures in the film (hereinafter, also referred to as defects), and the defect referred to here means that when the film is formed by the solution casting method, It refers to voids (foaming defects) in the film caused by rapid evaporation of the solvent, foreign substances in the film-forming stock solution, and foreign substances (foreign substance defects) in the film caused by foreign substances mixed in the film formation.

Specifically, it is preferable that a defect having a diameter of 5 μm or more is 1 piece / 10 cm square or less in the film plane. More preferably, it is 0.5 piece / 10 cm square or less, and particularly preferably 0.1 piece / 10 cm square or less.

The diameter of the above defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

¡When the defect is a bubble or a foreign object, the defect range is measured by the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope. Further, when the defect is accompanied by a change in the surface shape, such as transfer of a roller scratch or an abrasion, the size is confirmed by observing the defect with reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation. In order to obtain a film excellent in the quality represented by such a defect frequency with high productivity, it is necessary to highly accurately filter the raw material solution of the optical film immediately before casting, to increase the cleanliness around the casting machine, It is also effective to set the drying conditions after casting stepwise and to dry efficiently while suppressing foaming.

If the number of defects is greater than 1/10 cm square, for example, if the film is tensioned during processing in a later step, the film may be broken starting from the defects and productivity may be reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

(Elongation at break)
In the optical film of the present invention, the elongation at break in at least one direction (TD direction or MD direction) is preferably 4% or more, more preferably 10% in the measurement based on JIS-K7127-1999. That's it.

The upper limit of the elongation at break is not particularly limited, but the elongation at break tends to decrease by performing stretching at a high stretching ratio, and pre-stretching is preferably performed in the TD direction as in the present invention. Thereafter, by performing oblique stretching, the breaking elongation is preferably 30% or less, and more preferably 20% or less.

(Total light transmittance)
The optical film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film. Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roller, calendar roller, drum, belt, coating substrate in solution casting, transport roller, etc.) during film formation. It is effective to reduce the diffusion and reflection of light on the film surface.

[2-2] Dimensional Change Rate of First Optical Film The dimensional change rate of the first optical film according to the present invention is measured by the following method.

[1] Two 10 cm squares of the first optical film are sampled so that one side is parallel to the TD direction or MD direction, and for measuring the dimensional change in the slow axis direction and the direction perpendicular to the slow axis direction, respectively. And In measuring the dimensional change of the distance between two points, two scratches were made on the cross with a razor in each of the slow axis direction and the direction perpendicular to the slow axis direction so that the distance between the films was 8 cm. After that, it is left for 24 hours in an environment of 23 ° C. and 20% RH.

The humidity-controlled film is placed on a microscope stage in the same environment of 23 ° C. and 20% RH, and a glass plate is placed on the film and fixed. The dimension (8 cm) between the two cross-shaped scratches is the slow axis. The direction and the direction perpendicular to the slow axis direction are measured precisely with a microscope, and are defined as L ₀ (θ) and L ₀ (θ + 90), respectively.

The microscope was Nikon MEASURESCOPE MM-11 (eyepiece: x10, objective lens: x3) manufactured by Nikon, and the data measuring machine was directly connected to the microscope using Nikon DP-302 DATA PROCESSOR. Output to spreadsheet software.

[2] The film was transferred to an environment of 23 ° C./80% RH and allowed to stand for 24 hours, and then the dimension between the two cross-shaped scratches was delayed under the environment of 23 ° C./80% RH temperature / humidity. axis direction, and were measured in a direction perpendicular to the slow axis direction by the microscope and data measuring instrument, L _{1 (theta),} respectively, and L 1 _(θ + 90).

[3] Substituting the respective dimensions obtained in [1] and [2] into the following (formula a) and (formula b) to obtain the dimensional change rate of the first optical film, and L (θ) and L ( θ + 90).
(Formula a): L (θ) (%) = (L ₁ (θ) −L ₀ (θ)) / L ₀ (θ) × 100
(Formula b): L (θ + 90) (%) = (L ₁ (θ + 90) −L ₀ (θ + 90)) / L ₀ (θ + 90) × 100

The present invention is characterized in that the dimensional change rates L (θ) and L (θ + 90) of the first optical film thus obtained satisfy the above formulas (1) and (2). Thereby, the difference of the dimensional change in the surface direction of a 1st optical film can be reduced, and generation | occurrence | production of a physical distortion can be suppressed.

The means for adjusting the dimensional change rate of the first optical film according to the present invention to the range represented by the above formulas (1) and (2) is not particularly limited, but the following means are adopted. It is possible to adjust by this.
That is, the cast film obtained by solution casting is stretched in the width direction, and further stretched in an oblique direction with respect to the width direction, and then in the range of 180 to 220 ° C. with respect to the end of the cast film. It is possible to adjust the rate of dimensional change by heat treatment for 3 to 5 days under conditions of 60 to 80 ° C and 20% RH or less after being embossed and wound in a roll. is there. Alternatively, after stretching in an oblique direction, the cast film is heated at 140 to 170 ° C. for 40 to 600 seconds through the transport roller while the cast film is transported at a tension of 120 to 150 N by the transport roller. The dimensional change rate can be adjusted.

In the first optical film, it is preferable that a dimensional change rate L (MD) in the longitudinal direction and a dimensional change rate L (TD) in the width direction satisfy the following formula (3). Thereby, it can be set as the polarizing plate by which generation | occurrence | production of the surface failure and the planarity failure was suppressed.
Formula (3): 0.50 ≦ L (MD) / L (TD) <1.00
The dimensional change rates L (MD) and L (TD) can be obtained by the same method as the measurement method described above.

[2-3] Composition of first optical film As a composition of the first optical film according to the present invention, the dimensional change rate of the first optical film satisfies the above formulas (1) and (2). Any known material may be used as long as it can be used, but it is preferable to contain a polymer having a cellulose skeleton (hereinafter also referred to as “cellulose derivative”). Preferably, the content ratio of the cellulose derivative in the first optical film is 55% by mass or more, preferably 70% by mass or more.

A cellulose derivative is a compound using cellulose as a raw material. Examples of cellulose derivatives include cellulose esters (details will be described later), cellulose ethers (for example, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, etc.), cellulose ether esters (for example, acetyl methyl cellulose, acetyl ethyl cellulose, acetyl hydroxy). Resins such as ethyl cellulose, benzoylhydroxypropyl cellulose, etc., cellulose carbonate (eg, cellulose ethyl carbonate, etc.), cellulose carbamate (eg, cellulose phenyl carbamate, etc.) are included, and cellulose esters are preferred. One type of cellulose derivative may be used, or a mixture of two or more types may be used.

The cellulose ester preferably has an acyl group having 2 to 4 carbon atoms. Examples of the acyl group having 2 to 4 carbon atoms include an acetyl group, a propionyl group, and a butanoyl group.

The β-1,4-bonded glucose unit constituting cellulose has free hydroxy groups at the 2nd, 3rd and 6th positions. The cellulose ester is a polymer obtained by acylating part or all of these hydroxy groups with an acyl group. The total acyl group substitution degree means the ratio in which all the hydroxy groups of cellulose located at the 2nd, 3rd and 6th positions are acylated per one glucose unit (100% acylation has a degree of substitution of 3). .

Examples of preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, Examples thereof include an isobutanoyl group, a tert-butanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group, particularly preferably A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms);

Specific cellulose esters include at least selected from cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, cellulose phthalate and cellulose acetate benzoate. One type is preferred.

Among these, more preferred cellulose esters are cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

The cellulose triacetate preferably has an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5%, and more preferably cellulose triacetate having an average degree of acetylation of 58.0 to 62.5%. is there.

Cellulose diacetate preferably has an average degree of acetylation (amount of bound acetic acid) of 51.0 to 56.0%. Commercially available products include L20, L30, L40, and L50 manufactured by Daicel Corporation, and Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S manufactured by Eastman Chemical Japan Co., Ltd. .

Cellulose acetate propionate or cellulose acetate butyrate has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group is Y Those satisfying the following formulas (I) and (II) are preferred.

Formula (I): 2.0 ≦ X + Y ≦ 2.95
Formula (II): 0 ≦ X ≦ 2.5
Among them, it is preferable that 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9.

The method for measuring the degree of substitution of the acyl group can be measured according to ASTM-D817-96.

The weight average molecular weight Mw of the cellulose ester is preferably in the range of 80000 to 300000, and more preferably in the range of 120,000 to 250,000, from the viewpoint of controlling the elastic modulus. Within the above range, it is easy to control the elastic modulus by stretching at the time of film formation, so that the winding shape of the film is stabilized and the anti-bleeding resistance of the additive is improved.

The number average molecular weight (Mn) of the cellulose ester is preferably in the range of 30000 to 150,000 because the obtained optical film has high mechanical strength. Furthermore, cellulose esters having a number average molecular weight of 40,000 to 100,000 are preferably used.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester is preferably in the range of 1.4 to 3.0.

The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 1000,000 to 500 13 calibration curves were used. Thirteen samples are used at approximately equal intervals.

The raw material cellulose of the cellulose ester used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

The cellulose ester according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic anhydride, etc.), and a catalyst (sulfuric acid, etc.). The reaction proceeds until the triester is formed. In the triester, the three hydroxy groups of the glucose unit are substituted with an organic acid acyl acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Subsequently, the cellulose triester is hydrolyzed to synthesize a cellulose ester having a desired degree of acyl substitution. Thereafter, the cellulose ester is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

The cellulose ester according to the present invention is charged with 1 g in 20 ml of pure water (electric conductivity of 0.1 μS / cm or less, pH 6.8), and has a pH of 6 to 6 when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. The electric conductivity is preferably in the range of 1 to 100 μS / cm.

The cellulose ester according to the present invention can be specifically synthesized with reference to the method described in JP-A-10-45804.

[2-4] Additive The first optical film may contain an additive. Examples of the additive include a plasticizer, an ultraviolet absorber, a retardation adjusting agent, an antioxidant, a deterioration preventing agent, a peeling aid, a surfactant, a dye, and fine particles. In the present embodiment, additives other than the fine particles may be added when preparing the solution of the cellulose ether or the like, or may be added when preparing the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to a polarizing plate used in an image display device such as an organic EL display.

These additives are preferably added in an amount of, for example, 1 to 30% by mass, preferably 1 to 20% by mass with respect to the cellulose ester. In order to suppress bleeding out during stretching and drying, a compound having a vapor pressure at 200 ° C. of 1400 Pa or less is preferable.

(Retardation adjuster)
As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in EP 91656A2 can be used.

Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

(Polymer or oligomer)
The first optical film comprises a cellulose ester and a vinyl compound having a substituent selected from a carboxy group, a hydroxy group, an amino group, an amide group, and a sulfo group and having a weight average molecular weight in the range of 500 to 200,000. It is preferable to contain these polymers or oligomers. The mass ratio of the content of the cellulose ester and the polymer or oligomer is preferably in the range of 95: 5 to 50:50.

(Matting agent)
The first optical film can contain fine particles as a matting agent. This makes it easier to transport and wind up when the first optical film is long.

The particle size of the matting agent is preferably primary particles or secondary particles of 10 nm to 0.1 μm. A substantially spherical matting agent having a primary particle acicular ratio of 1.1 or less is preferably used.

As the fine particles, those containing silicon are preferable, and silicon dioxide is particularly preferable. As the fine particles of silicon dioxide preferable for this embodiment, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) manufactured by Nippon Aerosil Co., Ltd. And commercially available products such as Aerosil 200V, R972, R972V, R974, R202, and R812 can be preferably used. Examples of the polymer fine particles include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. Examples include Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.). Can do.

(Other additives)
In addition, thermal stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. Further, a surfactant, a peeling accelerator, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like may be added.

[2-5] Method for Producing First Optical Film The method for producing the first optical film is not particularly limited. For example, a solution casting film forming method or a melt casting film forming method is used. be able to.
In addition, in the manufacturing method demonstrated below, a cellulose ester shall be used as a material of a 1st optical film.

[2-5-1] Method by the solution casting film forming method When the first optical film is produced by the solution casting film forming method, (1) each material such as cellulose ester and additives is dissolved in a solvent. A casting process in which the dope is cast on a support to form a casting film; (2) a casting film having a residual solvent amount of 1 to 20% by mass in a width direction of 1.01 to 1. Lateral stretching step of stretching at a stretching ratio of 3 times, (3) an oblique stretching step of stretching the cast film in an oblique direction with respect to the width direction, and (4) an after-mentioned (i) for the cast film. Or it can manufacture through the heat processing process of obtaining a 1st optical film by performing the heat processing of (ii).

