WO2012133169A1

WO2012133169A1 - Liquid crystal display device

Info

Publication number: WO2012133169A1
Application number: PCT/JP2012/057488
Authority: WO
Inventors: 範江谷原; 村上　隆
Original assignee: コニカミノルタアドバンストレイヤー株式会社
Priority date: 2011-03-31
Filing date: 2012-03-23
Publication date: 2012-10-04
Also published as: JPWO2012133169A1

Abstract

The present invention provides a liquid crystal display device with high front contrast. A liquid crystal display device is provided in which contrast variations and color shifts caused by polarizing plate protective films are not distinguishable and in which no crosstalk is generated in a three-dimensional (3D) image display device when images are observed with one's head inclined. This liquid crystal display device has a viewing side polarizing plate, VA mode liquid crystal cells, and a back light side polarizing plate and is characterized by a polarizing plate protective film positioned on the viewing side of the viewing side polarizing plate being a λ/4 plate and one of the two polarizing plate protective films positioned so as to sandwich the VA mode liquid crystal cells being a film that satisfies prescribed requirements.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device. More specifically, in a liquid crystal display device with a high aperture ratio and high front contrast, the unevenness of contrast due to the polarizing plate protective film is not noticeable, and in a stereoscopic (3D) image display device, when the image is observed with the neck tilted The present invention relates to a liquid crystal display device that does not generate crosstalk.

In recent years, a stereoscopic (3D) video display device using a liquid crystal display device has been actively developed, and a λ / 4 plate, which is an optical film, is used for 3D viewing glasses and a viewing side surface of a stereoscopic (3D) video display device. For this reason, a system for viewing stereoscopic images has been studied. However, the field of view tends to be darkened by wearing the 3D viewing glasses, and it is required to increase the contrast of the stereoscopic (3D) video display device.

On the other hand, in order to improve the required display quality of the liquid crystal display device, various devices and methods are used for the liquid crystal cell. For example, Super Patterned VA mode (S-PVA mode), Polymer Stabilized VA mode (PSVA mode), Color Filter On Array (COA), and the like. Due to the improvements in these liquid crystal cells, the response speed was fast and the image became clear. For example, when COA is used, it is known that an increase in the aperture ratio increases the amount of light transmitted through the cell and increases the front contrast.

However, for example, in the case of a liquid crystal display device combined with the S-PVA mode and the COA, the amount of light transmitted through the liquid crystal cell is increased and the front contrast is increased, but this is caused by the polarizing plate protective film used for the polarizing plate. Contrast unevenness is easily noticeable, and the increase in these unevenness appears as crosstalk when observing the image with the head tilted in a stereoscopic (3D) video display device, and the visibility needs to be improved. .

Patent Document 1 discloses a technique in which the front contrast is increased and the color shift is improved by the configuration of the retardation film used on the liquid crystal cell side of the VA mode liquid crystal display device. However, when applied to a liquid crystal display device employing a device or method for improving the display quality described above, contrast unevenness, color shift, and crosstalk when observing an image with a neck tilted in a stereoscopic (3D) image display device. Problems are not improved.

JP 2010-54736 A

The present invention has been made in view of the above-described problems and situations, and the problem to be solved is that in a liquid crystal display device having a high aperture ratio and high front contrast, unevenness in contrast and color shift due to the polarizing plate protective film are conspicuous. First, it is to provide a liquid crystal display device that does not generate crosstalk when a stereoscopic (3D) video display device is tilted to observe the video.

In order to solve the above problems, the present inventor has a viewing side polarizing plate, a VA mode type liquid crystal cell, and a backlight side polarizing plate in this order from the viewing side in the process of studying the cause of the above problem and the like. The polarizing plate protective film located on the viewing side is a λ / 4 plate, and the two polarizing plate protective films located between the VA mode type liquid crystal cells have a specific retardation. It has been found that the above problems can be solved by the liquid crystal display device as described above, and the present invention has been achieved.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. A viewing side polarizing plate having a structure in which a polarizer is sandwiched between two polarizing plate protective films, a VA mode type liquid crystal cell, and a backlight side polarizing having a structure in which a polarizer is sandwiched between two polarizing plate protective films A liquid crystal display device having plates in this order from the viewing side, wherein the polarizing plate protective film located on the viewing side of the viewing side polarizing plate is a λ / 4 plate, and is located across the VA mode type liquid crystal cell One of the two polarizing plate protective films is a film having a retardation represented by the following requirement (1), and the other polarizing plate protective film is a retardation represented by the following requirement (2) A liquid crystal display device, characterized by being a film having

(1) The in-plane retardation value Ro (590) defined by the following formula (I) is in the range of 20 to 150 nm, and the retardation value in the thickness direction is defined by the following formula (II). Rt (590) is in the range of 220 to 400 nm.

(2) In-plane retardation value Ro (590) defined by the following formula (I) is in the range of 0 to 10 nm, and the retardation value in the thickness direction is defined by the following formula (II). Rt (590) is in the range of −15 to 15 nm.

Formula (I): Ro (590) = (n _x −n _y ) × d (nm)
Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d (nm)
(In the formula, Ro (590) represents the retardation value in the in-plane direction of the film at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm, and Rt (590) represents a temperature of 23 ° C. and a relative humidity of 55% RH. Represents the retardation value in the thickness direction of the film at a measurement wavelength of 590 nm, and d represents the thickness (nm) of the polarizing plate protective film.

n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film, n _y is in the plane direction of the film, the refractive index in the direction y perpendicular to the direction x, n _z Represents the refractive index in the thickness direction z of the film. Each refractive index is measured at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm. )
2. Of the two polarizing plate protective films positioned across the VA mode type liquid crystal cell, the polarizing plate protective film positioned on the viewing side with respect to the liquid crystal cell satisfies the requirement (1). 2. A liquid crystal display device according to item 1.

3. 3. The liquid crystal display device according to item 2, wherein the polarizing plate protective film contains cellulose acetate having an acetyl group substitution degree X of 2.0 ≦ X <2.7.

4. Of the two polarizing plate protective films located across the VA mode type liquid crystal cell, the polarizing plate protective film located on the backlight side with respect to the liquid crystal cell includes a cellulose ester resin and an acrylic resin, The liquid crystal display device according to any one of the first to third items.

5. 5. The liquid crystal display device according to any one of items 1 to 4, wherein the VA mode type liquid crystal cell is an SPVA mode type.

6. 6. The liquid crystal display device according to any one of items 1 to 5, wherein an aperture ratio of the liquid crystal display device is 65% or more.

7. 7. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a color filter on array (COA) structure.

8. Of the two polarizing plate protective films constituting the backlight side polarizing plate, the polarizing plate protective film located on the backlight side is a brightness enhancement film. The liquid crystal display device according to any one of the above.

According to the present invention, in a liquid crystal display device with a high aperture ratio and a high front contrast, contrast unevenness and color shift caused by the polarizing plate protective film are not noticeable, and the neck is tilted in a stereoscopic (3D) image display device to display an image. It is possible to provide a liquid crystal display device that does not generate crosstalk when observed.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

In the application example of the conventional retardation film, the retardation value Ro (590) in the in-plane direction is in the range of 20 to 70 nm, and the retardation value Rt (590) in the thickness direction is in the range of 70 to 200 nm. The retardation film is disposed on both sides of the liquid crystal cell to expand the viewing angle, but the retardation film does not necessarily have a uniform retardation over the entire film surface. There was a tendency that the unevenness of the two retardation films interfered with each other to increase the unevenness of contrast. In particular, the unevenness of the retardation film positioned on the backlight side with respect to the liquid crystal cell is considered to have a great influence because it causes unevenness in the incident light to the liquid crystal cell.

Further, when a λ / 4 plate is used on the viewing side surface of the liquid crystal display device, the phase difference unevenness of the λ / 4 plate itself is added. However, in the liquid crystal display device having high contrast, the unevenness of the retardation film cannot be ignored, and the influence on the unevenness of contrast and the color shift becomes large. In addition, in the stereoscopic (3D) video display device, a new problem has arisen that crosstalk is likely to occur when the video is tilted and observed.

Therefore, when using a λ / 4 plate for the polarizing plate protective film on the viewing side of the liquid crystal display device, one of the two polarizing plate protective films located across the liquid crystal cell is a film having a higher retardation than the conventional one, By making the other film a film having little retardation, it is considered that the unevenness between the films having the retardation can be prevented from interfering and expanding, and the unevenness can be reduced. Furthermore, it is considered that the non-uniformity incident light can be given to the liquid crystal cell by positioning the film having no phase difference on the backlight side, and further, the overall contrast unevenness can be reduced. .

Example of configuration of liquid crystal display device having VA mode type liquid crystal cell of the present invention Conceptual diagram showing an example of a configuration of a conventional liquid vertical alignment type (VA type) liquid crystal display device Schematic diagram showing oblique stretching with a tenter Schematic diagram of a 3D image display device (system with one polarizing plate for glasses) Schematic diagram of stereoscopic image display device (system with two polarizing plates for glasses)

Hereinafter, modes for carrying out the present invention will be described in detail, but the present invention is not limited to these.

In the liquid crystal display device of the present invention, a viewing side polarizing plate having a structure in which a polarizer is sandwiched between two polarizing plate protective films, a VA mode type liquid crystal cell, and a polarizer is sandwiched between two polarizing plate protective films. A liquid crystal display device having a backlight side polarizing plate having a structure in this order from the viewing side, wherein the polarizing plate protective film positioned on the viewing side of the viewing side polarizing plate is a λ / 4 plate, and the VA mode One of the two polarizing plate protective films located across the liquid crystal cell is a film having a retardation expressed by the following requirement (1), and the other polarizing plate protective film has the following requirements (2 ) Is a film having a retardation represented by.

(1) The in-plane retardation value Ro (590) defined by the formula (I) is in the range of 20 to 150 nm, and the retardation value in the thickness direction is defined by the formula (II). Rt (590) is in the range of 220 to 400 nm.

(2) The in-plane retardation value Ro (590) defined by the formula (I) is in the range of 0 to 10 nm, and the thickness direction retardation value is defined by the formula (II). Rt (590) is in the range of −15 to 15 nm.

This feature is a technical feature common to the inventions according to claims 1 to 8.

As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, of the two polarizing plate protective films positioned with the VA mode liquid crystal cell in between, the polarizing plate positioned on the viewing side with respect to the liquid crystal cell When the protective film satisfies the requirement (1), it reduces contrast unevenness and color shift, and remarkably suppresses the occurrence of crosstalk when the head is tilted and observed in a stereoscopic (3D) video display device. Preferred above.

In addition, it is preferable that the polarizing plate protective film contains at least cellulose acetate having an acetyl group substitution degree X of 2.0 ≦ X <2.7.

Moreover, the polarizing plate protective film located in the backlight side with respect to a liquid crystal cell among two polarizing plate protective films located on both sides of the said VA mode type liquid crystal cell may contain a cellulose ester resin and an acrylic resin. From the viewpoint of obtaining a retardation film satisfying the requirement (2).

