WO2013118566A1 - Process for producing optical film - Google Patents

Description

Manufacturing method of optical film

The present invention relates to a method for producing an optical film. More specifically, the present invention relates to a method for producing an optical film in which surface roughness does not occur even when a film having a thinner film thickness than that of the conventional film is formed by a melt casting method and gel-like foreign matters are reduced.

Polymethyl methacrylate (hereinafter abbreviated as “PMMA”), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like. However, the PMMA film has poor heat resistance, and there has been a problem that the shape changes when used under high temperatures or for long-term use.

In order to improve heat resistance, an optical film in which an acrylic resin and a specific cellulose ester resin are mixed has been proposed (for example, see Patent Document 1). In addition, an optical film in which the same material is melt casted to improve brittleness, yellowness, and bleed-out simultaneously, and a method for producing the same have been proposed (for example, see Patent Document 2).

In order to reduce environmental burden and reduce costs, resin film production has shifted from solution casting film formation to melt casting film formation. At the same time, in terms of cost reduction, there is a demand for thinning of liquid crystal displays, which is also a market need, and it is necessary to reduce the thickness of optical films as members.

In the study of thinning the optical film, we made a film thinner than the film thickness of the conventional optical film by melt casting using the resin composition containing the above acrylic resin and cellulose ester resin. However, the present inventors have found that a film surface failure called surface roughness that has not been seen so far occurs. Further, it has been found that the thinning increases the haze increase due to foreign matters and the influence on bright spot defects, and further reduction of foreign matters is required.

JP 2009-299075 A JP 2010-122340 A

The present invention has been made in view of the above-described problems and situations, and a solution to the problem is that a conventional optical film is formed by melt casting using a resin composition containing an acrylic resin and a cellulose ester resin. It is an object of the present invention to provide a method for producing an optical film in which surface roughness does not occur and gel-like foreign matters are reduced when a film is formed thinner than this film thickness.

In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, surface roughness generated during melt casting film formation, residual unreacted monomer that is an impurity in the acrylic resin, residual polymerization start It has been found that the reactivity of the agent, the residual chain transfer agent, etc. is increased by heating, and is produced by the formation of a high molecular weight substance that is presumed to be an aggregation of acrylic resin or cellulose ester resin. It has also been found that residual unreacted monomers, residual polymerization initiators and residual chain transfer agents, which are impurities in the acrylic resin, become gel-like foreign substances by reacting with part of the cellulose ester resin.

Thus, the present inventors have found that surface roughness and generation of gel-like foreign matters can be suppressed by reducing the generation of a high molecular weight substance that is presumed to be an aggregation of an acrylic resin or a cellulose ester resin.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. A method for producing an optical film for melt casting using a resin composition containing at least an acrylic resin and a cellulose ester resin in a mass ratio within a range of 95: 5 to 30:70, comprising: A method for producing an optical film, characterized in that the high molecular weight product formation rate H defined by the following formula is within the range of 0 to 10%.

Formula H = (a / b) × 100 (%)
Here, H is a molecular weight (Mw) on the horizontal axis and a detection sensitivity value on the vertical axis in gel permeation chromatography (GPC) measurement of the resin composition containing the acrylic resin and the cellulose ester resin. The difference in detection sensitivity value obtained by subtracting the detection sensitivity value of GPC before heating of the resin composition from the detection sensitivity value of GPC after heating the resin composition at a temperature of 260 ° C. for 1 hour is expressed as a molecular weight (Mw ) And the value obtained by dividing the positive difference area (a) of the obtained waveform by the area (b) of GPC before heating of the resin composition ((a / b) × 100 (%)) ). The positive differential area (a) is an area on the higher molecular weight side than the molecular weight value indicating the GPC detection sensitivity peak value before heating of the resin composition.

2. The weight average molecular weight Mw of the acrylic resin is in the range of 2.0 × 10 ⁴ to 5.0 × 10 ⁵ , and the content of residual unreacted monomer in the acrylic resin is in the range of 100 to 1000 ppm. 2. The method for producing an optical film as described in 1 above.

3. Item 1 or Item 2 above, wherein the acrylic resin has a residual polymerization initiator content in the range of 10 to 500 ppm and a residual chain transfer agent content in the range of 10 to 500 ppm. The manufacturing method of the optical film of description.

4. It is a manufacturing method of the optical film as described in any one of said 1st term | claim-3rd item | term, Comprising: The said cellulose ester resin is mixed with a cellulose-ester solution and a poor solvent, By precipitating a cellulose ester. When producing, the content of water in the solvent contained in the cellulose ester solution is in the range of 10 to 60% by mass, and the SP of the whole solvent after mixing the cellulose ester solution and the poor solvent. A method for producing an optical film, characterized in that the numerical value (s) of the value and the total number of acyl groups (t) per glucose unit of the precipitated cellulose ester satisfy the following formulas (1) and (2).

Formula (1) a = s + 0.8t
Formula (2) 31 ≦ a ≦ 40
(In the formula, s is the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent, and t is the total number of acyl group carbon atoms per glucose unit of the cellulose ester. 0.8t above) Is a term relating to the contribution of the acyl group to the SP value.)
5. The optical component according to any one of items 1 to 4, wherein the content of the alkali metal or the group 2 element in the cellulose ester resin is in the range of 1 to 150 ppm. A method for producing a film.

6. 6. The method for producing an optical film according to any one of items 1 to 5, wherein the thickness of the optical film is in a range of 10 to 35 μm.

When the above-mentioned means of the present invention is used to form a film with a thickness smaller than that of a conventional optical film by melt casting using a resin composition containing an acrylic resin and a cellulose ester resin, surface roughness occurs. And a method for producing an optical film with reduced gelled foreign matters can be provided. Moreover, the optical film manufactured by this optical film manufacturing method can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

According to the study by the present inventors, the phenomenon of surface roughness is that an unintended high molecular weight body is generated in the resin composition when the resin composition is heated and melted, and the high molecular weight body is the resin composition. Since the compatibility with the product is inferior, it is presumed that it appears on the surface of the web in the film forming stage and the surface state becomes irregular uneven shape.

Acrylic resins are usually obtained by polymerizing monomers such as methyl methacrylate in the presence of a polymerization initiator or chain transfer agent, so that residual components such as unreacted monomers, polymerization initiators, chain transfer agents, etc. May be included. It is presumed that these residual components are activated at the time of heat-melting and react with an acrylic resin or a cellulose ester resin to produce the unintended high molecular weight body. At the same time, it is presumed that the residual component reacts with a part of the cellulose ester resin to form a gel-like foreign material.

Therefore, according to the present invention, the resin composition containing the acrylic resin and the cellulose ester resin is heated at a specific temperature and time condition to suppress the formed high molecular weight polymer within a certain amount, so that the residual unreacted The content of monomers, residual polymerization initiators and residual chain transfer agents can be reduced, and unintentional high molecular weight products can be suppressed. Even in this case, it is considered that a method for producing an optical film in which surface roughness does not occur and gelled foreign matters are reduced can be provided.

GPC peak area before heating of resin composition containing acrylic resin and cellulose ester resin (b) Change in peak area of GPC before and after heating resin composition containing acrylic resin and cellulose ester at 260 ° C. for 1 hour Positive differential area according to the present invention (a) Diagram showing an example of acrylic resin synthesis method Schematic diagram showing an example of film production equipment

The method for producing an optical film of the present invention is an optical film for melt casting using a resin composition containing at least an acrylic resin and a cellulose ester resin in a mass ratio within a range of 95: 5 to 30:70. A production method, characterized in that the high molecular weight product formation rate H calculated by the above method of the resin composition is in the range of 0 to 10%, and this structure is an effect of the present invention. Even when the cast film is formed thinner than the conventional film thickness, the occurrence of surface roughness is prevented.

This feature is a technical feature common to the inventions according to claims 1 to 6.

As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, the weight average molecular weight Mw of the acrylic resin is in the range of 2.0 × 10 ⁴ to 5.0 × 10 ⁵ and The content of residual unreacted monomer is preferably in the range of 100 to 1000 ppm. In addition, the residual initiator content of the acrylic resin is in the range of 10 to 500 ppm, and the residual chain transfer agent content is in the range of 10 to 500 ppm, which further enhances the effect of preventing surface roughness. Therefore, it is preferable.

Furthermore, in the present invention, it is preferable that the cellulose ester resin is a purified cellulose ester resin produced by the method for producing the specific cellulose ester resin.

The cellulose ester resin reacts with the residual unreacted monomer, the residual polymerization initiator and the residual chain transfer agent to produce the high molecular weight product. Which component of the cellulose ester resin is denatured into the high molecular weight material still remains. Do not go out of speculation. However, it has been found that the use of a purified cellulose ester resin produced by the method for producing a cellulose ester resin can reduce the generation of high molecular weight bodies and, at the same time, reduce the occurrence of gelled foreign substances.

In addition, it is preferable that the content of the alkali metal or the Group 2 element in the cellulose ester resin is in the range of 1 to 150 ppm, respectively, because the effect of reducing the occurrence of gelled foreign matters can be further enhanced.

Also, the thickness of the optical film is preferably in the range of 10 to 35 μm from the viewpoint of thinning the liquid crystal display.

