JP2003344660A - Retardation film and manufacturing method therefor, and circularly polarizing plate and liquid crystal display device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate retardation film whose optical anisotropy is large, whose moisture permeability is low by improving the moisture dependence of the optical anisotropy, whose surface contamination or foreign material by a retardation ascending agent or a plasticizer is decreased, and which has an excellent display quality. <P>SOLUTION: This is a retardation film of a cellulose acylate film which contains an aromatic compound that has at least two aromatic rings. The aromatic compound content concentration of the cellulose film is higher inside of the film than near the surface of the film, the retardation value of the cellulose acylate film at the wavelength of 450 nm is 100 to 125 nm, the retardation value at the wavelength of 590 nm (Re590) is 125 to 160 nm, and the moisture permeability degree of the cellulose acylate film is 2 to 150 g/m<SP>2</SP>24 h. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cellulose acylate retardation plate, and more particularly to a cellulose acylate retardation film formed by laminating a cellulose acylate solution by a laminated casting method. Regarding the board. Furthermore, the present invention relates to a polarizing plate and a liquid crystal display device using this retardation plate.

[0002]

2. Description of the Related Art Cellulose acylate film is used in various photographic materials and optical materials because of its toughness and flame retardancy. Cellulose acylate film is a typical photographic light-sensitive material support. The cellulose acylate film is also used in liquid crystal display devices. The cellulose acylate film is characterized by having a higher optical isotropy (lower retardation value) than other polymer films. Therefore, a cellulose acylate film has often been used so far in applications requiring optical isotropy, for example, as a protective film for a polarizing plate. On the contrary, the retardation plate (optical compensation film) of the liquid crystal display device is required to have optical anisotropy (high retardation value). Therefore, a synthetic polymer film having a high retardation value such as a polycarbonate film or a polysulfone film is often used as the retardation plate.

As described above, in the technical field of optical materials, when a polymer film is required to have optical anisotropy (high retardation value), a synthetic polymer film is used, and optical isotropy (low retardation) is used. When a standardization value) is required, it was general to use a cellulose acylate film. However, European Patent 09116
The 56A2 specification overturns conventional general principles,
A cellulose acylate film having a high retardation value that can be used in applications where optical anisotropy is required is disclosed, and the applications of the cellulose acylate film have expanded. In recent years, it has been strongly desired to reduce the weight and thickness of liquid crystal display devices, and to reduce the thickness of cellulose acylate film, which is an element used in liquid crystal display devices.
As a result, there has been a demand for a film having a retardation value similar to that of the conventional film although it is thin. On the other hand, cellulose acylate has a high moisture permeability and has a problem that the retardation changes depending on the temperature and humidity of the outside air.
It has been clarified that the polymer film disclosed in JP-A No. 2002-14230 has a high water vapor transmission rate, and the retardation changes when the temperature and humidity of the outside air change greatly. That is, a film having low moisture permeability has been desired. In addition, additives and plasticizers added to increase retardation are deposited during film production and contaminate the production process, and there is a problem of foreign matter defects on the film surface.

[0004]

Therefore, the present invention has a large optical anisotropy used as a protective film for a polarizing film of a polarizing plate used in a liquid crystal display device and improves the humidity dependency of the optical anisotropy. It is an object of the present invention to provide a cellulose acylate retardation film having a low water vapor transmission rate and further having excellent display quality in which surface contamination and foreign matters due to a retardation increasing agent, a plasticizer and the like are reduced. Another object is to provide a circularly polarizing plate and a liquid crystal display device using this retardation plate.

[0005]

As a result of earnest research by the present inventor, the object of the present invention is to provide a cellulose acylate retardation film of the following (1) and (3) to (5) and a cellulose acylate of the following (2). Method for manufacturing rate retardation plate, circularly polarizing plate of (6) below,
This is achieved by the liquid crystal display device of the following (7) and further the image display device of the following (8). (1) In a retardation plate of a cellulose acylate film containing an aromatic compound having at least two aromatic rings, (a) the concentration of the aromatic compound in the cellulose film is higher in the inside of the film than in the vicinity of the film surface. And (b) the retardation value of the cellulose acylate film at a wavelength of 450 nm is 100 to 125 n.
m, and the retardation value (R
e590) is 125 to 160 nm, and (c) the water vapor transmission rate of the cellulose acylate film is 2 to 150 g / m.
A retardation plate having a length of ² · 24 h.

(2) In the method for producing a retardation plate of a cellulose acylate film, the cellulose acylate solution containing an aromatic compound having at least two aromatic rings is formed into a film by a casting method, and then stretched. a) The casting method is a laminated casting method, and the content of the aromatic compound in the cellulose acylate solution is 1 to 30 parts by mass for at least one inner layer solution with respect to 100 parts by mass of cellulose acylate. And the outermost layer solution is 0.01 to
10 parts by mass, and the content of the aromatic compound per 100 parts by mass of the cellulose acylate in the outermost layer solution is lower than that of at least one inner layer solution, and (b) the wavelength of the cellulose acylate film is 450 nm. Retardation value is 100 to 125 nm and wavelength 59
The retardation value at 0 nm is 125 to 160 nm, and (c) the water vapor transmission rate of the cellulose acylate film is ² to 150 g / m ² · 24 h.

