JP5962002B2 - Polarizing plate and display device using the same - Google Patents

Description

  The present invention relates to a polarizing plate used in a display device such as a liquid crystal display device or an organic EL display.

  A polarizing plate used for a liquid crystal display device or the like usually has a configuration in which a polarizing plate protective film made of a polymer film is bonded to both surfaces of a polarizer. Examples of the constituent material of the polarizer include a polyvinyl alcohol film, an ethylene vinyl alcohol film, a cellulose film, and a polycarbonate film. From the viewpoint of processability, etc., the iodine-stained polyvinyl alcohol film is stretched. In general, those obtained by stretching a polyvinyl alcohol film and then dyeing with iodine are generally used. On the other hand, as a polarizing plate protective film, a cellulose acylate film such as a triacetyl cellulose (TAC) film is widely used because of its small optical anisotropy, excellent transparency, and excellent adhesion to a polarizer. Has been.

  In recent years, with the development of thin and light notebook PCs, tablet terminals, smartphones, etc., there is an increasing demand for thinner and higher performance polarizing plate protective films used in display devices such as liquid crystal display devices. It is becoming. When the polarizing plate protective film is thinned, there is an advantage that curling can be suppressed when the polarizing plate is produced.

  However, when a cellulose acylate film used as a polarizing plate protective film is thinned to constitute a polarizing plate, the polarizer deteriorates when exposed to a high temperature and high humidity environment (the transmittance of the polarizing plate increases). There is.

  Conventionally, a sufficiently effective means has not been developed as a means for preventing the deterioration of the polarizer in such a high temperature and high humidity environment.

  By the way, Patent Document 1 discloses a technique in which in a clear hard coat film having a hard coat layer on a transparent film substrate, the hard coat layer contains a fluorine-siloxane graft polymer and an energy active ray curable resin. And it is also disclosed that it is good to contain the acryloyl type compound which has a predetermined structure in a transparent film base material as a preferable form.

International Publication No. 2009/001629 Pamphlet

  The present invention has been made in view of the above-described conventional state of the art, and provides a means capable of achieving a reduction in the thickness of a polarizing plate while minimizing the deterioration of the polarizer in a high temperature and high humidity environment. For the purpose.

  The present inventors diligently searched for the mechanism of polarizer deterioration under a high temperature and high humidity environment. As a result, it was found that cellulose acylate was decomposed by reacting with high-temperature water in a high-temperature and high-humidity environment, and a small amount of decomposition product produced thereby caused the polarizer deterioration.

  And based on such knowledge, the acryloyl-based compound having a predetermined structure is included in the polarizing plate protective film, and further, by controlling the halogen element content in the polarizing plate protective film to a value within a predetermined range, The present inventors have found that the above problems can be solved, and have completed the present invention.

  That is, the above object of the present invention is achieved by the following configuration.

1. A polarizer,
A first polarizing plate protective film containing cellulose acylate bonded to one surface of the polarizer;
A second polarizing plate protective film bonded to the other surface of the polarizer;
A polarizing plate having
The thickness is 50-100 μm,
The first polarizing plate protective film has the following general formula (1):

In the formula, R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ₁₂ and R ₁₃ each independently represents an alkyl group having 1 to 8 carbon atoms,
An acryloyl-based compound represented by
The halogen element content in the first polarizing plate protective film is 100% of the total amount of the film.
Ri 50-2000 mass ppm der relative to the weight%,
A polarizing plate in which a clear hard coat layer is disposed on the surface of either the first polarizing plate protective film or the second polarizing plate protective film ;
2. The polarizing plate according to 1 above, wherein the second polarizing plate protective film contains cellulose acylate;
3. The first polarizing plate protective film has the following general formula (2):

In the formula, B is a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, and G is an alkylene glycol residue having 2 to 18 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or 4 carbon atoms. -12 is an oxyalkylene glycol residue having -12, A is an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 16 carbon atoms, and n is an integer of 1 or more.
The polarizing plate of said 1 or 2 containing the polyester-type compound represented by these;
4). The polarizing plate according to any one of the above 1 to 3, wherein the first polarizing plate protective film does not contain a halogen element-containing ultraviolet absorber;
5. The polarizing plate of any one of said 1-4 whose thickness of a said 1st polarizing plate protective film is 15-35 micrometers;
6). The clear hard coat layer, wherein the first polarizing plate protective film, the are arranged in a surface opposite to the polarizer, the polarizing plate according to any one of the above 1 to 5;
7). The polarizing plate according to any one of 1 to 6 above, wherein the clear hard coat layer contains an ultraviolet absorber;
8). It is a manufacturing method of the polarizing plate of any one of said 1-7,
Drying the film obtained by casting a dope containing cellulose acylate, the acryloyl-based compound and a solvent on a support, obtaining the first polarizing plate protective film by a process of peeling and peeling, and
Bonding the obtained first polarizing plate protective film with a polarizer;
A production method comprising:
9. 9. The production method according to 8 above, wherein the solvent is a halogen-based solvent.

10. The display apparatus provided with the polarizing plate of any one of said 1-7.

  ADVANTAGE OF THE INVENTION According to this invention, the means which can achieve the thin film formation of a polarizing plate can be provided, suppressing deterioration of a polarizer in high temperature, high humidity environment to the minimum. The reason for this is not necessarily clear, but the acryloyl-based compound contained in the first polarizing plate protective film and a trace amount of halogen elements interact in some way, so that the degradation effect on the polarizer due to a trace decomposition product of cellulose acylate. It is thought that it is suppressing.

  Hereinafter, embodiments of the present invention will be described in detail.

  In one embodiment of the present invention, a polarizer, a first polarizing plate protective film containing cellulose acylate, which is bonded to one surface of the polarizer, and the other surface of the polarizer are bonded. And a second polarizing plate protective film.

  And the polarizing plate which concerns on this form has the characteristics in the point whose thickness is 50-100 micrometers first. Moreover, in the polarizing plate which concerns on this form, the 1st polarizing plate protective film has the following general formula (1):

In the formula, R ¹¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ¹² and R ¹³ each independently represents an alkyl group having 1 to 8 carbon atoms,
It is also characterized in that it contains an acryloyl compound represented by the formula: Furthermore, in the polarizing plate which concerns on this form, the halogen element content in a 1st polarizing plate protective film also has the characteristics that it is 50-2000 mass ppm with respect to 100 mass% of the total amount of a film.

≪Polarizing plate≫
Hereinafter, the polarizing plate according to the present embodiment will be described in more detail.

[Polarizer]
The polarizing plate according to this embodiment includes a polarizer as a main component. A polarizer is an element that allows only light of a plane of polarization in a certain direction to pass through. A typical polarizer known at present is a polyvinyl alcohol polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. Further, it is more preferable that the difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the film is 1 ° C. or less, and further two points 1 cm apart in the TD direction of the film. In order to reduce color spots, it is more preferable that the difference in hot water cutting temperature between them is 0.5 ° C. or less.

  A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

[Polarizing plate protective film]
The polarizing plate which concerns on this form has a polarizing plate protective film on both surfaces of a polarizer, respectively. These two polarizing plate protective films are referred to as “first polarizing plate protective film” and “second polarizing plate protective film”, respectively, but the ordinal numbers “first” and “second” are two pieces. It is given only for the purpose of naming the polarizing plate protective film for convenience, and the expression “first” and “second” itself has no particular meaning. In addition, as long as it is the polarizing plate protective film which has the characteristics mentioned above, even if it is the polarizing plate protective film arrange | positioned in any surface side of a polarizer, it may be a "1st polarizing plate protective film".

<First polarizing plate protective film>
(Cellulose acylate)
The first polarizing plate protective film first contains cellulose acylate. The cellulose acylate contained in the first polarizing plate protective film is preferably a carboxylic acid ester having about 2 to 22 carbon atoms, and particularly preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. In the case of the same substitution degree, birefringence decreases when the number of carbon atoms in the acyl group is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms.

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

  Further, the retardation value can be appropriately controlled by the kind of the acyl group of cellulose acylate, the substitution degree of the acyl group to the pyranose ring of the cellulose resin skeleton, and the like.

  In the present invention, the cellulose acylate preferably satisfies the following formulas (1) and (2) at the same time.

