JP2005307055A - Method for producing cellulose acylate, cellulose acylate film, and optically functional sheet, polarizing plate and liquid crystal display device, using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate having excellent optical transparency, optical anisotropy sufficient even as a thin film, mechanical strength, physical characteristics and water-resistant characteristics; to provide a cellulose acylate film, an optically functional sheet and a polarizing plate, using the cellulose acylate; and to provide a liquid crystal display device hardly causing leak of light and deterioration of planarity and durability of the heat resistance even after being used for a long time. <P>SOLUTION: The method for producing the cellulose acylate by reacting a cellulose with an acylation agent in a solution comprises carrying out the first step acylation reaction of the cellulose dissolved or undissolved but present at the solution interface in a state in which 10-90 mass% of the charged cellulose is in an undissolved state, dissolving the undissolved cellulose, and carrying out the second step acylation reaction by an acylation agent different from the acylation agent at the first step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing cellulose acylate, and a cellulose acylate film used for a liquid crystal display device, an image display device, and the like, a hard coat layer, an antiglare layer, an antireflection layer, The present invention relates to an optical functional sheet and a polarizing plate protective film provided with a prevention layer, an optically anisotropic layer, and the like, a polarizing plate using them, and a liquid crystal display device.

  Cellulose acetate film is excellent in optical transparency, optical isotropy, mechanical strength, physical properties and the like, and has been conventionally used as a support for silver halide light-sensitive material film and a polarizing plate protective film.

  In recent years, the demand for liquid crystal display devices has been rapidly increased due to various advantages such as startup with low voltage and low power consumption, and miniaturization and thinning. A liquid crystal display device is composed of a liquid crystal cell and a polarizing plate, and recently it has become common to use an optical compensation sheet in order to obtain excellent image characteristics. In addition to the STN mode and TN mode, the liquid crystal cell of the liquid crystal display device has an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode, and a VA (Vertically Aligned) mode to improve viewing angle characteristics and response speed. Various display formats have been studied, and the required performance of polarizing plates and optical compensation sheets is increasing.

Cellulose acetate film has been conventionally used as a polarizing plate protective film because of its optical isotropy. However, it is necessary to share a polarizing plate protective film and an optical compensation sheet support to reduce the number of members and to reduce the thickness of the film. Anisotropy has been increased optically to accommodate modes. As the method, it is known to add an additive imparting anisotropy or to dissolve by cooling (Patent Documents 1 and 2).
In addition, it has been studied to stretch cellulose acetate or to replace part of the acetyl substituent of cellulose acetate with a propionate substituent (Patent Documents 3, 4, and 5). However, although the cellulose acylate film described in Patent Document 5 has increased optical anisotropy, its mechanical strength, physical characteristics, thermal characteristics, water resistance characteristics, etc. are not sufficient, and it is assembled into a liquid crystal display device. In such a case, there are problems that light leakage occurs due to long-term use, flatness and wet heat durability are deteriorated, and improvement is demanded.

JP 2000-1111914 A JP 2000-154261 A JP 2000-137116 A JP-A-8-231761 JP 2002-71957 A

  An object of the present invention is to provide a cellulose acylate that can produce a cellulose acylate film having excellent optical transparency and sufficient optical anisotropy, mechanical strength, physical properties, thermal properties, and water resistance properties as a thin film. That is. Moreover, it is providing the cellulose acylate film using the said cellulose acylate, an optical functional sheet, and a polarizing plate. A further object of the present invention is to provide a liquid crystal display in which light leakage does not occur even after long-term use and flatness and wet heat durability are not deteriorated due to the improvement of the aforementioned characteristics when incorporated in a liquid crystal display device. Is to provide a device. Furthermore, another object of the present invention is to provide a photographic light-sensitive material that uses the cellulose acylate to obtain an excellent image.

The object of the present invention has been achieved by a cellulose acylate, a cellulose acylate film, an optical functional sheet, a polarizing plate and a liquid crystal display device having the following constitution.
(1) A method for producing cellulose acylate in which cellulose and an acylating agent are reacted in a solution, wherein 10% by mass to 90% by mass of input cellulose is in an undissolved state, dissolved cellulose and undissolved Performs the first-stage acylation reaction on the cellulose present at the solution interface, then dissolves the undissolved cellulose, and performs the second-stage acylation reaction with an acylating agent different from the first-stage acylating agent. A method for producing a cellulose acylate characterized by the above.
(2) A method for producing cellulose acylate in which cellulose and an acylating agent are reacted, wherein all three hydroxyl groups in a glucose unit are the same acyl group by the first-stage acylating agent or the second-stage acylating agent. The method for producing cellulose acylate as described in (1), wherein
(3) A method for producing cellulose acylate in which cellulose and an acylating agent are reacted, wherein the first-stage acylating agent is an acetylating agent and the second-stage acylating agent is a propionylating agent or butyrylating agent. The method for producing cellulose acylate according to (1) or (2), comprising:
(4) A cellulose acylate film formed by using a cellulose acylate produced by the production method according to any one of (1) to (3).
(5) A cellulose acylate produced by the production method according to any one of (1) to (3), wherein the substituent is introduced by the first-stage acylating agent or the second-stage acylation. A cellulose acylate film produced from a cellulose acylate having a block in which all of the substituents introduced by the agent are the same acyl groups in glucose units and the glucose units are continuous.
(6) The substituent of the cellulose acylate produced by the production method according to any one of (1) to (3) is an acetyl group and an acyl group having 3 to 22 carbon atoms, and all of the acetyl groups are A cellulose acylate film produced from a cellulose acylate having a block composed of continuous glucose units substituted with
(7) The Re value (unit: nm) and Rth value (unit: nm) of the cellulose acylate film defined by the formulas (I) and (II) and measured at a wavelength of 633 nm are the formulas (III) and (IV), respectively. The humidity dependence of the Re value and Rth value in the range of 15% relative humidity of 30 ° C to 85% relative humidity of 30 ° C is 2% /% relative humidity or less in absolute value, and 3% /% relative humidity. The cellulose acylate film according to any one of (4) to (6), wherein:
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
[Wherein nx is the refractive index in the slow axis direction in the cellulose acylate film surface; ny is the refractive index in the fast axis direction in the cellulose acylate film surface; nz is the cellulose acylate] The refractive index in the thickness direction of the film; and d is the thickness of the cellulose acylate film].
(III) 20 ≦ Re ≦ 100
(IV) 70 ≦ Rth ≦ 400
(8) The values of the tensile modulus of the cellulose acylate film having the maximum tensile modulus and the direction perpendicular thereto are 310 kg / mm ² or more and 250 kg / mm ² or more, respectively. The cellulose acylate film according to any one of (4) to (7), wherein the values in the vertical direction are 30% or less and 18% or less, respectively.
(9) The cellulose acylate film is characterized in that the value of the propagation velocity of sound waves in the maximum direction and the direction perpendicular thereto are at least 2.33 km / s and 2.04 km / s or more. The cellulose acylate film according to any one of (8).
(10) The cellulose acylate film has a moisture permeability (converted to a film thickness of 80 μ) at 40 ° C. and 90% relative humidity of 24 hr of 80 g / m ² · 24 hr to 600 g / m ² · 24 hr or less (4 The cellulose acylate film according to any one of (1) to (9).
(11) The cellulose acylate film is characterized in that the value of the thermal expansion coefficient in the maximum direction and the direction perpendicular thereto is at least 84 × 10 ⁻⁶ / ° C. and 45 × 10 ⁻⁶ / ° C. or less ( The cellulose acylate film according to any one of 4) to (10).
(12) The cellulose acylate substituent is composed of an acetyl group and an acyl group having 3 to 22 carbon atoms, and the cellulose acylate has a continuous portion of glucose units closed by the acetyl substituent. The degree of acyl substitution SB ′ of the formula 3-22 satisfies the following relational expressions (V), (VI), (VII), and the average degree of polymerization of cellulose acylate is 180-800 (5 The cellulose acylate film as described in any one of (1) to (11).
(V) 2.4 ≦ SA ′ + SB ′ ≦ 3.0
(VI) 1.8 ≦ SA ′ ≦ 2.8
(VII) 0.2 ≦ SB ′ ≦ 0.8
(13) Re ₍₄₃₀₎ value (unit: nm) and Rth ₍₄₃₀₎ value (unit: nm) and Re value (unit: nm) and Rth measured at 633 nm of the cellulose acylate film measured at a wavelength of 430 nm The cellulose acylate film according to any one of (4) to (12), wherein the value (unit: nm) satisfies the following relational expressions (VIII) and (IX):
(VIII) 0 ≦ | Re-Re ₍₄₃₀₎ | ≦ 20
(IX) 0 ≦ | Rth−Rth ₍₄₃₀₎ | ≦ 80
(14) The cellulose acylate film as described in any one of (4) to (13), wherein the cellulose acylate film has a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or less.
(15) In any one of (4) to (14), the dimensional change when the cellulose acylate film is allowed to stand for 24 hours at 60 ° C. and 95% RH is 5% or less. The cellulose acylate film described.
(16) The cellulose acylate film contains at least one or more additives selected from a plasticizer, an ultraviolet absorber, an antioxidant, a retardation adjusting agent, and a peeling accelerator (4) to ( The cellulose acylate film according to any one of 15).
(17) The cellulose acylate film according to any one of (4) to (16), wherein the cellulose acylate film contains fine particles.
(18) The cellulose acylate film as described in any one of (4) to (17), wherein the cellulose acylate film has a thickness of 5 to 500 μm.
(19) Cellulose containing 70% or more of cellulose acylate having a continuous portion of glucose units in which the substituent of the cellulose acylate is composed of an acetyl group and an acyl group having 3 to 22 carbon atoms and substituted with the acetyl substituent A cellulose acylate film formula (I), (II) obtained by casting a solution prepared by dissolving an acylate in an organic solvent onto a support, evaporating the solvent to release the film, and stretching the film. The Re value (unit: nm) and Rth value (unit: nm) measured at a wavelength of 633 nm satisfy Formula (III) and Formula (IV), respectively, and the Re value and the Rth value are 15% at 15 ° C. Cellulosics characterized in that the humidity dependence in the range from relative humidity to 30 ° C. and 85% relative humidity is 2% /% relative humidity or less and 3% /% relative humidity or less in absolute value, respectively. Manufacturing method of the scan acylate film.
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
[Wherein nx is the refractive index in the slow axis direction in the cellulose acylate film surface; ny is the refractive index in the fast axis direction in the cellulose acylate film surface; nz is the cellulose acylate] The refractive index in the thickness direction of the film; and d is the thickness of the cellulose acylate film].
(III) 20 ≦ Re ≦ 100
(IV) 70 ≦ Rth ≦ 400
(20) The cellulose acylate film according to any one of (4) to (19), at least one selected from a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an optically anisotropic layer. An optical functional sheet provided with a layer.
(21) The cellulose acylate film according to any one of (4) to (19) or the optical functional sheet according to (20) is used as a protective film for a polarizer. A polarizing plate.
(22) The cellulose acylate film according to any one of (5) to (19), the optical functional sheet according to (20), or at least one polarizing plate according to (21) is used. A liquid crystal display device.

In the cellulose acylate used in the present invention, after the first-stage acylation reaction is performed under conditions where cellulose is not uniformly dissolved in a solution containing an acylating agent, the reaction system is made to be a homogeneous dissolution system. Then, by performing the second stage reaction with an acylating agent different from the first stage acylating agent, a block is formed in which glucose units in which three hydroxyl groups of the glucose unit are substituted with the same substituent are continuous. It is considered that the produced cellulose acylate could be produced.
In cellulose acylate, acyl substituents different from other parts are present in the form of blocks (continuous parts are present), thereby forming a strong microcrystalline region and excellent mechanical strength, mechanical properties, thermal properties, An excellent in-plane retardation and retardation in the thickness direction can be exhibited by coexistence of optically different acyl substituents while exhibiting water resistance.

The cellulose acylate film in the present invention will be described in detail.
As an example of the cellulose acylate film in the present invention, there is an acylate substituent consisting of acetate and an acylate having 3 to 22 carbon atoms. A cellulose acetate acylate film is an acylate substituent group consisting of an acetate and an acylate having 3 to 22 carbon atoms, as an acylate substituent group consisting of acetate and propionate is called cellulose acetate propionate. Call.

[Production method of cellulose acylate and cellulose acylate]
The cellulose acylate used in the present invention is described below. Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, softwood pulp), and any cellulose acylate obtained from any raw material cellulose can be used, optionally mixed. May be.
In the present invention, cellulose acylate is produced by esterification from cellulose, but the aforementioned cellulose is not used as it is, but is used as refined linter and refined high-quality wood pulp by refining linter or pulp.
The cellulose acylate raw material cotton used in the present invention is described in detail on pages 7 to 12 of the Japan Institute of Invention and Technology (public technical number 2001-1745, published on March 15, 2001, Japan Society of Invention). .

  In the cellulose acylate (cellulose acetate acylate) in the present invention, an acid anhydride or an acid chloride is preferably used as the acylating agent, and the acylation reaction is first performed under a condition where the cellulose and the acylating agent are not uniformly mixed. After carrying out the second stage reaction, the reaction system can be mixed (dissolved) uniformly and synthesized by carrying out the second stage reaction. When the acylating agent is an acid anhydride, an organic acid (eg, acetic acid) or methylene chloride is used as a reaction solvent. Moreover, in order to form the state which has not melt | dissolved a part of cellulose, a poor solvent is used. As the catalyst, a protic catalyst such as sulfuric acid is preferably used. When the acylating agent is an acid chloride, a basic compound is preferably used as the catalyst.

The cellulose dissolved state in the first-stage acylation reaction is preferably 10% by mass to 90% by mass of the input cellulose, and more preferably 10% by mass to 60% by mass in the undissolved state. Preferably, it is 10 mass%-30 mass%.
When the undissolved content is less than 10% by mass or more than 90% by mass, the substituent formed by the first-stage acylation reaction or the substituent formed by the second-stage acylation reaction The ratio is too small to form a block in which glucose units substituted with only the respective substituents are continuous, and the blocking effect of the substituents cannot be exhibited.
The proportion of undissolved content is determined by sampling and filtering the undissolved content-containing mixed solution at the time when the first stage reaction is completed, and the amount of cellulose (a) contained in the solid content that could not be filtered It can be determined by comparing the total amount of cellulose (b) with the total amount of cellulose (c) in the filtrate and the amount of cellulose (e) in the cellulose acylate.
That is, the undissolved rate is obtained by (a + b) / (a + b + c + d).

Further, it is preferable that at least one of the acyl group by the first-stage acylating agent and the acyl group by the second acylating agent is a single acyl group, It is preferred that the stage acylating agent is an acylating agent that forms a single acyl group. By doing so, it becomes easy to form the block part which the glucose unit which has the said single substituent continues, and it is preferable.
Furthermore, as the acylating agent in the first stage and the second stage, those which form an acyl substituent having a small number of carbon atoms whose characteristics are intermittent to each other are preferable, and are an acetylating agent, a propionylating agent or a butyrylating agent. Among them, it is more preferable that the first-stage acylating agent is an acetylating agent, the second-stage acylating agent contains a propionylating agent and a butyrylating agent, and the first-stage acylating agent is It is an acetylating agent, and it is particularly preferred that the second-stage acylating agent mainly contains either a propionylating agent or a butyrylating agent.