(3) A cellulose acylate retardation plate obtained by forming a film of a cellulose acylate solution containing an aromatic compound having at least two aromatic rings by a casting method, and then stretching the film. ) The casting method is a laminated casting method, and the content of the aromatic compound in the cellulose acylate solution is 100% by weight.
1 to at least one inner layer solution with respect to parts by mass
30 parts by mass, 0.01 to 10 parts by mass in the outermost layer solution, and the content of the aromatic compound in the outermost layer solution per 100 parts by mass of cellulose acylate is lower than that of at least one inner layer solution. (B) the cellulose acylate film has a retardation value at a wavelength of 450 nm of 100 to 125 nm and a retardation value at a wavelength of 590 nm of 125 to 160 nm,
(C) The moisture permeability of the cellulose acylate film is 2 to
A retardation plate having a weight of 150 g / m ² · 24 h.

(4) The cellulose acylate retardation film as described in (1) or (3) above, wherein the film thickness of the cellulose acylate film is 10 to 100 μm. (5) The cellulose acylate retardation plate according to the above (1), (3) or (4), wherein the surface of the cellulose acylate film is saponified with an alkaline solution. (6) A circularly polarizing plate comprising a polarizing film and two transparent protective films arranged on both sides thereof, wherein at least one of the transparent protective films is one of the above (1) and (3) to (5). A circularly polarizing plate, which is the retardation plate described. (7) A liquid crystal display device using the retardation plate according to any one of (1) and (3) to (5) or the circularly polarizing plate according to (6). (8) An image display device using the retardation plate according to any one of (1) and (3) to (5) or the circularly polarizing plate according to (6).

That is, the present inventor can increase retardation of a retardation plate used in a liquid crystal display device by stretching with the cellulose acylate of the present invention, and further, the humidity dependence of the retardation is small and the retardation is small. It has been clarified that surface contamination and foreign matters due to a cation raising agent and a plasticizer can be reduced. As a result, we succeeded in producing a cellulose acylate retardation plate having excellent display quality. Moreover, an excellent circularly polarizing plate can be obtained by using the retardation film of the present invention as at least one protective film of a conventional polarizing plate having transparent protective films provided on both sides of a polarizing film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The cellulose acylate film, which is the retardation plate of the present invention, has a higher content concentration of the aromatic compound having at least two aromatic rings, which mainly functions as a retardation increasing agent, inside the film than in the vicinity of the film surface, By setting the concentration of the plasticizer to be low near the film surface, while suppressing the precipitation of the plasticizer and retardation increasing agent on the film surface, the retardation increasing agent inside the film is increased and the hydrophobicity is increased. Therefore, the water vapor permeability is reduced.
In the present invention, "near the film surface" means a part from the outermost surface of the film to a depth of about 25% of the film thickness, and "inside the film" means an inner part of the film excluding the vicinity of the film surface. The cellulose acylate film of the present invention is preferably produced by laterally stretching after being formed into a film by the below-mentioned laminated casting method. However, when forming a film by the laminated casting method, "the vicinity of the film surface" means the most. It corresponds to the outer layer.

[0011] The moisture permeability of the cellulose acylate film of [Moisture Permeability] The present invention is a 2~150g / m ² · 24h, preferably even at ^{10~120g / m 2 · 24h, 20~100g} / more preferably m ² · 24h, and particularly preferably 20~100g / m ² · 24h. When it exceeds 150 g / m ² · 24 h, water rapidly enters and leaves from the cellulose acylate film due to a rapid change in the temperature and humidity of the outside air, and the retardation value, which is an important property as a retardation plate, changes.
Further, when the retardation plate is incorporated in a liquid crystal display device, it causes a change in tint and a decrease in viewing angle. Also, 2 g / m ²
-If it is less than 24 hours, when it is attached to both surfaces of the polarizing film, the cellulose acetate film hinders the drying of the adhesive, resulting in poor adhesion. The method of measuring water vapor permeability is
Apply the method described in "Physical Properties of Polymers II" (Polymer Experiment Course 4 Kyoritsu Shuppan), pages 285 to 294: Measurement of vapor permeation amount (mass method, thermometer method, vapor pressure method, adsorption amount method). Can be done. The definition of water vapor transmission rate of the present invention is defined by JIS standard JIS.
Z0208, B condition (temperature 40 ℃, humidity 90% R
According to H), the measurement was performed under these conditions. Further, the value of water vapor permeability of the present invention is expressed as a value converted when the film thickness is 60 μm. The method of controlling the water vapor transmission rate is not particularly limited, but the water vapor transmission rate can be controlled by producing a film by a laminated casting (co-casting) method and stretching as in the present invention. Further, a barrier layer may be used in combination for controlling (lowering) the moisture permeability.