The optical film produced by the method for producing an optical film of the present invention is an optical film which is a thin film, excellent in surface shape and high in heat resistance, and suitable for various display devices other than a polarizing plate protective film and a liquid crystal display device. It is.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<Roughness>
The surface roughness referred to in the present invention refers to a phenomenon in which irregular irregularities are generated on the film surface with a size that can be visually confirmed. For example, it refers to a state in which the surface of the optical film is rough like a pine skin or a dried rice paper.

The phenomenon of surface roughness is that an unintended high molecular weight product is generated in the resin composition when the resin composition is heated and melted, and the high molecular weight material is poor in compatibility with the resin composition. It is presumed that it appears on the surface of the web in the film forming stage and the surface state becomes irregular irregular shapes.

<Gel foreign matter>
Unlike the high molecular weight body, the gel-like foreign material is a minute foreign material that can be confirmed with a microscope or the like. Although the shape is various, for example, it is specified as a gel by the following test method.

10 mg of the finely pulverized optical film was put into an aluminum pan, and heated at 260 ° C. for 60 minutes under N ₂ flow using TG / DTA6200 (manufactured by SII Nanotechnology). The heated aluminum pan containing the optical film is placed in a 10 ml volumetric flask, and this is made up to 10 ml with THF (tetrahydrofuran). Then, after storage at 23 ° C. for 24 hours, the dissolution state of the optical film in the aluminum pan is visually observed and observed as undissolved (gel).
If there are a large number of the above-mentioned gel-like foreign matters, it causes light scattering, resulting in a decrease in total light transmittance, a bright spot defect, etc., and especially assuming that the optical film of the present invention is used as a polarizing plate protective film, Foreign substances should be reduced as much as possible. In particular, in the case of a thin film optical film as in the present invention, even if the foreign matter has the same size, the influence on the optical characteristics is great, so that the gel-like foreign matter needs to be reduced more than before.

The number of gel-like foreign matters in the optical film is, for example, cut out 1 m ² minutes from the winding of the optical film obtained by melt casting film formation, hitting the light of the fluorescent lamp to the film, and visually checking the uneven reflection of the surface Then, the content of the confirmed part is examined with an optical microscope, separated from external foreign substances such as dust, and the longest diameter (the longest diameter connecting the end portion of the particle projection image) is less than 100 μm. Are counted as the number of gel-like foreign matters.

The gelled foreign matter is preferably less than 100 pieces / m ² , more preferably 50 pieces / m ² or less, and particularly preferably 10 pieces / m ² or less.

<Calculation of high molecular weight product formation rate H>
Here, calculation of the high molecular weight product formation rate H, which is a feature of the present invention, will be described with reference to the drawings.

FIG. 1 shows a GPC measurement before heating using a resin composition containing an acrylic resin and a cellulose ester resin. The horizontal axis is the molecular weight and the vertical axis is a waveform plotted with the detection sensitivity value. b).

FIG. 2 is an example of a change in the waveform of GPC before and after a resin composition containing an acrylic resin and a cellulose ester resin was heated at a temperature of 260 ° C. for 1 hour.

It can be seen that the GPC waveform after heating shown by the broken line is shifted to the high molecular weight side with respect to the GPC waveform before heating shown by the solid line, and a high molecular weight body is generated.

FIG. 3 shows the detection sensitivity obtained by subtracting the GPC detection sensitivity value before heating the resin composition from the GPC detection sensitivity value after heating the resin composition of acrylic resin and cellulose ester resin at 260 ° C. for 1 hour. The value difference is plotted against the horizontal axis molecular weight (Mw). In addition, the positive difference area (a) of the detection sensitivity value difference as used in the field of this invention is an area which exists in the high molecular weight side from the molecular weight value which shows the GPC peak before the heating of this resin composition.

The polymer production rate H according to the present invention is a value obtained by dividing the positive difference area (a) by the area (b) of the GPC before heating, as shown by the following formula.

Formula H = (a / b) × 100 (%)
For the heating operation, specifically, a resin composition containing an acrylic resin and a cellulose ester resin, which are samples, is applied to about 5 to 10 mg of a sample using a thermal analysis apparatus (EXSTAR6000 TG / DTA) manufactured by SII. Heat for 1 hour while maintaining the temperature at 260 ° C. in a nitrogen stream.

The heating condition of 260 ° C. for 1 hour is set by simulating the temperature and elapsed time that the resin composition receives from the production apparatus during the melt casting film formation.

The molecular weight is measured by the following GPC using the obtained sample before and after heating.

The measurement conditions for GPC are as follows.
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 Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

In order to obtain the area of the area (b) and the positive difference area (a) from the waveform measured by GPC, it can be calculated using area analysis software. For example, the area can be obtained using a multi-station GPC-8020 model II manufactured by Tosoh Corporation.

Therefore, when the high molecular weight product formation rate H takes a positive value, the resin composition containing the acrylic resin and the cellulose ester resin is generating a high molecular weight product by heating during melt casting film formation. However, as a result of many experiments, if this value can be kept within the range of 0 to 10% in a practical system, the surface roughness of the optical film formed thinner than before is rough. The above range was set after confirming that there was no.

The high molecular weight production rate H according to the present invention is required to obtain the effect of the present invention within the range of 0 to 10%, and preferably within the range of 0 to 6%. And the generation of gel-like foreign matters are preferred from the viewpoint of being able to significantly suppress the generation.

<Acrylic resin>
The acrylic resin according to the present invention may be an acrylic resin having an aromatic ring in the side chain or an acrylic resin having a cyclohexyl group in the side chain, and the weight average molecular weight Mw of the acrylic resin is 2.0 × 10 ⁴ to It is preferably within the range of 5.0 × 10 ⁵ . Within this range, excellent heat resistance and compatibility with the cellulose ester resin are excellent.

The acrylic resin according to the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxy group in the molecule, and an ethylenically unsaturated monomer Xb and Xa having no aromatic ring in the molecule and having a hydroxy group. , A polymer X obtained by copolymerization with a copolymerizable ethylenically unsaturated monomer other than Xb, or styrene or its derivative Ya and an ethylenically unsaturated group having no hydroxy ring and having a hydroxy group. A polymer Y obtained by copolymerizing a saturated monomer Yb and a copolymerizable ethylenically unsaturated monomer excluding Ya and Yb is preferable.

[Polymer X, Polymer Y]
The polymer X includes an ethylenically unsaturated monomer Xa that does not have an aromatic ring and a hydroxy group or an amide group in the molecule, and an ethylenically unsaturated monomer Xb that does not have an aromatic ring in the molecule and has a hydroxy group or an amide group. And a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb.

Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydroxy group or an amide group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydroxy group or an amide group.

The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-[Xa] _m- [Xb] _n- [Xc] _p-
In the general formula (X), Xa represents an ethylenically unsaturated monomer that does not have an aromatic ring and a hydroxy group or an amide group in the molecule, and Xb does not have an aromatic ring in the molecule and has a hydroxy group or an amide group. Xc represents a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

Furthermore, the polymer X is preferably a polymer represented by the following general formula (X-1).

Formula (X-1)
— [CH ₂ —C (—R ₁ ) (— CO ₂ R ₂ )] _m — [CH ₂ —C (—R ₃ ) (— CO ₂ R ₄ —OH) —] _n — [Xc] _p —
In the general formula (X-1), R ₁ and R ₃ each represent a hydrogen atom or a methyl group. R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R ₄ represents —CH ₂ —, —C ₂ H ₄ —, or C ₃ H ₆ —. Xc represents a monomer unit polymerizable to [CH ₂ —C (—R ₁ ) (— CO ₂ R ₂ )] or [CH ₂ —C (—R ₃ ) (— CO ₂ R ₄ —OH) —]. To express. m, n, and p represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

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

In X, the hydroxy group means not only a hydroxy group but also a group having an ethylene oxide chain. The ethylenically unsaturated monomer Xa having no aromatic ring and hydroxy group or amide group in the molecule is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate ( n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), etc. What changed the acid ester into the methacrylic acid ester can be mentioned. Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydroxy group or an amide group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxy group, for example, acrylic acid (2-hydroxy Ethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or these acrylic acids replaced with methacrylic acid Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

As monomer units having an amide group in Xb, N-vinylpyrrolidone, N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylpiperidone, N-vinylcaprolactam, acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N , N-dimethylaminopropylacrylamide, N, N-diethylacrylamide, N-hydroxyethylacrylamide, N-vinylacetamide and the like. Xc is not particularly limited as long as it is a monomer other than Xa and Xb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

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

Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

The polymer Y used in the present invention does not have an aromatic ring in the molecule with styrene or its derivative Ya, and has an ethylenically unsaturated monomer Yb having a hydroxy group and a copolymerizable ethylenically unsaturated group excluding Ya and Yb. A polymer Y obtained by copolymerizing with a monomer is preferred.

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

General formula (Y)
-[Ya] _m- [Yb] _n- [Yc] _p-
In the general formula (Y), Ya represents styrene or a derivative thereof, Yb has no aromatic ring in the molecule and has an ethylenically unsaturated monomer having a hydroxy group, and Yc is copolymerizable except for Ya and Yb. Represents an ethylenically unsaturated monomer. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

Monomers as monomer units constituting the polymer Y of the present invention are listed below, but are not limited thereto.

