KR102222797B1 - Optical film, method for manufacturing the same, polarizing plate and liquid crystal display device comprising the same - Google Patents

Abstract

Providing an optical film excellent in handling properties at the time of manufacturing a polarizing plate, and a good polarizing plate curl when attached to a polarizing plate, a manufacturing method of an optical film, a polarizing plate, and a liquid crystal display device.
A core layer containing a cellulose acylate having an average degree of acyl substitution of 2.00 to 2.55, and a first skin layer containing a cellulose acylate having an average degree of acyl substitution of 2.60 to 3.00 on one surface of the core layer, and a core layer An optical film having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of, and the radius of curvature of the curl of the film after being left to stand for 30 minutes in an environment at 25°C and 60% relative humidity. An optical film having a radius of curvature of 10 mm or more and 25 mm or less, which is larger than 25 mm, and the curvature radius of the curl in water of the film after being left still in water at 25° C. for 30 minutes.

Description

Optical film, manufacturing method of optical film, polarizing plate, and liquid crystal display device {OPTICAL FILM, METHOD FOR MANUFACTURING THE SAME, POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE COMPRISING THE SAME}

The present invention relates to an optical film having a favorable polarizing plate curl when used for a polarizing plate. The present invention also relates to a method of manufacturing the optical film, and a polarizing plate and a liquid crystal display device having the optical film.

In recent years, a large screen of a liquid crystal display device and thinning of a liquid crystal display device and a member for use thereof are in progress. In terms of design, a design that narrows the frame of a television is preferred. In addition, due to the increase in demand in emerging countries, the transport distance of liquid crystal panels is increasing, and opportunities to move to places with high relative humidity are increasing.

Patent Document 1 discloses that by using a cellulose acylate film containing a specific ultraviolet absorber in a predetermined amount, color unevenness during black display after a high-temperature, high-humidity environment and peripheral unevenness occurring in the corners of the display portion can be suppressed.

In Patent Literature 2, as a means of improving the curl of the polarizing plate, after bonding one transparent protective film with the polarizer among two transparent protective films bonded to both sides of the polarizer, the other transparent protection on the other side The manufacturing method of the polarizing plate which bonds a film is described.

In Patent Document 3, by laminating an optical film A with a small amount of curl at the end portion on the surface of the optical film B with a relatively large amount of curl at the end portion in the direction TD perpendicular to the machine flow direction, TD A method of manufacturing an optical film layered product X in which curl at the edge is suppressed is described. Specifically, the conveyance process (A) of conveying the optical films A and B in a state given a tension along the machine flow direction (MD), respectively, and bonding the optical film A to the surface side where curls become concave in the optical film B. It is described that performing the bonding process (B) is described, and in the bonding process (B), the tension imparted to the machine flow direction (MD) in the _{optical film B} is T B, in the machine flow direction (MD) in the optical film A. When the tension to be applied is T _A , it is described that the optical films A and B are bonded in a state in which tension is applied so that the tension ratio (T _B /T _{A) <1.} In Patent Document 3, adjusting the curl of a polarizing plate made of a three-layer laminate is not described.

Patent Document 4 describes a cellulose acylate film in which the ratio of the content ratio of the other plasticizer to one when divided into two in the thickness direction is from 1.2 to 2.0, and the curl radius in water at 25°C is 25 mm or more.

Japanese Laid-Open Patent Publication No. 2011-173964 Japanese Laid-Open Patent Publication No. 2004-117482 Japanese Unexamined Patent Publication No. 2013-11774 Japanese Unexamined Patent Publication No. 2003-145563

As described above, the transport distance of the liquid crystal panel is increasing, and the opportunity to move to a place with high relative humidity is also increasing. However, it is necessary to maintain the uniformity of display quality even after transport. In addition, when the curl of the polarizing plate is large, it has been found that bubbles enter the end portions during panel bonding, or that light leakage occurs at the end portion of the polarizing plate after a high-temperature, high-humidity endurance test. In particular, with a large-sized thin polarizing plate, curl adjustment is insufficient by a conventional method.

The present invention makes it a subject to be solved to provide an optical film in which folding of an end portion at the time of manufacturing a polarizing plate is suppressed and curling of a polarizing plate is suppressed, a manufacturing method thereof, and a polarizing plate. In addition, the present invention is a problem to be solved to provide an optical film capable of preventing air bubbles when bonding an optical film to a liquid crystal panel and suppressing light leakage after a high-temperature, high-humidity endurance test, a manufacturing method thereof, and a polarizing plate. do. Further, the present invention makes it a subject to be solved to provide a liquid crystal display device having the above optical film and having good oblique light leakage and end light leakage after time.

As a result of intensive examination in order to solve the above problems, the present inventors have found that the curl of the polarizing plate can be reduced by adjusting the curl of the film in a predetermined range rather than simply reducing it. The present invention was completed based on these findings.

That is, according to the present invention, the following invention is provided.

(1) A core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, and a first skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer. Have,

As an optical film having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer,

The curvature radius of the curl of the film after being allowed to stand for 30 minutes in an environment of 25°C 60% relative humidity is greater than 25 mm, and the radius of curvature of the underwater curl of the film after standing in water at 25°C for 30 minutes is 10 mm or more An optical film of 25 mm or less.

(2) The optical film according to (1), wherein the overall film thickness of the optical film is 3 µm or more and 50 µm or less, and the thickness of the first skin layer and the second skin layer is 0.3 µm or more and 3 µm or less, respectively.

(3) The optical film according to (1) or (2), wherein the core layer contains 1 to 9 parts by mass of polycondensation ester with respect to 100 parts by mass of cellulose acylate.

(4) The optical film in any one of (1)-(3) which satisfy|fills following formula 1 and following formula 2;

Equation 1: 30 ㎚ ≤ Re (550) ≤ 80 ㎚

Equation 2: 80 ㎚ ≤ Rth (550) ≤ 150 ㎚

However, Re (550) represents the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) represents the retardation in the thickness direction of the optical film at a wavelength of 550 nm.

(5) a dope for forming a core layer containing 1 to 9 parts by mass of a polycondensation ester with respect to 100 parts by mass of cellulose acylate;

A dope for forming a first skin layer containing 0 parts by mass or more and less than 0.05 parts by mass of a polycondensation ester based on 100 parts by mass of cellulose acylate,

Including a step of producing a film by covalently rolling a dope for forming a second skin layer containing 0 parts by mass or more and less than 0.05 parts by mass of a polycondensation ester per 100 parts by mass of cellulose acylate on a support ( The method for producing an optical film according to any one of 1) to (4).

(6) In (5) which includes the step of further stretching the film, the residual solvent amount of the film at the start of stretching is 0 mass% or more and 3 mass% or less, and the film elastic modulus at the start of stretching is 100 MPa or more and 1500 MPa or less The manufacturing method of the described optical film.

(7) A polarizing plate having a polarizer and the optical film according to any one of (1) to (4).

(8) The optical film according to any one of (1) to (4), the polarizer, and the protective film are arranged in the above order, and the underwater curl of the optical film and the underwater curl of the protective film are in the same direction. The polarizing plate according to (7) curled.

(9) The optical film produced by the manufacturing method described in (5) or (6), the polarizer, and the protective film are arranged in the above order, and the underwater curl of the optical film and the underwater curl of the protective film are the same. The polarizing plate according to (7) curled in the direction.

(10) A liquid crystal display device having the polarizing plate according to any one of (7) to (9).

In the optical film and the polarizing plate of the present invention, folding of the edge portion at the time of manufacturing the polarizing plate can be suppressed, and further, the curling of the polarizing plate can be suppressed. The liquid crystal display device of the present invention has good oblique light leakage and end light leakage after time.

1 is a schematic diagram of the vicinity of a flexible die.
2 is an explanatory diagram of an example of a shared smoke.
Fig. 3 is a diagram showing that the film is cut in 4 directions so as to be spaced at 45° intervals.
It is a figure which shows the case where the underwater curl of an optical film and the underwater curl of a protective film are curled in the same direction.

Hereinafter, the present invention will be described in detail. In addition, in this specification, the numerical range shown using "-" means a range including the numerical value described before and after "-" as a lower limit and an upper limit.

In the present specification, Re (λ) and Rth (λ) represent in-plane retardation (nm) and retardation in the thickness direction (nm) of the film at wavelength λ, respectively. In addition, in the present specification, when there is no particular description, the wavelength λ is set to 550 nm. Re (λ) is measured by injecting light having a wavelength of λ nm into the film normal direction in KOBRA 21ADH or WR or KOBRA CCD series (manufactured by Oji Measuring Instruments Co., Ltd.).

When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.

Rth (λ) is the in-plane slow axis (determined by KOBRA 21ADH or WR or KOBRA CCD series) as the oblique axis (rotation axis) (if there is no ground axis, an arbitrary direction in the film plane) Is the rotation axis) From the normal direction to the film normal direction to 50 degrees on one side in 10 degree steps, light having a wavelength of λ nm is incident from each of the inclined directions to measure 6 points in total, and the measured retardation value and the average refractive index Based on the assumed value of and the input film thickness, it is calculated by KOBRA 21ADH or WR or KOBRA CCD series.

In the above, in the case of a film having a direction in which the retardation value becomes zero at a certain inclination angle with the in-plane slow axis as the rotation axis from the normal direction, the retardation value at an inclination angle greater than the inclination angle is negative. After changing to (負), it is calculated as KOBRA 21ADH or WR or KOBRA CCD series. In the selection of the measurement wavelength λ nm, the wavelength selection filter can be manually replaced, or the measurement value can be converted by a program or the like to measure.

In addition, with the slow axis as the inclined axis (rotation axis) (if there is no ground axis, an arbitrary direction in the film plane is used as the rotation axis), and the retardation value is measured from two randomly inclined directions, and the value and the average refractive index are assumed. Based on the value and the input film thickness value, Rth can also be calculated from the following equations (X) and (XI).