[Optical Anisotropy of Retardation Plate (λ / 4 Plate)] The cellulose acylate film of the invention has the following optical anisotropic properties as a retardation plate. That is, the retardation value (Re450) measured at a wavelength of 450 nm is 100 to 1
The retardation value is 25 nm and the retardation value (Re590) measured at a wavelength of 590 nm is 125 to 160 nm. More preferably, Re450 is 108 to 120 nm and Re590 is 130 to 152 nm. The retardation plate of the present invention having the above-mentioned optical anisotropic properties is particularly suitable for a λ / 4 plate.

Each retardation value (Re) is calculated according to the following formula (1). Formula (1) Re = (nx−ny) × d In the formula, nx is the refractive index in the slow axis direction in the retardation plate surface (maximum refractive index in the surface); ny is the retardation plate surface Is the refractive index in the direction perpendicular to the slow axis inside; and d is the thickness (nm) of the retardation plate.

Further, when the retardation plate of the present invention is used as a λ / 4 plate, from the viewpoint of improving the viewing angle characteristics,
The Nz factor defined by the following formula is preferably in the following range. Formula (nx-nz) / (nx-ny) [In formula, nx is a refractive index of the slow axis direction in the surface of the retardation plate; ny is perpendicular to the slow axis in the surface of the retardation plate. Is the refractive index in the direction; nz is the refractive index in the thickness direction of the retardation plate. ] The preferable range of Nz factor is 1.2 to 3.0, the more preferable range is 1.5 to 2.5, and the particularly preferable range is 1.55 to 2.0.

The desired retardation value can be obtained by producing a film by the below-mentioned lamination casting method and stretching treatment, or by adding a retardation increasing agent. It is also possible to use the method such as coating on a film together. The retardation value can be measured with a commercially available ellipsometer, but since the measured value varies depending on temperature, humidity and the like, it is generally preferable to measure under conditions such as 25 ° C./60% RH.

[Cellulose Acylate Film] Regarding the solution of cellulose acylate film, various additives, manufacturing process, casting, drying, stretching process, surface treatment manufacturing process, etc., the Institute of Invention and Innovation published technique (Publication 2001-1745, 20)
Inventive Society), published March 15, 2001), and the present invention can use these methods.

The cellulose acylate of the present invention is a fatty acid ester of cellulose, and a lower fatty acid ester is particularly preferable. Lower fatty acid has 6 carbon atoms
The following fatty acids are meant. 2 for the number of carbon atoms
It is preferably (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is preferable as the cellulose acylate, and examples thereof include diacetyl cellulose and triacetyl cellulose. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Generally, 2,3 of cellulose acetate
The 6-hydroxyl group is not evenly distributed in 1/3 of the entire substitution degree, and the 6-hydroxyl group substitution degree tends to be small. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose acetate is higher than those of the 2- and 3-position hydroxyl groups.
30% or more and 40% or more of 6-position hydroxyl group with respect to the entire substitution degree
It is preferably substituted with an acyl group below, more preferably 31% or more, and particularly preferably 32% or more. Further, the substitution degree of the 6-position acyl group of cellulose acetate is preferably 0.88 or more. The 6-position hydroxyl group is a propionyl group, a butyroyl group, a valeroyl group, a benzoyl group, which is an acyl group having 3 or more carbon atoms, in addition to the acetyl group.
It may be substituted with an acryloyl group or the like. The substitution degree at each position can be measured by NMR.

As the cellulose acetate, it is preferable to use cellulose acetate having an acetylation degree of 59.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. Acetification degree is ASTM:
D-817-91 (Testing method for cellulose acetate, etc.)
According to the measurement and calculation of the degree of acetylation in. Also,
The viscosity average degree of polymerization (DP) of cellulose acylate is 2
It is preferably 50 or more, more preferably 290 or more. Cellulose acylate has Mw / M measured by gel permeation chromatography.
It is preferable that the molecular weight distribution of n (Mw is a mass average molecular weight and Mn is a number average molecular weight) is narrow. The specific value of Mw / Mn is preferably 1.0 to 1.8,
It is more preferably 1.0 to 1.7, and 1.0 to
Most preferably 1.6. The thickness of the cellulose acetate retardation plate of the present invention is preferably in the range of 10 to 100 μm, more preferably in the range of 20 to 80 μm, and most preferably in the range of 25 to 70 μm.

[Aromatic compound having at least two aromatic rings] An aromatic compound having at least two aromatic rings contained in the cellulose acylate film of the present invention (hereinafter, also referred to as "aromatic compound of the present invention"). ) Is contained in the cellulose acylate film as a retardation increasing agent in order to adjust the retardation of the cellulose acylate film. Also, two or more kinds of aromatic compounds may be used in combination. The aromatic ring of the aromatic compound may be an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples of the aromatic compound of the present invention include triazines substituted with a plurality of aryl groups or arylamino groups (triphenyl-1,3,5-triazine,
Tri-m-tolyl-1,3,5-triazine, triphenylamino-1,3,5-triazine, tri-m-tolylamino-1,3,5-triazine, etc.), trans-1,4-cyclohexanedicarboxylic acid Examples thereof include acid diesters (pn-hexylphenol diester, pn-amylphenol diester, etc.). Other specific examples include Japanese Patent Laid-Open No. 2000-111914,
2000-275434, WO / 01/885.
No. 74, Japanese Patent Application No. 2002-70009, and the like. The aromatic compound of the present invention has a molecular weight of 30.
It is preferably from 0 to 800. The content of the aromatic compound of the present invention is preferably 0.01 to 30 parts by mass, and more preferably 0.1 to 25 parts by mass with respect to 100 parts by mass of cellulose acetate. More preferable.