[2-5-1-1] Casting step In a dissolution vessel, a cellulose ester and an additive are dissolved in a solvent to prepare a dope.

The solvent contained in the dope may be a single type or a combination of two or more types. From the viewpoint of increasing production efficiency, it is preferable to use a combination of a good solvent and a poor solvent for cellulose ester. A good solvent refers to a solvent that dissolves cellulose ester alone, and a poor solvent refers to a solvent that swells cellulose ester or does not dissolve alone. Therefore, the good solvent and the poor solvent differ depending on the average acyl group substitution degree of the cellulose ester.

Examples of good solvents include organic halogen compounds such as dichloromethane, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc., preferably dichloromethane.

Examples of poor solvents include methanol, ethanol, n-butanol, cyclohexane, and cyclohexanone. In order to suppress the bleeding of the additive in the optical film constituting the roll body, methanol or ethanol is preferable.

The poor solvent may be one type or a mixture of two or more types. When the poor solvent is a mixture of two or more kinds of poor solvents, the content ratio of the poor solvent having a large absolute value of the difference from the SP value (solubility parameter) of the additive is preferably the largest.

When a good solvent and a poor solvent are used in combination, it is preferable that the good solvent is more than the poor solvent in order to increase the solubility of the cellulose ester. The mixing ratio of the good solvent and the poor solvent is preferably in the range of 70 to 98% by mass for the good solvent and in the range of 2 to 30% by mass for the poor solvent.

The concentration of the cellulose ester in the dope is preferably higher in order to reduce the drying load, but it is difficult to filter if the concentration of the cellulose ester is too high. Therefore, the concentration of the cellulose ester in the dope is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 25% by mass.

Examples of the method for dissolving the cellulose ester in a solvent include a method for dissolving under heating and pressure, a method for adding a poor solvent to the cellulose ester to swell, a method for further adding a good solvent, and a cooling dissolution method, and the like. sell.

Among them, the method of dissolving under heating and pressurization is preferable because it can be heated to the boiling point or higher at normal pressure. Specifically, when stirring and dissolving while heating to a temperature that is higher than the boiling point of the solvent under normal pressure and that the solvent does not boil under pressure, generation of massive undissolved material called gel or mamako can be suppressed.

The heating temperature is preferably higher from the viewpoint of increasing the solubility of the cellulose ester, but if it is too high, it is necessary to increase the pressure and the productivity is lowered. For this reason, the heating temperature is preferably in the range of 45 to 120 ° C., more preferably in the range of 60 to 110 ° C., and still more preferably 70 to 105 ° C.

The obtained dope may contain insoluble matters such as impurities contained in the cellulose ester as a raw material. Such an insoluble matter can become a bright spot foreign material in the obtained film. In order to remove such insoluble matter and the like, it is preferable to further filter the obtained dope.

Next, the prepared dope is cast from the slit of the pressure die onto an endless metal support (for example, a stainless belt or a rotating metal drum).

The die is preferably a pressure die that can adjust the slit shape of the die part and easily adjust the film thickness uniformly. Examples of the pressure die include a coat hanger die and a T-die. The surface of the metal support is preferably mirror-finished.

Casting can also be performed by preparing a plurality of dopes and casting the plurality of dopes on a smooth band or drum as a support.

In this case, two or more kinds of dopes may be cast on the support at the same time, or separately on the support. In the case of the sequential casting method in which casting is performed separately, the dope on the support side can be cast first and dried to some extent on the support, and then overlaid on the support. When three or more kinds of dopes are used, a film having a laminated structure can be produced by appropriately combining simultaneous casting (also referred to as co-casting) and sequential casting. These methods, which are formed by co-casting or sequential casting, differ from the method of coating on a dried film, and the boundary of each layer of the laminated structure becomes unclear, and the laminated structure is clear by observing the cross section. There is a feature that there is a case where there is no separation, there is an effect of improving the adhesion between each layer.

As the co-casting, a known co-casting method can be used. For example, the film may be produced by casting and laminating a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the metal support. The methods described in JP-A Nos. 158414, 1-122419 and 11-198285 can be applied. Further, it may be formed into a film by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933.

Next, the dope film is heated on a metal support to evaporate the solvent to obtain a web (casting film).

The dope film is preferably dried in an atmosphere in the range of 40 to 100 ° C. In order to dry the dope film in an atmosphere in the range of 40 to 100 ° C., it is preferable to apply hot air in the range of 40 to 100 ° C. to the upper surface of the web or to heat it with infrared rays or the like.

As a method of evaporating the solvent, there are a method of applying air to the surface of the dope film, a method of transferring heat from the back side of the belt with a liquid, a method of transferring heat from the front and back by radiant heat, etc. A method of transferring heat from the back surface of the liquid with a liquid is preferable.

Next, the obtained web is peeled off at the peeling position on the metal support. The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C., more preferably in the range of 11 to 30 ° C.

From the viewpoint of improving the surface quality, moisture permeability, peelability and the like of the obtained web, it is preferable to peel the web from the metal support within 30 to 120 seconds after casting.

The residual solvent amount of the web when peeling at the peeling position on the metal support depends on the drying conditions and the length of the metal support, but is preferably in the range of 50 to 120% by mass. A web having a large amount of residual solvent is too soft and tends to impair flatness, and wrinkles and streaks in the casting direction (MD direction) due to peeling tension tend to occur. The residual solvent amount of the web at the peeling position can be set so that wrinkles and lines in the casting direction (MD direction) can be suppressed.
The amount of residual solvent in the web is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the sample collected before the web or film is stretched, and N is the mass after heating M at 115 ° C. for 1 hour.

The peeling tension when peeling the web from the metal support can usually be 300 N / m or less.

The web obtained by peeling from the metal support is dried. For drying the web, the web may be dried while being conveyed by a large number of rollers arranged vertically, or may be dried while being conveyed while fixing both ends of the web with clips.

The method of drying the web may be a method of drying with hot air, infrared rays, a heating roller, microwaves, or the like, and a method of drying with hot air is preferable because it is simple. The drying temperature of the web can be about 40 to 250 ° C., preferably about 40 to 160 ° C.

[2-5-1-2] Transverse Stretching Step Next, the web having a residual solvent amount of 1 to 20% by mass is stretched in the width direction (TD direction) within a range of a draw ratio of 1.01 to 1.3 times. ) Is carried out. The transverse stretching step is preferably performed continuously after the casting step, without winding up the obtained web.

An optical film having a desired retardation can be obtained by stretching the web. The retardation of the optical film can be controlled by adjusting the magnitude of the tension applied to the web.

The stretch ratio of the web is preferably in the range of 1.01 to 1.3 times, more preferably in the range of 1.07 to 1.15 times.

The stretching temperature of the web is preferably in the range of 120 to 200 ° C, more preferably in the range of 135 to 170 ° C.

The web stretching method is not particularly limited, and a tenter stretching method in which both ends of the web are fixed with clips or pins and the gap between the clips or pins is widened is preferable.

The amount of residual solvent in the web during the transverse stretching step is preferably in the range of 1 to 20% by mass, more preferably in the range of 3 to 20% by mass, and still more preferably in the range of 3 to 10% by mass. is there.

[2-5-1-3] Diagonal Stretching Step Next, an oblique stretching step of stretching a laterally stretched film (casting film) obtained by stretching in the width direction obliquely with respect to the film width direction. I do.

In order to further stretch the transversely stretched film stretched in the width direction, it is preferable to use an apparatus capable of oblique stretching. An apparatus capable of oblique stretching will be described.

(Outline of the device)
FIG. 1 is a plan view schematically showing an example of a schematic configuration of a manufacturing apparatus 1 capable of oblique stretching. The manufacturing apparatus 1 includes, in order from the upstream side in the transport direction of a long film, a film feeding unit 2, a transport direction changing unit 3, a guide roll 4, a stretching unit 5, a guide roll 6, and a transport direction changing unit 7. And a film cutting device 8 and a film winding unit 9. The details of the extending portion 5 will be described later. Moreover, it is good also as what performs the next process, without winding up an obliquely stretched film after an oblique stretch process, and the manufacturing apparatus 1 does not need to be provided with the film winding part 9 in this case. Moreover, when it is not necessary to cut | disconnect a long film, the manufacturing apparatus 1 does not need to be provided with the film cutting device 8. FIG.

The film feeding unit 2 feeds the long transversely stretched film (casting film) after being stretched in the width direction described above and supplies it to the stretching unit 5. The film feeding section 2 may be configured separately from the web film forming apparatus, or may be configured integrally. In the former case, the film is drawn out from the film feeding unit 2 by winding the film once on the core after film formation and loading the wound body (long film original fabric) into the film feeding unit 2. . On the other hand, in the latter case, after the film is formed, the film feeding unit 2 performs a lateral stretching process without winding the web, and further feeds the web to the stretching unit 5.

The conveyance direction changing unit 3 changes the conveyance direction of the film fed from the film feeding unit 2 to a direction toward the entrance of the stretching unit 5 as an oblique stretching tenter. Such a conveyance direction change part 3 is comprised including the turntable which rotates the turn bar which changes the conveyance direction by, for example, returning while conveying a film, and the turn bar in the surface parallel to a film.

By changing the film transport direction as described above in the transport direction changing section 3, the width of the entire manufacturing apparatus 1 can be made narrower, and the film feed position and angle can be finely controlled. This makes it possible to obtain a long obliquely stretched film with small variations in film thickness and optical value. Further, if the film feeding unit 2 and the conveyance direction changing unit 3 are movable (slidable and turnable), the right and left clips (gripping tools) sandwiching both ends of the long film in the width direction in the stretching unit 5 It is possible to effectively prevent the biting into the film.

In addition, the above-described film feeding unit 2 may be slidable and turnable so that a long film can be fed at a predetermined angle with respect to the entrance of the stretching unit 5. In this case, a configuration in which the installation of the conveyance direction changing unit 3 is omitted may be employed.

At least one guide roll 4 is provided on the upstream side of the stretching portion 5 in order to stabilize the track during film travel. The guide roll 4 may be composed of a pair of upper and lower rolls sandwiching the film, or may be composed of a plurality of roll pairs. The guide roll 4 closest to the entrance of the extending portion 5 is a driven roll that guides the travel of the film, and is rotatably supported via a bearing portion (not shown). A known material can be used as the material of the guide roll 4. In order to prevent the film from being damaged, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coat to the surface of the guide roll 4 or applying chrome plating to a light metal such as aluminum.

Further, it is preferable that one of the rolls upstream of the guide roll 4 closest to the entrance of the extending portion 5 is nipped by pressing the rubber roll. By setting it as such a nip roll, it becomes possible to suppress the fluctuation | variation of the drawing tension | tensile_strength in the flow direction of a film.

A pair of bearing portions at both ends (left and right) of the guide roll 4 closest to the entrance of the extending portion 5 includes a first tension detecting device as a film tension detecting device for detecting the tension generated in the film in the roll, A second tension detecting device is provided. For example, a load cell can be used as the film tension detection device. As the load cell, a known tensile or compression type can be used. A load cell is a device that detects a load acting on an applied point by converting it into an electrical signal using a strain gauge attached to the strain generating body.

The load cell is installed in the left and right bearing portions of the guide roll 4 closest to the entrance of the extending portion 5, so that the force of the running film on the roll, that is, in the film traveling direction generated in the vicinity of both side edges of the film. The tension is detected independently on the left and right. In addition, a strain gauge may be directly attached to a support that constitutes the bearing portion of the roll, and a load, that is, a film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension is measured in advance and is known.

When the position and the transport direction of the film supplied from the film feeding unit 2 or the transport direction changing unit 3 to the stretching unit 5 are deviated from the position toward the entrance of the stretching unit 5 and the transport direction, according to the amount of deviation, A difference will arise in the tension | tensile_strength near the both-sides edge of the film in the guide roll 4 nearest to the entrance of the extending | stretching part 5. FIG. Therefore, by providing the above-described film tension detecting device and detecting the above-described tension difference, the degree of the deviation can be determined. That is, if the transport position and transport direction of the film are appropriate (if it is the position and direction toward the entrance of the stretching unit 5), the load acting on the guide roll 4 is roughly uniform at both ends in the axial direction. If not appropriate, there will be a difference in film tension between left and right.

Therefore, the position and the transport direction of the film (angle with respect to the entrance of the stretching section 5) are adjusted by, for example, the transport direction changing section 3 described above so that the left and right film tension difference of the guide roll 4 closest to the entrance of the stretching section 5 becomes equal. When properly adjusted, the film can be stably held by the gripping tool at the entrance of the stretching portion 5, and the occurrence of obstacles such as detachment of the gripping tool can be reduced. Furthermore, the physical properties in the width direction of the film after oblique stretching by the stretching portion 5 can be stabilized.