In Y, the hydroxy group means not only a hydroxy group but also a group having an ethylene oxide chain. Styrene or its derivative Ya is styrene or a compound in which other groups are bonded to styrene as a styrene derivative. For example, alkylstyrene such as methylstyrene, 2,4-dimethylstyrene, ethylstyrene, hydroxystyrene, Examples include methoxystyrene, acetoxystyrene, butoxystyrene, ethoxyethoxystyrene, and substituted styrene in which a hydroxy group, an alkoxy group, or the like is introduced into the benzene nucleus of styrene.

The ethylenically unsaturated monomer Yb having no aromatic ring in the molecule and having a hydroxy group or an amide group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxy group, for example, acrylic acid (2-hydroxy Ethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or these acrylic acids replaced with methacrylic acid Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

As monomer units having an amide group in Yb, N-vinylpyrrolidone, N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylpiperidone, N-vinylcaprolactam, acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N , N-dimethylaminopropylacrylamide, N, N-diethylacrylamide, N-hydroxyethylacrylamide, N-vinylacetamide and the like.
Yc is not particularly limited as long as it is a monomer other than Ya and Yb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

The molar composition ratio m: n of Ya and Yb is preferably in the range of 5:95 to 60:40, more preferably in the range of 10:90 to 40:60. P of Yc is 0-10. Yc may be a plurality of monomer units.

Further, if the molar composition ratio of Yb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Ya and Yb.

The hydroxy group value of the polymers X and Y is preferably 30 to 150 [mgKOH / g].

(Method for measuring hydroxy group value)
The hydroxy group value is measured according to JIS K 0070 (1992). This hydroxy group value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bound to a hydroxy group when 1 g of a sample is acetylated.

Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. Attach an air cooling tube to the mouth of the flask and heat in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid.

Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point.

Further, as a blank test, titrate without putting a sample, and obtain the inflection point of the titration curve. The hydroxy group value is calculated by the following formula.

Hydroxy group value = {(BC) × f × 28.05 / X} + D
In the formula, B is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of a 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount 56.11 of potassium hydroxide.

The above-mentioned polymer X and polymer Y are both excellent in compatibility with the cellulose ester resin, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, dimensions Excellent stability.

The acrylic resin according to the present invention is preferably subjected to a polymerization reaction by introducing a composition containing the monomer, a polymerization initiator, and a chain transfer agent into a reaction vessel.

Examples of radical polymerization initiators include organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate; potassium persulfate, ammonium persulfate Persulfates such as: 2,2′-azobis (2-methylpropionitrile) (AIBN), azo compounds such as azobis-2,4-dimethylvaleronitrile; redox in which organic peroxide and reducing agent are combined System initiators; redox initiators in which a persulfate and a reducing agent are combined are included. Only one type of radical polymerization initiator may be used, or a mixture of two or more types may be used.
The amount of radical polymerization initiator charged can be about 0.01 to 1% by mass relative to the total amount of monomer components.

Examples of chain transfer agents include alkyl mercaptans having 3 to 18 carbon atoms. Examples of alkyl mercaptans include n-octyl mercaptan, dodecyl mercaptan and the like.

The charge amount of the chain transfer agent can be about 0.05 to 1% by mass with respect to the total amount of the monomer components.

For example, the copolymerization may be suspension polymerization, emulsion polymerization, solution polymerization or bulk polymerization. In particular, since no solvent is used during polymerization, separation of the resulting polymer and solvent is unnecessary, and bulk polymerization is preferred because there is little mixing of an emulsifier, a dispersant, and the like into the polymer.

The polymerization temperature in suspension polymerization or emulsion polymerization can be in the range of 30 to 100 ° C .; the polymerization temperature in bulk polymerization is preferably in the range of 80 to 300 ° C. The polymerization reaction in bulk polymerization can be performed in a polymerization reactor, a heater, and a devolatilizing extruder as described later. The polymerization time can be in the range of 1 to 10 hours, for example.

FIG. 4 is a diagram showing an example of an acrylic resin synthesis method. The figure shows an example of bulk polymerization of methyl methacrylate (MMA) and acryloylmorpholine (ACMO).

As shown in FIG. 4, methyl methacrylate (MMA) and acryloylmorpholine (ACMO), which are raw material monomers, and a polymerization initiator (catalyst) are mixed in a catalyst preparation tank to obtain a catalyst solution.

On the other hand, methyl methacrylate (MMA) and acryloylmorpholine (ACMO), which are raw material monomers, and a chain transfer agent are mixed in a monomer preparation tank to obtain a monomer mixture.

The obtained catalyst solution and monomer mixture are mixed in a polymerization reactor to polymerize methyl methacrylate (MMA) and acryloylmorpholine (ACMO). Thereby, a liquid polymer composition is obtained. The polymerization temperature in the polymerization reactor is preferably in the range of 80 to 200 ° C, more preferably in the range of 80 to 180 ° C. The polymerization reaction of methyl methacrylate (MMA) and acryloylmorpholine (ACMO) in the polymerization reactor is carried out in order to obtain a fluid polymer composition (liquid polymerization composition). Is preferably 80% by mass or less; in order to increase the reaction efficiency, it is preferable that the average polymerization rate of the resulting polymerization composition is 10% by mass or more. An average polymerization rate shows the ratio (mass ratio) of the polymer contained in a liquid polymer composition.

The obtained liquid polymer composition is supplied to a devolatilizing extruder while being heated by a heater. The heater is a heat retaining means for feeding the liquid polymer composition to the devolatilizing extruder without lowering its temperature. The heating temperature in the heater can be preferably in the range of 150 to 250 ° C. Next, while melting and kneading the obtained polymer composition with a devolatilizing extruder, volatile components (including unreacted monomers and the like) are volatilized and removed from the vent. The melting temperature can preferably be in the range of 200-300 ° C. After the melt-kneaded melt is extruded, it is cooled with water and cut to obtain acrylic resin pellets.

Acrylic resin; In particular, an acrylic resin obtained by bulk polymerization tends to contain residual components such as unreacted monomers (methyl methacrylate and copolymerization monomers), unreacted radical polymerization initiators, and unreacted chain transfer agents. When an acrylic resin and a cellulose ester resin containing these residual components are melt-kneaded at a high temperature, the high molecular weight product formation rate H increases and a high molecular weight product is easily generated.

The cause of the formation of high molecular weight during melt kneading is not necessarily clear, but is presumed as follows. That is, it is considered that the high molecular weight product is produced by a chemical or physical action of a polymer obtained by polymerizing an unreacted monomer and a cellulose ester resin. Moreover, in the filtration filter for removing the foreign material in molten resin, since the residence time of the heated molten resin tends to become long, a high molecular weight body is easy to produce | generate. As a result of these, it is considered that the obtained film is likely to generate a high molecular weight body, and the high molecular weight body is inferior in compatibility, and thus is likely to be rough. In particular, unreacted monomers, radical polymerization initiators, and chain transfer agents among the remaining components are likely to form a high molecular weight body during melt kneading.

Therefore, as described above, it was considered effective to reduce the residual components contained in the acrylic resin below a certain level. However, simply reducing the content of these residual components tends to increase the molecular weight of the resulting acrylic resin. Acrylic resin with a large molecular weight is not only difficult to melt and extrude because of the high viscosity of the melt, but the film obtained by melt-kneading the resin composition of acrylic resin and cellulose ester resin produces a high molecular weight body. It's easy to do.

That is, in order to reduce the production of high molecular weight in the obtained optical film, it is important to balance the content of residual components contained in the acrylic resin and the molecular weight. That is, the obtained acrylic resin preferably satisfies the following requirements a) and b), and more preferably satisfies the requirements c) and d).

(A) The weight average molecular weight Mw is preferably in the range of 2.0 × 10 ⁴ to 5.0 × 10 ⁵ .

(B) The total content of residual unreacted monomers is preferably in the range of 100 to 1000 ppm.

(C) The content of the remaining polymerization initiator is preferably in the range of 10 to 500 ppm.

(D) The content of the residual chain transfer agent is preferably in the range of 10 to 500 ppm.

Regarding the requirement (a) When the weight average molecular weight Mw of the acrylic resin is more than 5.0 × 10 ⁶ , not only is it difficult to melt and extrude, but a high molecular weight body is likely to be produced during melt kneading.

The weight average molecular weight Mw of the acrylic resin is adjusted by the amount of radical polymerization initiator and chain transfer agent charged, the polymerization temperature and polymerization time in the polymerization reactor, the heating temperature in the heater, the melting temperature in the devolatilizing extruder, etc. it can. For example, in order to reduce the weight average molecular weight Mw of the acrylic resin, the charging amount of a polymerization initiator or a chain transfer agent is increased, the polymerization temperature in the polymerization reactor or the heating temperature in the heater is increased, The polymerization time in the polymerization reactor may be shortened.

The weight average molecular weight Mw of the acrylic resin can be measured by the GPC.

