WO2008018279A1

WO2008018279A1 - Polarizing plate protective film, and polarizing plate and liquid crystal display device using the polarizing plate protective film

Info

Publication number: WO2008018279A1
Application number: PCT/JP2007/064246
Authority: WO
Inventors: Tadanobu Sekiya; Hirokazu Sato
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2006-08-07
Filing date: 2007-07-19
Publication date: 2008-02-14
Also published as: JPWO2008018279A1

Abstract

This invention provides a polarizing plate protective film, which can be produced with high productivity, has polarization scattering anisotropy and has a brightness improving function, and a polarizing plate and a liquid crystal display device using the polarizing plate protective film. The polarizing plate protective film is a polarizing plate productive film having polarization scattering anisotropy and comprising an optical continuous phase formed of a cellulose ester and a domain having an aspect ratio of 2 or more defined by formula (1) and is characterized in that the acetyl group substitution degree X and the propionyl group substitution degree Y of the cellulose ester satisfy requirements represented by formulae (2) and (3) and the absolute value of the angle of the film formation direction of the polarizing plate protective film to the major axis direction of each domain is not more than 25 degrees on average. Formula (1): aspect ratio = major axis/minor axis (wherein the major axis means the absolute maximum length of domain and the minor axis means the distance between two straight lines, parallel to the absolute maximum length, which sandwich a projected domain image therebetween); and formula (2): 2.3 ≤ X + Y ≤ 2.8; and formula (3): 0.7 ≤ Y ≤ 2.3.

Description

Specification

Polarizing plate protective film, polarizing plate and liquid crystal display device using the same

Technical field

The present invention relates to a polarizing plate protective film having polarization scattering anisotropy excellent in productivity, a polarizing plate using the same, and a liquid crystal display device.

Background art

[0002] In recent years, in the field of liquid crystal display devices such as liquid crystal televisions, how efficiently the light energy from the backlight is used is not only from the viewpoint of increasing luminance, but also from the viewpoint of reducing power consumption. Has also become an important technical issue. In that sense, the point is usually how efficiently the 50% (theoretical value) portion that is absorbed when light passes through the dichroic polarizing film can be used.

[0003] In order to solve such problems, conventionally, so-called brightness enhancement films have been studied in order to increase the light use efficiency. For example, as disclosed in Patent Document 1, a birefringent layer and a non-birefringent layer are stacked and reflected using the principle of thin film interference by changing the refractive index. And a film that allows polarization separation by having an axis that does not have a difference in refractive index and transmits light as it is, and a polarization separation film that utilizes the circular dichroism of cholesteric liquid crystal as disclosed in Patent Document 2. It is done. However, all of these films have the disadvantage of high manufacturing difficulty and low productivity. Patent Document 3 discloses a film having polarization scattering anisotropy comprising a dispersed phase of polymer particles in an optical continuous phase having birefringence. This is used to separate polarized light. Although this technique is slightly less difficult to manufacture than the technique of Patent Document 1 or Patent Document 2, it is necessary to adjust both the birefringence and the refractive index. Required. Since the film surface is poorly smooth, it has the disadvantage that it is difficult to integrate with the dichroic polarizing film, which can meet the recent needs for reducing the number of knocklight side members in the field of liquid crystal display devices. It is not a thing. Japanese Patent Application No. 2006-111680 discloses a technique that improves the poor smoothness of Patent Document 3 and integrates a polarizing plate protective film function and a brightness enhancement function. As in Patent Document 3, both the birefringence and the refractive index must be adjusted in that the dispersed phase of the polymer particles is contained in the optically continuous phase having refraction and the polarization scattering anisotropy is provided. High difficulty! If technology is required, difficult points remain.

[0004] As information on a polarizing element having polarization scattering anisotropy with relatively high productivity, for example, acicular scattering particles such as titanium oxide are disclosed. A technique of aligning in a fixed direction and dispersing in a resin is known. In this technology, fine acicular particles having a refractive index different from that of the resin are dispersed in the UV-cured resin, so that reflection occurs with respect to the polarized light in the major axis direction of the particle, and the minor axis direction of the particle. For the polarized light, the particles are sufficiently small with respect to the wavelength of the light beam so that they are not reflected by making a Rayleigh scattering region, thereby providing polarization scattering anisotropy. However, as shown in the example of Patent Document 4, even if a method of dispersing titanium oxide needle-like particles in a specific UV-cured resin is re-examined, the particle aggregation is not sufficiently improved and disclosed. The brightness improvement effect was not obtained. In addition, Patent Document 4 has no description about the polymer resin as an optical continuous phase, and there is no description about the dispersibility of individual domains, which seems to be one of the important issues in practical use. Furthermore, a polarizing plate protective film made using UV-cured resin and scattering particles Z dichroic polarizing film Z polarizing plate laminated in the order of Z cellulose ester polarizing protective film has a humidity with poor moisture permeability balance. It tends to cause warpage due to environmental fluctuations, causing problems such as light leakage.

[0005] On the other hand, it is very common to use a triacetyl cellulose film as a polarizing plate protective film, but in the simple combination category of conventional cellulose esters and the above patent document group, a domain having excellent dispersibility is formed. It was difficult to provide a polarizing plate protective film having sufficient polarization scattering anisotropy and capable of exhibiting a brightness enhancement function when used in a liquid crystal display device.

Patent Document 1: Japanese Patent No. 3621415

Patent Document 2: Japanese Patent Laid-Open No. 2003-227933

Patent Document 3: Special Table 2000-506990

Patent Document 4: Japanese Patent No. 3090890

Disclosure of the invention Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a polarizing plate protective film having excellent productivity and polarization scattering anisotropy, and further a polarizing plate and a liquid crystal display device using the same.

Means for solving the problem

[0007] The above object of the present invention is achieved by the following configurations.

[0008] 1. A polarizing plate protective film having a polarization scattering anisotropy comprising an optical continuous phase having cellulose ester strength and a domain having a aspect ratio of 2 or more defined by the following formula (1): Therefore, the acetyl substitution degree X and the propiol substitution degree Y of the cellulose ester satisfy the conditions specified by the following formulas (2) and (3), and the polarizing plate protective film is formed. A polarizing plate protective film, characterized in that the average value of the absolute values of the angle between the direction and the major axis direction of each domain is within 25 °.

[0009] Formula (1)

Aspect ratio = major axis diameter Z minor axis diameter

(Here, the major axis diameter means the absolute maximum length in the domain, and the minor axis diameter is two straight lines parallel to the absolute maximum length, and two straight lines when the projected domain image is sandwiched between them. Means the distance between.)

Formula (2)

2. 3≤X + Y≤2.8

Formula (3)

0. 7≤Υ≤2.3

2. The minimum value of the refractive index difference between the optical continuous phase and the domain is 0.25 or more, the major axis diameter of the domain is 400 nm or more, lOOOOnm or less, and the minor axis diameter is 50 nm or more. 2. The polarizing plate protective film as described in 1 above, which is 390 nm or less.

[0010] 3. The polarizing plate protective film as described in 1 or 2 above, wherein the protective film is an inorganic compound that is surface-treated with a surface modifier.

[0011] 4. A polarizing plate protective film according to any one of 1 to 3 above, a dichroic polarizing film, a polarizing plate integrated in the order of Z polarizing plate protective film B, Absorption axial force of chromatic polarizing film Polarized light characterized by being in the longitudinal direction of the polarizing plate protective film Board.

[0012] 5. A liquid crystal display device using the polarizing plate as described in 4 above, wherein the polarizing plate protective film as set forth in any one of 1 to 3 is disposed on the knock light side. The invention's effect

An object of the present invention is to provide a polarizing plate protective film having excellent productivity and polarization scattering anisotropy, and further a polarizing plate and a liquid crystal display device using the same.

Brief Description of Drawings

FIG. 1 is a schematic view showing an example of a polarizing plate protective film having a polarization scattering anisotropy containing an optical continuous phase mainly composed of cellulose ester and a domain according to the present invention.

FIG. 2 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method.

FIG. 3 is a block diagram showing an example of a liquid crystal display device that is preferable to the present invention.

Explanation of symbols

[0015] 1, 10 Melting pot

3, 6, 12, 15 Filter

4, 13 Stock tank

5, 14 Liquid feed pump

8, 16 conduit

20 Junction pipe

21 Mixer

30 dice

31 Metal support

32 Web

33 Peeling position

34 Tenter device

35 roll dryer

60 Polarizer

61 Polarizing plate protective film of the present invention 62 Dichroic polarizer

63 Polarizing plate protective film B

64 Light diffuser

65 Light guide plate

66 Nokrai

67 LCD panel display

68 Viewing side polarizing plate

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] The following is a detailed description of the best mode for carrying out the present invention. The present invention is not limited to these.

[0017] A film having polarization scattering anisotropy (hereinafter also referred to as a brightness enhancement film) selectively transmits predetermined polarized light as disclosed in, for example, JP-A-11-509014. A film that can selectively scatter other polarized light and can improve luminance by reusing scattered light when used in a liquid crystal display device.

[0018] The polarizing plate protective film of the present invention is a film having polarization scattering anisotropy and capable of improving luminance when used in a liquid crystal display device, and is an optical continuous phase comprising a cellulose ester. And a domain having an optical anisotropy having an aspect ratio of 2 or more defined by the following formula (1), and the cellulose ester has a acetyl group substitution degree X and a propiol group substitution degree Y. However, the average value of the absolute values of the angle formed by the film forming direction of the polarizing plate protective film and the major axis direction of each domain satisfies the conditions defined by the following formulas (2) and (3): It is characterized by being within °.

[0019] Formula (1)

Aspect ratio = major axis diameter Z minor axis diameter

In the above formula (1), the major axis diameter means the absolute maximum length in the domain, and the minor axis diameter is the two straight lines parallel to the absolute maximum length when the projected domain image is sandwiched between them. Means the distance between two straight lines.

[0020] Formula (2)

2. 3≤X + Y≤2.8 Formula (3)

0. 7≤Y≤2. 3

Furthermore, the minimum value of the difference in refractive index between the optical continuous phase and the domain contained in the polarizing plate protective film is preferably 0.25 or more, and the major axis diameter of the domain is ΟΟηπ! ˜1 OOOOnm, preferably the domain having a minor axis diameter of 50 nm to 390 nm is preferably an inorganic compound surface-treated with a surface modifier.

Hereinafter, the present invention will be described in detail.

[0022] (Optical continuous phase Z domain)

In the present invention, the optical continuous phase refers to a phase in which the refractive index of each part of the polymer film is substantially constant and continuous, and the variation in each part of the refractive index is less than 0.01. Preferably, the variation in refractive index is 0.005 or less, particularly preferably 0.001 or less. Further, in the present invention, the domain means an independent region that exists in the same film as the above-mentioned optical continuous phase and has a refractive index different from that of the optical continuous phase. The “different refractive index” in the present invention means that the difference between the refractive index at any axis of the domain and the refractive index of the optical continuous phase is 0.02 or more. The domain itself may or may not have birefringence.

[0023] The domain according to the present invention has an aspect ratio represented by the following formula (1) of 2 or more.

[0024] Formula (1)

Aspect ratio = major axis diameter Z minor axis diameter

[0025] The domain according to the present invention is a particle having an aspect ratio of 2 or more as defined by the above formula, and the aspect ratio has an aspect ratio of 3 to 100 in the sense of enhancing the orientation of the domain as described later. A range of 5 to 50 is more preferable, and a range of 10 to 30 is particularly preferable.

[0026] A domain having an aspect ratio of 2 or more is preferable because the orientation can be sufficiently enhanced, and as a result, a sufficient brightness enhancement effect with later-described polarization scattering anisotropy can be obtained. [0027] The major axis diameter Z of the domain in the film can be determined using image data observed with an electron microscope.

[0028] For example, the produced film was photographed at a magnification of 20,000 using a transmission electron microscope, and the image was taken using a Canon CanoScan FB 636U scanner, and 300 dpi (in this invention, dpi is 2 This represents the number of dots per 54cm.) Monochrome 256 gray scales, and the scanned image was installed on an Endeavor Pro720L (CPU: Athlon-lGHz, memory: 512MB), a computer made by Epson Direct Corporation. Import to the processing software WinROOF ver 3.60 (Mitani Corporation). Perform domain image extraction on the captured image, and confirm that there are more than 300 domains on the screen after domain image extraction. If the extraction is not sufficient, manually adjust the detection level. Make adjustments to detect and extract any domain. For each domain of image data extracted in this way, the major axis diameter Z minor axis diameter can be measured, and the average aspect ratio of the number of domains can be calculated. At this time, the shape of the domain does not necessarily reflect the individual shape of the particles as shown in the following example. In the present invention, an aggregate having a plurality of constituent particle forces is regarded as one domain. In the case of an indefinite domain, the major axis has the absolute maximum length of the domain, converted to an ellipse with the same area as the domain projection area, and the minor axis is determined according to the above definition.

[0029] As the domain, for example, inorganic particles or particles having an organic compound force can be used.

[0030] Examples of the inorganic particles include TiO (rutile type, anatase type, or mixed crystals thereof.

2

Etc.), calcium silicate (wollastonite, zonotlite, etc.), potassium titanate, aluminum borate, basic magnesium sulfate, glass fiber and the like.

[0031] Examples of the particles having an organic compound power include polymer particles made of silicone resin, fluorine resin and acrylic resin. Particularly preferred is a silicone resin having a three-dimensional network structure. Only one of these inorganic particles or polymer particles can be used as a domain, or multiple types of particles can be used as a domain in the same film.