Said Re(θ) represents a retardation value in a direction inclined at an angle θ from the normal direction. In addition, in the formula, nx represents a refractive index in a slow axis direction in a plane, ny represents a refractive index in a direction orthogonal to nx in a plane, and nz represents a refractive index in a direction orthogonal to nx and ny. d represents the film thickness.

When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, or a film without a so-called optical axis, Rth (λ) is calculated by the following method.

Rth (λ) is the inclined axis (rotation axis) with Re (λ) as the in-plane slow axis (determined by KOBRA 21ADH or WR or KOBRA CCD series), and -50 degrees to +50 degrees with respect to the film normal direction. Measure 11 points by injecting light with a wavelength of λ ㎚ from the inclined direction in steps of 10 degrees up to, and calculating with KOBRA 21ADH or WR based on the measured retardation value and the assumed value of the average refractive index and the input film thickness. do.

In the above measurement, the values of the polymer handbook (JOHN WILEY & SONS, INC) and catalogs of various optical films can be used as the assumption of the average refractive index. If the value of the average refractive index is not known, it can be measured with an Abbe refractometer. The value of the average refractive index of the main optical film is illustrated below:

Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

By inputting the assumed value and film thickness of these average refractive indexes, the KOBRA 21ADH or WR or KOBRA CCD series calculates nx, ny, and nz. From this calculated nx, ny, nz, Nz = (nx-nz)/(nx-ny) is further calculated.

In addition, retardation can also be measured using AxoScan (AXOMETRICS).

In the present invention, a "ground axis" such as a retardation film means a direction in which the refractive index becomes the maximum. In addition, the measurement wavelength of the refractive index is a value at the wavelength λ = 550 nm in the visible light region unless otherwise specified.

In addition, in the present specification, the numerical values and numerical ranges indicating the optical properties of each member are interpreted as indicating numerical values, numerical ranges, and properties including generally acceptable errors for a liquid crystal display device or a member used therein. It should be.

In this specification, the number average molecular weight is defined as a polystyrene conversion value obtained by gel permeation chromatography (GPC) measurement. In this specification, the number average molecular weight (Mn) is, for example, using HLC-8220 (manufactured by Tosoh Corporation), and TSKgel (registered trademark) Super AWM-H (manufactured by Tosoh Corporation, 6.0) as a column. It can be calculated|required by using mmID x 15.0 cm Unless otherwise specified, the eluent is measured using a 10 mmol/L lithium bromide NMP (N-methylpyrrolidinone) solution.

[Optical film]

The optical film of the present invention includes a core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, and a cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer. An optical film having a skin layer and having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer, and allowed to stand in an environment at 25° C. 60% relative humidity for 30 minutes. It is an optical film in which the curvature radius of the curl of the subsequent film is larger than 25 mm, and the curvature radius of the underwater curl of the film after being allowed to stand in water at 25° C. for 30 minutes is 10 mm or more and 25 mm or less.

In this specification, the curl of the film (including the curl of the film in water) is defined below. When the film has a longitudinal direction, the longitudinal direction is set as the first direction, and when the film is the same side length, the direction of an arbitrary side is set as the first direction, and when there is no longitudinal direction, an arbitrary direction is set as the first. It is set as a direction, cut into 35 mm x 3 mm so that the first direction becomes a long side, and the radius of curvature in the long side direction is measured, and it is set as the radius of curvature in the first direction. Similarly, with respect to the first direction, the directions at intervals of 45° are respectively long sides, and the radii of curvature in the second to fourth directions are measured. Among the radii of curvature in the first to fourth directions, the direction having the minimum curvature radius is referred to as the curl direction of the film, and the curvature radius is referred to as the curvature radius of the curl of the film.

The measurement of the radius of curvature of the curl (also referred to as 25°C 60% relative humidity curl) of the film after leaving it to stand in a 25°C 60% relative humidity environment for 30 minutes can be performed as follows. The film is cut out into 35 mm x 3 mm. At this time, the long side direction is cut out in the first to fourth directions at intervals of 45°.

After allowing it to stand in an environment of 25° C. 60% relative humidity for 30 minutes, it can be measured according to the measurement method A of ISO (International Organization for Standardization) 18910: 2000 (Imaging materials -Photographic film and paper- Determination of curl). The radius of curvature in the cut-out long-side direction (35 mm) is read, and the value of the direction that becomes the minimum value among the curvature radii in the first to fourth directions is taken as the radius of curvature of the film 25° C. 60% relative humidity curl.

In addition, when evaluating the curl in the MD direction (longitudinal direction) of the film, the MD direction of the film is 35 mm, and when evaluating the curl in the TD direction of the film, the TD direction (transverse direction) of the film is set to 35 mm.

(Measurement method of underwater curl of film)

The film was sampled in the same direction as the above 25°C 60% relative humidity curl, immersed in water at 25°C for 30 minutes, and then ISO 18910:2000 (Imaging materials -Photographic film and paper- Determination of curl) Measurement Method A It is measured according to, and the radius of curvature is measured. The radius of curvature in the cut-out long-side direction (35 mm) is read, and the value of the direction in which the radius of curvature becomes the minimum value among the first to fourth directions is taken as the radius of curvature of the underwater curl of the film.

In addition, when evaluating the curl in the MD direction (longitudinal direction) of the film, the MD direction of the film is 35 mm, and when evaluating the curl in the TD direction of the film, the TD direction (transverse direction) of the film is set to 35 mm.

The effects of 25° C. 60% relative humidity curl and underwater curl to polarizing plate production and polarizing plate curl are as follows. The polarizing plate is generally manufactured by the following method. After conveying the optical film, polarizer, and protective film in a room temperature and humidity environment, between the optical film and the polarizer, and between the protective film and the polarizer are applied with a polyvinyl alcohol (PVA)-based adhesive. Thereafter, it is heated (40 to 80°C), and the PVA-based adhesive is dried and bonded to form a laminate.

At the time of conveyance before the film is wetted with a PVA-based adhesive, if the 25°C 60% relative humidity curl is small (the radius of curvature is large), the curl of the film is small, and the handling property at the time of manufacturing the polarizing plate can be improved. When the film is heated after being wetted with a PVA-based adhesive, the film begins to curl under the influence of underwater curl, and even if it returns to room temperature and humidity, the curl of the film does not return to its original state. Moreover, at the timing when the film starts to curl, it is adhered as a polarizing plate. The polarizing plate is a laminate, and since the balance of the stretching force of each layer affects the formation of the polarizing plate curl, the effect of correcting the curl as a laminate is produced by the force that the film wants to curl after bonding, thereby reducing the curl of the polarizing plate. can do.

The radius of curvature of the 25° C. 60% relative humidity curl of the optical film of the present invention is greater than 25 mm, preferably 30 mm or more, and more preferably 40 mm or more. The upper limit of the radius of curvature of the 25° C. 60% relative humidity curl of the optical film of the present invention is not particularly limited. By making the radius of curvature of the curl at 25° C. 60% relative humidity in the above range, it is possible to suppress the occurrence of folding of the edge during manufacturing the polarizing plate.

The radius of curvature of the underwater curl of the optical film of the present invention is 10 mm or more and 25 mm or less, preferably 10 mm or more and less than 25 mm, more preferably 11 mm or more and 22 mm or less, and more preferably 12 mm or more. It is 20 mm or less. By setting the radius of curvature of the underwater curl into the above range, the curl after bonding to the polarizing plate can be reduced.

As described above, in the optical film of the present invention, for adjusting the curl of the polarizing plate, the underwater curl of the optical film is increased (the radius of curvature is small), while for stabilizing the production of the polarizing plate, the optical film has a relative humidity of 25°C and 60%. The curl is made small (the radius of curvature is increased). Conventionally, it is considered that the underwater curl of the film and the curl of 25 ℃ 60% relative humidity are interlocked (if the curl in water is large, the curl at 25 ℃ 60% relative humidity is large, and if the curl in water is small, the curl at 25 ℃ 60% relative humidity is also small). Was becoming. In the present invention, it was found that the curl of the polarizing plate can be made small by adjusting the radius of curvature of the curl at 25° C. 60% relative humidity to be 10 mm or more and 25 mm or less, and the radius of curvature of the underwater curl is larger than 25 mm. .

In order to reduce the curl at 25°C and 60% relative humidity, it is effective to reduce the difference between the amount of deformation caused by absorption of the surface and the back surface at 25°C and 60% relative humidity. I think it is valid. In addition, it is also effective to balance the physical properties of the surface and the back surface, and for this purpose, a film is prepared by covalent brazing using multiple types of dope, and the film thicknesses of the skin layer on the surface and the skin layer on the back surface are made close to each other. It is considered effective to make the skin layer thinner. On the other hand, in order to increase the curl in water, it is effective to change the physical properties (moisture content, elastic modulus) in the film thickness direction, and for that purpose, it is considered that the method of producing a film by covalent brazing using a plurality of types of dope is effective. In addition, it is also effective to increase the difference in the residual deformation amount of the front and back released by water immersion, and to do so, increase the difference between the glass transition temperature between the front and back surfaces at the time of stretching by adjusting the amount of additive added within a predetermined range. It is considered effective that no additives are added to the skin layer at the time of manufacture, and stretching with a high elastic modulus.

(Layer structure of the film)

The optical film of the present invention includes a core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, and a cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer. It has a skin layer, and has a 2nd skin layer containing cellulose acylate with an average acyl substitution degree 2.60-3.00 on the other surface of the core layer.

In the present specification, the term "core layer" refers to a layer having the thickest film thickness, and the term "skin layer" refers to a layer having a thinner film thickness than the core layer and in contact with the core layer.