The content of unreacted monomer remaining in the acrylic resin is preferably 1000 ppm or less, and more preferably 500 ppm or less. When the content of the remaining unreacted monomer is more than 1000 ppm, a high molecular weight product is easily generated in a film obtained by melt-kneading a resin composition of an acrylic resin and a cellulose ester resin. On the other hand, the content of the remaining unreacted monomer is preferably 100 ppm or more. If the content of the remaining unreacted monomer is less than 100 ppm, the flexibility of a film obtained by melt-kneading a resin composition of an acrylic resin and a cellulose ester resin is likely to be lowered (brittle).

The content of the remaining unreacted monomer is determined by the polymerization temperature and polymerization time in the polymerization reactor, the heating temperature in the heater, the melting temperature in the devolatilizing extruder, the unreacted monomer from the vent of the devolatilizing extruder. It can be adjusted by the displacement of volatile components. In order to reduce the content of the remaining unreacted monomer, for example, the polymerization time in the polymerization reactor may be increased, or the exhaust amount of volatile components from the vent of the devolatilizing extruder may be increased.

The content of the unreacted radical polymerization initiator remaining in the acrylic resin is preferably 500 ppm or less, and more preferably 100 ppm or less. When the content of the residual radical polymerization initiator is more than 500 ppm, a high molecular weight product is easily generated in a film obtained by melt-kneading a resin composition of an acrylic resin and a cellulose ester resin. On the other hand, the content of the remaining radical polymerization initiator is preferably 10 ppm or more. When the content of the residual radical polymerization initiator is less than 10 ppm, the flexibility of a film obtained by melt-kneading a resin composition of an acrylic resin and a cellulose ester resin is likely to be lowered.

The content of the unreacted chain transfer agent remaining in the acrylic resin is preferably 500 ppm or less, and more preferably 100 ppm or less. When the content of the remaining chain transfer agent is more than 500 ppm, the film obtained by melt-kneading the resin composition of the acrylic resin and the cellulose ester resin is likely to be colored. On the other hand, the content of the remaining chain transfer agent is preferably 10 ppm or more. If the content of the unreacted chain transfer agent is less than 10 ppm, the flexibility of a film obtained by melt-kneading a resin composition of an acrylic resin and a cellulose ester resin is likely to be lowered.

The content of the radical polymerization initiator or chain transfer agent remaining in the acrylic resin is the amount of the radical polymerization initiator or chain transfer agent charged, the polymerization temperature and polymerization time in the polymerization reactor, the heating temperature in the heater, and devolatilization. It can be adjusted by the melting temperature in the extruder. For example, in order to reduce the content of the residual radical polymerization initiator or chain transfer agent, it is possible to reduce the amount charged, increase the polymerization temperature in the polymerization reactor or the heating temperature in the heater, The polymerization time in the reactor may be lengthened.

The content of the residual component contained in the acrylic resin can be measured by the following method.

(1) 0.1 g of acrylic resin is dissolved in 2 ml of acetone and sonicated for 30 minutes. After adding 50 ppm of ethylene glycol monomethyl ether as an internal standard component to this solution, the volume is made up to 10 ml with hexane to obtain a sample solution.

(2) The contents (mass%) of the monomer, the polymerization initiator, and the chain transfer agent contained in the sample solution are measured by GC / MS. The GC / MS measurement apparatus and measurement conditions can be as follows.

Device: HP 6890GC / HP5973MSD (manufactured by Hewlett-Packard)
Column: DB-624 (30 m × 0.25 mm.d. 0.25 μm) manufactured by J & W
Oven program: 40 ° C (3min) -20 ° C / min-230 ° C (8min)
Inj: 160 ° C
AUX: 250 ° C
A preferable procedure for simultaneously satisfying the requirements (a) to (d) is: (i) a step of setting a weight average molecular weight Mw of the acrylic resin to be aimed; (ii) setting an amount of the radical polymerization initiator accordingly. (Iii) so that the residual content of unreacted monomer, polymerization initiator, chain transfer agent or the like is within a predetermined range (so as to satisfy the requirements of (b) to (d) above), Adjusting the polymerization temperature and polymerization time.

In order to satisfy the requirements (a) to (d), the amount of radical polymerization initiator or chain transfer agent charged, the polymerization temperature and polymerization time in the polymerization reactor, the heating temperature in the heater, Two or more conditions such as melting temperature and volatile matter discharge amount may be adjusted simultaneously. For example, when only reducing the content of the remaining unreacted monomer, the exhaust amount of volatile matter in the devolatilizing extruder may be increased. However, when the exhaust amount of volatile components in the devolatilizing extruder is increased, the molecular weight of the acrylic resin is also reduced. Therefore, it is only necessary to lower the polymerization temperature or lengthen the polymerization time so that the molecular weight of the acrylic resin does not decrease.

In order to satisfy the requirements (a) to (d), it is also effective to use conditions that increase the amount of radicals generated in the polymerization reaction process. If the amount of radicals generated in the polymerization reaction process is large, the radical polymerization initiator and chain transfer agent can be consumed (remaining radical polymerization initiator and chain transfer agent are reduced) without excessively increasing the molecular weight. is there. That is, by increasing the polymerization temperature in the polymerization reactor and the heating temperature in the heater, the molecular weight of the acrylic resin (a) is kept below a certain level, and the residual components of the acrylic resins (b) to (d) The content can also be kept below a certain level.

The acrylic resin may be one type or a mixture of two or more types.

<Cellulose ester resin>
The cellulose ester resin used for the optical film of the present invention (hereinafter also simply referred to as cellulose ester) preferably has a total acyl group substitution degree of the cellulose ester in the range of 2.0 to 2.95, and The cellulose ester has a total carbon number of acyl group in the range of 4.0 to 10. However, the acyl group total carbon number is the sum of the products of the substitution degree and the carbon number of each acyl group substituted in the glucose unit of the cellulose ester. The carbon number of the acyl group means the carbon number including the carbonyl group, 2 for the acetyl group, 3 for the propionyl group, and 4 for the butyryl group. In other words, the total number of acyl groups in the present invention is calculated based on the cellulose ester having an acetyl group substitution degree of 1, propionyl group substitution degree of 0.5, and a butyryl group substitution degree of 0.5. It is determined by the formula “degree × acetyl group carbon number + propionyl group substitution degree × propionyl group carbon number + butyryl group substitution degree × butyryl group carbon number”.

Further, the number of carbon atoms of the aliphatic acyl group substituted with the cellulose ester is preferably 2 or more and 6 or less, and more preferably 2 or more and 4 or less, from the viewpoint of productivity and cost of cellulose synthesis. The portion not substituted with an acyl group usually exists as a hydroxy group.

The glucose unit constituting cellulose with β-1,4-glycosidic bonds has free hydroxy groups at the 2nd, 3rd and 6th positions. The cellulose ester according to the present invention is a polymer obtained by esterifying some or all of these hydroxy groups with an acyl group. The acyl group substitution degree represents the total of the proportions of cellulose esterified at the 2nd, 3rd and 6th positions of the repeating unit. Specifically, the substitution degree is 1 when the hydroxy groups at the 2-position, 3-position and 6-position of cellulose are each 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of the cellulose are 100% esterified, the degree of substitution is 3 at the maximum.

Examples of the acyl group include an acetyl group, a propionyl group, a butyryl group, a pentanate group, and a hexanate group. Examples of the cellulose ester include cellulose acetate, cellulose propionate, cellulose butyrate, and cellulose pentanate. . Further, mixed fatty acid esters such as cellulose acetate, cellulose acetate propionate, cellulose propionate, cellulose acetate butyrate, and cellulose acetate pentanate may be used as long as the above-mentioned side chain carbon number is satisfied. Among these, cellulose acetate, cellulose acetate propionate, and cellulose propionate are particularly preferable cellulose esters for optical film applications.

A preferred cellulose ester other than cellulose triacetate has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group is Y, It is a cellulose ester which satisfies (i) and (ii) simultaneously.

Formula (i) 2.0 ≦ X + Y ≦ 2.9
Formula (ii) 0.5 ≦ Y ≦ 2.7
Of these, cellulose acetate propionate is particularly preferably used. The portion not substituted with an acyl group is usually present as a hydroxy group. The method for measuring the degree of acyl group substitution can be measured according to ASTM-D817-96.

The cellulose ester according to the present invention preferably has a weight average molecular weight Mw in the range of 50,000 to 500,000, more preferably in the range of 100,000 to 300,000, and still more preferably in the range of 150,000 to 250,000.

Since the average molecular weight and molecular weight distribution of cellulose ester can be measured using high performance liquid chromatography, the weight average molecular weight (Mw) and molecular weight distribution are calculated using this.

The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation)
A calibration curve with 13 samples from Mw = 1000000 to 500 was used. The 13 samples are preferably used at approximately equal intervals.

The raw material cellulose of the cellulose ester used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

In the present invention, cellulose having a high degree of polymerization is preferable. For example, linter pulp is preferable, and it is preferable to use cellulose composed of at least linter pulp. The α-cellulose content, which is an index of the crystallinity of cellulose, is in the range of 90% or more (eg, about 92 to 100%, preferably 95 to 100%, more preferably about 99.5 to 100%). .