In the present invention, the domain is subjected to a surface treatment with a surface modifier described later. Preferred to be an inorganic compound.

[0033] The domain has a major axis diameter of OOnm to 10000nm and a minor axis diameter of 50nm to 390nm, from the viewpoint of increasing polarization scattering anisotropy.

[0034] The refractive index of the domain is preferably in the range of 1.3 to 3.0. Further, the minimum value of the refractive index difference between the optical continuous phase and the domain is 0.02 or more, preferably 0.25 or more, and more preferably 0.5 or more, to increase the polarization scattering anisotropy. Liked in terms of.

[0035] In the polarizing plate protective film having polarization scattering anisotropy of the present invention, the domain is preferably contained in an amount of 0.1% by volume or more. Different forces in each case depending on its size For domains with a refractive index of 2.0 or more, it is preferable to make it 5% by volume or less. For grain domains with a refractive index of 1.3 to less than 2.0, 20 It is preferable to make it volume% or less.

[0036] The particles used as the domain according to the present invention are subjected to various surface treatments for the purpose of improving the affinity with the cellulose ester resin and the organic solvent in the film production process. Is preferred.

[0037] For particles that have been sufficiently dried to remove moisture, fatty acid-based, oil-based, surfactant-based, wax-based, silane coupling agent, titanate coupling agent, carboxylic acid-based coupling agent, phosphoric acid-based particle Various modifiers such as coupling agents and polymer systems can be used.

[0038] The treatment method includes a coating method in which the surface is coated with a fatty acid, a metal salt, a surfactant, and the like, a topochemical method in which a coupling agent is bonded to the particle surface, and an organic treatment agent is added in the particle grinding step. There are various methods such as a mechanochemical method in which the monomer is polymerized on the surface of the particle or a capsule method in which the surface of the particle is coated with the polymer by graft polymerization.

[0039] The type of modifier used to treat the particle surface is slightly different depending on the combination of the particle type and cellulose ester-based resin, but coating using a fatty acid-based modifier Treatment method or topochemical treatment power with various silane coupling agents is generally preferred.

[0040] There are two methods for dispersing the surface-treated particles in the cellulose ester-based resin: a method using a disperser and a method using a kneader.

[0041] The former is further divided into media distribution and medialess distribution. As media distribution, Examples thereof include those using a dispersing machine such as a ball mill, a sand mill, and a dyno mill. Examples of the medialess dispersion include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, various mill dispersions or dispersions using a kneader are preferred. As a kneading method, using an extruder having one or two nozzles, pouring the fat from the hot press, and taking the particles from the side when the viscosity has dropped to some extent, Breakage can be minimized and kneadability can be improved. As a mill dispersion method, it is preferable to use one having a bead diameter of 0.1 mm or less because a domain having excellent dispersibility can be obtained while preventing breakage and reaggregation of particles.

[0042] (polarized light scattering anisotropy)

The polarizing plate protective film of the present invention has a polarization scattering anisotropy. Here, having the polarization scattering anisotropy is defined as follows in the present invention. That is, when measuring the total transmitted light amount of the polarizing plate protective film using the linearly polarized incident light, the angle formed by the incident photoelectric field vibration axis and the axis in the film forming direction of the polarizing plate protective film Is changed in the plane of the polarizing plate protective film, when the ratio between the maximum value and the minimum value of the total transmitted light amount (maximum value Z minimum value) is 1.2 or more, the polarizing plate protective film is It is defined as having polarization scattering anisotropy.

[0043] To determine this value, for example, using a haze meter such as NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd., before the incident light hits the polarizing plate protective film to be measured, the iodine-containing polyvinyl alcohol polarized light Inserting a film or the like to linearly polarize the incident light, and measure the total transmitted light amount at each position while changing the rotation angle of the polarizing plate protective film with the incident light as a normal line. It can be easily calculated by obtaining the minimum value. In the present invention, the maximum value Z minimum value ratio of the total amount of transmitted light by the measurement method of the polarizing plate protective film having polarization scattering anisotropy is 1.2 or more, and in order to further improve the brightness enhancement effect, 1. Preferably it is 5 or more 2. More preferably it is 0 or more

[0044] In the present invention, as a means for imparting polarization scattering anisotropy to the polarizing plate protective film, domains having an aspect ratio of 2 or more according to the present invention can be oriented in a specific direction by various methods. It is valid. Examples of the method for orienting domains according to the present invention include domain In the case where the film is uniformly dispersed, there is a method of stretching the film in one direction. In particular, it is preferable to set the production conditions such that the film is stretched in the film forming direction, because the domain can be oriented by a simple method that does not require a separate stretching step. Also, at the stage of film production, the use of high aspect ratio particles, or by adjusting the viscosity and dice shape of the liquid containing the particles and the resin, the method of increasing the shear stress acting on the high aspect ratio particles. , The orientation in a specific direction can be increased. Furthermore, at a stage where there is some fluidity before the film is completely solidified, for example, when using a melt extrusion method to make a film, a method for increasing the film winding speed relative to the extrusion speed, The same effect as stretching can be obtained by a method of solidifying after applying shear stress in one direction while maintaining fluidity. In addition, when the domain has magnetic field anisotropy or electric field anisotropy, a method of solidifying in a support substrate while applying a magnetic field or electric field in one direction can be used. It is also preferable to use these various methods in combination.

[0045] Although polarization degree anisotropy can be greatly improved by providing polarization scattering anisotropy by such a method, a polarizing plate on the backlight side with respect to a liquid crystal cell in a liquid crystal display is provided in the present invention. By using this polarizing plate, a so-called luminance improvement effect is exhibited.

[0046] (Orientation angle)

In the polarizing plate protective film having polarization scattering anisotropy of the present invention, the average value of the absolute values (values that 0 ° to 90 ° can take) between the film forming direction and the major axis direction of each domain; The orientation angle as defined is required to be small in order to increase the polarization scattering anisotropy. Here, as a specific method for obtaining the orientation angle, a transmission electron microscope was used to determine the position of the film slice in the direction of film formation, and then the angle between this axis and 300 domains was measured. A method is adopted in which these totals are obtained by averaging the numbers. In the present invention, the orientation angle of the domain of the polarizing plate protective film having polarization scattering anisotropy is preferably within 25 °, and is preferably within 15 ° in order to further enhance the brightness enhancement effect. It is particularly preferable that it is within the range of °.

[0047] (dichroic polarizing film)

As the dichroic polarizing film according to the present invention, a general dichroic polarizing film with no particular limitation can be used. In general, a dichroic polarizing film means two polarizing plate protective films. It is a dichroic polarizer sandwiched between lumes, allowing light that is almost completely plane-polarized to pass through at maximum half the intensity of incident light. In general, the material particles constituting the dichroic polarizer have crystals or molecules oriented in the same direction. As a dichroic polarizing film for a liquid crystal display device, it is typically obtained by coloring polybutyl alcohol with iodine or a dichroic dye and extending the axis.

FIG. 1 is a schematic view of a polarizing plate protective film having polarization scattering anisotropy including an optical continuous phase mainly composed of cellulose ester and a domain having an aspect ratio of at least an aspect ratio according to the present invention.

[0049] In Fig. 1! /, An optical continuous phase 1 mainly composed of cellulose ester, and domains having an aspect ratio of 2 or more are large in the longitudinal direction (film forming direction or MD direction) of the polarizing plate protective film. It shows a state of being lined up in a generally constant direction. When the refractive index of the optical continuous phase (grease) is nl, the refractive index in the major axis direction of the domain is n2, and the refractive index in the minor axis direction of the domain is n3, nl = n 3 and n2> n3. Sometimes polarized light parallel to the short axis direction of the domain is transmitted and polarized light parallel to the long axis direction is scattered. If the transmitted polarized light is parallel to the transmission axis of the light-absorbing polarizer, the polarized light is transmitted. However, the polarizing plate protective film having polarization scattering anisotropy of the present invention is not limited to the above refractive index relationship. For example, n2> n3> nl force n 3-nl≥0.5 Even in this case, if the short axis diameter of the domain is sufficiently short with respect to the light source wavelength (so-called Rayleigh scattering region), the same polarization scattering anisotropy can be expressed. In this case, as a guideline for the short axis diameter of the domain, 50ηπ! ~ 390 nm is preferred.

[0050] (Cellulose ester)

The optical continuous phase according to the present invention is characterized in that it is made of cellulose ester.

[0051] In particular, the cellulose ester used in the present invention has a cellulose acetate propio that satisfies the conditions defined by the following formulas (2) and (3) in which the degree of substitution of the acetyl group X and the degree of substitution of the propio group Y It is characteristic that it is a nate.

[0052] Formula (2)

2. 3≤X + Y≤2.8

Formula (3)

0. 7≤Υ≤2.3 The degree of substitution of these acyl groups can be measured according to the method specified in ASTM-D817-96.

According to the study by the present inventors, surprisingly, by setting the total acyl substitution degree (X + Y) and the propiol substitution degree (Y) within the above ranges, It has been found that the dispersibility is very good. The reason for this is not clear, but by controlling the hydrophobic Z hydrophilic balance of cellulose acetate propionate within a certain range, the cellulose acetate propionate can be combined with the domain and organic solvent in the film formation process. It is estimated that it may act as a dispersant that maximizes affinity. In fact, even if the propylene group substitution degree (Y) force γ is 0.7 or Y> 2.3, the domain dispersibility is inferior. Apart from this, if Υ> 2.3, there is also a problem that the adhesion with the dichroic polarizing film deteriorates.

[0054] The cellulose that is a raw material of the cellulose ester according to the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. In addition, the cellulose esters from which these strengths are also obtained can be used alone or mixed at an arbitrary ratio.

[0055] In the cellulose ester according to the present invention, when the acylating agent of the cellulose raw material is an acid anhydride (for example, acetic anhydride, propionic anhydride, butyric anhydride), an organic acid methylene chloride such as acetic acid is used. The reaction is performed using an organic solvent such as sulfuric acid and a protic catalyst such as sulfuric acid. Asinolei glaze is acid chloride (CH COCl

3, C H COCl

2 5, C H COC1)

In the case of 3 7, the reaction is carried out using a basic compound such as ammine as the catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804. In cellulose ester, the acyl group reacts with the hydroxyl group of the cellulose molecule. Cellulose molecules are made up of many linked glucose units, with three hydroxyl groups per glucose unit. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cell mouth one triacetate has a acetyl group bonded to all three hydroxyl groups of the glucose unit.

[0056] The force shown below is an example of a method for producing cellulose acetate propionate, which is a kind of cellulose ester according to the present invention. The present invention is not limited to this. <Example of Synthesis of Cellulose Acetate Propionate>

It was synthesized with reference to Example B of JP-T-6-501040.

[0058] The following mixtures A to E were prepared.

[0059] A: Propionic acid: Concentrated sulfuric acid = 5: 3 (mass ratio)

B: Acetic acid: pure water = 3: 1 (mass ratio)

C: Acetic acid: pure water = 1: 1 (mass ratio)

D: Acetic acid: Pure water: Magnesium carbonate = 12: 11: 1 (mass ratio)

E: Aqueous solution in which 0.5 mol of potassium carbonate and 1.0 mol of citrate are dissolved in 14.6 kg of pure water. In a reaction vessel equipped with a mechanical stirrer, 100 parts by mass of purified cellulose, acetic acid 317 parts by mass and 67 parts by mass of propionic acid were added and stirred at 55 ° C for 30 minutes. After the temperature of the reaction vessel was lowered to 30 ° C., 2.3 parts by mass of the mixed solution A was added and stirred for 30 minutes. After cooling the temperature of the reaction vessel to 20 ° C., 100 parts by mass of acetic anhydride and 250 parts by mass of propionic anhydride were added and stirred for 1 hour. After raising the temperature of the reaction vessel to 10 ° C, 4.5 parts by mass of Solution A was added, and the temperature was raised to 60 ° C and stirred for 3 hours. Further, 533 parts by mass of the mixed solution B was added and stirred for 17 hours. Further, 333 parts by mass of the mixed liquid C and 730 parts by mass of the mixed liquid D were added and stirred for 15 minutes. After filtering the insoluble matter, water was added while stirring the solution until the formation of the precipitate was completed, and then the formed white precipitate was filtered. The obtained white solid was washed with pure water until the washing solution became neutral. To this wet product, 1.8 parts by mass of mixed solution E was added, and then dried at 70 ° C. for 3 hours under vacuum to obtain cellulose acetate propionate.

[0060] The degree of substitution of the obtained cellulose ester was calculated based on ASTM-D817-96. As a result, the degree of substitution with the acetyl group was 2.08, and the degree of substitution with the propiol group was 0.72. . When GPC was measured under the above conditions, the Mn force 2000, Mw force S 156000, and MwZMn were 1.7.

[0061] It should be noted that the synthesized cellulose ester is preferably purified to remove low molecular weight components and to remove unacetylated components by filtration.

[0062] The molecular weight of the cellulose ester used in the present invention is in the range of 50 000 to 350,000 in terms of weight average molecular weight (Mw). The power of 60000-300000 is more preferred <, 800 00 ~ 250,000 power especially preferred!

[0063] In the case of acetyl cellulose, if the acetylation rate is to be increased, it is necessary to extend the time for the acetylation reaction. However, if the reaction time is too long, the decomposition proceeds simultaneously, and if the polymer chain is cleaved, the decomposition of the acetyl group occurs, resulting in an undesirable result. Therefore, in order to increase the degree of acetylation and suppress degradation to some extent, it is necessary to set the reaction time within a certain range. It is not appropriate to specify the reaction time because the reaction conditions vary and greatly vary depending on the reactor, equipment, and other conditions. As the degradation of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of degradation can be defined by the value of the weight average molecular weight (Mw) and the Z number average molecular weight (Mn) that are usually used. In other words, in the process of cell mouth 1-triacetate vinegar, it is too long to decompose too much. As an index, the value of weight average molecular weight (Mw) Z number average molecular weight (Mn) can be used.