The VA mode type liquid crystal cell is preferably an SPVA mode type, the liquid crystal display device has an aperture ratio of 65% or more, and the liquid crystal display device has a color filter on array (COA) structure. Is preferable from the viewpoint of improving visibility and contrast.

Of the two polarizing plate protective films constituting the backlight side polarizing plate, the polarizing plate protective film located on the backlight side is preferably a brightness improving film from the viewpoint of improving the contrast.

Hereinafter, the present invention will be described in detail.

<Configuration of liquid crystal display device>
FIG. 1 shows an example of the configuration of a liquid crystal display device having a VA mode type liquid crystal cell of the present invention, but the present invention is not limited to this.

The polarizing plate according to the present invention has a structure in which polarizers 1 and 10 are sandwiched between two polarizing plate protective films, and a viewing side polarizing plate is provided on both sides of a liquid crystal cell 15 having a VA mode type liquid crystal 5. 13 and a backlight side polarizing plate 14 are arranged.

The polarizing plate

protective films

2, 3, 9, and 11 according to the present invention are referred to as polarizing plate protective films T1, T2, T3, and T4, respectively, in order to distinguish them. The polarizing plate protective film T1 according to the present invention is a λ / 4 plate, and the polarizing plate protective films T2 and T3 are polarizing plate protective films satisfying the above requirements (1) and (2).

The liquid crystal cell 15 is filled with VA mode type liquid crystal 5 between the

transparent substrates

4 and 8, and the color filter 6 and the thin film transistor 7 are installed on the backlight 12 side of the liquid crystal cell, and this structure is a color filter on array (COA). It is called. The backlight 12 may be a cold cathode tube or an LED, but is preferably an LED for improving the contrast.

The VA mode type liquid crystal display device is preferably an SPVA mode type. The SPVA mode has a common electrode layer patterned on a color filter substrate and a pixel electrode layer patterned on an array substrate to define multiple domains. A wide viewing angle can be secured by forming a fringe field and uniformly dispersing the tilting direction of the liquid crystal in various directions. Generally, it is assumed that the rising time is intermediate and the rising time is slow, and an afterimage is confirmed when DCC (acceleration method) is applied. SPVA forms two separated pixel electrode regions (main pixel and sub-pixel) having different pixel voltages in one pixel region, and is an excellent method for widening the viewing angle while maintaining high contrast.

The COA method includes, for example, a color filter integrated drive substrate in which a color filter is directly formed on a drive side substrate of a liquid crystal cell, and a counter electrode (conductive layer) as described in JP-A-10-206888. ) And a counter substrate with a spacer interposed therebetween, and a liquid crystal material is sealed in the gap, and a color filter is formed on the reflective electrode, and a bonding margin is provided in high definition. The yield and aperture ratio can be improved by widening. The aperture ratio of the liquid crystal display device of the present invention is preferably 65% or more depending on the configuration of the COA method.

Incidentally, FIG. 2 shows the structure of a conventional liquid crystal display device in which a color filter and a thin film transistor are arranged on different transparent substrates, and the aperture ratio is about 50 to 55%.

Although not shown, a light guide plate, a light diffusion film, a brightness enhancement film, etc. may be disposed between the backlight 12 and the backlight side polarization plate 14, and the polarization plate protective film T4 is a brightness enhancement film. Is also a preferred embodiment.

<Polarizing plate protective films T2, T3>
First, the two polarizing plate protective films T2 and T3 positioned with the VA mode type liquid crystal cell according to the present invention interposed therebetween will be described.

The polarizing plate protective film T2 and T3 according to the present invention are preferably resin films, for example, cellulose such as triacetyl cellulose film, cellulose acetate propionate film, cellulose diacetate film, cellulose acetate butyrate film, etc. Ester film, Polyester film such as polyethylene terephthalate, Polyethylene naphthalate, Polycarbonate film, Polyarylate film, Polysulfone (including polyethersulfone) film, Polyethylene film, Polypropylene film, Cellophane, Polyvinylidene chloride film, Polyvinyl Alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, norbornene Resin film, a polymethylpentene film, a polyether ketone film, polyether ketone imide film, a polyamide film, a fluorine resin film, nylon film, can be used cycloolefin polymer film, a polymethylmethacrylate film, or an acrylic film. Among these, a cellulose ester film is a preferable resin film from the viewpoint of optical properties, physical properties, and suitability for producing a polarizing plate with a saponification treatment.

<Cellulose ester film>
The polarizing plate protective films T2 and T3 according to the present invention are polarizing plate protective films that satisfy the following requirements (1) and (2), and are cellulose ester films from the viewpoint of optical properties, physical properties, handleability, and productivity. It is preferable. (Hereinafter, the polarizing plate protective film according to the present invention may be referred to as a cellulose ester film.)
(1) The in-plane retardation value Ro (590) defined by the following formula (I) is in the range of 20 to 150 nm, and the retardation value in the thickness direction is defined by the following formula (II). Rt (590) is in the range of 220 to 400 nm.

The preferable range of the retardation value Ro is in the range of 30 to 100 nm, more preferably in the range of 35 to 70 nm. A preferred range for Rt is in the range of 250 to 350 nm. When the retardation is within the above range, both reduction in contrast unevenness and expansion of the viewing angle can be achieved.

The preferable range of the retardation value Ro is in the range of 0 to 5 nm, and the preferable range of Rt is in the range of −5 to 5 nm. When the retardation is within the above range, the unevenness of incident light to the liquid crystal cell is reduced, which contributes to the effect of reducing contrast unevenness and color shift.

n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film, n _y is in the plane direction of the film, the refractive index in the direction y perpendicular to the direction x, n _z Represents the refractive index in the thickness direction z of the film. Each refractive index is measured at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm. )
The retardation can be obtained by measuring an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.).

Although there is no restriction | limiting which polarizing plate protective film T2 and T3 satisfy | fill the said requirements (1) and (2), The polarizing plate protective film T2 arrange | positioned in the position far from a backlight side satisfy | fills the said requirement (1). It is preferable from the viewpoint of making the contrast unevenness less noticeable.

In order to give retardation within the above range, the types and addition amounts of cellulose esters and other resins, the types and addition amounts of additives such as plasticizers, the types and addition amounts of retardation increasing agents, the types of retardation reducing agents And the amount added, and the conditions of the stretching treatment during film formation can be controlled.

(Cellulose ester)
The cellulose ester used for the polarizing plate protective films T2 and T3 according to the present invention preferably has an average degree of acetyl group substitution of the whole cellulose ester ≧ 1.9.

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

The cellulose ester used in the present invention is not particularly limited as long as the acetyl group substitution degree is satisfied, but the cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an aromatic carboxylic acid ester. A lower fatty acid ester of cellulose is preferable. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxy group may be linear or branched, and may form a ring. Furthermore, another substituent may be substituted. In the case of the same degree of substitution, birefringence decreases when the number of carbon atoms is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

The cellulose ester may be an acyl group derived from a mixed acid, and particularly preferably an acyl group having 2 and 3 carbon atoms or 2 and 4 carbon atoms. In the present invention, as the cellulose ester, a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate is used. Can do. The butyryl group that forms butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose butyrate, cellulose propionate, cellulose acetate butyrate, and cellulose acetate propionate are particularly preferably used.

In the case of cellulose acetate, cellulose acetate having an acetyl group substitution degree X of 2.0 ≦ X <2.7 is preferable from the viewpoint of expression of retardation. A more preferable degree of acetyl group substitution is 2.2 ≦ X ≦ 2.5.

On the other hand, in the case of cellulose acetate butyrate and cellulose acetate propionate, those that simultaneously satisfy the following formulas (1) to (3) are preferable.

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 1.9 <= X <= 3.0
Formula (3) 0.1 <= Y <= 1.1
In the formula, X is the degree of substitution of the acetyl group, Y is the degree of substitution of the propionyl group or butyryl group, and X + Y is the degree of substitution of the total acyl group.

Among these, in the case of cellulose acetate propionate, 1.9 ≦ X ≦ 2.5 and preferably 0.2 ≦ Y ≦ 1.0.

If the degree of substitution of the acetyl group is too low, there are many unreacted parts with respect to the hydroxy group of the pyranose ring constituting the skeleton of the cellulose resin, and a large amount of the hydroxy group remains, resulting in dimensional change and warping. In addition, physical properties as a binder are liable to deteriorate, such as a slit failure.

The cellulose ester used in the present invention has a number average molecular weight (Mn) of 60,000 or more and less than 180,000, a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio, and Mw / Mn is 1.5 to 5.5. Are preferably used, particularly preferably 2.0 to 5.0, more preferably 2.5 to 5.0, and still more preferably 3.0 to 5.0 cellulose ester.

The cellulose ester used in the present invention preferably contains two or more types of cellulose esters having a weight average molecular weight (Mw) of Mw ≧ 260,000 and Mw of 10,000 or more.

The smaller the molecular weight of the cellulose ester, the less the haze rises during the stretching process, but the peelability from the belt during casting tends to deteriorate, and by mixing two or more cellulose esters having different molecular weights, the peelability is improved. At the same time, the compatibility between the plasticizer and the cellulose ester, which will be described later, can be improved, so that there is an effect of suppressing the increase in haze and enhancing the dimensional stability.

The weight average molecular weight (Mw) is preferably in the range of 260000-500000, more preferably in the range of 290000-400000. The difference in Mw between two or more cellulose esters is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 50,000 or less.

The mixing ratio of the low molecular weight cellulose ester and the high molecular weight cellulose ester can be in the range of 99: 1 to 1:99, but is preferably in the range of 90:10 to 50:50, more preferably 90:10 to It is within the range of 60:40, particularly preferably within the range of 85:15 to 60:40.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the cellulose ester can be measured as follows.

Measured by high performance liquid chromatography under the following conditions.

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

The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and wood pulp (coniferous pulp, hardwood pulp), cotton linter, and the like can be used. The Mw of the cellulose ester can be controlled by the type of cellulose and the use of a plurality of raw material celluloses. For example, if esterification is performed using pre-hydrolysis kraft pulp, the Mw of the cellulose ester increases, and if softwood sulfite pulp is used, the Mw tends to decrease. Therefore, cellulose may be used singly or in combination of two or more. For example, softwood pulp and cotton linter or hardwood pulp may be used in combination. As cellulose, usually pulp (particularly softwood pulp) is often used. The α-cellulose content (mass%) of cellulose is usually from 94 to 99 (eg, 95 to 99), preferably from about 96 to 98.5 (eg, 97.3 to 98). .