The optical film of the present invention can be produced by forming a film by simultaneously or sequentially casting a dope containing cellulose acylate on a support in multiple layers as described later, but even in that case, each layer is mixed with each other to create a clear interface. It may be in a state that is not formed.

Moreover, only one type of cellulose acylate may be used in each layer, and a plurality of cellulose acylates may be mixed in one layer, but the cellulose acylate in each layer is preferably one type.

(Film thickness)

The film thickness of the entire optical film of the present invention is preferably 3 µm or more and 50 µm or less, more preferably 5 µm or more and 47 µm or less, and still more preferably 7 µm or more and 45 µm or less.

When the film thickness is set to 3 µm or more, since strength as a film can be secured, it is preferable, and when the film thickness is set to be 50 µm or less, it is easy to cope with changes in humidity and easy to maintain optical properties.

It is preferable that the thickness of the first skin layer and the second skin layer be 0.3 µm or more and 3 µm or less, respectively. It is more preferably 0.4 µm or more and 2.5 µm or less, and even more preferably 0.5 µm or more and 2.0 µm or less.

In addition, the film thickness can be measured with an electronic micrometer K402B manufactured by Anritsu Corporation.

(Retardation Re and Rth)

The retardation Re and Rth of the optical film of the present invention are appropriately selected depending on the design of the liquid crystal cell and the optical film.

Re is,

It is preferable to satisfy 30 nm ≤ Re (550) ≤ 80 nm,

It is more preferable to satisfy 35 nm ≤ Re (550) ≤ 70 nm,

It is more preferable to satisfy 40 nm≦Re(550)≦65 nm.

Rth is,

It is preferable to satisfy 80 nm ≤ Rth (550) ≤ 150 nm,

It is more preferable to satisfy 90 nm ≤ Rth (550) ≤ 140 nm,

It is more preferable to satisfy 100 nm≦Rth (550)≦130 nm.

Re (550) represents the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) represents the thickness direction retardation of the optical film at a wavelength of 550 nm.

<Cellulose Acylate>

The cellulose acylate used in the present invention is not particularly limited. Raw materials for cellulose acylate include cotton linter and wood pulp (hardwood pulp, softwood pulp), etc., and cellulose acylate obtained from any raw material may be used. In some cases, cellulose acylate obtained from a plurality of raw materials may be mixed. You may use it. For example, Maruzawa, Utazer, "Plastic Materials Lecture (17) Fibrin-based Resin" Daily Industrial Newspaper (published in 1970) or Invention Association Publication No. 2001-1745 (Pages 7 to 8). Cellulose can be used.

The β-1,4 bonded glucose units constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of these hydroxyl groups are acylated by acyl groups. The average degree of acyl substitution means the ratio in which the hydroxyl groups of the cellulose positioned at the 2nd, 3rd and 6th positions are acylated (100% of acylation is substitution degree 1).

The method of measuring the degree of acetyl substitution can be performed according to D-817-91 of ASTM (American Association for Testing Materials).

In the present invention, the average degree of acyl substitution of the cellulose acylate of the core layer is 2.00 to 2.55, and the average degree of acyl substitution of the cellulose acylate of the first skin layer and the second skin layer is each independently 2.60 to 3.00.

The acyl group having 2 or more carbon atoms of the cellulose acylate in the present invention may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters and the like of cellulose, and may each have a group further substituted. Preferred examples of these are acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octade Canoyl group, isobutanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group, and the like. 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 particularly preferably Is an acetyl group, a propionyl group, or a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more particularly preferably an acetyl group (when the cellulose acylate is cellulose acetate).

In the acylation of cellulose, when an acid anhydride or an acid chloride is used as the acylating agent, an organic acid such as acetic acid or methylene chloride is used as the organic solvent serving as the reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (eg, CH ₃ CH ₂ COCl), a basic compound is used.

The most common industrial synthesis method of mixed fatty acid esters of cellulose is a method of acylating cellulose with fatty acids corresponding to acetyl groups and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or mixed organic acid components containing their acid anhydrides. .

The cellulose acylate used in the present invention can be synthesized, for example, by a method described in Japanese Patent Application Laid-Open No. Hei 10-45804. Moreover, as a cellulose acylate, a commercial item, such as L-70 (Daisel Corporation), LT-55 (Daisel Corporation), CA-394-60LF (Eastman Chemical Company), can also be used, for example.

(Polycondensation ester)

If desired, polycondensation ester can be added to the optical film of the present invention.

The polycondensation ester is a polycondensation ester of a dicarboxylic acid component and a diol component. The dicarboxylic acid component may be composed of only one type of dicarboxylic acid, or may be a mixture of two or more types of dicarboxylic acids. Among them, as the dicarboxylic acid component, it is preferable to use a dicarboxylic acid component containing at least one aromatic dicarboxylic acid and at least one aliphatic dicarboxylic acid. On the other hand, the diol component may also be composed of only one diol component, or a mixture of two or more diols. Among them, as the diol component, it is preferable to use ethylene glycol and/or an aliphatic diol having an average carbon atom number of more than 2.0 and not more than 3.0.

The ratio of the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid in the dicarboxylic acid component is preferably 5 to 100 mol%, more preferably 10 to 100 mol%, and 20 to 100 mol% of the aromatic dicarboxylic acid. It is more preferable that it is %.

Examples of the aromatic dicarboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8- Naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, etc. are contained, and phthalic acid and terephthalic acid are preferable. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and 1 ,4-cyclohexanedicarboxylic acid and the like are contained, and among them, succinic acid and adipic acid are preferable.

The diol component is ethylene glycol and/or a diol having an average carbon atom number of more than 2.0 and not more than 3.0. Among the diol components, it is preferable that ethylene glycol is 50 mol%, and it is more preferable that it is 75 mol%. Examples of the aliphatic diol include alkyldiol or alicyclic diol. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2 -Methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1, 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol , 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonane Diol, 1,10-decanediol, 1,12-octadecanediol, diethylene glycol, and the like, and these are preferably used together with ethylene glycol as a mixture of one or two or more.

The diol component is preferably ethylene glycol, 1,2-propanediol, and 1,3-propanediol, particularly preferably ethylene glycol and 1,2-propanediol.

Moreover, as a polycondensation ester, it is preferable that OH at the terminal of a polycondensation ester is a derivative of a polycondensation ester which forms an ester with a monocarboxylic acid. As monocarboxylic acids used for sealing both terminal OH groups, aliphatic monocarboxylic acids are preferable, acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof are preferable, and acetic acid or propionic acid is more preferable. And acetic acid is most preferred. When the number of carbon atoms of the monocarboxylic acids used at both ends of the polycondensation ester is 3 or less, the heating loss of the compound is not large, and it is possible to reduce the occurrence of planar failure. Moreover, you may mix 2 or more types of monocarboxylic acids used for sealing. It is preferable that both ends of the polycondensation ester are sealed with acetic acid or propionic acid, and a derivative of the polycondensation ester in which both ends of the polycondensation ester are made of acetyl ester residues is particularly preferable.

The number average molecular weight of the polycondensation ester is preferably 500 to 2000, more preferably 700 to 1500, and particularly preferably 700 to 1200. The number average molecular weight of the polycondensation ester is preferably 500 or more from the viewpoint of improving optical expression properties. In addition, if it is 2000 or less, compatibility with cellulose acylate increases, and bleed out hardly occurs during manufacture and during heating and stretching.

The number average molecular weight of the polycondensation ester can be measured and evaluated by gel permeation chromatography as described above in the present specification. In addition, when the terminal is a polyester polyol without a seal, it can also be calculated by the amount of hydroxyl groups per mass (hereinafter, hydroxyl value). As for the hydroxyl value, after acetylating the polyester polyol, the amount (mg) of potassium hydroxide required for neutralization of excess acetic acid is measured.

The polycondensation ester is, by a conventional method, a polyesterization reaction of a dicarboxylic acid component and a diol component, or a thermal melt condensation method by transesterification reaction, or an interfacial axis of an acid chloride of a dicarboxylic acid component and glycols. It can be easily synthesized by any of the legal methods. In addition, about polycondensation ester, there is a detailed description in Koichi Murai edition "The theory and application of plasticizers" (Saiwai Shobo Co., Ltd., first edition issued on March 1, 1987, first edition). In addition, Japanese Unexamined Patent Publication No. Hei 05-155809, Japanese Unexamined Patent Publication No. 05-155810, Japanese Unexamined Patent Publication No. Hei 5-197073, Japanese Unexamined Patent Publication No. 2006-259494, Japanese Unexamined Patent Publication No. 07-330670 , Materials described in JP 2006-342227 A, JP 2007-003679 A, etc. may also be used.

As a specific example of the polycondensation ester,

A polycondensation ester having a number average molecular weight of 1000 in which the dicarboxylic acid unit is terephthalic acid/succinic acid = 70/30, the diol unit is ethylene glycol/propylene glycol = 50/50, and the terminal is an acetyl group;

A polycondensation ester having a number average molecular weight of 950 in which the dicarboxylic acid unit is terephthalic acid/succinic acid = 45/55, the diol unit is ethylene glycol/propylene glycol = 50/50, and the terminal is an acetyl group;

A polycondensation ester having a number average molecular weight of 900 in which the dicarboxylic acid unit is terephthalic acid/succinic acid = 20/80, the diol unit is ethylene glycol/propylene glycol = 50/50, and the terminal is an acetyl group; And

A dicarboxylic acid unit is adipic acid, a diol unit is ethylene glycol/propylene glycol = 50/50, and a polycondensation ester having a number average molecular weight of 1000 in which the terminal is an acetyl group;

Can be used. The numerical values of dicarboxylic acids and diols represent molar ratios.

