JP2010286603A - Optical compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an optical compensation film which is excellent in reworkability and is made of cellulose acylate free of adhesion of the films to each other. <P>SOLUTION: The optical compensation film 10 is made of cellulose acylate, wherein a plasticizing agent is unevenly distributed in the thickness direction so that the inner content is higher than those of the first and second surfaces 11a, 12a. The plasticizing agent is a polymer having a repeating unit containing an ester bond of carboxylic acid and diol. The optical compensation film has Re in the range of 0-100 nm and Rth in the range of 0-400 nm, for light of a wavelength of 550 nm. The surface energy of the optical compensation film 10 after saponification processing at a predetermined condition is in the range of 50-75 mN/m. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an optical compensation film.

  The liquid crystal panel includes a pair of polarizing plates arranged in crossed Nicols and a liquid crystal cell that is sandwiched between the polarizing plates and changes the polarization state of transmitted light. Each polarizing plate includes a polarizing film and a protective film that is provided on both surfaces of the polarizing film and protects the polarizing film. Of the pair of polarizing plates disposed on the light source side and the viewing side of the liquid crystal cell, the light emitted from the liquid crystal cell is incident on the viewing side of the pair of protective films sandwiching the polarizing film. One protective film that is emitted to the film is a so-called optical compensation film having an optical compensation function. By using this optical compensation film, the viewing angle of a liquid crystal display (LCD) incorporating a liquid crystal panel is improved.

  As an optical compensation film, a film made of cellulose acylate is often used. And in order to express the target optical compensation function, it is made of cellulose acylate by carrying out a so-called stretching process for applying tension in a predetermined direction during or after the film forming process in the solution film forming method. An optical compensation film is manufactured. Since an appropriate plasticity is required for the stretching process as well as the film formation, it is necessary to previously include a plasticizer in the film.

  Typical examples of the plasticizer used in the cellulose acylate film include phosphoric ester triphenyl phosphate (TPP) and biphenyl diphenyl phosphate (BDP). When these are used as a plasticizer, there is a problem that the plasticizer is deposited on the surface of the film by a film forming apparatus or a stretching apparatus or scattered outside. Therefore, Patent Document 1 proposes that the cellulose acylate film has a three-layer structure, and the plasticizer content in the two exposed surface layers is less than the plasticizer content in the base layer sandwiched between the two surface layers. ing. Patent Document 2 and Patent Document 3 also describe that the cellulose acylate film has a multilayer structure, and the content of the plasticizer is determined for each layer.

  However, there is a further problem when the above plasticizer is used. When such a cellulose acylate film is used as a polarizing plate protective film such as an optical compensation film, there is a problem that the display quality of the LCD fluctuates due to a change in humidity. This is because the retardation of the cellulose acylate film containing the plasticizer changes reversibly according to changes in humidity.

  Therefore, Patent Document 4 proposes that a compound that is not a phosphate ester, that is, a non-phosphate ester, among which a predetermined ester is used as a plasticizer. Thereby, the reversible change of the retardation due to the humidity change is suppressed, and the display quality of the LCD is prevented from fluctuating according to the humidity. Patent Document 5 proposes the use of a non-phosphate ester as a plasticizer for a multilayer cellulose acylate film.

  Moreover, although an optical compensation film is bonded with a liquid crystal cell through an adhesive agent, at the time of bonding failure or the like, it is peeled off and re-bonded, that is, re-bonded. Various proposals have been made so far in order to improve such re-bonding property, so-called reworkability. For example, Patent Document 6 proposes to provide tan δ with in-plane anisotropy. And in order to give in-plane anisotropy to tan δ, when the solvent residual amount in the solution casting is 5 to 30%, the film temperature is set to 60 to 140 ° C., and 1.01 to 2. The film is stretched in the width direction so that the draw ratio becomes 0 times. Patent Document 7 proposes improving impact strength, not tensile strength of a film. In order to improve the impact strength, thermal decomposition of cellulose acylate molecules during film formation is suppressed. And in order to suppress thermal decomposition, the moisture content is made into less than 0.7% in the reprecipitation drying process of a cellulose acylate. Patent Document 8 proposes that the elastic modulus in the width direction and the longitudinal direction have a predetermined relationship. For this reason, in patent document 8, the total draw ratio of the width direction including a conveyance process and an extending process is made larger than the total draw ratio of a elongate direction. And patent document 9 is proposing to make a water absorption elastic modulus and moisture permeability into a predetermined range for the improvement of rework property. In order to make the water absorption elastic modulus and moisture permeability within a predetermined range, Patent Document 9 mentions as one method to adjust the content of the plasticizer.