Synthetic methods include, for example, cellulose with organic acids corresponding to acetyl groups and other acyl groups (acetic acid, propionic acid, butyric acid), their acid anhydrides (acetic anhydride, propionic anhydride, butyric anhydride), or poor cellulose. Using a mixed organic acid component containing an organic solvent that is a solvent and does not inhibit the acylation reaction, the first-stage acylation is performed under the condition that the amount of cellulose is larger than that of the mixed organic acid and the organic solvent. Subsequently, after adding the mixed organic acid component excluding the poor solvent and completely dissolving and mixing the cellulose and its partially acylated product, the second stage reaction is performed to make the acetyl substitution site and the acyl substitution site non-uniform. A cellulose acylate that is present and has a continuous portion of acetyl substitution sites is synthesized. In this method, cellulose such as cotton linter or wood pulp is activated with an organic acid such as acetic acid and then acylated using a mixture of organic acid components as described above in the presence of a sulfuric acid catalyst. It is preferable to do.
In this case, the amount of the organic acid to be added is preferably about 1 to 5 times equivalent in terms of chemical equivalent to the amount of hydroxyl group present in the dissolved cellulose in the first stage, preferably 1 to 3 times equivalent. Is more preferable, and 1.2 times equivalent to 2.4 times equivalent is particularly preferable. In the second stage, it is preferable to make the amount excessive.

  In this acylation treatment, a hydrolysis reaction (depolymerization reaction) of the cellulose main chain (β-1,4-glycoside bond) tends to proceed in addition to the acylation reaction. As the hydrolysis reaction of the main chain proceeds, the degree of polymerization of cellulose acylate decreases, and the physical properties of the cellulose acylate film to be produced decrease. Therefore, the reaction conditions such as the reaction temperature need to be determined in consideration of the degree of polymerization and molecular weight of the cellulose acylate to be obtained and the length and ratio of continuous acetyl substitution sites. Moreover, it does not matter at all if the cellulose acylate used in the present invention is prepared by a synthesis method not based on this method.

  In order to obtain cellulose acetate acylate having a high degree of polymerization (high molecular weight), it is important to adjust the maximum temperature in the acetylation and acylation reaction step to 50 ° C. or less. The maximum temperature is adjusted to 25 to 50 ° C, preferably 30 to 45 ° C. When the reaction temperature is less than 25 ° C., the acetylation and acylation reaction may not proceed smoothly. When the reaction temperature exceeds 50 ° C., acyl groups or acetyl groups are exchanged by the acyl exchange reaction, and the blocking properties of acyl groups and acetyl groups are lowered, and the degree of polymerization of cellulose acetate acylate is likely to be lowered. After the acetylation and acylation reaction, when the reaction is stopped while suppressing the temperature rise, a decrease in the degree of polymerization can be further suppressed, and cellulose acetate acylate having a high degree of polymerization can be synthesized. That is, when a reaction terminator (eg, water, acetic acid) is added after completion of the reaction, the excess acid anhydride that did not participate in the acylation reaction is hydrolyzed to form a corresponding organic acid as a byproduct. This hydrolysis reaction is accompanied by intense heat generation, and the temperature in the reactor rises. When the rate of addition of the reaction terminator is high, heat is rapidly generated exceeding the cooling capacity of the reactor. Therefore, the hydrolysis reaction of the cellulose main chain proceeds remarkably and the degree of polymerization of the cellulose acetate acylate obtained is lowered.

  Also, part of the catalyst is bound to cellulose during the acetylation and acylation reaction, and most of it is dissociated from the cellulose during the addition of the reaction terminator. However, when the rate of addition of the reaction terminator is high, there is not enough reaction time for the catalyst to dissociate, and a part of the catalyst remains in a state of being bound to cellulose. Cellulose acetate acylate, in which a strong acid catalyst is partially bonded, is very poor in stability, and is easily decomposed by heat during drying of the product to lower the degree of polymerization. For these reasons, after the acetylation and acylation reaction, it is desirable to stop the reaction by adding a reaction terminator over a period of preferably 3 minutes or more, more preferably 3 to 40 minutes. In addition, when the addition time of the reaction terminator exceeds 40 minutes, industrial productivity decreases. As the reaction terminator, water or alcohol that decomposes an acid anhydride is generally used. However, in the present invention, a mixture of water and an organic acid is preferably used as a reaction terminator in order not to precipitate triacetate having low solubility in various organic solvents. When the acetylation and acylation reactions are carried out under the above conditions, a high molecular weight cellulose acetate acylate having a weight average polymerization degree of 500 or more can be easily synthesized.

Next, the cellulose acylate in the present invention produced from the above cellulose raw material will be described. In the cellulose acylate of the present invention, the degree of substitution of cellulose with a hydroxyl group preferably satisfies all of the following formulas (V) to (VII).
(V): 2.4 ≦ SA ′ + SB ′ ≦ 3.0
(VI): 1.8 ≦ SA ′ ≦ 2.8
(VII): 0.2 ≦ SB ′ ≦ 0.8
Here, SA ′ represents the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents degrees. SA represents an acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose.

  The degree of substitution means the ratio of the three hydroxyl groups present in the cellulose structural unit (glucose having β-1,4-glycosidic bonds) being ester-bonded. The degree of substitution can be calculated by measuring the amount of bound fatty acid per unit weight of cellulose. The measurement method is carried out according to ASTM-D817-91.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total substitution degree of SA and SB (SA ′ + SB ′) is preferably 2.4 to 3.0, more preferably 2.5 to 2.96, and particularly preferably 2.60 to 2.90. Further, the substitution degree (SB ′) of SB is 0.2 to 0.8, particularly 0.4 to 0.6. Further, 28% or more of SB is preferably a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, more preferably 31% or more, and particularly 32% or more is 6%. It is also preferable that it is a substituent of a coordinate hydroxyl group. Furthermore, the cellulose acylate film in which the sum of the substitution degrees of SA and SB at the 6-position of cellulose acylate is 0.8 or more, further 0.85 or more, and particularly 0.90 or more is also preferable. Can be mentioned. With these cellulose acylate films, a solution having a preferable solubility can be prepared. In particular, in a non-chlorine organic solvent, a good solution can be prepared.

The number of carbon atoms of the acyl group other than the acetyl group is preferably 3 to 22. The other acyl group is more preferably a propionyl group or a butyryl group, and most preferably a propionyl group. The mixed fatty acid ester of cellulose preferably has a weight average degree of polymerization of 180 to 800, more preferably has a weight average degree of polymerization of 300 to 700, and most preferably has a weight average degree of polymerization of 400 to 600. . The mixed fatty acid ester of cellulose preferably has a number average molecular weight of 40000 to 250,000, more preferably a number average molecular weight of 60000 to 200000, and most preferably a number average molecular weight of 80000 to 18000.
The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

  The acyl group (SB) having 3 to 22 carbon atoms of the cellulose acylate used in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. These preferred SBs include propionyl, butanoyl, keptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, preferable SB is propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like.

[Cellulose acylate film]
In the cellulose acylate film of the present invention, the substituent of the cellulose acylate comprises a substituent by a first-stage acylating agent and a substituent by a second-stage acylating agent, and either one of the acylating agents is glucose. A cellulose acylate film prepared from a cellulose acylate having a continuous portion of glucose units in which the same acyl group is formed by all three hydroxyl groups in the unit and the same acyl group is substituted is preferable.
The cellulose acylate film of the present invention is a mixed fatty acid ester in which the substituent is an acetyl substituent and an acyl group having 3 to 22 carbon atoms, and has a continuous block of glucose units in which the acetyl group is all substituted. More preferably, it consists of cellulose acetate acylate, and it is particularly preferred that the acyl group having 3 to 22 carbon atoms consists of a propionyl substituent or a butyryl substituent.

Here, the glucose unit in which all the same acyl groups are substituted is one in which three hydroxyl groups of glucose are substituted with substantially the same acyl group and are not substituted with other acyl groups. Specifically, as the degree of substitution in a certain number of glucose units of interest, it is preferable that unreacted hydroxyl groups contain 0.2 or less and / or other substituents contain 0.03 or less.
In addition, the continuous block refers to a state in which a plurality of glucose units substituted with the same acyl group are continuously bonded, and the number of glucose units in which the same acyl group is continuously substituted (hereinafter referred to as “repetition number”) is 20 units or more, more preferably 30 units or more, and still more preferably 50 units or more.
The number of continuous portions of glucose units substituted with the same acyl group in one molecule of cellulose acylate (hereinafter, this number is referred to as “the number of consecutive portions”) is preferably 1 to 20, and 2 to 15 locations. More preferably, it is more preferably 3-10. At 20 points or more, the retardation value is difficult to control.
Although a method for confirming regularity has not been found at present, the mechanical property value and the optical property are compatible, and since acylation is performed in two stages and insolubles are present in the first stage, it is continuously detected. Presumed to exist.
In addition, the cellulose acylate film of the present invention may be substantially composed of the cellulose acylate of the present invention, and may contain other cellulose acylates. As used herein, “substantially” means that the proportion of cellulose acylate in the present invention in the total cellulose acylate component is preferably 55% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more. It is.

The cellulose acylate film of the present invention has a Re retardation value (unit: nm) and an Rth retardation value (unit: nm), which are defined by the following formulas (I) and (II) and measured at a wavelength of 633 nm, respectively, in the formula (III). ) And formula (IV) are preferably satisfied.
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
Here, in the formulas (I) and (II), nx is the refractive index in the slow axis direction (direction in which the refractive index becomes maximum) in the film plane. Ny is the refractive index in the fast axis direction (the direction in which the refractive index is minimized) in the film plane. d is the thickness of the film whose unit is nm. On the other hand, nz is the refractive index in the thickness direction of the film.
(III) 20 ≦ Re ≦ 100
(IV) 70 ≦ Rth ≦ 400
The more preferable ranges of the Re retardation value and the Rth retardation value are 25 to 80 nm and 80 to 300 nm, and particularly preferable ranges are 30 to 60 nm and 100 to 250 nm, respectively.

The Rth / Re ratio is preferably -10 to 10, more preferably 0.7 to 7, still more preferably 1.0 to 5.0, and 3.5 to 5.0. It is particularly preferred.
Further, the Re retardation value and the Rth retardation value preferably have little variation in the film width direction, and are within ± 5 nm from the average value.

  The film thickness of the cellulose acylate film of the present invention is such that the polarizing plate protective sheet, the optical functional sheet such as the optical compensation sheet, and the liquid crystal display device are thinned and lightened, the transmittance is increased, the contrast and the display brightness are improved, etc. In order to optimize the optical characteristics, the thickness is preferably 5 to 500 μm, more preferably 30 to 200 μm, still more preferably 30 to 120 μm, and particularly preferably 30 to 80 μm. If it is less than 5 μm, it is difficult and difficult to handle a long and wide support. The long and wide form is preferable for improving productivity and providing the product at low cost. The length of the long roll is preferably 100 to 5000 m, more preferably 500 to 4500 m, and particularly preferably 1000 to 4000 m. The width of the long roll is preferably as wide as possible, and is preferably 0.7 m or more. It is more preferable that it is 0.7-3 m, and it is especially preferable that it is 1.0-2.5 m.

  Further, it is preferable that the humidity dependence of 15% to 85% RH at 15 ° C. to 40 ° C. of the Re value and the Rth value is smaller, and each absolute value is 2% relative to the value at each temperature of 50% RH. /% RH or less, preferably 3% /% RH or less. In particular, the humidity dependence between 30 ° C. and 15% RH to 30 ° C. and 85% RH is preferably 1.8% /% RH or less and 2.8% /% RH or less, respectively, in absolute value. The “humidity dependency” referred to here means a constant temperature and humidity coefficient in the present invention.

  Further, it is preferable that the temperature dependence from 5 ° C. to 85 ° C. in the Re value and the Rth value from 15% RH to 85% RH is as small as possible. It is preferably 6% / ° C. or less. In particular, the temperature dependence between 5 ° C. and 55% RH to 85 ° C. and 55% RH is preferably 4% / ° C. or less and 5% / ° C. or less in absolute value. The “temperature dependency” referred to herein means a constant humidity temperature coefficient in the present invention.

The cellulose acylate film of the present invention preferably satisfies the following relational expressions (V) and (VI), and is preferable because it does not cause excessive birefringence because the wavelength dispersion of retardation is small. Even when an optically anisotropic layer having birefringence is provided, only the birefringence of the optically anisotropic layer can be exhibited.
(VIII) 0 ≦ | Re-Re ₍₄₃₀₎ | ≦ 20
(IX) 0 ≦ | Rth−Rth ₍₄₃₀₎ | ≦ 80

(Tensile modulus, elongation at break)
The tensile modulus of the cellulose acylate film of the present invention has a maximum value in the casting direction, the direction perpendicular to the casting direction, or the direction obliquely intersecting the casting direction, and the tensile modulus in the direction of the maximum value is is preferably 310kgf / mm ² or more, more preferably 330kgf / mm ² or more, particularly preferably 350 kgf / mm ² or more. It is preferable that a direction perpendicular to the direction of the elastic modulus of the maximum value is 250 kgf / mm ² or more, more preferably 270 kgf / mm ² or more, and particularly preferably 290kgf / mm ² or more. The larger the tensile elastic modulus is, the more preferable, but 540 kgf / mm ² or less is practically preferable in both the maximum value direction and the vertical direction.
The breaking elongation of the cellulose acylate film of the present invention has a maximum value in the casting direction, the direction perpendicular to the casting direction or the direction obliquely intersecting the casting direction, and the breaking elongation in the direction of the maximum value is It is preferably 30% or less, more preferably 27% or less, and particularly preferably 24% or less. Further, the breaking elongation in the direction perpendicular to the maximum value is preferably 18% or less, more preferably 16% or less, and particularly preferably 15% or less. The smaller the elongation at break, the better, but 1% or more is practically preferable in both the maximum value direction and the vertical direction.
As a specific measuring method, using a universal tensile tester STM T50BP manufactured by Toyo Baldwin, a tensile elastic modulus is obtained from a stress at 0.5% elongation at a pulling rate of 10% / min in an atmosphere of 25 ° C. and 60%. The breaking elongation was determined from the breaking point of the cellulose acylate film.

(Sound wave propagation speed)
The sound wave propagation speed of the cellulose acylate film of the present invention has a maximum value in the casting direction, the direction perpendicular to the casting direction, or the direction obliquely intersecting the casting direction, and the sound wave propagation speed in the direction of the maximum value is It is preferably 2.33 km / s or more, more preferably 2.37 km / s or more, and particularly preferably 2.41 km / s or more. The sound wave velocity in the direction perpendicular to the maximum value is preferably 2.04 km / s or more, more preferably 2.08 km / s or more, and particularly preferably 2.12 km / s or more. For the measurement, the propagation speed of the longitudinal wave vibration of the ultrasonic pulse was obtained by a sonic meter (SST-110 manufactured by Nomura Corporation).