[0064] The cellulose ester used in the present invention preferably has a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), and MwZMn is 1.4 to 3.9 as described above. More preferably, it is in the range of 1.6 to 3.5.

[0065] The average molecular weight and molecular weight distribution of cenorelose esterol can be measured by a known method using genole permeation chromatography (hereinafter also referred to as GPC). Using this, the number average molecular weight and the weight average molecular weight are measured.

[0066] The measurement conditions are as follows.

[0067] <Gel permeation chromatography: molecular weight measurement by GPC>

As a method for measuring the number average molecular weight by GPC, the sample was diluted with tetrahydrofuran so that the sample solid content concentration was 0.1%. Since particles were included, the particles were removed using a filter, and measurement was performed under the following conditions at a column temperature of 25 ° C.

[0068] Column: TSKgelG5000HXL — TSKgelG2000H XL

Eluent; THF (tetrahydrofuran)

Pump; L6000 (manufactured by Hitachi, Ltd.)

Flow rate: 1. Omi, mm

Detection: RI Model 504 (GL Sciences) Sample concentration; 0.8%

Standard sample 'Calibration curve; Standard polystyrene STK standard polystyrene (manufactured by Tosohichi Co., Ltd.) Use a calibration curve with 13 samples from Mw = 1000000-500. It is preferable that the 13 samples be approximately equally spaced.

[0069] Cellulose esters are also affected by trace metal components in cellulose esters. These are thought to be related to water used in the manufacturing process, but metal ions such as iron, calcium, and magnesium are preferred to contain fewer components that can form insoluble nuclei. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be lost, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. The calcium (Ca) component is abundant in groundwater, river water, etc., and if it is too much, it becomes hard water and is also unsuitable as drinking water. Acidic components such as carboxylic acids and sulfonic acids, and many more It forms a complex with the ligand of, ie, a scum (insoluble starch, turbidity) derived from many insoluble calcium.

[0070] The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. As for the magnesium (Mg) component, too much too much results in insoluble matter, so 0 to 70 ppm is preferable, and 0 to 20 ppm is particularly preferable. Metal components such as iron (Fe) content, calcium and a) content, and magnesium (Mg) content are pre-treated with microdigest wet cracking equipment (sulfuric acid decomposition) and alkali melting. This can be obtained by performing analysis using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

[0071] (Organic solvent)

Organic solvents that dissolve cellulose esters and are useful for cellulose ester solution or dope formation include chlorinated organic solvents and non-chlorinated organic solvents. Examples of chlorinated organic solvents include methylene chloride (methylene chloride), which is suitable for dissolving cellulose esters, particularly cellulose triacetate. In recent years, the use of non-chlorine organic solvents is also being investigated. Non-chlorine organic solvents include, for example, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, 1, 4 —Dioxane, cyclohexanone, ethyl formate, 2, 2, 2—trifluoroethanol, 2, 2, 3, 3 hexafluoro-1 propanol, 1,3 difluoro-2-propanol, 1, 1, 1, 3, 3, 3 Hexafnoroleo 2—Methylolone 2 Prono Norole, 1, 1, 1, 3, 3, 3 Hexafluoro-2-propanol, 2, 2, 3, 3, 3 Pentafluoro-1-propanol, Nitroethane, etc. . When these organic solvents are used for cellulose triacetate, a dissolution method at room temperature can be used, but it is insoluble by using a dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method. This is preferable because it can reduce the amount of materials. For cellulose esters other than cellulose triacetate, it is possible to use methylene chloride. Methyl acetate, ethyl acetate, and acetone are preferably used. Particularly preferred is methyl acetate. In the present invention, the organic solvent having good solubility in the cellulose ester is referred to as a good solvent, and the main effect is shown in the dissolution, and the organic solvent used in a large amount among them is the main (organic) solvent. Or the main (organic) solvent.

[0072] The dope used in the present invention preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. After casting the dope onto the metal support, the solvent starts to evaporate and the alcohol ratio increases, so the dope film (web) gels, making the web strong and easy to peel off from the metal support. It can also be used as a gelling solvent, and when these ratios are small, it also has a role of promoting the dissolution of cellulose ester as a non-chlorine organic solvent. Examples of the alcohol having 1 to 4 carbon atoms include methanol monole, ethanol, n-prono norre, iso prono norre, n-butanol monol, sec butanol and tert-butanol. Of these, ethanol is preferable because it is excellent in dope stability, has a relatively low boiling point, and has good drying properties. These organic solvents are soluble in cellulose esters by themselves, and are therefore poor solvents.

[0073] The concentration of cellulose ester in the dope is 15 to 30 mass ^_0/0, dope viscosity be prepared in a range of 100 to 500 Pa 's, preferable for obtaining a good film surface quality.

[0074] Additives added to the dope include plasticizers, ultraviolet absorbers, antioxidants, dyes, fine particles, and the like. In the present invention, for additives other than fine particles, cellulose It may be added during the preparation of the ester solution! /, Or may be added during the preparation of the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to the polarizing plate used in the liquid crystal image display device. The additive will be described below. [0075] (Plasticizer)

In the polarizing plate protective film according to the present invention or the polarizing plate protective film B described later, a compound known as a so-called plasticizer is used to improve mechanical properties, impart flexibility, impart water resistance, reduce water vapor transmission rate, For example, a phosphoric acid ester or a carboxylic acid ester is preferably used for the purpose of adjusting the determination.

[0076] Examples of the phosphoric acid ester include triphenyl phosphate, tricresyl phosphate, and phenyl diphosphate.

[0077] Examples of the carboxylic acid esters include phthalic acid esters and citrate esters. Examples of the phthalic acid esters include dimethyl phthalate, jetyl phosphate, dioctyl phthalate, and jetyl hexyl phthalate. For example, mention may be made of acetyl cetyl citrate and acetyl butyl thioate. Other examples include butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, and triacetin. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl phthalyl alkyl glycolate include, for example, methyl phthalyl methyl dallicolate, ethyl phthalyl ethyl dallicolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl dallicolate, octyl phthalyl octyl dallylate , Methyl phthalyl ethyl dalicolate, ethyl phthalyl methyl dallicolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl dallicolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl dallicolate, ethyl phthalyl butyl dallicolate , Butyl phthalyl methyl dallicolate, butyl phthalyl ethyl dallicolate, propyl phthalyl butyl dallicolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl Lil OTA tilde Rico rate, O Chi le phthalyl Rume tilde Rico rate, can be mentioned O Chi le phthalyl Rue tilde Rico rate, etc., methyl phthalyl methyl Dali Kore And ethyl phthalyl ethyl dallicolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl dallicolate, and octyl phthalyl octyl dallicolate are preferably used. Two or more of these alkylphthalylalkyl glycolates may be used in combination.

[0078] Polyhydric alcohol esters are also preferably used.

[0079] The polyhydric alcohol used in the present invention is represented by the following general formula (1).

[0080] General formula (1)

R-one (OH) n

1

In the general formula (1), R is an n-valent organic group, n is a positive integer of 2 or more, and the OH group is

1

Represents an alcoholic or phenolic hydroxyl group.

[0081] The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and monostrength rubonic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. A divalent to 20-valent aliphatic polyhydric alcohol ester is preferred.

[0082] Examples of preferable polyhydric alcohols include the following, but the present invention is not limited thereto. Ad-tol, arabitol, ethylene darconol, diethylene glycol, triethylene glycol, tetraethylene dallicol, 1,2 propanediol, 1,3 propanediol, dipropylene glycol, tripropylene glycol, 1,2 butanediol, 1,3 butane Diol, 1,4 butanediol, dibutylene glycol, 1,2,4 butanetriol, 1,5 pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane 1,3 , 5 trio-inole, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene dalycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

[0083] As the monocarboxylic acid used in the polyhydric alcohol ester, known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like, which are not particularly limited, can be used. When using alicyclic monocarboxylic acids or aromatic monocarboxylic acids, moisture permeability, Preferred in terms of improving distillability

[0084] As examples of preferable monocarboxylic acids, the following can be cited. The present invention is not limited thereto.

[0085] 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, the carbon number is 120. Particularly preferred is LO. When acetic acid is contained, the compatibility with the cellulose ester increases, so that it is also preferable to use a mixture of acetic acid and other monocarboxylic acid.

[0086] Preferably, the aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, cabronic acid, enanthic acid, strength prillic acid, pelargonic acid, strength puric acid, 2-ethyruxanoic acid, undecylic acid, Saturated lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, araquinic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, rataceric acid Examples thereof include unsaturated fatty acids such as fatty acid, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

[0087] Examples of preferable alicyclic monocarboxylic acid include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

[0088] Examples of preferable 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 benzene such as biphenylcarboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. An aromatic monocarboxylic acid having two or more rings, or a derivative thereof can be exemplified. Benzoic acid is particularly preferable.

[0089] The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 1500 to 1500, and more preferably 350 to 750. Smaller molecular weights are preferred in terms of moisture permeability and compatibility with cellulose esters, as higher molecular weights are less likely to volatilize.

[0090] The carboxylic acid used in the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Further, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are. [0091] Specific compounds of the polyhydric alcohol ester plasticizer used in the present invention are shown below, but the present invention is not limited thereto.

[0092] [Chemical 1] cn

Three

cn

5 C ₄ H ₃ 0-^-CH ₂ -CH ₂ "0 ^ — CC ₄ H ₉

13 C4HS— c 1 0 "cH ₂ CH— ~ ー

[0093] [Chemical 2]

[0096] These compounds, 1 to the cellulose ester 30 mass ^_0/0, preferably it is preferably contained so as to be 1 to 20 mass%. In order to suppress bleeding out during stretching and drying, a compound having a vapor pressure at 200 ° C. of 1400 Pa or less is preferable.

[0097] These compounds may be added together with cellulose ester or a solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

Furthermore, in the present invention, it is preferable to use an aromatic terminal ester plasticizer represented by the following general formula (2).

[0099] General formula (2) B— (G— A) n— G— B

In the above general formula (2), B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol glycol residue having 6 to 12 carbon atoms, or an alkyl group having 4 to 12 carbon atoms. A xylalkylene glycol residue, 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.

[0100] In the general formula (2)! /, A benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, an oxyalkylene glycol residue or an aryl glycol residue represented by G, It is composed of an alkylene dicarboxylic acid residue or an aryl dicarboxylic acid residue represented by A, and can be obtained by the same reaction as a normal polyester plasticizer.

[0101] Examples of the benzene monocarboxylic acid component of the aromatic terminal ester plasticizer used in the present invention include benzoic acid, tertiary butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, There are ethyl benzoic acid, normal propyl benzoic acid, amino benzoic acid, acetooxy benzoic acid, etc., which can be used singly or as a mixture of two or more.

[0102] Examples of the alkylene glycol component having 2 to 12 carbon atoms of the aromatic terminal ester plasticizer used in the present invention include ethylene glycol, 1,2 propylene glycol, 1,3 propylene glycol, 1,2 butanediol. 1,3 butanediol, 2 methyl 1,3-propanediol, 1,4 butanediol, 1,5 pentanediol, 2,2 dimethyl 1,3 propanediol (neopentyl glycol), 2,2 jetyl 1, 3—propanediol (3,3 dimethylolpentane), 2—n-butyl-2-ethylyl-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, there are 12-O Kuta decanediol, etc., these glycols may be used alone or in combination.

[0103] The aromatic terminal ester may be an oxyalkylene glycol component having 4 to 12 carbon atoms. Examples include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like.

Can be used as a mixture of one or more.

[0104] Further, examples of the arylene glycol component having 6 to 12 carbon atoms of the aromatic terminal ester include hydroquinone, resorcin, bisphenol nore A, bisphenol nore F, bisphenol nole, and the like. It can be used as a mixture of seeds or more.

[0105] 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. They are used as a mixture of one or more of each. Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid.

[0106] The aromatic terminal ester plasticizer has a number average molecular weight of preferably 300 to 2000, more preferably 500 to 1500. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOHZg or less, more preferably the acid value is 0.3 mgKOHZg or less, and the hydroxyl value is 15 mgKOHZg or less.

The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid (carboxyl group present at the molecular end) contained in the sample lg. The acid value and the hydroxyl value are measured in accordance with JIS KO 070 (1992).

[0108] Synthesis examples of the aromatic terminal ester plasticizer used in the present invention are shown below.

Charge 820 parts (5 moles) of phthalic acid, 608 parts (8 moles) of 1,2-propylene glycol, 610 parts (5 moles) of benzoic acid and 0.30 parts of tetraisopropyl titanate as a catalyst into a reaction vessel. While stirring in a nitrogen stream, attach a reflux condenser to recirculate excess monohydric alcohol and continue heating at 130-250 ° C until the acid value is 2 or less. Removed. Next, the distillate is removed under reduced pressure of 6.65 × 10 ³ Pa to 4 × 10 ² Pa or less at 200 to 230 ° C., and then filtered to obtain an aromatic terminal having the following properties: Beauty treatment I got it.

[0110] Viscosity (25 ° C, mPa's); 19815

Acid value; 0.4

Aside from using 500 parts (3.5 moles) of adipic acid, 305 parts (2.5 moles) of benzoic acid, 583 parts (5.5 moles) of ethylene glycol and 0.45 parts of tetraisopropyl titanate as a catalyst in the reaction vessel. Obtained an aromatic terminal ester having the following properties exactly as in Sample No. 1.