In the present invention, when the cellulose acylate film is produced by the laminated casting method, the concentration of the aromatic compound of the present invention in the outermost layer dope and the inner layer dope is adjusted to be different. As a result, the concentration of the aromatic compound of the present invention can be made different between the inside and the vicinity of the surface of the film. The amount of the aromatic compound of the present invention added to each layer dope is 100 parts by weight of cellulose acylate and is 1 in at least one inner layer.
To 30 parts by mass, more preferably 3 to 25 parts by mass, and particularly preferably 5 to 20 parts by mass. Further, the addition amount of the outermost layer is lower than that of at least one inner layer, and is 0.01 to 10 parts by mass, and further 0.
It is more preferably 1 to 8 parts by mass, and particularly preferably 0.3 to 5 parts by mass. In any case, the concentration in the outermost layer dope is at least 1 in the present invention.
It should be lower than the concentration of the two inner layers. This makes it possible to prevent the aromatic compound of the present invention from depositing on the film surface and prevent foreign matter defects from occurring.

[Cellulose Acylate Plasticizer] As the additives to be added to the cellulose acylate film of the invention, those described in JIII Journal of Technical Disclosure No. 2001-1745, their usage and the like can be used. In the present invention, when the cellulose acylate film is produced by the layered casting method described later, the amount of the plasticizer added is 5 to 30 parts by mass in the inner layer with respect to 100 parts by mass of the cellulose acylate. It is preferably 10 to 28 parts by mass, more preferably 15 to 25 parts by mass. The addition amount of the outermost layer is preferably lower than that of the inner layer, and is preferably 2 to 15 parts by mass, more preferably 3 to 10 parts by mass. The addition amount of the outermost layer is 15
If it exceeds the mass part, precipitation may occur depending on the plasticizer, and the possibility of becoming a foreign matter defect increases.

[Layered Casting Method] The cellulose acylate film of the present invention is preferably formed by a solvent film forming method (solvent casting). In the present invention, the dope solution in which cellulose acylate is dissolved in an organic solvent can be formed by laminating and casting on a smooth band or a drum. In order to laminate and cast a plurality of dope solutions of three layers or more, a dope solution is cast from a plurality of casting holes provided at intervals in the traveling direction of the support to form a film while laminating the dope solutions. It may be, for example, JP-A-61-15
8414, JP-A-1-122419, JP-A-11-
The method described in 198285 can be used. The dope solution may be cast from three or more casting ports to form a film.
-27562, JP-A-61-94724, JP-A-6-
1-946245, JP-A 61-104813, JP-A 61-158413, and JP-A 6-1349.
The method described in No. 33 can be used.

Alternatively, by using three casting ports, the film formed on the support by the first casting port is peeled off, and the second and third castings are performed on the side in contact with the surface of the support. A film may be produced according to, for example, Japanese Patent Publication No.
The method described in No. 0235 can be used. When producing the cellulose film of the present invention, in the dope solution to be cast, the additive amount (retardation increasing agent amount, plasticizer amount, etc.) of the outermost layer is made lower than that inside as described above. be able to. In the present invention, the cellulose acylate film is preferably composed of three or more and 10 or less laminated casting layers. Further, the cellulose acylate solution of the present invention can be simultaneously cast with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

[Stretching Treatment] In the production of the cellulose acylate film of the present invention, the stretching treatment includes stretching in the casting direction at the time of laminate casting, drying and winding, and also in the casting direction (longitudinal stretching). ) Or by stretching (transverse stretching) perpendicularly to the casting direction. Stretching is preferably performed in the range of 10% to 90% of breaking elongation, and 20% to
It is more preferably performed at 85%, particularly preferably at 30% to 80%. If it exceeds 90%, the haze will increase due to cracks that occur before breaking, and if it is less than 10%, there is no effect. The orientation of the cellulose acetate molecules in the film plane advances, and the retardation Re value can be increased. Specifically, the draw ratio is 3 to 100%
Is preferred.

[Slow-Phase Angle of Cellulose Acylate Retardation Plate] The in-plane slow-axis angle of the cellulose acylate film, which is the retardation film of the present invention, is defined by the film stretching direction as a reference line (0 °). And is defined by the angle between the slow axis and the reference line. Here, when a roll-shaped film is stretched in the width direction, the width direction is used as a reference line, and when stretched in the longitudinal direction, the length direction is used as a reference line. The average value of the slow axis angle is 3
It is preferably at most 0 °, more preferably at most 2 °, most preferably at most 1 °. The direction of the average value of the slow axis angle is defined as the average direction of the slow axis. Further, the standard deviation of the slow axis angle is preferably 1.5 ° or less, more preferably 0.8 ° or less, and most preferably 0.4 ° or less.