(Moisture permeability)
Moisture permeability of the cellulose acylate film of the present invention, based on the temperature 40 ° C. The JIS standard JIS Z0208 condition, measured at a humidity ^{90% RH, 80g / m 2} · 24h or more 600 g / m ² · in 80μm thickness in terms It is preferably 24 hours or less. More preferably 100~500g / m ² · 24h, and particularly preferably 120~400g / m ² · 24h. If it exceeds 600 g / m ² · 24h, the absolute value of the humidity dependence of the Re value and the absolute value of the humidity dependence of the Rth value tend to exceed the prescribed values. Also, in the case of an optical compensation sheet in which an optically anisotropic layer is laminated on a cellulose acylate film, the absolute value of the humidity dependence of the Re value and Rth value tends to exceed the specified value, which is not preferable. . When a polarizing plate or an optical compensation sheet is incorporated in a liquid crystal display device, it causes a change in color and a decrease in viewing angle. In addition, when the moisture permeability of the cellulose acylate film is less than 80 g / m ² · 24 h, when the polarizing plate is prepared by sticking to both surfaces of the polarizing film, drying of the adhesive is hindered by the cellulose acylate film. Cause a defect.

The measurement method of moisture permeability is “Polymer Properties II” (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount method) The cellulose acylate film sample 70 mmφ of the present invention was conditioned at 40 ° C. and 90% RH for 24 hours and applied to a moisture permeation test apparatus (KK-709007, Toyo Seiki Co., Ltd.). The amount of water per unit area was calculated (g / m ² ) and obtained. Further, it is known that the moisture permeability is inversely proportional to the film thickness, and was converted by the following formula.
80 μm film thickness converted moisture permeability = (actually measured moisture permeability) × (actually measured film thickness (μm) / 80 (μm))

(Coefficient of thermal expansion)
The thermal expansion coefficient of the cellulose acylate film of the present invention has a maximum value in the casting direction, the direction perpendicular to the casting direction, or the direction obliquely intersecting the casting direction, and the thermal expansion coefficient in the direction of the maximum value and The values in the direction perpendicular to it are preferably 84 × 10 ⁻⁶ / ° C. or lower and 45 × 10 ⁻⁶ / ° C. or lower, respectively, and are 78 × 10 ⁻⁶ / ° C. or lower and 44 × 10 ⁻⁶ / ° C. or lower. It is more preferable that it is 70 × 10 ⁻⁶ / ° C. or lower and 43 × 10 ⁻⁶ / ° C. or lower. A smaller thermal expansion coefficient is preferable, but it is usually a value of 10 × 10 ⁻⁶ / ° C. or more. The thermal expansion coefficient indicates the amount of change in the sample length when the temperature is changed under a constant humidity. By adjusting the coefficient of thermal expansion, when the cellulose acylate film of the present invention is used as an optical compensation film support, while maintaining the optical compensation function of the optical compensation film, the frame-shaped transmittance rises, i.e., light due to distortion. Leakage can be prevented.

(Photoelastic coefficient)
The photoelastic coefficient of the cellulose acylate film of the present invention is preferably 50 × 10 ⁻¹³ cm ² / dyne or less. It is more preferably 30 × 10 ⁻¹³ cm ² / dyne or less, and further preferably 20 × 10 ⁻¹³ cm ² / dyne or less. As a specific measuring method, a tensile stress is applied to the major axis direction of a 12 mm × 120 mm cellulose acylate film sample, and the retardation at that time is measured with an ellipsometer (M150, JASCO Corporation). The photoelastic coefficient was calculated from the amount of change in retardation with respect to.

(Dimension change)
The dimensional stability of the cellulose acylate film of the present invention is as follows: the dimensional change rate after standing for 24 hours under the conditions of 60 ° C. and 90% RH (high humidity) and 90 ° C. and 5% RH. It is preferable that the dimensional change rate after standing for 24 hours (high temperature) is 0.5% or less.
More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.
As a specific measurement method, two cellulose acylate film samples 30 mm × 120 mm were prepared, conditioned at 25 ° C. and 60% RH for 24 hours, and at both ends with an automatic pin gauge (Shinto Kagaku Co., Ltd.). Holes of 6 mmφ were opened at 100 mm intervals to obtain the original punch interval (L0). Punch interval size (L1) after one sample was treated at 60 ° C. and 90% RH for 24 hours, punch after one sample was treated at 90 ° C. and 5% RH for 24 hours The distance dimension (L2) was measured. Measurement was made to a minimum scale of 1/1000 mm at all intervals. Dimensional change rate of 60 ° C. and 90% RH (high humidity) = {| L0−L1 | / L0} × 100, Dimensional change rate of 90 ° C. and 5% RH (high temperature) = {| L0−L2 | / The dimensional change rate was determined as L0} × 100.

(Transmittance)
The transmittance of visible light (615 nm) was measured on a 20 mm × 70 mm sample at 25 ° C. and 60% RH with a transparency measuring instrument (AKA phototube colorimeter, KOTAKI Corporation).

(Spectral characteristics)
A sample 13 mm × 40 mm was measured for transmittance at a wavelength of 300 to 450 nm with a spectrophotometer (U-3210, Hitachi, Ltd.) at 25 ° C. and 60% RH. The inclination width was determined at a wavelength of 72% −a wavelength of 5%. The limit wavelength was expressed by a wavelength of (gradient width / 2) + 5%. The absorption edge is represented by a wavelength having a transmittance of 0.4%. From this, the transmittances at 380 nm and 350 nm were evaluated.

(Haze)
The haze of the cellulose acylate film of the present invention is preferably 0.01 to 2.0%. More preferably, it is 0.05 to 1.5%, and more preferably 0.1 to 1.0%. As an optical film, the transparency of the film is important. The haze was measured by measuring a 40 mm × 80 mm cellulose acylate film sample of the present invention at 25 ° C. and 60% RH with a haze meter (HGM-2DP, Suga Test Instruments) in accordance with JIS K-6714.

(Surface roughness)
The surface of the cellulose acylate film of the present invention has an arithmetic average roughness (Ra) of surface irregularities of the film based on JISB0601-1994 of 0.1 μm or less and a maximum height (Ry) of 0.5 μm or less. preferable. Preferably, the arithmetic average roughness (Ra) is 0.05 μm or less, and the maximum height (Ry) is 0.2 μm or less. The concave and convex shapes on the film surface can be evaluated by an atomic force microscope (AFM).

(curl)
The curl value in the width direction of the cellulose acylate film of the present invention is preferably −10 / m to + 10 / m. The cellulose acylate film of the present invention is subjected to surface treatment, which will be described later, rubbing treatment when coating an optically anisotropic layer, alignment film, coating and bonding of an optically anisotropic layer, etc. When the curl value in the width direction of the cellulose acylate film of the present invention is outside the above range, the film handling may be hindered and the film may be cut. In addition, the film is strongly contacted with the transport roll at the edge and center of the film, so dust generation is likely to occur, and foreign matter adheres to the film, and the point defect of the optical compensation film and the frequency of coating stripes are allowed. May exceed the value. Further, by setting the curl in the above-mentioned range, it is possible to reduce color spot failure that is likely to occur when the optically anisotropic layer is installed, and it is possible to prevent bubbles from entering when the polarizing film is bonded, which is preferable.
The curl value can be measured according to a measurement method (ANSI / ASCPH1.29-1985) defined by the American National Standards Institute.

(Tear strength)
The tear strength (Elmendorf tear method) based on the tear test method of JISK7128-2: 1998 is preferably 2 g or more when the film thickness of the cellulose acylate film of the present invention is in the range of 20 to 80 μm. More preferably, it is 5-25g, Furthermore, it is 6-25g. Moreover, 8 g or more is preferable at 60 micrometer conversion, More preferably, it is 8-15g. Specifically, it can be measured using a light load tear strength tester after conditioning a sample piece of 50 mm × 64 mm under the conditions of 25 ° C. and 65% RH for 2 hours.

(Retention of film)
In the cellulose acylate film of the present invention, retention of various compounds added to the film is required. Specifically, it is preferable that the mass change of the film when the cellulose acylate film of the present invention is allowed to stand for 48 hours under the condition of 80 ° C./90% RH is 0 to 5%. More preferably, it is 0 to 3%, and still more preferably 0 to 2%.
The retaining property evaluation method is to cut a sample into a size of 10 cm × 10 cm, measure the mass after being left for 24 hours in an atmosphere of 23 ° C. and 55% RH, and measure 80 ± 5 ° C. and 90 ± 10% RH. It was left under conditions for 48 hours. The surface of the sample after the treatment was lightly wiped, the mass after standing for 1 day at 23 ° C. and 55% RH was measured, and the retention was calculated by the following method.
Retention property (mass%) = {(mass before standing−mass after standing) / mass before standing} × 100

(Residual solvent amount)
It is preferable to dry on the conditions that the amount of residual solvents with respect to the cellulose acylate film of the present invention is in the range of 0.01 to 1.5% by mass. More preferably, it is 0.01-1.0 mass%. Curling can be suppressed by setting the residual solvent amount of the transparent support used in the present invention to 1.5% or less. More preferably, it is 1.0% or less. This is presumably because free deposition is reduced by reducing the amount of residual solvent during film formation by the solvent casting method described above.

(Glass transition temperature Tg)
The glass transition temperature Tg of the cellulose acylate film of the present invention is 80 to 165 ° C. From the viewpoint of heat resistance, Tg is more preferably 100 to 160 ° C, and particularly preferably 110 to 150 ° C. The glass transition temperature Tg is measured with a differential scanning calorimeter (DSC2910, TA Instruments) using a cellulose acylate film sample of 10 mg of the present invention at a temperature rising / falling rate of 5 ° C./min from room temperature to 200 ° C. And the glass transition temperature Tg was calculated.

(Equilibrium moisture content)
The equilibrium water content of the cellulose acylate film of the present invention is 25 ° C. at 80 ° C. regardless of the film thickness so as not to impair the adhesion with a water-soluble polymer such as polyvinyl alcohol when used as a protective film for a polarizing plate. The equilibrium moisture content at% RH is preferably 0 to 4%. It is more preferably 0.1 to 3.5%, and particularly preferably 1 to 3%. An equilibrium moisture content of 4% or more is not preferable because the dependence of retardation on humidity changes becomes too great when used as a support for an optical compensation film.
The water content was measured by measuring the cellulose acylate film sample 7 mm × 35 mm of the present invention with a Karl Fischer method using a moisture measuring device and a sample drying apparatus (CA-03, VA-05, both Mitsubishi Chemical Corporation). . It was calculated by dividing the amount of water (g) by the sample weight (g).

(Molecular orientation axis)
A sample 70 mm x 100 mm was conditioned at 25 ° C and 65% RH for 2 hours. The orientation axis was calculated.

(Axis misalignment)
Moreover, the axis | shaft misalignment angle was measured with the automatic birefringence meter (KOBRA-21ADH, Oji Scientific Instruments). Twenty points were measured at equal intervals over the entire width in the width direction, and the average absolute value was determined. The range of the slow axis angle (axis deviation) is the measurement of 20 points at equal intervals over the entire width direction. It is what took.

  In the cellulose acylate film of the present invention, various additives (for example, plasticizers, ultraviolet absorbers, deterioration inhibitors (antioxidants)) depending on the use in each preparation step are added to the cellulose acylate solution (composition). ), An optical anisotropy control agent (retardation adjusting agent), a peeling accelerator, an infrared absorber, and the like, and at least one or more additives are preferably contained. They may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing materials at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, Japanese Patent Application Laid-Open No. 2001-151901. Furthermore, infrared absorbing dyes are described in, for example, JP-A-2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step.

  Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a cellulose acylate film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, they are described in Japanese Patent Application Laid-Open No. 2001-151902, etc., which are conventionally known techniques. Furthermore, for these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used. The amount of these additives used is preferably used in the range of 0.001 to 20% by mass in the entire cellulose acylate composition.

(Additive ratio)
In the cellulose acylate film of the present invention, the total amount of compounds having a molecular weight of 3000 or less is preferably 5 to 45% based on the weight of the cellulose acylate. More preferably, it is 10 to 40%, and more preferably 15 to 30%. The molecular weight is preferably 3000 or less, more preferably 2000 or less, and even more preferably 1000 or less. When the total amount of these compounds is 5% or less, as a property of cellulose acylate alone, there is a problem that, for example, optical performance and physical strength are likely to fluctuate with changes in temperature and humidity. Further, when the total amount of these compounds is 45% or more, problems such as exceeding the limit of compatibility of the compounds in the cellulose acylate film and depositing on the film surface to cause the film to become cloudy (crying out from the film) occur. It becomes easy.

The cellulose acylate film of the present invention preferably contains fine particles added to the cellulose acylate composition in order to maintain good scratch resistance and film transportability.
They are conventionally used as matting agents, antiblocking agents, or anti-kissing agents. They are not particularly limited as long as they have the functions described above, but preferred specific examples of these matting agents include inorganic compounds such as silicon-containing compounds, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, and oxidation. Barium, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. More preferred is an inorganic compound containing silicon or zirconium oxide, but silicon dioxide is particularly preferred because the turbidity of the cellulose acylate film can be reduced.
In addition, surface-treated inorganic fine particles are also preferable because of good dispersibility in cellulose acylate. Examples of the treatment method include the method described in JP-A No. 54-57562. Examples of the particles include those described in JP-A No. 2001-151936.
As the organic compound, for example, polymers such as cross-linked polystyrene, silicone resin, fluororesin and acrylic resin are preferable, and among them, silicone resin is preferably used. Among silicone resins, those having a three-dimensional network structure are particularly preferable.

When these additives are added to the cellulose acylate solution, the method is not particularly limited, and any method can be used as long as a desired cellulose acylate solution can be obtained.
For example, an additive may be contained at the stage of mixing cellulose acylate and a solvent, or an additive may be added after preparing a mixed solution with cellulose acylate and a solvent. Furthermore, it may be added and mixed immediately before casting the dope, which is a so-called immediately preceding addition method, and screw type kneading is installed on-line for the mixing. The mixture of the additive may be added by itself, but it may be dissolved in advance using a solvent or a binder (preferably cellulose acylate), or may be used as a dispersed and stabilized solvent in some cases. Is also a preferred embodiment.

The primary average particle diameter of these fine particles is preferably 0.001 to 20 μm, more preferably 0.001 to 10 μm, and still more preferably 0.002 to 1 μm, from the viewpoint of keeping haze low. It is particularly preferably 0.005 to 0.5 μm.
The amount of fine particles added to cellulose acylate is preferably 0.01 to 0.3 parts by mass, more preferably 0.05 to 0.2 parts by mass with respect to 100 parts by mass of cellulose acylate.

Next, a method for producing the cellulose acylate film of the present invention will be described. As a method and equipment for producing the cellulose acylate film of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film can be used.
The cellulose acylate in which the substituent of the cellulose acylate in the present invention is composed of an acetyl group and an acyl group having 3 to 22 carbon atoms and contains 70% or more of cellulose acylate having a continuous portion of glucose units substituted by the acetyl substituent. Cellulose acylate film formulas (I) and (II) obtained by casting a solution obtained by dissolving a rate in an organic solvent onto a support, evaporating the solvent to release the film, and stretching the film. And the Re value and Rth value measured at a wavelength of 633 nm satisfy formula (III) and formula (IV), respectively, and the humidity in the range of 30 ° C. 15% RH to 30 ° C. 85% RH of the Re value and Rth value. By the method for producing a cellulose acylate film, the dependency is 2% /% RH or less and 3% /% RH or less in absolute value, Since cetyl substitution sites and acyl substitution sites are heterogeneous, a strong microcrystalline region similar to cellulose acetate is formed in acetyl substitution sites that are not acyl substituted, resulting in excellent mechanical strength, mechanical properties, heat A cellulose acylate film exhibiting properties and water resistance can be produced. In addition, the presence of optically heterogeneous acyl-substituted cellulose in the acetyl-substituted cellulose matrix results in a cellulose acylate film that expresses a necessary and sufficient in-plane retardation and retardation in the thickness direction.