The optical film of the present invention preferably contains 1 to 9 parts by mass of a polycondensation ester (preferably, a polycondensation ester of an aromatic dicarboxylic acid and an aliphatic diol) with respect to 100 parts by mass of cellulose acylate, and 1 to It is more preferably 8 parts by mass, and even more preferably 1 to 7 parts by mass.

In the present invention, the polycondensation ester can be used as a plasticizer, but the polycondensation ester may also function as a retardation expressing agent.

(Sugar ester)

You may add a sugar ester to the protective film of this invention.

The specific examples and preferable ranges of [sugar ester] are as described in [0041 to 0056] of JP2011-94098.

(Retardation expression agent)

You may add a retardation expressing agent to the optical film of this invention. Although there is no restriction|limiting in particular as a retardation expressing agent, A rod-shaped compound, a disk-shaped compound, a compound represented by general formula (II-1) described later, etc. can be used. As a rod-like compound or a disk-like compound, it is preferable to use a compound having at least two aromatic rings.

When a rod-shaped compound is used, the amount of the rod-shaped compound added is preferably 0.1 parts by mass or more and less than 3 parts by mass, and more preferably 0.5 parts by mass or more and less than 2 parts by mass per 100 parts by mass of the cellulose acylate component. When using a disk-like compound or a compound represented by the general formula (II-1), the amount of the disk-like compound or the compound represented by the general formula (II-1) is preferably 0.1 to 10% by mass, respectively, based on the cellulose acylate. And, it is more preferable that it is 0.5-4 mass%, and it is especially preferable that it is 1-3 mass%.

Since the compound represented by the disk-like compounding and the general formula (II-1) is superior to the rod-like compound in terms of Rth retardation expression property, it is preferably used when a particularly large Rth retardation is required. You may use two or more types of retardation expressing agents together. It is preferable that the retardation expressing agent has a maximum absorption in the wavelength region of 250 to 400 nm, and it is preferable that the retardation expressing agent has substantially no absorption in the visible region.

Discuss the compound. As the discoid compound, a compound having at least two aromatic rings can be used. In this specification, the "aromatic ring" includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. It is particularly preferable that the aromatic hydrocarbon ring is a 6 membered ring (ie, a benzene ring).

Specific examples and preferable ranges of the "aromatic ring" are as described in paragraphs 0073 to 0077 of JP2013-75401A. In addition, the aromatic ring and the linking group may have a substituent, and specific examples of the substituent are as described in paragraphs 0078 to 0081 of JP2013-75401A.

It is preferable that the molecular weight of the disk-like compound is 300 to 800.

It is preferable to use a triazine compound represented by the following general formula (I) as a discoid compound.

[Formula 1]

In the above general formula (I):

Each of R ²⁰¹ independently represents an aromatic ring or a hetero ring having a substituent in at least any of the ortho position, the meta position, and the para position.

X ²⁰¹ each independently represents a single bond or -NR ²⁰² -. Here, R ²⁰² each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aromatic ring group, or a heterocyclic group.

The ^{aromatic ring represented by R 201} is preferably phenyl or naphthyl, and particularly preferably phenyl. The ^{aromatic ring represented by R 201} may have at least one substituent at any substitution position. Examples of the substituent include halogen atom, hydroxyl group, cyano group, nitro group, carboxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, alkenyloxy Carbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl substituted sulfamoyl group, alkenyl substituted sulfamoyl group, aryl substituted sulfamoyl group, sulfonamide group, carbamoyl, alkyl substituted carbamoyl group, alkenyl substituted carbamoyl group, Aryl substituted carbamoyl group, amide group, alkylthio group, alkenylthio group, arylthio group and acyl group are included.

It is preferable that the heterocyclic group represented by R ^{201 has aromaticity.} The aromatic heterocycle is generally an unsaturated heterocycle, and preferably a heterocycle having the largest number of double bonds. The hetero ring is preferably a 5-membered ring, a 6-membered ring, or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocycle is preferably a nitrogen atom, a sulfur atom, or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (as the heterocyclic group, 2-pyridyl or 4-pyridyl) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as those of the substituent of the aromatic ring.

In the case where X ²⁰¹ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valency at a nitrogen atom. The heterocyclic group having a free valency in the nitrogen atom is preferably a 5-membered ring, a 6-membered ring, or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 5-membered ring. The heterocyclic group may have a plurality of nitrogen atoms. Moreover, the heterocyclic group may have a hetero atom (for example, O, S) other than a nitrogen atom.

Although the ^{alkyl group represented by R 202} may be a cyclic alkyl group or a chain alkyl group, a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. The number of carbon atoms in the alkyl group is preferably from 1 to 30, more preferably from 1 to 20, still more preferably from 1 to 10, still more preferably from 1 to 8, and most preferably from 1 to 6. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (eg, a methoxy group, an ethoxy group), and an acyloxy group (eg, an acryloyloxy group, a methacryloyloxy group).

The ^{alkenyl group represented by R 202} may be a cyclic alkenyl group or a chain alkenyl group, but it is preferably a chain alkenyl group, and more preferably a linear alkenyl group than a branched chain alkenyl group. . The number of carbon atoms in the alkenyl group is preferably from 2 to 30, more preferably from 2 to 20, still more preferably from 2 to 10, still more preferably from 2 to 8, and most preferably from 2 to 6 Do. The alkenyl group may have a substituent. Examples of the substituent are the same as those of the aforementioned alkyl group.

The ^{aromatic ring group and the heterocyclic group represented by R 202} are the same as the aromatic ring and the hetero ring ^{represented by R 201} , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent are the same as those of the aromatic ring and heterocyclic ring of ^{R 201.}

The compound represented by the general formula (I) can be synthesized by a known method, such as the method described in JP 2003-344655 A. Details of the retardation expressing agent are described on page 49 of Publication 2001-1745.

It is also preferable to use a compound represented by the following general formula (II-1) as the disk-like compound. In addition, the compound represented by the following general formula (II-1) does not need to be in the form of a disk.

[Formula 2]

(In General Formula (II-1), Y ¹ represents a methine group or -N-. Ra ³¹ represents an alkyl group, alkenyl group, alkynyl group, aromatic ring group or heterocyclic group. Rb ³¹ , Rc ³¹ , Rd ³¹ and Re ³¹ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group Q ²¹ represents a single bond, -O-, -S-, or -NRf-, and Rf Represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group, and may form a ring by linking with ^{Ra 31. X 31} , X ³² , and X ³³ are each independently a single bond or a divalent Represents a linking group X ³⁴ is the following general formula (Q)

General formula (Q)

[Formula 3]

(In the general formula (Q), the * side is a linking site with an N atom substituted with a heterocycle in the compound represented by the general formula (II-1))

It shows a linking group selected from the group consisting of a divalent linking group represented by.)

The alkyl group, alkenyl group, aromatic cyclic group, or heterocyclic group in the general formula (II-1) has the same meaning as the alkyl group, alkenyl group, aromatic cyclic group, or heterocyclic group in the general formula (I).

As the compound represented by the general formula (II-1), the general formula (II-2), general formula (II-4), or general formula (II) described in paragraphs 0092 to 0095 of JP2013-75401A It is more preferable to represent by -5). Among them, it is particularly preferable to be represented by the following general formula (II-4).

[Formula 4]

(In General Formula (II-4), Y ⁴ represents a methine group or -N-. Ra ³⁴ represents an alkyl group, an alkenyl group, an alkynyl group, an aromatic cyclic group, or a heterocyclic group. Q ²⁴ represents a single bond,- Represents O-, -S-, or -NRf-, Rf represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group, or a heterocyclic group, ^{and may be connected to Ra 34} to form a ring. R ⁶¹ , R ⁶² , R ⁶³ and R ⁶⁴ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, a carbamoyl group, a sulfamoyl group, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkyl having 1 to 8 carbon atoms An amino group and a C1-C8 dialkylamino group are shown.)

<Other additives>

To the optical film of the present invention, a mat agent can be added as necessary. The mat agent is not particularly limited as long as it is a material exhibiting a function of preventing scratches or deterioration in transportability during handling, and an inorganic compound or an organic compound mat agent may be used.

As a preferable specific example of the mat agent of the inorganic compound, an inorganic compound containing silicon (e.g., silicon dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, etc.), titanium oxide, zinc oxide, aluminum oxide , Barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide, antimony, calcium carbonate, talc, clay, calcined kaolin, calcium phosphate, etc. are preferable, more preferably inorganic compounds containing silicon or oxidation Although it is zirconium, since the turbidity of a cellulose acylate film can be reduced, silicon dioxide is used especially preferably. As the fine particles of the silicon dioxide, for example, trade names such as aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) It is possible to use a commercial item having. As the fine particles of zirconium oxide, commercially available ones such as aerosil R976 and R811 (above manufactured by Nippon Aerosil Co., Ltd.) can be used.

As a preferable specific example of the mat agent of an organic compound, polymers, such as a silicone resin, a fluororesin, and an acrylic resin, are preferable, for example, and silicone resin is used especially preferably. Among the silicone resins, it is particularly preferable to have a three-dimensional network structure, and for example, Toss Pearl (registered trademark) 103, Toss Pearl 105, Toss Pearl 108, Toss Pearl 120, Toss Pearl 145, Toss Pearl 3120 and Toss Pearl 240 A commercial product having a brand name such as (manufactured by Toshiba Silicone Co., Ltd.) can be used.

The method of adding the mat agent to the cellulose acylate solution is not particularly limited. For example, an additive may be contained in the step of mixing the cellulose acylate and the solvent, or after preparing a mixed solution of the cellulose acylate and the solvent, the additive may be added. Furthermore, the mat agent may be added and mixed immediately before casting the dope, and the mixing can be carried out by installing a screw type mixer online. Specifically, a static mixer such as an in-line mixer is preferable, and as the in-line mixer, for example, a static mixer SWJ (Toray stationary in-pipe mixer Hi-Mixer) (manufactured by Tore Engineering) and the like is preferable. A preferred aspect of mixing of the mat agent is as described in Paragraph No. 0127 of JP2013-75401A.