  In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group. According to the cellulose acylate satisfying the above two formulas, a film exhibiting excellent physical properties and optical properties that meet the object of the present invention can be constituted.

  Of these, triacetyl cellulose and cellulose acetate propionate are particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 1.5, and 2.0 ≦ X + Y ≦ 3.0. In addition, the measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  If the substitution degree of the acyl group is too low, there will be many unreacted parts with respect to the hydroxyl groups of the pyranose ring constituting the skeleton of the cellulose resin, and many hydroxyl groups will remain, thereby changing the humidity of the retardation and protecting the polarizing plate. The ability to protect the polarizer as a film may decrease, which is not preferable.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate according to this embodiment is preferably 1.4 to 3.0. In addition, in this form, although it is preferable that the 1st polarizing plate protective film contains the cellulose acylate whose value of Mw / Mn is 1.4-3.0 as a material, the cellulose contained in a film The Mw / Mn value of the entire acylate (preferably cellulose triacetate or cellulose acetate propionate) is more preferably in the range of 1.4 to 3.0. More preferably, it is 1.7-2.2.

  In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds simultaneously, and the polymer chain is broken and the acetyl group is decomposed, resulting in an undesirable result. Therefore, it is necessary to set the reaction time within a predetermined range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions are various and greatly change depending on the reaction apparatus, equipment and other conditions. Since the molecular weight distribution becomes wider as the decomposition of the polymer proceeds, also in the case of cellulose acylate, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. That is, in the process of acetylation of cellulose triacetate, the weight average molecular weight (which is not too long and does not proceed excessively and is used as one index of the reaction degree for allowing acetylation for a sufficient time for acetylation ( The value of Mw) / number average molecular weight (Mn) can be used.

  The molecular weight of the cellulose acylate according to this embodiment is preferably 80000 to 200000 in terms of number average molecular weight (Mn). Those having 100,000 to 200,000 are more preferred, and those having 150000 to 200,000 are particularly preferred.

  The average molecular weight and molecular weight distribution (Mw / Mn) of cellulose acylate can be measured by a known method (for example, the following method) using high performance liquid chromatography. The number average molecular weight (Mn) and the weight average molecular weight (Mw) are calculated using this, and the ratio (Mw / Mn) may be calculated.

(Measurement method of average molecular weight of cellulose acylate)
Measured by high performance liquid chromatography under the following conditions.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

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

  The average substitution degree of the acyl group at the 6-position of the glucose unit of the cellulose acylate used in the present invention is preferably 0.5 to 0.9.

  Unlike the 2nd and 3rd positions, the glucose unit constituting the cellulose acylate has a highly reactive primary hydroxyl group, which is a process for producing cellulose acylate using sulfuric acid as a catalyst. To preferentially form sulfate esters. For this reason, in the esterification reaction of cellulose, by increasing the amount of catalytic sulfuric acid, the average substitution degree at the 2nd and 3rd positions of the glucose unit can be increased as compared with the ordinary cellulose acylate. Furthermore, if the cellulose is tritylated as necessary, the hydroxyl group at the 6-position of the glucose unit can be selectively protected. Therefore, the tritylation protects the hydroxyl group at the 6-position, and after esterification, the trityl group (protection) By deprotecting the group), the average degree of substitution at the 2nd and 3rd positions can be increased rather than the 6th position of the glucose unit. Specifically, cellulose acylate produced by the method described in JP-A No. 2005-281645 can also be preferably used.

  An example of a method for producing cellulose acylate is shown below. 100 parts by weight of a cotton linter was crushed as a cellulose raw material, 40 parts by weight of acetic acid was added, and pretreatment activation was performed at 36 ° C. for 20 minutes. Thereafter, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride and 350 parts by mass of acetic acid were added, and esterification was performed at 36 ° C. for 120 minutes. After neutralization with 11 parts by mass of a 24% magnesium acetate aqueous solution, saponification aging was carried out at 63 ° C. for 35 minutes to obtain acetylcellulose. This was stirred for 160 minutes at room temperature using a 10-fold acetic acid aqueous solution (acetic acid: water = 1: 1 (mass ratio)), then filtered and dried to obtain purified acetylcellulose having an acetyl substitution degree of 2.75. . This acetylcellulose had Mn of 92000, Mw of 156000, and Mw / Mn of 1.7. Similarly, cellulose acylates having different degrees of substitution and molecular weight distribution (Mw / Mn) can be synthesized by adjusting the esterification conditions (temperature, time, stirring) and hydrolysis conditions of cellulose acylate.

  The synthesized cellulose acylate is preferably purified to remove low molecular weight components, or to remove components having no acetylation or low acetylation by filtration.

  In the case of mixed acid cellulose acylate, it can be obtained by the method described in JP-A-10-45804.

  The cellulose acylate content in the first polarizing plate protective film is preferably 60 to 95 parts by weight, more preferably 70 to 90 parts by weight with respect to 100 parts by weight of the total amount of the first polarizing plate protective film. It is.

(Acryloyl compounds)
The first polarizing plate protective film has the following general formula (1):

The acryloyl type compound represented by these is included.

In the general formula (1), R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, particularly preferably a hydrogen atom or a methyl group. .

Moreover, in General formula (1), R < ₁₂ > and R < ₁₃ > represent a C1-C8 alkyl group each independently, and may have a linear structure, a branched structure, or a ring structure. R ₁₂ and R ₁₃ are preferably a structure represented by “* —C (CH ₃ ) ₂ —R ′” containing a quaternary carbon (* represents a connecting site to an aromatic ring, and R ′ has 1 carbon atom) Represents an alkyl group of ˜5).

R ₁₂ is more preferably a tert-butyl group, a tert-amyl group or a tert-octyl group. R ₁₃ is more preferably a tert-butyl group or a tert-amyl group. As the compound represented by the general formula (1), commercially available products include “Sumilizer GM, Sumilizer GS” (both trade names, manufactured by Sumitomo Chemical Co., Ltd.) and the like.

  Specific examples (I-1 to I-18) of the compound represented by the general formula (1) are illustrated below, but the present invention is not limited thereto.

  As for the acryloyl-type compound represented by the said General formula (1), only 1 type may be used independently and 2 or more types may be used together. Further, the compounding amount of the compound is appropriately selected within a range not impairing the object of the present invention, but preferably 0.1 to 10.0% by mass with respect to 100% by mass of the total amount of the first polarizing plate protective film. More preferably, it is 0.2-5.0 mass%, More preferably, it is 0.3-3.0 mass%.

(Halogen content)
The first polarizing plate protective film is also characterized in that the halogen element content is 50 to 2000 ppm by mass with respect to 100% by mass of the total amount of the film. By containing such a small amount of halogen element, the above-described acryloyl compound further enhances the action of suppressing the polarizer deterioration, and the polarizer deterioration can be suppressed to a minimum even in the thinned polarizing plate. It is. On the other hand, when the halogen element content in the first polarizing plate protective film exceeds 2000 mass ppm, a large amount of halogen harmful to the environment is released when the member is discarded. Here, as the value of the halogen element content, a value measured by the method described in the column of Examples described later is adopted. The halogen element content is the total content of a plurality of halogen elements when they are contained. The halogen element content in the first polarizing plate protective film is preferably 10 to 800 ppm by mass, more preferably 10 to 500 ppm by mass. In a more preferred embodiment, the first polarizing plate protective film preferably contains no halogen element other than chlorine. That is, preferably the halogen element content is equal to the chlorine content. There is no restriction | limiting in particular about the specific method of controlling the halogen element content in a 1st polarizing plate protective film to the value within the range mentioned above, A conventionally well-known knowledge can be referred suitably.

<Additive>
In the polarizing plate according to the present embodiment, the first polarizing plate protective film may contain various additives. Hereinafter, although the example of the additive which may be contained in a 1st polarizing plate protective film is demonstrated, it is not limited only to the following form.

(Plasticizer)
In the polarizing plate according to this embodiment, the first polarizing plate protective film preferably contains a plasticizer for the purpose of improving mechanical strength and water resistance. The plasticizer is preferably a compound having an octanol-water partition coefficient (log P) of 0 or more and less than 7. The plasticizer needs to have an appropriate solubility corresponding to the resin, but if the log P is 0 or more in the first polarizing plate protective film, the water solubility of the compound does not become too high, and the occurrence of orientation disorder occurs. If logP is less than 7, the compound has a certain degree of orientation and a desired phase difference can be obtained.