JP 2001-054936 A JP 2001-151902 A JP 2006-182865 A JP 2007-086992 A Japanese Patent No. 4036014 JP 2004-206038 A JP 2007-169589 A JP 2008-058893 A JP 2003-232926 A

  When the cellulose acylate film is used as an optical compensation film or a polarizing plate protective film, the film surface is saponified in advance when the film is bonded to the polarizing film, thereby bonding the polarizing film or the liquid crystal cell to the glass substrate. Strengthen power. However, since the cellulose acylate films using the predetermined plasticizers in Patent Documents 4 and 5 are excessively saponified by alkali, the cellulose acylate films that have undergone the saponification treatment are overlapped with each other. In addition to being bonded, there is a problem in that reworkability is also lacking, such as leaving an adhesive on the glass substrate if it is peeled off from the glass substrate of the liquid crystal cell in order to rework.

  Patent Documents 6 to 9 use a phosphate ester as a plasticizer, for example, a cellulose acylate film containing TPP or BDP as a plasticizer, even if there is a certain effect for improving reworkability. When used in a glass, the problem remains that the retardation fluctuates in accordance with changes in humidity, as in the cellulose acylate films described in Patent Documents 1 to 3. Moreover, although various compounds which are non-phosphate ester are illustrated by patent documents 6-9 as a plasticizer, about the adhesion | attachment of the films by the saponification process progressing too much is considered. Absent.

  Therefore, the present invention is an optical compensation film made of cellulose acylate, and has an object of providing an optical compensation film that is excellent in reworkability, does not excessively undergo saponification reaction due to alkali, and does not adhere to each other even when stacked on each other. And

In order to solve the above problems, the optical compensation film of the present invention is made of cellulose acylate, and the plasticizer is unevenly distributed in the thickness direction so that the content rate in the inside is higher than the film surface. It is a polymer having a repeating unit containing an ester bond of an acid and a diol, and Re obtained by the following formula (1) is in the range of 0 to 100 nm at a wavelength of 550 nm, and Rth obtained by the following formula (2) is at a wavelength of 550 nm. The surface energy of the film surface after being immersed in an aqueous solution of sodium hydroxide at 50 ° C. and 1 mol / L for 60 seconds, after being washed with water and dried is 50 mN / m or more and 75 mN / m or less. It is configured to be a range.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(In the formulas (1) and (2), nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction, d Represents thickness (unit: nm))

  The dicarboxylic acid is preferably at least one of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid.

  The aliphatic dicarboxylic acid is at least one of malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, cyclohexanedicarboxylic acid, maleic acid, and fumaric acid, and the aromatic dicarboxylic acid is phthalic acid. , Isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, at least any of 2,6-naphthalenedicarboxylic acid It is preferable that it is one.

  The diol is preferably at least one of an aliphatic diol and an aromatic diol.

  Aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4 -Butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol And the aromatic diol is preferably at least one of bisphenol A, 1,4-dihydroxyfunol, and benzene-1,4-dimethanol.

  The terminal of the plasticizer molecule is an aliphatic group having 1 to 22 carbon atoms, an aromatic group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, and 6 to 20 carbon atoms. It is preferably at least one of the following aromatic carbonyl groups.

  In the optical compensation film of the present invention, the saponification reaction due to alkali does not proceed excessively, so even if the films overlap each other, they do not adhere to each other, and are excellent in reworkability. Further, the optical compensation film of the present invention improves the viewing angle of the LCD, and the degree of polarization does not change even when the LCD is placed under high temperature and high humidity. Therefore, the contrast does not decrease even when the LCD is placed under high temperature and high humidity.

It is sectional drawing of the optical compensation film of this invention. It is a graph which shows the additive content rate in the thickness direction of an optical compensation film. It is explanatory drawing regarding the optical characteristic of the optical compensation film which provided the optically anisotropic layer. It is the schematic of the manufacturing equipment of an optical compensation film. It is a table | surface which shows prescription of dope used by the Example and the comparative example. It is a table | surface which shows the conditions and evaluation result in an Example and a comparative example.

  Hereinafter, the optical compensation film of the present invention will be described with reference to embodiments. However, this embodiment is an example of the present invention and does not limit the present invention.

  The optical compensation film 10 is made of cellulose acylate as a polymer component and contains a predetermined amount of plasticizer. By including a predetermined amount of plasticizer, it can be widened and reduced without breaking the cellulose acylate film in the stretching step described later, and the viewing angle of the LCD can be adjusted to a desired value.