In the optical film of the present invention, when at least one of the two skin layers contains a matting agent, abrasion resistance due to reduction of the friction coefficient of the film surface and creaking occurs when a wide-width film is wound in a long length. It is preferable from the viewpoint of prevention of rust prevention and film folding, and it is particularly preferable from the viewpoint of effectively reducing scratch resistance and creaking that a mat agent is contained in both of the two skin layers.

The content of the mat agent in the optical film of the present invention is preferably 0.01 to 5.0% by mass, more preferably 0.03 to 3.0% by mass, and particularly preferably 0.05 to 1.0% by mass. By setting it as the above range, it is possible to realize a creak reduction effect and abrasion resistance without increasing the haze of the optical film.

[Method of manufacturing optical film]

The manufacturing method of the optical film of the present invention comprises a dope for forming a core layer containing 1 to 9 parts by mass of polycondensation ester per 100 parts by mass of cellulose acylate, and 0 parts by mass or more of polycondensation ester based on 100 parts by mass of cellulose acylate. A dope for forming a first skin layer containing less than 0.05 parts by mass, and a dope for forming a second skin layer containing 0 parts by mass or more and less than 0.05 parts by mass of a polycondensation ester per 100 parts by mass of cellulose acylate, on a support. It includes a process of producing a film by covalent rolling. The above three types of dope may be multi-layered flexible simultaneously or sequentially on the support. In the production method of the optical film of the present invention, the covalent dope is dried to form a film, the film is peeled from the support, and the film after the peeling may be stretched.

(Preparation of dope)

In the present invention, an optical film can be produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent by a solution film production method.

The organic solvent preferably contains a solvent selected from an ether having 3 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and a halogenated hydrocarbon having 1 to 6 carbon atoms. . Ether, ketone, and ester may have a cyclic structure. A compound having two or more of the functional groups of ethers, ketones and esters (ie, -O-, -CO- and -COO-) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having a certain functional group.

Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetol. Included.

Examples of the ketone having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.

Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. It is preferable that the halogen of the halogenated hydrocarbon is chlorine. The ratio in which the hydrogen atom of the halogenated hydrocarbon is substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, still more preferably 35 to 65 mol%, and 40 to 60 mol% It is most preferred. Methylene chloride is a representative halogenated hydrocarbon.

You may mix and use two or more types of organic solvents.

The preparation of the solution can be carried out using a method and apparatus for preparing dope in a conventional solution film preparation method. Further, in the case of a general method, it is preferable to use halogenated hydrocarbons (especially methylene chloride) as the organic solvent.

It is preferable to adjust the amount of cellulose acylate so that it may contain 10 to 40 mass% in the solution obtained, and it is more preferable that it is 10 to 30 mass %. In the organic solvent, you may add arbitrary additives.

A solution can be prepared by stirring a cellulose acylate and an organic solvent at normal temperature (0-40 degreeC). The high-concentration solution may be stirred under pressure and heating conditions. Specifically, the cellulose acylate and the organic solvent are put into a pressurized container, sealed, and stirred under pressure while heating at a temperature above the boiling point of the solvent at room temperature and within a range in which the solvent does not boil. The heating temperature is usually 40°C or higher, preferably 60 to 200°C, and more preferably 80 to 110°C.

Each component may be roughly mixed in advance and then put into a container, or may be sequentially introduced into the container. The container needs to be configured to be able to stir. The container can be pressurized by injecting an inert gas such as nitrogen gas. Further, an increase in the vapor pressure of the solvent by heating may be used. Alternatively, after sealing the container, each component may be added under pressure.

In the case of heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. In addition, the entire container can be heated by installing a plate heater on the outside of the container and circulating the liquid through piping.

It is preferable to form a stirring blade inside the container, and to stir using this. It is preferable that the stirring blade has a length reaching the vicinity of the wall of the container. It is preferable to provide a scraper blade at the end of the stirring blade in order to renew the liquid film on the wall of the container.

Instruments, such as a pressure gauge and a thermometer, may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope may be taken out from the container after cooling, or may be cooled using a heat exchanger or the like after taking it out.

(Shared)

From the prepared cellulose acylate solution (dope), a cellulose acylate film can be produced by a solution membrane production method.

The dope is cast on a drum or band, and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 10 to 40% by mass. It is preferable to finish the surface of the drum or band in a mirror-finished state. For the casting and drying method in the solution membrane manufacturing method, U.S. Patent 2336310, U.S. Patent 2367603, U.S. Patent 2492078, U.S. Patent 2492977, U.S. Patent 2492978, U.S. Patent 2607704, U.S. Patent 2739069, U.S. Patent 2739070, British Patent 640731, British Patent 736892, Japanese Patent Publication No. 45-4554, Japanese Patent Publication No. 49-5614, Japanese Unexamined Patent Publication No. 60-176834, Japanese Unexamined Patent Publication No. 60-203430 , Japanese Laid-Open Patent Publication No. 62-115035 discloses.

In the present invention, the obtained cellulose acylate solution (dope) can be cast onto a smooth band or drum as a support to be formed into a film. As a method for producing the optical film of the present invention, a known covalent rolling method can be used. For example, a film may be prepared by flexing and laminating a cellulose acylate solution from a plurality of research plants installed at intervals in the direction of progression of the metal support, respectively. For example, Japanese Laid-Open Patent Publication No. 61-158414, Japan The method described in Unexamined Patent Publication No. Hei1-122419, Japanese Unexamined Patent Publication No. 11-198285, etc. can be used. In addition, a membrane may be produced by casting a cellulose acylate solution from two research studies, for example, Japanese Patent Application Publication No. 60-27562, Japanese Patent Application Publication No. 61-94724, and Japanese Patent Application Publication No. 61-947245. , JP-A 61-104813, JP-A 61-158413, and JP-A 6-134933 can be used. In addition, the flow of the high viscosity cellulose acylate solution described in Japanese Patent Application Laid-Open No. 56-162617 is wrapped with a low viscosity cellulose acylate solution, and the high viscosity and low viscosity cellulose acylate solution are simultaneously extruded. It may be a method. In addition, it is also preferable that the outer solution described in JP-A-61-94724 and JP-A 61-94725 contains more alcohol components, which are poor solvents, than the inner solution.

In addition, a film can also be produced by peeling the film molded on the metal support by the first flow research using two flow studies, and performing the second casting on the side that was in contact with the metal support surface (for example, For example, Japanese Patent Publication No. 44-20235).

In the manufacturing method of the optical film of the present invention, a cellulose acylate solution is covalently rolled to produce a cellulose acylate film of a skin layer/core layer/skin layer. The covalent dope is dried and can be peeled off from the support as a film.

(Drying process)

A method of drying the film which is dried on a drum or belt and peeled off is described. The film peeled off at the peeling position just before the drum or belt is conveyed by passing it alternately through a group of rolls arranged in a zigzag pattern, or by gripping both ends of the peeled film with a clip, etc. to make it non-contact. It is conveyed by a method or the like that is conveyed separately. Drying can be performed by a method in which air at a predetermined temperature is blown onto both sides of the film during transport, or a method using a heating means such as a microwave or the like. Since rapid drying may impair the flatness of the formed film, in the initial stage of drying, it is preferable to dry at a temperature such that the solvent does not foam, and to dry at a high temperature after drying proceeds. In the drying process after peeling from the support, the film is intended to shrink in the longitudinal direction or the width direction by evaporation of the solvent. The shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable in order to improve the flatness of the film. In this respect, for example, as shown in Japanese Laid-Open Patent Publication No. 62-46625, a method in which the entire process or a part of the drying process is carried out while maintaining the width of both ends of the web with clips or pins in the width direction. (Tenter method) is preferable. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, but may be appropriately selected according to the type and combination of the solvent used.

(Stretching)

In the present invention, after the covalent dope is dried and peeled from the support, the film can be stretched.

In the production method of the cellulose acylate film, it may be stretched in any direction of a film conveyance direction (hereinafter, also referred to as a film MD direction) and a direction orthogonal to the film conveyance direction (hereinafter, also referred to as a film TD direction), but at least the film TD Stretching in the direction is preferable from the viewpoint of expressing a desired retardation. Further, biaxial stretching in combination with stretching in a direction not coincident with the film TD direction (for example, the film MD direction) may be used. Moreover, extending|stretching may be performed in 1 stage and may be performed in multiple stages.

The optical film of this invention can perform biaxial stretching.

When performing biaxial stretching, after stretching in the film MD direction (transport direction), it is preferable to extend in the film TD direction (transport direction and orthogonal direction). When extending|stretching, you may contain a residual solvent, and you may extend|stretch in the state which does not contain a residual solvent. In the case of containing a residual solvent, it is preferable to extend the amount of the solvent between 0.1% by weight and 50% by weight based on the weight of the solid content of the film.

It is preferable that it is 0-20%, as for the elongation in extending|stretching in a film MD direction, it is more preferable that it is 0-15%, and it is especially preferable that it is 0-10%. The elongation rate of the cellulose acylate web at the time of stretching can be achieved by giving a difference between the film conveyance speed at the entrance of the stretching zone and the film conveyance speed at the exit. For example, when an apparatus having two nip rolls is used, the cellulose acylate film is preferably stretched in the MD direction by making the rotational speed of the nip roll on the outlet side faster than the rotational speed of the nip roll on the inlet side of the stretching zone. I can. In addition, "elongation rate (%)" means what is calculated|required by the following formula.