[0111] Viscosity (25 ° C, mPa's); 90

Acid value; 0. 05

Sample No. except that 410 parts (2.5 moles) of phthalic acid, 610 parts (5 moles) of benzoic acid, 737 parts (5.5 moles) of dipropylene glycol and 0.40 parts of tetraisopropyl titanate as the catalyst were used in the reaction vessel. An aromatic terminal ester plasticizer having the following properties was obtained in exactly the same manner as in 1.

[0112] Viscosity (25 ° C, mPa's); 43400

Acid value: 0.2

In the following, the ability to show specific compounds of the aromatic terminal ester plasticizer used in the present invention is not limited to this.

[0113] [Chemical 5]

CO {OCH ₂ CH ₂ OCO— <f CO) -OCH ₂ CH ₂ OCO

Mw: 874

CH ₃ CH,

The content of the aromatic terminal ester plasticizer used in the present invention is preferably 120% by mass, particularly preferably 311% by mass, in the cellulose ester film.

(UV absorber)

The polarizing plate protective film of the present invention can contain an ultraviolet absorber. Examples of ultraviolet absorbers that can be used include oxybenzophenone compounds and benzotria. Examples include sol compounds, salicylic acid ester compounds, benzophenone compounds, cyanoate compounds, nickel complex compounds, triazine compounds, and the like, but benzotriazole compounds with less coloring are preferred. Further, ultraviolet absorbers described in JP-A-10-182621, JP-A-8-337574, JP-A-2001-72782, JP-A-6-148430, JP-A-2002-31715, JP-A-2002-169020, Polymer ultraviolet absorbers described in JP-A-2002-47357, JP-A-2002-363420, and JP-A-2003-113317 are also preferably used. Ultraviolet absorbers are excellent in the ability to absorb ultraviolet rays with a wavelength of 370 nm or less from the viewpoint of preventing deterioration of polarizers and liquid crystals, and have little absorption of visible light with a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Is preferred.

[0116] Specific examples of UV absorbers useful in the present invention include 2- (2'-hydroxymonomethylphenol) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert- Butylphenol) benzotriazole, 2— (2 ′ —hydroxy—3 ′ —tert—butyl—5′-methylphenol) benzotriazole, 2— (2 ′ —hydroxy—3 ′, 5′—di—tert —Butylphenol) 1-5 Chronobenzozoazole, 2— (2 ′ —Hydroxy 1 3 ′ — (3, “, 5 Q” —Tetrahydrophthalimidomethyl) 5, —Methylphenyl) benzotriazole, 2, 2-Methylenebis (4- (1, 1, 3, 3-tetramethylbutyl) 6- (2H-benzotriazole-2-yl) phenol), 2- (2'-hydroxy 3'-tert-butyl) 1 '5 (methylphenol) 5 Chronobenzotriazole, 2— (2H Benzotriazole 2 ) -6 (Straight and side chain dodecyl) -4 Methylphenol, Octyl —3— [3 tert Butyl-4-hydroxy-5- (Chromium—2H-benzotriazole-2-yl) phenol (L) propionate and 2-ethylhexyl 3- [3-tert-butyl 4-hydroxy 5-((5-chlorobenzoic acid 2H benzotriazole-2-yl) phenol) propionate, etc. It is not limited to these. As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all of which are manufactured by Ciba Specialty Chemicals) can be preferably used. As an example of the polymer ultraviolet absorber, a reactive ultraviolet absorber RUVA-93 manufactured by Otsuka Chemical Co., Ltd. can be given as an example.

[0117] As specific examples of benzophenone compounds, 2, 4 dihydroxybenzophenone, 2, 2 ' Examples thereof include, but are not limited to, dihydroxy-4-methoxybenzophenone, 2-hydroxy-1-4-methoxy-5-sulfobenzophenone, and bis (2-methoxy-4-hydroxy-5-benzoylmethane).

[0118] The ultraviolet absorber described above preferably used in the present invention is a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber excellent in the effect of preventing deterioration of a highly transparent polarizing plate or liquid crystal element. Benzotriazole-based ultraviolet absorbers are particularly preferably used because they have less unwanted coloration that is preferred by the agent.

[0119] The method of adding the ultraviolet absorber to the dope can be used without limitation as long as it dissolves the ultraviolet absorber in the dope, but in the present invention, the ultraviolet absorber is methyl chloride, methyl acetate. Cellulose ester as a UV absorber solution by dissolving it in a good organic solvent for cellulose esters such as dioxolane, or a mixed solvent of good solvents and poor solvents such as lower aliphatic alcohols (methanol, ethanol, propanol, butanol, etc.) The method of adding the solution to dope is preferred. In this case, it is preferable to make the dope solvent composition and the solvent composition of the ultraviolet absorber solution as close as possible or as close as possible. The content of the ultraviolet absorber is 0.01 to 5% by mass, particularly 0.5 to 3% by mass.

[0120] (Antioxidant)

As the anti-oxidation agent, a hindered phenol compound is preferably used. For example, 2,6-di-tert-butyl-p-taresole, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenol- ) Propionate], triethyleneglycol bis [3- (3-t-butyl-5-methyl-4-hydroxyphenol) propionate], 1,6-hexanediol-bis [3- (3,5-di-t- Butyl-4-hydroxyphenol) propionate], 2, 4 bis- (n-octylthio) -6- (4-hydroxy 3,5 di-tert-butylamino) 1, 3, 5 triazine, 2, 2 thio Diethylenebis [3- (3,5-di-tert-butyl 4-hydroxyphenol) propionate], Octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenol) propionate, N, To N'- Xamethylene bis (3,5 di-tert-butyl 4-hydroxy monohydrocinnamamide), 1, 3, 5 trimethyl 2, 4, 6 tris (3,5 di-tert-butyl 4-hydroxybenzyl) benzene, tris (3,5-di-tert-butyl 4-hydroxybenzyl) monoisocyanurate It is. In particular, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3 (3-, 5-di-tert-butyl-4-hydroxyphenol) propionate], triethylene glycol-bis [3- (3-t Butyl-5-methyl-4-hydroxyphenol) propionate] is preferred. Also, for example, hydrazine-based metal deactivators such as N, N'-bis [3- (3,5-di-tert-butyl 4-hydroxyphenyl) propiol] hydrazine, tris (2,4- It is also possible to use phosphorus-based processing stabilizers such as di (tbutylbutyl) phosphite. The amount of addition of these compounds is preferably lppm to l.0% by weight with respect to the cellulose ester, more preferably 10 to 1 OOOppm.

[0121] (Matting agent)

In the present invention, it is possible to contain fine particles as a matting agent in the polarizing plate protective film, and this makes it easy to carry and take up.

[0122] The matting agent preferably has a primary particle size or secondary particle size of 10 nm to 0.1 µm. A substantially spherical matting agent having a primary particle acicular ratio of 1.1 or less is preferably used.

[0123] As the fine particles, those containing silicon are preferred, and silicon dioxide is particularly preferred. Preferred examples of the silicon dioxide fine particles used in the present invention include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, 0X50, TT600 (above, Nippon Aerosil Co., Ltd.) manufactured by Nippon Aerosil Co., Ltd. It is possible to list those that are commercially available under the trade name of “Made by Co., Ltd.”, and it is possible to use ellosinore 200V, R972, R972V, R974, R202, R812 preferably. Examples of polymer fine particles include silicone resin, fluorine resin and acrylic resin. A silicone resin having a three-dimensional network structure is preferred, for example, Tosnowl 103, 105, 108, 120, 145, 3120 and 240 (above, Toshiba Silicone ( Manufactured by the same company).

[0124] The fine particles of silicon dioxide preferably have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 gZL or more. The average diameter of primary particles is more preferably 5 to 16 nm, and further preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because of lower haze. The apparent specific gravity is preferably 90 to 200 gZL or more, more preferably 100 to 200 gZL or more. Higher apparent specific gravity makes it possible to produce a high-concentration fine particle dispersion, which is preferable because no haze or aggregates are generated. [0125] The addition amount of the matting agent in the present invention is preferably 0.01 to 1. Og force S, more preferably 0.03 to 0.3 g force, more preferably 0.08 to 0.16 g force per lm ^{2 of} the polarizing plate protective film. Even better!

[0126] (Other additives)

In addition, thermal stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, acid titanium, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. . Further, surfactants, peeling accelerators, antistatic agents, flame retardants, lubricants, oils, and the like may be added.

[Film Forming Method]

The polarizing plate protective film of the present invention can be formed by either a solution casting film forming method or a melt extrusion film forming method. Hereinafter, details of the solution casting film forming method will be described as an example.

[0128] (Solution casting film forming method)

The polarizing plate protective film of the present invention is preferably formed by a solution casting film forming method. Here, the solution casting film forming method will be described with reference to FIG.

FIG. 2 is a diagram showing an example of a process schematically showing a dope preparation process, a casting process, and a drying process of the solution casting film-forming method according to the present invention.

[0130] (1) Cellulose ester solution preparation process

In the present invention, a dope is prepared by mixing a domain-forming material, cellulose ester, and a solvent prepared in advance. Specifically, it is preferable to add and mix or disperse a part of the solvent and the domain-forming material in the dissolution vessel, and then add and dissolve the remaining solvent and cellulose ester while stirring. Additives such as plasticizers can be added later to the melting pot or later.

[0131] Alternatively, an additive such as a cellulose ester or a plasticizer may be added to the solvent in the dissolution vessel while stirring, and the domain-forming material may be further added during the dissolution of the cellulose ester. Alternatively, it is possible to obtain a cellulose ester solution by mixing a solvent and an additive such as cellulose ester and a plasticizer, and add the domain-forming material mixed or dispersed in the solvent to this while stirring.

[0132] The method for preparing the cellulose ester solution will be described in more detail. [0133] Additives such as cellulose ester and plasticizer are dissolved in an organic solvent mainly composed of the above-mentioned good solvent for cellulose ester while stirring. For dissolution, a method under normal pressure, a method below the boiling point of the main solvent, a high-temperature dissolution method under pressure above the boiling point of the main solvent, a cooling dissolution method with cooling and dissolution, and a high-pressure dissolution at a fairly high pressure Although there are various dissolution methods such as methods, the high temperature dissolution method is preferably used in the present invention.

[0134] The cellulose ester solution obtained by mixing the domain-forming material, cellulose ester and solvent in the dissolution vessel is dissolved in the cellulose ester and then sent to a filter by a pump and filtered.

[0135] The cellulose ester solution is preferably filtered using a suitable filter medium such as filter paper for filter press. The filter medium in the present invention has a low absolute filtration accuracy to remove insoluble matters and the like! However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. A filter medium with an absolute filtration accuracy of 8 m or less is preferred. More preferred Filter media in the 3-6 m range is even more preferred. Examples of the filter paper include No. 244 and 277 of Azumi Filter Paper Co., Ltd., which are commercially available, and are preferably used.

[0136] Filter media used for filtration can be used with ordinary filter media with no particular restrictions. Plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel are used to remove fibers. This is preferable. Filtration can be carried out in the usual way, but it is a method of filtering while heating or keeping at a temperature in the range of V, in which the organic solvent does not boil under pressure, at or above the normal boiling point of the organic solvent used. However, the increase in the differential pressure before and after the filter medium (hereinafter sometimes referred to as filtration pressure) is preferably small. A preferred temperature range is 45 to 120 ° C., which depends on the organic solvent used, and a more preferred range is 45 to 55 ° C., with 45 to 70 ° C. being more preferred. It is preferable that the filtration pressure is smaller, preferably 0.3 to 1.6 MPa, more preferably 0.3 to 1.2 MPa, and further 0.3 to 1. OMPa. preferable.

[0137] The dope thus obtained is stored in a stock tank, defoamed, and used for casting.

[0138] In this way, the domain forming material and the cellulose ester solution are mixed in the dope kettle. It is preferable to prepare a loop, and the force listed as a method. The cellulose ester solution and part or all of the domain forming material can be mixed in-line. For example, Fig. 2 shows an example of a process for adding a domain forming material in-line. The domain-forming material solution mixed or dispersed in an appropriate solvent is joined with a cellulose ester solution (or sometimes referred to as a dope stock solution) in a joining pipe 20. Immediately before the junction pipe 20, a filter is arranged. For example, a lump or a large foreign matter generated by a path force due to exchange of the filter medium can be removed from the domain forming material solution or the dope stock solution being fed. . Here, a metal filter having solvent resistance is preferably used. The filter medium is preferably a metal from the viewpoint of durability, particularly stainless steel. From the viewpoint of clogging, it is preferable to have a porosity of 60 to 80%. Most preferably, the filtration is performed with a metal filter medium having an absolute filtration accuracy of 30 to 60 / ζ πι and a porosity of 60 to 80%, thereby reliably removing coarse foreign substances over a long period of time. It can be removed and is preferable. Examples of metal filter media with an absolute filtration accuracy of 30 to 60 / ζ πι and a porosity of 60 to 80% include NF-10, NF-12, and NF of Fine pore NF series manufactured by Nippon Seisen Co., Ltd. — 13 mag.