The optical compensation film 10 has an in-plane retardation Re in a range of 0 to 100 nm with incident light having a wavelength of 550 nm, and a thickness direction retardation Rth0 to 400 nm due to widening and shrinking in the stretching process. The desired value of the range. As a result, the desired viewing angle is expressed on the LCD. Re is a value obtained from the following equation (1) and Rth is obtained from the following equation (2). In equations (1) and (2), nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction. , D represents thickness (unit: nm).
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)

  The optical compensation film 10 is manufactured by co-casting dopes having different masses of plasticizer (hereinafter referred to as plasticizer content) relative to the unit mass of cellulose acylate. If one of the plasticizer contents relatively low is the first dope and one of the plasticizer contents higher than the first dope is the second dope, the optical compensation film 10 is formed from the first dope and exposed. The surface layer 11 and the 2nd surface layer 12, and the center layer 13 formed from the 2nd dope and formed between the 1st surface layer 11 and the 2nd surface layer 12 are provided. However, since the polymer components of the first dope and the second dope are the same cellulose acylate and are manufactured by co-casting, each boundary surface between the first surface layer 11, the central layer 13, and the second surface layer 12 is not exist. Therefore, the boundary line between the first surface layer 11 and the central layer 13 and the boundary line between the central layer 13 and the second surface layer 12 in FIG. 1 are shown for convenience of explanation and are merely conceptual.

  In the optical compensation film 10, the plasticizer is unevenly distributed in the thickness direction. In the graph of FIG. 2 showing the uneven distribution of the plasticizer, the vertical axis indicates the content of the plasticizer, and the higher the value, the higher the plasticizer content. The horizontal axis is the thickness direction of the optical compensation film. The first range R1 on the horizontal axis corresponds to the first surface layer 11, the second range R2 corresponds to the second surface layer 12, and the third range R3 corresponds to the central layer 13. As described above, the first range R1 and the second range R2 formed from the first dope having a high plasticizer content rate have a higher plasticizer content rate than the third range R3 formed from the second dope. Thus, in the optical compensation film 10, the plasticizer is unevenly distributed in the thickness direction so that the internal plasticizer content is higher than the film surfaces 11a and 12a.

  When the predetermined amount of plasticizer is unevenly distributed in the thickness direction as described above, (1) widening and shrinking can be performed without breaking the cellulose acylate film in the stretching step. ) The plasticizer hardly scatters in the apparatus during the film forming process or stretching process or deposits on the film surface, and (3) it adheres when the optical compensation films 10 before saponification treatment are overlapped. There is also an effect that (4) saponification does not proceed excessively when saponification processing is performed, so that reworkability is good.

  The graph showing the uneven distribution of the plasticizer in the thickness direction, that is, the distribution does not need to be a target with respect to the central portion in the thickness direction as shown in FIG. For example, the additive content in the first range R1 and the second range R2 need not be the same value. Further, it is not necessary that the additive content in the third range R3 is constant.

  When the 1st surface 11a is a bonding surface bonded with a polarizing film (not shown), the 1st surface 11a will be saponified. However, it is difficult to apply saponification treatment to only one film surface, and even if possible, the structure of the saponification treatment apparatus must be complicated, so that it can be superimposed on the first surface 11a and the glass substrate of the liquid crystal cell. Both film surfaces with the second surface 12a are saponified. Therefore, a relationship between the degree of progress of saponification under the saponification conditions to be performed and the additive content in the first range R1 is obtained in advance, and the additive content corresponding to the saponification conditions is determined based on this relationship. be able to.

  However, the additive content in the first range R1 is not determined according to the saponification conditions, but the target of the adhesive strength with the polarizing film (polyvinyl alcohol (PVA)), the reworkability, and the extent that the films do not adhere to each other. It is preferable to determine the additive content in the first range R1 according to the level. This is because, by making the saponification conditions constant, the maintenance of the production line for the optical compensation film 10 becomes easier.

  Therefore, in the present invention, the optical compensation film 10 is immersed in a 1 mol / L sodium hydroxide aqueous solution maintained at 50 ° C. for 60 seconds, and then this optical compensation film 10 is washed with water (washed with water). The first range so that the surface energy of the first surface 11a and the second surface 12a is in the range of 50 mN / m or more and 75 mN / m or less when the saponification treatment is performed under the generally practiced condition of drying. Determine the additive content of R1. This is because when the surface energy is within this range, the adhesive strength with the polarizing film and the reworkability are almost compatible. If the surface energy of the first surface 11a is less than 50 mN / m, the adhesive force with the polarizing film is too small, or if the surface energy of the second surface 12a is less than 50 mN / m, the second surface 12a and the adhesive Since the bonding force is too weak, the adhesive remains on the glass substrate, and there is concern about reworkability. On the other hand, when it is larger than 75 mN / m, the films may be bonded to each other. The surface energy can be obtained from the contact angle obtained by obtaining the contact angle with pure water. The contact angle can be obtained with a commercially available contact angle measuring device (for example, CA-A type manufactured by Kyowa Interface Science Co., Ltd.), and there are also commercially available devices for obtaining the surface energy from the measured contact angle. May be used.