The viewpoint that the cellulose ester resin which concerns on this invention is the refined cellulose ester resin manufactured by the manufacturing method of the following cellulose ester resins, suppresses the production | generation of a high molecular weight body, and reduces the gelatinous foreign material simultaneously. To preferred. By adjusting the type of cellulose ester and the type of solvent so as to satisfy the following production methods, in particular, the formula (1) and the formula (2), the crystallized product obtained by the difference in the substituent and degree of substitution of the cellulose ester is coarse. It is a preferable method for obtaining a purified uniform cellulose ester resin by suppressing the growth to a crystallized product.

(Method for producing cellulose ester resin)
The cellulose ester resin according to the present invention is a method for producing a cellulose ester having a step of mixing a cellulose ester solution and a poor solvent and precipitating the cellulose ester, wherein the water content relative to the solvent contained in the cellulose ester solution is The total number of acyl groups per glucose unit of the cellulose ester that is within the range of 10 to 60% by mass and the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent and the precipitated cellulose ester It is preferable to manufacture by the manufacturing method of the cellulose-ester resin in which carbon number (t) satisfy | fills following formula (1) and (2).

Formula (1) a = s + 0.8t
Formula (2) 31 ≦ a ≦ 40
(In the formula, s is the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent, and t is the total number of acyl group carbon atoms per glucose unit of the cellulose ester. 0.8t above) Is a term relating to the contribution of the acyl group to the SP value.)
Details will be described below.

(Cellulose ester solution)
The cellulose ester solution should just be a solution containing a cellulose ester. In addition, when the cellulose ester solution is continuously formed from cellulose ester synthesis to precipitation, a cellulose solution immediately before the cellulose ester precipitation step, for example, cellulose activation step, acylation reaction step, aging step, The cellulose ester solution which passed through the neutralization reaction process is pointed out.

The method for producing the cellulose ester resin is characterized in that the water content of the entire solvent contained in the cellulose ester solution is in the range of 10 to 60% by mass, and both good dispersibility and solubility of the cellulose ester are achieved. From the viewpoint of the above, it is preferably in the range of 15 to 50% by mass.

If the amount is 50% by mass or less, the cellulose ester is easily dissolved and the productivity is improved. If the amount is 60% by mass or less, the effect of reducing gel-like foreign matters is great and the production is also easy.

Moreover, if it is 15 mass% or more, it can shorten time for dispersion | distribution prior to melt | dissolution of a cellulose ester, adhesion to the apparatus of a cellulose ester will reduce, productivity will improve, and if it is 10 mass% or more, it will be a gel-like foreign material. The reduction effect is great.

The solvent used to obtain the cellulose ester solution is a mixed solvent containing water as described above, and any solvent can be used as long as the cellulose ester dissolves. However, as a solvent other than water mixed with water, The SP value is preferably in the range of 18.5 to 37.0 (MPa) ^1/2 . A solvent having an SP value within the above range can easily dissolve the cellulose ester.

The solubility parameter (SP value) of the solvent referred to in the present invention is a value represented by the square root of the molecular aggregation energy, and is described in Polymer Hand Book (Second Edition) Chapter IV Solubility Parameter Values. The unit is (MPa) ^1/2 and indicates a value at 25 ° C. In addition, R.D. F. It can be calculated by the method described in Fedors, Polymer Engineering Science, 14, p147 (1967). In the mixed solvent, the total sum of the mass fraction of each solvent used with respect to the total solvent and the SP value of each solvent is taken as the SP value of the mixed solvent.

In addition to water, a single solvent that does not dissolve the cellulose ester may be used for the cellulose ester solution, and the formulas (1) and (2) may be satisfied in a state where the solvent of the cellulose ester solution and the poor solvent are mixed. It ’s fine.

Specific organic solvents used for the solvent and poor solvent of the cellulose ester solution include, for example, methanol (29.7), ethanol (28.0), water (47.9), butyric acid (19.9), and propion. Acid (20.3), ethyl acetate (18.6), tetrahydrofuran (18.6), benzene (18.8), trichloroethyl (18.8), methyl ethyl ketone (19.0), chloroform (19.0) , Methylene chloride (19.8), acetone (20.2), acetic acid (20.7), pyridine (21.9), n-butanol (23.3), isopropyl alcohol (23.5), dimethylformamide ( 24.8). The numerical value in the parenthesis represents the SP value (MPa) ^1/2 .

However, the solvent of the cellulose ester solution preferably contains a solvent responsible for dissolving the cellulose ester. Specifically, an organic solvent having an SP value in the range of 18.5 to 25.0 is preferably used. It is done.

The solvent responsible for dissolution preferably has an SP value in the range of 18.5 to 23.5, and more preferably has an SP value in the range of 18.5 to 22.0. Preferred solvents include ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methylene chloride, acetone and acetic acid. Furthermore, these solvents may be combined with any solvent. As a preferable combination, for example, in a mixed solvent of acetic acid and water, a mass ratio of acetic acid: water is in the range of 90:10 to 65:35, and in a mixed solvent of acetic acid, methanol and water, a mass ratio of acetic acid / methanol. In the range of 100/0 to 6/94), a mixed solvent of acetone, methanol and water (mass ratio of acetone / methanol is in the range of 100/0 to 8/92). You may contain.

When the cellulose ester solution is prepared using a mixed solvent, the order of addition of the solvent is not limited, and a solvent adjusted so that the cellulose ester is dissolved may be added to the cellulose ester. You may add a cellulose ester to the solvent which adjusted the value. Moreover, when producing the said cellulose-ester solution using several types of solvent, you may adjust so that it may become in the range of SP value which a cellulose ester melt | dissolves in a system, adding a solvent to a cellulose ester sequentially. .

The amount of solvent to be used is not particularly limited, but the solid content concentration of the cellulose ester in the cellulose ester solution before mixing with the poor solvent is preferably in the range of 5 to 30% by mass. If it is 30% by mass or less, it is difficult for foreign substances to be taken into the solid when the cellulose ester is precipitated, and if it is 5% by mass or more, the cellulose ester can be precipitated even if the amount of the poor solvent used is small. Productivity is improved.

The temperature of the step of dissolving the cellulose ester is not particularly limited as long as it is a temperature at which the cellulose ester dissolves, and there is no problem even when heated to reflux with a boiling point or higher, but it is preferably in the range of −20 to 80 ° C.

(Poor solvent)
The “poor solvent” refers to a solvent in which the cellulose ester does not dissolve by 10% by mass or more at 20 ° C., and refers to a solvent added to precipitate the cellulose ester from the cellulose ester solution. Moreover, in the manufacturing process of a cellulose ester, the solvent added in order to precipitate a cellulose ester after the neutralization reaction performed after the aging process for performing partial hydrolysis is called a poor solvent, and when the aging process is not performed, The solvent added to precipitate the cellulose ester after the neutralization reaction performed after the acylation reaction step is referred to as a poor solvent.

In order to precipitate the cellulose ester from the cellulose ester solution, when mixing with the cellulose ester solution step by step while changing the solvent type and composition ratio of the poor solvent, it is necessary to use a solvent that combines all the poor solvents used. It is called a solvent.

The poor solvent may be adjusted so that the numerical value of the total SP value of the solvent combined with the solvent used for the cellulose ester solution is within the range of the formulas (1) and (2). It is preferable that the SP value is adjusted to be higher than that of the solvent used for the cellulose ester solution. If the numerical value of the SP value of the whole solvent is within the range of the above formulas (1) and (2), the crystallized product is dissolved and can be separated from the precipitation of cellulose ester. In addition, if the SP value of the poor solvent is 45.0 or less, it is preferable that the SP value of the poor solvent is adjusted to 45.0 or less because a part of the gel-like foreign matter can be remarkably reduced during the addition. .

As the poor solvent suitably used, two or more solvents having different SP values may be used in combination, and a mixed solvent of water and an organic solvent is preferable. As a preferable mixed solvent of water and organic solvent, for example, a mixed solvent of water and alcohols (methanol, ethanol, isopropyl alcohol, butanol, etc.), a mixed solvent of water and acetic acid, a mixed solvent of acetone and water, water and acetic acid and Examples include a mixed solvent of alcohols (methanol, ethanol, isopropyl alcohol, butanol, etc.), a mixed solvent of water, acetone, and alcohols (methanol, ethanol, isopropyl alcohol, butanol, etc.). The alcohol is preferably methanol or ethanol, more preferably methanol.

The poor solvent may be a solvent prepared in advance so that the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent is within the range of the formulas (1) and (2), While mixing the cellulose ester solution and the poor solvent, stepwise while changing the composition ratio and the solvent species so that the SP value of the whole solvent finally falls within the range of the formulas (1) and (2). May be added. When adding stepwise while changing the composition ratio and solvent type of the poor solvent, the SP value of the poor solvent added stepwise is preferably 45.0 or less.

The amount of the poor solvent used is preferably in the range of 0.5 to 10.0 times, more preferably in the range of 1.0 to 5.0 times the mass of the cellulose ester solution. The composition of the cellulose ester solution and the entire poor solvent is adjusted so that the cellulose ester is precipitated within this range, and the maximum SP value of the poor solvent to be mixed is adjusted to 45.0 or less. Thus, a remarkable reduction effect can be obtained for the gel-like foreign matter.