[Surface Treatment of Film] When the cellulose acylate retardation film of the present invention is used as a transparent protective film of a polarizing plate, it is preferable that the cellulose acylate film of the present invention is surface-treated in advance. As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment is carried out. It is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment of the cellulose acylate film. The alkali saponification treatment is preferably carried out in a cycle of immersing the film surface in an alkali solution, neutralizing the film with an acid solution, washing with water and drying. Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution. The specified concentration of hydroxide ion is 0.
It is preferably in the range of 1 to 3.0 N, and more preferably in the range of 0.5 to 2.0 N. The alkaline solution may contain, in addition to water, lower alcohol (eg, ethanol, isopropyl alcohol), lower glycol (eg, ethylene glycol, propylene glycol) and the like. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, and more preferably in the range of 40 to 70 ° C.

[Polarizing Film] As the polarizing film used in the circularly polarizing plate of the present invention, an iodine type polarizing film, a dye type polarizing film using a dichroic dye, a polyene type polarizing film, or the like can be used.
The iodine type polarizing film and the dye type polarizing film are generally manufactured using a polyvinyl alcohol type film.

As the polarizing film, a polarizing film of any manufacturing method can be applied. For example, when a polyvinyl alcohol-based film is continuously supplied and the both ends of the film are stretched by applying a tension while being held by the holding means, one end of the film from the substantial holding start point to the substantial holding release point of the holding means The locus L1 and the locus L2 of the holding means from the substantial holding start point at the other end to the substantial holding release point have the relationship of the following formula (2) with respect to the distance W between the left and right substantial holding release points, and The straight line connecting the substantial holding start points is substantially orthogonal to the center line of the film introduced into the holding process, and the straight line connecting the left and right substantial holding release points is substantially perpendicular to the center line of the film sent to the next process. It may be stretched in this manner (US Patent Publication No. 2002-8840A).
See 1. ) Formula (2) | L2-L1 |> 0.4W Since the polarizing film has characteristics such as low mechanical strength and hygroscopicity, it can be protected by a film having protective ability to obtain a polarizing plate. it can. As the protective film for the polarizing film, an optically transparent film having a small birefringence is usually preferable, and cellulose triacetate or the like is used. In the case of the circularly polarizing plate of the present invention, the invention having optical anisotropy is used. The cellulose acylate retardation film is used as a film which also serves as a protective film.

[Circular Polarizing Plate] The retardation plate of the present invention described above is used as a λ / 4 plate, and the angle between the in-plane slow axis of the λ / 4 plate and the polarization axis of the polarizing film is substantially 45 °. A circularly polarizing plate can be obtained by laminating the layers so that Substantially 45 ° means 40 to 50 °. In terms of the performance of the circularly polarizing plate, the angle between the in-plane slow axis of the λ / 4 plate and the polarization axis of the polarizing film is preferably 41 to 49 °, and 42 to 48.
More preferably, it is more preferably 43 to 47 °, and most preferably 44 to 46 °. A transparent protective film is preferably provided on the surface of the polarizing film opposite to the surface on which the λ / 4 plate is provided. A hard coat layer is preferably provided on the transparent protective film. An antireflection layer or a functional thin film layer can be provided on the outermost layer.

The above retardation plate and the circularly polarizing plate using the above retardation plate as a protective film are HAN (hybrid a
ligned nematic) type, TN (twisted nematic) type, ST
N (supper twisted nematic) type, OCB (optically co
mpensatory bend) type, VA (vertical aligned) type, IP
S (in-plane switching) type, ECB (electrically cont)
rolled birefringence type, FLC (ferroelectric liqu)
id crystal) type, HPOLC (holographic polymer dis)
It can be used for liquid crystal display devices of modes such as a persed liquid crystal) type and a GH (guest-host) type.

[Reflective Liquid Crystal Display Element] The reflective liquid crystal display element used in the present invention comprises a lower substrate (1), a reflective electrode (2), a lower alignment film (3), a liquid crystal layer (4) and an upper alignment film. (5), transparent electrode (6), upper substrate (7), λ / 4 plate (8), and linear polarizing film (9) in this order. The lower substrate (1) and the reflective electrode (2) form a reflective plate. The lower alignment film (3) to the upper alignment film (5) form a liquid crystal cell. λ
The / 4 plate (8) can be arranged at any position between the reflection plate and the linearly polarizing film (9). In the case of color display, a color filter layer is further provided. The color filter layer is preferably provided between the reflective electrode (2) and the lower alignment film (3) or between the upper alignment film (5) and the transparent electrode (6). A transparent electrode may be used instead of the reflective electrode (2), and a reflective plate may be separately attached. A metal plate is preferable as the reflector used in combination with the transparent electrode. If the surface of the reflector is smooth, only the specular reflection component may be reflected and the viewing angle may be narrowed. Therefore, it is preferable to introduce an uneven structure (described in Japanese Patent No. 2756206) on the surface of the reflection plate. When the surface of the reflection plate is flat (instead of introducing an uneven structure on the surface), a light diffusion film may be attached to one side (cell side or outside) of the polarizing film.