[Plasticizer]
The plasticizer is an ester as a polymer having a repeating unit containing an ester bond of a dicarboxylic acid and a diol, and is not a phosphate ester. And TPP and BDP which are phosphate esters are not used in the present invention. One of the reasons why the cellulose acylate film is used as a polarizing plate protective film or an optical compensation film is that it has an appropriate moisture permeability. However, when TPP or BDP is included in the optical compensation film 10, an appropriate moisture permeability of cellulose acylate is obtained in an atmosphere of high temperature and high humidity (for example, a temperature of 60 ° C. or higher and a relative humidity of 90% RH or higher). Therefore, TPP and BDP are hydrolyzed to generate phenol. Most of the polarizing films are obtained by dyeing polyvinyl alcohol (PVA) with iodine. Phenol acts as a reducing agent on iodine contained in the polarizing film, and iodine is reduced. In the present invention, a polymer containing an ester bond of a dicarboxylic acid and a diol in the repeating unit is used as a plasticizer, so that a substance capable of reducing iodine is not generated, thereby changing the polarization degree of the polarizing film. Can be suppressed. As a result, even when the LCD is placed under high temperature and high humidity, the initial contrast can be maintained without reducing the contrast of the LCD.

  In the present invention, by using a polymer having a predetermined repeating unit as a plasticizer, it is difficult for the plasticizer to be deposited on the film surface, and the plasticizer is less likely to be scattered outside. This effect and the effect of preventing breakage due to widening in the stretching process are so-called non-polymers that are not polymers, and are far greater than monomers having the same number average molecular weight as the plasticizer used in the present invention. Therefore, compared with the case where a monomer having a number average molecular weight comparable to that of the plasticizer used in the present invention is used as the plasticizer, the film temperature in drying is set to a higher temperature so as to increase the drying efficiency in the film forming process. In addition, Re and Rth can be controlled in a larger range.

  By making the plasticizer which is a polymer unevenly distributed in the thickness direction as described above, the effect of preventing precipitation on the film surface and scattering to the outside is further improved.

  The plasticizer used as a plasticizer is preferably an oligomer having a degree of polymerization of about 300 or more and 2000 or less in order to uniformly disperse the respective layers 11 to 13 of the optical compensation film 10 so as not to aggregate. By being an oligomer, precipitation on the film surface and scattering to the outside can be prevented, and this can be uniformly dispersed in each of the layers 11 to 13 so that the transparency of the cellulose acylate is not impaired. . In addition, as for this polymer, it is more preferable that a number average molecular weight is the range of 700-10000.

  As the dicarboxylic acid, at least one of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid can be used. An aliphatic dicarboxylic acid is preferable when the flexibility (flexibility) of the optical compensation film 10 is further increased, and an aromatic dicarboxylic acid is preferable when the heat resistance and strength are further increased. When flexibility and strength are increased, the stretching ratio in the stretching process can be set larger, so that the control range of Re and Rth can be further expanded. Moreover, deterioration at high temperature and high humidity can be prevented by further increasing the heat resistance.

  Aliphatic dicarboxylic acid and aromatic dicarboxylic acid may be used in combination, and in the case of using together, according to the target level of flexibility, heat resistance and strength of the optical compensation film 10, the mass ratio of both is determined. Good. For example, when only an aromatic dicarboxylic acid is used, the heat resistance of the optical compensation film 10 is improved as compared with the case where only an aliphatic dicarboxylic acid is used, but flexibility is often impaired. By using both together, the optical compensation film 10 in which both heat resistance and flexibility have reached the target level can be manufactured.

  As the aliphatic carboxylic acid, at least one compound of malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, cyclohexanedicarboxylic acid, maleic acid, and fumaric acid is preferable. This is because the polymerization degree is easily controlled in the polymerization with various diols. If the degree of polymerization is easily controlled, the optical compensation film 10 whose flexibility is close to the target value can be more reliably manufactured.

  Examples of the aromatic dicarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2 1,6-Naphthalenedicarboxylic acid is preferably at least one compound. These also have an advantage that the degree of polymerization with the diol can be easily controlled as compared with other aromatic dicarboxylic acids.

  The diol may be either an aliphatic diol or an aromatic diol. An aliphatic diol is preferable when the flexibility (flexibility) of the optical compensation film 10 is further increased, and an aromatic diol is preferable when the heat resistance and strength are further increased. An aliphatic diol and an aromatic diol may be used in combination, and in the case of using them together, the mass ratio between the two may be determined according to the target level of flexibility and heat resistance of the optical compensation film 10.

  Aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1, 4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedi It is preferable to use at least one of methanol. This is because the degree of polymerization is easily controlled in the polymerization with the various dicarboxylic acids.