At least one guide roll 6 is provided on the downstream side of the stretching portion 5 in order to stabilize the track during running of the film that is obliquely stretched in the stretching portion 5.

The transport direction changing unit 7 changes the transport direction of the stretched film transported from the stretching unit 5 to a direction toward the film winding unit 9.

Here, in order to cope with fine adjustment of the orientation angle (in-plane slow axis direction of the film) and product variations, the film traveling direction at the entrance of the stretching portion 5 and the film traveling direction at the exit of the stretching portion 5 It is necessary to adjust the angle between the two. In order to adjust the angle, the traveling direction of the formed film is changed by the transport direction changing unit 3 to guide the film to the inlet of the stretching unit 5 and / or the traveling direction of the film from the outlet of the stretching unit 5 Is changed by the transport direction changing unit 7 to return the film to the direction of the film winding unit 9.

Moreover, it is preferable from the viewpoint of productivity and yield that the film formation and oblique stretching are continuously performed. When the film forming process, the oblique stretching process, and the heat treatment process are continuously performed, the traveling direction of the film is changed by the transport direction changing unit 3 and / or the transport direction changing unit 7, and the film is formed by the film forming process and the heat treatment process. 1, that is, as shown in FIG. 1, the traveling direction of the film fed out from the film feeding portion 2 (feeding direction) and the traveling direction of the film immediately before being wound up by the film winding portion 9 ( The width of the entire apparatus with respect to the film traveling direction can be reduced by matching the winding direction.

Although the film traveling direction does not necessarily coincide in the film forming process and the heat treatment process, the transport direction changing unit 3 and the film feeding unit 2 and the film winding unit 9 are arranged so as not to interfere with each other. It is preferable to change the traveling direction of the film by the transport direction changing unit 7.

The transport direction changing units 3 and 7 as described above can be realized by a known method such as using an air flow roll or an air turn bar.

The film cutting device 8 cuts the film stretched by the stretching section 5 (long oblique stretched film) along the cross section including the width direction, and has a cutting member. The cutting member is composed of, for example, a scissor or a cutter (including a slitter, a strip-shaped blade (Thomson blade)), but is not limited thereto, and in addition, a rotating circular saw, a laser irradiation device, etc. It is also possible to configure.

The film take-up unit 9 takes up the film conveyed from the stretching unit 5 via the conveyance direction changing unit 7, and includes, for example, a winder device, an accumulator device, a drive device, and the like. It is preferable that the film winding unit 9 has a structure that can be slid in the horizontal direction in order to adjust the film winding position.

The film take-up unit 9 can finely control the film take-up position and angle so that the film can be taken at a predetermined angle with respect to the exit of the stretching unit 5. Thereby, it becomes possible to obtain a long obliquely stretched film with small variations in film thickness and optical value. In addition, it is possible to effectively prevent wrinkling of the film and to improve the winding property of the film, so that the film can be wound up in a long length.

The film take-up unit 9 constitutes a take-up unit that takes up the film stretched and transported by the stretch unit 5 with a constant tension. Note that a take-up roll for taking up the film with a constant tension may be provided between the stretching unit 5 and the film take-up unit 9. Moreover, you may give the function as said take-up roll to the guide roll 6 mentioned above.

In this embodiment, the take-up tension T (N / m) of the stretched film is preferably adjusted between 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. When the take-up tension is 100 N / m or less, sagging and wrinkles of the film are likely to occur, and the retardation and orientation angle profile in the film width direction are also deteriorated. On the other hand, when the take-up tension is 300 N / m or more, the variation of the orientation angle in the film width direction is deteriorated, and the width yield (taken efficiency in the width direction) is deteriorated.

In the present embodiment, it is preferable to control the fluctuation of the take-up tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the variation in the take-up tension T is ± 5% or more, variations in optical characteristics in the width direction and the flow direction (conveying direction) increase. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll (guide roll 6) on the outlet side of the stretching section 5, that is, the film tension is measured, and the value becomes constant. Thus, the method of controlling the rotational speed of the take-up roll or the take-up roll of the film take-up part 9 by a general PID control system is mentioned. Examples of the method for measuring the load include a method in which a load cell is attached to the bearing portion of the guide roll 6 and a load applied to the guide roll 6, that is, a film tension is measured. As the load cell, a known tensile type or compression type can be used.

The stretched film is released from the exit of the stretching section 5 after being gripped by the gripping tool of the stretching section 5, and both ends (both sides) of the film gripped by the gripping tool are trimmed as necessary. Then, the film is cut into a predetermined length by the film cutting device 8 and is wound up around a winding core (winding roll) sequentially to form a wound body of an obliquely stretched film.

(Details of stretched part)
Next, the detail of the extending | stretching part 5 mentioned above is demonstrated. FIG. 2 is a plan view schematically showing an example of the rail pattern of the extending portion 5. However, this is an example, and the configuration of the extending portion 5 is not limited to this.

In the present embodiment, the oblique stretching step is preferably performed using a tenter (an oblique stretching machine) capable of oblique stretching as the stretching portion 5. This tenter is an apparatus that heats a long film to an arbitrary temperature at which it can be stretched and obliquely stretches it. This tenter includes a heating zone Z, a pair of rails Ri and Ro on the left and right, and a number of gripping tools Ci and Co that travel along the rails Ri and Ro to convey a film (in FIG. 2, a set of gripping tools). Only). Details of the heating zone Z will be described later. Each of the rails Ri and Ro is configured by connecting a plurality of rail portions with connecting portions (white circles in FIG. 2 are examples of connecting portions). The gripping tool Ci / Co is composed of a clip that grips both ends of the film in the width direction.

In FIG. 2, the feeding direction D1 of the long film is different from the winding direction D2 of the stretched long diagonally stretched film, and forms a feeding angle θi with the winding direction D2. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

Thus, since the feeding direction D1 and the winding direction D2 are different, the rail pattern of the tenter has an asymmetric shape on the left and right. And a rail pattern can be adjusted now manually or automatically according to orientation angle (theta) given to the long diagonally stretched film which should be manufactured, a draw ratio, etc. FIG. In the oblique stretching machine used in the manufacturing method of the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions constituting the rails Ri and Ro can be freely set and the rail pattern can be arbitrarily changed.

In the present embodiment, the tenter gripping tool Ci · Co travels at a constant speed with a constant interval from the front and rear gripping tools Ci · Co. The traveling speed of the gripping tool Ci / Co can be selected as appropriate, but is usually 1 to 150 m / min. The difference in travel speed between the pair of left and right grippers Ci / Co is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed on the left and right of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the left and right grippers Ci / Co is substantially the same speed. Is required. In general tenter devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

In the oblique stretching machine used in the manufacturing method of the present embodiment, a high bending rate is often required for the rail that regulates the trajectory of the gripping tool, particularly at a location where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a curve at the bent portion.

As described above, the obliquely stretched tenter used for imparting oblique orientation to a long film can freely set the orientation angle of the film by variously changing the rail pattern, and further, the orientation axis of the film. It is preferable that the tenter be capable of orienting the (slow axis) horizontally and evenly with high precision across the film width direction and controlling the film thickness and retardation with high precision.

Next, the stretching operation in the stretching unit 5 will be described. Both ends of the long film are gripped by the left and right grippers Ci · Co, and are conveyed in the heating zone Z as the grippers Ci • Co travel. The left and right grips Ci / Co are opposed to a direction substantially perpendicular to the film traveling direction (feeding direction D1) at the entrance portion (position A in the drawing) of the extending portion 5, and are asymmetric rails. Each travels on Ri and Ro, and the film gripped at the exit portion (position B in the figure) at the end of stretching is released. The film released from the gripping tool Ci / Co is wound around the core by the film winding portion 9 described above. Each of the pair of rails Ri and Ro has an endless continuous track, and the grippers Ci and Co that have released the film at the exit portion of the tenter travel on the outer rail and sequentially return to the entrance portion. It is supposed to be.

At this time, since the rails Ri and Ro are asymmetrical in the left and right directions, in the example of FIG. 2, the left and right gripping tools Ci and Co, which are opposed to each other at the position A in the figure, move as the rails run on the rails Ri and Ro. The gripping tool Ci traveling on the Ri side (in-course side) has a positional relationship preceding the gripping tool Co traveling on the rail Ro side (out-course side).

That is, of the gripping tools Ci and Co that are opposed to the film feeding direction D1 at the position A in the figure, one gripping tool Ci is first in position B at the end of film stretching. When it reaches, the straight line connecting the gripping tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the film winding direction D2. With the above operation, the long film is obliquely stretched at an angle of θL with respect to the width direction. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

Next, the details of the heating zone Z will be described. The heating zone Z of the stretching section 5 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretching unit 5, the film gripped by the gripping tool Ci / Co passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order. In the present embodiment, the preheating zone Z1 and the stretching zone Z2 are separated by a partition, and the stretching zone Z2 and the heat fixing zone Z3 are separated by a partition.

The preheating zone Z1 refers to a section in which the gripping tool Ci / Co that grips both ends of the film travels at the left and right (in the film width direction) at a constant interval at the entrance of the heating zone Z.

The stretching zone Z2 refers to a section from when the gap between the gripping tools Ci and Co that grips both ends of the film opens until a predetermined gap is reached. At this time, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the transverse direction before and after the oblique stretching as necessary.

The heat setting zone Z3 refers to a section after the stretching zone Z2 in which the interval between the gripping tools Ci and Co is constant, and the gripping tools Ci and Co at both ends travel in parallel with each other. .

The stretched film passes through the heat setting zone Z3 and then passes through a section (cooling zone) in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the film. May be. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the interval between the gripping tools Ci and Co facing each other in advance may be used.

The temperature of the preheating zone Z1 is Tg to Tg + 30 ° C., the temperature of the stretching zone Z2 is Tg to Tg + 30 ° C., and the temperature of the heat setting zone Z3 and the cooling zone is Tg-30 to Tg + 20 ° C. with respect to the glass transition temperature Tg of the thermoplastic resin. It is preferable to set.

The lengths of the preheating zone Z1, the stretching zone Z2, and the heat setting zone Z3 can be appropriately selected. The length of the preheating zone Z1 is normally 100 to 150% of the length of the stretching zone Z2, and the length of the heat setting zone Z3. The length is usually 50 to 100%.

Further, when the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the draw ratio R (W / Wo) in the oblique stretching step is preferably 1.3 to 3. 0.0, more preferably 1.5 to 2.8. When the draw ratio is in this range, the thickness unevenness in the width direction of the film is preferably reduced. In the stretching zone Z2 of the oblique stretching tenter, if the stretching temperature is differentiated in the width direction, the thickness unevenness in the width direction can be further improved. In addition, said draw ratio R is equal to a magnification (W2 / W1) when the interval W1 between both ends of the clip held at the tenter inlet portion becomes the interval W2 at the tenter outlet portion.

Note that the method of oblique stretching in the stretching portion 5 is not limited to the above-described method. For example, the oblique stretching may be performed by simultaneous biaxial stretching as disclosed in JP-A-2008-23775. good. Note that simultaneous biaxial stretching means that both ends of the supplied long film in the width direction are gripped by each gripping tool, and the long film is transported while each gripping tool is moved, and the long film is transported. This is a method of stretching a long film in an oblique direction with respect to the width direction by making the moving speed of one gripping tool different from the moving speed of the other gripping tool while keeping the direction constant. In addition, oblique stretching may be performed by a method disclosed in JP2011-11434A.

In the long obliquely stretched film obtained by the oblique stretching step, the orientation angle θ is inclined in the range of, for example, greater than 0 ° and less than 90 ° with respect to the winding direction, and at a width of at least 1300 mm, It is preferable that the variation in the in-plane retardation Ro in the width direction is 10 nm or less and the variation in the orientation angle θ is 10 ° or less. Further, the in-plane retardation value Ro (550) of the long obliquely stretched film measured at a wavelength of 550 nm is preferably in the range of 60 to 220 nm, and more preferably in the range of 65 to 200 nm. More preferably, it is in the range of 75 to 150 nm.

That is, in the long obliquely stretched film obtained by the production method of the present embodiment, the variation of the in-plane retardation Ro is 2 nm or less and preferably 1 nm or less in at least 1300 mm in the width direction. By setting the variation of the in-plane retardation Ro within the above range, it is possible to improve the display quality when the long obliquely stretched film is used as a retardation film for a liquid crystal display device, for example.