The liquid crystal cell is a TN (twisted nematic)
Type, STN (Supper Twisted Nematic) type or HAN
A (Hybrid Aligned Nematic) type is preferable.
The twist angle of the TN type liquid crystal cell is preferably 40 to 100 °, more preferably 50 to 90 °, and most preferably 60 to 80 °. The value (Δn × d) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is 0.1 to 550 nm.
It is preferably 0.5 μm, and 0.2 to 0.4 μm
Is more preferable. The twist angle of the STN type liquid crystal cell is preferably 180 to 360 °, and 2
It is more preferably 20 to 270 °. The product of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer (Δ
The value of n × d) is 0.3 to 1.
The thickness is preferably 2 μm, more preferably 0.5 to 1.0 μm. In the HAN type liquid crystal cell, it is preferable that the liquid crystal is substantially vertically aligned on one substrate and the pretilt angle on the other substrate is 0 to 45 °. The value (Δn × d) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 1.0 μm at a wavelength of 550 nm, and 0 .3
More preferably, it is about 0.8 μm. The substrate on the side of vertically aligning the liquid crystal may be the substrate on the reflection plate side or the substrate on the transparent electrode side.

The reflective liquid crystal display device is used in a normally white mode in which bright display is performed when the applied voltage is low and dark display when the applied voltage is high, and in a normally black mode in which dark display is applied when the applied voltage is low and bright display is applied when the applied voltage is high. be able to. Normally white mode is preferred. As typical examples of the reflective liquid crystal display device and the guest-host reflective liquid crystal display element, Japanese Patent Application Laid-Open No. 2002-71948,
No. 2001-100205 and No. 2002-229.
Reference can be made to Japanese Patent No. 41, etc.

[0034]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. [Example 1] (Preparation of Cellulose Acylate Phase Difference Plate) (Preparation of Cellulose Acetate Solution) A cellulose acylate stock solution (dope stock solution) having the composition shown in Table 1 was prepared. For the dissolution, the raw materials were put into a mixing tank and stirred while heating to dissolve each component.

[0035]

[Table 1]

(Preparation of Retardation Raising Agent Solution) As shown in Table 2, the composition was put into another mixing tank and stirred while heating to prepare a retardation raising agent solution. Retardation increasing agent (Sumisolve T
M165F) is shown below.

[0037]

[Table 2]

[0038]

[Chemical 1]

(Preparation of Cellulose Acetate Dope Solution for Inner Layer and Outer Layer) As shown in Tables 3 and 4, the composition was put into a mixing tank, stirred and dissolved to prepare a cellulose acetate dope solution for inner layer and outer layer. The addition amount of the retardation increasing agent to 100 parts by mass of cellulose acetate is shown in Tables 3 and 4. 50 of the obtained dope
Degree, absolute filtration accuracy 0.01 mm filter (Toyo Roshi Kaisha, Ltd., # 63) and absolute filtration accuracy 0.002
It was filtered with a 5 mm filter (PH, FH025).

[0040]

[Table 3]

[0041]

[Table 4]

Using a three-layer co-casting die with the filtered dope,
The inner layer dope was placed on the inner side and the outer layer dope was placed on both outer sides, and multilayer casting was performed using a band casting machine. The dope was gelled, dried at 70 ° C. for 3 minutes and at 120 ° C. for 5 minutes, and then the film was peeled from the band and dried at 130 ° C. for 50 seconds to produce a cellulose acetate film.
The dope discharge amount was adjusted so that the inner layer thickness and both outer layer thicknesses shown in Table 5 were obtained. The obtained film was longitudinally uniaxially stretched by a roll stretching machine. The stretching ratio is as shown in Table 5, and the casing temperature in the stretching zone was 130 ° C. to prepare a cellulose acetate retardation plate.

[0043]

[Table 5]

(Measurement of Optical Properties of Cellulose Acetate Retardation Plate) About the prepared cellulose acetate retardation plate, an ellipsometer (M-150, JASCO Corporation)
Was used to measure the retardation Re values at wavelengths of 450 nm and 590 nm. In addition, from the refractive index measurement with an Abbe refractometer and the angle dependence of the retardation, the refractive index nx in the in-plane slow axis direction at a wavelength of 550 nm and the refractive index in the direction perpendicular to the in-plane slow axis. ny and the refractive index nz in the thickness direction are obtained, and the Nz factor (n
The value of (x-nz) / (nx-ny) was calculated. The results are shown in Table 6.

(Measurement of moisture permeability) JIS standard JISZ02
The measurement was performed under the conditions of 08 and B (temperature 40 ° C., humidity 90% RH). The results are shown in Table 6.

(Measurement of Haze) Haze is measured by a haze meter (10
It was measured using a 01DP type, manufactured by Nippon Denshoku Industries Co., Ltd. Five points were measured for each sample, and the average value was adopted. The results are shown in Table 6.

(Evaluation of surface condition) The film is visually observed,
The surface condition was evaluated as follows. The results are shown in Table 6. A: There is no contamination on the film surface, which is extremely good. B: Almost no contamination is observed on the film surface, and there is a slight amount of foreign matter, which is good. C: Contamination is partially recognized on the film surface. Not suitable as a film. D: Contamination is recognized almost all over the film surface. Not suitable as a film. E: Contamination is recognized on the entire surface of the film, and many foreign matters are seen. Not suitable as a film.