  As the aromatic diol, at least one of bisphenol A, 1,4-dihydroxyfunol, and benzene-1,4-dimethanol is preferable. These also have the advantage that the control of the degree of polymerization with the various dicarboxylic acids is easier than other aromatic diols.

  The end of the plasticizer molecule is an aliphatic group having 1 to 22 carbon atoms, an aromatic-containing group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, or 6 to 20 carbon atoms. It is preferably at least one of the following aromatic carbonyl groups. These are excellent in affinity with cellulose acylate, and when these are used, there is an advantage that the alkali solution used for the saponification treatment is suppressed from excessively penetrating into the optical compensation film.

[Cellulose acylate]
Among cellulose acylates, the ratio of esterifying the hydroxyl group of cellulose with carboxylic acid, that is, the degree of acyl group substitution (hereinafter referred to as acyl group substitution degree) satisfies all the conditions of the following formulas (I) to (III). What is satisfied is more preferable. In (I) to (III), A and B are both acyl group substitution degrees, the acyl group in A is an acetyl group, and the acyl group in B has 3 to 22 carbon atoms. In order to reduce Re to 0 nm or more and 10 nm or less, A + B is more preferably in the range of 2.8 or more and 3.0 or less, and further preferably in the range of 2.8 or more and 2.9 or less.
2.5 ≦ A + B ≦ 3.0 (I)
0 ≦ A ≦ 3.0 (II)
0 ≦ B ≦ 2.9 (III)

  Glucose units constituting cellulose and having β-1,4 bonds have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of these hydroxyl groups are esterified, and hydrogen of the hydroxyl groups is substituted with acyl groups having 2 or more carbon atoms. Since the degree of substitution is 1 when esterification of one hydroxyl group in the glucose unit is 100%, in the case of cellulose acylate, the hydroxyl groups at the 2nd, 3rd and 6th positions are each 100% ester. The degree of substitution is 3.

  Here, the substitution degree of the acyl group at the 2-position of the glucose unit is DS2, the substitution degree of the acyl group at the 3-position is DS3, and the substitution degree of the acyl group at the 6-position is DS6. The total acyl group substitution degree determined by DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and even more preferably 2.40 to 2.88. . DS6 / (DS2 + DS3 + DS6) is preferably 0.32 or more, more preferably 0.322 or more, and further preferably 0.324 to 0.340.

  There may be only one kind of acyl group, or two or more kinds. When there are two or more acyl groups, it is preferable that one of them is an acetyl group. DSA + DSB, where DSA is the sum of the substitution degrees of the hydrogens of the hydroxyl groups at the 2nd, 3rd and 6th positions with the acetyl group, and DSB is the sum of the substitution degrees other than the acetyl groups at the 2nd, 3rd and 6th positions The value of is preferably 2.2 to 2.86, particularly preferably 2.40 to 2.80. DSB is preferably 1.50 or more, and particularly preferably 1.7 or more. Further, it is preferable that 28% or more of the DSB is a substituent at the 6-position hydroxyl group, more preferably 30% or more, still more preferably 31% or more, and particularly preferably 32% or more is a substituent at the 6-position hydroxyl group. Preferably there is. The 6-position DSA + DSB value of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more.

  The acyl group having 2 or more carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. For example, there are cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester, etc., and these may each further have a substituted group. Propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group, t-butanoyl group, cyclohexane Examples thereof include a carbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  The optical film 10 is manufactured such that the thickness is in the range of 10 μm to 200 μm, the width is in the range of 500 mm to 4000 mm, and the length is in the range of 100 m to 8000 m.

  The optical compensation film 10 is provided with a so-called optical anisotropic layer having optical anisotropy on one of the film surfaces. FIG. 3 shows the optical compensation film 10 when the optically anisotropic layer 16 is provided on the second surface 12a. The optically anisotropic layer 16 has a configuration in which a liquid crystal compound is sandwiched between glass substrates. Here, the direction in which Re is the smallest in the plane of the optical anisotropic layer 16 is the-(minus) direction on the x axis, the normal direction of the surface of the optical anisotropic layer 16 is the y axis, the x axis, and the y axis. The direction perpendicular to the axis is taken as the z-axis. The arrow (A) in FIG. 3 is the longitudinal direction of the optical compensation film 10 when the optical compensation film 10 is produced with the film production facility in FIG. 4, and in this embodiment, coincides with the x axis.