(Solvent after mixing cellulose ester solution and poor solvent)
The manufacturing method of the said cellulose ester has the process of mixing a cellulose-ester solution and a poor solvent, and precipitating a cellulose ester. Further, the content of water in the range of 10 to 60% by mass with respect to the whole solvent contained in the cellulose ester solution, and the numerical value of the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent: s And the total number of acyl groups in the cellulose ester: t is within the range satisfying the formulas (1) and (2).

Here, “the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent” means “the mass fraction of each solvent in the whole solvent after mixing the cellulose ester solution and the poor solvent”. And the sum of the product of the SP value.

By adjusting the SP value within the above range, precipitation of gel-like foreign matters can be suppressed, gelation of cellulose ester can be prevented, and the effect of reducing gel-like foreign matters can be sufficiently obtained. At the same time, by adjusting the SP value within the above range, aggregation and fine dispersion of the crystallized product can be suppressed.

However, in order to precipitate the cellulose ester, the SP value after mixing the cellulose ester solution and the poor solvent is preferably larger than the SP value of the cellulose ester solution.

From the viewpoint of manifesting the effects of the present invention, the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent: s, and the total number of acyl groups in the cellulose ester: t is the following formula (3): And it is more preferable that it is in the range satisfying the formula (4). Here, 0.8 t below is a term relating to the contribution of the acyl group to the SP value.

Formula (3) a = s + 0.8t
Formula (4) 33 ≦ a ≦ 39
Furthermore, it is particularly preferable that the value is within a range satisfying the following formulas (5) and (6).

Formula (5) a = s + 0.8t
Formula (6) 35 ≦ a ≦ 39
If the value of a exceeds the upper limit of the above formulas (1) and (2), the crystallization product is likely to be precipitated, and the crystallization product is taken into the cellulose ester. Fine dispersion of the precipitate may occur, and the filter may pass through the filter during filtration and the yield may decrease.

When the value of a falls below the lower limit of the above formulas (1) and (2), the target cellulose ester does not become a crystal, and it itself gels, requiring a large amount of man-hours for filtration, making production difficult.

When the value of a is less than or equal to the upper limit of the formulas (3) and (4), the reduction of the crystallized product becomes remarkable, and when it is less than or equal to the upper limit of the formulas (5) and (6), the reduction of the crystallized product is further reduced. Become prominent. When the value of a is equal to or greater than the lower limit of the above formulas (3) and (4), the number of coarse crystals is reduced, and the load on the apparatus in the next step can be reduced and the cellulose ester can be produced efficiently. When it is at least the lower limit of the above formulas (5) and (6), coarser crystallized products are reduced.

(Alcohol)
It is preferable that alcohol is contained in at least one of the cellulose ester solution or the poor solvent. By precipitating the cellulose ester in a state containing the alcohols, aggregation of the cellulose ester is suppressed, and a precipitate can be obtained uniformly in a better shape. Moreover, since the said alcohol is contained, melt | dissolution or dispersion | distribution of a foreign material is accelerated | stimulated, Therefore Content of the foreign material in the cellulose ester obtained by precipitation can be reduced significantly.

The alcohol is not particularly limited as long as it is an alcohol having a hydroxy group, but is preferably an aliphatic alcohol. Examples of aliphatic alcohols include methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and the like. Methanol, ethanol, ethylene glycol, and propylene glycol are preferable, methanol and ethanol are more preferable, and methanol is most preferable.

The amount of the alcohol used is not particularly limited, but is preferably within a range in which the cellulose ester solid does not precipitate when mixed with the cellulose ester solution. The range in which the effects of alcohols are obtained is preferably within a range of 0.1 to 50 times the mass of the cellulose ester, and more preferably from the mass of the cellulose ester from the viewpoint of shape control of the crystallized product. 10 times or less, and most preferably 5 times or less. By setting the amount of alcohol used as described above, a coarse crystallized product is not precipitated, and the precipitation yield can be increased.

The alcohols may be contained in one or both of the cellulose ester solution and the poor solvent. As a method of adding alcohols to the cellulose ester solution, a method of mixing the cellulose ester solution and alcohols, a method of preparing a cellulose ester solution by mixing a mixed solvent containing alcohols and a cellulose ester, cellulose Examples thereof include a method of preparing the cellulose ester solution by adding an ester and an alcohol and then adding another solvent. In addition, in the cellulose ester production process, the alcohol added in the reaction stopping process or the aging process is excessive, and the residual amount of alcohol is in the range of 0.1 to 50 times the mass of the cellulose ester. You may adjust as follows.

(Step of precipitating cellulose ester)
The method for producing the cellulose ester includes a step of mixing the cellulose ester solution and a poor solvent to precipitate the cellulose ester (also referred to as a precipitation step). In the precipitation step, the cellulose ester solution and the poor solvent may be mixed by adding the cellulose ester solution to the poor solvent or adding the poor solvent to the cellulose ester solution. A method of adding a solvent to the cellulose ester solution is preferred.

The solvent used in the precipitation step, the type of solvent used up to the precipitation step, and the preferred mode of the SP value are as described above.

The temperature at which the cellulose ester solution and the poor solvent are mixed is not limited, but is preferably not more than the boiling point of the solvent, more preferably in the range of −10 to 60 ° C., more preferably in the range of 0 to 50 ° C. Is within. However, it has been found that when an acidic solvent such as acetic acid is contained in the cellulose ester solution, hydrolysis of the cellulose ester proceeds and the crystallized product increases remarkably by heating. Therefore, when an acidic solvent such as acetic acid is contained in the cellulose ester solution, the temperature when mixing with the poor solvent is preferably within a range of −10 to 40 ° C., more preferably −10 to 30 ° C. Within range. The temperature lowering may be performed by water cooling or the like, or may be performed continuously or stepwise. In such a temperature drop, the rate of temperature drop may be, for example, in the range of 1 to 20 ° C. per hour, preferably in the range of 3 to 18 ° C., more preferably in the range of 5 to 15 ° C. Good.

The mixing of the cellulose ester solution and the poor solvent is preferably performed with stirring. When carried out under stirring, the stirring speed depends on the scale (manufacturing scale), but is, for example, in the range of 10 to 10,000 rpm, preferably in the range of 20 to 5000 rpm, more preferably in the range of 30 to 3000 rpm. In particular, it may be in the range of 50 to 2000 rpm. In particular, the stirring speed is in the range of 10 to 2000 rpm (eg 20 to 1500 rpm), preferably in the range of 30 to 1000 rpm (eg 40 to 800 rpm), more preferably 50 to 500 rpm (eg 60 to 300 rpm). It may be within the range, particularly within the range of 70 to 200 rpm. It is desirable that the stirring speed be large enough for granulation. When the stirring speed is too low, localization of the poor solvent to be added and uneven temperature distribution may occur, and the effect of reducing the crystallized product may be reduced.

The method for producing the cellulose ester resin may be performed in the cellulose ester synthesis step.

Hereinafter, the cellulose ester synthesis process will be described.

(Synthesis process of cellulose ester)
The cellulose ester synthesis step preferably includes an activation step, an esterification step, an esterification reaction stop step, a filtration step, an aging step, and a neutralization step in this order. The precipitation step may be provided as a part of a post-treatment step provided after the synthesis step, or may be provided after the post-treatment step is completed.

[Activation process]
In the activation step, cellulose is treated with an activator to activate the cellulose. Raw material cellulose is supplied in a slurry wet state.

As the activator for activating cellulose, a solvent for acylation reaction (acylation solvent) is usually used. As the acylation solvent, organic carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid are used. Or an aliphatic carboxylic acid (linear or branched C1-6 alkanoic acid) such as valeric acid. These activators can be used alone or in combination of two or more.

In the activation treatment, an aqueous medium containing water is used as the activator. This aqueous medium may be an aqueous medium containing an organic carboxylic acid. In consideration of substituting the aqueous medium from the cellulose raw material with the carboxylic acid used in the reaction prior to the reaction following the activation treatment, it is economical. It is preferable to use many organic carboxylic acids.

The activation step is not limited to a single activation step, and may be composed of a plurality of activation steps, and can be performed using activators having different concentrations of the acylation catalyst. For example, the acylating catalyst may be composed of a first activating step for activating cellulose with an activating agent and a second activating step for activating cellulose with an activating agent containing an acylating catalyst. You may comprise in the 1st process of processing cellulose with the activator with a low density | concentration, and the 2nd process of processing cellulose with the activator with the high density | concentration of an acylation catalyst.

The amount of the activator used is, for example, in the range of 25 to 150 parts by weight, preferably in the range of 30 to 125 parts by weight, more preferably 50 to 100 parts by weight (for example, 70 parts by weight) with respect to 100 parts by weight of cellulose. May be in the range of about 100 parts by mass).

In the activation treatment, the cellulose may be treated with an activator, the activator may be sprayed on the cellulose, or the cellulose may be immersed in the activator. Usually, raw material cellulose is often added to the activator to form a slurry. The activation treatment temperature can be selected from the range of 0 to 100 ° C. In order to perform the activation treatment without applying industrial load, it is usually within the range of 10 to 40 ° C., preferably about 15 to 35 ° C. It is. The activation treatment time can be selected in the range of 0.1 to 72 hours, and is usually in the range of 0.1 to 3 hours, preferably in the range of 0.2 to 2 hours.