Hereinafter, a preferred casting film forming method and its casting film production line in the present invention will be described with reference to FIG. The dope (cellulose acylate organic solvent solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle (also called a mixing tank) (11), and the foam contained in the dope is defoamed for final preparation. To do. The dope is fed from the dope discharge port to a pressurization die (casting die) (14) through a pressurization metering gear pump (also referred to as a liquid feed pump) (12) capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations. At the peeling point where the metal support is almost cast around the casting support (also called casting band) (15) running endlessly from the die (slit) of the pressure die, The solvent is evaporated and the dry-dried dope film (also called web) is peeled off from the metal support. This apparatus is further provided with a casting part side rotating drum (16), a non-casting part side rotating drum (17), a guide roll (18), and a stripping roll (19). The resulting web is sandwiched between clips, stretched with a tenter while maintaining the width, dried in the drying section (22) while being transported, and subsequently stretched and transported by a roll group of a drying apparatus to finish drying, and the film (23) is wound up to a predetermined length by the winder (21) through the guide roll (20).
The combination of the tenter and the roll group drying device varies depending on the purpose, and in addition to the solution casting film forming device, for surface processing of films such as undercoat layers, antistatic layers, antihalation layers, protective layers, etc. A coating device can be added. Each of these manufacturing processes is described in detail on pages 25 to 30 in the Japan Institute of Invention Disclosure Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). (Including rolling), metal support, drying, peeling, stretching and the like.

Here, although the space temperature of a casting part is not specifically limited in this invention, It is preferable that it is -50 degreeC-50 degreeC. Furthermore, it is preferable that it is -30 degreeC-40 degreeC. In particular, the cellulose acylate solution cast at a low space temperature can be cooled on the support instantly to increase the gel strength, thereby holding the film containing the organic solvent. This makes it possible to peel the cellulose acylate from the support in a short time without evaporating the organic solvent from the cellulose acylate, thereby achieving high-speed casting. The means for cooling the space may be normal air, nitrogen, argon, helium or the like, and is not particularly limited.
In this case, the humidity is preferably 0 to 70% RH, and more preferably 0 to 50% RH.
Moreover, in this invention, the temperature of the support body of the casting part which casts a cellulose acylate solution is -50 degreeC-130 degreeC, Preferably it is -30 degreeC-25 degreeC. In order to keep the casting part at a temperature suitable for the present invention, it may be achieved by introducing a cooled gas into the casting part, or a cooling device may be arranged in the casting part to cool the space. Good. At this time, it is important to pay attention so that water does not adhere, and it can be carried out by a method such as using dry gas.

In the casting step, one type of cellulose acylate solution may be cast in a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and sequentially.
As a method of co-casting a plurality of cellulose acylate solutions of two or more layers, for example, each of solutions containing cellulose acylate is cast from a plurality of casting ports provided at intervals in the traveling direction of the support. (For example, a method described in JP-A-11-198285), a method for casting a cellulose acylate solution from two casting ports (a method described in JP-A-6-134933), a high viscosity cellulose Examples thereof include a method of wrapping a flow of an acylate solution with a low-viscosity cellulose acylate solution and simultaneously extruding the high- and low-viscosity cellulose acylate solution (a method described in JP-A-56-162617). The present invention is not limited to these.

The obtained film is peeled off from the support (band) and further dried. The drying temperature in the drying step is preferably 40 ° C to 250 ° C, particularly preferably 70 ° C to 180 ° C.
Further, in order to remove the residual solvent, it is preferably dried at 50 ° C. to 160 ° C. In that case, the residual solvent is preferably evaporated by drying with high-temperature air whose temperature is changed successively. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, the time from casting to stripping can be shortened. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and can be appropriately selected according to the type and combination of the solvents used. The residual solvent amount of the final finished film is preferably 2% by mass or less, and more preferably 0.4% by mass or less in order to obtain a film having good dimensional stability. The specific method of these drying processes may use, for example, any of the conventionally known methods and apparatuses described in the above-mentioned Technical Report of the Invention Association, and is not particularly limited.

The cellulose acylate film can achieve an improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs in a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the technical report of the Invention Association (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of cellulose acylate film.

  The alkali saponification treatment is also preferably performed by applying a saponification solution. Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, for example, the contents described in JP-A-2002-82226 and W002 / 46809 are exemplified.

  In order to achieve adhesion between the film, the functional layer and the emulsion layer, after surface activation treatment, a method of directly applying the functional layer on the cellulose acylate film to obtain adhesive force, There is a method in which an undercoat layer (adhesive layer) is provided after surface treatment or without surface treatment, and a functional layer is applied thereon. Details of these subbing layers are described on page 32 of the Japan Society for Invention and Innovation (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Inventions). Various functional layers of the cellulose acylate film of the present invention are also described in detail on pages 32 to 45 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is described in.

Next, the organic solvent for dissolving the cellulose acylate used in the present invention will be described.
As the solvent to be used, a lower aliphatic hydrocarbon chloride or a lower aliphatic alcohol is generally used. Examples of lower aliphatic hydrocarbon chlorides include methylene chloride. Examples of lower aliphatic alcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol and n-butanol. Examples of other solvents include acetone substantially free of halogenated hydrocarbons, ketones having 4 to 12 carbon atoms (for example, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone), carbon atoms 3-12 esters (eg ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate and 2-ethoxy-ethyl acetate), alcohols having 1 to 6 carbon atoms (eg Methanol, ethanol, propanol, isopropanol, 1-butanol, t-butanol, 2-methyl-2-butanol, 2-methoxyethanol, 2-butoxyethanol, etc.), ethers having 3 to 12 carbon atoms (for example, diisopropyl ether, dimethoxy) Cimethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenetole, etc.) and cyclic hydrocarbons having 5 to 8 carbon atoms (for example, cyclopentane, cyclohexane, cycloheptane, cyclooctane, etc.) Is mentioned.

Preferably, a mixed solvent of esters, ketones, and alcohols is used as the dope preparation solvent from the viewpoint of the solubility of cellulose acylate.
Examples of non-halogen organic solvent systems that do not contain a halogenated hydrocarbon such as methylene chloride include, for example, paragraph numbers [0021] to [0025] of JP-A No. 2002-146043 and paragraph numbers of JP-A No. 2002-146045. Examples of the solvent system described in [0016] to [0021] are given.

  The cellulose acylate in the present invention is preferably a solution in which 10 to 30% by mass is dissolved in an organic solvent. The method for preparing cellulose acylate at these concentrations may be carried out so as to have a predetermined concentration at the stage of dissolution, or it is prepared in advance as a low concentration solution (for example, 9 to 14% by mass) and then concentrated later. You may adjust to a predetermined high concentration solution by a process. In addition, a cellulose acylate solution having a high concentration may be added to the cellulose acylate solution at a predetermined low concentration by adding various additives, so that the cellulose acylate solution concentration in the present invention can be obtained by any method. There is no particular problem if it is implemented.

  Regarding the preparation of the cellulose acylate solution (dope) in the present invention, the dissolution method is not particularly limited, and may be a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. With respect to these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-95854 -45950, JP-A-2000-53784, JP-A-11-322946, JP-A-11-322947, JP-A-2-276830, JP-A-2000-273239, JP-A-11-71463. JP-A Nos. 04-259511, 2000-273184, 11-323017, and 11-302388 describe methods for preparing cellulose acylate solutions. The above-described method for dissolving cellulose acylate in an organic solvent is applicable to the present invention as long as it is within the range suitable for the present invention.

  These details are described in detail on pages 22 to 25 in the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society for Inventions), especially for non-chlorine solvent systems. Be implemented in a way that Further, the cellulose acylate dope solution in the present invention is usually subjected to solution concentration and filtration. Similarly, the dope solution of the Invention Association (Publication No. 2001-1745, published on March 15, 2001, Invention Association) 25 It is described in detail on the page. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

The cellulose acylate solution in the present invention preferably has a viscosity and a dynamic storage modulus within the range. 1 mL of the sample solution was measured with a rheometer (CLS 500) using Steel Cone (both manufactured by TA Instruments) having a diameter of 4 cm / 2 °. Measurement conditions were measured at Oscillation Step / Temperature Ramp by changing the range from 40 ° C to -10 ° C at 2 ° C / min, static non-Newtonian viscosity n ^* (Pa · sec) at 40 ° C and storage at -5 ° C The elastic modulus G ′ (Pa) was determined. The measurement was started after the sample solution was kept warm at the measurement start temperature until the liquid temperature became constant. In the present invention, the viscosity at 40 ° C. is 1 to 300 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is 10,000 to 1,000,000 Pa.

  The use of cellulose acylate in the present invention will be briefly described first. The optical film of the present invention is particularly useful for a polarizing plate protective film. When using as a polarizing plate protective film, the production method of a polarizing plate is not specifically limited, It can produce by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed.

Examples of the adhesive used for bonding the protective film-treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both sides of the polarizer, and further comprises 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. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, the polarizing plate protective film on the display side outermost surface of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and the like. Particularly preferred.

  The cellulose acylate film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation sheet for liquid crystal display devices. The cellulose acylate film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Charged TNS). Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed.

  In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose acylate film is effective in the liquid crystal display device in any display mode. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device. The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell. The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d) of the rod-like liquid crystalline molecules. Product (Δnd) is in the range of 300 to 1500 nm. The optical compensation sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316. The cellulose acylate film of the present invention is particularly advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell.

  The cellulose acylate film of the present invention is also advantageously used as an optical compensation sheet for TN-type, STN-type, HAN-type, and GH (Guest-Host) type reflective liquid crystal display devices. These display modes have been well known since ancient times. The TN type reflection type liquid crystal display device is described in JP-A-10-123478, WO98848320, and Japanese Patent No. 3022477. The optical compensation sheet used for the reflection type liquid crystal display device is described in WO00-65384. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell in an ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)).

The cellulose acylate film of the present invention is also useful as a support for silver halide photographic light-sensitive materials. The cellulose acylate film of the present invention can be used as a support for any silver halide photographic light-sensitive material for printing plate making, medical use, general photographic use and the like. Moreover, it is preferable that the film thickness is 30-250 micrometers. For such a silver halide photographic light-sensitive material, see T.W. H. James et. al. The Theory of the Photographic Process 4th edition (Macmillan Publishing Co., Inc. 1977).
The use of these detailed cellulose acylate films described above is described in detail on pages 45-59 in the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society for Invention). Has been.

[Optical functional layer]
In the cellulose acylate film of the present invention, an optical compensation layer, an optical anisotropic layer, an antireflection layer, a polarization separation layer, a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, an antistatic layer, an easy adhesion layer, an orientation An optical functional sheet provided with an optical functional layer such as a layer or a liquid crystal layer is preferably used. The details will be described below, but the present invention is not limited thereto.

(Optical compensation sheet)
An optical compensation sheet is shown as a specific example of the optical functional sheet of the present invention. The optical functional layer has an optical anisotropic layer (optical compensation layer) and an alignment layer.
The cellulose acylate film of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Bend), VA (Vertically Aligned Labeled), and ECB (Electrically Labeled Mode). It is optimally used as a base film for optical compensation sheets.

As an optical compensation sheet for the TN mode, Journal of the Japan Printing Society, Vol. 36, No. 3 (1999), p. 40 to 44, Monthly Display August (2002), p. 20 to 24, JP-A-4-229828, JP-A-6-75115. The optical compensation sheets described in JP-A-6-214116 and JP-A-8-50206 are preferably used in combination.
A preferable configuration of the optical compensation sheet for the TN mode has an alignment layer and an optically anisotropic layer in this order on the transparent polymer film. The optical compensation sheet may be used by being bonded to a polarizing plate via an adhesive, but SID'00 Dig. , P551 (2000), it is particularly preferable from the viewpoint of thinning that it is used as one of the protective films of the polarizer.

  The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, or formation of a layer having a microgroup. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. It is preferable that the absorption axis direction and the rubbing direction of the polarizer are substantially parallel. As the polymer used for the alignment layer, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in JP-A-9-152509, and the like can be preferably used. The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer preferably contains a liquid crystalline compound. The liquid crystal compound used in the present invention particularly preferably has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like the triphenylene derivative of D-1, and has a structure in which side chains extend radially therefrom. In order to impart stability over time, it is also preferable to further introduce a group that reacts with heat, light or the like. As the discotic liquid crystal used in the present invention, compounds described in JP-A-8-50206 are preferably used.

  The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented in a form that is nearly perpendicular to the plane on the opposite air side. doing. The discotic liquid crystal layer as a whole has a hybrid alignment, and this layer structure can realize a wide viewing angle of a TN mode TFT-LCD.

  The optically anisotropic layer is generally a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) dissolved in a solvent, coated on the alignment layer, dried, and then discotic nematic. After heating to the phase formation temperature, it is obtained by polymerization by irradiation with UV light or the like and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

In addition to the discotic compound added to the optically anisotropic layer, the compound has compatibility with the discotic compound and can give a preferable change in tilt angle to the liquid crystalline discotic compound or inhibit the alignment. Any compound can be used as long as it is not. Among these, additives for controlling the orientation on the air interface side such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), fluorine-containing triazine compounds are cellulose acetate, cellulose acetate pro Mention may be made of polymers such as pionate, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.
The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

  A preferred embodiment of the optical compensation sheet comprises a cellulose acylate film as a transparent substrate film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer. The optically anisotropic layer is crosslinked by UV light irradiation.

  In addition to the above, when the optical compensation sheet and the polarizing plate of the present invention are combined, for example, as described in JP-A-07-198942, the birefringence has an optical axis in the direction intersecting the plate surface. It is also preferable to laminate with a retardation plate exhibiting anisotropy, or to make the dimensional change rate of the protective film and the optically anisotropic layer substantially the same as described in JP-A-2002-258052. be able to. Further, as described in JP-A No. 2000-258632, the moisture content of the polarizing plate bonded to the optical compensation sheet is set to 2.4% or less, or as described in JP-A No. 2002-267839, It is also preferable to make the contact angle of the sheet surface with water 70 ° or less.

  The IPS mode liquid crystal cell optical compensation sheet is used for optical compensation of liquid crystal molecules aligned in parallel to the substrate surface and for improving the viewing angle characteristics of the orthogonal transmittance of the polarizing plate during black display without an electric field. In the IPS mode, black is displayed when no electric field is applied, and the transmission axes of the pair of upper and lower polarizing plates are orthogonal. However, when observed from an oblique direction, the crossing angle of the transmission axes is not 90 °, and leakage light is generated, resulting in a decrease in contrast. When the polarizing plate of the present invention is used in an IPS mode liquid crystal cell, the in-plane retardation as described in JP-A-10-54982 is close to 0 and the thickness direction is reduced in order to reduce leakage light. It is preferably used in combination with an optical compensation sheet having a phase difference.