Elongation (%) = 100 × {(length after stretching)-(length before stretching)}/length before stretching

The elongation in stretching in the film TD direction is preferably more than 20%, more preferably more than 20% to 60% or less, particularly preferably 22 to 55%, more particularly 23 to 50% desirable. By performing such stretching, the expression of retardation can be adjusted.

The film surface temperature at the start of stretching is preferably 100°C or more and 220°C or less, and more preferably 120°C or more and 200°C or less.

In addition, in this invention, as a method of extending|stretching in the film TD direction, it is preferable to extend|stretch using a tenter device.

When stretching in the film TD direction, the residual solvent amount of the film at the time of starting of stretching is preferably 0% by mass or more and 3% by mass or less, more preferably 0% by mass or more and 2.3% by mass or less, and 0% by mass or more and 2.1% by mass It is more preferable that it is the following.

The amount of residual solvent can be represented by the following formula.

Residual solvent amount (mass%) = {(M-N)/N} × 100

Here, M is the mass at an arbitrary time point of a film (web), and N is the mass when the film which measured M was dried at 110 degreeC for 3 hours.

When stretching in the film TD direction, the film elastic modulus at the beginning of stretching is preferably 100 MPa or more and 1500 MPa or less, more preferably 100 MPa or more and 1000 MPa or less, still more preferably 100 MPa or more and 500 MPa or less, and 100 MPa or more It is particularly preferably 300 MPa or less.

The film elastic modulus was cut out from the center of the film 15 seconds before the stretching to be 10 mm in the film MD direction and 130 mm in the film TD direction, and using a Tensilon universal testing machine RTF series (manufactured by Orientec), the interchuck distance was 100 mm. It can be measured by making it so, and carrying out a tensile test at a tensile speed of 100 mm%/min.

[Polarizer]

The optical film of this invention can be used as a film for polarizing plates. The polarizing plate can be manufactured by bonding and laminating the optical film of the present invention on at least one surface of the polarizer. As the polarizer, a conventionally known one can be used, and for example, a hydrophilic polymer film such as a polyvinyl alcohol film is stretched by treating it with a dichroic dye such as iodine. The bonding of the cellulose acylate film and the polarizer is not particularly limited, but can be performed with an adhesive made of an aqueous solution of a water-soluble polymer. As the water-soluble polymer adhesive, a completely saponified polyvinyl alcohol aqueous solution is preferably used. The thickness of the polarizer is not particularly limited, but is generally 3 µm to 35 µm, preferably 5 µm to 25 µm, and more preferably 5 to 20 µm.

The optical film of the present invention is a configuration of a protective film/polarizer/protective film/liquid crystal cell/optical film/polarizer/protective film of the present invention, or a protective film/polarizer/optical film/liquid crystal cell/optical of the present invention. It can be preferably used in the constitution of a film/polarizer/protective film.

As the protective film, any one can be used as long as it has a function as a polarizing plate protective film. As a material constituting the polarizing plate protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, and the like is used. Specific examples of such a thermoplastic resin include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and (meth)acrylic. Resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. In addition, a polarizing plate protective film is usually bonded to a polarizer by an adhesive layer.

In the polarizing plate of the present invention, preferably, the optical film of the present invention, the polarizer, and the protective film are arranged in the above order, and the underwater curl of the optical film and the underwater curl of the protective film curl in the same direction. It is desirable to be. 4: in the polarizing plate in which the protective film 1, the polarizer 2, and the optical film 3 were laminated in this order, the direction of the underwater curl of the protective film 1 and the underwater curl of the optical film 3 Two aspects which are the same direction are shown.

(Wave curl)

The wave curl means that when the polarizing plate laminated in the order of a protective film, a protective film, a polarizer, an optical film, an adhesive, and a separate film is left standing in a high humidity environment, the end of the polarizing plate is absorbed, and the end of the polarizing plate is absorbed by moisture absorption expansion. It is a phenomenon that is deformed and becomes a wave shape.

When the thickness of the polarizer was 5 to 15 µm and the optical film stretched biaxially was used, it was found that the wavy curl of the polarizing plate was suppressed. The mechanism is not clear, but when the thickness of the polarizer is 5 to 15 µm, the expansion force is suppressed, and when an optical film stretched in two axes is used, the optical film is considered to have an action of suppressing expansion of the polarizer.

[Liquid crystal display device]

The polarizing plate of the present invention can be used for a liquid crystal display device in various display modes. The display modes of the liquid crystal display include TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Supper Twisted). Nematic), VA (Vertically Aligned), and HAN (Hybrid Aligned Nematic) display modes have been proposed, and the display mode of the liquid crystal display device of the present invention is not particularly limited. Particularly preferably, the liquid crystal display device of the present invention is a VA mode liquid crystal display device.

Example

The present invention will be described in more detail by the following examples, but the present invention is not limited by the examples.

<Cellulose acetate>

By the method described in JP-A-10-45804 and JP-A-8-231761, cellulose acetate was synthesized, and the degree of substitution thereof was measured. Specifically, sulfuric acid (7.8 parts by mass per 100 parts by mass of cellulose) was added as a catalyst, and a carboxylic acid serving as a raw material for an acyl substituent was added to perform an acylation reaction at 40°C. At this time, the degree of substitution of the acyl group was adjusted by adjusting the amount of acetic acid. Moreover, after acylation, it aged at 40 degreeC. Further, the low molecular weight component of this cellulose acetate was washed with acetone and removed. Table 1 shows the degree of substitution of the synthesized cellulose acetate.

<Preparation of Dope>

(Preparation of core layer dope solution C01)

The following composition was put into a mixing tank and stirred to dissolve each component to prepare a core layer dope solution C01.

Cellulose acetate CA01 (degree of substitution 2.43) 100 parts by mass

4.0 parts by mass of plasticizer E1

2.3 parts by mass of additive N1

394.0 parts by mass of methylene chloride

59.0 parts by mass of methanol

The solid content concentration was 19.0 mass%.

(Preparation of core layer dope solution C02 to C27)

Core layer dope solutions C02 to C27 were prepared in the same manner as in the case of preparing the core layer dope solution C01, except that the cellulose acetate, plasticizer and additives described in Table 2 were used in the amounts shown in Table 2. The amount of the solvent was appropriately adjusted so that the cellulose acetate concentration and the composition of the solvent were the same. The numerical value in the column of the addition amount in Table 2 represents parts by mass when the amount of cellulose acetate is 100 parts by mass.

[Formula 5]

[Formula 6]

(Preparation of skin layer dope solution S01)

The following composition was put into a mixing tank and stirred to dissolve each component to prepare a skin layer dope solution S01.

100 parts by mass of cellulose acetate CA02 (degree of substitution 2.81)

425.0 parts by mass of methylene chloride

63.0 parts by mass of methanol

(Dispersion of the mat solution)

The following composition was put into a disperser and stirred to dissolve each component to prepare a mat agent dispersion liquid M1.

2.0 parts by mass of silica particles having an average particle size of 20 nm

(AEROSIL (registered trademark) R972, manufactured by Nippon Aerosil Co., Ltd.)

76.1 parts by mass of methylene chloride

11.4 parts by mass of methanol

Skin layer dope solution S01 12.6 parts by mass

(Preparation of dope solution S01M)

To the skin layer dope solution S01 prepared above, the mat agent dispersion solution M1 was mixed in the ratio shown below to prepare a skin layer dope solution S01M.

Skin layer dope solution S01 100.0 parts by mass

7.1 parts by mass of mat dispersion M1

(Preparation of skin layer dope solution S02-S06)

Skin layer dope solutions S02 to S06 were prepared by the same method as the preparation of the skin layer dope solution S01, except that the cellulose acetate, plasticizer, and peeling accelerator described in Table 5 were used in the amounts described in Table 5. The amount of the solvent was appropriately adjusted so that the cellulose acetate concentration and the composition of the solvent were the same. The numerical value in the column of the addition amount in Table 5 represents parts by mass in the case where the amount of cellulose acetate is 100 parts by mass. The peeling accelerator K-37V represents Poem I (registered trademark) K-37V, manufactured by Riken Vitamin Co., Ltd.

(Preparation of skin layer dope solution S02M-S06M)

Skin layer dope solutions S02M to S06M to which the mat agent liquid was added were prepared by the same method as the preparation of the skin layer dope solution S01M, except for using the skin layer dope solution S02 to S06 instead of the skin layer dope solution S01.

<Membrane preparation of cellulose acetate film>

(softness)

The dope solutions C01 to C27 and S01M to S06M prepared above were used in the combinations shown in Table 6, and cast by a band casting machine.

When casting the dope solution, as shown in FIG. 1, as shown in FIG. 2, as shown in FIG. 2, the dope shown in the following Table 6 was co-cast from the casting die 89 on the moving band 85. Here, by adjusting the casting amount of each dope, the core layer was made the thickest, and consequently, the multilayer covalent flexible film 70 was formed so that the film thickness of the film after stretching became the value shown in Table 6 below.

Next, this casting film 70 was peeled off from the casting band 85, and after making it a wet film, it dried with a moving part and a tenter, and was set as a film. The amount of residual solvent immediately after peeling the dope was about 25% by mass. The film was sent to a drying room, and drying was sufficiently promoted during conveyance while being hung on a plurality of rollers.

(2-axis stretching)

The films obtained by casting (Examples 20 and 21) were stretched 10% in the MD (longitudinal) direction, and then held by a clip, and 40% stretched in the TD (transverse) direction under the condition of a fixed end uniaxial. At this time, the amount of residual solvent and the elastic modulus of the film at the start of TD stretching were as described in Table 7. The film elastic modulus at the start of stretching was adjusted by the film material, the amount of the residual solvent, and the temperature.