-Polyester compound As the plasticizer, it is preferable to use a polyester compound (polyester plasticizer).

  The polyester compound is not particularly limited. For example, a polymer in which a terminal obtained by a condensation reaction of dicarboxylic acid or an ester-forming derivative thereof and glycol becomes a hydroxy group (hydroxyl group) (hereinafter referred to as “polyester polyol”). Alternatively, a polymer in which the terminal hydroxy group of the polyester polyol is sealed with a monocarboxylic acid (hereinafter referred to as “end-capped polyester”) can be used. The ester-forming derivative as used herein refers to an esterified product of dicarboxylic acid, dicarboxylic acid chloride, and dicarboxylic acid anhydride.

  By using the polyester polyol or the end-capped polyester, the film can be further prevented from peeling and wrinkling over time. The reason why such an effect is obtained is not clear, but the above-mentioned compound is oriented in the surface direction when the cellulose ester film is formed, and the deformation stress at the time of moisture absorption is dispersed in the thickness direction. Estimated that wrinkles were suppressed.

  Specifically, an ester compound represented by the following general formula (2) can be preferably used as the polyester compound.

  In the formula, B is a hydroxy group, a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, and G is an alkylene glycol residue having 2 to 18 carbon atoms or an aryl glycol residue or carbon having 6 to 12 carbon atoms. An oxyalkylene glycol residue having 4 to 12 carbon atoms, A is an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 16 carbon atoms, and n is an integer of 1 or more .

  In the above general formula (2), a compound in which B is a hydroxy group corresponds to a polyester polyol, and a compound in which B is a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue corresponds to an end-capped polyester. In the present invention, it is particularly preferable that the first polarizing plate protective film contains a compound (terminal-capped polyester) in which B is a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue.

  The polyester compound represented by the general formula (2) is obtained by the same reaction as a normal polyester plasticizer.

  As the aliphatic monocarboxylic acid component of the polyester compound represented by the general formula (2), for example, an aliphatic monocarboxylic acid having 3 or less carbon atoms is preferable, and examples include acetic acid, propionic acid, and butanoic acid (butyric acid). These can be used individually or as a mixture of two or more.

  Examples of the benzene monocarboxylic acid component of the polyester compound represented by the general formula (2) include, for example, benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal There are propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, aliphatic acid and the like, and these can be used singly or as a mixture of two or more. In particular, it is preferable to contain benzoic acid or p-toluic acid.

  Examples of the alkylene glycol component having 2 to 18 carbon atoms of the polyester compound represented by the general formula (2) include ethylene glycol, 1,2-propanediol (1,2-propylene glycol), 1,3-propanediol (1 , 3-propylene glycol), 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butane Diol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol, 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-buty 2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol , 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds. Of these, ethylene glycol, diethylene glycol, 1,2-propylene glycol, and 2-methyl 1,3-propanediol are preferable, and ethylene glycol, diethylene glycol, and 1,2-propylene glycol are more preferable.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester. More preferably, it is C2-C6 alkylene glycol, More preferably, it is C2-C4 alkylene glycol.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (2) include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Glycol can be used as one kind or a mixture of two or more kinds.

  Examples of the aryl glycol having 6 to 12 carbon atoms of the polyester compound represented by the general formula (2) include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, cyclohexanediethanol, and 1,4-benzenedimethanol. And these glycols can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester compound represented by the general formula (2) include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. There are acids and the like, and these are used as one kind or a mixture of two or more kinds, respectively.

  Examples of the aryl dicarboxylic acid component having 6 to 16 carbon atoms of the polyester compound represented by the general formula (2) include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, There are 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,6-anthracenedicarboxylic acid and the like. The aryl dicarboxylic acid may have a substituent on the aromatic ring. Examples of the substituent include a linear or branched alkyl group having 1 to 6 carbon atoms, an alkoxy group, and an aryl group having 6 to 12 carbon atoms.

  When B is a hydroxy group, that is, when the polyester compound is a polyester polyol, in the general formula (2), A is preferably an aryl dicarboxylic acid residue having 10 to 16 carbon atoms. For example, a dicarboxylic acid having an aromatic cyclic structure such as a benzene ring structure, a naphthalene ring structure, or an anthracene ring structure can be used. Specific examples of the aryl dicarboxylic acid component include orthophthalic acid, isophthalic acid, terephthalic acid, Mentioning 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,6-anthracenedicarboxylic acid Can do. Preferred are 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,8-naphthalenedicarboxylic acid, and more preferred is 2 , 3-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, particularly preferably 2,6-naphthalenedicarboxylic acid. These can be used alone or in combination of two or more.

  It is important that the polyester polyol has a carbon number average of 10 to 16 in the dicarboxylic acid used as a raw material. If the average carbon number of the dicarboxylic acid is 10 or more, the dimensional stability of the cellulose ester film is excellent. If the average carbon number is 16 or less, the compatibility with the cellulose ester is excellent, and the cellulose ester film is transparent. The property is remarkably excellent. As dicarboxylic acid, Preferably the average of carbon number is 10-14, More preferably, the average of carbon number is 10-12.

  The average carbon number of the dicarboxylic acid of the polyester polyol means the carbon number of the dicarboxylic acid when the polyester polyol is polymerized using a single dicarboxylic acid, but the polyester using two or more kinds of dicarboxylic acids. When polymerizing a polyol, it means the sum of the products of the carbon number of each dicarboxylic acid and the molar fraction of the dicarboxylic acid.

  When the average number of carbon atoms is 10 to 16, the aryl dicarboxylic acid having 10 to 16 carbon atoms and another dicarboxylic acid can be used in combination.

  The dicarboxylic acid that can be used in combination is preferably a dicarboxylic acid having 4 to 9 carbon atoms. For example, succinic acid, glutaric acid, adipic acid, maleic acid, orthophthalic acid, isophthalic acid, terephthalic acid, esterified products thereof, and acid A chloride and an acid anhydride can be mentioned.

Although the specific example of dicarboxylic acid whose carbon number of polyester polyol is 10-16 below is shown, this invention is not limited to this.
(1) 2,6-naphthalenedicarboxylic acid (2) 2,3-naphthalenedicarboxylic acid (3) 2,6-anthracenedicarboxylic acid (4) 2,6-naphthalenedicarboxylic acid: succinic acid (75: 25-99: 1 molar ratio)
(5) 2,6-naphthalenedicarboxylic acid: terephthalic acid (50:50 to 99: 1 molar ratio)
(6) 2,3-naphthalenedicarboxylic acid: succinic acid (75:25 to 99: 1 molar ratio)
(7) 2,3-naphthalenedicarboxylic acid: terephthalic acid (50:50 to 99: 1 molar ratio)
(8) 2,6-anthracene dicarboxylic acid: succinic acid (50:50 to 99: 1 molar ratio) (9) 2,6-anthracene dicarboxylic acid: terephthalic acid (25:75 to 99: 1 molar ratio)
(10) 2,6-naphthalenedicarboxylic acid: adipic acid (67:33 to 99: 1 molar ratio)
(11) 2,3-naphthalenedicarboxylic acid: adipic acid (67:33 to 99: 1 molar ratio)
(12) 2,6-anthracene dicarboxylic acid: adipic acid (40:60 to 99: 1 molar ratio)
As the polyester compound that can be used in the present invention, a compound having an octanol-water partition coefficient (logP (B)) of 0 or more and less than 7 is used in addition to the polyester polyol described above, from the viewpoint of water solubility and orientation of the compound. It is also preferable.

  The polyester polyol is a dicarboxylic acid or an ester-forming derivative thereof (a component corresponding to A in the general formula (2)) and a glycol (a component corresponding to G in the general formula (2)) as necessary as an esterification catalyst. In the presence of, for example, in a temperature range of 180 to 250 ° C., for 10 to 25 hours by an esterification reaction by a well-known and conventional method.

  In conducting the esterification reaction, a solvent such as toluene or xylene may be used, but a method using no solvent or glycol used as a raw material as a solvent is preferable.