When the solvent used for pulverizing the raw material cellulose is carboxylic acid, the activation process proceeds at the fine pulverization stage, so that the standing time is short, and it can be immediately put into the esterification reaction vessel.

When a solution other than carboxylic acid such as water is used for pulverizing raw material cellulose, the activation treatment is completed by washing with carboxylic acid several times, replacing with carboxylic acid, and allowing to stand.

[Esterification process]
The cellulose activated by the activation treatment is esterified with a carboxylic acid (containing at least one or more) having an acyl group having at least 2 carbon atoms and a carboxylic anhydride (containing at least one or more) in the presence of an acid catalyst. . As the acid catalyst, Lewis acid or strong acid can be used, but sulfuric acid is generally used.

Usually, an acid anhydride [for example, an acid anhydride of a carboxylic acid having 2 or more carbon atoms (carboxylic acid anhydride)], for example, a C ₂ -C ₆ alkane such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, etc. Acid anhydrides can be used. A carboxylic acid having an acyl group having at least 2 carbon atoms (for example, at least a C ₂ -C ₆ carboxylic acid anhydride) is used. You may use these individually or in combination of 2 or more types. As long as it has an acyl group and is easily acylated, it is not limited to carboxylic acids, and organic acid halides can also be used.

The amount of the acid catalyst (particularly sulfuric acid) used in the esterification step is, for example, in the range of 3 to 20 parts by mass, preferably in the range of 5 to 18 parts by mass, more preferably 7 to 15 parts per 100 parts by mass of cellulose. It can be selected from the range of about part by mass, and is usually in the range of 7 to 15 parts by mass.

As the esterification solvent, an esterification solvent corresponding to at least an acyl group having 2 or more carbon atoms, for example, a carboxylic acid (an acid anhydride) may be used. For example, an acid anhydride corresponding to a C ₂ to C ₆ carboxylic acid A plurality of acid anhydrides selected from those having different carbon numbers may be used. For example, propionic anhydride and / or butyric anhydride and acetic anhydride may be used in combination.

Preferred esterification solvents are a combination of acetic anhydride and propionic anhydride, a combination of acetic anhydride and butyric anhydride, and a combination of acetic anhydride, propionic anhydride and butyric anhydride. In particular, a combination of acetic anhydride and propionic anhydride, and a combination of acetic anhydride and butyric anhydride are preferable. Acetic anhydride is more reactive than propionic anhydride and the like, and in the case of obtaining a cellulose mixed fatty acid ester having a low degree of acetyl group substitution, acetic anhydride is not used or the object of the present invention is not impaired. The esterification solvent having at least 3 carbon atoms and corresponding to the acyl group may be combined with a small amount of acetic anhydride.

In the case of obtaining a cellulose ester having an acyl group having 3 or more carbon atoms, the esterification solvent may correspond to an acyl group having 3 or more carbon atoms, for example, propionic anhydride, if acylation or aging can be performed in the presence of acetic acid. What is necessary is just to comprise by butyric anhydride etc., and it does not necessarily need to contain the esterification solvent (acetic anhydride) corresponding to an acetyl group. In order to introduce an acetyl group, acetic anhydride is not necessarily used, and the reaction may be carried out in the presence of acetic acid.

Such acetic acid may be present in the reaction system in the esterification step and the ripening step (particularly at least the ripening step), and may be composed only of acetic acid derived from the activation treatment. May be newly added, and may be used as an esterification solvent in an ordinary esterification step.

In addition, when producing a cellulose ester using a plurality of esterification solvents, in the esterification step, a plurality of esterification solvents may coexist in the reaction system, and after esterifying cellulose with a specific esterification solvent The cellulose may be esterified with another esterification solvent. The amount of the esterification solvent used in the esterification step is, for example, in the range of 1.1 to 4 equivalents, preferably in the range of 1.1 to 2 equivalents, more preferably 1.3 to the hydroxy group of cellulose. It is in the range of about ~ 1.8 equivalent.

In the esterification step, an esterification solvent (organic carboxylic acid such as acetic acid, propionic acid, butyric acid) is usually used as a solvent or diluent. The amount of esterification solvent (carboxylic acid) used is in the range of 50 to 700 parts by weight, preferably in the range of 150 to 600 parts by weight, and more preferably in the range of 200 to 550 parts by weight with respect to 100 parts by weight of cellulose. Degree.

The esterification reaction can be performed at a temperature in the range of 0 to 50 ° C., preferably in the range of 5 to 45 ° C., more preferably in the range of 10 to 40 ° C. The esterification reaction may be initially performed at a relatively low temperature of 10 ° C. or lower (0 to 10 ° C.). The reaction time at such a low temperature may be, for example, 30 minutes or more, 40 minutes to 2 hours, preferably 45 to 100 minutes from the start of the esterification reaction. The esterification time in the range of 10 to 50 ° C. is in the range of 10 to 20 minutes, preferably in the range of 30 to 80 minutes, and in the range of 40 to 75 minutes.

When a uniform reaction system is formed, it can be determined that the esterification reaction has been completed.

After completion of the esterification reaction, the hydrolysis reaction may be started, or the esterification solvent, the esterification solvent, and the acid catalyst may be left as they are, and the aging step may be performed.

[Esterification reaction stopping step]
When the hydrolysis reaction is performed in order to deactivate the esterification solvent after the esterification reaction, it is sufficient if the esterification solvent can be deactivated, and usually contains at least water. The quenching agent that promotes hydrolysis may be composed of water and at least one selected from esterification solvents, alcohols, and neutralizing agents. More specifically, examples of the quencher include water alone, a mixture of water and carboxylic acid, a mixture of water and alcohols, a mixture of water and neutralizer, water, organic carboxylic acid and alcohols. And a mixture of a neutralizing agent and the like.

Examples of the neutralizing agent include bases that can neutralize part of the acid catalyst or esterification solvent, such as alkali metal compounds (hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium carbonate and potassium carbonate, etc. , Organic acid salts such as sodium acetate and potassium acetate), alkaline earth metal compounds (eg, hydroxides such as calcium hydroxide, carbonates such as calcium carbonate, organic acid salts such as calcium acetate and magnesium acetate) And may be used alone or in combination of two or more.

Examples of alcohols include linear alcohols (ethanol, methanol, propanol, etc.). These alcohols can also be used alone or in combination of two or more. The ratio of water and esterification solvent or water and alcohol can be selected from the range of about 20 to 140 parts by mass of the esterification solvent or alcohol with respect to 100 parts by mass of water, and is usually in the range of 25 to 120 parts by mass. Of these, preferably in the range of 50 to 100 parts by mass.

In carrying out the hydrolysis after the esterification step and before the ripening step, a neutralizing agent may be included at a ratio of partially neutralizing the acid catalyst, or a neutralizing agent may not be included.

The preferred deactivator may be water alone, but since water is a poor solvent for cellulose esters, there is a high possibility that cellulose esters other than the desired degree of substitution will precipitate. And a mixed solution is preferable.

Since the reaction component contained in the raw material cellulose is not 100%, an unreacted component is included at this stage, so a step of filtering the reaction solution may be introduced once.

This reaction stopping step can be omitted if necessary.

[Filtering process]
It is preferable to provide a filtration step between the esterification step and an aging step described later.

The solution after completion of the esterification reaction contains unacetylated, low-acetylated components and impurities that did not react with the raw material cellulose. The time is shortened, and specific cleavage of molecular chains and substituents occurring in the reaction solution is less likely to occur. The film surface quality of the film formed using the obtained cellulose ester is cellulose without filtration. Even better than the ester.

Filter media used for filtration preferably have low absolute filtration accuracy, but if the absolute filtration accuracy is too low, the filter media is likely to be clogged, and the filter media must be replaced frequently, reducing productivity. There is a problem of making it.

The material of the filter medium is not particularly limited, and a normal filter medium can be used. However, a filter medium made of plastic such as polypropylene, polyester, and PTFE, a filter medium made of glass fiber, and a metal filter medium such as stainless steel fiber can be used. This is preferable because there is no dropout.

Since the cellulose ester slurry contains an acid, the metal filter is easily corroded, and therefore, a filter made of glass fiber or plastic fiber is more preferable.

When performing filtration using a metal filter between the esterification process and the aging process, it is possible to neutralize and deactivate sulfuric acid and carboxylic anhydride and then move to the filtration process without worrying about corrosion. Can be used.

In particular, it is preferable to use a pressure filter equipped with the above filter medium.

[Aging process]
In the ripening step, after the esterification reaction is almost completed, the acylation is performed to obtain a desired degree of substitution, and after the completion of the deacylation, a neutralizing agent is added to complete the series of reactions. .

When the acid catalyst used for esterification is neutralized, the required amount of acid catalyst may be added again, or used in the aging process without neutralizing the acid catalyst (especially sulfuric acid) used in the esterification process. May be. An acid catalyst other than the acid catalyst used in the esterification may be added.

If sulfuric acid is too much, the molecular weight may be reduced. Therefore, it is preferable to use the acid catalyst used in the esterification step as it is in the aging step without adding an acid catalyst in the aging step.

In addition, in the stage where the acid catalyst is neutralized later, the alkali metal or alkaline earth metal contained in the neutralizing agent is added in the neutralizing agent, and remains in the purified cellulose ester. It is preferable not to add sulfuric acid in the aging process because it can be an obstacle.