(TD 1-axis stretching)

The films obtained by casting (Examples 1 to 19, Comparative Examples 1 to 9) were gripped with a clip, and stretched 30% in the TD (transverse) direction under the condition of a fixed end 1 axis. At this time, the amount of residual solvent and the elastic modulus of the film at the start of stretching were as described in Table 7. The film elastic modulus at the start of stretching was adjusted by the film material, the amount of the residual solvent, and the temperature.

(Measurement of the elastic modulus of the film at the start of stretching)

The elastic modulus at the start of stretching was measured as follows. The film obtained by casting was cut out 15 seconds before stretching so as to be 10 mm in the MD (longitudinal) direction and 130 mm in the TD (transverse) direction from the center of the film. Using the Tensilon universal testing machine RTF series (manufactured by Orientec), the chuck distance was set to 100 mm, and a tensile test was performed at a tensile speed of 100 mm%/min.

With respect to the film obtained by casting, the film surface temperature at the start of stretching was measured using a thermocouple. An oven was installed in the tension part of the film of the Tensilon universal material tester, and the temperature of the oven was adjusted so that the temperature of the film surface at the start of the Tensilon measurement became the same as the temperature at the start of the stretching.

(Moist heat treatment)

Condensation prevention treatment, moist heat treatment (water vapor contact treatment), and heat treatment were sequentially performed on each film subjected to the stretching treatment.

In the condensation prevention treatment, dry air was supplied to each film, and the film temperature Tf0 was adjusted to 120°C.

In the wet heat treatment (water vapor contact treatment), the absolute humidity of the wet gas in the wet gas contact chamber (absolute humidity of the wet heat treatment) is 250 g/㎥, and the dew point of the wet gas is 10°C or more higher than the temperature Tf0 of each film. It adjusted so that it might become a temperature, and each film was conveyed, maintaining the state in which the temperature (moist heat treatment temperature) of each film became 100 degreeC for a treatment time (60 seconds).

In heat treatment, the absolute humidity (absolute humidity of heat treatment) in the heat treatment chamber is set to 0 g/㎥, the temperature of each film (heat treatment temperature) is set to the same temperature as the wet heat treatment temperature, and the treatment time (2 minutes) is maintained. I did. The film surface temperature was obtained by attaching a tape-type thermocouple surface temperature sensor (ST series manufactured by Anritsu Instruments Co., Ltd.) to the film at three points, and obtained from the average values of each.

(Winding up)

Then, after cooling to room temperature, each film was wound up, and for the purpose of judging its manufacturing suitability, a roll having a roll width of 1960 mm and a roll length of 3900 m was produced at least 24 rolls under the above conditions. A sample of 1 m in length (1,960 mm in width) was cut out at 100 m intervals per one roll of 24 continuously produced rolls to obtain films of each of the Examples and Comparative Examples, and measurements of curls at 25° C. 60% relative humidity and curls in water were performed. It was implemented as follows.

(Measurement method of curl at 25° C. 60% relative humidity)

The obtained film was cut out so as to be 35 mm x 3 mm in the 4 directions so that the MD direction was 0° and the interval was 45° (refer to FIG. 3 ). The four cut-out films were allowed to stand in an environment at 25° C. 60% for 30 minutes, and then the radius of curvature of the curl of the film was read. Further, the amount of curl on the long side (35 mm) cut out was read, and the value having the minimum radius of curvature was taken as the radius of curvature of the curl of the film.

(Measurement method of underwater curl)

The film was sampled in the same direction as the above 25° C. 60% relative humidity curl, immersed in 25° C. water for 30 minutes, and then the radius of curvature was read. Further, the amount of curl on the long side (35 mm) cut out was read, and the value having the minimum radius of curvature was taken as the radius of curvature of the curl of the film.

(Film retardation)

Measurement was made with an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Measuring Instrument Co., Ltd.) by the above method.

Table 7 shows the results of measuring 25° C. 60% relative humidity curl, underwater curl, Re (550) and Rth (550).

<Production of protective film>

(Preparation of the cellulose ester solution for the first skin layer and the second skin layer)

The following composition was put into a mixing tank, stirred while heating, and each component was dissolved to prepare a cellulose ester solution for a first skin layer and a second skin layer.

Composition of the cellulose ester solution for the first skin layer and the second skin layer:

Cellulose ester (acetyl substitution degree 2.86) 100 parts by mass

3 parts by mass of sugar ester compound of formula (I)

1 part by mass of sugar ester compound of formula (II)

2.4 parts by mass of ultraviolet absorber

Silica particle dispersion (average particle diameter 16 nm) 0.078 parts by mass

(AEROSIL (registered trademark) R972, manufactured by Nippon Aerosil Co., Ltd.)

339 parts by mass of methylene chloride

74 parts by mass of methanol

3 parts by mass of butanol

[Formula 7]

[Formula 8]

[Formula 9]

(Preparation of cellulose ester solution for core layer)

The following composition was put into a mixing tank, stirred while heating, and each component was dissolved to prepare a cellulose ester solution for a core layer.

Composition of cellulose ester solution for core layer

Cellulose ester (acetyl substitution degree 2.86) 100 parts by mass

7.7 parts by mass of sugar ester compound of formula (I)

2.3 parts by mass of sugar ester compound of formula (II)

2.4 parts by mass of ultraviolet absorber

266 parts by mass of methylene chloride

58 parts by mass of methanol

2.6 parts by mass of butanol

(Membrane production by covalent combustion)

As a casting die, an apparatus was used that was equipped with a feed block adjusted for covalent rolling, and made it possible to form a three-layered film. The cellulose ester solution for the first skin layer, the cellulose ester solution for the core layer, and the cellulose ester solution for the second skin layer were covalently rolled on a drum cooled to -7°C from a research study. At this time, the flow rate of each dope was adjusted so that the ratio of thickness might be 1st skin layer/core layer/second skin layer = 5/53/2.

It was cast on a mirror-finished stainless steel support, which was a drum having a diameter of 3 m. Dry air at 34° C. was blown on the drum at 270 m 3 /min.

Then, 50 cm from the end of the flexible part, the cellulose ester film that has been cast and rotated was peeled from the drum, and then both ends were clipped with a pin tenter. When peeling, 5% of stretching was performed in the MD direction.

The cellulose ester web held by the pin tenter was conveyed to the drying zone. In the initial drying, a 45 degreeC dry air was blown, and it dried at 110 degreeC for 5 minutes next. At this time, the cellulose-ester web was conveyed while extending|stretching at 10% of magnification in the width direction.

After the web was removed from the pin tenter, the portion held by the pin tenter was continuously cut out and dried at 145°C for 10 minutes while applying a 210 N tension in the MD direction. Further, the end portions in the width direction were continuously cut out so that the web had a desired width, and irregularities having a height of 10 µm were provided on both ends of the web width direction with a width of 15 mm to prepare a film having a thickness of 60 µm, and protective film 2A It was made into.

The curvature radius of the underwater curl of the protective film 2A prepared above was 50 mm.

<Manufacture of polarizing plate>

The surfaces of the optical films produced in Examples 1 to 21 and Comparative Examples 1 to 9 were subjected to alkali saponification treatment. It was immersed in 1.5 mol/L sodium hydroxide aqueous solution for 2 minutes at 45 degreeC, and it washed in a room temperature water washing bath, and neutralized with 0.05 mol/L sulfuric acid at 30 degreeC. Again, it washed in a room temperature water washing bath, and further dried with a 100°C warm air. Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 60 µm was continuously stretched five times in an aqueous iodine solution, and dried to obtain a polarizer having a thickness of 15 µm. A 3% by mass aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) was used as an adhesive to prepare a protective film 2A subjected to alkali saponification treatment in the same manner as the optical films of Examples and Comparative Examples in which the alkali saponification treatment was described above, and a polarizer It bonded together so that it might become between the optical film of an Example or a comparative example and the protective film 2A, and obtained the laminated body. At this time, the MD directions of the optical films of Examples or Comparative Examples and the protective film 2A were made parallel to the absorption axis direction of the polarizer.

An acrylic pressure-sensitive adhesive layer having a thickness of 15 µm was formed on the surface of the optical film side of Examples or Comparative Examples, and a separate film having a thickness of 38 µm was further bonded to the outside thereof. In the above polarizing plate, a 60 µm-thick protective film made of an acrylic pressure-sensitive adhesive layer and a polyethylene terephthalate film was bonded to the surface on the side of the protective film 2A to prepare a polarizing plate.

When an optical film of an Example or Comparative Example, a polarizer, and a protective film 2A were arranged in the vertical direction, when the protective film 2A was viewed from the top, the underwater curl of the optical film and the protective film 2A was convex. The case where a positive curl and the bottom were convex was made into a negative curl.

(The end of the polarizing plate is folded)

When the polarizing plate was manufactured as described above, the frequency of occurrence of folding of the ends was observed. A polarizing plate was produced at 1000 m, and evaluated according to the following criteria.

1: does not occur

2: Occurs, but evaluation of the polarizing plate is possible

3: Occurs, and evaluation of the polarizing plate is impossible

(Evaluation of polarizing plate curl)

The polarizing plate prepared above was punched into a rectangle having a long side direction of 1150 mm and a short side direction of 645 mm. At this time, the absorption axis of the polarizer was made to be in the long side direction. After leaving the punched polarizing plate for 7 days in an environment at 23°C and 55% relative humidity, the separate film was peeled off to evaluate curl.

The polarizing plate from which the separate film was peeled off was allowed to stand on a flat surface in the direction in which the lower surface becomes convex, and the heights of excitation at the four corners and the center of each side were measured, and the maximum value of the absolute value was taken as the polarizing plate curl value.

Here, the polarizing plate curl is positive (+) indicates a convex curl toward the protective film side (that is, the protective film side), and the polarizing plate curl negative (-) indicates the pressure-sensitive adhesive side (that is, the first optical film) from which the separate film is peeled off. Side) shows that it is a convex curl.