  The optical compensation sheet for OCB mode liquid crystal cells is used to improve the viewing angle characteristics of black display by optically compensating the liquid crystal layer that is vertically aligned at the center of the liquid crystal layer by applying an electric field and tilted near the substrate interface. Is done. When the polarizing plate of the present invention is used in an OCB mode liquid crystal cell, it is preferably used in combination with an optical compensation sheet in which a discotic liquid crystalline compound as described in US Pat. No. 5,805,253 is hybrid-aligned.

  The VA mode liquid crystal cell optical compensation sheet improves the viewing angle characteristics of black display in a state where liquid crystal molecules are vertically aligned with respect to the substrate surface in the absence of an electric field. As such an optical compensation sheet, a film having a phase difference close to 0 and having a phase difference in the thickness direction as described in Japanese Patent No. 2866372, or a disk-shaped compound is a substrate. Like films that are arranged in parallel with each other, films with the same in-plane retardation value laminated so that the slow axes are orthogonal, and liquid crystal molecules to prevent the deterioration of the orthogonal transmittance in the oblique direction of the polarizing plate It is preferably used in combination with a laminate of films made of various rod-like compounds.

(Λ / 4 plate)
The cellulose acylate film of the present invention can be used as a base film for a λ / 4 plate, and this λ / 4 plate can be used as a circularly polarizing plate by laminating it with a polarizing plate. The circularly polarizing plate has a function of converting incident light into circularly polarized light, and is preferably used for a reflective liquid crystal display device, a transflective liquid crystal display device such as an ECB mode, or an organic EL element.

  In the circularly polarizing plate, the slow axis of the λ / 4 plate and the transmission axis of the polarizer can intersect at an arbitrary angle, but preferably intersect within a range of 45 ° ± 20 °. However, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may intersect within a range other than the above.

  When the λ / 4 plate is formed by laminating the λ / 4 plate and the λ / 2 plate, as described in Japanese Patent No. 3236304 and Japanese Patent Laid-Open No. 10-68816, the λ / 4 plate and The λ / 2 plate is preferably bonded so that the angle formed between the slow axis in the plane of the λ / 2 plate and the transmission axis of the polarizing plate is substantially 75 ° and 15 °.

(Anti-reflective film)
The cellulose acylate film of the present invention is optimally used as a base film for an antireflection film. As the antireflection film, either a film having a reflectance of about 1.5% simply by applying a single layer of a low refractive index material such as a fluorine-based polymer, or a film having a reflectance of 1% or less using multilayer interference of a thin film is used. it can. In the present invention, a structure in which a low refractive index layer and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a middle refractive index layer) is laminated on a transparent support is preferably used. The Also, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28, and Japanese Patent Application Laid-Open No. 2002-301783 can be preferably used.

The refractive index of each layer satisfies the following relationship.
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of transparent support> refractive index of low refractive index layer The refractive index of the low refractive index layer is 1.20 to 1.55, preferably 1.30 to 1.50. The low refractive index layer is preferably used as an outermost layer having scratch resistance and antifouling properties. In order to improve the scratch resistance, it is also preferable to impart slipperiness to the surface using a material containing a silicone group or fluorine.

Examples of the fluorine-containing compound include paragraphs [0018] to [0026] of JP-A-9-222503, paragraphs [0019] to [0030] of JP-A-11-38202, and JP-A-2001-40284. The compounds described in paragraph Nos. [0027] to [0028], JP-A 2000-284102 and the like can be preferably used.
The silicone-containing compound is preferably a compound having a polysiloxane structure, but reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane at both ends (Japanese Patent Laid-Open No. 11-258403), etc. An organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent may be cured by a condensation reaction in the presence of a catalyst (Japanese Patent Laid-Open No. 58-142958). JP, 58-147483, 58-147484, JP-A-9-157582, 11-106704, JP-A-2000-117902, 2001-48590, 2002-53804. Described compounds).
The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as fillers (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as additives other than the above. Inorganic compounds having a low refractive index, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820), silane coupling agents, slip agents, surfactants, and the like are preferably added. be able to.
The low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.), but is preferably formed by a coating method because it can be manufactured at low cost. . As the coating method, dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, and micro gravure can be preferably used.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

The medium refractive index layer and the high refractive index layer preferably have a constitution in which ultrafine particles of high refractive index having an average particle size of 100 nm or less are dispersed in a matrix material. The inorganic compound fine particles having a high refractive index include inorganic compounds having a refractive index of 1.65 or more, for example, oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and metal atoms thereof. A composite oxide or the like can be preferably used.
Such ultrafine particles may be obtained by treating the surface of the particles with a surface treatment agent (silane coupling agent, etc .: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds or (Organic metal coupling agent: JP 2001-310432 A), a core-shell structure having high refractive index particles as a core (JP 2001-166104 A, etc.), or a specific dispersant is used in combination (for example, No. 153703, Patent No. US62010858B1, Japanese Patent Application Laid-Open No. 2002-27776069, etc.).

As the matrix material, a conventionally known thermoplastic resin, curable resin film, or the like can be used. Or a curable film obtained from a metal alkoxide composition described in JP-A-2001-293818 can be used.
The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(Brightness enhancement film)
The cellulose acylate film of the present invention can be optimally used as a base film for a brightness enhancement film. The brightness enhancement film has a function of separating circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and reflects or backscatters one circularly polarized light or linearly polarized light to the backlight side. The re-reflected light from the backlight part partially changes its polarization state and partially transmits when it re-enters the brightness enhancement film and the polarizing plate. By repeating this process, the light utilization rate is improved. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection system and an anisotropic scattering system are known, and both can be combined with the polarizing plate of the present invention.

  In the anisotropic reflection method, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers and increasing the refractive index difference in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal systems (European Patent No. 606940A2, Japanese Patent Laid-Open No. Hei 8- No. 271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. )) Is preferably used in the present invention. For NIPOCS, see Nitto Giho, vol. 38, no. 1, may, 2000, pages 19 to 21 and the like.

Further, in the present invention, positive numbers described in the specifications of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226 and JP-A-9-274108 and 11-174231 are described. It is also preferable to use in combination with a brightness enhancement film of an anisotropic scattering system in which an intrinsic birefringent polymer and a negative intrinsic birefringent polymer are blended and uniaxially stretched. As the anisotropic scattering system brightness enhancement film, DRPF-H (manufactured by 3M) is preferable.
The polarizing plate and the brightness enhancement film of the present invention are preferably used as an integrated type in which one of the protective films of the polarizing plate and the protective film of the polarizing plate is bonded via an adhesive.

(Other optical functional sheets)
The cellulose acylate film of the present invention is an optical functional sheet provided with a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, a gas barrier layer, a sliding layer, an antistatic layer, an undercoat layer, a protective layer and the like. Ideal as a base film. These functional layers are preferably used in combination with each other or in the same layer as the above-described antireflection layer, optically anisotropic layer, or the like.

(Hard coat layer)
In order to impart mechanical strength such as scratch resistance, the hard coat layer is preferably an optical functional sheet provided on the surface of the cellulose acylate film. When the hard coat layer is applied to the above-mentioned antireflection film, it is particularly preferable to provide it between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of the curable compound by light and / or heat. The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound. As a specific constituent composition of the hard coat layer, for example, those described in JP-A Nos. 2002-144913, 2000-9908, and WO 0/46617 can be preferably used.
The film thickness of the hard coat layer is preferably 0.2 to 100 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

  As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group or a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferred examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol. Polyacrylates of polyols such as hexaacrylate; epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether; obtained by reaction of polyisocyanate and hydroxyl group-containing acrylate such as hydroxyethyl acrylate Examples of preferred compounds include urethane acrylates. Moreover, as a commercially available compound, EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (above, Daicel UCB Co., Ltd. product), UV -6300, UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.

  Preferred examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, glycerol triglycidyl ether as glycidyl ethers. Triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin, etc. Celoxide 2021P, Celoxide 2081, Epoxide GT-301, Epolide GT-401, EHPE3150CE (above, Oxetane, OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, manufactured by Toagosei Co., Ltd.), etc. Can be mentioned. In addition, a polymer of glycidyl (meth) acrylate or a copolymer of a monomer that can be copolymerized with glycidyl (meth) acrylate may be used for the hard coat layer.

  In the hard coat layer, oxide fine particles such as silicon, titanium, zirconium, and aluminum are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and reduce curling of the hard coat treated article in the present invention. It is also preferable to add crosslinked fine particles such as organic fine particles such as crosslinked particles such as polyethylene, polystyrene, poly (meth) acrylic acid esters, polydimethylsiloxane, crosslinked rubber fine particles such as SBR and NBR. These crosslinked fine particles preferably have an average particle size of 1 nm to 20000 nm. Further, the shape of the crosslinked fine particles can be used without any particular limitation, such as a spherical shape, a rod shape, a needle shape, or a plate shape. The addition amount of the fine particles is preferably 60% by volume or less, more preferably 40% by volume or less of the hard coat layer after curing.

  In the case of adding the inorganic fine particles described above, since the affinity with the binder polymer is generally poor, it contains a metal such as silicon, aluminum, titanium, etc., and an alkoxide group, carboxylic acid group, sulfonic acid group, phosphonic acid group, etc. It is also preferable to perform a surface treatment using a surface treatment agent having a functional group of

  The hard coat layer is preferably cured using heat or active energy rays. Among them, active energy rays such as radiation, gamma rays, alpha rays, electron rays, and ultraviolet rays are more preferred, and safety and productivity are improved. In view of the above, it is particularly preferable to use an electron beam or an ultraviolet ray. In the case of curing with heat, in consideration of the heat resistance of the plastic itself, the heating temperature is preferably 140 ° C. or lower, more preferably 100 ° C. or lower.

(Forward scattering layer)
The forward scattering layer is used to improve the viewing angle characteristics (hue and luminance distribution) in the vertical and horizontal directions when the polarizing plate of the present invention is applied to a liquid crystal display device. In the present invention, a configuration in which fine particles having different refractive indexes are dispersed in a binder is preferable. The construction of JP-A-200280975, Japanese Patent Application Laid-Open No. 2002-107512 in which the haze value is defined as 40% or more can be used. Further, in order to control the viewing angle characteristics of haze, the polarizing plate of the present invention is also preferably used in combination with “Lumisty” described in Sumitomo Chemical's technical report “Photofunctional Film” on pages 31-39. be able to.

(Anti-glare layer)
The antiglare (antiglare) layer is used to scatter reflected light and prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
The method for forming irregularities on the film surface is, for example, a method of forming irregularities on the film surface by adding fine particles (for example, JP-A-2000-271878), relatively large particles (particle size 0.05-2 μm) A small amount (0.1 to 50% by mass) of a surface uneven film (for example, JP-A 2000-281410, 2000-95893, 2001-100004, 2001-281407, etc.) And a method of physically transferring the concavo-convex shape onto the film surface (for example, as an embossing method described in JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401, etc.) Can be used.

(Polarizer)
The polarizing plate of the present invention comprises a polarizer and a protective film bonded to both sides thereof, and the cellulose acylate film of the present invention can be used as the protective film. Moreover, you may use the optical functional sheet which attached the optical functional layer to the cellulose acylate film as a protective film.

  The polarizer is preferably composed of polyvinyl alcohol (PVA) and a dichroic molecule. As described in JP-A-11-248937, a polyene structure is formed by dehydrating and dechlorinating PVA and polyvinyl chloride. In addition, a polyvinylene polarizer having this oriented can also be used.

  PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.

The saponification degree of PVA is not particularly limited, but is preferably 80 to 100 mol%, particularly preferably 90 to 100 mol% from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494 is also preferably used. it can.

  After PVA is filmed, it is preferable to introduce a dichroic molecule to form a polarizer. As a method for producing a PVA film, a method of forming a film by casting a stock solution obtained by dissolving a PVA resin in water or an organic solvent is generally preferably used. The concentration of the polyvinyl alcohol-based resin in the stock solution is usually 5 to 20% by mass, and a PVA film having a thickness of 10 to 200 μm can be produced by forming a film of this stock solution by a casting method. The PVA film can be produced with reference to Japanese Patent No. 3342516, Japanese Patent Application Laid-Open No. 09-328593, Japanese Patent Application Laid-Open No. 2001-302817, and Japanese Patent Application Laid-Open No. 2002-144401.

The crystallinity of the PVA film is not particularly limited. However, in order to reduce the average crystallinity (Xc) of 50 to 75% by weight and the in-plane hue variation described in Japanese Patent No. 3251073, Japanese Patent Application Laid-Open Publication No. 2002-201013. PVA film having a crystallinity of 38% or less described in 236214 can be used.
The birefringence (Δn) of the PVA film is preferably small, and a PVA film having a birefringence of 1.0 × 10 ⁻³ or less described in Japanese Patent No. 3342516 can be preferably used. However, as described in JP-A-2002-228835, the birefringence of the PVA film may be set to 0.02 or more and 0.01 or less in order to obtain a high degree of polarization while avoiding cutting at the time of stretching the PVA film. Then, as described in JP-A-2002-060505, the value of (nx + ny) / 2-nz may be set to 0.0003 or more and 0.01 or less. The retardation (in-plane) of the PVA film is preferably from 0 nm to 100 nm, and more preferably from 0 nm to 50 nm. The Rth (film thickness direction) of the PVA film is preferably 0 nm or more and 500 nm or less, and more preferably 0 nm or more and 300 nm or less.

In addition, the polarizing plate of the present invention includes a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less as described in Japanese Patent No. 3021494, or 5 μm or more as described in JP-A No. 2001-316492. PVA film having 500 or less optical foreign matters per 100 cm ² , PVA film having a hot water cutting temperature spot in the TD direction described in JP-A-2002-030163 of 1.5 ° C. or less, and glycerin, etc. A PVA film formed from a solution containing 1 to 100 parts by weight of a 3-6 valent polyhydric alcohol or a mixture of 15% by weight or more of a plasticizer described in JP-A-06-289225 can be preferably used. .

  The film thickness before stretching of the PVA film is not particularly limited, but 1 μm to 1 mm is preferable and 20 to 200 μm is particularly preferable from the viewpoint of film holding stability and stretching uniformity. As described in JP-A-2002-236212, a thin PVA film may be used in which the stress generated when stretching 4 to 6 times in water is 10 N or less.

Dichroic molecule I ₃ ^- or I ₅ ^- can be preferably used an iodine ion or a dichroic dye higher such. In the present invention, higher-order iodine ions are particularly preferably used. Higher-order iodine ions were dissolved in an aqueous potassium iodide solution as described in “Application of Polarizing Plate” by Nagata Ryo, CMC Publishing, Industrial Materials, Vol. 28, No. 7, p39-p45. PVA can be dipped in a liquid and / or boric acid aqueous solution and adsorbed and oriented in PVA.
When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and a bisazo dye and a trisazo dye are particularly preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt.

Specific examples of such dichroic dyes include C.I. I. Direct Red 37, Congo Red (C.I. Direct Red 28), C.I. I. Direct Violet 12, C.I. I. Direct Blue 90, C.I. I. Direct Blue 22, C.I. I. Direct Blue 1, C.I. I. Direct Blue 151, C.I. I. Benzidines such as Direct Green 1, C.I. I. Direct Yellow 44, C.I. I. Direct Red 23, C.I. I. Diphenylurea series such as Direct Red 79, C.I. I. Stilbene series such as Direct Yellow 12, C.I. I. Dinaphthylamine series such as Direct Red 31, C.I. I. Direct Red 81, C.I. I. Direct Violet 9, C.I. I. Mention may be made of J acid series such as Direct Blue 78.
Further, JP-A-62-70802, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105, JP-A-1-265205. Further, dichroic dyes described in JP-A-7-261024 and the like can also be preferably used. In order to produce dichroic molecules having various hues, two or more of these dichroic dyes may be blended. When a dichroic dye is used, the adsorption thickness may be 4 μm or more as described in JP-A-2002-082222.