In the cellulose ester according to the present invention, when the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), an organic solvent such as acetic acid or an organic solvent such as methylene chloride is used. The reaction is carried out using a protic catalyst such as sulfuric acid. When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

(Additive)
The polarizing plate protective films T2 and T3 according to the present invention include retardation adjusters such as resins and polymers other than cellulose esters, plasticizers, retardation increasing agents, retardation reducing agents, ultraviolet absorbers, antioxidants, and light stability. It is preferable to contain an agent, a dye, a peeling accelerator, a sliding agent such as fine particles.

(Plasticizer)
The polarizing plate protective film according to the present invention preferably contains an appropriate amount of a plasticizer as necessary to obtain the effects of the present invention. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like. Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

The polyhydric alcohol ester is composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The polyhydric alcohol used is represented by the following general formula (1).

General formula (1) R1- (OH) _n (wherein R1 represents an n-valent organic group and n represents a positive integer of 2 or more)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, pentaerythritol, dipentaerythritol and the like. Of these, trimethylolpropane and pentaerythritol are preferable.

There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but are not limited thereto.

As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or derivatives thereof can be mentioned. In particular, benzoic acid is preferred.

The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester. The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are. Although the specific compound of a polyhydric alcohol ester is shown below, it is not limited to this.

In addition, trimethylolpropane triacetate, pentaerythritol tetraacetate, and the like are also preferably used.

The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

The polyvalent carboxylic acid ester compound is composed of an ester of a divalent or higher, preferably a divalent to 20valent polyvalent carboxylic acid and an alcohol. The aliphatic polyvalent carboxylic acid is preferably divalent to 20-valent, and in the case of an aromatic polyvalent carboxylic acid or alicyclic polyvalent carboxylic acid, it is preferably trivalent to 20-valent.

The polyvalent carboxylic acid is represented by the following general formula (2).

General formula (2) R2 (COOH) _m (OH) _n (where R2 is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, COOH group is a carboxy group, OH The group represents an alcoholic or phenolic hydroxy group.)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

The alcohol used in the polyvalent carboxylic acid ester compound that can be used in the present invention is not particularly limited, and known alcohols and phenols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxy group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

As the aliphatic monocarboxylic acid, a straight-chain or side-chain fatty acid having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. Aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

The alcohol used for the polyvalent carboxylic acid ester may be one kind or a mixture of two or more kinds.

The acid value of the polycarboxylic acid ester compound is preferably 1 mgKOH / g or less, more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

(Acid value)
The acid value refers to the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxy group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto. For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

(Sugar ester compound)
The polarizing plate protective films T2 and T3 according to the present invention contain a compound represented by the following general formula (I) (in the present invention, a sugar ester compound other than a cellulose ester is referred to as a sugar ester compound). However, it is preferable for preventing haze caused by stretching and promoting stable retardation.

The average substitution degree of the compound represented by the general formula (I) used in the present invention is in the range of 3.0 to 6.0, which suppresses haze increase in the stretching treatment and exhibits a stable phase difference. It is also effective above. The average degree of substitution is more preferably in the range of 4.5 to 6.0.

In the present invention, the degree of substitution of the compound represented by the general formula (I) represents the number substituted with a substituent other than hydrogen among the eight hydroxy groups contained in the general formula (I). Represents a number containing groups other than hydrogen among R ₁ to R ₈ in formula (I). Accordingly, when all of R ₁ to R ₈ are substituted with a substituent other than hydrogen, the degree of substitution is 8.0, which is the maximum value, and when R ₁ to R ₈ are all hydrogen atoms, 0.0 It becomes.

The compound having the structure represented by the general formula (I) is difficult to synthesize a single kind of compound in which the number of hydroxy groups and the number of OR groups are fixed, and the number of hydroxy groups in the formula, OR Since it is known that a compound in which several kinds of components having different groups are mixed is used, it is appropriate to use the average degree of substitution as the degree of substitution of the general formula (I) in the present invention. The average substitution degree can be measured from the area ratio of the chart showing the substitution degree distribution by chromatography.

In the general formula (I), R ₁ to R _{8 each} represents a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group, and each of R ₁ to R ₈ is the same. May be different.

Examples of the sugar as a raw material for synthesizing the sugar ester compound used in the present invention include the following, but the present invention is not limited to these.

Glucose, galactose, mannose, fructose, xylose, or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose Can be mentioned.

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

The monocarboxylic acid used in the synthesis of the sugar ester compound used in the present invention is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like can be used. . The carboxylic acid used may be one type or a mixture of two or more types.

Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecyl acid, Saturated lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, and laxaric acid Examples thereof include unsaturated fatty acids such as fatty acids, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids in which 1 to 5 alkyl groups or alkoxy groups are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, An aromatic monocarboxylic acid having two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid and tetralin carboxylic acid, or a derivative thereof can be mentioned, and benzoic acid is particularly preferable.

Some specific examples are shown below, but these are cases where R ₁ to R ₈ are all the same substituents, and the present invention is not limited thereto. In the table below, when the average degree of substitution is less than 8.0, any one of R ₁ to R ₈ represents a hydrogen atom.

The sugar ester compound used in the present invention can be produced by reacting a sugar ester with an acylating agent (also called an esterifying agent, for example, an acid halide of acetyl chloride, an anhydride such as acetic anhydride). The distribution of the degree of substitution is made by adjusting the amount of acylating agent, the timing of addition, and the esterification reaction time, but it is possible to mix sugar ester compounds with different degrees of substitution, or purely isolated degrees of substitution. By mixing the compounds, it is possible to adjust a component having a target average substitution degree and a substitution degree of 4 or less.

(Synthesis Example: Synthesis of Compound According to the Present Invention)

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 135.6 g (0.6 mol) of benzoic anhydride, 284. 8 g (3.6 mol) was charged, the temperature was raised while bubbling nitrogen gas through a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of the Kolben is depressurized to 4 × 10 ² Pa or less, and after excess pyridine is distilled off at 60 ° C., the inside of the Kolben is depressurized to 1.3 × 10 Pa or less and the temperature is raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A sugar ester compound 1 which is a mixture of A-1, A-2, A-3, A-4, A-5 and the like was obtained.

The obtained mixture was analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). As a result, A-1 was 1.2% by mass, A-2 was 13.2% by mass, and A-3 was 14.2% by mass. %, A-4 was 35.4% by mass, A-5 and the like were 40.0% by mass. The average degree of substitution was 5.2.

Similarly, 158.2 g (0.7 mol) of benzoic anhydride, 146.9 g (0.65 mol), 135.6 g (0.6 mol), 124.3 g (0.55 mol) and equimolar pyridine. To obtain sugar esters of components as shown in Table 1.

Next, a part of the obtained mixture is purified by column chromatography using silica gel to obtain 100% pure A-1, A-2, A-3, A-4, A-5, etc., respectively. Obtained.

A-5 etc. means a mixture of all components having a substitution degree of 4 or less, that is, compounds having substitution degrees of 4, 3, 2, 1. The average degree of substitution was calculated with A-5 and the like being the degree of substitution 4.

In the present invention, the average degree of substitution was adjusted by adding in combination the sugar ester close to the desired degree of average substitution and the isolated A-1 to A-5 etc. by the method prepared here.

<Measurement conditions for HPLC-MS>
1) LC section Equipment: Column oven (JASCO CO-965) manufactured by JASCO Corporation, detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C
The polarizing plate protective film according to the present invention preferably contains the sugar ester compound in the polarizing plate protective film in the range of 1 to 20% by mass, particularly in the range of 3 to 15% by mass. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out during storage of the raw material.

(Ester compound)
The polarizing plate protective films T2 and T3 according to the present invention preferably contain an ester compound represented by the following general formula (II) from the viewpoint of preventing haze due to stretching and suppressing breakage and the like.

As the ester compound, an ester compound having an aromatic ring or a cycloalkyl ring in the molecule is preferably used. As the ester compound, an aromatic terminal ester plasticizer represented by the following general formula (II) is preferably used.

Formula (II) B- (GA) _n -GB
(Wherein B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
The compound represented by the general formula (II) includes a benzene monocarboxylic acid residue represented by B, an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, and an alkylene dicarboxylic acid represented by A. It is composed of a residue or an aryl dicarboxylic acid residue, and can be obtained by the same reaction as a normal polyester plasticizer.

Examples of the benzene monocarboxylic acid component of the ester plasticizer include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, normal propyl benzoic acid, and aminobenzoic acid. And acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

Examples of the alkylene glycol component having 2 to 12 carbon atoms of the ester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1, 2-propanediol, 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-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Used as a mixture of two or more. In particular, alkylene glycols having 2 to 12 carbon atoms are particularly preferable because of excellent compatibility with cellulose esters.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols include 1 It can be used as a seed or a mixture of two or more.

Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like.

The number average molecular weight of the ester plasticizer is preferably in the range of 300 to 1500, more preferably in the range of 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

Hereinafter, synthesis examples of aromatic terminal ester plasticizers will be shown.

<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst. While the monohydric alcohol was refluxed, heating was continued in the range of 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Next, the distillate is removed under reduced pressure of 1.33 × 10 ⁴ Pa to finally 4 × 10 ² Pa or less within a range of 200 to 230 ° C., and then filtered to obtain an aromatic terminal having the following properties: An ester plasticizer was obtained.

Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2
<Sample No. 2 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 31000
Acid value: 0.1
<Sample No. 3 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as the catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 38000
Acid value: 0.05
<Sample No. 4 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05
Although the specific compound of an aromatic terminal ester plasticizer is shown below, this invention is not limited to this.

The polarizing plate protective film according to the present invention preferably contains the ester compound in the range of 1 to 20% by mass, particularly 3 to 11% by mass. If it is in this range, while exhibiting the outstanding effect of this invention, failures, such as a fracture | rupture, can be suppressed.

(Retardation increasing agent)
The polarizing plate protective films T2 and T3 according to the present invention, in particular, a film satisfying the above requirement (1) preferably contains a retardation increasing agent, and is described in European Patent No. 911,656A2 as the retardation increasing agent. It is preferable to use an aromatic compound having two or more aromatic rings as a retardation increasing agent. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

(Cellulose ester resin / thermoplastic acrylic resin-containing film)
The polarizing plate protective films T2 and T3 according to the present invention, in particular, the film satisfying the above requirement (2) contains a thermoplastic acrylic resin and a cellulose ester resin from the viewpoint of adjusting the retardation, It is preferable that the content ratio of the cellulose ester resin is a thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50.

Acrylic resin includes methacrylic resin. The acrylic resin is not particularly limited, but is composed of 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith. Is preferred. Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Examples thereof include maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like, and these can be used alone or in combination of two or more monomers.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used. The weight average molecular weight (Mw) is preferably in the range of 80,000 to 500,000, and more preferably in the range of 110,000 to 500,000. The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography including the measurement conditions.

The method for producing the acrylic resin is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be carried out within a range of 30 to 100 ° C., and bulk or solution polymerization may be carried out within a range of 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent. Commercial products can also be used. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination. The acrylic resin may be a graft copolymer obtained by grafting a (meth) acrylic resin to a copolymer of (meth) acrylic rubber and an aromatic vinyl compound. In the graft copolymer, a copolymer of (meth) acrylic rubber and an aromatic vinyl compound forms a core, and the (meth) acrylic resin forms a shell around the copolymer. -A shell-type graft copolymer is preferred.