  As the esterification catalyst, for example, tetraisopropyl titanate, tetrabutyl titanate, p-toluenesulfonic acid, dibutyltin oxide and the like can be used. The esterification catalyst is preferably used in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the total amount of dicarboxylic acids or their ester-forming derivatives.

  The molar ratio when the dicarboxylic acid or their ester-forming derivative is reacted with the glycol must be a molar ratio in which the terminal group of the polyester becomes a hydroxy group (hydroxyl group). Therefore, the dicarboxylic acid or their ester-forming derivative The glycol is 1.1 to 10 moles per mole. Preferably, the glycol is 1.5 to 7 moles per mole of the dicarboxylic acid or their ester-forming derivatives, and more preferably the glycol is one mole of the dicarboxylic acid or their ester-forming derivatives. 2 to 5 moles.

  The terminal group of the polyester polyol is a hydroxy group (hydroxyl group), but the polyester polyol may contain a carboxy group-terminated compound as a by-product. However, the carboxy group terminal in the polyester polyol lowers the humidity stability, so that the content is preferably low. Specifically, the acid value is preferably 5.0 mgKOH / g or less, more preferably 1.0 mgKOH / g or less, and particularly preferably 0.5 mgKOH / g or less.

  The “acid value” here refers to the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxy group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070: 1992.

  The polyester polyol preferably has a hydroxy (hydroxyl) value (OHV) in the range of 35 mg / g to 220 mg / g. The hydroxy (hydroxyl group) value here means the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to a hydroxy group (hydroxyl group) when OH group contained in 1 g of a sample is acetylated. . Acetic anhydride is used to acetylate OH groups in the sample, and unused acetic acid is titrated with a potassium hydroxide solution, and obtained from the difference from the initial titration value of acetic anhydride.

  The polyester polyol preferably has a hydroxy group (hydroxyl group) content of 70% or more. When the hydroxy group (hydroxyl group) content is low, the compatibility between the polyester polyol and the cellulose ester is lowered. For this reason, the hydroxy group (hydroxyl group) content is preferably 70% or more, more preferably 90% or more, and most preferably 99% or more.

  In the present invention, a compound having a hydroxy group (hydroxyl group) content of 50% or less is not included in the polyester polyol because one of the end groups is substituted with a group other than the hydroxy group (hydroxyl group).

  The hydroxy group (hydroxyl group) content can be determined by the following formula (A).

  The polyester polyol preferably has a number average molecular weight within a range of 300 to 3,000, and more preferably has a number average molecular weight of 350 to 2,000.

  Moreover, it is preferable that the dispersion degree of the molecular weight of the polyester polyol based on this invention is 1.0-3.0, and it is still more preferable that it is 1.0-2.0. If the degree of dispersion is within the above range, a polyester polyol having excellent compatibility with the cellulose ester can be obtained.

  The polyester polyol preferably contains 50% or more of a component having a molecular weight of 300 to 1800. By setting the number average molecular weight within the above range, the compatibility can be greatly improved.

  As a method of controlling the number average molecular weight, the degree of dispersion, and the component content within the above preferred ranges, 2 to 5 mol of glycol is used per 1 mol of dicarboxylic acid or an ester-forming derivative thereof, and unreacted glycol is decompressed A method of distilling off is preferred. The temperature at which the solvent is distilled off under reduced pressure is preferably 100 to 200 ° C, more preferably 120 to 180 ° C, and particularly preferably 130 to 170 ° C. The degree of reduced pressure when distilled off under reduced pressure is preferably 0.1 to 500 Torr, more preferably 0.5 to 200 Torr, and most preferably 1 to 100 Torr.

  The number average molecular weight (Mn) and dispersity of the polyester compound (polyester polyol, end-capped polyester) can be measured using gel permeation chromatography (GPC).

  An example of measurement conditions is as follows, but is not limited to this, and an equivalent measurement method can be used.

Solvent: Tetrahydrofuran (THF)
Column: TSKgel G2000HXL (Tosoh Co., Ltd. uses two connected)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Flow rate: 1.0ml / min
Calibration curve: A calibration curve by PStQuick F (manufactured by Tosoh Corporation) is used.

  When B is a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, that is, when the polyester compound is an end-capped polyester, in the general formula (2), preferable A is a residue of adipic acid. Groups, phthalic acid residues and the like.

  In addition, A in the general formula (2) preferably includes both an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms and an aryl dicarboxylic acid residue having 6 to 16 carbon atoms, and more preferably an adipic acid residue. Includes both groups and phthalic acid residues.

  The end-capped polyester may be a monocarboxylic acid residue at least one of the two end groups B. That is, one of the two terminal groups B may be a hydroxy group and the other may be a monocarboxylic acid residue. However, it is preferable that both of the two terminal groups B are monocarboxylic acid residues.

  As the terminal group B, the benzene monocarboxylic acid residue and the aliphatic monocarboxylic acid residue described above can be used, and the benzene monocarboxylic acid residue is preferable. That is, it is preferably an aromatic terminal polyester.

  The above end-capped polyester includes glycol (a component corresponding to G in the general formula (2)), a dicarboxylic acid or an ester-forming derivative thereof (a component corresponding to A in the general formula (2)) and a monocarboxylic acid or These ester-forming derivatives (components corresponding to B in the general formula (2)) can be obtained by an esterification reaction. For example, JP-A-2011-52205, JP-A-2008-69225, It can be synthesized with reference to Kaikai 2008-88292, JP-A 2008-115221 and the like.

  The ester compound described above is a mixture having a distribution in molecular weight and molecular structure at the time of its synthesis. Among them, preferred components of the present invention, for example, phthalic acid residue and adipic acid residue as A in the general formula (2) are used. What is necessary is just to have at least 1 type of polyester compound which has group.

  The end-capped polyester has a number average molecular weight of preferably 300 to 2000, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxy (hydroxyl group) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxy (hydroxyl group) value is 15 mgKOH / g or less. is there.

  Although the specific compound of the ester type compound represented by General formula (2) which can be used for this invention below is shown, this invention is not limited to this.

  The polarizing plate which concerns on this form WHEREIN: It is preferable that a 1st polarizing plate protective film contains a polyester compound 0.1-30 mass% with respect to 100 mass% of the total amount of a polarizing plate protective film, Especially, it is 0. It is preferable to contain 5-10 mass%.

-Other plasticizer In the polarizing plate which concerns on this form, it replaces with the said polyester compound, or in addition to this, the 1st polarizing plate protective film can contain another plasticizer. Preferably, (a-1) a polyhydric alcohol ester plasticizer, (a-2) a polycarboxylic acid ester plasticizer, (a-3) a glycolate plasticizer, (a-4) a phthalate ester It is selected from plasticizers, (a-5) fatty acid ester plasticizers, (a-6) phosphate ester plasticizers, and the like.

  (A-1) The polyhydric alcohol ester plasticizer is an ester compound of a polyhydric alcohol represented by the following general formula (3).

In the formula, R ₁ represents an n-valent organic group, and n represents a positive integer of 2 or more.

  Preferred examples of the polyhydric alcohol include ethylene glycol, propylene glycol, trimethylolpropane, and pentaerythritol.

  As monocarboxylic acid used for polyhydric alcohol ester, well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. In particular, benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  In addition, trimethylolpropane triacetate, pentaerythritol tetraacetate and the like are also preferably used. It is also preferable to use the ester compound (A) represented by the general formula (I) described in JP-A-2008-88292.

  (A-2) The polyvalent carboxylic acid ester compound is composed of an ester of a divalent or higher valent, preferably a divalent to 20 valent polyvalent carboxylic acid and an alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 2 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (4).

In the formula, R ₂ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, the COOH group is a carboxyl group, and the OH group is alcoholic or It is a phenolic hydroxyl group.

  Examples of preferable polyvalent carboxylic acids include the following. Divalent or higher aromatic polyvalent carboxylic acids or derivatives such as phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid Aliphatic polycarboxylic acids such as fumaric acid, maleic acid and tetrahydrophthalic acid, and oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used.

  Known alcohols and phenols can be used as the alcohol used in the polycarboxylic acid ester compound. For example, an aliphatic saturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used.

  It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used. Examples of phenol include phenol, paracresol, dimethyl Phenol etc. can be used individually or in combination of 2 or more types.