  If the content of the dichroic molecule in the film is too small, the degree of polarization is low, and if the content is too large, the single-plate transmittance is lowered. Therefore, the polyvinyl alcohol polymer constituting the film matrix is usually used. On the other hand, it is adjusted to a range of 0.01% by mass to 5% by mass.

  A preferable film thickness of the polarizer is preferably 5 μm to 40 μm, and more preferably 10 μm to 30 μm. The ratio between the thickness of the polarizer and the thickness of the protective film described later is in the range of 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0.16 described in JP-A-2002-174727. It is also preferable that

[Polarizing plate manufacturing process]
Next, the manufacturing process of the polarizing plate of this invention is demonstrated.
The manufacturing process of the polarizing plate in the present invention is preferably composed of a swelling process, a dyeing process, a hardening process, a stretching process, a drying process, a protective film bonding process, and a post-bonding drying process. The order of the dyeing step, the hardening step, and the stretching step may be arbitrarily changed, or several steps may be combined and performed simultaneously. Further, as described in Japanese Patent No. 3331615, washing with water after the hardening step can be preferably performed.

  In the present invention, it is particularly preferable to sequentially perform the swelling process, the dyeing process, the hardening process, the stretching process, the drying process, the protective film bonding process, and the drying process after bonding in the order described. An on-line surface inspection step may be provided during or after the above-described steps.

The swelling process is preferably performed only with water, but as described in JP-A-10-153709, in order to stabilize optical performance and avoid wrinkling of the polarizing plate substrate in the production line, polarized light is used. It is also possible to manage the degree of swelling of the polarizing plate substrate by swelling the plate substrate with an aqueous boric acid solution.
Moreover, although the temperature and time of a swelling process can be defined arbitrarily, 10 to 60 degreeC and 5 to 2000 second are preferable.

For the dyeing step, the method described in JP-A-2002-86554 can be used. Further, as a dyeing method, not only immersion but any means such as application or spraying of iodine or a dye solution can be used. Further, as described in JP-A-2001-290025, a method of dyeing while stirring the concentration of iodine, dye bath temperature, draw ratio in the bath, and bath solution in the bath may be used.
When higher-order iodine ions are used as the dichroic molecule, in order to obtain a high-contrast polarizing plate, it is preferable to use a solution obtained by dissolving iodine in an aqueous potassium iodide solution in the dyeing step. In this case, iodine in the iodine-potassium iodide aqueous solution is preferably 0.05 to 20 g / l, potassium iodide is 3 to 200 g / l, and the weight ratio of iodine and potassium iodide is preferably 1 to 2000. The dyeing time is preferably 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, iodine is 0.5 to 2 g / l, potassium iodide is 30 to 120 g / l, the weight ratio of iodine and potassium iodide is 30 to 120, dyeing time is 30 to 600 seconds, and liquid temperature is 20-50 degreeC is good.
Further, as described in Japanese Patent No. 3145747, boron compounds such as boric acid and borax may be added to the dyeing solution.

In the hardening step, it is preferable to immerse in the crosslinking agent solution or apply the solution to contain the crosslinking agent. Further, as described in JP-A-11-52130, the hardening process can be performed in several steps.
As the cross-linking agent, those described in US Reissue Patent No. 232897 can be used, and as described in Japanese Patent No. 3357109, a polyhydric aldehyde may be used as a cross-linking agent in order to improve dimensional stability. However, boric acids are most preferably used.
When boric acid is used as the crosslinking agent used in the hardening step, metal ions may be added to the boric acid-potassium iodide aqueous solution. Zinc chloride is preferred as the metal ion, but as described in JP 2000-35512 A, zinc halides such as zinc iodide, zinc sulfates, zinc acetates and the like are used instead of zinc chloride. You can also.
In the present invention, it is preferable to prepare a boric acid-potassium iodide aqueous solution to which zinc chloride has been added, and to perform dura- tion by immersing the PVA film. Boric acid is preferably 1 to 100 g / l, potassium iodide is 1 to 120 g / l, zinc chloride is preferably 0.01 to 10 g / l, hardening time is preferably 10 to 1200 seconds, and liquid temperature is preferably 10 to 60 ° C. . More preferably, boric acid is 10 to 80 g / l, potassium iodide is 5 to 100 g / l, zinc chloride is 0.02 to 8 g / l, hardening time is 30 to 600 seconds, and liquid temperature is 20 to 20 g / l. 50 ° C is preferable.

  For the stretching step, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515, or a tenter method as described in JP-A-2002-86554 can be preferably used. A preferable draw ratio is 2 times or more and 12 times or less, and more preferably 3 times or more and 10 times or less. Further, the relationship between the draw ratio, the thickness of the original fabric and the thickness of the polarizer is described in JP-A-2002-040256 (polarizer thickness after protective film bonding / raw fabric thickness) × (total draw ratio)> 0.17 or the relationship between the width of the polarizer when leaving the final bath and the width of the polarizer when bonding the protective film is 0.80 ≦ (when bonding the protective film) described in JP-A-2002-040247 The width of the polarizer / the width of the polarizer when leaving the final bath) ≦ 0.95 can also be preferably performed.

  As the drying step, a method known in JP-A-2002-86554 can be used, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. Further, as described in Japanese Patent No. 3148513, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or as described in Japanese Patent Laid-Open Nos. 07-325215 and 07-325218. Aging in an atmosphere controlled in temperature and humidity can also be preferably performed.

The protective film laminating step is a step of laminating both surfaces of the above-described polarizer that has gone through the drying step with two protective films. A method of bonding with a pair of rolls is preferably used so that the adhesive liquid is supplied immediately before bonding and the polarizer and the protective film are overlapped. In addition, as described in JP-A-2001-296426 and JP-A-2002-86554, the moisture content of the polarizer at the time of bonding is adjusted in order to suppress the groove-like unevenness of the record due to the stretching of the polarizer. It is preferable to do. In the present invention, a moisture content of 0.1% to 30% is preferably used.
The adhesive between the polarizer and the protective film is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 5 μm after drying, and particularly preferably 0.05 to 3 μm.
Moreover, in order to improve the adhesive force of a polarizer and a protective film, it is preferable to perform adhesion after surface-treating the protective film to make it hydrophilic. The surface treatment method is not particularly limited, and a known method such as a saponification method using an alkaline solution or a corona treatment method can be used. Further, an easy-adhesion layer such as a gelatin undercoat layer may be provided after the surface treatment. As described in JP-A-2002-267839, the contact angle of the protective film surface with water is preferably 50 ° or less.

  The drying conditions after bonding are in accordance with the method described in JP-A-2002-86554, but the preferred temperature range is 30 ° C. to 100 ° C., and the preferred drying time is 30 seconds to 60 minutes. It is also preferable to perform aging in an atmosphere with temperature and humidity control as described in JP-A-07-325220.

The element content in the polarizer is as follows: iodine 0.1-3.0 g / m ² , boron 0.1-5.0 g / m ² , potassium 0.1-2.0 g / m ² , zinc 0-2. It is preferably 0 g / m ² . Further, the potassium content may be 0.2% by weight or less as described in JP-A No. 2001-166143, and the zinc content in the polarizer is 0 described in JP-A No. 2000-035512. It is good also as 0.04 weight%-0.5 weight%.

  As described in Japanese Patent No. 3323255, in order to increase the dimensional stability of the polarizing plate, an organic titanium compound and / or an organic zirconium compound is added and used in any of the dyeing process, stretching process and hardening process And at least 1 type of compound chosen from the organic titanium compound and the organic zirconium compound can also be contained. Further, a dichroic dye may be added to adjust the hue of the polarizing plate.

[Characteristics of polarizing plate]
(Transmittance and degree of polarization)
The preferable single plate transmittance of the polarizing plate of the present invention is 42.5% or more and 49.5% or less, more preferably 42.8% or more and 49.0% or less. A preferable range of the degree of polarization defined by the formula XII is 97% or more, more preferably 99% or more, still more preferably 99.900% or more and 99.999% or less, and particularly preferably 99.940% or more and 99.99% or less. 995% or less. A preferable range of the parallel transmittance is 36% or more and 42% or less, and a preferable range of the orthogonal transmittance is 0.001% or more and 0.05% or less. A preferable range of the dichroic ratio defined by the formula XIII is 48 or more and 1215 or less, and more preferably 53 or more and 525 or less.
The above-described transmittance is defined by Formula X based on JISZ8701.

ここで、Ｋは式XIで定義され、Ｓ（λ）、ｙ（λ）、τ（λ）は以下の通りである。

Here, K is defined by Formula XI, and S (λ), y (λ), and τ (λ) are as follows.

Ｓ（λ）：色の表示に用いる標準光の分光分布
ｙ（λ）：ＸＹＺ系における等色関数
τ（λ）：分光透過率

S (λ): spectral distribution of standard light used for color display y (λ): color matching function in XYZ system τ (λ): spectral transmittance

The iodine concentration and the single plate transmittance may be within the ranges described in JP-A-2002-258051. The parallel transmittance may be small in wavelength dependency as described in JP-A-2001-083328 and JP-A-2002-022950. The optical characteristics when the polarizing plates are arranged in crossed Nicols may be in the range described in Japanese Patent Laid-Open No. 2001-091736, and the relationship between parallel transmittance and orthogonal transmittance is described in Japanese Patent Laid-Open No. 2002-174728. It may be within the range.
As described in JP-A-2002-221618, the standard deviation of the parallel transmittance every 10 nm when the light wavelength is between 420 and 700 nm is 3 or less, and the light wavelength is between 420 and 700 nm. The minimum value of (parallel transmittance / orthogonal transmittance) every 10 nm may be 300 or more.
The parallel transmittance and the orthogonal transmittance at a wavelength of 440 nm of the polarizing plate, the parallel transmittance, the parallel transmittance and the orthogonal transmittance at a wavelength of 550 nm, and the parallel transmittance and the orthogonal transmittance at a wavelength of 610 nm are disclosed in JP2002-258042 and JP2002. The range described in -258043 can also be preferably performed.

(Hue)
The hue of the polarizing plate of the present invention is preferably evaluated using the lightness index L * and the chromaticness indices a * and b * in the L * a * b * color system recommended as the CIE uniform perceptual space.
L *, a *, b * are defined in the formula XIV using the above X, Y, Z.

ここでX_０、 Y_０、 Z_０は照明光源の三刺激値を表し、標準光Ｃの場合、X_０=９８．０７２、 Y_０=１００、 Z_０=１１８．２２５であり、標準光Ｄ_６５の場合、X_０=９５．０４５、 Y_０=１００、 Z_０=１０８．８９２である。

Here, X ₀ , Y ₀ and Z ₀ represent the tristimulus values of the illumination light source. In the case of the standard light C, X ₀ = 98.072, Y ₀ = 100, Z ₀ = 118.225, and the standard light D _In the case of ₆₅ , X ₀ = 95.045, Y ₀ = 100, and Z ₀ = 108.892.

  The preferable range of a * for a single polarizing plate is −2.5 or more and 0.2 or less, and more preferably −2.0 or more and 0 or less. A preferable range of b * of the single polarizing plate is 1.5 or more and 5 or less, and more preferably 2 or more and 4.5 or less. The preferable range of a * of the parallel transmitted light of the two polarizing plates is −4.0 to 0, and more preferably −3.5 to −0.5. The preferred range of b * of the parallel transmitted light of the two polarizing plates is 2.0 or more and 8 or less, more preferably 2.5 or more and 7 or less. The preferable range of a * of the orthogonally transmitted light of the two polarizing plates is −0.5 or more and 1.0 or less, and more preferably 0 or more and 2 or less. The preferable range of b * of the orthogonally transmitted light of the two polarizing plates is −2.0 or more and 2 or less, and more preferably −1.5 or more and 0.5 or less.

The hue may be evaluated by the chromaticity coordinates (x, y) calculated from the aforementioned X, Y, and Z. For example, the chromaticity (x _p , y _p ) of the parallel transmitted light of the two polarizing plates And the chromaticity (x _c , y _c ) of the orthogonal transmitted light are within the ranges described in JP-A-2002-214436, JP-A-2001-166136, and JP-A-2002-169024, and the relationship between hue and absorbance is disclosed in JP It can also be preferably performed within the range described in 2001-311827.

(Viewing angle characteristics)
In the case where the polarizing plate is arranged in crossed Nicol and light with a wavelength of 550 nm is incident, when the vertical light is incident, the light is incident at an angle of 40 degrees with respect to the normal from the direction of 45 degrees with respect to the polarization axis. In this case, it is also preferable that the transmittance ratio and the xy chromaticity difference are within the ranges described in JP-A Nos. 2001-166135 and 2001-166137. Further, as described in JP-A-10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminate having the crossed Nicols arrangement and the light transmission in the direction inclined by 60 ° from the normal line of the laminate. The ratio (T ₆₀ / T ₀ ) to the rate (T ₆₀ ) is 10,000 or less, or as described in JP-A-2002-139625, natural light at an arbitrary angle from the normal to an elevation angle of 80 degrees On the film, the difference in transmittance of transmitted light within a wavelength range of 20 nm within the wavelength range of 520 to 640 nm of the transmission spectrum is set to 6% or less, or as described in JP-A-08-248201. It is also preferable that the brightness difference of transmitted light at an arbitrary 1 cm distance is within 30%.

(Damp heat durability)
As described in JP-A No. 2001-116922, the light transmittance and the rate of change in the degree of polarization before and after leaving in an atmosphere of 60 ° C. and 90% RH for 500 hours are 3% or less based on absolute values. It is preferable. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value. Further, as described in JP-A-07-0777608, it is also preferred that the degree of polarization after standing at 80 ° C. and 90% RH for 500 hours is 95% or more and the single transmittance is 38% or more.

(Dry durability)
It is preferable that the light transmittance and the rate of change of the degree of polarization before and after standing in a dry atmosphere at 80 ° C. for 500 hours are also 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value.

(Other durability)
Further, as described in JP-A-06-167611, 69 is a polarizing plate laminate in which the shrinkage ratio after being allowed to stand at 80 ° C. for 2 hours is 0.5% or less, or crossed Nicols are arranged on both surfaces of a glass plate. The x and y values after leaving for 750 hours in an atmosphere at ℃ are within the range described in JP-A-10-068818, or Raman after being left for 200 hours in an atmosphere at 80 ° C. and 90% RH the change in spectral intensity ratio of the 105 cm ^-1 and 157cm ^-1 due spectroscopy, can be preferably in the range described in JP-a-08-094834 and JP-a-09-197127.

(Degree of orientation)
The higher the degree of orientation of PVA, the better the polarization performance. However, the order parameter value calculated by means such as polarized Raman scattering or polarized FT-IR is preferably 0.2 to 1.0. Further, as described in JP-A-59-133509, in the entire amorphous region of the polarizer, the difference between the orientation coefficient of the polymer segment and the orientation coefficient of the occupied molecule (0.75 or more) is at least 0. .15, as described in JP-A No. 04-204907, the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85, and the orientation of higher-order iodine ions of I ₃ and I ₅ It is also preferable to set the degree to 0.8 to 1.0 as an order parameter value.