[0139] (2) In-line addition process

When a dope is prepared by previously mixing a domain forming material, a cellulose ester, and a solvent in a melting pot, it is usually unnecessary to add the domain forming material in-line. However, if necessary, all or part of the domain forming material can be mixed in-line. The in-line addition process will be described with reference to FIG. 2. The cellulose ester solution (sometimes referred to as a dope stock solution) and the domain-forming material solution are transferred by the liquid feed pumps 5 and 14, respectively, and filtered by the filters 6 and 15. Transfer through conduits 8 and 16 and join the two liquids in the merge pipe 20. Both combined liquids are transported in layers in the conduit and are difficult to mix as they are. Therefore, after the two liquids are merged, they are transferred to the next process while being sufficiently mixed by the mixer 21 such as an in-line mixer. As an in-line mixer that can be used in the present invention, for example, a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer, manufactured by Toray Engineering) is preferable.

[0140] The dope prepared by the step (2) preferably has a solid content concentration in the dope adjusted to 15% by mass or more, particularly preferably 18 to 30% by mass. Solid concentration in dope If it is too high, the viscosity of the dope becomes too high, and sharkskin or the like may occur during casting to deteriorate the film flatness. Therefore, the content is preferably 30% by mass or less.

[0141] (3) Casting process

The dope prepared up to the previous step is fed to the die 30 and transferred to the endless metal support 31, for example, a stainless steel belt or a metal support 31 such as a rotating metal drum 31 at the casting position. This is a step of casting a dope from the die 30. The surface of the metal support 31 is a mirror surface. A die 30 (for example, a pressure die) is preferable because the slit shape of the die portion can be adjusted and the film thickness can be uniformly blocked. The die 30 includes a coat hanger die, a T die, and the like, and any of them is preferably used. In order to increase the film forming speed, two or more dies may be provided on the metal support 31, and the dope amount may be divided to be stacked.

[0142] The surface temperature of the metal support for casting is 10 to 55 ° C, the temperature of the dope is 25 to 60 ° C, and the temperature of the solution should be equal to or higher than the temperature of the support. It is even more preferable to set the temperature to 5 ° C or higher.

[0143] The higher the solution temperature and the support temperature, the higher the drying speed of the solvent, which is preferable. However, if the temperature is too high, foaming may occur and the flatness may be deteriorated.

[0144] The more preferable range of the temperature of the support depends on the organic solvent used, but is 20 to 55. A more preferable range of C and the solution temperature is 35 to 45 ° C.

[0145] (4) Solvent evaporation process

Web (The name of the dope film after casting the dope on the metal support is the web.) 32 is heated on the metal support 31 and the solvent is evaporated until the web 32 can be peeled from the metal support 31. It is a process to make. To evaporate the solvent, there are a method of blowing wind from the web 32 side, a method of transferring heat with liquid from the back surface of Z or the metal support 31, and a method of transferring front and back forces by radiant heat. The backside liquid heat transfer method is preferred because of its good drying efficiency. A method of combining them is also preferable. In the case of backside liquid heat transfer, it is preferable to heat at or below the boiling point of the organic solvent having the lowest boiling point or the organic solvent having the lowest boiling point.

[0146] (5) Peeling process

In this process, the web 32 where the solvent has evaporated on the metal support 31 is peeled off at the peeling position 33. The The peeled web 32 is sent to the next process. If the residual solvent amount of the web 32 at the time of peeling (the formula described later) is too large, it will be difficult to peel off, or conversely, if it is sufficiently dried on the metal support 31 and then peeled off, A part of may come off. In the present invention, when the thin web is peeled from the metal support, it is preferable to peel the thin web with a force within 170 NZm from the minimum tension that can be peeled as the peeling tension in order to prevent the flatness from being deteriorated or hung up. A force within 140 NZm is more preferable.

[0147] As a method for increasing the film forming speed (the film forming speed can be increased because peeling occurs while the residual solvent amount is as large as possible), there is a gel casting method (gel casting). For example, a poor solvent for the cellulose ester is added to the dope and the gel is cast after casting the dope, and the gel is made by lowering the temperature of the metal support. By gelling on the metal support 31 and increasing the strength of the film at the time of peeling, peeling can be accelerated and the film forming speed can be increased. The web 32 on the metal support 31 can be peeled in the range of 5 to 150% by weight depending on the strength and weakness of the condition and the length of the metal support 31. However, it is peeled off when the amount of residual solvent is larger. In this case, if the web 32 is too soft, the flatness at the time of peeling will be lost, and vertical stripes will be generated due to the peeling tension, and the residual solvent amount at the time of peeling can be determined immediately in consideration of the economic speed and quality. . Therefore, in the present invention, the temperature at the peeling position on the metal support 31 is 10 to 40 ° C., preferably 15 to 30 ° C., and the residual solvent amount of the web 32 at the peeling position is 10 to 10 ° C. 120% by mass is preferred.

[0148] In order to maintain good flatness of the polarizing plate protective film at the time of production, it is preferable to set the residual solvent amount at the time of peeling from the metal support to 10 to 150% by mass, more preferably 70 to It is 150 mass%, More preferably, it is 100-130 mass%. The proportion of the good solvent contained in the residual solvent is preferably 50 to 90%, more preferably 60 to 90%, and particularly preferably 70 to 80%.

[0149] In the present invention, the amount of residual solvent can be expressed by the following formula.

[0150] Residual solvent amount (mass%) = {(M-N) / N} X 100

Here, M is a mass of the web at an arbitrary time point, and is a mass measured by the following gas chromatography. N is a mass when the M is dried at 110 ° C. for 3 hours. Measurement is Measured by gas chromatography with a dspace sampler. In the present invention, gas chromatography 5890 type SERISII manufactured by Hewlett-Packard Company and headspace sampler HP7694 type were used, and the measurement was performed under the following measurement conditions.

[0151] Headspace sampler heating conditions: 120 ° C, 20 minutes

GC introduction temperature: 150 ° C

Temperature rise: 40 ° C, hold for 5 minutes → 100 ° C (8 ° CZ minutes)

Column: DB & WAX manufactured by J & W (inner diameter 0.32mm, length 30m).

[0152] (6) Drying process

After peeling, generally, the web 32 is dried using a roll drying device 35 that alternately conveys the web 32 through a plurality of rolls and a tenter device 34 that grips and conveys both ends of the web 32. In FIG. 2, the present invention is not limited to the force arrangement in which the roll drying device 35 is arranged after the tenter device 34. As a means of drying, hot air is generally blown on both sides of the web, but there is also a means of heating by applying a microwave instead of the wind. Too rapid drying tends to impair the flatness of the finished film. The drying temperature is usually in the range of 40 to 250 ° C throughout. The drying temperature, amount of drying air, and drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of solvents used. 37 is winding of the finished polarizing plate protective film. In the step of drying the polarizing plate protective film, the residual solvent amount is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

[0153] The protective film for polarizing plate of the present invention is formed into a film by a casting process after preparing a dope to which a domain-forming material is added. As a method for orienting the added domain-forming material, a film is formed during film production. It is possible to adopt a method of stretching the film in the TD or MD direction, or a method of making a dope flow during casting and orienting the domain forming material along this flow. Furthermore, the orientation of the domain forming material can be promoted by an electric field or a magnetic field. In particular, in the present invention, it is preferable to use a method of stretching at least in the MD direction in order to orient the domain forming material.

[0154] (7) Stretching process (also called tenter process)

The polarizing plate protective film of the present invention adjusts the birefringence by stretching, or arranges the domains. The polarization scattering anisotropy can be controlled by adjusting the directionality. A film containing a solvent can be stretched during the production of the solution casting method, or a film in a state where the solvent is dried can be stretched. The stretching temperature is preferably performed at a glass transition temperature of the film of 20 ° C to a temperature at which the film flows. Here, the glass transition temperature of the film can be measured by a known method. Stretching can be performed in the film forming direction or the width direction, but in the present invention, it is preferable to stretch at least in the longitudinal direction. By stretching, the ratio of domains oriented in the stretching direction can be increased.

[0155] The stretching step will be described in more detail. The stretch ratio in producing the polarizing plate protective film of the present invention is 1.01 to 3 times, preferably 1.5 to 3 times, with respect to the film forming direction or the width direction. When stretching in the biaxial direction, the side to be stretched at a high magnification is 1.01 to 3 times, preferably 1.5 to 3 times, and the stretching ratio in the other direction is 0.8 to 1.5. The film can be stretched by a factor of preferably 0.9 to 1.2.

[0156] This makes it possible to obtain a polarizing plate protective film with good flatness, in combination with the preferable polarizing plate protective film having polarization scattering anisotropy of the present invention. It is preferable to use a tenter to maintain these widths or stretch in the transverse direction during the film forming process.

[0157] (8) Winding process

This is a step of winding the web after drying as a film. When the amount of the residual solvent that finishes drying is 0.5% by mass or less, preferably 0.1% by mass or less, a film having good dimensional stability can be obtained. Winding methods include tension control methods such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress. You can use them properly.

[0158] The thickness of the polarizing plate protective film of the present invention varies depending on the purpose of use, but from the viewpoint of thinning the liquid crystal display device, the finished film is preferably in the range of 10 to 150 / ζ πι. ~: The range of LOO μm is more preferable, and the range of 40 to 80 μm is particularly preferable. If it is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If it is too thick, the advantage of the thin film over the conventional polarizing plate protective film is lost. Film thickness adjustment In order to obtain a desired thickness, it is preferable to control the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the metal support, and the like. In addition, it is preferable that the film feed detecting means is fed back to each of the above devices and adjusted using a film thickness detecting means as a means for making the film thickness uniform.

[0159] In the step up to the drying of the force immediately after casting through the solution casting film-forming method, the atmosphere in the drying apparatus may be air, but is performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. May be.

[0160] (Polarizing plate and liquid crystal display device)

Next, the case where the polarizing plate protective film having polarization scattering anisotropy of the present invention is used for a liquid crystal display device will be described.

[0161] The polarizing plate protective film having polarized light scattering anisotropy of the present invention has an advantage that a conventional polarizing plate production process can be utilized because the resin constituting this is a cellulose-based resin. The polarizing plate protective film according to the present invention is a water-soluble adhesive material such as water paste for a light-absorbing polarizer utilizing a dichroic dye by stretching a polybulal alcohol derivative that is commonly used. The film can be directly bonded with a thin film, so it is greatly superior in productivity.

[0162] Further, since the polarizing plate protective film of the present invention has a characteristic as a polarizing plate protective film composed of cellulose ester, it is polarized in a roll shape as a long film having a brightness enhancement function. Since it can be delivered to the plate manufacturing process, the roll-shaped film has the advantage that it is not necessary to use a protective sheet for preventing dust from being attached to the roll film.

[0163] The polarizing plate of the present invention preferably has a configuration of a polarizing plate protective film Z having a polarization scattering anisotropy Z a dichroic polarizing film, and a polarizer Z polarizing plate protective film B.

[0164] In the present invention, the polarizing plate protective film, the polarizer, and the polarizing plate protective film B having polarization scattering anisotropy are all preferably long films. It is preferable to use a roll toe roll.

[0165] When used in a liquid crystal display device, it is preferable that a polarizing plate protective film having polarization scattering anisotropy is disposed on the most adjacent side of the polarizing plate in the transmissive liquid crystal display device. Yes.

[0166] The polarizing plate protective film B located opposite to the polarizer with respect to the polarizing plate protective film having polarization scattering anisotropy may be a TAC film represented by a general cellulose acetate resin. The polarizing plate protective film B may be a polarizing plate protective film having a viewing angle widening film or a retardation film function. When used as a polarizing plate, a functional film or a functional layer for improving display quality with respect to contrast or color may be provided on the polarizing plate protective film B via an adhesive layer or an adhesive layer.

[0167] The polarizing plate protective film B used in the polarizing plate of the present invention may be a cellulose ester film or a polarizing plate protective film other than the cellulose ester film! / ヽ. In addition, the present invention is not limited to the properties of the polarizing plate protective film B, and the polarizing plate protective film of the present invention has moisture permeability regardless of the characteristics of the polarizing plate protective film B. In this case, there is an advantage that moisture contained in the production of the polarizing plate can be removed by a drying process.

[0168] Accordingly, in the present invention, the moisture permeability when a polarizing plate prepared is at the preferred instrument 100gZm ² Zday more is at 50gZm ² Zday more polarizing plate protective film having a polarization scattering anisotropy of the present invention This is preferable in terms of reducing the drying load. On the other hand, the upper limit of the moisture permeability of the polarizing plate protective film having scattering anisotropy of the present invention is preferably 1500 gZm ² Zday or less, more preferably 1200 g / m ² from the viewpoint of maintaining the polarizing ability of the polarizer. / da y or less.

[0169] When the polarizing plate protective film is alkali-capped with an alkaline solution, the wettability to water increases, which leads to adhesion with the polyvinyl alcohol-based paste represented by the aforementioned water paste. . In the polarizing plate protective film of the present invention, at least one surface has a contact angle with water before saponification treatment of 60 ° or more and 80 ° or less, and a contact angle with water after saponification treatment of 15 ° or more and 40 ° or less. It is preferable that

[0170] Examples of the polarizer preferably used for the polarizing plate of the present invention include a polyvinyl alcohol polarizing film, which is obtained by dyeing polybutyl alcohol film with iodine and dichroic dye. There is something. As the polybula alcohol film, a modified polybulal alcohol film modified with ethylene is preferably used. For the polarizer, a polybulal alcohol aqueous solution is formed into a film, and this is uniaxially stretched and dyed. After the dyeing, the polarizer is preferably uniaxially stretched and then subjected to a durability treatment with a boron compound. . The film thickness of the polarizer is 5 to 40 m, preferably 5 to 30 / ζ πι, and particularly preferably 5 to 20 / ζ πι. One side of the polarizing plate protective film of the present invention is bonded to the surface of the polarizer to form a polarizing plate.