[0048]

[Table 6]

The cellulose acylate retardation film of the present invention is a film obtained by forming a cellulose acylate film containing a compound having at least two aromatic rings by a laminated casting method and then stretching the cellulose acylate film. There, Re450 is 100 ~ 125nm, R
e590 is 125 to 160 nm and the water vapor transmission rate is 2-1.
It is 50 g / m ² · 24 h, and it can be seen that this is a cellulose acylate retardation plate having excellent transparency and excellent surface condition without contamination.

Example 2 (Saponification Treatment of Cellulose Triacetate Film) On the cellulose triacetate film produced in Example 1 and shown in Table 7, a 1.0 N potassium hydroxide solution (solvent: IPA / propylene) was used. Glycol / water = 75/13 /
12 wt%) is applied with # 6 bar and heated at 60 ° C. for 10 seconds, then water is applied with # 1.6 bar on the wet application surface, and immediately 500 cc / m ² of washing water at 40 ° C. The film was sprayed from a nozzle and the washing water on the film surface was blown off with an air knife three times in succession, followed by drying with hot air at 100 ° C. to prepare a cellulose triacetate film having a saponified surface. Table 7 shows the results of measurement of various characteristics. The cellulose acylate retardation plate of the present invention is a cellulose acylate retardation plate saponified with an alkaline solution, has the same Re and moisture permeability as before treatment, and has the same excellent transparency as in Example 1. It was found to have an excellent surface condition with no property and no contamination. It was also confirmed that this film has excellent adhesion to the polarizing film.

[0051]

[Table 7]

Example 3 (Preparation of Polarizing Film) PVA film was added with iodine 2.0 g /
L, potassium iodide 4.0 g / L aqueous solution at 250C for 240 seconds, and then boric acid 10 g / L aqueous solution.
After dipping at 5 ° C. for 60 seconds, it was introduced into a tenter stretching machine, and
The film was stretched 3 times and the tenter was bent in the stretching direction. Thereafter, the width was kept constant and the film was dried in an atmosphere of 80 ° C. while contracting, and then separated from the tenter and wound up. The water content of the PVA film before the start of stretching was 31%, and the water content after drying was 1.5%. The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the film introduced and the center line of the film sent to the next step was 46 °. Wrinkles and film deformation at the tenter exit were not observed. The transmission axis direction of the obtained polarizing film was inclined by 45 ° with respect to the transport direction (longitudinal direction) of the tenter. The transmittance at 550 nm of this polarizing film was 43.7% and the polarization degree was 99.97%. there were.

(Preparation of Circular Polarizing Plate) A low refractive index layer coating solution having the following formulation was stirred, adjusted, filtered through a polypropylene filter having a pore size of 1 μm, and then Fujitac (TD80U, trade name: Fuji Photo Film Co., Ltd.) It was coated on the above with a bar coater, dried at 80 ° C. for 5 minutes, and then heated at 120 ° C. for 10 minutes to crosslink the polymer to form a low-refractive index layer having a thickness of 0.1 μm, and an antireflection film was produced.

[0054] -Refractive index layer coating liquid formulation- Thermally crosslinkable fluoropolymer 210 parts by mass (JN-7228, solid content concentration 6%, manufactured by JSR Corporation) Silica sol (MEK-ST) 18 parts by mass (Average particle size 10 to 20 nm, solid content concentration 30 wt%, manufactured by Nissan Chemical Co., Ltd.)   MEK 200 parts by mass

This antireflection film and each retardation film prepared were dipped in a 1.5N NaOH aqueous solution at 55 ° C. for 1 minute to saponify both surfaces, thoroughly washed with dilute sulfuric acid and water, dried and then dried on each cellulose triacetate side. Then, a polyvinyl alcohol-based adhesive material was applied to a thickness of about 30 μm, adhered on both sides of the polarizing film, and further dried at 80 ° C. to form a circularly polarizing plate. It was found that the circularly polarizing plates obtained from the retardation plate of the present invention were all substantially circularly polarizing plates.

Example 4 (Production of Reflective Liquid Crystal Display Element) A glass substrate provided with an ITO transparent electrode and a glass substrate provided with an aluminum reflective electrode having fine irregularities were prepared. A polyimide alignment film (SE-7) is provided on each of the electrode sides of the two glass substrates.
992, manufactured by Nissan Kagaku Co., Ltd.) was formed and subjected to rubbing treatment. The two substrates were stacked with the alignment films facing each other through a spacer of 2.5 μm. The orientation of the substrate was adjusted so that the rubbing directions of the two alignment films intersect at an angle of 117 °. Liquid crystal (MLC-62
52, manufactured by Merck & Co., Inc.) was injected to form a liquid crystal layer. Thus, a TN type liquid crystal cell having a twist angle of 63 ° and a value of Δn × d of 198 nm for a wavelength of 550 nm was produced. The λ / 4 plate prepared in Example 1 was attached to the side of the glass substrate provided with the ITO transparent electrode via an adhesive.
Further, a polarizing plate (a polarizing plate in which a protective film whose surface is AR (antireflection) -treated and a polarizing film are laminated) is attached thereon. A rectangular wave voltage of 1 kHz was applied to the produced reflective liquid crystal display device. When visually evaluated with a white display of 2 V and a black display of 6 V, it was confirmed that there was no tint in both white display and black display, and that neutral gray was displayed. Next, the measuring machine (EZ-Contrast 160
D, manufactured by ELDIM) was used to measure the front contrast ratio. Further, the viewing angle (angle range where the contrast ratio is 10 or more) in the left-right direction (direction orthogonal to the rubbing direction of the cell) was examined. The results are shown in Table 8. The liquid crystal display device of the present invention has excellent front contrast and a wide viewing angle.