  It is also preferable to use the ester compound (B) represented by the general formula (II) described in JP-A-2008-88292.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric carboxylic acid ester compound, It is preferable that it is the range of molecular weight 300-1000, and it is more preferable that it is the range of 350-750.

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

  The acid value of the polyvalent carboxylic acid ester compound is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less.

  The acid value means the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxyl group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070: 1992.

  (A-3) The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of the alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate and the like.

  Examples of the (a-4) phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like.

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

  (A-5) Fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and the like.

  Examples of the (a-6) phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

  These plasticizers (including polyester compounds) are preferably contained in an amount of 0.1 to 30% by mass, particularly 0.5 to 10% by mass, with respect to 100% by mass of the total amount of the polarizing plate protective film. % Is preferably included.

<Hydrolysis inhibitor (sugar ester compound)>
It is also a preferable form that the first polarizing plate protective film contains a hydrolysis inhibitor. The hydrolysis inhibitor is not particularly limited, but those having an octanol-water partition coefficient (log P) of 7 or more and less than 11 are preferred. If log P is above, the hydrolysis preventing effect is sufficiently ensured, and if log P is less than 11, compatibility with cellulose acylate is sufficiently ensured. As a result, generation of bleed out due to wet heat is prevented. The

  As the hydrolysis inhibitor, for example, a mixture of ester compounds in which at least one of a pyranose structure or furanose structure is 1 to 12 and a part of the OH group of the structure is esterified can be preferably used.

  The ratio of esterification of an ester compound in which at least one of the pyranose structure or furanose structure is 1 to 12 and all or part of the OH groups in the structure is esterified is present in the pyranose structure or furanose structure. It is preferable that it is 70% or more of the OH group.

  In the present invention, the above ester compounds are collectively referred to as sugar ester compounds.

  Examples of the ester compound used in the present invention include the following, but the present invention is not limited to these.

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

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH group in the pyranose structure or furanose structure is not particularly limited, and is a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic A monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

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

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratrumic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid and naphthylic acid are particularly preferable.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or furanose structure according to the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ , and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group further have a substituent. May be. Oligosaccharides can also be produced by the same method as the ester compound of the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

  The polarizing plate which concerns on this form WHEREIN: It is preferable that a 1st polarizing plate protective film contains 0.5-30 mass% of hydrolysis inhibitors with respect to 100 mass% of total amounts of a polarizing plate protective film, especially 2 It is preferable to contain -15 mass%.

<Ultraviolet absorber>
The polarizing plate which concerns on this form WHEREIN: The 1st polarizing plate protective film can also contain a ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, Preferably it is 2% or less.

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

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

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

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

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

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  Note that, as described above, in the first polarizing plate protective film, the halogen element content is controlled to a value within a predetermined range. Therefore, when the first polarizing plate protective film contains an ultraviolet absorber, the ultraviolet absorber preferably does not contain a halogen element. Moreover, in other preferable embodiment, a 1st polarizing plate protective film does not contain a ultraviolet absorber. In summary, in the present invention, it can be said that the first polarizing plate protective film preferably does not contain a halogen element-containing ultraviolet absorber.

  In the case where the ultraviolet absorber is not dissolved in an organic solvent such as an inorganic powder, a dissolver or a sand mill is used in the organic solvent and cellulose ester to be dispersed and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but is preferably 0.5 to 10% by mass relative to 100% by mass of the total amount of the first polarizing plate protective film. 0.6-4 mass% is more preferable.

<Antioxidant>
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the polarizing plate protective film may be deteriorated.

  The antioxidant has a role of delaying or preventing the polarizing plate protective film from being decomposed by, for example, the residual solvent amount of halogen in the polarizing plate protective film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to contain in 1 polarizing plate protective film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  1 mass ppm-1.0 mass% are preferable with respect to 100 mass% of whole quantity of a 1st polarizing plate protective film, and, as for content of these antioxidants, 10-1000 mass ppm is further more preferable. In addition, although the acryloyl type compound represented by the general formula (1) described above may also function as an antioxidant, in the present invention, the concept of “antioxidant” includes the general formula ( The acryloyl compound represented by 1) is not included.

<Fine particles>
In the polarizing plate according to this embodiment, it is preferable to add fine particles to the first polarizing plate protective film in order to impart slipperiness.

  The average primary particle diameter of the fine particles to be added is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

  These fine particles preferably form secondary particles having a particle size of 0.1 to 5 μm and are contained in the film, and the preferable average secondary particle size is 0.1 to 2 μm, more preferably 0.2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

  The average primary particle diameter of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification of 500,000 to 2,000,000 times), observing 100 particles, measuring the particle diameter, and measuring the average value. Is the average primary particle size.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  Silicon dioxide fine particles having an average primary particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen burned in air at 1000 to 1200 ° C. Can be obtained. For example, it is marketed with the brand name of Aerosil 200V and Aerosil R972V (above, Nippon Aerosil Co., Ltd. product), and can use them.

  The apparent specific gravity described above is calculated by the following equation by taking a certain amount of silicon dioxide fine particles in a graduated cylinder, measuring the weight at this time.

  Examples of the method for preparing the fine particle dispersion used in the present invention include the following three types.

<< Preparation Method A >>
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

<< Preparation Method B >>
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose acylate is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

<< Preparation Method C >>
Add a small amount of cellulose acylate to the solvent and dissolve with stirring. Fine particles are added to this and dispersed by a disperser. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  Preparation method A is excellent in dispersibility of silicon dioxide fine particles, and preparation method C is excellent in that silicon dioxide fine particles are difficult to re-aggregate. Among them, the preparation method B described above is a preferable preparation method that is excellent in both dispersibility of the silicon dioxide fine particles and difficulty in reaggregation of the silicon dioxide fine particles.

《Distribution method》
The concentration of silicon dioxide when the silicon dioxide fine particles are mixed with a solvent and dispersed is preferably 5% by mass to 30% by mass, more preferably 10% by mass to 25% by mass, and most preferably 15% by mass to 20% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  The addition amount of silicon dioxide fine particles relative to cellulose ester is preferably 0.01 parts by mass to 5.0 parts by mass, and more preferably 0.05 parts by mass to 1.0 part by mass with respect to 100 parts by mass of cellulose ester. Preferably, 0.1 mass part-0.5 mass part is the most preferable. The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the less aggregates.

  As the disperser, a normal disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersing silicon dioxide fine particles, a medialess disperser is preferred because of its low haze. Examples of the media disperser include a ball mill, a sand mill, and a dyno mill.

  Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. The high pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

  When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm.

  More preferably, it is 19.613 MPa or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable.

  Examples of the high-pressure dispersion apparatus include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and a Manton Gorin type high-pressure dispersion apparatus such as a homogenizer manufactured by Izumi Food Machinery. UHN-01 manufactured by Sanwa Machinery Co., Ltd.

  In addition, casting a dope containing fine particles so as to be in direct contact with the casting support is preferable because a film having high slip properties and low haze can be obtained.

(Physical properties and optical properties of the first polarizing plate protective film)
The thickness of the 1st polarizing plate protective film which concerns on this form is not restrict | limited in particular, If it is about 10-60 micrometers normally, Preferably it is 15-35 micrometers, Most preferably, it is 20-30 micrometers. According to the present invention, even when a polarizing plate is configured using such a thin polarizing plate protective film, the deterioration of the polarizer in a high-temperature and high-humidity environment is suppressed to a minimum. A suitable technique can be provided as a polarizing plate that can cope with thinning of a display device or the like.

Moisture permeability of the first polarizing plate protective film according to the present embodiment, 40 ° C., preferably 10~1200g ^/ m 2 · 24h at 90% RH, preferably more ^{20~1000g / m 2 · 24h, 20~850g} / m ² · 24 h is particularly preferable. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The breaking elongation of the first polarizing plate protective film according to this embodiment is preferably 10 to 80%, and more preferably 20 to 50%.

  The visible light transmittance of the first polarizing plate protective film according to this embodiment is preferably 90% or more, and more preferably 93% or more.

  The haze of the first polarizing plate protective film according to this embodiment is preferably less than 1%, and particularly preferably 0 to 0.1%.