Further, in the long obliquely stretched film obtained by the production method of the present embodiment, the variation in the orientation angle θ is preferably 10 ° or less, more preferably 5 ° or less, in at least 1300 mm in the width direction. Preferably, it is most preferably 1 ° or less. A long diagonally stretched film having a variation in the orientation angle θ exceeding 0.5 is bonded to a polarizer to form a circularly polarizing plate, and when this is installed in an image display device such as an organic EL display device, light leakage occurs, Contrast may be reduced.

The retardation value Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the plane perpendicular to the slow axis by the average thickness d of the film ( Ro = (nx−ny) × d).

The average thickness of the long obliquely stretched film obtained in the oblique stretching step is 20 to 60 μm, preferably 10 to 60 μm, more preferably 10 to 50 μm, particularly from the viewpoint of mechanical strength and thinning of the display device. The thickness is preferably 15 to 35 μm. Further, the thickness unevenness in the width direction of the long obliquely stretched film affects whether or not the film can be wound, and is preferably 3 μm or less, and more preferably 2 μm or less.

[2-5-1-4] Heat treatment step Next, the first optical film is obtained by performing the following heat treatment (i) or (ii) on the obliquely stretched obliquely stretched film (casting film). The heat treatment process to obtain is performed.
(I) After embossing in the range of 180 to 220 ° C. with respect to the end of the film after film formation and stretching, the cast film is wound up to form a roll body, which is 60 to 80 ° C., 20% Heat treatment for 3-5 days under conditions of RH or lower.
(Ii) The film after film formation and stretching is conveyed by a conveyance roller at a tension of 120 to 150 N, and the film is heat-treated at 140 to 170 ° C. for 40 to 600 seconds via the conveyance roller.

Thus, the film can be heat-corrected by fixing the film stretched obliquely in a wound state or in a tensioned state, whereby the film can be thermally corrected, and the slow axis direction of the first optical film The dimensional change rate L (θ) and the dimensional change rate L (θ + 90) in the direction orthogonal to the slow axis can be adjusted to values satisfying the above equations (1) and (2).
Hereinafter, the heat treatments (i) and (ii) will be described.

(Regarding (i) heat treatment)
In the heat treatment (i) above, first, embossing is performed in which embossed portions are provided at both ends in the width direction of the film obtained after oblique stretching. The embossed part is a constant film consisting of minute continuous irregularities on the film in order to prevent the back and front surfaces of the wound films from coming into close contact with each other before winding the long film. It has a width pattern. When one surface (for example, the upper surface) of the film is protruded in a convex shape, a relatively concave shape is formed on the other surface (for example, the lower surface) of the film corresponding to the convex shape.

In order to perform the embossing, it is preferable to use an embossing apparatus including an embossing roller and a back roller disposed opposite to the embossing roller via a film.

The roller diameter of the embossing roller is preferably in the range of 5 to 20 cm, and more preferably in the range of 6 to 15 cm. When the roller diameter of the embossing roller is more than 20 cm, the distance between the heat source (arranged inside the embossing roller) and the surface of the embossing roller is too large, and temperature unevenness may occur on the surface of the embossing roller. Therefore, a portion having a high elastic modulus and a portion having a low elastic modulus are generated in the embossed portion to be formed, and a portion having a low elastic modulus is easily crushed. On the other hand, if the roller diameter of the embossing roller is less than 5 cm, the rotation axis is likely to be shaken, and the height of the convex portions of the embossing formed tends to vary. The embossed part formed higher than the set height tends to be crushed.

The material of the back roller is preferably made of metal for the purpose of uniformly cooling the film on which the embossed portion is formed. As the metal type, for example, SUS, titanium, stainless steel, chrome plating, copper and the like are preferable. The metal back roller is easier to cool the film more uniformly than, for example, a rubber back roller, so that the cellulose ester is easily crystallized uniformly, and an embossed portion having high strength (high elastic modulus) is formed. Can do.

The clearance between the embossing roller and the back roller can be about 1 to 30 μm, preferably about 1 to 15 μm. The nip pressure between the embossing roller and the back roller can be about 100 to 10,000 Pa.

Then, both ends of the film in the width direction are nipped by the embossing roller and the back roller, and the both ends of the film in the width direction are embossed.

The surface temperature of the embossing roller is preferably in the range of 150 to 350 ° C, more preferably in the range of 160 to 300 ° C, and particularly preferably in the range of 180 to 220 ° C. If the surface temperature of the embossing roller is within the range of 150 to 350 ° C., the film can be sufficiently melted, and even when cooled, the cellulose ester can be sufficiently crystallized, and the embossed portion with high strength can be obtained. Easy to form. Moreover, the film does not melt too much, and sticking of the melt of the film to the embossing roller can be prevented.

In the production of the first optical film, when the embossed portions are formed by embossing rollers at both ends in the width direction of the film, a temperature difference within a range of 5 to 20 ° C. is applied to the surface temperature of the embossing rollers on both sides. It is preferable to form the embossed portion. Since the first optical film is stretched obliquely, there is anisotropy in the elastic modulus at both ends in the width direction of the film, so the difference in elastic modulus is canceled and the crush resistance of the convex portion of the embossed portion is made uniform. Therefore, an embossed portion is formed with a high-temperature embossing roller at the end portion having a low elastic modulus, and the embossing roller surface temperature is set at a low temperature within a range of 5 to 20 ° C. at the end portion having a high elastic modulus. It is preferable to form an embossed part with a roller. The surface temperature difference is more preferably in the range of 7 to 15 ° C.

The surface temperature of the back roller depends on the surface temperature of the embossing roller, but is preferably in the range of 30 to 100 ° C, more preferably in the range of 50 to 80 ° C. When the surface temperature of the back roller is in the range of 50 to 100 ° C., the film is not rapidly cooled, the cellulose ester is easily crystallized uniformly, and an embossed part having a high elastic modulus is obtained. In addition, the cellulose ester contained in the film can be easily cooled and crystallized, and the thermal expansion of the film can be suppressed to prevent undulation of the front and back surfaces of the film near the embossed portion. When the undulations on the front and back surfaces of the film near the embossed portion occur, the films are likely to stick to each other and the film is easily torn.

The film conveyance speed during embossing is preferably in the range of 50 to 120 m / min. When the film conveyance speed is in the range of 80 to 120 m / min, the productivity can be improved, and the pressure of the embossing roller and the heat of the embossing roller and the back roller can be easily transferred to the film, thereby being included in the film. A cellulose ester is crystallized uniformly, and an embossed part with high strength is obtained.

That is, in order to form an embossed portion that is not easily crushed, it is considered important to sufficiently melt the cellulose ester with an embossing roller, and slowly cool and crystallize the melted cellulose ester with a back roller. For that purpose, various combinations of at least two of (1) the surface temperature of the embossing roller, (2) the surface temperature of the back roller, (3) the roller diameter of the embossing roller, and (4) the material of the back roller are combined. It is preferable to adjust. Among them, (1) the surface temperature of the embossing roller and (2) the surface temperature of the back roller are preferably adjusted to the above-mentioned ranges, respectively, and (3) the embossing roller diameter is more preferably adjusted to the above-mentioned ranges. Furthermore, it is particularly preferable to select (4) the material of the back roller.

Subsequently, in the heat treatment of (i), after embossing is performed on the end of the film, the film is wound up in a roll shape at 60 to 80 ° C. under 20% RH for 3 to 5 days. Heat treatment.

The film can be wound using a winder.
The film winding method is not particularly limited, and for example, a constant torque method, a constant tension method, a taper tension method, or the like can be used.
The winding tension at the time of winding the film can be about 50 to 170N.

The period of the heat treatment may be appropriately determined depending on the set temperature. Usually, it is preferable to set the temperature relatively low so that the heat treatment effect at the outside of the winding, the center of the winding, and the core is not biased.

In order to carry out the heat treatment stably, it is preferably carried out in a place where the temperature and humidity can be adjusted, and preferably in a heat treatment chamber such as a clean room without dust.

The winding core for winding the antireflection film into a roll is not particularly limited as long as it is a cylindrical core, but is preferably a hollow plastic core, and the plastic material is a heat resistant plastic that can withstand heat treatment temperatures. For example, resins such as phenol resin, xylene resin, melamine resin, polyester resin, and epoxy resin can be used. A thermosetting resin reinforced with a filler such as glass fiber is preferred.

The number of turns around these winding cores is preferably 100 turns or more, more preferably 500 turns or more, and the winding thickness is preferably 5 cm or more.

Thus, when performing the heat treatment in a state of winding a long film, the roll is preferably rotated, and the rotation is preferably performed at a speed of 1 rotation or less per minute, and may be continuous or intermittent. Rotation may be possible. Moreover, it is preferable to perform rewinding of the roll once or more during the heating period.

It is preferable to provide a dedicated turntable in the heat treatment chamber in order to rotate the long film wound around the core during the heat treatment.

In the case of intermittent rotation, it is preferable that the stop time is within 10 hours, the stop position is preferably made uniform in the circumferential direction, and the stop time is within 10 minutes. More preferred. Most preferred is continuous rotation.

As for the rotation speed in continuous rotation, the time required for one rotation is preferably 10 hours or less, and if it is early, it becomes a burden on the apparatus, so the range of 15 minutes to 2 hours is preferable in practice.

In the case of a dedicated carriage having a rotation function, it is preferable that the optical film roll can be rotated during movement and storage. In this case, rotation is effective as a countermeasure against black bands that occur when the storage period is long. Function.

In addition, in the heat processing of (i), it is preferable to perform the said heat processing in the state which covered the film wound up in roll shape with the moisture proof sheet. That is, the film wound in a roll is wrapped with a resin film, preferably a moisture-proof sheet deposited with aluminum on the resin film, and then the winding shaft portion is fastened with a string or rubber band, and the above heat treatment is performed. Is preferred.
This makes it easy to maintain a humidity of 20% RH or less when heat-treating the film wound up in a roll shape, and further suppresses the occurrence of moisture absorption, foreign matter adhesion, and the like. It becomes possible to produce a high-quality first optical film.

As a specific example of the packaging form of the film, the entire peripheral surface and both axial end surfaces of the film wound in a roll shape on a cylindrical core are covered with a sheet-like packaging material, An example is an embodiment in which both ends in the roll circumferential direction are overlapped with each other, and a joining portion between the ends of the packaging material is fastened with a gum tape or the like. By such an aspect, there is substantially no gap in the contact portion between the end portions of the packaging material, and entry of dust or the like into the interior is prevented. When the end of the core protrudes outward from both ends in the axial direction of the roll film, the peripheral surface of the end and the both ends in the axial direction of the packaging material are fastened with strings, rubber bands, etc. A form that is hermetically sealed is preferred. It is better to use a form in which the core part is fastened with a string or a rubber band, etc., rather than fastening the left and right ends with gummed tape multiple times as in the past and making the inside substantially sealed without gaps It is a preferable embodiment in that the roll body can be appropriately absorbed and released during storage or transportation, and the optical characteristics and physical properties of the optical film are improved.

Examples of such packaging materials include films of polyolefin-based synthetic resins such as polyethylene and polypropylene, and films of polyester-based synthetic resins such as polyethylene terephthalate and polyethylene naphthalate. Further, the thickness of the packaging material is preferably 10 μm or more from the viewpoint of maintaining moisture permeability, and is preferably 100 μm or less from the viewpoint of handling such as rigidity. Moreover, since the moisture permeability of a packaging material changes with the thickness of the synthetic resin film which comprises a packaging material, the moisture permeability of a packaging material can be adjusted suitably by adjusting the thickness of a synthetic resin film.

Here, if the moisture permeability of this packaging material is 10 g / m ² or less per day as specified in JIS Z0208, it is possible to prevent the winding shape from being deteriorated and foreign matter failure, and to cause scratches due to it. Since it becomes difficult to produce, it is preferable.

In addition, in the packaging form of the roll body of the optical film of the present invention, the roll body of the optical film is packaged with a packaging material having a moisture permeability of 5 g / m ² or less per day specified by JIS Z 0208. Further, it is more preferable to package with a packaging material having a moisture permeability of 1 g / m ² or less. Thereby, deterioration at the time of storage in the physical distribution state such as storage and transportation of the film (deterioration of winding shape, occurrence of sticking failure between films and foreign matter failure) can be further suppressed.