[0171] Since the polarizer is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high temperature and high humidity environment, the stretching direction (usually the longitudinal direction) shrinks and is orthogonal to the stretching. Extends in the direction (usually the width direction). As the thickness of the polarizing plate protective film becomes thinner, the rate of stretching of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizer increases. Usually, the direction of stretching of the polarizer is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when the polarizing plate protective film is used as a thin film, it is particularly important to suppress the stretching rate in the casting direction. is there. Since the polarizing plate protective film of this invention is excellent in dimensional stability, it is used suitably as such a polarizing plate protective film.

[0172] Next, a polarizing plate protective film 好ましい preferred in the present invention will be described.

[0173] The polarizing plate protective film 偏光板 preferably used in the present invention is the other polarizing plate protective film disposed with the polarizer sandwiched between the polarizing plate protective film having polarization scattering anisotropy of the present invention. It is a film.

[0174] Polarizing plate protective film Β is not particularly limited, for example, polyester film such as polyethylene terephthalate and polyethylene naphthalate, polyethylene film, polypropylene film, polycyclohexylene film, cellophane, cellulose acetate , Cellulose acetate butyrate vinyl, cellulose acetate phthalate film, cellulose acetate propionate film, cellulose ester such as cellulose acetate triacetate, cellulose nitrate or other derivatives thereof, polyvinyl chloride Reden film, polybulol alcohol film, ethylenebulol alcohol film, syndiotactic polystyrene film, polycarbonate film , Cycloolefin polymer film (for example, ARTON (manufactured by JSR), ZEONEX, ZENOA (manufactured by ZEON)), polymethylpentene film, polyetherketone film, polyethersulfone film, polysulfone film, poly Ether ketone Examples thereof include a mid film, a polyamide film, an acrylic film, and a polyacrylate film.

[0175] In the present invention, cellulose ester films such as cellulose acetate propionate film and cellulose triacetate film (TAC film) (for example, Co-Camino Nortack KC8UX2M, KC4UX manufactured by Co-Caminoltop Co., Ltd.) KC5UX, KC4UY, KC 4UE ゝ KC4FR—1, KC4FR—2, KC8UY ゝ KC12UR ゝ KC8UY—HA ゝ KC8U X—RHA, etc. are preferably used), cycloolefin polymer film, polycarbonate film, polyester film or polyacrylic The film is preferable in terms of transparency, mechanical properties, and lack of optical anisotropy, and in particular, the cellulose ester film and the cycloolefin polymer film are preferable. The most preferred is cellulose ester film with excellent saponification ability. These resin films may be films formed by a melt casting method or a solution casting method.

[0176] The polarizing plate protective film B used in the present invention preferably has a retardation value Ro defined by the following formula of 0 to 300 nm and a retardation value Rt of -600 to 600 nm. Also, more preferable ranges are Ro value 0 to 120 nm, Rt value is in the range of 400 to 400 nm, especially preferred! /, Ranges are Ro value force ^ to lOOnm and Rt value is in the range 300 to 300 nm. .

[0177] Formula (I)

Ro = (ηχ— ny) X d

Formula (Π)

Rt = {(nx + ny) / 2-nz} X d

In the formula, nx, ny, and nz are the refractive index nx at 23 ° CRH and 590 nm (the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction), and the refractive index ny (in the film plane). The refractive index in the direction perpendicular to the slow axis), the refractive index nz (the refractive index of the film in the thickness direction), and d is the thickness (nm) of the film.

[0178] When the polarizing plate protective film B used in the present invention is used as an optical compensation film of a VA liquid crystal display device having a VA mode liquid crystal cell, the Ro value is set to 20 to 150 nm, The Rt value is preferably 70 to 400 nm. The Ro value is more preferably 30 to 100 nm. When two optical compensation films are used in a VA liquid crystal display device, the Rt value of the film is preferably 70 to 250 nm! /. When a single optical compensation film is used for a VA liquid crystal display device, the Rt value of the film is preferably 150 to 400 nm! /.

[0179] The polarizing plate protective film B used in the present invention is also suitable for a polarizing plate protective film used in a transverse electric field switching mode type (both IPS mode type) liquid crystal display device. It is preferable that the retardation value Ro of the polarizing plate protective film B, Rth force 0 nm≤Ro≤2 nm, and 15 nm≤Rth≤15 nm. More preferably, Onm ≤ Ro ≤ 0.5 nm and 1511111 ≤ 1¾11 ≤ 511111.

[0180] When the polarizing plate protective film B used in the present invention is used as a polarizing plate protective film used in a horizontal electric field switching mode type (also referred to as IPS mode type) liquid crystal display device, the polarizing plate protective film B is Even though it is preferable to contain an acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less, it has an ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule and an aromatic ring in the molecule. Polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with ethylenically unsaturated monomer Xb having a hydrophilic group, more preferably ethylene having no aromatic ring and no hydrophilic group in the molecule A polymer X having a weight average molecular weight of 5000 or more and 30000 or less, obtained by copolymerization of the polymerizable unsaturated monomer Xa and an ethylenically unsaturated monomer Xb having no hydrophilic ring in the molecule and having a hydrophilic group; Preferably contains a weight average molecular weight 5 00 3,000 a polymer Y obtained by polymerization of ethylenic unsaturated monomer Ya having no ring.

[0181] <Polymer X, Polymer Y>

The polymer X used in the present invention does not have an aromatic ring and a hydrophilic group in the molecule, and the ethylenically unsaturated monomer Xb does not have an aromatic ring in the molecule and has a hydrophilic group. Is a polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization of

[0182] Preferably, Xa is an acrylic or methacrylic monomer having no aromatic ring and no hydrophilic group in the molecule, and Xb is an acrylic or methallyl monomer having no aromatic ring in the molecule and a hydrophilic group. [0183] The polymer X used in the present invention is represented by the following general formula (X).

[0184] General formula (X)

-(Xa) m- (Xb) n- (Xc) p- More preferably, it is a polymer represented by the following general formula (X-1).

[0185] General formula (X— 1)

[CH—C (one R) (—CO R)] m— [CH—C (one R) (—CO R—OH) —] n

2 1 2 2 2 3 2 4

-[Xc] p-

(In the formula, R R represents H or CH. R represents an alkyl group having 1 to 12 carbon atoms,

1 3 3 2

Represents an alkyl group. R represents —CH 2 —C 2 H or C 2 H. Xc, Xa Xb

4 2 2 4 3 6

Represents a polymerizable monomer unit. m n and p represent a molar composition ratio. However, m ≠ 0 n ≠ 0 k ≠ 0 m + n + p = 100. )

Monomers as monomer units constituting the polymer X used in the present invention are listed below, but are not limited thereto.

[0186] In X, the hydrophilic group is a group having a hydroxyl group or an ethylene oxide chain! Uh.

[0187] The ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule includes, for example, methyl acrylate, ethyl acrylate, propyl acrylate (in-), butyric acrylate (nis-t- ), Pentyl acrylate (nis—), hexyl acrylate (ni 1), heptyl acrylate (ni 1), octyl acrylate (ni 1), nor acrylate (ni 1), myristyl acrylate ( ni), acrylic acid (2-ethylhexyl), acrylic acid (ε-strength prolatatone), acrylic acid (2-hydroxyethyl), acrylic acid (2-ethoxyethyl), etc., or the above acrylic ester is methacrylic acid You can list those that have been changed to esters. Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (in—) are preferable.

[0188] The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or a methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid ( 2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or these acrylic acids with methacrylic acid List what you replaced Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxycetyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

[0189] Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

[0190] The molar composition ratio m: n of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, and more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

[0191] The molar composition ratio of Xa is high, and the compatibility with the cellulose ester is improved, but the retardation value Rth in the film thickness direction is increased. When the molar composition ratio of Xb is large, the above-mentioned compatibility is deteriorated, but the effect of reducing Rth is high. In addition, if the molar composition ratio of Xb exceeds the above range, there is a tendency for haze to occur during film formation. It is preferable to optimize these to determine the molar composition ratio of Xa and Xb.

[0192] The molecular weight of the polymer X has a weight average molecular weight of 5000 or more and 30000 or less, more preferably <is 8000 or more and 25000 or less.

[0193] By setting the weight average molecular weight to 5,000 or more, it is preferable to obtain advantages such as little dimensional change of the cellulose ester film under high temperature and high humidity, and little curling as a polarizing plate protective film. When the weight average molecular weight is within 30000, the compatibility with cellulose ester is further improved, and bleeding out under high temperature and high humidity and further haze generation immediately after film formation are suppressed.

[0194] 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 molecular weight adjusting methods include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercabtan, octyl thioglycolate, and the like. The polymerization temperature is usually from room temperature to 130 ° C, preferably from 50 ° C to 100 ° C. This temperature or the polymerization reaction time can be adjusted.

[0195] The weight average molecular weight can be measured by the following method.

[0196] (Method for measuring weight average molecular weight)

The weight average molecular weight Mw was measured using gel permeation chromatography. [0197] The measurement conditions are as follows.

[0198] 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 (GL Science Co., Ltd.)

Pump: L6000 (manufactured by Hitachi, Ltd.)

Flow rate: 1. Om mm

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoichi Co., Ltd.) Mw = 1000000-500 13 Sampu Nore [This calibration curve was used. 13Sampnore ί, use it at regular intervals.

[0199] The polymer 用い used in the present invention is a polymer having an aromatic ring and having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing the ethylenically unsaturated monomer Ya. A weight average molecular weight of 500 or more is preferable because the residual monomer in the polymer decreases. Moreover, it is preferable to set it to 3000 or less in order to maintain the reduction value Rth reduction performance. Ya is preferably an acrylic or methacrylic monomer without an aromatic ring.

[0200] The polymer Y used in the present invention is represented by the following general formula (Y).

[0201] General formula (Y)

One (Ya) k— (Yb) q—

More preferred is a polymer represented by the following general formula (Y-1).

[0202] General formula (Y— 1)

[CH -C (-R) (-CO R)] k- [Yb] q-

2 5 2 6

(In the formula, R represents H or CH. R has 1 carbon.

Represents an alkyl group or a cycloalkyl group of 5 3 6 to 12; Yb represents a monomer unit copolymerizable with Ya. k and q represent molar composition ratios. However, k ≠ 0 and k + q = 100. )

Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Y b may be plural. k + q = 100 q is preferably 0-30.

[0203] No aromatic ring! /, Ethylenically unsaturated monomer Ya constituting polymer Y obtained by polymerizing ethylenically unsaturated monomer Ya is an acrylate ester such as methyl acrylate, ethyl acrylate Propyl acrylate (in-), butyl acrylate (nis-t 1), pentyl acrylate (nis), hexyl acrylate (ni 1), heptyl acrylate (ni 1), octyl acrylate (ni 1), acrylic acid (n-i), myristyl acrylate (ni), cyclohexyl acrylate, acrylic acid (2-ethylhexyl), acrylic acid ( _ε -force prolatathon), acrylic Acid (2-hydroxyethyl), acrylic acid (2 hydroxypropyl), acrylic acid (3 hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2 hydroxybutyl) ), Methacrylic acid esters obtained by replacing the above acrylic acid esters with methacrylic acid esters; examples of unsaturated acids include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, and the like. .

[0204] Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of the bull ester include, for example, vinyl acetate, butyl propionate, vinyl butyrate, valerate valerate, and valerate pivalate. , Caproic acid bull, strength puric acid bull, lauric acid bull, myristic acid bull, palmitate bull, stearic acid bull, cyclohexane carbonic acid bull, octyl acid bull, methacrylate bull, crotonic acid bull, sorbic acid bull, cinnamon Acid bur is preferred. Yb may be plural.

[0205] In order to synthesize polymer XY, it is desirable to use a method in which the molecular weight can be adjusted as much as possible by a method that does not increase the molecular weight that is difficult to control the molecular weight in ordinary polymerization. As a powerful polymerization method, a method using a peroxide polymerization initiator such as cumene peroxide or t-butyl hydroloxide, a method using a polymerization initiator in a larger amount than a normal polymerization, a polymerization initiator In addition, a method using a chain transfer agent such as a mercapto compound or carbon tetrachloride, a method using a polymerization terminator such as benzoquinone dinitrobenzene in addition to the polymerization initiator, and JP 2000-128911 or 2000. -A method of bulk polymerization using a compound having one thiol group and a secondary hydroxyl group as described in JP-A-344 823, or a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, the polymer Y is preferably a polymerization method in which a compound having a thiol group and a secondary hydroxyl group in the molecule is used as a chain transfer agent. In this case, the terminal of the polymer Y has a hydroxyl group and thioether resulting from the polymerization catalyst and the chain transfer agent. This terminal residue can adjust the compatibility between Y and cellulose ester.

[0206] The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mgKOH / g]!

[0207] (Measuring method of hydroxyl value)

This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bound to a hydroxyl group when sample lg is acetylated. Specifically, sample Xg (about lg) is precisely weighed in a flask, and 20 ml of acetylating reagent (20 ml of acetic anhydride with pyridine added to 400 ml) is accurately added to this. Attach an air condenser to the mouth of the flask and heat in a 95-100 ° C glycerin bath. After 1 hour and 30 minutes, cool and add 1 ml of purified water from the air cooling tube to decompose acetic anhydride into acetic acid. Next, titration is performed with a 0.5 mol ZL aqueous solution of potassium hydroxide and potassium ethanol using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. In addition, as a blank test, titrate without adding a sample and obtain the inflection point of the titration curve. The hydroxyl value is calculated by the following formula.