[0057]

[Table 8]

[0058]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a retardation plate having a surface property in which the humidity dependence of retardation is small and the surface contamination and the foreign matter due to the retardation increasing agent and the plasticizer are reduced. Further, by using the retardation plate of the present invention, it is possible to provide an excellent circularly polarizing plate and a liquid crystal display device having excellent display quality.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a configuration of a reflective liquid crystal display element used in the present invention.

[Explanation of symbols]

1 Lower substrate 2 Reflective electrode 3 Lower alignment layer 4 Liquid crystal layer 5 Upper alignment layer 6 transparent electrodes 7 Upper substrate 8 λ / 4 plate 9 Linear polarization film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 1/12 C08L 1/12 4J002 G02F 1/13363 G02F 1/13363 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 9:00 9:00 11:00 11:00 F-term (reference) 2H049 BA02 BA06 BA42 BB03 BB49 BC03 BC22 2H091 FA11 FB02 FC08 FC25 FC29 FC30 FD10 FD12 FD14 GA16 KA02 LA03 LA11 LA12 LA18 4F071 AA09 AA81 AC10 AC11 AC12 AE22 AF08Y AF29 AF31 AF35Y AG28 AH16 AH19 BA02 BB02 BC01 BC12 BC17 4F205 AA01K AB19A AG01 AG03 AH73 GA07 GB02 GC02 GC07 GE03 GE21 GF03 QF16 A01 Q18G01 Q01G01G02G01 Q01G02G01Q02G01Q02G01G02G01G02G01G02G01G02G01G02G01G01G02G01G01G02G01G01G02G01G02G01G02G01G02G01G01G01G02G01G02G01G02G01G02G01G02G01G01G02G01G01G02G01G01G02G01G01G01G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G02G01G01G01G02G FD206 GP00 HA03

Claims (5)

[Claims] 1. A retardation plate of a cellulose acylate film containing an aromatic compound having at least two aromatic rings, wherein (a) the concentration of the aromatic compound in the cellulose film is higher than that in the vicinity of the film surface. And (b) the retardation value of the cellulose acylate film at a wavelength of 450 nm is 100 to 1
25 nm, the retardation value (Re590) at a wavelength of 590 nm is 125 to 160 nm, and (c)
The moisture permeability of the cellulose acylate film is 2 to 150.
g / m ² · 24h, a retardation plate characterized by being. 2. A method for producing a retardation plate of a cellulose acylate film, which comprises forming a film of a cellulose acylate solution containing an aromatic compound having at least two aromatic rings by a casting method, and then stretching the film. ) The casting method is a laminated casting method, and the content of the aromatic compound in the cellulose acylate solution is 10%.
1 for at least one inner layer solution for 0 parts by weight
To 30 parts by mass, 0.01 to 10 parts by mass in the outermost layer solution, and the content of the aromatic compound in the outermost layer solution per 100 parts by mass of the cellulose acylate is at least one from the inner layer solution. Low (b) the retardation value of the cellulose acylate film at a wavelength of 450 nm is 100 to 125 nm, and the wavelength is 590 nm.
Has a retardation value of 125 to 160 nm,
(C) The moisture permeability of the cellulose acylate film is 2
The method for producing a retardation plate is characterized in that it is about 150 g / m ² · 24 h. 3. A cellulose acylate retardation plate obtained by forming a film of a cellulose acylate solution containing an aromatic compound having at least two aromatic rings by a casting method, and then stretching the film. The casting method is a laminated casting method, and the content of the aromatic compound in the cellulose acylate solution is 1 to 30 parts by mass in at least one inner layer solution with respect to 100 parts by mass of cellulose acylate. 0.01 to 10 parts by mass in the outermost layer solution, and the content of the aromatic compound in the outermost layer solution is at least 1 per 100 parts by mass of cellulose acylate.
Lower than that of one inner layer solution, (b) the cellulose acylate film has a retardation value at a wavelength of 450 nm of 100 to 125 nm, a retardation value at a wavelength of 590 nm of 125 to 160 nm, and (c) the cellulose acylate film. Permeability of rate film is 2-150g /
A retardation plate characterized by being m ² · 24h. 4. A circularly polarizing plate comprising a polarizing film and two transparent protective films arranged on both sides thereof, wherein at least one of the transparent protective films is the retardation plate according to claim 1. A circularly polarizing plate characterized by that. 5. A reflective liquid crystal display device comprising the retardation plate according to claim 1 or 3 or the circularly polarizing plate according to claim 4.