In addition, as a packaging material whose moisture permeability per day prescribed | regulated by JISZ0208 is 5 g / m < ² > or less, thru | or 1 g / m < ² > or less, For example, polyolefin synthetic resin films, such as polyethylene and a polypropylene, and a polyethylene terephthalate And composite materials in which polyester synthetic resin films such as polyethylene naphthalate are laminated, and composite materials in which a metal such as aluminum is vapor-deposited or a thin film of metal is joined to these films. Is mentioned. The thickness of the packaging material made of these composite materials is preferably 1 μm or more from the viewpoint of maintaining moisture permeability, and is preferably 50 μm or less from the viewpoint of handling such as rigidity. And since the moisture permeability of a packaging material changes with the thickness of a composite material, the moisture permeability of a packaging material can be suitably adjusted by adjusting thickness.

In particular, composite materials in which polyolefin-based synthetic resin films such as polyethylene and polypropylene and polyester-based synthetic resin films such as polyethylene terephthalate and polyethylene naphthalate are laminated, and whether metal such as aluminum is deposited on these films. Alternatively, a composite material in which metal thin films are bonded and laminated can be particularly preferably used in terms of handling because high moisture permeation-preventing properties are obtained and the material is lightweight.

The above packaging material can exhibit the above effect by winding the roll of the optical film of the present invention at least once, but it may be wound twice or more.

By performing the heat treatment process in such a manner, the film is heat-corrected to reduce the dimensional change rate, and the dimensional change rate L (θ) in the slow axis direction and the dimensional change rate L in the direction perpendicular to the slow axis. A first optical film in which (θ + 90) satisfies the above formulas (1) and (2) can be obtained.

(Regarding heat treatment of (ii))
In the heat treatment (ii), the film obtained after oblique stretching is applied for 40 to 600 seconds through 300 to 600 conveying rollers while applying a tension of 120 to 150 N under a temperature condition of 140 to 170 ° C. Heat treatment while transporting.

The heat treatment (ii) may be performed by any apparatus as long as the apparatus has a transport roller group capable of stretching the film with the tension and heating the film in the temperature range. For example, the heat treatment is preferably performed using an apparatus having 300 to 600 conveying rollers.

By performing the heat treatment process in such a manner, the film is heat-corrected and the dimensional change rate is reduced. Thus, the first optical film in which the dimensional change rate L (θ) in the slow axis direction and the dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis satisfy the above formulas (1) and (2). Obtainable.

[2-5-2] Method by Melt Casting Film Forming Method When the first optical film is produced by the melt casting film forming method, a composition containing an additive such as a resin and a plasticizer is used. Then, the mixture is heated and melted to a temperature exhibiting the following, and then a melt containing a flowable cellulose ester is cast.

More specifically, the heat melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these molding methods, the melt extrusion method is preferable from the viewpoint of mechanical strength and surface accuracy. The plurality of raw materials used in the melt extrusion method are usually preferably kneaded and pelletized in advance.

A known method can be applied to pelletization, for example, dry cellulose acylate, plasticizer, and other additives are fed to an extruder with a feeder, and kneaded using a single or twin screw extruder, It can be obtained by extruding in a strand form from a die, cooling with water or air, and cutting.

The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of additives such as fine particles and antioxidants are preferably mixed in advance in order to mix uniformly.

The extruder used for pelletization preferably has a method of processing at as low a temperature as possible so that pelletization is possible so that the shear force is suppressed and the resin does not deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. Of course, the raw material powder can be put into a feeder as it is, supplied to an extruder, heated and melted, and then directly formed into a film without being pelletized.

The pellets are extruded using a single or twin screw type extruder and the melting temperature is within the range of 200 to 300 ° C. After removing foreign matter by filtering with a leaf disk type filter or the like, from the T-die The film is cast into a film, and the film is nipped with a cooling roller and an elastic touch roller, and solidified on the cooling roller.

When introducing into the extruder from the supply hopper, it is preferable to carry out under vacuum or reduced pressure or in an inert gas atmosphere to prevent oxidative decomposition and the like.

The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. Stainless steel fiber sintered filter is made by compressing the stainless fiber body in a complicatedly intertwined state, and sintering and integrating the contact points. The density is changed according to the thickness and compression amount of the fiber, and the filter is filtered. The accuracy can be adjusted.

Additives such as plasticizers and fine particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

The film temperature on the touch roller side when the film is nipped by the cooling roller and the elastic touch roller is preferably in the range of Tg or more and Tg + 110 ° C. or less of the film. A known elastic touch roller can be used as the elastic touch roller having an elastic surface used for such a purpose. The elastic touch roller is also called a pinching rotary body, and a commercially available one can also be used.

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

In addition, the film obtained as described above passes through the step of contacting the cooling roller, and is then subjected to stretching treatment by the transverse stretching step and the oblique stretching step.

As the stretching method, a known roller stretching machine or tenter can be preferably used. The stretching temperature is usually preferably in the temperature range of Tg to (Tg + 60) ° C. of the resin constituting the film.

[3] Second optical film The second optical film according to the present invention is provided to face the other surface of the polarizer. The second optical film is preferably stretched in the longitudinal direction or the width direction, and its slow axis and the absorption axis of the polarizer are preferably parallel or orthogonal.

As the material of the second optical film, the same material as that of the first optical film can be used, and the description thereof will be omitted. In particular, cellulose acetate or cellulose acetate propionate is preferable.

Since matters other than those described above are the same as those of the first optical film, description thereof will be omitted.

[4] Other constituent layers The polarizing plate may include a functional layer on the surface of the optical film disposed on the viewing side of the first optical film and the second optical film. As the functional layer, for example, a hard coat layer made of an ultraviolet curable resin or the like, or an antiglare layer is provided.
Examples of the hard coat layer or antiglare layer used as the functional layer include a hard coat layer described in JP-A No. 2003-114333, JP-A No. 2004-203090, 2004-354699, and No. 2004-354828. An antiglare layer can be used.

[4-1] Hard coat layer The hard coat layer preferably contains a cured product of an actinic radiation curable compound, and the actinic radiation curable compound includes a component containing a monomer having an ethylenically unsaturated double bond. Preferably used. Examples of the actinic radiation curable compound include an ultraviolet curable compound and an electron beam curable compound, and a compound that is cured by ultraviolet irradiation is preferable from the viewpoint of excellent mechanical film strength (abrasion resistance, pencil hardness).

As the ultraviolet curable compound, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. Of these, ultraviolet curable acrylate resins are preferred.

The dry thickness of the hard coat layer is an average layer thickness of 0.01 to 20 μm, preferably 0.5 to 10 μm. More preferably, it is in the range of 0.5 to 5 μm.

As the method for applying the hard coat layer, known methods such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, and an ink jet method can be used. After applying the hard coat layer composition, it is dried, irradiated with active rays (also referred to as UV curing treatment)) and cured, and if necessary, it may be heat treated after curing.

[4-2] Antiglare layer The antiglare layer is a layer that blurs the outline of the image reflected on the surface of the film substrate and the outside light. When using an image display device such as a liquid crystal display, organic EL display, plasma display, etc. It is a functional layer that prevents reflection of light and reflected images. The antiglare layer may also serve as a hard coat layer.

The antiglare layer is preferably formed by adding and dispersing the following fine particles in the actinic radiation curable resin used for the hard coat layer. Examples of the fine particles include fine particles such as inorganic fine particles and organic fine particles. Examples of the inorganic fine particles include silicon oxide, magnesium oxide, and calcium carbonate. Examples of the organic particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, polystyrene resin powder, and melamine resin powder.

The arithmetic average roughness Ra (JIS B0601: 1994) of the antiglare layer is preferably in the range of 0.3 to 1.5 μm from the viewpoint of imparting antiglare properties, and more preferably 0.35 to 1.3 μm. And particularly preferably in the range of 0.5 to 1.3 μm. Within the above range, the antiglare property and the slipperiness of the antiglare layer are satisfied, and an antiglare layer having a high hardness (4H or more) can be obtained even with a thin film.

<< Polarizing plate manufacturing method >>
In the optical film according to the first aspect of the present invention, the angle θ between the slow axis and the absorption axis of the polarizer is in the range of 30 to 60 ° by being obliquely stretched, and the transmission axis (or absorption axis) is long. A long polarizing plate can be formed by laminating with a long polarizer in a direction with a roll to roll.

In the heat treatment step of the first optical film, when performing the heat treatment (ii), the method for producing a polarizing plate of the present invention further includes a step of removing the embossed portion of the first optical film. It is preferable.

In the polarizing plate, the polarizer is preferably sandwiched between the first optical film and the second optical film according to the present invention.
The bonding of the optical film and the polarizer is not particularly limited, but can be performed using a completely saponified polyvinyl alcohol adhesive after saponifying the optical film. Moreover, although it can also bond together using an active energy ray hardening adhesive etc., a photocurable adhesive is used from the point etc. which the elasticity modulus of the adhesive layer obtained is high and it is easy to suppress a deformation | transformation of a polarizing plate. It is preferable that they are bonded.

Preferred examples of the photocurable adhesive include (α) cationic polymerizable compound, (β) photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm, as disclosed in JP 2011-08234 A. And a photo-curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other photocurable adhesives may be used.

Hereinafter, an example of a method for producing a polarizing plate using a photocurable adhesive will be described. The polarizing plate includes (1) a pretreatment step for easily adhering the surface of the optical film to which the polarizer is bonded, and (2) at least one of the adhesive surfaces of the polarizer and the optical film. (3) a bonding step of bonding the polarizer and the optical film through the obtained adhesive layer, and (4) a polarizer and the optical film through the adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in the bonded state. What is necessary is just to implement the pre-processing process of (1) as needed.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the adhesive surface of the optical film with the polarizer. When bonding an optical film to both surfaces of a polarizer, easy adhesion processing is performed on the bonding surface of each optical film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When the photocurable adhesive is directly applied to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(Bonding process)
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, an optical film is superimposed thereon. When a photocurable adhesive is applied to the surface of the optical film in the previous application step, a polarizer is superimposed thereon. In addition, when a photocurable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In the case where the optical film is bonded to both surfaces of the polarizer, and the photocurable adhesive is used on both surfaces, the optical film is superimposed on the both surfaces of the polarizer via the photocurable adhesive. In this state, the pressure is usually sandwiched between rolls from both sides. As the material of the roll, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer containing the epoxy compound or the oxetane compound. Thereby, the overlapped polarizer and the optical film are bonded via the photocurable adhesive. In order to paste the optical film on both sides of the polarizer, the active energy rays are irradiated from either one of the optical films while the optical films are superimposed on both sides of the polarizer via a photocurable adhesive. It is advantageous to simultaneously cure the photocurable adhesive on both sides.

As the active energy rays, visible rays, ultraviolet rays, X-rays, electron beams and the like can be used, and since they are easy to handle and have a sufficient curing rate, electron beams or ultraviolet rays are generally preferably used.

Any appropriate conditions can be adopted as the electron beam irradiation conditions as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, There is a risk of damaging the polarizer. The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent optical film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can cure | harden the said adhesive agent. Preferably the dose of ultraviolet rays in the range of 50 ~ 1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 ~ 500mJ / cm ^2.

In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, and preferably in the range of 0.5 to 5 μm.

<Liquid crystal display device>
FIG. 3 is a cross-sectional view showing a schematic configuration of the liquid crystal display device 10 of the present embodiment. The liquid crystal display device 10 includes a liquid crystal cell 11, a polarizing plate 12 disposed on the viewing side with respect to the liquid crystal cell 11, a polarizing plate 13 disposed on the side opposite to the viewing side with respect to the liquid crystal cell 11, and a polarization The backlight 14 arrange | positioned on the opposite side to the visual recognition side with respect to the board 13 and the front board 15 arrange | positioned with respect to the polarizing plate 12 at the visual recognition side are provided. The liquid crystal cell 11 is configured by sandwiching a liquid crystal layer between a pair of substrates. The liquid crystal cell 11 has a plurality of pixels arranged in a matrix, and performs display by turning on / off each pixel by a switching element such as a TFT (Thin Film Transistor).

The front plate 15 serves as an exterior cover of the liquid crystal display device 10 and is a transparent substrate made of glass or resin (for example, acrylic) or a touch panel module. It is preferable that a filler (not shown) made of, for example, an ultraviolet curable resin is filled between the front plate 15 and the polarizing plate 12. By providing the filler, an air layer is prevented from being formed between the front plate 15 and the polarizing plate 12, and the interface between the front plate 15 and the air layer and between the polarizing plate 12 and the air layer are prevented. It is possible to improve the visibility of the display image by suppressing reflection of light at the interface.

As the polarizing plate 12, the polarizing plate of the present invention described above is used, and a polarizer 21 that transmits predetermined linearly polarized light, and a first side that is disposed on the viewing side with respect to the polarizer 21 via an adhesive layer or the like. It has the optical film 22 and the functional layer 23 arrange | positioned at the visual recognition side further. The functional layer 23 is composed of, for example, a hard coat layer made of an ultraviolet curable resin or an antiglare layer. Further, the polarizing plate 12 has a second optical film 24 disposed on the liquid crystal cell 11 side with respect to the polarizer 21 via an adhesive layer or the like.