  In the plane including the x axis and the y axis, that is, the xy plane, Re of the optical compensation film 10 obtained in the normal direction is represented as Re (0 °), and in the xy plane, from the y axis to the positive direction of the x axis. Re (θ1) represents Re of the optical compensation film 10 in the direction inclined by θ1 (°), and Re (−θ2) represents Re of the optical compensation film 10 in a direction inclined by θ2 (°) in the minus direction. For example, the Re of the optical compensation film 10 in the direction tilted 50 ° from the y-axis to the minus direction of the x-axis on the xy plane is Re (−50 °). Re of the compensation film 10 is represented as Re (50 °). In the optical compensation film 10, Re (0 °) at 30 ° C. and 50% RH is in the range of (35 ± 30) nm, and Re (−50 °) under the same condition is in the range of (40 ± 35) nm. The Re (50 °) under the same conditions is in the range of (110 ± 85) nm. It should be noted that the range of (A ± B) nm for these Re means a range of (A−B) nm or more and (A + B) or less.

  As shown in FIG. 4, a film production facility 30 for producing an optical compensation film includes a dope production unit 31 for producing a plurality of dopes having different additive contents, and a solution casting of the optical compensation film 10 from the plurality of dopes. It consists of the solution film-forming part 32 manufactured by this.

  In the dope manufacturing section 31, a first dope 33 for forming the first and second surface layers 11 and 12 (see FIG. 1) and a second dope 34 for forming the central layer 13 (see FIG. 1) are formed. The solution casting part 32 forms a casting film 35 composed of the first dope 33 and the second dope 34 and peels off the casting film 37 as a wet film 36 containing a solvent, and the wet film 36 is dried. The optical compensation film 10 includes a drying area 38 and a winding area 39 that winds the optical compensation film 10 into a roll shape.

  In the dope manufacturing unit 31, a cellulose acylate 41, a plasticizer 42, and a solvent 43 that dissolves the cellulose acylate 41 and the plasticizer 42 are used.

  The dope manufacturing unit 31 includes a first dissolving device 47 for dissolving a plasticizer 42 in a solvent 43 to produce a first plasticizer liquid 45 and a second plasticizer liquid 46 having different concentrations of the plasticizer 42, a cellulose acid And a second dissolving device 51 that dissolves the rate 41 in the solvent 43 to obtain a cellulose acylate solution 50 having a predetermined concentration. One with a low additive concentration is a first plasticizer liquid 45 and the other with a high additive concentration is a second plasticizer liquid 46.

  The cellulose acylate solution 50 produced by the second dissolving device 51 is sent downstream through two liquid feeding lines, a first liquid feeding line L1 and a second liquid feeding line L2. Each flow rate in the first liquid feeding line L1 and the second liquid feeding line L2 is adjusted by the first liquid feeding controller 52, respectively.

  Moreover, the 1st plasticizer liquid 45 is sent by the 3rd liquid feeding line L3 connected to the 1st liquid feeding line L1, and is added in-line to the cellulose acylate solution 50 which flows through the 1st liquid feeding line L1. The 2nd plasticizer liquid 46 is sent by the 4th liquid feeding line L4 connected to the 2nd liquid feeding line L2, and is added in-line to the cellulose acylate solution 50 which flows through the 2nd liquid feeding line L2. At this time, the flow rate of the first plasticizer liquid 45 in the third liquid feed line L3 is set by the second liquid feed controller 54, and the flow rate of the second plasticizer liquid 46 in the fourth liquid feed line L4 is set by the third liquid feed controller 55. , Adjust each.

  As described above, the first dope 33 having a predetermined plasticizer content can be obtained by adjusting the flow rates of the cellulose acylate solution 52 and the first and second plasticizer liquids 46 and 47 each having a predetermined concentration. The first dope 33 and the second dope 34 can be formed as the optical compensation film 10 that can form the second dope 34 and that does not have the boundaries between the first surface layer 11, the central layer 13, and the second surface layer 12. Can be manufactured.

  The first dope 33 and the second dope 34 are guided to the casting area 37 of the solution casting part 32 by independent liquid feeding lines. Then, the first dope 33 is sent to the casting area 37 through two liquid feeding lines.

  In the casting area 37, a casting die 56 that flows out of the first dope 33 and the second dope 34, a band 57 that is disposed below the casting die 56 and continuously runs, and a band 57 Are wound around the circumferential surface and at least one of them is driven to rotate to drive the band 57, and a roller 59 for supporting the wet film 36 when the casting film 35 is peeled off from the band 57. It has been. Further, the upstream end face of the casting die 56 is provided with a feed block 61 that joins the first dope 33 and the second dope 34 that have been guided independently and guides them to the casting die 56. On the upstream side of the casting die 56, a decompression chamber 62 that sucks and decompresses air in an area upstream of the bead formed from the casting die 56 to the band 57 is provided. In the feed block 61, the first dope 33 and the second dope 34 are merged so that the flow of the second dope 34 is sandwiched between the two flows of the first dope 33.