[0208] Hydroxyl value = {(B— C) X f X 28. 05ZX} + D

(In the formula, B is the amount of 0.5 mol ZL of hydroxyaluminum potassium ethanol solution used for the blank test (ml), C is the amount of 0.5 molZL of hydroxyaluminum potassium carbonate solution used for titration (ml) , F is a factor of 0.5 mol ZL potassium hydroxide ethanol solution, D is the acid value, and 28. 05 is 1Z2 of lmol 56.11 potassium hydroxide.)

The above-mentioned polymer X and polymer Y are both highly compatible with cellulose ester, have excellent productivity without evaporation and volatilization, have good retention as a protective film for polarizing plates, and have low moisture permeability and dimensional stability. Are better.

[0209] The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (III) and (IV). If the content of polymer X is Xg (mass% = mass of polymer X / mass of cellulose ester X 100) and the content of polymer Y is Yg (mass%), Formula (III)

5≤Xg + Yg≤35 (mass%)

Formula (IV)

Preference for formula (III)! /, The range is 10 to 25% by weight.

[0210] If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y have a sufficient effect for reducing the retardation value Rth. If the total amount is 35% by mass or less, the adhesiveness with a polyvinyl alcohol polarizer is good.

[0211] Polymer X and polymer Y can be added directly to the dope solution as a material constituting the dope solution described later, or dissolved in advance in an organic solvent in which cellulose ester is dissolved.

[0212] The physical properties of the polarizing plate protective film having polarizing scattering anisotropy and the polarizing plate protective film B of the present invention are summarized below.

[0213] (Transmissivity of polarizing plate protective film B)

A high transmittance is required as a member of an LCD display device, and the 500 nm transmittance of the manufactured polarizing plate protective film B obtained by combining and adding the above-mentioned additives is preferably from 85 to 100%, and from 90 to : L00 ⁰ / _o force more preferred, 92-: L00 ⁰ / _o force most preferred! / ,. 400mn transmittance ί or 40 to 100% is preferred 50 to 100% is more preferred 60 to 100% is most preferred. In addition, ultraviolet absorption performance may be required. In such a case, the transmittance of 380 nm is preferably 0 to 5%, more preferably 0 to 5%, and most preferably 0 to 3%.

[0214] (Thickness distribution in the width direction of the polarizing plate protective film)

The polarizing plate protective film of the present invention preferably has a thickness distribution R (%) in the width direction of 0≤R (%) ≤5%, more preferably 0≤R (%) ≤3 %, Particularly preferably 0 ≤ R (%) ≤ 1%.

[0215] (Haze value of polarizing plate protective film B)

The polarizing plate protective film B of the present invention has a haze value of preferably 2% or less, more preferably 1.5%, and most preferably 1% or less.

[0216] (Elastic modulus of polarizing plate protective film) The elastic modulus is preferably in the range of 1.5 to 5 GPa, more preferably in the range of 1.8 to 4 GPa, and particularly preferably in the range of 1.9 to 3 GPa.

[0217] Further, the stress at break is preferably in the range of 50 to 200 MPa, more preferably in the range of 70 to 150 MPa, and even more preferably in the range of 80 to: LOOMPa.

[0218] The elongation at break at 23 ° C and 55% RH is preferably in the range of 20-80% 30-6

The range of 0% is more preferable. The range of 40-50% is most preferable.

[0219] The hygroscopic expansion coefficient is preferably in the range of 1 to 1%, more preferably in the range of 0.5 to 0.5%, and most preferably 0 to 0.2% or less.

[0220] Further, it is preferable that the bright spot foreign matter is 0 to 80 Zcm ² , and more preferably 0 to 60 Zcm ^{2 is} the range of 0 to 30 pieces / cm ^2. Most preferred.

[0221] (Center line average roughness of polarizing plate protective film (Ra))

When a polarizing plate protective film is used as an LCD member, high flatness is required to reduce the light leakage of the film. The center line average roughness (Ra) is a numerical value defined in JIS B 0601. Examples of the measuring method include a stylus method or an optical method.

[0222] The center line average roughness (Ra) of the polarizing plate protective film of the present invention is preferably 20 nm or less, more preferably lOnm or less, and particularly preferably 4 nm or less.

[0223] 《Polarizing plate》

The polarizing plate of the present invention and the liquid crystal display device of the present invention using the polarizing plate will be described.

[0224] The polarizing plate can be produced by a general method. The polarizing plate protective film having polarization scattering anisotropy of the present invention that has been treated with an alkaline acid is completely cured on at least one surface of a polarizer prepared by immersing and stretching a polybulal alcohol film in an iodine solution. It is preferable to bond together using an aqueous polyvinyl alcohol solution. It is preferable to paste the polarizing plate protective film B on the other surface.

The polarizing plate according to the present invention is a polarizing plate integrated in the order of a polarizing plate protective film having a polarization scattering anisotropy according to the present invention, a Z dichroic polarizing film, and a Z polarizing plate protective film B. The absorption axis of the dichroic polarizing film is in the longitudinal direction of the polarizing plate protective film. With this configuration, the polarizing plate protective film of the present invention is applied to a liquid crystal display device. Also functions as an excellent brightness enhancement film for V.

[0226] The polarizing plate can be constituted by further laminating a protective film on one surface of the polarizing plate and a separate film on the other surface. 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.

[0227] <Liquid crystal display device>

By making the polarizing plate of the present invention a liquid crystal display device bonded to at least the surface of the liquid crystal cell on the backlight side, the luminance can be improved and the liquid crystal display device of the present invention having excellent visibility can be produced. . The polarizing plate protective film of the present invention is of various drive systems such as reflective, transmissive, transflective L CD or TN, STN, OCB, HAN, VA (PVA, MVA), IPS, etc. Preferably used in LCD. In particular, a large-screen display device with a 30-inch screen or more has the effect that eyes are not tired even when viewing for a long time with little color unevenness and wavy unevenness.

[0228] Although the polarizing plate of the present invention can also be arranged on the viewing side, it is preferable to arrange it only on the backlight side of the liquid crystal panel from the viewpoint of avoiding visual hindrance based on backscattering, etc.

[0229] FIG. 3 shows the force shown in the configuration example of the liquid crystal display device preferable for the present invention, but the present invention is not limited to this.

The liquid crystal display device of the present invention comprises a polarizing plate 60 (a polarizing plate having polarization scattering anisotropy) adjacent to the light reflection plate 64, the backlight 67, the light guide plate 65, and the light diffusion plate 66. Protective film 61Z Dichroic polarizing film using light absorption action by dichroic substance 62Z polarizing plate protective film B63)), liquid crystal display panel 68, viewing side polarizing plate 69 preferable.

[0231] As a specific example of the light guide plate, a linear light source such as a cathode tube or a light source such as a light emitting diode or EL is disposed on the side surface of a transparent resin plate, and the light guide plate is placed on the resin plate. For example, the light transmitted through the plate is emitted to one side of the plate by diffusion, reflection, diffraction, interference, or the like. When forming a laminated polarizing plate including a light guide plate, a prism sheet layer that controls the emission direction of light, a prism array layer with equal force, a light diffusing plate to obtain uniform light emission, and light emitted from a linear light source are used. Auxiliary means such as a light source holder for guiding to the side of the light guide plate If necessary, one layer or two or more layers can be arranged at predetermined positions such as the upper and lower surfaces and side surfaces to form an appropriate combination.

[0232] The backlight of the liquid crystal display device is preferably a direct backlight type. Specific examples of the direct backlight system include Japanese Patent Laid-Open Nos. 2001-215497 and 2001-3055.

The backlights described in JP-A-35, JP-A-2003-215585, JP-A-2004-29091, JP-A-2004-102119 and the like are effectively used.

[0233] In particular, the liquid crystal display device using the polarizing plate of the present invention is effective for a thin liquid crystal display device having a size of 15 inches or more and a large influence of heat in which the distance between the light source and the polarizing plate is shortened.

[0234] <Horizontal electric field switching mode type liquid crystal display device>

By incorporating the polarizing plate protective film B used in the present invention into a commercially available IPS (In Plane Switch) mode type liquid crystal display device, a liquid crystal display device of the present invention having excellent visibility and an increased viewing angle is produced. I can do it.

[0235] In the present invention, the transverse electric field switching mode includes a fringe field switching (FFS) mode, and the polarization plate of the present invention is incorporated in the same manner as the IPS mode. Thus, the liquid crystal display device of the present invention having the same effect can be manufactured. The polarizing plate protective film B used in the present invention is preferably installed between the driving liquid crystal cell and the lower polarizing element.

Example

[0236] Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

[0237] Example 1

<< Production of polarizing plate protective film having polarization scattering anisotropy >>

Table 1 shows the particles, plasticizer, and UV absorber used.

[0238] [Table 1] particle

[0239] 100 parts by mass of the following dope solution was thoroughly mixed with an in-line mixer (Toray's static in-tube mixer Hi-Mixer, SWJ), and then a stainless steel band support with a width of 2 m using a belt casting apparatus. Were uniformly cast. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel support was peeled off. Stretching during stretching to stretch so that the longitudinal (MD) stretch ratio is 1.2 times, and then grips both ends of the web with a tenter, and the stretch ratio in the width (TD) direction is 1. Stretched to 1x. The residual solvent at the start of stretching was 30%. After stretching, hold for several seconds while maintaining the width, release the width after releasing the tension in the width direction, and further transport for 30 minutes in the third drying zone set at 125 ° C for drying. A polarizing plate protective film 101 which is a polarizing plate protective film according to the present invention having a thickness of 40 μm and a winding length of 3000 m having a width of 1.5 m, a width of lcm at the end, and a height of 8 / xm is 40 μm. Produced.

300 parts by mass of methylene chloride

Ethanore 40 parts by mass Cellulose ester (cellulose acetate propionate; degree of substitution of acetyl group 1.9, degree of substitution of propiol group 0.7, degree of substitution of total acyl group 2.6) 100 parts by mass

Plasticizer (A) 5.5 parts by mass

Plasticizer (B) 5.5 parts by mass

UV absorber (A) 1.2 parts by mass

UV absorber (B) 0.8 parts by mass

Particle (A) 2 parts by mass

Next, except that the dope (cellulose ester resin, particle type) was changed as shown in Table 2, and the longitudinal (MD) stretch ratio was changed as shown in Table 2, the polarizing plate protective film 101 and Similarly, polarizing plate protective films 102 to 124 were produced. Further, a polarizing plate protective film 125 was prepared in accordance with the polarizing plate protective film 101 except that the ultraviolet curable resin described in the example of Japanese Patent No. 3090890 was used instead of the cellulose ester resin. did. The conditions during casting were appropriately changed so that the final film thickness was the same as that of the polarizing plate protective film 101.

[0241] The degree of acyl substitution of cellulose ester resin was measured according to the method prescribed in ASTM-D817-96.

[0242] The major axis diameter, minor axis diameter, and aspect ratio of the domains in the film were measured according to the following measurement methods.

[0243] <Measurement of domain major axis diameter, minor axis diameter, aspect ratio, and orientation angle>

Using a microtome, take a thin section of a few lOOnm thick around the surface of the produced film. Take a section with a transmission electron microscope at a magnification of 20,000 times and scan the image with a Canon CanoScan scanner. The image processing software WinROOF ver3 installed on Endeavor Pro 720L (CPU; Athlon—lGHz, memory: 512MB), which is a computer made by Epson Direct Co., Ltd. 60 (Mitani Corporation) Extract the domain image from the captured image, and check that there are more than 300 domains on the screen after extracting the domain image. If the extraction is not enough, manually adjust the detection level to obtain more than 300 domains. Adjustments were made to detect and extract the domain. Images extracted in this way For each domain in the image data, the major axis diameter and the minor axis diameter were measured, and the aspect ratio of the average number of domains was calculated. In addition, when the angle formed between the film forming direction of the polarizing plate protective film and the major axis direction of the domain is taken as the orientation angle, the average value of the absolute values of the orientation angles is obtained by using a transmission electron microscope. After positioning, this axis and each domain

Each angle with 300 was measured, and the total of these was obtained by averaging the numbers.

[Table 2]

[0245] <Preparation of polarizing plate protective film B>

(Preparation of polarizing plate protective film 201)

Fine particles (Aerosil R972V (Nippon Aerosil Co., Ltd.)) 11 parts by mass

89 parts by mass of ethanol

The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with a high-pressure disperser, Manton Gorin.

[0246] <Fine particle additive solution>

Cellulose ester A was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and then filtered using Azumi filter paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. While finely stirring the cellulose ester solution after filtration, the fine particle dispersion was slowly added thereto. Further, the dispersion was performed 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.

[0247] 99 parts by mass of methylene chloride

Cellulose ester A (cellulose acetate propionate; degree of substitution of acetyl group 1.6, degree of substitution of propiol group 0.8, degree of substitution of total acyl group 2.4) 4 parts by mass

Particulate dispersion 11 parts by mass

A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester was added to the pressurized dissolution tank containing the solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was filtered using Azumi filter paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. to prepare a main dope solution.

[0248] The main dope solution was mixed with 100 parts by mass and the fine particle additive solution was 5 parts by mass, mixed thoroughly with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ), and then belt-rolled. Using an apparatus, the film was uniformly cast on a stainless steel band support having a width of 2 m. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. Applying tension during peeling so that the longitudinal (MD) draw ratio is 1.1 times Next, the both ends of the web were gripped by a tenter and stretched so that the stretching ratio in the width (TD) direction was 1.3 times. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, and further transport for 30 minutes in the third drying zone set at 125 ° C for drying. A polarizing plate protective film 201 having a thickness of 40 m and a winding length of 3000 m, having a width of 1.5 m, a width of 1 cm at the end, and a height of knurling was prepared.