(Other characteristics)
As described in JP-A-2002-006133, the contraction force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is 4.0 N / cm or less, or described in JP-A-2002-236213. As shown in the figure, when the polarizing plate is placed under heating at 70 ° C. for 120 hours, both the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarization axis direction of the polarizing plate are both within ± 0.6%. The moisture content of the polarizing plate can be preferably adjusted to 3% by weight or less as described in JP-A-2002-090546. Further, as described in JP-A-2000-249832, the surface roughness in the direction perpendicular to the stretching axis is 0.04 μm or less based on the centerline average roughness, or described in JP-A-10-268294. The refractive index n ₀ in the transmission axis direction is preferably made larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film is preferably set in the range described in JP-A-10-111411. Can do.

[Liquid Crystal Display]
Next, a liquid crystal display device to which the polarizing plate of the present invention is applied will be described.
FIG. 2 is an example of a liquid crystal display device in which the polarizing plate of the present invention is used.

  The liquid crystal display device shown in FIG. 2 includes a liquid crystal cell (105 to 109), and an upper polarizing plate (101) and a lower polarizing plate (112) that are disposed with the liquid crystal cell (105 to 109) interposed therebetween. The polarizing plate is sandwiched between a polarizer and a pair of transparent protective films. In FIG. 2, the polarizing plate is shown as an integrated polarizing plate, and the detailed structure is omitted. The liquid crystal cell includes a liquid crystal cell upper substrate (105), a liquid crystal cell lower substrate (108), and a liquid crystal layer formed of liquid crystal molecules (107) sandwiched between them. The liquid crystal cell is different in the alignment state of liquid crystal molecules that perform ON / OFF display. Aligned), HAN (Hybrid Aligned Nematic), ECB (Electrically Controlled Birefringence), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric ALiS) It is. In addition, a display mode (MVA) in which the above display mode is orientation-divided has been proposed. The present invention is effective in a liquid crystal display device in any display mode. Further, it can be used in any of transmissive, reflective, and transflective liquid crystal display devices.

  An alignment film (not shown) is formed on the surface (hereinafter also referred to as “inner surface”) of the substrates (105) and (108) that contacts the liquid crystal molecules (107). The orientation of the liquid crystal molecules (107) in a state where no electric field is applied or a state where a low voltage is applied is controlled by rubbing treatment or the like. Further, on the inner surfaces of the substrates (105) and (108), a transparent electrode (not shown) capable of applying an electric field to the liquid crystal layer made of the liquid crystal molecules (107) is formed.

The rubbing direction of the TN mode is applied in directions perpendicular to each other on the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle (twist angle) of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm was added so that the twist angle was 90 °.
The twist angle is in the vicinity of 90 ° (85 to 95 °) in the case of a notebook computer, a personal computer monitor, and a liquid crystal display device for a television, and is 0 to 70 ° in the case of use as a reflective display device such as a mobile phone. Set. In the IPS mode and the ECB mode, the twist angle is 0 °. In the IPS mode, electrodes are disposed only on the lower substrate (108) of the liquid crystal cell, and an electric field parallel to the substrate surface is applied. In the OCB mode, there is no twist angle and the tilt angle is increased, and in the VA mode, the liquid crystal molecules (107) are aligned perpendicular to the upper and lower substrates.

Here, the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn changes the brightness during white display. Therefore, in order to obtain the maximum brightness, the range is set for each display mode.
In general, the crossing angle between the absorption axis (102) of the upper polarizing plate (101) and the absorption axis (113) of the lower polarizing plate (112) is generally perpendicular to obtain a high contrast. The crossing angle between the absorption axis (102) of the upper polarizing plate (101) of the liquid crystal cell and the rubbing direction of the upper substrate (105) depends on the liquid crystal display mode, but is generally set to be parallel or vertical in the TN and IPS modes. In OCB and ECB modes, it is often set to 45 °. However, the optimum value differs in each display mode for adjusting the color tone and viewing angle of the display color, and the present invention is not limited to this range.

The liquid crystal display device in which the polarizing plate of the present invention is used is not limited to the configuration of FIG. 2, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizer. In addition, the above-described viewing angle widening film (also referred to as an optically anisotropic layer) (103, 110) can be separately disposed between the liquid crystal cell and the polarizing plate. The polarizing plate (101, 112) and the viewing angle widening film (103, 110) may be arranged in a laminated form bonded with an adhesive, or one of the liquid crystal cell side protective films is used for widening the viewing angle. You may arrange | position as an integrated elliptical polarizing plate.
When used as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight having a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. In addition, the liquid crystal display device in which the polarizing plate of the present invention is used may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back of the liquid crystal cell or under the liquid crystal cell. A reflective film is installed on the inner surface of the side substrate. Of course, a front light using the light source may be provided on the liquid crystal cell observation side.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Example 1]
<Manufacture of cellulose acetate propionate film>
(Preparation of cellulose acetate propionate (AP-1))
120 parts by weight of acetic acid and 74 parts by weight of propionic acid were placed in a control container and adjusted to 20 ° C. After adding 81 parts by weight of cellulose and partially swelling at 20 ° C. for 10 minutes, the mixture was cooled to −10 ° C., and then a solution prepared by mixing 122 parts by weight of acetic anhydride and 9.8 parts by weight of sulfuric acid was gradually cooled to −20 ° C. To the first stage of acetylation. The system was cooled so that the temperature did not exceed 30 ° C., and reacted for 80 minutes. At the end of the reaction, about 20% by mass of undissolved cellulose remained in the reaction system.
Next, 390 parts by weight of propionic anhydride and 148 parts by weight of propionic acid were added to carry out second-stage propionylation. The maximum temperature in acylation is adjusted to 40 ° C., and the acylation reaction is carried out for 80 minutes. Then, a mixed solution of 300 parts by weight of acetic acid and 90 parts by weight of water is added as a reaction terminator over 20 minutes. Was hydrolyzed. The temperature of the reaction solution was kept at 50 ° C., and 900 parts by weight of acetic acid and 270 parts by weight of water were added. After 60 minutes, an aqueous solution containing 16 parts by weight of magnesium acetate was added to neutralize sulfuric acid in the system. The obtained cellulose acetate propionate had an acetyl substitution degree of 2.19, a propionyl substitution degree of 0.70, a weight average polymerization degree of 500, and a number average molecular weight of 80600.

(Preparation of cellulose acetate propionate dope)
To a stainless steel dissolution tank having a stirring blade, the solvent, additive and fine particles of the following formulation are added and mixed, and the prepared cellulose acetate propionate powder (average size 2 mm) is gradually added while stirring well, After being left at (25 ° C.) for 1 hour, the cellulose acetate propionate was swollen by maintaining at 35 ° C. In addition, methyl acetate, methyl ethyl ketone, methanol, ethanol, and n-butanol, which are solvents, all used had a water content of 0.2% by mass or less.
The component ratio (dope formulation) of each component used for the preparation of the dope is shown below.

―――――――――――――――――――――――――――――――――――――――
Dope prescription (D-1)
―――――――――――――――――――――――――――――――――――――――
Cellulose acetate propionate thus prepared (substitution degree 2.89, substitution degree 0.93 at the 6-position, substitution degree 1.90 at the 2,3-position, viscosity average polymerization degree 500, water content 0.8. 4 mass%, 6 mass% viscosity in methylene chloride solution 305 mPa · s)
18 parts by weight Methyl acetate 56 parts by weight Methyl ethyl ketone 10 parts by weight Methanol 5 parts by weight Ethanol 5 parts by weight n-butanol 5 parts by weight Plasticizer A (dipentaerythritol hexaacetate) 1 part by weight Fine particles (silica (particle size 20 nm)) 0. 1 part by mass The following UV absorber (1) 0.15 parts by mass ――――――――――――――――――――――――――――――――― ―――――

  Next, the dope was defoamed by irradiating weak ultrasonic waves. The defoamed dope was first passed through a sintered metal filter having a nominal pore diameter of 5 μm while being pressurized to 1.5 MPa, and then passed through a sintered metal filter of 2.5 μm. Respective primary pressures were 1.5 and 1.2 MPa, and secondary pressures were 1.0 and 0.8 MPa, respectively. The dope temperature after filtration was adjusted to 35 ° C. and stored in a stainless steel stock tank. The center axis of the stock tank was provided with an anchor blade and stirred constantly at a peripheral speed of 0.3 m / sec.

(Cellulose acetate propionate film formation)
The dope obtained by the above-described dissolution method was set to 40 ° C., and cast on a mirror surface stainless steel support having a surface temperature of 20 ° C. through a casting Giesser to form a film.
The dope cast on the band was first dried by sending parallel-flow drying air. The overall heat transfer coefficient from the drying air to the dope during drying was 24 kcal / m ² · hr · ° C. The temperature of the drying air was 140 ° C. at the upper part of the band and 100 ° C. at the lower part.
For 5 seconds after casting, the wind is prevented from directly hitting the dope by the wind shield device, and after that, it is peeled off from the support, stretched in the direction perpendicular to the casting direction, and further a drying zone having a large number of rolls. A cellulose acetate propionate film having a thickness of 60 μm was produced by stretching while being conveyed.

[Example 2]
<Manufacture of cellulose acetate butyrate film>
(Preparation of cellulose acetate butyrate (AB-1))
The acetic acid 120 weight part and the butyric acid 130 weight part were put into the adjustment container, and it adjusted to 20 degreeC. After adding 81 parts by weight of cellulose and partially swelling at 20 ° C. for 10 minutes, the mixture was cooled to −10 ° C., and then a solution containing 122 parts by weight of acetic anhydride cooled to −15 ° C. and 9.8 parts by weight of sulfuric acid was gradually added. To the first stage of acetylation. The system was cooled so that the temperature did not exceed 35 ° C., and reacted for 80 minutes. At the end of the reaction, about 25% of undissolved cellulose remained in the reaction system.
Next, 620 parts by weight of butyric anhydride and 176 parts by weight of butyric acid were added to carry out second-stage butyrylation. The maximum temperature in acylation is adjusted to 40 ° C., and the acylation reaction is carried out for 80 minutes. Then, a mixed solution of 300 parts by weight of acetic acid and 90 parts by weight of water is added as a reaction terminator over 20 minutes. Was hydrolyzed. The temperature of the reaction solution was kept at 50 ° C., and 900 parts by weight of acetic acid and 270 parts by weight of water were added. After 60 minutes, an aqueous solution containing 16 parts by weight of magnesium acetate was added to neutralize sulfuric acid in the system. The obtained cellulose acetate butyrate had an acetyl substitution degree of 2.21, a butyryl substitution degree of 0.67, a weight average polymerization degree of 490, and a number average molecular weight of 81300.
The cellulose acetate butyrate dope solution (D-2) was prepared in the same manner as in Example 1 except that the same amount of cellulose acylate was used, and the film thickness after drying the cellulose acetate butyrate film was 60 μm. It produced as follows.

Example 3
<Production of cellulose acetate propionate butyrate film>
(Preparation of cellulose acetate propionate butyrate (APB-1))
120 parts by weight of acetic acid, 44 parts by weight of propionic acid and 70 parts by weight of butyric acid were placed in a control container and adjusted to 20 ° C. After adding 81 parts by weight of cellulose and partially swelling at 20 ° C. for 10 minutes, the mixture was cooled to −10 ° C., then 122 parts by weight of acetic anhydride cooled to −20 ° C., 4 parts by weight of propionic anhydride, 9.8 parts by weight of sulfuric acid. The solution in which the parts were mixed was gradually added to perform first-stage acetylpropionylation. The system was cooled so that the temperature did not exceed 35 ° C., and reacted for 80 minutes. At the end of the reaction, about 25% of undissolved cellulose remained in the reaction system.
Next, 230 parts by weight of propionic anhydride, 89 parts by weight of propionic acid, 316 parts by weight of butyric anhydride, and 92 parts by weight of butyric acid were added to carry out second-stage propionylbutyrylation. The maximum temperature in acylation is adjusted to 40 ° C., and the acylation reaction is carried out for 80 minutes. Then, a mixed solution of 300 parts by weight of acetic acid and 90 parts by weight of water is added as a reaction terminator over 20 minutes. Was hydrolyzed. The temperature of the reaction solution was kept at 50 ° C., and 900 parts by weight of acetic acid and 270 parts by weight of water were added. After 60 minutes, an aqueous solution containing 16 parts by weight of magnesium acetate was added to neutralize sulfuric acid in the system. The obtained cellulose acetate propionate butyrate had an acetyl substitution degree of 2.19, a propionyl substitution degree of 0.35, a butyryl substitution degree of 0.33, a weight average polymerization degree of 470, and a number average molecular weight of 76700. .
The cellulose acetate butyrate dope solution (D-3) was prepared in the same manner as in Example 1 except that this cellulose acylate was used in the same amount, and the film thickness after drying the cellulose acetate propionate butyrate film was It produced so that it might become 60 micrometers.

[Comparative Example 1]
270 parts by weight of acetic acid and 333 parts by weight of propionic acid were placed in an adjustment container and adjusted to 40 ° C. After adding 81 parts by weight of cellulose and substantially dissolving at 40 ° C. for 30 minutes, the mixture was cooled to −10 ° C., then 122 parts by weight of acetic anhydride, 390 parts by weight of propionic anhydride, 9.8 parts by weight of sulfuric acid cooled to −10 ° C. Acetylpropionylation was carried out by gradually adding the mixed solution. The temperature of the system was 45 ° C. and the reaction was performed for 80 minutes. At the end of the reaction, the cellulose in the reaction system was completely dissolved.
Next, as a reaction terminator, a mixed solution of 300 parts by weight of acetic acid and 90 parts by weight of water was added over 20 minutes to hydrolyze excess anhydride. The temperature of the reaction solution was kept at 50 ° C., and 900 parts by weight of acetic acid and 270 parts by weight of water were added. After 60 minutes, an aqueous solution containing 16 parts by weight of magnesium acetate was added to neutralize sulfuric acid in the system. The obtained cellulose acetate propionate has an acetyl substitution degree of 2.18, a propionyl substitution degree of 0.72, a weight average polymerization degree of 510, a number average molecular weight of 82400, and an acetyl substituent and a propionyl substituent are random. The cellulose acylate distributed in
A cellulose acetate propionate dope solution (D-R1) was prepared in the same manner as in Example 1 except that the same amount of cellulose acylate was used, and the film thickness after drying the cellulose acetate propionate film was 60 μm. It produced so that it might become.