The polarizer 21 is obtained, for example, by staining a polyvinyl alcohol film with a dichroic dye and stretching the film at a high magnification. After the polarizer 21 is subjected to alkali treatment (also referred to as saponification treatment), the first optical film 22 is bonded to one surface side through an adhesive layer or the like, and the second optical surface is bonded to the other surface side. The film 24 is bonded through an adhesive layer or the like.

The adhesive layer is, for example, a layer made of a polyvinyl alcohol adhesive (PVA adhesive, water glue), but may be a layer made of an ultraviolet curable adhesive (UV adhesive). These adhesives are liquid in a state where they are applied to an adhesive surface, and are bonded to each other by being dried or cured by ultraviolet irradiation after application. That is, the adhesive layer bonds the polarizer 21 and the first optical film 22, and the polarizer 21 and the second optical film 24, respectively, according to the state change from the liquid state. In this way, the adhesive layer is an adhesive layer (a sheet having an adhesive on the base material) that adheres the two without causing such a change in the state of bonding the two by a change in state from the liquid state. The adhesive layer).
The thickness of the adhesive layer is preferably in the range of more than 0.1 μm and not more than 5 μm. In this case, the polarizing plate 12 can be easily made thinner as compared with a configuration using an acrylic pressure-sensitive adhesive (thickness of about 10 μm).

The first optical film 22 is a layer that imparts an in-plane retardation of about ¼ of the wavelength to transmitted light, and is composed of a cellulose ester film having a thickness of 20 to 60 μm that is obliquely stretched. It is preferable. The angle (crossing angle) θ formed between the slow axis of the first optical film 22 and the absorption axis of the polarizer 21 is in the range of 30 to 60 °, whereby linearly polarized light from the polarizer 21 is It is converted into circularly polarized light or elliptically polarized light by the first optical film 22.

When the functional layer 23 is composed of a hard coat layer, the surface of the polarizing plate 12 can be protected by the hard coat layer. The hard coat layer may contain an organic compound having an ultraviolet absorbing function. As such an organic compound (organic UV absorber), for example, Tinuvin 928 (manufactured by BASF Japan Ltd.) can be used.

The second optical film 24 is a cellulose ester film having a thickness of 20 to 60 μm, and is provided as a film for protecting the back side of the polarizer 21. Note that the second optical film 24 may be provided as an optical film that also serves as a retardation film having a desired optical compensation function.

The polarizing plate 13 includes a polarizer 31 that transmits predetermined linearly polarized light, an optical film 32 that is disposed on the viewing side (liquid crystal cell 11 side) with respect to the polarizer 31 via an adhesive layer, and a polarizer 31. On the other hand, the optical film 33 is disposed on the opposite side (backlight side) to the viewing side via an adhesive layer. The polarizers 21 and 31 are arranged so as to be in a crossed Nicols state. In addition, as a constituent material of the polarizer 31 and the optical films 32 and 33, the same thing as the polarizer 21 and the 2nd optical film 24 can be used, respectively.

As described above, in the polarizing plate 12 on the viewing side, the first optical film 22 and the second optical film 24 located on both sides of the polarizer 21 are both cellulose esters composed of a thin film having a thickness of 20 to 60 μm. Since the first optical film 22 that is obliquely stretched is disposed on the viewing side of the polarizer 21 that is a film, the first optical film 22 and the second optical film 24 absorb it. Warpage of the polarizing plate 12 due to variation in moisture can be effectively suppressed.

Moreover, since the hard coat layer or the anti-glare layer is provided as the functional layer 23 on the viewing side with respect to the first optical film 22, the surface of the polarizing plate 12 can be protected by this functional layer 23, or the antiglare function. Can be demonstrated.

In addition, the easily bonding layer for improving the adhesiveness of the 1st optical film 22 may be provided in the surface at the side of the polarizer 21 of the 1st optical film 22. FIG. The easy adhesion layer is formed by performing an easy adhesion process on the surface of the first optical film 22. The easy adhesion treatment includes corona (discharge) treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment, etc., and at least one of them may be performed. Among these easy adhesion treatments, from the viewpoint of productivity, corona treatment and plasma treatment are preferable as the easy adhesion treatment.

In the polarizing plate 12, an overcoat layer may be formed on the functional layer 23. The overcoat layer is preferably composed of an active energy ray curable resin (for example, an ultraviolet curable resin) similar to the hard coat layer described above. Thus, by providing an overcoat layer on the functional layer 23, the surface of the functional layer 23 can be protected.

If both the overcoat layer and the functional layer 23 are hard coat layers, two hard coat layers are formed on one side of the first optical film 22, so that the surface protection of the polarizing plate 12 is ensured. Can be aimed at. Further, the overcoat layer may be composed of a hard coat layer that does not substantially contain an organic compound having an ultraviolet absorbing function or has a content (mass%) of an organic compound having an ultraviolet absorbing function that is smaller than that of the functional layer 23. preferable. In this case, it is possible to further suppress the elution of an organic compound having an ultraviolet absorption function contained in the functional layer 23 to the outside.

<< Organic EL display device >>
FIG. 4 is a cross-sectional view showing a schematic configuration of the organic EL display device 50 of the present embodiment. The organic EL display device 50 includes an organic EL light emitting element 51, a polarizing plate 52 disposed on the viewing side with respect to the organic EL light emitting element 51, a front plate 53 disposed on the viewing side with respect to the polarizing plate 52, It has. The organic EL light emitting element 51 has a metal electrode, a TFT, an organic light emitting layer, a transparent electrode (ITO, etc.), an insulating layer, and a sealing layer in this order on a substrate using glass, polyimide, or the like.

The polarizing plate 52 and the front plate 53 are configured in the same manner as the polarizing plate 12 and the front plate 15 of the liquid crystal display device 10 described above. However, in the organic EL display device 50, the first polarizing plate 52 includes the first polarizing plate 52. The optical film 62 is disposed closer to the organic EL light emitting element 51 than the polarizer 61, and the second optical film 64 is disposed closer to the viewing side than the polarizer 61. Further, the configuration is different from the liquid crystal display device 10 in that the functional layer 63 is disposed on the viewing side of the second optical film 64.

Generally, an organic EL display device includes an element (organic EL element) that is a light emitter by sequentially laminating a metal electrode, an organic light emitting layer, and a transparent electrode on a transparent substrate. Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, various combinations of structures such as a laminate of such a light-emitting layer and an electron injection layer made of a perylene derivative, or a stack of these hole injection layer, light-emitting layer, and electron injection layer are known. Yes.

In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the fluorescent material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

In an organic EL display device, in order to take out light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent, and is usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO). Is preferably used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

The polarizing plate of the present invention can be applied to an organic EL display device composed of a large screen having a screen size of 20 inches or more, that is, a diagonal distance of 50.8 cm or more.

In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL image display device looks like a mirror surface.

In an organic EL display device including an organic EL element having a transparent electrode on the surface side of an organic light emitting layer that emits light when a voltage is applied and a metal electrode on the back surface side of the organic light emitting layer, the surface side of the transparent electrode (visible) By providing a circularly polarizing plate on the side), light passing through it is transmitted through the transparent substrate, transparent electrode, and organic thin film, reflected by the metal electrode, and again transmitted through the organic thin film, transparent electrode, and transparent substrate. Since it becomes linearly polarized light again by the circularly polarizing plate, this linearly polarized light is orthogonal to the polarization direction of the polarizing plate and cannot pass through the polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

[Example 1]
<< Production of Polarizing Plate 101 >>
<Production of first optical film>
A first optical film (λ / 4 film) made of a cellulose ester film was produced according to the following method.

(Preparation of fine particle dispersion)
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

(Preparation of fine particle additive solution)
Based on the following composition, the fine particle dispersion was slowly added to a dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by 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 additive solution.
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion

(Main dope)
A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate was added to a pressurized dissolution tank containing a solvent while stirring. While this was heated and stirred, it was completely dissolved, and this was dissolved in Azumi Filter Paper No. The main dope was prepared by filtration using 244. In addition, the compound synthesize | combined by the following synthesis examples was used for the following sugar ester and the following polyester.

<Composition of main dope>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.50, propionyl group substitution degree 0.90, total substitution degree 2.40, weight average molecular weight 220,000) (CAP) 100 parts by mass Sugar ester 5.0 parts by weight Polyester 5.0 parts by weight Particulate additive solution 1 part by weight

(Synthesis of sugar esters)
A sugar ester was synthesized by the following steps.

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off.

Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture (sugar ester) of A-1, A-2, A-3, A-4 and A-5 was obtained.

The obtained mixture was analyzed by HPLC and LC-MASS. As a result, A-1 was 1.3% by mass, A-2 was 13.4% by mass, A-3 was 13.1% by mass, and A-4 was 31% by mass. 0.7% by mass and A-5 was 40.5% by mass. The average degree of substitution was 5.5.

(Measurement conditions for HPLC-MS)
1) LC section Equipment: Column oven (JASCO CO-965) manufactured by JASCO Corporation, detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

(Synthesis of polyester)
Polyester was synthesized by the following steps.

251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with thermometer, stirrer, and slow cooling tube The flask is charged and gradually heated with stirring until it reaches 230 ° C. in a nitrogen stream. After dehydration condensation for 15 hours, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. after completion of the reaction to obtain a polyester. Polyester has an ester of benzoic acid at the end of a polyester chain formed by condensation of 1,2-propylene glycol, phthalic anhydride and adipic acid. The acid value of the polyester was 0.10, and the number average molecular weight was 450.

(Production of long film)
Then, using an endless belt casting apparatus, it was cast uniformly on a stainless belt support.

In the endless belt casting apparatus, the main dope was uniformly cast on a stainless steel belt support. On the stainless steel belt support, the solvent in the cast (long cast) long film was evaporated and peeled off from the stainless steel belt support (casting process). The obtained film was dried to have a residual solvent amount of 10% by mass, and then stretched at a stretching ratio of 1.15 times the original width in the width direction at 170 ° C. using a tenter (horizontal Stretching step).

Thereafter, the long film is obliquely stretched at a stretching temperature of 185 ° C. and a stretching ratio of 1.7 times so that the orientation angle θ is 45 ° using the manufacturing apparatus shown in FIG. A stretched film was produced (oblique stretching step).

Furthermore, the heat treatment step was performed by performing the heat treatment (i) or (ii) described above.

When the heat treatment of (i) is performed, the end of the produced film is embossed within a range of 180 to 220 ° C., and then wound in a roll shape at 60 to 80 ° C., Heat treatment for 3-5 days under 20% RH or less.
In Table 1, heat treatment (i) -1 is embossed at 220 ° C., and the film wound up in a roll is covered with a moisture-proof sheet in three layers, and heated at 60 ° C. and 20% RH for 3 days. It is something to process. In the heat treatment (i) -2, embossing is performed at 180 ° C., the film wound up in a roll shape is covered with a moisture-proof sheet twice, and is heat-treated at 80 ° C. and 5% RH for 5 days. Is. In the heat treatment (i) -3, embossing is performed at 170 ° C., the film wound in a roll is covered with a moisture-proof sheet and covered with a moisture-proof sheet, and heat-treated at 50 ° C. and 20% RH for 2 days. (Comparative example).
In addition, as a moisture-proof sheet | seat, the film by which aluminum was vapor-deposited on the 30-micrometer-thick polyethylene resin film was used.

In the case of performing the heat treatment (ii), the film is heated at 140 to 170 ° C. for 40 to 600 seconds through the conveyance roller while the produced film is conveyed at a tension of 120 to 150 N by the conveyance roller.
In Table 1, heat treatment (ii) -1 is one in which the film is heated at 140 ° C. for 600 seconds while being transported at a tension of 120 N by 500 transport rollers. In the heat treatment (ii) -2, the film is heated at 170 ° C. for 40 seconds while being transported at a tension of 120 N by 500 transport rollers. In the heat treatment (ii) -3, the film is heated at 120 ° C. for 200 seconds while being transported at a tension of 100 N by 200 transport rollers (comparative example).

In producing the polarizing plate 101, the heat treatment of (ii) -1 was performed as a heat treatment step. By performing the heat treatment step, a 3000 m roll film was obtained as the first optical film. The thickness of this film was 60 μm.

<Production of second optical film>
According to the following method, the 2nd optical film which consists of a cellulose-ester film was produced.