  The retardation value Re represented by the following formula of the first polarizing plate protective film according to this embodiment is preferably 0 to 10 nm, and more preferably 0 to 5 nm. Moreover, retardation value Rth becomes like this. Preferably it is 5-60 nm, More preferably, it is 10-40 nm. In order to obtain these retardation values Re and Rth, it is preferable to control the refractive index by adjusting the conditions of the stretching operation in producing the first polarizing plate protective film.

  In the formula, Re is a retardation value in the film plane, Rth is a retardation value in the film thickness direction, nx is a refractive index in the slow axis direction in the film plane, ny is a refractive index in the fast axis direction in the film plane, nz Represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.

  The refractive index can be obtained at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH or KOBRA-WR (manufactured by Oji Scientific Instruments).

<Second polarizing plate protective film>
The polarizing plate which concerns on this form WHEREIN: The 2nd polarizing plate protective film is arrange | positioned on the surface on the opposite side to the 1st polarizing plate protective film of a polarizer.

  There is no restriction | limiting in particular about the specific form of a 2nd polarizing plate protective film. For example, the same thing as the 1st polarizing plate protective film mentioned above may be used for the 2nd polarizing plate protective film. The second polarizing plate protective film may be a conventionally known polarizing plate protective film. As a conventionally well-known polarizing plate protective film, a commercially available cellulose acylate film can be used. As a commercially available cellulose acylate film, for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UA, KC4UY, KC4UE, KC8UE, KC8UY-HA, HC8UY-HA, KC8UY-HA, KC8UY-HA, KC8UY-HA RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used. Moreover, a cyclic olefin resin film, a polycarbonate-type resin film, etc. may be used as another conventionally well-known polarizing plate protective film.

  However, in a preferred embodiment, the second polarizing plate protective film contains cellulose acylate in the same manner as the first polarizing plate protective film. By setting it as such a structure, the advantage that the water resistance of a polarizing plate can be improved is acquired.

  Alternatively, a polarizing plate protective film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal is used as the second polarizing plate protective film. It is also preferable. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

[Configuration of polarizing plate]
(Thickness of polarizing plate)
The thickness of the polarizing plate which concerns on this form is 50-100 micrometers, Preferably it is 50-130 micrometers, More preferably, it is 55-110 micrometers. Even if it is a case where it is the structure which concerns on this form as the thickness of a polarizing plate is less than 50 micrometers, deterioration of a polarizer in a high temperature, high humidity environment cannot fully be suppressed. On the other hand, when the thickness of the polarizing plate exceeds 100 μm, not only does it not sufficiently contribute to the thinning of the display device and the like, but also there is a problem that curling occurs in the manufactured polarizing plate. If the display device is configured using the polarizing plate in which the curl is generated as described above, a failure such as color unevenness or luminance unevenness may occur when the panel of the display device is turned on, which is not preferable.

  In addition, in addition to each thickness of a polarizer and the 1st and 2nd polarizing plate protective film, in addition to the thickness of a polarizing plate, the thickness of a polarizing plate WHEREIN: When various functional layers mentioned later are arrange | positioned on the surface of a polarizing plate protective film Also includes the thickness of the functional layer.

(Functional layer)
In the polarizing plate according to the present embodiment, various functional layers for improving the quality of the display device may be arranged on either one of the first and second polarizing plate protective films. In this case, the polarizing plate is used in such a manner that the side on which the functional layer is disposed is located on the side far from the panel of the display device.

  As such a functional layer, for example, scratch resistance (clear hard coat (CHC)), antireflection (antireflection (AR)), antiglare (antiglare (AG)), low reflection (low reflection (LR)), A film containing a known functional layer as a display as a constituent for dust adhesion prevention, brightness improvement, antistatic, antifouling, and back coating can be used.

  In preferable embodiment of this invention, a clear hard-coat (CHC) layer is arrange | positioned on the surface of either one of a 1st or 2nd polarizing plate protective film. In this case, it is more preferable that the clear hard coat (CHC) layer is disposed on the surface of the first polarizing plate protective film. By setting it as such a structure, deterioration of a polarizing plate in a high temperature, high humidity environment can be prevented further.

  When such a clear hard coat (CHC) layer is disposed, the clear hard coat (CHC) layer preferably contains an ultraviolet absorber. There is no restriction | limiting in particular about the specific form of the ultraviolet absorber which can be contained in a clear hard-coat (CHC) layer, The form similar to what was mentioned above as what can be contained in a 1st polarizing plate protective film may be employ | adopted. However, the ultraviolet absorber contained in the clear hard coat (CHC) layer is not particularly problematic even if it is a halogen element-containing ultraviolet absorber, so that the ultraviolet absorber is contained in the first polarizing plate protective film. There is an advantage that options for additives can be widely secured.

  The polarizing plate having the above-described configuration can be configured by further bonding a protective film on one surface 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 display panel. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a panel, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

≪Production method of polarizing plate≫
There is no restriction | limiting in particular about the manufacturing method of the polarizing plate which concerns on this form, A conventionally well-known knowledge can be referred suitably.

  In order to produce the polarizing plate according to the present embodiment, it is usually sufficient to prepare and prepare a polarizer and first and second polarizing plate protective films and bond them together.

(Production method of first polarizing plate protective film)
In the polarizing plate of the present embodiment, the first polarizing plate protective film is preferably a film produced by a solution casting method or a film produced by a melt casting method. it can. However, it is preferably by the solution casting method. Therefore, below, the manufacturing method of the 1st polarizing plate protective film by a solution casting method is mentioned as an example, and is demonstrated.

  Production of the first polarizing plate protective film by the solution casting method in the production method according to the embodiment includes, for example, cellulose acylate, an acryloyl compound represented by the general formula (1) and a solvent, and other as necessary A step of preparing a dope containing the additive of: a step of casting the dope onto an endless metal support that moves indefinitely, a step of drying the cast dope as a web, a step of peeling from the metal support, stretching Or it is performed by the process of holding width, the process of drying further, and the process of winding up the finished film.

  First, the process for preparing the dope will be described. The concentration of cellulose acylate in the dope is preferable because it can reduce the drying load after casting on the metal support, but if the concentration of cellulose acylate is too high, the load during filtration increases and the filtration accuracy Becomes worse. The concentration for achieving both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass. Moreover, about the acryloyl type compound represented by General formula (1), a polyester plasticizer, and another additive, it is preferable to batch-add a specified quantity to a dope preparation kettle.

  The solvent used for the preparation of the dope may be used alone or in combination of two or more, but it is preferable in terms of production efficiency to use a mixture of a good solvent and a poor solvent of cellulose acylate, A larger amount of good solvent is preferred from the viewpoint of the solubility of cellulose acylate.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose acylate to be used independently is defined as a good solvent, and what swells or does not melt | dissolve independently is defined as a poor solvent. Therefore, the good solvent and the poor solvent change depending on the acyl group substitution degree of cellulose acylate.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water is contained in dope.

  In the manufacturing method of the polarizing plate which concerns on this invention, it is preferable that a halogen-type solvent is included as a solvent contained in dope. “Halogen-based solvent” means a solvent containing a halogen atom. Of these, the organic halogen compounds described above are preferred as good solvents. As the organic halogen compound, methylene chloride, chloroform and the like are more preferable, and methylene chloride is most preferable. As described above, when the first polarizing plate protective film is produced by the solution casting method using a halogen-based solvent as a solvent contained in the dope, a small amount of residual solvent is present, so that a separate operation is not required. In the manufactured first polarizing plate protective film, the above-mentioned predetermined amount of halogen element content can be achieved.

  Moreover, the solvent used for melt | dissolution of a cellulose acylate collect | recovers the solvent removed from the film by drying at the film-forming process, and this can be reused.

  There may be a trace amount of additives added to the cellulose acylate in the recovered solvent, but even if these are included, they can be reused preferably and can be purified and reused if necessary. It can also be used.

  As a method for dissolving cellulose acylate when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and does not boil under pressure, in order to prevent the formation of massive undissolved materials called gels and mamacos.

  In addition, a method in which cellulose acylate is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

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

  The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of cellulose acylate, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and further preferably 70 to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

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

  Next, this cellulose acylate solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose acylate by filtration.

A bright spot foreign material is placed in a crossed Nicols state with two polarizing plates, a cellulose acylate film or the like is placed between them, light is applied from one polarizing plate, and observation is performed from the other polarizing plate. The number of bright spots having a diameter of 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm 2. ² or less, more preferably 50 pieces / m ² or less, and particularly preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

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

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and even more preferably 45 to 55 ° C.