[Comparative Example 2]
<Manufacture of cellulose acetate film>
120 parts by weight of acetic acid and 74 parts by weight of propionic acid were placed in a control container and adjusted to 20 ° C. After adding 81 parts by weight of cellulose and partially swelling at 20 ° C. for 10 minutes, the mixture was cooled to −10 ° C., and then a solution prepared by mixing 122 parts by weight of acetic anhydride and 9.8 parts by weight of sulfuric acid was gradually cooled to −25 ° C. To the first stage of acetylation. The system was cooled so that the temperature did not exceed 30 ° C., and reacted for 80 minutes. At the end of the reaction, about 20% of undissolved cellulose remained in the reaction system.
Next, 510 parts by weight of acetic anhydride was added to perform the second stage acetylation. The maximum temperature in acylation is adjusted to 40 ° C., and the acylation reaction is carried out for 80 minutes. Then, a mixed solution of 300 parts by weight of acetic acid and 90 parts by weight of water is added as a reaction terminator over 20 minutes. Was hydrolyzed. The temperature of the reaction solution was kept at 50 ° C., and 900 parts by weight of acetic acid and 270 parts by weight of water were added. After 60 minutes, an aqueous solution containing 16 parts by weight of magnesium acetate was added to neutralize sulfuric acid in the system. The obtained cellulose acetate was a cellulose acetate having an acetyl substitution degree of 2.85 and a propionyl substitution degree of 0.00.
Its weight average degree of polymerization is 500, number average molecular weight is 77600,
The cellulose acylate dope solution (D-R2) was prepared in the same manner as in Example 1 except that the same amount of cellulose acylate was used, so that the film thickness after drying the cellulose acylate film was 60 μm. Produced.

<Result>
Table 1 shows the performance of the cellulose acylate films obtained in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 obtained above.

The evaluation method of the evaluation item of Table 1 was implemented as follows.
(1) Optical properties (retardation) of cellulose acylate film
About the produced cellulose acylate film, using an ellipsometer (M-150, manufactured by JASCO Corporation), the Re retardation (Re) value and the Rth retardation (Rth) value at a wavelength of 633 nm under 30 ° C. and 50% RH. Was measured.
Humidity dependence was calculated from measured values of different humidity at the same temperature, with the Re value and Rth value at a wavelength of 633 nm under 50% RH as reference values at each temperature. On the other hand, the temperature dependence was similarly calculated from the measured values at the same humidity and different temperatures using the value at 30 ° C. as the reference value.
Also, the Re ₍₄₃₀₎ value and the Rth ₍₄₃₀₎ value at a wavelength of 430 nm are measured, and the deviation of Re and Rth depending on the wavelength ΔRe = | Re−Re ₍₄₃₀₎ | and ΔRth = | Rth−Rth ₍₄₃₀₎ | Calculated.

(2) Tensile modulus and elongation at break The tensile modulus and elongation at break of the produced cellulose acylate film were measured using a Toyo Baldwin Universal Tensile Tester STM T50BP in a 25 ° C, 60% atmosphere and a tensile rate of 10%. The tensile modulus was determined from the stress at 0.5% elongation per minute, and the elongation at break was determined from the breaking point of the cellulose acylate film.

(3) Sound wave propagation velocity The sound wave propagation velocity of the produced cellulose acylate film was determined by a sound wave meter (SST-110 manufactured by Nomura Shoji Co., Ltd.).

(4) Moisture permeability The moisture permeability of the produced cellulose acylate film was adjusted based on JIS standard JIS Z0208 conditions for a film sample 70 mmφ at 40 ° C. and 90% RH for 24 hours. 709007, Toyo Seiki Co., Ltd.) to calculate the water content per unit area (g / m ² ). The 80 μm film thickness converted moisture permeability was converted by the following formula.
80 μm film thickness converted moisture permeability = (actually measured moisture permeability) × (actually measured film thickness (μm) / 80 (μm))

(5) Thermal expansion coefficient The thermal expansion coefficient of the produced cellulose acylate film was determined as follows using a thermomechanical measurement method (TMA).
The sample after humidity adjustment at 25 ° C. and 60% RH is cut into a width of 4 mm, set so that the distance between chucks is 25 mm, and then a load is applied based on the following formula.
Load (g) = {sample thickness (μm) / 100} × 6
The temperature was raised from 25 ° C. to 40 ° C. at 2 ° C./min, the amount of dimensional change (ΔL) was read, and the temperature expansion coefficient was determined according to the following formula.
Thermal expansion coefficient (/ ° C.) = ΔL (mm) / {25 (mm) × 15 (° C.)}

(6) Photoelastic coefficient The photoelastic coefficient of the prepared cellulose acylate film was determined by applying tensile stress to the long axis direction of the film sample 12 mm × 120 mm, and the retardation at that time was determined by ellipsometer (M150, JASCO Corporation) )), And the photoelastic coefficient was calculated from the amount of change in retardation with respect to stress.

(7) Dimensional change The dimensional stability of the prepared cellulose acylate film was measured by preparing two cellulose acylate film samples 30mm x 120mm, humidity-controlled at 25 ° C and 60% RH for 24 hours, and automatic pin gauge. (Shinto Kagaku Co., Ltd.) made 6 mmφ holes at both ends at an interval of 100 mm to obtain the original punch spacing (L0). Punch interval size (L1) after one sample was treated at 60 ° C. and 90% RH for 24 hours, punch after one sample was treated at 90 ° C. and 5% RH for 24 hours The distance dimension (L2) was measured. Measurement was made to a minimum scale of 1/1000 mm at all intervals. Dimensional change rate of 60 ° C. and 90% RH (high humidity) = {| L0−L1 | / L0} × 100, Dimensional change rate of 90 ° C. and 5% RH (high temperature) = {| L0−L2 | / The dimensional change rate was determined as L0} × 100.

(8) Degree of substitution of cellulose acylate 1.9 g of dried cellulose acylate was precisely weighed, and after adding 70 ml of acetone and 30 ml of dimethyl sulfoxide to dissolve, 50 ml of acetone was further added. While stirring, 30 ml of 1N sodium hydroxide aqueous solution was added and saponified for 2 hours. After adding 100 ml of hot water and washing the sides of the flask, titration with 1N sulfuric acid was performed using phenolphthalein as an indicator. Separately, a blank test was performed in the same manner as the sample. The supernatant of the solution after titration was diluted 100 times, and the composition of the organic acid was measured by an ordinary method using an ion chromatograph. From the measurement result and the acid composition analysis result by ion chromatography, the substitution degree was calculated by the following formula.
TA = (B−A) × F / (1000 × W)
DSace = (162.14 × TA) /
{1-42.14 × TA + (1−56.06 × TA) × (AL / AC)}
DSacy = Sace × (AL / AC)
A: Sample titration (ml)
B: Blank test titration (ml)
F: 1N-sulfuric acid titer W: Sample weight (g)
TA: Total organic acid amount (mol / g)
AL / AC: molar ratio of acetic acid (AC) and other organic acid (AL) measured by ion chromatography DSace: substitution degree of acetyl group DSacy: substitution degree of other acyl group

(9) Number average molecular weight of cellulose acylate The number average molecular weight was measured using a high performance liquid chromatography system (GPC-LALLS) in which a detector for detecting refractive index and light scattering was connected to a gel filtration column. The measurement conditions are as follows.
Solvent: Acetone column: MPW × 1 (manufactured by Tosoh Corporation)
Sample concentration: 0.2 W / v%
Flow rate: 1.0ml / min
Sample injection volume: 300 μl
Standard sample: polymethyl methacrylate (Mw = 188,200)
Temperature: 23 ° C

(10) Weight average polymerization degree of cellulose acylate The weight average molecular weight was measured under the same measurement conditions as in (9) above. From the weight average molecular weight and average substitution degree obtained from the measurement results, the weight average polymerization degree was determined by the following formula.
Weight average degree of polymerization = Mw / (162 + 42 × DSace + (Mal-18) × DSacy
Mw: Weight average molecular weight DSace: Degree of substitution of acetyl group DSacy: Degree of substitution of other acyl group Mal: Molecular weight of organic acid corresponding to other acyl substituent

The cellulose acylate film having a continuous portion of glucose units substituted with the acetyl substituent of Example 1, Example 2 and Example 3 has the Re value, Rth value, Re value and Rth value humidity dependency and wavelength dispersion ( Deviation) and appropriate optical anisotropy, and other optical properties (transparency, haze value, foreign matter / dirt, etc.) were also preferable. It can also be seen that the tensile modulus is high, the elongation at break is not too high, and the mechanical properties are excellent. Furthermore, it can be seen that the speed of sound wave propagation is high, and the microcrystal / orientation of the film is improved. It was confirmed that the thermal expansion coefficient and the dimensional change rate were small and excellent in mechanical characteristics, particularly thermal characteristics, and in addition, even a thin film showed good moisture permeability.
On the other hand, although the cellulose acetate propionate film of Comparative Example 1 has good Re and Rth characteristics, it is confirmed that the tensile modulus is low, the elongation at break is large, the mechanical characteristics are inferior, and the sound wave propagation speed is slow. Therefore, it can be seen that the film has poor crystallinity and orientation, thermal expansion coefficient and dimensional change rate are large, mechanical properties and thermal properties are insufficient, moisture permeability is large, optical functional sheet, polarizing plate and liquid crystal It was unbearable for practical use as a display device.
The cellulose acetate film of Comparative Example 2 is a cellulose acylate in which the second acylating agent is the same as the first acylating agent, in addition to mechanical properties such as tensile modulus and elongation at break, mechanical properties, thermal properties, Although it was excellent in moisture permeability, it was found that the Re and Rth characteristics were low and it did not have sufficient optical characteristics, and it was not practical for optical functional sheets, polarizing plates and liquid crystal display devices.
Further, the cellulose acylate films of Example 1 and Example 2 have performance superior to the cellulose acylate film of Example 3 in which the first and second stage acylating agents are not the same acylating agent. confirmed.

Example 4
In Example 1, the amount of undissolved cellulose after the first-stage acylation reaction was 20%, but the amount of undissolved cellulose was adjusted to 38%, 58%, 81% by adjusting the amount of acetic acid and propionic acid added. A cellulose acylate film was prepared. The undissolved cellulose content of 38% was as good as 58% in mechanical properties such as tensile elastic modulus and breaking strength, but was found to be slightly inferior to Example 1. In addition, it was confirmed that 81% had a tendency to be slightly inferior in mechanical properties and moisture permeability than 38% and 58%. However, these had better performance than Comparative Example 1.

Example 5
Japanese Unexamined Patent Publication No. 7-333433, except that the triacetyl cellulose film of Fuji Photo Film Co., Ltd. in Example 1 of JP-A-7-333433 is changed to the cellulose acetate propionate film of Example 1 of the present invention. An optical compensation sheet exactly the same as Example 1 was prepared. The obtained optical compensation sheet had an excellent viewing angle in the left, right, up and down directions. Therefore, it was found that the cellulose acetate propionate film of the present invention was excellent for optical use.

Example 6
The cellulose acylate film of the present invention is further used for various optical applications. Samples of Example 1 and Comparative Example 1 described above are described in Example 1 of JP-A-10-48420, a polarizing plate described in Example 1 of JP-A-10-48420, a liquid crystal display device using the same, and Example 1 of JP-A-9-26572. An optically anisotropic layer containing discotic liquid crystal molecules, an alignment film coated with polyvinyl alcohol, a VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, and a diagram of JP-A-2000-154261 When used in the OCB type liquid crystal display device described in 10 to 15, good performance was obtained using the cellulose acylate film of the present invention.
In particular, it was confirmed that in the display device using the cellulose acylate film of the present invention, light leakage during black display was all within 2%, which was 1/2 to 1/10 or less of the comparative example. The light leakage after 1000 hours at 50 ° C./80% RH was also good, and it was confirmed that the display device was excellent in flatness without floating of the polarizing plate.

  As described above, the cellulose acylate film having a continuous portion of glucose units substituted with an acetyl group in the present invention showed excellent performance as an optical functional sheet, a polarizing plate, and a liquid crystal display device.

It is the schematic of one Embodiment of the casting film forming line which enforces the casting film forming method by this invention. It is explanatory drawing which showed an example of the liquid crystal display device in which the polarizing plate of this invention is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Mixing tank 12 Liquid feed pump 13 Filter 14 Casting die 15 Casting band 16 Casting side part rotating drum 17 Non-casting part side rotating drum 18 Guide roll 19 Stripping roll 20 Guide roll 21 Winding roll 22 Drying part 23 Film 101 Upper polarizing plate 102 Upper polarizing plate absorption axis 103 Upper optical anisotropic layer 104 Upper optical anisotropic layer alignment control direction 105 Liquid crystal cell upper substrate 106 Upper substrate alignment control direction 107 Liquid crystal molecule 108 Liquid crystal cell lower substrate 109 Lower Substrate orientation control direction 110 Lower optical anisotropic layer 111 Lower optical anisotropic layer orientation control direction 112 Lower polarizing plate 113 Lower polarizing plate absorption axis

Claims (10)

  A method for producing cellulose acylate in which cellulose and an acylating agent are reacted in a solution, wherein 10% by mass to 90% by mass of input cellulose is in an undissolved state, dissolved cellulose and an undissolved but solution interface The first-stage acylation reaction is performed on the cellulose present in the water, the undissolved cellulose is then dissolved, and the second-stage acylation reaction is performed using an acylating agent different from the first-stage acylating agent. A method for producing cellulose acylate.   A method for producing cellulose acylate by reacting cellulose with an acylating agent, wherein the same acyl group is introduced into all three hydroxyl groups in a glucose unit by the first-stage acylating agent or the second-stage acylating agent. The method for producing a cellulose acylate according to claim 1.   A method for producing cellulose acylate in which cellulose and an acylating agent are reacted, wherein the first-stage acylating agent is an acetylating agent, and the second-stage acylating agent contains a propionylating agent or a butyrylating agent The method for producing a cellulose acylate according to claim 1 or 2, wherein:   A cellulose acylate film formed using the cellulose acylate produced by the production method according to claim 1. The Re value (unit: nm) and Rth value (unit: nm) of the cellulose acylate film defined by the formulas (I) and (II) measured at a wavelength of 633 nm satisfy the formulas (III) and (IV), respectively. In addition, the humidity dependence of the Re value and the Rth value in the range of 15 ° C. relative humidity of 15% to 30 ° C. relative humidity of 85% is 2% /% relative humidity or less and 3% /% relative humidity or less in absolute value. The cellulose acylate film according to claim 4.
(I) Re = (nx−ny) × d
(II) Rth = {(nx + ny) / 2−nz} × d
[Wherein nx is the refractive index in the slow axis direction in the cellulose acylate film surface; ny is the refractive index in the fast axis direction in the cellulose acylate film surface; nz is the cellulose acylate] The refractive index in the thickness direction of the film; and d is the thickness of the cellulose acylate film].
(III) 20 ≦ Re ≦ 100
(IV) 70 ≦ Rth ≦ 400 The direction of the maximum tensile modulus of the cellulose acylate film and the direction perpendicular thereto are 310 kg / mm ² or more and 250 kg / mm ² or more, respectively, and the film has a maximum elongation at break and a direction perpendicular thereto The values of are respectively 30% or less and 18% or less, The cellulose acylate film according to any one of claims 4 to 5.   The cellulose acylate film according to any one of claims 4 to 6, wherein the cellulose acylate film has a thickness of 5 to 500 µm.   The cellulose acylate film according to any one of claims 4 to 7 is provided with at least one layer selected from a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an optically anisotropic layer. An optical functional sheet characterized by the above.   A polarizing plate comprising the cellulose acylate film according to any one of claims 4 to 7 or the optical functional sheet according to claim 8 as a protective film for a polarizer.   A liquid crystal comprising at least one sheet of the cellulose acylate film according to any one of claims 4 to 7, the optical functional sheet according to claim 8, or the polarizing plate according to claim 9. Display device.

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