The total mass of the acrylic resin and the cellulose ester resin in the polarizing plate protective film is preferably 55% by mass or more of the polarizing plate protective film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. is there.

(Acrylic particles)
The polarizing plate protective film may contain acrylic particles because it is excellent in improving brittleness. An acrylic particle represents the acrylic component which exists in the state of particle | grains (it is also called an incompatible state) in the polarizing plate protective film which contains the said thermoplastic acrylic resin and cellulose-ester resin in a compatible state.

The acrylic particles are not particularly limited, but are preferably multi-layered acrylic granular composites. Examples of commercial products of acrylic granular composites that are multi-layer structured polymers include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Co., Ltd., “Paraloid” manufactured by Kureha Co., Ltd., “Acryloid manufactured by Rohm and Haas Co., Ltd. “Staphyroid” manufactured by Gantz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination of two or more. When the acrylic particles are added to the polarizing plate protective film, it is preferable that the refractive index of the mixture of the acrylic resin and the cellulose ester resin is close to the refractive index of the acrylic particles in order to obtain a highly transparent film. Specifically, the refractive index difference between the acrylic particles and the acrylic resin is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

The acrylic particles are in a range of acrylic particles: acrylic resin and cellulose ester resin total mass = 0.5: 100 to 30: 100 with respect to the total mass of the acrylic resin and cellulose ester resin constituting the film. It is preferable from the standpoint that the target effect is better exhibited, and more preferably, the total mass of acrylic particles: acrylic resin and cellulose ester resin = 1.0: 100 to 15: 100.

(Retardation reducing agent)
It is preferable from the viewpoint of retardation adjustment that the polarizing plate protective film T2 or T3 of the present invention, particularly the film satisfying the requirement (2), contains the following polymer X and polymer Y.

The polymer X used in the present invention comprises an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. It is a polymer having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization, and is preferably a polymer represented by the following general formula (5). Furthermore, it is preferable that it is solid under 30 degreeC, or a glass transition temperature is 35 degreeC or more.

General formula (5)
-[CH ₂ -C (-R1) (-OCOR2)] _m- [CH ₂ (-CR3) (-OCOR4-OH)-] _n
(In the formula, R 1 and R ₃ are H or CH ₃ , R 2 and R 4 are CH _2, C ₂ H ₄ or C ₃ H ₆ , and m and n are repeating units.)
Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-ethoxyethyl), etc., or those obtained by replacing the above acrylic ester with a methacrylic ester. Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxy group. For example, acrylic acid (2-hydroxyethyl) , Acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing acrylic acid with methacrylic acid Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

In the present invention, the polymer X is synthesized by copolymerization using the hydrophobic monomer Xa and the hydrophilic monomer Xb.

The use ratio during the synthesis of the hydrophobic monomer Xa and the hydrophilic monomer Xb is preferably in the range of 99: 1 to 65:35, and more preferably in the range of 95: 5 to 75:25. When the use ratio of the hydrophobic monomer Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the use ratio of the hydrophilic monomer Xb is large, the compatibility is deteriorated, but the effect of reducing the retardation value Rt is high. Moreover, since the haze comes out at the time of film forming when the usage-amount of the hydrophilic monomer Xb exceeds the said range, it is unpreferable.

In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible without increasing the molecular weight. Examples of such a polymerization method include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than usual polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further disclosed in JP 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxy group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Preferably used.

The hydroxyl value of polymer X is preferably 30 to 150 [mg KOH / g].

(Method for measuring hydroxyl number)
This measurement conforms to JIS K 0070 (1992). This hydroxyl number is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bound to hydroxy groups when 1 g of sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. Attach an air cooling tube to the mouth of the flask and heat in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl number is calculated by the following formula.

Hydroxyl number = {(BC) × f × 28.05 / X} + D (where B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), C is titration) The amount of 0.5 mol / L potassium hydroxide ethanol solution used in (ml), f is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is the acid value, and 28.05 is potassium hydroxide. (It represents 1/2 of 1mol amount 56.11)
The molecular weight of the polymer X has a weight average molecular weight in the range of 2000 to 30000, more preferably in the range of 4000 to 25000 or more.

A large molecular weight is preferable because it has advantages such as little dimensional change of the cellulose ester film under high temperature and high humidity, and less curling as a polarizing plate protective film. When the weight average molecular weight is 30000 or less, compatibility with the cellulose ester is good, bleeding out under high temperature and high humidity, and haze immediately after film formation are good. It is preferable that the polymer X is solid at room temperature (23 ° C.) because the dimensional stability of the polarizing plate is improved.

The weight average molecular weight of the polymer X used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., but this temperature or the polymerization reaction time can be adjusted.

The method for measuring the weight average molecular weight can be as follows.

(Molecular weight measurement method)
The weight average molecular weight is measured using high performance liquid chromatography.

The measurement conditions are as follows.

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

The polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 to 3,000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring, and is represented by the following general formula (6). The glass transition temperature is preferably 35 ° C. or lower, and more preferably liquid at 23 ° C. Polymers having a weight average molecular weight of less than 500 are difficult to produce due to an increase in residual monomers, and polymers having a weight average molecular weight of 3000 or less, low glass transition temperature materials, and liquid materials are preferable because of their high retardation Rt reduction performance.

General formula (6)
Ry— [CH ₂ —C (—R 5) (— OCOR 6)] _k —OH ( _where R y is OH or H or alkyl having 3 or less carbon atoms, R 5 is H or CH ₃ , R 6 is CH ₂ or C ₂ H ₄ or C ₃ H ₆ is represented, and k represents a repeating unit)
The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is: vinyl acetate, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, Vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotrate, vinyl sorbate, cinnamon Examples of acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (N-, i-, s-), hexyl acrylate (n-, -), Heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate Acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxy) Butyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid such as acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, Itaconic acid and the like can be mentioned. The polymer composed of the above monomers may be a copolymer or a homopolymer, and a homopolymer of vinyl ester, a copolymer of vinyl ester, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester is preferable.

Examples of the acrylate monomer having no aromatic ring include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i-, s-, t-). Pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), acrylic acid Nonyl (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2- Hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl) ), Acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomer, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. Is preferred. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

Polymers obtained by polymerizing the above-mentioned ethylenically unsaturated monomers and acrylic polymers are both highly compatible with cellulose esters, excellent in productivity without evaporation and volatilization, and retainability as a protective film for polarizing plates. The moisture permeability is small, and the dimensional stability is excellent.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass%) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferred range of formula (i) is in the range of 10-25% by weight.

If the total amount of the polymer X and the polymer Y is not 5% by mass or more, the retardation value Rt is not sufficiently reduced. Moreover, if it is not 35 mass% or less as a total amount, adhesiveness with polarizer PVA will be impaired.

When the amount of the polymer X is increased, the polarizer deterioration is remarkably improved, but the retardation value Rt tends to increase. Therefore, the range satisfying the above formula (ii) is preferable for obtaining the effect used in the present invention. .

Polymer X and polymer Y can be directly added and dissolved as a material constituting the dope described later, or can be added to the dope after being previously dissolved in an organic solvent for dissolving the cellulose ester.

(UV absorber)
The polarizing plate protective films T2 and T3 according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. Preferably it is 2% or less.

Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by BASF Japan and can be preferably used.

The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

Specific examples of the benzotriazole-based ultraviolet absorber used in the present invention are listed below, but the present invention is not limited to these.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6- (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- Mixture of 4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN109)
Specific examples of the benzophenone-based ultraviolet absorber are shown below, but the present invention is not limited thereto.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

The polarizing plate protective film according to the present invention preferably contains two or more ultraviolet absorbers.

Also, as the ultraviolet absorber, a polymeric ultraviolet absorber can also be preferably used, and in particular, a polymer type ultraviolet absorber described in JP-A-6-148430 is preferably used.

The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is in the range of 30 to 200 μm, it is 0.5% relative to the film. It is preferably in the range of ˜10% by mass, and more preferably in the range of 0.6 to 4% by mass.

(Fine particles)
The polarizing plate protective film according to the present invention preferably contains fine particles from the viewpoint of improving slipperiness and eliminating poor conveyance such as slipping.

As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

The average primary particle size of the fine particles is preferably in the range of 5 to 400 nm, and more preferably in the range of 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size in the range of 0.05 to 0.3 μm. If the particles have an average particle size in the range of 100 to 400 nm, the primary particles are not aggregated. It is also preferable that it is contained. The content of these fine particles in the polarizing plate protective film is preferably in the range of 0.01 to 1% by mass, particularly preferably in the range of 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by a co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

Zirconium oxide fine particles are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the polarizing plate protective film low. In the polarizing plate protective film according to the present invention, it is preferable that the dynamic friction coefficient of at least one surface is in the range of 0.2 to 1.0.

<Manufacturing method of polarizing plate protective films T2 and T3>
Next, the manufacturing method of polarizing plate protective film T2, T3 which concerns on this invention is demonstrated.

The polarizing plate protective film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method. Hereinafter, the solution casting method will be described, but it is not limited thereto.

The production of the polarizing plate protective film according to the present invention by the solution casting method is a step of preparing a dope by dissolving the cellulose ester and the additive in a solvent, casting on an endless metal support that moves the dope indefinitely. A step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration that achieves both of these is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 25% by mass.

The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what melt | dissolves the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not dissolve is defined as a poor solvent. Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

The good solvent is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. The dope preferably contains water in the range of 0.01 to 2% by mass. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again. The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

A general method can be used as a method for dissolving the cellulose ester when the dope is prepared. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

Pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is in the range of 45 to 120 ° C, more preferably in the range of 60 to 110 ° C, and still more preferably in the range of 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, the cellulose ester solution is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. Therefore, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium in the range of 0.001 to 0.008 mm is more preferable, and a filter medium in the range of 0.003 to 0.006 mm is more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

A bright spot foreign material is placed in a crossed Nicols state with two polarizing plates, a polarizing plate protective film is placed between them, light is applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side sometimes leaks, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm ² or less, still more preferably 50 pieces / m ² or less, still more preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is in the range of 45 to 120 ° C, more preferably in the range of 45 to 70 ° C, and still more preferably in the range of 45 to 55 ° C.

A smaller filtration pressure is preferable. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

Here, the dope casting will be described.

The metal support in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be 1 to 4 m. Since the width of the polarizing plate protective film is preferably 2 m to 4 m, the cast width is necessarily wide. The surface temperature of the metal support in the casting step is −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web drying speed can be increased. May deteriorate. The support temperature is preferably in the range of 0 to 40 ° C, more preferably in the range of 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

In order for the polarizing plate protective film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably in the range of 10 to 150% by mass, more preferably in the range of 20 to 40% by mass. Or in the range of 60 to 130% by mass, particularly preferably in the range of 20 to 30% by mass or in the range of 70 to 120% by mass.