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

  Next, dope casting will be described.

  The metal support used in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the drying speed of the web can be increased. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  The manufacturing method of the 1st polarizing plate protective film which concerns on this form includes the process of extending | stretching, after drying and peeling the film obtained by casting dope on a support body.

  In order for the 1st polarizing plate protective film to show favorable planarity, 10-150 mass% is preferable, and, as for the residual solvent amount at the time of peeling a web from a metal support body, More preferably, it is 20-40 mass% or 60. It is -130 mass%, Most preferably, it is 20-30 mass% or 70-120 mass%.

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

  Where M is the mass of a sample taken during or after production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the first polarizing plate protective film, the web is preferably peeled off from the metal support and further dried to make the residual solvent amount 1% by mass or less, more preferably 0.1% by mass. Or less, particularly preferably 0 to 0.01% by mass or less.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

  The stretching operation for producing the first polarizing plate protective film can be sequentially or simultaneously stretched in the MD direction (casting direction or longitudinal direction) and the TD direction (width direction) of the film. The draw ratio in the biaxial direction perpendicular to each other may be about 0 to 10% in the MD direction and about 5 to 40% in the TD direction.

  In particular, in the present invention, the film is stretched by 10 to 30% in the TD direction, the stretching temperature is 130 to 190 ° C., the in-plane retardation Re after stretching is 0 to 10 nm, and the retardation Rth in the thickness direction is 15 to 15%. When adjusted to a range of 40 nm, the haze stability is significantly improved.

  In particular, when a stretching treatment is performed at a relatively high temperature of 180 to 230 ° C., which is a relatively high temperature in the presence of a polyester compound (plasticizer), the polyester compound (plasticizer) coats around the matting agent (fine particles) and more aggregates. Is less likely to occur. At this time, the surface coating ability is higher when the molecular weight of the polyester compound (plasticizer) is smaller, and the coating ability is higher when the dicarboxylic acid group is a mixture of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid.

  Furthermore, it is preferable to maintain the amount of residual solvent at less than 5% by mass at the start of stretching because the in-plane retardations Re and Rth can be easily adjusted to the preferred ranges and the effect on haze can be further improved. The measurement of the residual solvent is as described above, and the term “at the start of stretching” here refers to a dictionary in which, for example, a tenter grips the end of the web with a clip and actually starts stretching. In order to keep the residual solvent amount at the start of stretching below 5% by mass, it is preferable to provide the drying step and evaporate the solvent in the process of peeling the web from the metal support and carrying it. If stretching is performed while retaining a residual solvent of 5% by mass or more, it is difficult to adjust the in-plane retardations Re and Rth to a preferable range, and the haze tends to increase. A preferable residual solvent amount at the start of stretching is 4% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less. This operation is preferably performed online considering productivity.

  There is no particular limitation on the method of stretching the web. For example, a method in which peripheral speed differences are applied to a plurality of rolls and a roll peripheral speed difference is used to stretch the rolls in the MD direction. And a method of stretching in the MD direction, a method of stretching in the transverse direction and stretching in the TD direction, a method of stretching in the MD / TD direction simultaneously and stretching in both the MD / TD directions, and the like. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or width direction stretching in the film forming process is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The film transport tension in the film forming process such as in the tenter depends on the temperature, but is preferably 120 N / m to 200 N / m, and more preferably 140 N / m to 200 N / m. 140 N / m to 160 N / m is most preferable.

  The elastic modulus of the first polarizing plate protective film measured in an environment of 23 ° C. and 55% RH is 3.4 GPA or more and 7.0 GPA or less in both the film longitudinal direction (MD) and the film width direction (TD). It is preferable that the TD elastic modulus / MD elastic modulus is adjusted to be 1.05 to 2.0. In order to avoid the stability of stretching operation, breakage, and the like, the elastic modulus is preferably adjusted by the material type constituting the film and the ratio of the constituting materials in the range of 3.4 GPA or more and 4.5 GPA or less.

  The first polarizing plate protective film is preferably heat-set after stretching, but the heat-setting is higher than the final TD direction stretching temperature and is usually 0.5 to 300 seconds within a temperature range of Tg-20 ° C. or less. It is preferable to heat-set. Under the present circumstances, it is preferable to heat-fix, heating up sequentially in the range from which a temperature difference becomes 1-100 degreeC in the area | region divided into 2 or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. Under the present circumstances, it is preferable to carry out the relaxation | loosening process 0.1 to 10% in TD direction and / or MD direction within the temperature range below the last heat setting temperature and Tg. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1-Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

  More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the additive species such as cellulose acylate and plasticizer constituting the film, so the physical properties of the obtained stretched film are measured, and preferable characteristics are obtained. What is necessary is just to determine by adjusting suitably so that it may have.

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

  As mentioned above, although the manufacturing method of the 1st polarizing plate protective film was demonstrated in detail, when the same film as a 1st polarizing plate protective film is used as a 2nd polarizing plate protective film, manufacture similar to the above is carried out. Of course, the method can be adopted. Moreover, also when the film which has a structure different from a 1st polarizing plate protective film is used as a 2nd polarizing plate protective film, such a 2nd polarizing plate is referred by referring conventionally known knowledge suitably. It is possible to prepare and produce a protective film.

(Bonding of polarizer and polarizing plate protective film)
A polarizing plate is manufactured by bonding a polarizer and a polarizing plate protective film. Among them, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizer produced by subjecting the polarizer side of the first polarizing plate protective film to an alkali saponification treatment and immersion drawing in an iodine solution. It is preferable to bond them together. About this pasting process, conventionally well-known knowledge can be referred to suitably.

≪Display device≫
The polarizing plate according to the present invention can be used in various display devices such as a liquid crystal display device and an organic electroluminescence (EL) display device.

  For example, by incorporating the polarizing plate according to the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be manufactured. The polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), and IPS. Particularly preferred are VA (MVA, PVA) type and IPS type liquid crystal display devices.

  In particular, the polarizing plate of the present invention is less likely to cause deterioration of the polarizer even in a high temperature and high humidity environment. Therefore, even when used in a large-screen liquid crystal display device, it is less likely to cause color unevenness and has excellent visibility. Can be granted.

  Hereinafter, although an embodiment of the present invention is described in detail using an example, the technical scope of the present invention is not limited only to the following form.

<< Synthesis Example: Synthesis of Polyester Compound >>
(Synthesis of polyester compound No. 1)
In a three-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser, 830.7 g (5.0 mol) of phthalic acid and 730.7 g of adipic acid (5. 0 mol), 1,2-propanediol 380.4 (5 mol) ethylene glycol 310.4 g (5 mol), benzoic acid 1221.2 g (10 mol) as a terminal component, and tetraisopropyl titanate 0. 10 g was charged. Next, the mixture was refluxed with stirring under a nitrogen stream, and the temperature was raised stepwise to 220 ° C, followed by dehydration condensation reaction at 220 ° C for 15 hours. After completion of the reaction, the unreacted product was distilled off under reduced pressure, and the polyester compound No. 1 shown in Table 2 was obtained. 1 was obtained.

  Similarly, using the raw materials described in Table 1 below, polyester compounds No. 2-No. 6 was synthesized.

≪Preparation of dope≫
(Silicon dioxide dispersion)
Aerosil R812 (Nippon Aerosil Co., Ltd.) 10 parts by mass Ethanol 90 parts by mass The above was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution. It filtered with the fine particle dispersion | distribution dilution liquid filter (Advantech Toyo Co., Ltd .: Polypropylene wind cartridge filter TCW-PPS-1N).

(Preparation of cellulose acylate dope 1 (surface layer dope or single layer dope))
TAC: Triacetylcellulose (acetyl group substitution degree 2.89, Mw = 19000) 100 parts by mass Additive 1: Polyester compound No. 1 5 parts by mass Additive 3: Acrylyl compound represented by the general formula (1) (I-10) 1 part by mass Methylene chloride 700 parts by mass Ethanol 40 parts by mass The above is put into a sealed container, heated and stirred. While completely dissolved and filtered. To this, 4 parts by mass of the silicon dioxide dispersion dilution was added with stirring, and the mixture was further stirred for 30 minutes.