Table 8 shows the results of the above evaluation.

In the polarizing plate using the optical films of Examples 1-6 and 9-21 in which the radius of curvature of the 25 degreeC 60% relative humidity curl was larger than 30 mm, the evaluation of the edge folding at the time of polarizing plate manufacture was 1, and was especially excellent. In the polarizing plate using the optical films of Examples 7 and 8 in which the radius of curvature of the 25° C. 60% relative humidity curl was greater than 25 mm and not more than 30 mm, the evaluation of the edge folding at the time of manufacturing the polarizing plate was 2, which was good. On the other hand, in the polarizing plate using the optical films of Comparative Examples 3 and 6 in which the radius of curvature of the curl at 25° C. 60% relative humidity was 25 mm or less, the evaluation of the edge folding at the time of manufacturing the polarizing plate was 3 and was defective.

(Evaluation of wave curl)

The polarizing plate prepared above was punched into a rectangle having a long side direction of 1150 mm and a short side direction of 645 mm. At this time, the absorption axis of the polarizing plate was made parallel to the short side. After allowing the punched polarizing plate to stand on a flat surface for 24 hours in an environment of 55% relative humidity at 23° C. so that the separator film faces down, the point of excitation from the flat surface on the four sides of the polarizing plate is set as a wave, and from the flat surface of each wave The maximum value of the amount of excitation of was taken as the height of the wave, and was measured using straight silver (manufactured by Shinwa Measurement Co., Ltd.). The measurement of the height of each wave on each side of the polarizing plate was performed in a state in which the separate film was left standing so as to be downward, and in a state where the separate film was left standing so as to be above.

The point where the height of the wave is 1 mm or more was measured as 1 wave, and the number of waves of each side of the polarizing plate and the height of the wave were measured. The measurement results are shown in the table below. Among the number of waves of each side, the maximum value is called "wave number", and the maximum wave height among the total measurement results is called "wave height". If the wave height is 3 mm or less and the wave number is 3 or less, there is no practical problem.

The polarizing plate 20 and the polarizing plate 21 using the biaxially stretched optical film were compared with the polarizing plate 1 and the polarizing plate 2 using the TD uniaxially stretched optical film, and both the wave height and the wave number were good.

<Liquid crystal display device>

(Manufacture of liquid crystal display device)

Using two polarizing plates of the above-described Examples and Comparative Examples, the pressure-sensitive adhesive side (that is, the optical film side of the Example or Comparative Example) is the liquid crystal cell side, and the absorption axis of each polarizing plate is affixed to the VA liquid crystal cell so that the absorption axis is orthogonal, Liquid crystal displays of Examples and Comparative Examples were manufactured. The VA liquid crystal cell was used by peeling off the front and back polarizing plates and retardation plates of a commercially available VA mode liquid crystal display device (LC-52G7, manufactured by Sharp Corporation).

(Evaluation of oblique light leakage)

The manufactured liquid crystal display device was measured using a measuring instrument (EZ-Contrast XL88, manufactured by ELDIM) to measure the black luminance at a polar angle of 60 degrees and an azimuth angle of 45 degrees of the liquid crystal display in a black display state in a dark room. Evaluated.

1: 0.5 cd/m² or less

2: Exceeding 0.5 cd/m² and less than 1.0 cd/m²

3: More than 1.0 cd/m² and less than 1.5 cd/m²

4: Exceeding 1.5 cd/㎡ and below 2.0 cd/㎡

5: Exceeds 2.0 cd/㎡

1 to 3 has no practical problem, and 4 to 5 has a large light leakage and has a problem in practical use.

(End light leakage after 1000 hours at 50°C 90% relative humidity)

The liquid crystal cell to which the polarizing plates of Examples and Comparative Examples were bonded was taken out after being left in a constant temperature layer in a 50°C 90% relative humidity environment for 1000 hours, and the black luminance observed from the front of the liquid crystal display in a black display state in a dark room was measured using a measuring instrument ( Measurement was made using EZ-Contrast XL88, manufactured by ELDIM). The position of 3 cm from the edge of the 4 sides of the screen was measured at 4 centers of the top, bottom, left and right, and the maximum value was taken as the end light leakage, and the following criteria were evaluated.

1: 0.2 cd/m² or less

2: Exceeding 0.2 cd/m2 and less than 0.3 cd/m2

3: Exceeding 0.3 cd/m² and less than 0.4 cd/m²

4: Exceeding 0.4 cd/m² and less than 0.5 cd/m²

5: exceeds 0.5 cd/m2

1 to 3 has no problem in practical use, and in 4 to 5, there is a problem in practical use because light leakage is conspicuous.

Table 10 shows the results of the above evaluation.

(Summary of Examples)

Liquid crystal displays 1 to 4, 17, 20, and 21 in which the curvature radius of the underwater curl of the film is 10 mm or more and 20 mm or less, and the polarizing plate curl is -5 mm or more and 5 mm or less, ends after 1000 hours at 50° C. 90% relative humidity The evaluation of light leakage was 1, which was particularly excellent.

Liquid crystal displays 5 to 16, 18 and 19 in which the curvature radius of the underwater curl is 20 mm or more and 25 mm or less, and the polarizing plate curl is -10 mm or more and -5 mm or less, or 5 mm or more and 10 mm or less, 50° C. 90% relative humidity. The evaluation of the end light leakage after 1000 hours was 2 or 3, which was good.

On the other hand, the curvature radius of the underwater curl is larger than 25 mm, the polarizing plate curl is smaller than -10 mm, or the liquid crystal display devices 22 to 27 larger than 10 mm are evaluated for end light leakage after 1000 hours at 50°C 90% relative humidity. Was 4 or 5, and was defective.

In addition, liquid crystal displays 1 to 17, 20, and 21 in which the underwater curl of the optical film and the underwater curl of the protective film in the polarizing plate are curled in the same direction show good results, and in the polarizing plate, the underwater curl of the optical film and protection Liquid crystal displays 18 and 19 in which the underwater curl of the film was curled in different directions were also acceptable levels.

In the optical film of Example 5, the amount of polycondensation polyester is slightly large, and the amount of polycondensation polyester in the optical film of Example 6 is slightly small, and curls in water are slightly inferior, but there is no problem in practical use.

The optical film of Example 7 did not contain a plasticizer, the optical film of Example 8 contained an aliphatic polycondensed polyester, and the optical film of Example 9 contained an aromatic polycondensed polyester having a low aromatic ratio. By doing so, the curls in the water slightly fall, but there is no problem in practical use.

The optical film of Example 10 has a slightly thick overall film thickness, and the optical film of Example 11 has a slightly thick skin layer, so that curls at 25° C. 60% relative humidity and curls in water are slightly inferior, but there is no problem in practical use. .

The optical film of Example 14 contained a plasticizer in the skin layer, so that the curls in water slightly fell, but practically there was no problem.

The optical film of Example 15 has a slightly high average degree of acyl substitution, and the optical film of Example 16 has a slightly low average degree of acyl substitution, and the curl in water is slightly inferior, but there is no problem in practical use.

70 flexible membrane
85 flexible band
89 flexible die
120 core layer dope
121 Dope for the first skin layer
122 Dope for the second skin layer
120a core layer
121a first skin layer
122a second skin layer
150 die for the second skin layer (support layer)
151 Die for core layer (base layer)
152 Die for the first skin layer (air side layer)

Claims (20)

As a method of manufacturing an optical film,
A dope for forming a core layer containing 1 to 9 parts by mass of a polycondensation ester with respect to 100 parts by mass of cellulose acylate;
A dope for forming a first skin layer containing 0 parts by mass or more and less than 0.05 parts by mass of a polycondensation ester based on 100 parts by mass of cellulose acylate,
A step of producing a film by covalently rolling a dope for forming a second skin layer containing 0 parts by mass or more and less than 0.05 parts by mass of a polycondensation ester based on 100 parts by mass of cellulose acylate, and further Including a process of stretching a furnace film,
The residual solvent amount of the film at the start of stretching is 0% by mass or more and 3% by mass or less, and the tensile modulus of the film at the start of stretching is 100 MPa or more and 1500 MPa or less, and the stretching is carried out in a direction orthogonal to the film transport direction. Become,
The optical film
A core layer containing cellulose acylate having an average degree of acyl substitution of 2.00 to 2.55, and
On one surface of the core layer, a first skin layer containing a cellulose acylate having an average degree of acyl substitution of 2.60 to 3.00 is provided,
On the other surface of the core layer, a second skin layer containing cellulose acylate having an average degree of acyl substitution of 2.60 to 3.00 is provided,
The film thickness of the entire optical film is 3 µm or more and 55 µm or less, and the thickness of the first skin layer and the second skin layer is 0.3 µm or more and 5 µm or less, respectively,
Method of manufacturing an optical film. The method of claim 1,
The method for producing an optical film in which the amount of the residual solvent is 0% by mass or more and 2.1% by mass or less. The method of claim 1,
The method for manufacturing an optical film, wherein the overall film thickness of the optical film is 3 µm or more and 50 µm or less, and the first skin layer and the second skin layer each have a thickness of 0.3 µm or more and 3 µm or less. The method according to any one of claims 1 to 3,
The method for producing an optical film, wherein the core layer contains 1 to 9 parts by mass of polycondensation ester with respect to 100 parts by mass of cellulose acylate. The method according to any one of claims 1 to 3,
The manufacturing method of an optical film in which the said optical film satisfies following Formula 1 and following Formula 2;
Equation 1: 30 ㎚ ≤ Re (550) ≤ 80 ㎚
Equation 2: 80 ㎚ ≤ Rth (550) ≤ 150 ㎚
However, Re (550) represents the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) represents the retardation in the thickness direction of the optical film at a wavelength of 550 nm. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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