In the present invention, the amount of residual solvent is defined by the following formula.

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

Next, the peeled web is transported to the above-described stretching process (preferably a tenter), stretched, and then transported to the film drying process.

(Stretching operation, refractive index control)
In order to satisfy the requirement (1) in the polarizing plate protective films T2, T3, preferably T2, according to the present invention, it is preferable to perform refractive index control, that is, retardation control by stretching operation.

Stretching operation can be performed biaxially or uniaxially, for example, sequentially or simultaneously in the longitudinal direction (film forming direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. Simultaneous biaxial stretching includes stretching in one direction and contracting the other tension by relaxing.

The draw ratios in the biaxial directions perpendicular to each other may eventually be in the range of 0.8 to 1.5 times in the casting direction and in the range of 1.1 to 2.5 times in the width direction. It is preferable to carry out within a range of 0.9 to 1.0 times in the casting direction and 1.2 to 2.0 times in the width direction.

The stretching temperature is preferably in the range of 120 ° C to 200 ° C, more preferably in the range of 140 ° C to 180 ° C.

The residual solvent in the film at the time of stretching is preferably in the range of 20 to 0%, and more preferably in the range of 15 to 0%.

There is no particular limitation on the method of stretching the web. For example, a method in which a circumferential speed difference is applied to a plurality of rollers, and the roller is stretched in the longitudinal direction by utilizing the difference in the circumferential speed of the roller. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by a linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

It is preferable to carry out the width maintenance or lateral stretching in the film forming step by a tenter, and it may be a pin tenter or a clip tenter. In addition, you may extend | stretch sequentially, even if a conveyance direction and the width direction are extended | stretched simultaneously.

The polarizing plate protective film is preferably heat-set after the stretching treatment, but the heat setting is preferably heat-set usually within a temperature range of Tg-20 ° C. or lower for 0.5 to 300 seconds. At this time, it is preferable to perform heat fixing while sequentially raising the temperature in a range where the temperature difference is 1 to 100 ° C. in the region divided into two or more.

The heat-fixed film is usually cooled to Tg or less, and the clip gripping portions at both ends of the film are cut and wound. The cooling is preferably performed by gradually cooling from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film.

More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the type of additives such as cellulose ester and plasticizer constituting the film, so the physical properties of the obtained stretched film are measured and preferable characteristics are obtained. Thus, it may be determined by adjusting as appropriate.

The slow axis or the fast axis of the polarizing plate protective film according to the present invention exists in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less when the angle formed with the film forming direction is θ1. It is more preferably −0.5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

Next, in the film drying process, generally, a roller drying method (a method in which webs are alternately passed through a plurality of rollers arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roller, microwave, or the like, but is preferably performed with hot air from the viewpoint of simplicity.

The drying temperature in the web drying process is preferably increased stepwise within a range of 40 to 200 ° C. The preferable drying time depends on the drying temperature, but is preferably in the range of 5 minutes to 60 minutes, and more preferably in the range of 10 minutes to 30 minutes.

It is preferable to provide a slitter after the predetermined heat treatment and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

The knurling process can be formed by pressing a heated embossing roller. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film, and the end can be made bulky.

The height of the knurling at both ends of the width of the polarizing plate protective film according to the present invention is preferably in the range of 4 to 20 μm, and preferably in the range of 5 to 20 mm.

In the present invention, the knurling process is preferably provided after the drying in the film forming process and before winding.

The film thickness of the polarizing plate protective films T2 and T3 according to the present invention is not particularly limited, but is preferably in the range of 10 to 200 μm. The film thickness is more preferably in the range of 10 to 100 μm, and further preferably in the range of 20 to 60 μm from the viewpoint of thinning and weight reduction.

The polarizing plate protective films T2 and T3 according to the present invention have a width in the range of 1 to 4 m. Those having a width in the range of 1.4 to 4 m are preferably used, and particularly preferably in the range of 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

<Physical properties>
The moisture permeability of the polarizing plate protective films T2 and T3 according to the present invention is preferably in the range of 10 to 1200 g / m ² · 24 h at 40 ° C. and 90% RH, and more preferably in the range of 20 to 1000 g / m ² · 24 h. A range of 20 to 850 g / m ² · 24 h is particularly preferable. The moisture permeability can be measured according to the method described in JIS Z 0208.

The visible light transmittance of the polarizing plate protective films T2 and T3 according to the present invention is preferably 90% or more, and more preferably 93% or more.

The haze of the polarizing plate protective films T2 and T3 according to the present invention is preferably less than 1%, particularly preferably in the range of 0 to 0.1%.

<Λ / 4 plate>
The λ / 4 plate according to the present invention refers to a plate having a function of converting linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). The λ / 4 plate is designed so that the retardation value Ro in the in-plane direction of the layer is about 1/4 with respect to a predetermined wavelength of light (usually in the visible light region).

In the λ / 4 plate according to the present invention, the retardation value Ro (590) in the in-plane direction measured at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH is preferably in the range of 110 to 170 nm.

The λ / 4 plate according to the present invention is a retardation plate (resin) having a retardation value of approximately ¼ of the wavelength in the visible light wavelength range in order to obtain almost perfect circularly polarized light in the visible light wavelength range. Film).

“Retardation of approximately 1/4 in the wavelength range of visible light” means that the longer the wavelength in the wavelength range of 400 to 700 nm, the larger the retardation, and the retardation value Ro (450) measured at a measurement wavelength of 450 nm and the measurement wavelength It is preferable that Ro (590) which is a retardation value measured at 590 nm satisfies 1 <Ro (590) / Ro (450) ≦ 1.6. Furthermore, in order to function effectively as a λ / 4 plate, the Ro (450) is in the range of 100 to 125 nm, and the retardation value Ro (550) measured at the measurement wavelength of 550 nm is in the range of 125 to 142 nm. It is more preferable that the Ro (590) is a retardation film in the range of 130 to 152 nm.

A circularly polarizing plate is obtained by laminating so that the angle between the slow axis of the λ / 4 plate and the transmission axis (or absorption axis) of the polarizer is substantially 45 °. “Substantially 45 °” means within a range of 40 to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizer is preferably in the range of 41 to 49 °, more preferably in the range of 42 to 48 °, More preferably within the range of 43 to 47 °, most preferably within the range of 44 to 46 °.

The λ / 4 plate according to the present invention is a length that is stretched in an oblique direction so that the angle formed by the width direction and the slow axis in the plane of the λ / 4 plate is within a range of 40 to 50 °. When it is a long λ / 4 plate, a long circular polarizing plate can be easily obtained by laminating with a long polarizer having an absorption axis in the longitudinal direction with a roll to roll.

(Material of λ / 4 plate, manufacturing method)
The λ / 4 plate according to the present invention is preferably a film containing a thermoplastic resin, and the thermoplastic resin used is a cellulose ester, in terms of production, cost, ease of processing, transparency, It is preferable from the viewpoints of uniformity, suitability for saponification, adhesiveness, and the like.

The λ / 4 plate according to the present invention is produced by appropriately combining cellulose esters, other thermoplastic resins, plasticizers, and other various additives that can be used in the polarizing plate protective films T2 and T3 according to the present invention. can do.

Like the polarizing plate protective films T2 and T3, the λ / 4 plate according to the present invention is a film produced by a solution casting method or a film produced by a melt casting method. It can be preferably used.

In the case of the solution casting method, similarly, a step of preparing a dope by dissolving the cellulose ester and the additive in a solvent, a step of casting on an endless metal support that moves the dope infinitely, a cast dope Is performed by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

(Λ / 4 plate stretching process)
The λ / 4 plate according to the present invention is preferably subjected to a stretching treatment in order to give the retardation value Ro in the in-plane direction.

There is no particular limitation on the stretching method. For example, a method in which a circumferential speed difference is applied to a plurality of rollers, and the roller is stretched in the longitudinal direction by utilizing the difference in the circumferential speed of the roller. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

In the present invention, in particular, stretching is performed in the transport direction using the difference in peripheral speed of the film transport rollers, or both ends of the web are clipped in a direction orthogonal to the transport direction (also referred to as the width direction or the TD direction). It is preferable to use a tenter method for gripping, and it is further preferable to use a tenter that can independently control the gripping length of the web (distance from the start of gripping to the end of gripping) by the left and right gripping means.

In the present invention, it is also preferable to stretch either the λ / 4 plate according to the present invention or the polarizer in a 45 ° direction with respect to the film transport direction in the stretching step.

This is because, in a display device whose polarization axis is parallel to the long side direction or the short side direction of the polarizing plate, such as a polarizing plate used in a VA type or IPS type liquid crystal display device, a roll-shaped λ / 4 plate is used. When the angle between the longitudinal direction and the in-plane slow axis is substantially 45 °, a λ / 4 plate cut in parallel to the longitudinal direction or the transverse direction has a transmission axis (or absorption axis) of the polarizer. Since it can be bonded to a roll-shaped polarizer parallel to the longitudinal direction by aligning the longitudinal direction or the transverse direction, there is little cut loss of the film, which is advantageous in production.

A roll-like λ / 4 plate in which the angle between the longitudinal direction and the in-plane slow axis is substantially 45 ° is obtained by placing the roll-like cellulose acylate film in a direction substantially 45 ° with respect to the longitudinal direction. It can manufacture by extending | stretching.

Hereinafter, a method of stretching in the 45 ° direction will be described.

In order to obliquely stretch the cellulose acylate film in a direction substantially 45 ° with respect to the longitudinal direction, it is preferable to use a tenter shown in FIG. FIG. 3 is a schematic diagram showing oblique stretching by a tenter.

The stretched film is manufactured using a tenter. This tenter is a device that widens a film fed from a film roll (feeding roll) in an oblique direction with respect to its traveling direction (moving direction of the middle point in the film width direction) in a heating environment by an oven. The tenter includes an oven, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. Both ends of the film fed out from the film roll and sequentially supplied to the entrance portion of the tenter are gripped by a gripping tool, the film is guided into the oven, and the film is released from the gripping tool at the exit portion of the tenter. The film released from the gripping tool is wound around the core. Each of the pair of rails has an endless continuous track, and the gripping tool which has released the grip of the film at the exit portion of the tenter travels outside and is sequentially returned to the entrance portion.

In addition, the rail shape of the tenter is asymmetrical on the left and right according to the orientation angle, stretch ratio, etc. given to the stretched film to be manufactured, and can be finely adjusted manually or automatically. In the present invention, a long thermoplastic resin film is stretched, and the orientation angle θ can be set to an arbitrary angle within the range of 40 ° to 80 ° with respect to the winding direction after stretching. Yes. In the present invention, the gripping tool of the tenter is configured to travel at a constant speed with a certain distance from the front and rear gripping tools.