<< Production of first polarizing plate protective film by solution casting >>
(Preparation of the 1st polarizing plate protective film 1)
Using a belt casting apparatus, the dope prepared above was cast uniformly on a stainless steel band support at a temperature of 35 ° C. and a width of 2 m. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100% by mass, and the stainless steel band support was peeled off. The peeled film web is conveyed while being dried at 50 ° C., slitted, and then stretched by a tenter in the TD direction (direction perpendicular to the film conveying direction) at a temperature of 190 ° C. and a stretching ratio of 10%. And dried at a drying temperature of 160 ° C. At this time, the residual solvent amount when starting stretching with a tenter was 4.5% by mass. Then, after being dried for 15 minutes while being transported in a drying apparatus at 120 ° C. with a number of rolls, slitting is performed, a knurling process with a width of 15 mm and a height of 10 μm is applied to both ends of the film, and the film is wound around a core. A polarizing plate protective film 1 was obtained. The residual solvent amount of the film was less than 0.1%, and the film thickness was 25 μm. In addition, about the 1st polarizing plate protective film 1, when halogen element content was measured with the following methods, it was 100 mass ppm.

[Measurement method of halogen element content]
The halogen element content in the polarizing plate protective film was measured using a combustion ion chromatograph analysis system (Mitsubishi Chemical Analytech AQF-100F).

  A clear hard coat (CHC) layer was formed on one surface of the first polarizing plate protective film 1 produced above by the following method.

The following hard coat layer coating composition was extrusion coated and then dried in a drying section set at 80 ° C. for 30 minutes, and then the coating layer was cured by irradiation with ultraviolet rays of 150 mJ / cm ² .

(Hardcoat layer coating composition)
Dipentaerythritol hexaacrylate (contains about 20% of dimer or higher components)
108 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 2 parts by mass Propylene glycol monomethyl ether 180 parts by mass Ethyl acetate 120 parts by mass In this way, a clear hard coat (CHC) layer having a thickness of 5 μm was formed.

(Preparation of first polarizing plate protective films 2 to 37 (with some overlap; excluding film 32))
Kind of additive 1 contained in first polarizing plate protective film, presence / absence / type of additive 2, presence / absence / type of additive 3, thickness of first polarizing plate protective film, and clear hard coat (CHC) ) Except that the presence / absence / type of additives contained in the layer and the thickness of the clear hard coat (CHC) layer were changed as shown in Table 2 below, the “of the first polarizing plate protective film 1” First polarizing plate protective films 2 to 37 (with some overlap; excluding film 32) were produced by the same method as “Production”.

<< Production of first polarizing plate protective film by melt casting >>
(Preparation of the 1st polarizing plate protective film 32)
A mixture obtained by mixing the additives shown in Table 2 below and cellulose acylate dried at 80 ° C. for 6 hours was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. Pellets (moisture content 50 mass ppm) were melt extruded from a T die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder, and a cast film having a thickness of 120 μm. Got. At this time, the film was pressed with an elastic touch roll having a 2 mm thick metal surface on the first cooling roll. A first polarizing plate protective film 32 was prepared in the same manner as in the above-mentioned “Preparation of the first polarizing plate protective film 1” except that the film thus obtained was used.

<< Production of Second Polarizing Plate Protective Film 1 by Solution Casting >>
(Production of second polarizing plate protective film 1)
The 2nd polarizing plate protective film 1 was produced by the method similar to "Preparation of the 1st polarizing plate protective film 1 by the solution casting method" mentioned above except not having added the additive 3.

(Preparation of second polarizing plate protective films 2 to 37 (with some overlap)
Except for changing the kind of additive 1 contained in the second polarizing plate protective film, the presence / absence / type of additive 2, and the thickness of the second polarizing plate protective film as shown in Table 2 below, Second polarizing plate protective films 2 to 37 (partially overlapped) were prepared by the same method as the above-described “Preparation of second polarizing plate protective film 1”.

≪Preparation of polarizing plate≫
(Preparation of polarizing plate 1)
The polarizing plate was produced by a general method. The polarizer (thickness 25 μm) prepared by subjecting the polarizer side of each of the first polarizing plate protective film 1 and the second polarizing plate protective film 1 produced above to alkali saponification treatment and immersion drawing in an iodine solution. Both surfaces were bonded together using a completely saponified polyvinyl alcohol aqueous solution. Thereby, the polarizing plate 1 (thickness 80 micrometers) was produced.

(Preparation of polarizing plates 2 to 37)
Except that the combination of the first polarizing plate protective film and the second polarizing plate protective film and the thickness of the polarizer were changed as shown in Table 2 below, the same as “Preparation of polarizing plate 1” described above. The polarizing plates 2-35 were produced by the method of.

≪Evaluation of polarizing plate≫
About the polarizing plate produced above, the following methods evaluated the grade of deterioration of a polarizer and the generation | occurrence | production of the curvature (curl) of a polarizing plate. The results are shown in Table 2 below.

(Degradation of polarizer)
The polarizing plate produced above was cut into a 37-inch size, put into a wet heat thermostat at 80 ° C. and 90% RH, and the degree of deterioration of the polarizer after 100 hours was visually observed. The evaluation criteria are as follows.

  A: There is no deterioration.

  ○: There is very little deterioration.

  ○: Partial deterioration is observed.

  Δ: Deterioration is observed on the entire surface.

  X: Strong deterioration is observed on the entire surface.

(Slave of polarizing plate)
The polarizing plate produced above was cut into a 37-inch size and placed on a flat plate, and the degree of warpage (curling) was visually observed. The evaluation criteria are as follows.

  ○: No warpage is observed.

  ○ △: Slight warping is observed.

  Δ: Sled is observed.

  X: Vigorous sled is seen.

  From the results shown in Table 2, according to the polarizing plate according to the present invention, curling can be prevented by reducing the thickness of the polarizing plate while minimizing the deterioration of the polarizer in a high temperature and high humidity environment. It can be shown that various techniques can be provided.

Claims (10)

A polarizer,
A first polarizing plate protective film containing cellulose acylate bonded to one surface of the polarizer;
A second polarizing plate protective film bonded to the other surface of the polarizer;
A polarizing plate having
The thickness is 50-100 μm,
The first polarizing plate protective film has the following general formula (1):
In the formula, R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ₁₂ and R ₁₃ each independently represents an alkyl group having 1 to 8 carbon atoms,
An acryloyl-based compound represented by
The halogen element content in the first polarizing plate protective film is 50 to 2000 ppm by mass with respect to 100% by mass of the total amount of the film,
A polarizing plate comprising a clear hard coat layer disposed on one surface of the first polarizing plate protective film or the second polarizing plate protective film.   The polarizing plate according to claim 1, wherein the second polarizing plate protective film contains cellulose acylate. The first polarizing plate protective film has the following general formula (2):
In the formula, B is a benzene monocarboxylic acid residue or an aliphatic monocarboxylic acid residue, and G is an alkylene glycol residue having 2 to 18 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or 4 carbon atoms. -12 is an oxyalkylene glycol residue having -12, A is an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 16 carbon atoms, and n is an integer of 1 or more.
The polarizing plate of Claim 1 or 2 containing the polyester-type compound represented by these.   The polarizing plate according to claim 1, wherein the first polarizing plate protective film does not contain a halogen element-containing ultraviolet absorber.   The polarizing plate according to claim 1, wherein the first polarizing plate protective film has a thickness of 15 to 35 μm. The clear hard coat layer, of the first polarizing plate protective film, the are arranged in a surface opposite to the polarizer, the polarizing plate according to any one of claims 1 to 5.   The polarizing plate according to claim 1, wherein the clear hard coat layer contains an ultraviolet absorber. It is a manufacturing method of a polarizing plate given in any 1 paragraph of Claims 1-7,
Drying the film obtained by casting a dope containing cellulose acylate, the acryloyl-based compound and a solvent on a support, obtaining the first polarizing plate protective film by a process of peeling and peeling, and
Bonding the obtained first polarizing plate protective film with a polarizer;
Manufacturing method.   The manufacturing method of Claim 8 whose said solvent is a halogen-type solvent. The display apparatus provided with the polarizing plate of any one of Claims 1-7.