  The first dope 33 and the second dope 34 merged in the feed block 61 are cast from the casting die 56 to the band 57 in a state where the flows are overlapped. By at least one of drying and cooling, the casting film 35 is hardened to such an extent that it can be conveyed by a roller, that is, has a self-supporting property, and the casting film 35 is peeled off from the band 57, Guide to the tenter 66 in the drying area 38. In the vicinity of the conveyance path from the band 57 to the tenter 66, an air duct 67 for blowing dry air onto the wet film 36 is provided in order to advance the drying of the wet film 36.

  The tenter 66 is provided with holding means for holding the side edge of the wet film 36 on both sides of the transport path of the wet film 36. As the holding means, a clip 68 that grips the wet film 36 is used, but instead of the clip 68, a pin that pierces and holds the wet film may be used. The plurality of clips 68 are provided in an endless chain (not shown) that continuously travels, and the travel path of the clips 68 can be changed by displacing the travel path of the chain. By setting the travel path of the chain so that the distance between the clip 68 disposed on both sides of the wet film 36 and the clip 68 gradually increases toward the downstream side, the width of the wet film 36 can be expanded. .

  With the tenter 66, the wet film 36 is widened at a predetermined stretching ratio at a predetermined timing, or is contracted to reduce the width. In addition, a draw ratio is a value calculated | required by W2 / W1, when the width | variety before implementing width expansion or contraction is W1, and the width after implementation is W2. Re and Rth are controlled by this widening and contraction.

  The tenter 66 is provided with a blower duct 66a that blows dry air whose temperature is adjusted to the wet film 36, and by this blow, the wet film 36 is dried while being held and conveyed by the clip 68.

  The wet film 36 released from the grip by the clip 68 is guided to a cutting device 71 provided downstream of the tenter 66. A grip mark remains at the grip position held by the clip 68 of the wet film 36. Therefore, the excision device 71 continuously cuts the side end portion of the wet film 36 so that the grip trace is separated from the central portion that becomes the optical compensation film 10.

  Downstream of the cutting device 71, there is a drying chamber 74 that includes a plurality of rollers 73 that support the wet film 36 with both side ends cut off on the circumferential surface, and a blower duct (not shown) that blows dry air. The roller 73 includes a driving roller that conveys the wet film 36 by being rotationally driven in the circumferential direction. In the air duct, a plurality of slits (not shown) extending in the width direction of the wet film 36 are provided in the transport direction, and the wet film 36 is dried and optically dried by dry air of a predetermined temperature emitted from these slits. The compensation film 10 is obtained. The optical compensation film 10 is wound in a roll shape by a winding device 77 in the winding area 39.

  Below, Experiments 1-6 which are the scope of the present invention are described. First, with the prescription shown in the table of FIG. 5, six types of dopes B1 to B3 and C1 to C3 were manufactured in the dope manufacturing unit 31. The “polymer” in the “plasticizer” column of FIG. 5 is an oligomer that is a non-phosphate ester. This oligomer has a repeating unit containing an ester bond of a dicarboxylic acid and a diol. In this “polymer” column, “terminal OH” means that the terminal of the molecule that is a polymer is —OH, and “terminal acyl group” means that the molecule is a polymer. The terminal of is an acyl group. In addition, the unit of each numerical value in FIG. 5 is a mass part.

  The optical compensation film 10 of the present invention was manufactured using the manufactured B1 to B3 and C1 to C3 in the combinations shown in the table of FIG. These are Experiments 1-6. In FIG. 6, “first dope” is the first dope 33 for forming the first surface layer 11, and “second dope” is the first dope 33 for forming the second surface layer 12. is there. The central layer 13 is formed from the “second dope”.

  In each experiment 1-6, the wet film 36 was widened by the tenter 66 so as to achieve the draw ratio shown in Table 6.

  For each optical compensation film 10 obtained, Re and Rth were obtained, and the reworkability of the film after saponification treatment and the evaluation of the adhesion between the films before saponification treatment were performed. Each evaluation method is as follows. The evaluation results are shown in the “Evaluation” column of FIG.

(1) Re and Rth
Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), three-dimensional birefringence measurement is performed at a wavelength of 590 nm under an atmosphere of 23 ° C. and 55% RH, and nx, ny, nz Each refractive index is obtained. Re and Rth were calculated by the above formulas (1) and (2). By setting Re and Rth within a predetermined range, an optical compensation film according to the application is obtained. Specifically, when Re is 0 to 10 nm and Rth is 20 to 60 nm, a polarizer protective film, and when Re is 20 to 60 nm and Rth is 60 to 200 nm, a VA retardation film, Re is 0 to 0 nm. If Rth is 0 to 5 nm at 5 nm, it can be used as a retardation film for IPS.