390 parts by mass of methylene chloride

80 parts by mass of ethanol

Cellulose ester (cellulose acetate propionate; substitution degree of acetyl group 1.6, substitution degree of propiol group 0.8, substitution degree of total acyl group 2.4) 100 parts by mass

Plasticizer (A) 5.5 parts by mass

Plasticizer (B) 5.5 parts by mass

UV absorber (A) 1.2 parts by mass

UV absorber (B) 0.8 parts by mass

(Preparation of polarizing plate protective film 202)

Into a glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer, 40 g of the monomer Xa and Xb mixed solution of the types and ratios listed in Table 4, 2 g of the mercaptopropionic acid chain transfer agent and 30 g of toluene. The temperature was raised to 90 ° C. Thereafter, from one dropping funnel, 60 g of the monomer Xa and Xb mixed solution of the types and ratios shown in Table 4 was dropped over 3 hours, and at the same time, the azobisisobuti-titol dissolved in 14 g of toluene from the other funnel 0 4 g was added dropwise over 3 hours. Thereafter, 0.6 g of azobis soft mouth-tolyl dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain Polymer X. The obtained polymer X was solid at room temperature. The weight average molecular weight of polymer X is shown in Table 4 by the following measurement method.

[0250] In Table 4, MMA and HEA are abbreviations for the following compounds, respectively.

[0251] MMA: Methyl methacrylate

HEA: 2-hydroxyethyl acrylate (Weight average molecular weight measurement)

The weight average molecular weight was measured using gel permeation chromatography.

[0252] The measurement conditions are as follows.

[0253] Solvent: Methylene chloride

Column temperature: 25 ° C

Sample concentration: 0.1% by mass

Detector: RI Model 504 (GL Science Co., Ltd.)

Pump: L6000 (manufactured by Hitachi, Ltd.)

Flow rate: 1. Om mm

[0254] <Synthesis of polymer candy>

Bulk polymerization was performed by the polymerization method described in JP-A-2000-128911. That is, the following methyl acrylate (MA) was introduced as a monomer Ya into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser, and nitrogen gas was introduced into the flask. The following thioglycerol substituted with was added with stirring. After the addition of thioglycerol, the temperature of the contents was appropriately changed and polymerization was carried out for 4 hours, the contents were returned to room temperature, and 20 parts by mass of a benzoquinone 5 mass% tetrahydrofuran solution was added thereto to stop the polymerization. The contents were transferred to an evaporator, and tetrahydrofuran, residual monomer and residual glycerol were removed under reduced pressure at 80 ° C. to obtain polymer Y shown in Table 4. The obtained polymer Y was liquid at room temperature. The weight average molecular weight of the polymer Y is shown in Table 4 by the above measurement method.

[0255] 100 parts by mass of methyl acrylate

Thioglycerol 5 parts by mass <Composition of dope 202>

(Silicon dioxide dispersion 1)

Aerosil 972V (Nippon Aerosil Co., Ltd.) 12 parts by mass

(Average primary particle diameter 16nm, apparent specific gravity 90gZ liter)

88 parts by mass of ethanol

The above was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide / silicon dioxide dispersion with stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare silicon dioxide dispersion / dilution liquid 1.

[0256] (Dope additive 1)

50 parts by mass of methylene chloride

Polymer X Table 4 Amount

Polymer Y Table 4 Amount

Silicon dioxide dispersion 1 10 parts by mass

UV absorber (A) 1.2 parts by mass

UV absorber (B) 0.8 parts by mass

In the above, methylene chloride, polymer X, and polymer Y were completely dissolved while stirring, and then a silicon dioxide-silica dispersion 1 was added and stirred to prepare a dope addition solution 1.

[0257] (Preparation of dope 202)

Cellulose ester (cellulose triacetate synthesized from linter cotton, acetyl substitution degree 2.92) 100 parts by weight

380 parts by mass of methylene chloride

30 parts by mass of ethanol

Dope additive solution 1 part by mass of the preparation

The above was put into an airtight container, heated, stirred and completely dissolved, and filtered using Azumi filter paper No. 24 manufactured by Azumi Filter Paper Co., to prepare Dope 202.

[0258] The above dope solution is filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd., and a belt casting apparatus is used. Yes, temperature 22. C, uniformly cast onto a stainless steel band support with a width of 2 m. On the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 105%, and the stainless steel band support was peeled off with a peel tension of 162 NZm. The peeled cellulose ester web was evaporated at 35 ° C, slit to 1.6 m width, and then dried at 135 ° C drying temperature while being stretched 1.1 times in the width direction with a tenter. . At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter, the lateral tension is released at 130 ° C to release the width retention, and then drying is completed while transporting the drying zone at 120 ° C and 130 ° C with many rolls. Slit at 5πιψ 、, apply a 10m wide and 7m wide knurling force to both ends of the film, scrape it off to a 6-inch inner diameter core with an initial tension of 220NZm and a final tension of lONZm. 202 Got. The rotational speed of the stainless steel band support and the operating speed of the tenter were calculated. The MD draw ratio in the MD direction was 1.1. The residual solvent amount of the polarizing plate protective film shown in Table 3 was 0.1%, the film thickness was 40 m, and the ridge length was 3000 m.

[0259] [Table 3]

[0260] [Table 4]

*,: Additive parts by mass per 100 parts by mass

[0261] << Production of Polarizing Plate >>

Polarizing plates 301 to 350 shown in Tables 5 and 6 were produced using the produced polarizing plate protective films 101 to 125 and polarizing plate protective films B201 and 202, respectively.

[0262] A polybulal alcohol film having a thickness of 120 m was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 6 times at 50 ° C to form a polarizing film. Al on both sides of this polarizing film The above polarizing plate protective films 101 to 125 and polarizing plate protective films B 201 and 202 that have been subjected to the caliken candy treatment are combined in Tables 5 and 6, respectively, using a completely saponified polybulal alcohol 5% aqueous solution as an adhesive. Pasted together.

[0263] <Alkali Kenyaku treatment>

Saponification process 2 mol ZL—NaOH 50 ° C 90 seconds

(If it is difficult to paste, 70 ° C 90 seconds)

Washing process Water 30 ° C 45 seconds

Neutralization process 10% by mass HC1 30 ° C 45 seconds

Washing process Water 30 ° C 45 seconds

The film sample was saponified, washed with water, neutralized and washed with water under the above conditions, and then dried at 80 ° C.

[0264] <Production of VA liquid crystal display device>

Sharp's 32-inch TV AQ—32AD5, which is a VA-type liquid crystal display device, is peeled off the previously-attached polarizing plate on the backlight side, and each of the above-prepared polarizing plates 301 to 325 is a liquid crystal cell (VA-type). The liquid crystal display device 301-325 was produced by bonding to the glass surface.

[0265] At that time, the polarizing plate protective film 201 as the polarizing plate protective film B is on the liquid crystal cell side, and the polarizing plate is bonded in the same direction as the polarizing plate bonded in advance. I went as follows.

[0266] IPS mode liquid crystal display device

Using the 23-inch Toshiba LCD TV FACE 23LC100, which is an IPS mode liquid crystal display device, the polarizing plate on the backlight side that had been bonded in advance was peeled off, and the polarizing plates 326 to 350 produced above were each It was bonded to the glass surface of the cell (IPS type) to prepare liquid crystal display devices 3 26 to 350.

[0267] At that time, the polarizing plate protective film 202 as the polarizing plate protective film B is on the liquid crystal cell side, and the polarizing plate is bonded in the same direction as the polarizing plate bonded in advance. I went as follows.

[0268] Using the liquid crystal display devices 301 to 350 produced as described above, the luminance was evaluated in the following manner.

[0269] <Evaluation of luminance of liquid crystal display device> The front luminance of each manufactured liquid crystal display device was evaluated.

[0270] For the luminance, the value measured with a spectral radiance meter CS-1000 (manufactured by Co-Force Minolta Sensing) was used as the luminance (cdZm ² ). The luminances of the liquid crystal display devices 315 and 340 using the polarizing plate protective film 115 disposed on the backlight side are set to 1, and the relative luminance in each liquid crystal display method is represented by the following criteria.

[0271] ◎: 1. Front brightness more than 2 times

0: 1. Front brightness of 1x or more and less than 1.2x

△: Front brightness of 1.05 times or more and less than 1 time

X: Less than 1.05 times

The results are shown in Tables 5 and 6 below.

[0272] [Table 5] Polarizing plate / liquid crystal BL side polarizing plate protection Polarizing plate protection

LCD drive method Brightness Remarks

Display No. Film rto. Film B No.

301 VA type 101 201 ○ The present invention

302 VA type 102 201 ○ The present invention

303 VA type 103 201 ○ The present invention

304 VA type 104 201 ○ The present invention

305 VA type 105 201 ○ The present invention

306 VA type 106 201 ○ The present invention

307 VA type 107 201 ○ The present invention

308 VA type 108 201 ◎ The present invention

309 薩 109 201 ◎ The present invention

3Π 111 201 Δ The present invention

312 VA type 112 201 △ The present invention

313 VA type 113 201 △ The present invention

314 VA type 114 201 △ The present invention

315 VA type 115 201 X Comparative example

316 VA type 116 201 X Comparative example

3W VA type 117 201 X Comparative example

318 VA type 118 201 X Comparative example

319 VA type 119 201 X Comparative example

320 120 20, X Comparative example

321 VA type 121 201 X Comparative example

322 VA type 122 201 X Comparative example

323 suke 123 201 X Comparative example

324 VA type t24 201 X Comparative example

325 VA type 125 201 X Comparative example [0273] [Table 6]

[0274] From the results of Tables 5 and 6, VA type liquid crystal display devices 301 to 314 and IPS type liquid crystal displays using the polarizing plate on which the polarizing plate protective film having polarization scattering anisotropy of the present invention was bonded. It can be seen that the devices 32 6 to 339 show an excellent brightness enhancement effect.

[0275] Example 2

In place of the polarizing elements used in the polarizing plates 301 to 314 and 326 to 339 of the present invention described in Example 1, a polarizing plate was prepared in the same manner except that the following ethylene-modified PVA film was used as the polarizing element. When the same evaluation as in Example 1 was performed, it was found that a polarizing plate with a high brightness enhancement effect could be produced.

<Polarizing element: Production of ethylene-modified PVA film> The ethylene unit content 2.5 mole ^_0/0, a degree of saponification of 99.95 mol ^_0/0, the E Ji Ren modified PVA100 parts by weight of the polymerization degree of 2400, also impregnated with glycerin 10 parts by mass and 170 parts by weight of water These were melt-kneaded, defoamed, melt-extruded into a metal roll from T Daika, and formed into a film. The ethylene-modified PVA film obtained after drying and heat treatment had a thickness force of 0 μm, and the average hot water cutting temperature of the film was 70 ° C.

[0277] The thus obtained ethylene-modified PVA film was successively treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying, and heat treatment to produce a polarizing film. That is, the ethylene-modified PVA film was pre-swelled by immersing in 30 ° C water for 60 seconds, and then in a 35 ° C aqueous solution having a boric acid concentration of 40 gZ liter, an iodine concentration of 0.4 gZ liter, and a potassium iodide concentration of 60 gZ liter. Soaked for 2 minutes. Subsequently, it was uniaxially stretched 6 times in a 55 ° C aqueous solution with a boric acid concentration of 4%, and a 30 ° C aqueous solution with a potassium iodide concentration of 60 gZ liters, boric acid concentration of 40 gZ liters, and salted zinc concentration of 10 gZ liters. Fixing was performed by immersing in for 5 minutes. Thereafter, the ethylene-modified PVA film was taken out, dried with hot air at 40 ° C. under a constant length, and further subjected to heat treatment at 100 ° C. for 5 minutes to obtain a polarizing film having a thickness of 15 m.

[0278] The transmittance of the obtained polarizing film was 44.34%, the degree of polarization was 99.46%, and the dichroic ratio determined by calculation was 49.13. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). Color spots with small brightness differences are small and good.

Claims

The scope of the claims

[1] A polarizing plate protective film having a polarization scattering anisotropy comprising an optical continuous phase comprising cellulose ester and a domain having an aspect ratio of ^ or more defined by the following formula (1): Acetyl group substitution degree X, propionyl group substitution degree Y and force of cellulose ester satisfying the conditions defined by the following formulas (2) and (3), and the film-forming direction of the polarizing plate protective film and the length of each domain A polarizing plate protective film, characterized in that the average value of the angle formed with the axial direction is within 25 °.

Formula (1)

Aspect ratio = major axis diameter Z minor axis diameter

Formula (2)

2. 3≤X + Y≤2.8

Formula (3)

0. 7≤Υ≤2.3

[2] The minimum value of the refractive index difference between the optical continuous phase and the domain is 0.25 or more, the major axis diameter of the domain is 400 nm or more, lOOOOnm or less, and the minor axis diameter is 50 nm or more. 2. The polarizing plate protective film according to claim 1, wherein the thickness is 390 nm or less.

[3] The polarizing plate protective film according to [1] or [2], wherein the domain is an inorganic compound that has been surface-treated with a surface modifier.

[4] A polarizing plate protective film according to any one of claims 1 to 3, which is a polarizing plate integrated in the order of a polarizing plate protective film Z dichroic polarizing film Z polarizing plate protective film B, A polarizing plate characterized in that the absorption axis of the dichroic polarizing film is in the longitudinal direction of the polarizing plate protective film.

[5] The polarizing plate according to claim 4 is used, and the polarizing film protective film force according to any one of claims 1 to 3 is disposed on the backlight side. Special A liquid crystal display device.