FIG. 3 shows the track (rail pattern) of the tenter rail used for oblique stretching. The feeding direction DR1 of the cellulose ester film is different from the winding direction (MD direction) DR2 of the stretched film, thereby obtaining a wide and uniform optical characteristic even in a stretched film having a relatively large orientation angle. Is possible. The feeding angle θi is an angle formed by the feeding direction DR1 of the film before stretching and the winding direction DR2 of the film after stretching. In the present invention, in order to produce a film having an orientation angle of 40 ° to 80 ° as described above, the feeding angle θi is set to 10 ° <θi <60 °, preferably 15 ° <θi <50 °. The By setting the feeding angle θi in the above range, the variation in the optical characteristics in the width direction of the obtained film becomes good (becomes small).

The cellulose ester film fed out from the film roll (feeding roll) is gripped in order by the left and right gripping tools at the tenter inlet (position a), and then traveled as the gripping tool travels. . The left and right grips CL and CR, which are opposed to the direction of the film traveling direction (feeding direction DR1) at the tenter entrance (position a), run on a rail that is asymmetrical to the left and right, and are in a preheating zone. Through an oven having a stretching zone and a heat setting zone. Here, “substantially perpendicular” indicates that the angle formed by the straight line connecting the aforementioned gripping tools CL and CR and the film feeding direction DR1 is within 90 ± 1 °.

予 Preheating zone refers to the section that runs while the interval between the gripping tools gripping both ends is kept constant at the oven entrance. The stretching zone refers to an interval until the gap between the gripping tools gripping both ends starts to become constant again. In addition, the cooling zone refers to a section in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg ° C. of the thermoplastic resin constituting the film during a period in which the interval between the gripping tools after the stretching zone becomes constant again. .

The temperature of each zone is the glass transition temperature Tg of the thermoplastic resin, the temperature of the preheating zone is in the range of Tg + 5 to Tg + 20 ° C., the temperature of the stretching zone is in the range of Tg to Tg + 20 ° C., and the temperature of the cooling zone is Tg− It is preferably set within the range of 30 to Tg ° C.

The draw ratio R (W / Wo) in the drawing step is preferably in the range of 1.3 to 3.0 times, more preferably in the range of 1.5 to 2.8 times. When the draw ratio is within this range, thickness unevenness in the width direction is reduced, which is preferable. In the stretching zone of the tenter stretching machine, if the stretching temperature is differentiated in the width direction, the thickness unevenness in the width direction can be further improved. In addition, Wo represents the width of the film before stretching, and W represents the width of the film after stretching.

The step of stretching in the oblique direction may be performed in the film forming step (online), or may be unwound after being wound up once and performed in the tenter (offline).

<Polarizing plate protective film T4>
The polarizing plate protective film T4 according to the present invention is not particularly limited, but is preferably a thermoplastic resin film, easy to manufacture, optically uniform, and optically transparent. Is preferable. Any of these may be used, for example, cellulose ester film, polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) film, polyethylene terephthalate, polyethylene naphthalate. Polyester film, polyethylene film, polypropylene film, cellophane, cellulose diacetate film, cellulose acetate butyrate film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, norbornene resin Film, polymethylpentene film, polyetherketone film, Examples include, but are not limited to, ether ketone imide films, polyamide films, fluororesin films, nylon films, cycloolefin polymer films, polyvinyl acetal resin films, polymethyl methacrylate films, and acrylic films. . Of these, cellulose ester films, polycarbonate films, polysulfones (including polyether sulfones) and cycloolefin polymer films are preferred. In the present invention, cellulose ester films are particularly advantageous in terms of production, cost, transparency, uniformity, and adhesion. From the aspect of properties and the like.

The polarizing plate protective film T4 according to the present invention is obtained by appropriately combining cellulose esters, other thermoplastic resins, plasticizers, and other various additives that can be used in the polarizing plate protective films T2 and T3 according to the present invention. Can be manufactured.

The polarizing plate protective film T4 according to the present invention is the same as the polarizing plate protective films T2 and T3, either a film produced by a solution casting method or a film produced by a melt casting method. Can also be preferably used.

Commercially available cellulose ester films can also be preferably used. For example, cellulose ester films (for example, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, and KC12UR (more than Konica Norol) Etc.) are suitable.

It is also preferable to use a brightness enhancement film in order to increase the contrast. The brightness enhancement film reflects the linearly polarized light with a predetermined polarization axis or the circularly polarized light in a predetermined direction when natural light is incident due to a backlight of a liquid crystal display device or the like or reflection from the back side, and transmits other light. is there. Light having a polarization direction that is absorbed by the polarizer is reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer or the like provided behind the brightness enhancement film. The brightness enhancement film transmits only the polarized light whose polarization direction is such that the polarization direction of the light reflected and inverted between the two is allowed to pass through the polarizer. Supply. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

As a brightness enhancement film, for example, a multi-layer thin film of dielectric material or a multi-layer laminate of thin film films having different refractive index anisotropy, which shows a characteristic of transmitting linearly polarized light with a predetermined polarization axis and reflecting other light (3M, D-BEF, etc.), although the cholesteric liquid crystal polymer alignment film and the alignment liquid crystal layer are supported on a film substrate (Nitto Denko, PCF350, Merck, Transmax, etc.) it can.

<Polarizing plate>
In the polarizing plate according to the present invention, the λ / 4 plate is bonded to the polarizer, and the absorption axis of the polarizer and the slow axis of the λ / 4 plate are bonded with an inclination of substantially 45 °. It is preferable to use a circularly polarizing plate.

The polarizing plate according to the present invention uses a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer, and the viewing side polarizing plate is a λ / 4 plate (T1) / polarizer / polarizing plate protection. A film (T2) and a backlight side polarizing plate can be manufactured by bonding with the constitution of polarizing plate protective film (T3) / polarizer / polarizing plate protective film (T4).

Examples of the polarizer preferably used in the polarizing plate according to the present invention include a polyvinyl alcohol polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. Stretching is preferably performed uniaxially in the film forming direction, or stretched in an oblique 45 ° direction using the aforementioned oblique stretching apparatus with respect to the film forming direction.

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

The polarizing plate can be produced by a general method. The polarizing plate protective film according to the present invention subjected to alkali saponification treatment is bonded to at least one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Is preferred.

The polarizing plate can be constructed by further bonding a protective film on one side of the polarizing plate and a separate film on the other side. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

<Stereoscopic image display device>
The liquid crystal display device of the present invention can be suitably used for a stereoscopic video display device. For example, a stereoscopic image display device including a liquid crystal display device and liquid crystal shutter glasses, wherein the liquid crystal shutter glasses are provided with (1) a λ / 4 plate, a liquid crystal cell, and a polarizer in this order, or ( 2) A λ / 4 plate, a polarizer, a liquid crystal cell, and a stereoscopic video display device which is liquid crystal shutter glasses in which a polarizer is provided in this order.

FIG. 4 shows a schematic diagram of a stereoscopic image display apparatus according to the above-described aspect (1) (a system in which the polarizing plate of the glasses is one sheet). Further, FIG. 5 shows a schematic diagram of the above-described aspect (2) (system in which the glasses have two polarizing plates).

In either case, the viewing side polarizing plate of the liquid crystal display device is λ / 4 plate (T1) / polarizer / polarizing plate protective film (T2), and the backlight side polarizing plate is a polarizing plate protective film (T3). ) / Polarizer / polarizing plate protective film (T4).

In the present invention, the above-described aspect and configuration can reduce crosstalk, luminance reduction, and color change (color shift) when tilting the neck when viewing a stereoscopic (3D) image, and can be visually recognized in an excellent environment. The stereoscopic video display device can be maintained with high durability and higher durability against the usage environment.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
In the examples, the polarizing plate protective film is distinguished by referring to the viewing side of the viewing side polarizing plate as T1, the liquid crystal cell side as T2, the liquid crystal cell side of the backlight side polarizing plate as T3, and the backlight side as T4.

(Synthesis of cellulose ester)
By the methods described in JP-A-10-45804 and 08-231761, cellulose acetates having a degree of acetyl group substitution described in Table 2, Table 3, and Table 4 (referred to as CA in the table) were synthesized. The degree of substitution was measured. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, and carvone serving as a raw material for the acyl group substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the degree of substitution was adjusted by adjusting the type and amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of this cellulose ester was removed by washing with acetone.

The degree of substitution was determined by the method specified in ASTM-D817-96.

In addition, the cellulose ester described as CAP in Table 2 and Table 3 is cellulose acetate propionate. The cellulose ester described as CAB is cellulose butyrate.

<Preparation of Polarizing Plate Protective Film T1 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate having an acetyl group substitution degree of 1.90 was added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate (acetyl group substitution degree 1.90, Mw = 200000) 100 parts by mass Sugar ester compound (Exemplary compound 1-7) 10 parts by mass Ester compound (Exemplary compound 2-17) 3 Part by mass Tinuvin 928 (manufactured by BASF Japan) 0.1 part by mass Particulate additive solution 1 1 part by mass The above was put into a sealed main dissolution vessel and dissolved while expanding sales to prepare a dope. Next, using an endless belt casting apparatus, the dope was cast uniformly on a stainless steel belt support at a temperature of 33 ° C. and a width of 2000 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film reached 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

After peeling off the peeled cellulose acetate film, hot air at 140 ° C. was applied by a tenter to widen the stretch rate to 32%, and then relaxed at 140 ° C. for 60 seconds so that the stretch rate was 30%. Thereafter, the tenter conveyance was shifted to the roller conveyance, and the film was further dried at 120 to 150 ° C. and wound up.

Furthermore, using the apparatus described in Example 1 of JP-A-2009-214441 (stretching machine A: FIG. 11), the slow axis forms 45 ° with the film longitudinal direction at a temperature of 170 ° C. and a magnification of 1.5 times. Thus, it extended | stretched in the diagonal direction.

Next, drying was terminated while the drying zone was conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

Thus, a polarizing plate protective film 101 having a dry film thickness of 40 μm and a winding number of 3000 m was obtained. When the retardation of the obtained film was measured by the method described later, it was Ro 153 nm, Rt 110 nm, and was a polarizing plate protective film functioning as a λ / 4 plate.

<Preparation of polarizing plate protective film T1 102-113>
In the production of the polarizing plate protective film 101, the polarizing plate protection was performed in the same manner except that the cellulose acetate was changed to the cellulose acetate having the degree of acetyl group substitution described in Table 2, the additives were changed to the following compounds, and the film thickness was adjusted. Films T1 102 to 113 were produced.

In Table 2, MD in the stretching direction means stretching in the film casting direction, and stretching was performed with a difference in peripheral speed of the rollers so that the stretching ratio was 30%.

In Tables 2 and 3, Compound A is a retardation increasing agent containing a 1,3,5-triazine ring and is a compound having the following structure. TPP represents triphenylene phosphate and BDP represents biphenyl diphenyl phosphate.