(Preparation of fine particle dispersion)
10 parts by weight Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) and 90 parts by weight of ethanol were stirred and mixed with a dissolver for 30 minutes, and then high pressure disperser Manton Gorin Was used to prepare a fine particle dispersion.

Into the obtained fine particle dispersion, 88 parts by mass of dichloromethane was added with stirring, and the mixture was diluted by stirring and mixing with a dissolver for 30 minutes. The obtained solution was filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to obtain a fine particle dispersion dilution.

(Preparation of inline additive solution)
To 100 parts by mass of dichloromethane, 36 parts by mass of the prepared fine particle dispersion diluted liquid was added with stirring and further stirred for 30 minutes, and then 6 parts by mass of diacetyl cellulose (acetyl group substitution degree: 2.32, weight average molecular weight 27). Was added with stirring, and further stirred for 60 minutes. The obtained solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain an in-line additive solution. The filter medium having a nominal filtration accuracy of 20 μm was used.

(Preparation of dope)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was filtered with a filter equipped with a leaf disk filter at a temperature of 40 ° C. (boiling point of dichloromethane + 10 ° C.) to obtain a main dope. The filter medium was Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. 244 was used.

<Composition of main dope>
Diacetylcellulose (acetyl group substitution degree: 2.32, weight average molecular weight 270,000)
70 parts by mass Cellulose acetate propionate (acetyl group substitution degree: 1.55, propionyl group substitution degree 0.91, total acyl group substitution degree 2.46, weight average molecular weight 280,000) 30 parts by mass Retardation increasing agent 4 masses Part Sugar ester (benzyl saccharose, average ester substitution degree 5.5) 11 parts by mass Dichloromethane 430 parts by mass Methanol 11 parts by mass

100 parts by mass of the main dope and 2.5 parts by mass of the in-line additive solution were sufficiently mixed with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ) to obtain a dope.

The following compounds were used as the retardation increasing agent.

(Film formation / stretching / drying)
The obtained dope was uniformly cast on a stainless steel band support using a belt casting apparatus under the conditions of a dope liquid temperature of 35 ° C. and a width of 1.95 m and a final film thickness of 33 μm. . On the stainless steel band support, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. The obtained web was further preliminarily dried at 40 ° C. for 30 seconds so that the residual solvent amount was 5% by mass, and then the web was used as a tenter and 1.35 times the original width in the TD direction at 160 ° C. Stretched.

After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while the drying zone was being conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. The obtained film was slit to 1.6 m width, and knurled with a width of 10 mm and a height of 5 μm at both ends of the film, and wound on a core having an initial tension of 220 N / m and a final tension of 110 N / m and an inner diameter of 15.24 cm. A cellulose ester film having a length of 4000 m and a dry film thickness of 33 μm was obtained as a second optical film. The retardation value Ro (550) in the in-plane direction of the obtained second optical film was 50 nm, and the retardation value Rt (550) in the film thickness direction was 130 nm.

<Preparation of polarizing plate>
The 1st optical film and 2nd optical film which were obtained as mentioned above were bonded together on both surfaces of the polarizer, and the polarizing plate was produced.

(Production of polarizer)
The following polarizer was produced with reference to Example 1 of Japanese Patent No. 4691205.
A laminated body in which a PVA layer having a thickness of 7 μm is formed on an amorphous PET base material is produced by air-assisted stretching at a stretching temperature of 130 ° C., and then the stretched laminated body is dyed with iodine or potassium iodide. A colored laminate is produced, and the colored laminate is further stretched integrally with an amorphous PET substrate so that the total draw ratio becomes 5.94 times by stretching in boric acid water at a stretching temperature of 65 degrees. The optical film laminated body (polarizer) containing the PVA layer of was obtained. The amorphous PET substrate was peeled off after the polarizer was bonded to the optical film, and only the PVA layer (polarizing film) was used.

(Preparation of photocurable adhesive)
After mixing the following components, defoaming was performed to prepare a photocurable adhesive. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass

(Lamination of polarizer and optical film)
On the 1st optical film, the prepared photocurable adhesive was apply | coated so that dry thickness might be set to 5 micrometers using a micro gravure coater, and the photocurable adhesive layer was formed. The application was performed under the conditions of gravure roller # 300, rotation speed 140% / line speed.

Similarly, the photocurable adhesive prepared above was applied on the second optical film so as to have a dry thickness of 2 μm to form a photocurable adhesive layer.

A second optical film in which a first optical film having a photocurable adhesive layer formed thereon is disposed on one surface of the produced polarizer and a photocurable adhesive layer is formed on the other surface. Were arranged to obtain a laminate of the first optical film / photocurable adhesive layer / polarizer / photocurable adhesive layer / second optical film. The obtained laminate was bonded by a roll-to-roll method so that the longitudinal direction was matched with a roller machine. As a result of pasting, the slow axis of the first optical film is pasted in a 45 ° oblique direction with respect to the absorption axis of the polarizer, and the slow axis of the second optical film is relative to the absorption axis of the polarizer. Laminated in parallel.

An electron beam was applied from both sides of the laminated laminate so that the photocurable adhesive layer was cured to obtain a laminate. The line speed was 20 m / min, the acceleration voltage was 250 kV, and the irradiation dose was 20 kGy.

Further, an antiglare layer composition having the following composition was prepared, and the thickness of the antiglare layer composition after curing was 5.0 μm on the surface (surface on the viewing side) of the first optical film of the laminate produced above. It was applied with a gravure reverse coater. After drying this in an oven at 70 ° C. for 60 seconds, the coating was cured by irradiating with ultraviolet rays so that the irradiation amount was 120 mJ / cm ² to form an antiglare layer as a functional layer.

Binder resin (pentaerythritol tetraacrylate, manufactured by Nippon Kayaku)
40 parts by mass Binder resin (urethane acrylate, UV1700B, manufactured by Nippon Synthetic Chemical)
60 parts by mass Organic fine particles (styrene-acrylic copolymer, XX245C, average particle size 2 μm, refractive index: 1.515, manufactured by Sekisui Plastics Sales Co., Ltd.) 4 parts by mass Talc (Nanotalc D-1000, average particle size 1 μm, Japan) 3 parts by weight leveling agent (polyether-modified silicone oil, TSF4460, manufactured by Momentive Performance Materials) 0.04 parts by weight Polymerization initiator (Irg184, manufactured by BASF Japan) 6 parts by weight Solvent (toluene) 60 parts by weight Part solvent (cyclohexanone) 40 parts by mass

Thus, a polarizing plate 101 was produced.

<< Production of polarizing plates 102 to 113 >>
In the production of the polarizing plate 101, the crossing angle θ of the slow axis with respect to the absorption axis of the polarizer of the first optical film is changed to the value shown in Table 1, and the heat treatment process is changed to the method shown in Table 1. Polarizers 102 to 113 were produced in the same manner except that.

<< Production of Polarizing Plate 114 >>
In the production of the polarizing plate 101, when the second optical film is bonded to the polarizer, except that the slow axis of the second optical film is orthogonal to the absorption axis of the polarizer. Similarly, a polarizing plate 114 was produced.

<< Evaluation of polarizing plates 101-114 >>
The following evaluations were performed on the manufactured polarizing plates 101 to 114. For the following evaluations (3) to (6), liquid crystal display devices and organic EL display devices were prepared in advance as described below using polarizing plates 101 to 114, and evaluation was performed using the display devices. It is. Each evaluation result is shown in Table 1.

(Production of liquid crystal display device)
The polarizing plate on the viewing side was peeled off from a commercially available 20-inch VA mode liquid crystal display device, and the produced polarizing plates 101 to 114 were bonded to the substrate surface of the liquid crystal cell to produce a liquid crystal display device. At that time, the polarizing plates 101 to 114 were bonded so that the absorption axis was in the same direction as the polarizing plate on the viewing side that had been bonded in advance. At this time, the polarizing plates 101 to 114 were arranged so that the second optical films of the polarizing plates 101 to 114 were on the liquid crystal cell side.

(Production of organic EL display device)
Using the polarizing plates 101 to 114, organic EL display devices were produced in the same manner as in paragraphs [0180] to [0186] of JP2013-109869A. At this time, the polarizing plates 101 to 114 were arranged so that the first optical films of the polarizing plates 101 to 114 were on the organic EL light emitting element side.

(1) Measurement of the dimensional change rate before and after the heat treatment step of the first optical film The first optical film used for each of the polarizing plates 101 to 114 by the measurement method described in the above “dimensional change rate of the first optical film”. L (θ), L (θ + 90), L (MD) and L (TD) were measured before and after the heat treatment step of the optical film. From the measurement results, respective values of L (θ) / L (θ + 90) and L (MD) / L (TD) were calculated.

(2) Measurement of optical value of first optical film Retardation values Ro and Rt of the first optical film used for the polarizing plates 101 to 114 were measured using an automatic birefringence meter KOBRA-21AWR (Oji Scientific Instruments) And the birefringence measurement at each wavelength in an environment of 23 ° C. and 55% RH.

(3) Image distortion when mounted on a liquid crystal display device After the prepared liquid crystal display device is placed under conditions of 40 ° C. and 90% RH for 100 hours, the liquid crystal display device is placed under the conditions of 23 ° C. and 55% RH. Observed in this way.
In other words, the liquid crystal display device is placed on a desk 80 cm high from the floor so that the display screen faces vertically upward, and a daylight direct fluorescent lamp (FLR40S • D is placed on the ceiling 3 m high from the floor. (/ MX manufactured by Panasonic Corporation) 40W × 2 sets were set as 10 sets at intervals of 1.5 m. In this case, when the evaluator is in front of the display screen of the liquid crystal display device, the fluorescent lamp is arranged so that the fluorescent lamp is positioned on the ceiling from the evaluator's overhead to the rear.
After disposing the liquid crystal display device in this way, the display screen of the liquid crystal display device was observed and evaluated according to the following criteria.
◎: Fluorescent lamp looks straight ○: Fluorescent lamp appears to be slightly bent △: Fluorescent lamp appears to be bent ×: Fluorescent lamp appears to swell greatly

(4) Visibility of Screen when Mounted on Liquid Crystal Display Device Twenty samples of the liquid crystal display device as described above were produced for each of the polarizing plates 101 to 114. As a durability test, each sample of the liquid crystal display device was placed at 40 ° C. and 90% RH for 100 hours, and then a difference in visibility was observed between the screen center and the screen periphery using a polarizing microscope. The results were evaluated according to the following criteria.
◎: Peripheral brightness increase (visibility degradation) was 0 in 20 samples. ○: Peripheral brightness increase (visibility degradation) was 1-2 in 20 samples. △: Peripheral brightness increase (visibility degradation) was 3-5 in 20 samples. X: Peripheral brightness increase (visibility degradation) was 6 or more in 20 samples.

(5) Distortion of device when mounted on organic EL display device After the produced organic EL display device is placed under the condition of 40 ° C and 90% RH for 100 hours, it is placed under the condition of 23 ° C and 55% RH and the organic EL display device Was observed as follows.
That is, the organic EL display device is placed on a desk 80 cm high from the floor so that the display screen is vertically upward, and a daylight direct fluorescent lamp (FLR40S · (D / MX Panasonic Corporation) 40W × 2 were set as one set, and 10 sets were arranged at intervals of 1.5 m. In this case, when the evaluator is in front of the display screen of the organic EL display device, the fluorescent lamp is arranged so that the fluorescent lamp is positioned on the ceiling from the evaluator's overhead to the rear.
After arranging the organic EL display device in this way, the display screen of the organic EL display device was observed and evaluated according to the following criteria.
◎: Fluorescent lamp looks straight ○: Fluorescent lamp appears to be slightly bent △: Fluorescent lamp appears to be bent ×: Fluorescent lamp appears to swell greatly

(6) Visibility of the screen when mounted on an organic EL display device After the prepared organic EL display device is placed under conditions of 40 ° C. and 90% RH for 100 hours, the organic EL display is placed under conditions of 23 ° C. and 55% RH. The apparatus was observed. The results were evaluated according to the following criteria.
◎: When viewing the fabricated EL display device, the image of myself or the background is not visible at all. ○: When viewing the fabricated EL display device, the image of itself or the background is not very visible. △: Produced EL display. When you look at the device, you can see the image of yourself and the background along with the image of the display device, but the actual harm is low. , Harmful

As shown in Table 1, the dimensional change rate L (θ) in the slow axis direction of the first optical film and the dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis are expressed by the above formula (1) and When the polarizing plates 101 to 104, 109 to 112, 114 of the present invention satisfying (2) are mounted on a liquid crystal display device or an organic EL display device, the occurrence of distortion of the device is suppressed, and the visibility is also improved. It was good. Therefore, in the polarizing plate of the present invention, the occurrence of physical distortion is suppressed, and it is considered that the above result was obtained.
In order to obtain such a polarizing plate of the present invention, after the oblique stretching step, the film end is embossed in the range of 180 to 220 ° C. and then wound in a roll shape. Heat treatment (i) for 3 to 5 days under the conditions of 60 to 80 ° C. and 20% RH or less, or the film is conveyed through the conveyance roller while being conveyed at a tension of 120 to 150 N by the conveyance roller. It was found that it is preferable to perform heat treatment (ii) in which heat treatment is performed at 140 to 170 ° C. for 40 to 600 seconds.