(2) Reworkability An adhesive having a thickness of 25 μm formed on the release-treated PET film is applied to each optical compensation film 10 using a sticking device (trade name: Lami Packer, manufactured by Fuji Plastic Machinery Co., Ltd.). Transferred from PET film. The optical compensation film 10 is preliminarily immersed in an aqueous solution of sodium hydroxide at 50 ° C. and 1 mol / L for 60 seconds before the adhesive is applied, and then saponified under the condition of washing and drying. is there. A strip test piece having a width of 25 mm and a length of 250 mm was cut out from the optical compensation film 10 with the adhesive. Next, the adhesive side of this test piece was attached to a non-alkali glass plate (product number 1737, manufactured by Corning) that had been washed and dried using the above-described attaching device. This test piece was autoclaved at 50 ° C. and 500 kPa for 20 minutes. Next, after heat-treating at 70 ° C. for 2 hours and then storing in a constant temperature bath at 50 ° C. for 48 hours, the optical compensation film 10 is removed from the glass plate at a speed of 300 mm / min at a temperature of 23 ° C. and a relative humidity of 50%. And peeled in the 180 ° direction, the surface of the glass plate was visually observed, and evaluated according to the following criteria. This evaluation result is shown in the column of “Reworkability” in FIG. The adhesive is a sample with a sticking area (10 mm × 10 mm), a 200 g load is applied for 1 hour in a 50 ° C. atmosphere, and the creep value is 30 to 50 μm when the load is removed in a room temperature atmosphere. Was used.
○: No fogging is observed on the surface of the glass plate.
Δ: Clouding or the like is observed on the surface of the glass plate, but is acceptable.
X: The remainder of an adhesive agent is recognized by the surface of a glass plate.

(3) Presence / absence of adhesion between films The optical compensation film 10 before the saponification treatment is temporarily wound into a roll and left for a predetermined time, and then the optical compensation film 10 is pulled out from the film roll and pulled out. It was visually evaluated whether or not. This evaluation item is shown in the “adhesion presence / absence” column of FIG. In addition, “◯” and “×” described in FIG. 6 represent the following meanings, respectively.
○: No adhesion ×: Adhesion

[Comparative example]
Three types of dopes A1 to A3 were manufactured according to the formulation shown in the table of FIG. An optical compensation film was manufactured using these and the dopes manufactured in the examples in combinations shown in the table of FIG. These are designated as comparative experiments 1 to 4. In the “plasticizer” column of FIG. 5, “phosphate ester” is a mixture of TPP and BDP.

  The obtained optical compensation film was evaluated in the same manner as in the examples. The evaluation results are shown in FIG.

DESCRIPTION OF SYMBOLS 10 Optical compensation film 11 1st surface layer 12 2nd surface layer 13 Center layer

Claims (6)

Made of cellulose acylate,
The plasticizer is unevenly distributed in the thickness direction so that the content in the inside is higher than the film surface,
The plasticizer is a polymer having a repeating unit containing an ester bond of a dicarboxylic acid and a diol,
Re obtained by the following formula (1) is a range of 0 to 100 nm at a wavelength of 550 nm, Rth obtained by the following formula (2) is a range of 0 to 400 nm at a wavelength of 550 nm
An optical system characterized in that the surface energy of the film surface after being immersed in an aqueous solution of sodium hydroxide at 50 ° C. and 1 mol / L for 60 seconds, washed with water and dried is in the range of 50 mN / m to 75 mN / m. Compensation film.
Re = (nx−ny) × d (1)
Rth = {(nx + ny) / 2−nz} × d (2)
(In the formulas (1) and (2), nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction, d Represents thickness (unit: nm))   2. The optical compensation film according to claim 1, wherein the dicarboxylic acid is at least one of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid. The aliphatic dicarboxylic acid is at least one of malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, cyclohexanedicarboxylic acid, maleic acid, fumaric acid,
The aromatic dicarboxylic acid includes phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2, The optical compensation film according to claim 2, which is at least one of 6-naphthalenedicarboxylic acid.   The optical compensation film according to any one of claims 1 to 3, wherein the diol is at least one of an aliphatic diol and an aromatic diol. The aliphatic diol includes ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1, 4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedi At least one of methanol,
The optical compensation film according to claim 4, wherein the aromatic diol is at least one of bisphenol A, 1,4-dihydroxyfunol, and benzene-1,4-dimethanol.   The terminal of the molecule of the plasticizer is an aliphatic group having 1 to 22 carbon atoms, an aromatic-containing group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, and 6 or more carbon atoms. The optical compensation film according to any one of claims 1 to 5, wherein the optical compensation film is at least one of 20 or less aromatic carbonyl groups.

Images