<Preparation of Polarizing Plate Protective Film T1 114>
<Production of cycloolefin polymer film (COP)>
In a nitrogen atmosphere, dehydrated cyclohexane (500 parts), 1-hexene (1.2 parts), dibutyl ether (0.15 parts), and triisobutylaluminum (0.30 parts) were mixed in a reactor at room temperature. 20 parts of tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1,4,4a, 9a-tetrahydrofluorene ( A norbornene-based monomer comprising 140 parts of MTF) and 40 parts of 8-methyl-tetracyclo [4.4.0.12, 5.17,10] -dodec-3-ene (hereinafter abbreviated as MTD). The mixture and 40 parts of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 part of butyl glycidyl ether and 0.52 part of isopropyl alcohol were added to deactivate the polymerization catalyst and stop the polymerization reaction.

Next, 270 parts of cyclohexane is added to 100 parts of the reaction solution containing the obtained ring-opening polymer, and further 5 parts of a nickel-alumina catalyst (manufactured by JGC Chemical Co., Ltd.) is added as a hydrogenation catalyst. The mixture was heated to 200 ° C. while being pressurized and stirred, and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MTF / MTD ring-opening polymer hydrogenated polymer. After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray; Septon 2002) and an antioxidant (manufactured by BASF Japan; Irganox 1010) were added to each of the obtained solutions and dissolved. (All are 0.1 parts per 100 parts of polymer). Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), the hydrogenated polymer is extruded in a strand form from an extruder in a molten state, and pellets after cooling. And recovered. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

The obtained ring-opened polymer hydrogenated pellets were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture. Next, the pellets were subjected to a short shaft extruder having a coat hanger type T die with a lip width of 1.6 m (Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip material was tungsten carbide, peel strength from molten resin 44 N ) Was used to produce a cycloolefin polymer film having a thickness of 100 μm. Extrusion molding was performed in a clean room of class 10000 or less under molding conditions of a molten resin temperature of 240 ° C. and a T die temperature of 240 ° C. The obtained cycloolefin polymer film was stretched 1.5 times in the oblique direction at a stretching temperature of 135 ° C. At that time, the length of the tenter device, the clip interval, and the tension of the clip were adjusted so that the orientation angle deviation between the in-plane slow axis of the film and the width direction of the film was within ± 0.4 °. Thereafter, both ears were slit, processed into a film thickness of 87 μm and a width of 1.5 m, and wound into a roll to obtain a polarizing plate protective film T1 114. Moreover, the polyester film was wound up together as a protective film when winding up.

<Preparation of polarizing plate protective film T1 115>
As a polycarbonate resin film (PC) which is a λ / 4 plate, Teijin Chemicals Co., Ltd. Pure Ace TT-138 was used as a polarizing plate protective film T1 115.

<Preparation of polarizing plate protective film T2 201>
A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate having an acetyl group substitution degree of 1.90 was added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate (acetyl group substitution degree 1.90, Mw = 200000) 100 parts by mass Sugar ester compound (Exemplary compound 1-7) 10 parts by mass Ester compound (Exemplary compound 2-14) 3 Part by mass Particulate additive solution 1 1 part by mass The above dope was prepared with Finemet NF manufactured by Nippon Seisen Co., Ltd., then filtered, and uniformly applied to the stainless steel band support at a temperature of 22 ° C. and a width of 2000 mm using a belt casting apparatus. It was cast into. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.35 times in the width direction (TD direction) with a tenter. I let you. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter and relaxing at 130 ° C. for 5 minutes, drying is completed while conveying a drying zone of 120 ° C. and 130 ° C. with a large number of rollers, and a knurling process with a width of 10 mm and a height of 5 μm is applied to both ends of the film. A polarizing plate protective film T2 201 having an initial tension of 220 N / m and a final tension of 110 N / m was wound around a 6-inch inner diameter core to have a film thickness of 45 μm and a winding number of 3000 m.

<Production of Polarizing Plate Protective Films T2 202 to 206, 211 to 212>
In the production of the polarizing plate protective film T2 201, the polarizing plate protective film T2 202- was similarly prepared except that the cellulose acetate was changed to cellulose acetate having the degree of acetyl group substitution described in Table 3 and the additives and film thickness were changed. 206, 210 to 212 were produced.

<Preparation of polarizing plate protective film T2 207-209>
A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate with an acetyl group substitution degree of 2.50 was added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate (acetyl group substitution degree 2.50, Mw = 250,000) 100 parts by mass Sugar ester compound (Exemplified compound 1-7) 15 parts by mass SMA1000P (manufactured by Sartomer) 5 parts by mass Fine particles Additive Solution 1 1 part by mass The main dope was filtered with a filter paper having an average pore diameter of 34 μm and a sintered metal filter having an average pore diameter of 10 μm, and the main dope was cast with a band casting machine. The film peeled off from the band with a residual solvent amount of about 30% by mass was stretched 30% in the width direction by applying hot air of 140 ° C. with a tenter and dried. Thereafter, the transfer from the tenter conveyance to the roller conveyance was performed, and the film was further dried at 120 to 150 ° C., and the polarizing plate protective film T2207 was wound up. The film thickness at this time was 85 μm.

The polarizing plate protective film shown in Table 3 was similarly prepared except that the acetyl group substitution degree of cellulose acetate, the sugar ester compound, the addition amount of SMA1000P, and the film thickness were changed in the production of the above and the polarizing plate protective film T2207. T2 208-209 were produced.

<Preparation of polarizing plate protective film T2 210, 213>
A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate having an acetyl group substitution degree of 2.81 was added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.81, Mw = 230,000) 100 parts by weight Retardation increasing agent (Compound A) 13 parts by weight TPP 7.8 parts by weight BDP 3.9 parts by weight Particulate additive solution 1 1 part by mass The main dope was cast using a band casting machine. The film peeled from the band is stretched 3% in the longitudinal direction from the stripping to the tenter, then stretched to 32% in the width direction using the tenter and relaxed in the width direction, and then the film is detached from the tenter. Then, the film was dried and wound up as a polarizing plate protective film T2 210 having a film thickness of 105 μm and a length of 3000 m.

In the production of the polarizing plate protective film T2 210, the polarizing plate protective film T2 213 was produced in the same manner except that the cellulose acetate was changed to cellulose butyrate having a total acyl group substitution degree of 2.4 and the film thickness was adjusted to 60 μm. did.

<Preparation of Polarizing Plate Protective Film T3 301>
1) Preparation of Cellulose Acetate Solution The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acetate solution D.

(Cellulose acetate solution D composition)
Cellulose acetate (acetyl group substitution degree 2.86, Mw = 200000) 100 parts by mass Methylene chloride 402 parts by mass Methanol 60 parts by mass 2) Preparation of matting agent solution Silica particles with average particle size of 16 nm (AEROSIL R972, Nippon Aerosil Co., Ltd.) 20 parts by mass and 80 parts by mass of methanol were thoroughly mixed for 30 minutes to obtain a silica particle dispersion. This dispersion was put into a disperser together with the following composition, and further stirred for 30 minutes or more to dissolve each component to prepare a matting agent solution.

(Matting agent solution composition)
Silica particle dispersion liquid having an average particle size of 16 nm 10 parts by mass Methylene chloride 76.3 parts by mass Methanol 3.4 parts by mass Cellulose acetate solution D 10.3 parts by mass 3) Preparation of additive solution The following composition is charged into a mixing tank. Then, the mixture was stirred while heating to dissolve each component to prepare a cellulose acetate solution. The compounds shown below were used for the compound (optical anisotropy reducing agent) and the wavelength dispersion adjusting agent that reduce the optical anisotropy.

(Additive solution composition)
Compound (A-19) for reducing optical anisotropy 49.3 parts by mass The following wavelength dispersion adjusting agent (compound UV-102) 7.6 parts by mass Methylene chloride 58.4 parts by mass Methanol 8.7 parts by mass Cellulose acetate Solution D 12.8 parts by mass 94.6 parts by mass of the cellulose acetate solution D, 1.3 parts by mass of the matting agent solution, and 4.1 parts by mass of the additive solution were mixed after filtration, and a band casting machine. Was used for casting. The mass ratio of the compound for reducing optical anisotropy and the wavelength dispersion adjusting agent to cellulose acetate in the above composition was 12% and 1.8%, respectively. The film was peeled off from the band with a residual solvent amount of 30%, and dried at 140 ° C. for 40 minutes to produce a polarizing plate protective film T3 301. The film thickness was 40 μm.

<Preparation of Polarizing Plate Protective Film T3 302>
(Preparation of acrylic resin MA-2 containing maleic anhydride units)
According to “Heat Resistant Acrylic Resin” described in JP-A-2007-113109 [0049], a resin of maleic anhydride 10 mol%, styrene 16 mol%, and methyl methacrylate 74 mol% was synthesized. The Tg was 112 ° C.

The prepared acrylic resin is dried with a vacuum dryer at 90 ° C. to a water content of 0.03% or less, and then 0.3% by mass of a stabilizer (Irganox 1010 (manufactured by BASF Japan Ltd.)) is added to 230%. Under a nitrogen stream at 0 ° C., a biaxial kneading extruder with a vent was used to extrude into water to form a strand, which was then cut to obtain a pellet having a diameter of 3 mm and a length of 5 mm.

The pellets were dried with a 90 ° C. vacuum dryer to a water content of 0.03% or less, and then kneaded and extruded at a temperature of 240 ° C. using a single screw kneading extruder. After this, a 300 mesh screen filter was installed between the extruder and the gear pump. Then, after passing through an air pump, the melt was extruded from the die through a leaf disk filter having a filtration accuracy of 7 μm and cast.

Thereafter, the melt (molten resin) was extruded onto a triple cast roller. At this time, the touch roller was brought into contact with the most upstream cast roller (chill roller) with a predetermined surface pressure. Use the touch roller described in Example 1 of JP-A-11-235747 (the one described as a double holding roller, but with a thin metal outer cylinder thickness of 2 mm) and used at Tg-5 ° C. did. The temperature of the three cast rollers including the chill roller is such that the most upstream cast roller (first roller) that contacts the touch roller has a predetermined temperature difference (cast roller temperature−touch roller temperature). . Further, the next cast roller (second roller) was a first roller at 5 ° C., and the next cast roller (third roller) was a first roller at −10 ° C.

Then, after trimming both ends (5 cm each of the full width) immediately before winding, knurling with a width of 10 mm and a height of 20 μm was attached to both ends. Further, the film-forming width was 1.5 m, and the film was wound up 3000 m at a film-forming speed of 30 m / min. A polarizing plate protective film T3 302 having a thickness of 60 μm after film formation was produced.