On the other hand, the dimensional change rate L (θ) in the slow axis direction of the first optical film and the dimensional change rate L (θ + 90) in the direction orthogonal to the slow axis represent the above formulas (1) and (2). When the polarizing plates 105 to 107 of the comparative examples that are not satisfied are mounted on a liquid crystal display device or an organic EL display device, the device is distorted and the visibility of the display screen is low. This is considered to be because the polarizing plate of the comparative example caused physical distortion when exposed to a high humidity environment, and also caused distortion in the liquid crystal display device or the organic EL display device.

In addition, the polarizing plates 108 and 113 of the comparative examples in which the crossing angle between the slow axis of the first optical film and the absorption axis of the polarizer is not in the range of 30 to 60 ° have a low display screen visibility. It has become.

[Example 2]
<< Production of Polarizing Plates 201 to 205 >>
In the production of the polarizing plate 101 in Example 1 above, the methods of the transverse stretching process and the oblique stretching process at the time of producing the first optical film were changed in the same manner except that the methods described in Table 2 were used. 205 was produced.

In Table 2, in the transverse stretching step, the film obtained in the casting step was dried to have a residual solvent amount of 10% by mass, and then 1% of the original width in the width direction at 170 ° C. When the film was stretched at a draw ratio of 15 times, “Method A1”, the film obtained in the casting step was dried to have a residual solvent amount of 10% by mass, and then the original width in the width direction at 150 ° C. When the film was stretched at a stretching ratio of 1.10 times with respect to “Method A2,” the film obtained in the casting step was dried to a residual solvent amount of 20% by mass, and then the width was 135 ° C. When the film was stretched at a draw ratio of 1.07 times the original width in the direction “Method A3”, the film obtained in the casting step was dried to make the residual solvent amount 1% by mass, The case where the film was stretched at a draw ratio of 1.05 times the original width in the width direction under the conditions 4 ", it shows a case that has not been the transverse stretching itself as" none ".

Also, in Table 2, when the film was obliquely stretched at a stretching temperature of 185 ° C. and a stretching ratio of 1.7 times in the oblique stretching step, “Method B1”, the film was slanted at a stretching temperature of 175 ° C. and a stretching ratio of 1.8 times. The stretched case is indicated as “Method B2”.

<< Evaluation of polarizing plates 201-205 >>
In the same manner as in Example 1, the dimensional change rate before and after the heat treatment step of the first optical film, the optical value of the first optical film, and the liquid crystal display device were mounted on the prepared polarizing plates 201 to 205. The distortion of the device in the case, the visibility of the screen, the distortion of the device when mounted on the organic EL display device, and the visibility of the screen were evaluated. Further, the polarizing plate yield was evaluated for the produced polarizing plates 201 to 205 as follows. The evaluation results are shown in Table 2. In Table 2, the evaluation results of the polarizing plate 101 in Example 1 are also shown.

(Polarizing plate yield)
The surfaces of the produced polarizing plates 101 and 201 to 205 were visually observed, and those having no surface failure or flatness failure were regarded as non-defective products. The ratio of non-defective products and defective products when 50 polarizing plates were produced was calculated and evaluated according to the following criteria.
◎: Non-defective polarizing plate is 95% or more ○: Non-defective polarizing plate is 80% or more and less than 95% △: Non-defective polarizing plate is 60% or more and less than 80% ×: Non-defective polarizing plate is less than 60%

As shown in Table 2, the polarizing plate of the present invention in which the dimensional change rate L (MD) in the longitudinal direction and the dimensional change rate L (TD) in the width direction of the first optical film satisfy the above formula (3). 101, 202, 203, and 205 were found to be excellent in polarizing plate yield.
Further, in order to obtain such polarizing plates 101, 202, 203, 205, it is preferable to perform a transverse stretching step when producing the first optical film, and further, the residual solvent amount is 10 to 20% by mass, More preferably, the transverse stretching step is carried out under conditions of a stretching temperature of 135 to 170 ° C. and a stretching ratio of 1.07 to 1.15, and the residual solvent amount is 10% by mass, the stretching temperature is 150 to 170 ° C., and the stretching ratio is 1.1 to 1. It was found that it is more preferable to perform the transverse stretching step under the condition of 1.15.

Further, in the oblique stretching step for producing the first optical film, the stretching temperature is 185 ° C. and the stretching ratio is 1.7 times, rather than the oblique stretching under the stretching temperature of 175 ° C. and the stretching ratio of 1.8 times. When the polarizing plate is mounted on the liquid crystal display device, it is found that when the polarizing plate is mounted on the liquid crystal display device, distortion of the device is suppressed and the visibility of the display screen is improved.

[Example 3]
<< Production of Polarizing Plates 301 to 306 >>
Polarizers 301 to 306 were produced in the same manner as in the production of the polarizing plate 201 in Example 2, except that the substrate type of the first optical film was changed to that shown in Table 3.

In Table 3, cellulose acetate propionate (acetyl substitution degree 1.50, propionyl substitution degree 0.90, total substitution degree 2.40, weight average molecular weight 220,000) is “CAP”, cellulose acetate (acetyl substitution degree). Degree 2.85, weight average molecular weight 250,000) “TAC”, cellulose acetate (acetyl substitution degree 2.43, weight average molecular weight 200,000) “DAC”, cellulose acetate benzoate (acetyl substitution degree 1.90, benzoyl substitution) Degree 0.30, total substitution degree 2.20, weight average molecular weight 150,000) “CeBz”, methyl cellulose (methyl ether substitution degree 2.5, weight average molecular weight 150,000) “CE-1”, ethyl cellulose (ethyl ether) Substitution degree 2.5, weight average molecular weight 150,000) "CE-2", cellulose ether benzoate Shows (ethyl ether substitution degree 2.2, benzoyl substitution degree 0.7, weight average molecular weight 150,000) as "CEBz".

<< Evaluation of polarizing plates 301 to 306 >>
The produced polarizing plates 301 to 306 were mounted in the liquid crystal display device in the same manner as in Example 1, the rate of dimensional change before and after the heat treatment step of the first optical film, the optical value of the first optical film, and the liquid crystal display device. The distortion of the device in the case, the visibility of the screen, the distortion of the device when mounted on the organic EL display device, and the visibility of the screen were evaluated. The evaluation results are shown in Table 3. Table 3 also shows the evaluation results of the polarizing plate 201 in Example 2.

As shown in Table 3, it was found that it is preferable to use cellulose acetate propionate or cellulose acetate benzoate as the material of the first optical film from the viewpoint of suppressing physical distortion of the polarizing plate.
Further, when methylcellulose is used as the material of the first optical film, the dimensional change rate L (θ) in the slow axis direction does not satisfy the above formula (2). Therefore, in the present invention, the material of the first optical film is It can be said that methylcellulose cannot be used.

[Example 4]
<< Production of Polarizing Plates 401 and 402 >>
Polarizers 401 and 402 were produced in the same manner as in the production of the polarizing plate 101 in Example 1 except that the base material type of the second optical film was changed to that shown in Table 4.

In Table 4, cellulose acetate (acetyl substitution degree 2.85, weight average molecular weight 250,000) is shown as “TAC”, and cellulose acetate (acetyl substitution degree 2.43, weight average molecular weight 200,000) is shown as “DAC”. ing.

<< Evaluation of Polarizing Plates 401 and 402 >>
The produced polarizing plates 401 and 402 were evaluated in the same manner as in Example 1 for device distortion and screen visibility when mounted on a liquid crystal display device. The evaluation results are shown in Table 4. Table 4 also shows the evaluation results of the polarizing plate 101 in Example 1.

As shown in Table 4, cellulose acetate propionate, cellulose acetate having an acetyl substitution degree of 2.43 or 2.85 can be preferably used as the material of the second optical film, and among them, cellulose acetate propionate or It has been found that cellulose acetate having an acetyl substitution degree of 2.43 is more preferable, and cellulose acetate propionate is most preferable.

As described above, the present invention is a polarizing plate comprising an obliquely stretched optical film, a polarizing plate in which the occurrence of physical distortion is suppressed, a method for producing such a polarizing plate, and the polarizing plate Suitable for providing a liquid crystal display device and an organic electroluminescence display device.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Film delivery part 3, 7 Conveyance direction change part 4, 6 Guide roll 5 Stretching part 8 Film cutting apparatus 9 Film winding part 10 Liquid crystal display device 11 Liquid crystal cell 12, 13, 52 Polarizing plate 14 Backlight 15, 53 Front plate 21, 31, 61 Polarizer 22, 62 First optical film 23, 63 Functional layer 24, 64 Second optical film 32, 33 Optical film 50 Organic EL display device 51 Organic EL light emitting device Ci, Co Tool D1 Feeding direction D2 Winding direction Ri, Ro Rail W, Wo Width Z1 Preheating zone Z2 Stretching zone Z3 Heat fixing zone θi Feeding angle θL Angle

Claims (12)

1. A polarizing plate comprising: a polarizer; a first optical film provided to face one surface of the polarizer; and a second optical film provided to face the other surface of the polarizer. And
   The crossing angle θ between the slow axis of the first optical film and the absorption axis of the polarizer is in the range of 30-60 °,
   The dimensional change rate L (θ) in the slow axis direction of the first optical film and the dimensional change rate L (θ + 90) in the direction perpendicular to the slow axis satisfy the following expressions (1) and (2). A polarizing plate characterized by being adjusted to.
   Formula (1): 0.50 ≦ L (θ) / L (θ + 90) ≦ 0.95
   Formula (2): 0.1 (%) ≦ L (θ) ≦ 1.5 (%)
2. The dimensional change rate L (MD) in the longitudinal direction and the dimensional change rate L (TD) in the width direction of the first optical film satisfy the following formula (3). Polarizer.
   Formula (3): 0.50 ≦ L (MD) / L (TD) <1.00
3. The polarizing plate according to claim 1 or 2, wherein the first optical film contains a polymer having a cellulose skeleton.
4. The retardation value Ro (550) in the in-plane direction at a wavelength of 550 nm of the first optical film is in the range of 75 to 150 nm, according to any one of claims 1 to 3. The polarizing plate as described.
5. The polarizing plate according to any one of claims 1 to 4, wherein the first optical film contains cellulose acetate propionate.
6. The polarizing plate according to any one of claims 1 to 5, wherein a slow axis of the second optical film and an absorption axis of the polarizer are parallel or orthogonal to each other.
7. The polarizing plate according to any one of claims 1 to 6, wherein the second optical film contains cellulose acetate or cellulose acetate propionate.
8. The hard coat layer or the anti-glare layer is provided on the surface on the viewing side of the optical film disposed on the viewing side of the first optical film and the second optical film. The polarizing plate according to claim 7.
9. A manufacturing method for manufacturing the polarizing plate according to any one of claims 1 to 8,
   The manufacturing method of the polarizing plate characterized by having the bonding process which bonds the said polarizer, a said 1st optical film, and a said 2nd optical film by a roll to roll system.
10. A casting step of casting a dope on a support to form a casting film;
    A transverse stretching step of stretching the cast film having a residual solvent amount of 1 to 20% by mass in the width direction at a stretching ratio of 1.01 to 1.3 times;
    An oblique stretching step of stretching the casting film in an oblique direction with respect to the width direction;
    A heat treatment step of obtaining the first optical film by performing the following heat treatment (i) or (ii) on the cast film,
    The method for producing a polarizing plate according to claim 9, wherein the bonding step is performed after the heat treatment step.
    (I) The end of the cast film is embossed in the range of 180 to 220 ° C., and then wound in a roll shape, and the condition is 3 to 60 ° C. and 20% RH or less. Heat for ~ 5 days.
    (Ii) The cast film is heat-treated at 140 to 170 ° C. for 40 to 600 seconds through the transport roller while transporting the cast film with a tension of 120 to 150 N by a transport roller.
11. A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 8.
12. An organic electroluminescence display device comprising the polarizing plate according to any one of claims 1 to 8.

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