<Preparation of Polarizing Plate Protective Film T3 303>
(Main dope composition)
Acrylic resin Dianal BR85 (Mitsubishi Rayon Co., Ltd., MW95000) 70 parts by mass CAP482-20 (acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000) 30 parts by weight Tinuvin 109 (manufactured by BASF Japan) 1 part by weight Tinuvin 171 (manufactured by BASF Japan) 1 part by weight Methylene chloride 300 parts by weight Ethanol 40 parts by weight Butanol 5 parts by weight The composition was sufficiently dissolved while heating to prepare a dope. In addition, CAP is a cellulose acetate propionate resin.

The produced dope was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2000 mm using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

The solvent was evaporated from the peeled web at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction by a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting a drying zone at 120 ° C and 130 ° C with many rollers, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process having a thickness of 10 μm was performed, and winding was performed to obtain a polarizing plate protective film T3 303 having a thickness of 40 μm and a length of 3000 m.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

<Polarizing plate protective film T4 401>
As a commercially available cellulose ester film, Konica Minolta Tac KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) was used, and a polarizing plate protective film T4 401 was obtained. The constructions and retardation values of the produced polarizing plate protective films T1 to T3 are shown below.

The retardation of the polarizing plate protective film T4 401 was Ro: 1 nm, Rt: 35 nm.

(Measurement of retardation)
In-plane direction retardation value Ro (590) and thickness direction retardation value Rt (590) were measured.

The average refractive index of the film was measured using an Abbe refractometer (4T). Moreover, the thickness of the film was measured using a commercially available micrometer.

Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH, measurement of the retardation of the film at a measurement wavelength of 590 nm in the same environment Went. The above-mentioned average refractive index and film thickness were input, and the values of retardation (Ro) in the in-plane direction and retardation (Rt) in the thickness direction were obtained. The direction of the slow axis was also measured at the same time.

Formula (I): Ro (590) = (n _x −n _y ) × d (nm)
Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d (nm)
[In the above formula, d represents the thickness of the polarizing plate protective film (nm), n _x represents a refractive index in the direction x in which the refractive index in the plane direction is maximized in the film, n _y is the surface of the film In the inward direction, it represents the refractive index in the direction y perpendicular to the direction x, and _nz represents the refractive index in the thickness direction z of the film. Each refractive index is measured at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm. ]

<Preparation of polarizing plate>
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a long polarizer.

Subsequently, the polarizer and the polarizing plate protective films T1 to T4 were bonded in the combinations shown in Table 5 according to the following steps 1 to 5 to produce a viewing side polarizing plate and a backlight side polarizing plate.

Step 1: Dipped in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain polarizing plate protective films T1 to T4 having a saponified side to be bonded to a polarizer.

Step 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off and placed on the polarizing plate protective films T1 to T4 treated in Step 1.

Step 4: The polarizer and the polarizing plate protective films T1 to T4 laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

Step 5: A sample obtained by bonding the polarizer prepared in Step 4 and the polarizing plate protective films T1 to T4 in a drier at 80 ° C. was dried for 2 minutes to prepare the polarizing plates described in Table 5.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

Strip the polarizing plate that was previously bonded to the liquid crystal panel of Sony BRAVIA KDL-46HX800, which uses LEDs for the backlight, and combine the prepared polarizing plates on both sides of the glass surface of the liquid crystal cell with the combinations shown in Table 5 respectively. Bonded to.

At that time, the polarizing plate is bonded so that the absorption axis is in the same direction as the polarizing plate bonded in advance, and the liquid crystal display devices 501 to 501 in Table 5 corresponding to the respective polarizing plates are used. 531 were produced.

The liquid crystal cell of this liquid crystal display device has a COA structure in which a color filter and a thin film transistor are arranged on one of the transparent substrates, and the aperture ratio is 67% as a result of measurement. (See FIG. 1).

(3D glasses)
A polarizing plate protective film T1 106 was bonded to the panel side of the Sony 3D glasses TDG-BR100.

<Evaluation>
The manufactured liquid crystal display device was evaluated for red image evaluation, contrast unevenness, and crosstalk when the head was tilted during 3D video viewing.

<Contrast unevenness>
The measurement was performed after the backlight of the liquid crystal display device was lit continuously for 1 hour in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used, the luminance from the normal direction of the display screen of white display and black display was measured with a liquid crystal display device, and the ratio was defined as the front contrast.

Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
The front contrast at any 10 points of the liquid crystal display device was measured and evaluated according to the following criteria.

◎: There is no variation in front contrast and there is no unevenness. ○: The variation in front contrast is less than 1 to 5% and the variation is small. △: The variation in front contrast is less than 5 to 10% and the variation is slightly Yes ×: Variation in front contrast of 10% or more and large unevenness <Evaluation of viewing angle>
Using a measuring device (EZ-Contrast 160D, manufactured by ELDIM), measurement was performed by displaying white and black in the same manner as the front contrast measurement, and the minimum angle of contrast 50 in the range of 20 to 70 ° was set as the viewing angle. In addition, when the viewing angle exceeds 80 ° in all directions, it is described as 80 °.

<Evaluation of color shift>
Using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM), the color shift in black display is measured, expressed as coordinates (u1 ′, v1 ′) in the CIE1976UCS chromaticity diagram, and an inclination angle of 60 ° from the normal line of the display device. In the 360 ° measurement coordinates, a value having the longest coordinate distance from the front direction (u2 ′, v2 ′) is defined as a color shift. Color shift (ΔCS) = ((u1 ′, v1 ′) 2+ (u2 ′, v2 ′) 2) 1/2
The level of color shift (ΔCS) was evaluated according to the following criteria.

◎: Less than 0.040 ○: 0.040 or more and 0.060 or less ×: More than 0.060 <Evaluation of crosstalk when tilting neck at the time of 3D video viewing>
Immediately after turning on the backlight of the liquid crystal display device in an environment of 23 ° C. and 55% RH, wear 3D glasses and watch 3D images with the glasses tilted at a 25 ° angle, Crosstalk was evaluated according to the following criteria.

A: There is no crosstalk. O: A very weak crosstalk can be seen, but there is no practical problem. Δ: A weak crosstalk is seen. X: Crosstalk is clearly seen. The above evaluation results are shown in Table 5 below.

From the description in Table 5, the configuration of the liquid crystal display device of the present invention has a wide viewing angle, contrast unevenness, color shift, and occurrence of crosstalk during 3D video viewing when the head is tilted, compared to the comparative example. It is clear that the improvement is significant.

Example 2
A liquid crystal display device was prepared and evaluated in the same manner except that the polarizing plate protective film T4 of the backlight-side polarizing plate of the liquid crystal display device prepared in Example 1 was changed to a brightness enhancement film (PCF350 manufactured by Nitto Denko Corporation). However, although the front luminance was improved by 1.1 times compared with the liquid crystal display device manufactured in Example 1, the liquid crystal display device of the present invention reproduced the effects of improving the contrast unevenness, color shift and crosstalk of Example 1.

The liquid crystal display device of the present invention has the characteristic that contrast unevenness and color shift due to the polarizing plate protective film are not conspicuous, and there is no occurrence of crosstalk when an image is observed with the neck tilted. It can be suitably used for a stereoscopic (3D) video display device.

1, 10 Polarizer 2 Polarizing plate protective film T1
3 polarizing plate protective film T2
4, 8 Transparent substrate 5 VA mode type liquid crystal 6 Color filter 7 Thin film transistor 9 Polarizing plate protective film T3
10 Polarizing plate protective film T4
12 Backlight 13 Viewing-side polarizing plate 14 Backlight-side polarizing plate 15 Liquid crystal cell DR1 Feeding direction DR2 Winding direction θi Feeding angle (angle formed between the feeding direction and the winding direction)
CL, CR Gripping tool Wo Width of film before stretching W Width of film after stretching A Liquid crystal shutter glasses A1, A4 Polarizer A2 Liquid crystal cell A3 λ / 4 plate B Liquid crystal display device (for example, television (TV))
C Polarizing plate C1 λ / 4 plate C2 Polarizer C3 Polarizing plate protective film D Liquid crystal cell E Polarizing plate F Backlight a Absorption axis b Slow axis

Claims

A viewing side polarizing plate having a structure in which a polarizer is sandwiched between two polarizing plate protective films, a VA mode type liquid crystal cell, and a backlight side polarizing having a structure in which a polarizer is sandwiched between two polarizing plate protective films A liquid crystal display device having plates in this order from the viewing side, wherein the polarizing plate protective film located on the viewing side of the viewing side polarizing plate is a λ / 4 plate, and is located across the VA mode type liquid crystal cell One of the two polarizing plate protective films is a film having a retardation represented by the following requirement (1), and the other polarizing plate protective film is a retardation represented by the following requirement (2) A liquid crystal display device, characterized by being a film having
(1) The in-plane retardation value Ro (590) defined by the following formula (I) is in the range of 20 to 150 nm, and the retardation value in the thickness direction is defined by the following formula (II). Rt (590) is in the range of 220 to 400 nm.
(2) In-plane retardation value Ro (590) defined by the following formula (I) is in the range of 0 to 10 nm, and the retardation value in the thickness direction is defined by the following formula (II). Rt (590) is in the range of −15 to 15 nm.
Formula (I): Ro (590) = (n x −n y ) × d (nm)
Formula (II): Rt (590) = {(n x + n y ) / 2−n z } × d (nm)
(In the formula, Ro (590) represents the retardation value in the in-plane direction of the film at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm, and Rt (590) represents a temperature of 23 ° C. and a relative humidity of 55% RH. Represents the retardation value in the thickness direction of the film at a measurement wavelength of 590 nm, and d represents the thickness (nm) of the polarizing plate protective film.
n x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film, n y is in the plane direction of the film, the refractive index in the direction y perpendicular to the direction x, n z Represents the refractive index in the thickness direction z of the film. Each refractive index is measured at a temperature of 23 ° C., a relative humidity of 55% RH, and a measurement wavelength of 590 nm. )
The polarizing plate protective film located in the visual recognition side with respect to a liquid crystal cell among the two polarizing plate protective films located on both sides of the said VA mode type liquid crystal cell satisfies the said requirements (1), Item 2. A liquid crystal display device according to item 1.
3. The liquid crystal display device according to claim 2, wherein the polarizing plate protective film includes at least cellulose acetate having an acetyl group substitution degree X of 2.0 ≦ X <2.7.
Of the two polarizing plate protective films located across the VA mode type liquid crystal cell, the polarizing plate protective film located on the backlight side with respect to the liquid crystal cell includes a cellulose ester resin and an acrylic resin, The liquid crystal display device according to any one of claims 1 to 3.
The liquid crystal display device according to any one of claims 1 to 4, wherein the VA mode type liquid crystal cell is an SPVA mode type.
The liquid crystal display device according to any one of claims 1 to 5, wherein an aperture ratio of the liquid crystal display device is 65% or more.
The liquid crystal display device according to any one of claims 1 to 6, wherein the liquid crystal display device has a color filter on array (COA) structure.
The polarizing plate protective film located on the backlight side of the two polarizing plate protective films constituting the backlight side polarizing plate is a brightness enhancement film. The liquid crystal display device according to item.