In addition, a deacylation solvent (such as a mixed solution of water and carboxylic acid) may be newly added as necessary during aging.

The reaction temperature during the ripening step is preferably in the range of 20 to 90 ° C, preferably in the range of 25 to 80 ° C, more preferably in the range of 30 to 70 ° C, and the ripening reaction is performed in a nitrogen atmosphere. Or in an air atmosphere.

The aging reaction time can be selected from the range of 20 minutes or more and 25 minutes to 6 hours, preferably 30 minutes to 5 hours, and more preferably 1 to 3 hours.

[Neutralization process]
After the desired cellulose ester is obtained in the aging step, it is necessary to neutralize the acid catalyst used for deacylation. As the neutralizing agent, it is preferable to add a neutralizing agent composed of a base described in the esterification reaction stopping step.

The reaction product (dope containing cellulose mixed fatty acid ester) is put into a precipitation solvent (water, aqueous acetic acid solution, etc.) to separate the cellulose mixed fatty acid ester, and free metal components and sulfuric acid components are removed by washing with water. May be. In addition, a neutralizing agent can also be used in the case of washing with water.

(Post-processing process)
The post-treatment step is a step after neutralizing the acid catalyst in the neutralization step, and the product is precipitated and precipitated, the precipitated cellulose ester is filtered and separated, and the separated cellulose ester is washed, It preferably comprises a drying step.

[Precipitation]
As a poor solvent for precipitation, a mixed solution of water and carboxylic acid is preferably used, but is not limited to these poor solvents, and ketones, alcohols, ethers, esters and the like alone or in a water mixed solvent There may be.

The cellulose ester production method is most effectively used in the product precipitation step in the post-treatment step for the purpose of reducing the crystallized product. Moreover, you may reduce a crystallized substance by the manufacturing method of the said cellulose ester once using the taken-out cellulose ester.

[filtration]
The method for producing the cellulose ester resin is more preferably combined with a filtration step. The degree of purification of the cellulose ester resin is further improved by the filtration step.

The combined filtration step is preferably a method of filtering a solution obtained by adding a carboxylic acid to a cellulose ester, either before the start of the acylation step or before the precipitation step.

Various known filtration devices can be used for filtering the cellulose ester solution. That is, it can be divided into a continuous filter and a batch pressure filter when roughly classified as a filter, and as a continuous filter, it can be divided into a belt type, a multiple disk type, a screw press type, a filter press type, etc. Examples of the batch pressure filter include a leaf type and a candle type.

A filter press device, a paper filter device, a leaf filter device, a drum filter device, a precoat filter device, or the like can be used. The industrially most advantageous product is a filter press device, and the filter press device may be precoated and used. As an example of the filter press apparatus, 40 to 50 plates of about 60 cm square are used, and each plate is provided with a net, and filter paper or cotton cloth is installed between the nets. A plurality of these filter press apparatuses may be used for filtration in multiple stages. As the filter medium, a sintered metal filter, a non-woven metal filter, a cotton cloth filter, a paper filter, or the like may be used.

If it is a filter press type, the filter medium to be used can be a natural fiber or a synthetic fiber. In general, polypropylene, polyester (tetron), and nylon can be used as the material of the synthetic fiber used for the filter cloth. Vinylon, acrylic, saran, etc. can also be used depending on the solvent. Each of these materials has characteristics on the material and can be used according to the characteristics. If it is a natural fiber, cotton can be mentioned as a typical material. Monofilaments, multifilaments, spun yarns and the like can be used as the type of raw yarn used for the filter cloth. When a monofilament is used, the cake peelability is excellent and clogging is small, but there is a disadvantage that the fine particles are poorly captured. When multifilament is used, the strongest filter cloth is obtained and the cake peelability is good. In the case of spun yarn, cake peeling is poor and clogging is slightly faster. The filter cloth weave includes plain weave, twill weave, and satin weave. In the case of plain weave, particles are easily collected but clogging is accelerated. In the case of twill weave, a filter cloth having a good balance between trapping properties and clogging can be obtained. In the case of satin weaving, particles are less clogged, but the ability to collect particles is poor. A plain weave or twill filter cloth is suitable for the method for producing the cellulose ester.

For cotton cloth filters, cotton flannel (No. 10B, 63 plain weave diameter 20 single yarns, 46 weft 10 single yarns), gold width (11, 100 plain weave diameter 40 single yarns, 98 weft 40 single yarns) ), Thick twill (26, twill, 12-3, 64, 12-4, 32) may be used. In the paper filter, filter paper (300 g / m ² ) or the like may be used. These filter media may be used in combination (for example, the first filter media is one cotton flannel filter paper, the second filter media is two cotton flannels, one gold width, and the third filter media is one cotton flannel one filter paper, one gold width).

The retention particle size of the filter medium is preferably within the range of 1 to 50 μm. A range of 2 to 20 μm is more preferable, and a range of 3 to 15 μm is most preferable. By using such a filter medium, filterability is improved and productivity is improved.

The pressure in the filtration step can be appropriately set in consideration of the filtration efficiency. Specifically, the filter medium may be pressurized within a range of 5 to 18 atmospheres (for example, 8 to 18 atmospheres, for example, 10 to 18 atmospheres). The shape of the cellulose mixed fatty acid ester composition obtained by dissolving cellulose ester in an organic solvent, filtering and drying may be a filament. In the step of dissolving cellulose ester in an organic solvent and filtering, kaolin, titanium oxide, clay, or the like may be used as a filter aid. The filtrate may be kept warm in the range of 40 to 50 ° C. The filter medium may be pressurized within a range of 5 to 18 atmospheres (for example, 8 to 18 atmospheres, for example, 10 to 18 atmospheres). Filtration multiple times instead of once (for example, the first filter medium is a cotton flannel 1 filter paper, the second filter medium is a cotton flannel 1 sheet, a gold width 1 sheet, the third filter medium is a cotton flannel 1 sheet of filter paper 1 sheet of a gold width 1 sheet) The first filtration is performed within the range of 12 to 18 atm, the second filtration is performed within the range of 8 to 14 atm, and the third filtration is performed within the range of 5 to 9 atm. May be. When the same filter medium configuration is used, the filtration pressure may be changed between the first time and the second time (for example, the second filtration is performed at a lower pressure).

The retained particle size of the filter used for filtration is preferably in the range of 1 to 30 μm, more preferably in the range of 1 to 20 μm, and still more preferably in the range of 2 to 20 μm. By setting the retained particle size of the filter to 0.1 μm or more, it tends to be able to suppress a significant increase in the filtration pressure, and industrial production is also facilitated. Further, by setting the retained particle size to 30 μm or less, fine foreign matters can be removed, and therefore it is effective when combined with the precipitation step. Further, filtration may be performed by combining filters having different retention particle sizes.

The temperature at the time of filtration can be any temperature as long as filtration is possible, but it is preferably in the range of 30 to 100 ° C., more preferably in the range of 35 to 80 ° C., still more preferably 40 Heating in the range of ˜70 ° C. is preferable because the viscosity of the solution can be lowered.

Further, the filtration pressure is preferably within the range of 0.001 to 10 MPa, more preferably within the range of 0.001 to 5 MPa, and even more preferably within the range of 0.01 to 1 MPa.

In addition, as a filter aid, celite (for example, Filter-Cel, Celite 505, Standard Super-Cel, Celite 512, Hyflo Super-Cel, manufactured by Johns-Manville Sales Corp.) Celite 501, Celite 503, Celite 535, Celite 545, Celite 560, etc.), Dicalite [Superref, Specified Flow, Special Spec, made by Glefco, Inco, USA, Inc. (Grefco, Inco, USA) , Speedex, etc.), radio lights (RADIOLITE # manufactured by Showa Chemical Industry Co., Ltd.) 00, RADIOLITE # 200, RADIOLITE # 500, RADIOLITE # 600, RADIOLITE # 700, RADIOLITE # 900, RADIOLITE # 1100, RADIOLITE # 100), layered clay mineral (preferably talc, mica, kaolinite), silicon dioxide fine particles ( For example, silicon dioxide fine particles (for example, silica gel MB-300, MB-500 manufactured by Fuji Silysia Co., Ltd., Fuji silica gel AB type, Fuji silica gel A type, Fuji silica gel RD type, BW-25K, Merck Silica Gel 40, (Silica Gel 60, Silica Gel 100, etc.) etc. These filter aids may be mixed with a cellulose ester solution and subjected to cake filtration. Pre-coated on the solution may be filtered cellulose ester is dissolved.

(Alkali metals, Group 2 elements)
In the optical film of the present invention, the content of the alkali metal or the Group 2 element in the cellulose ester is preferably in the range of 1 to 150 ppm, respectively, from the viewpoint of generating a high molecular weight substance and reducing gelled foreign matter. In addition, content of an alkali metal or a Group 2 element means the total of the mass in terms of the atom of the alkali metal or Group 2 element contained in a cellulose ester.

When the content of the alkali metal or group 2 element in the cellulose ester is less than 1 ppm, neutralization of hydrogen ions generated during melt film formation becomes insufficient, and the compatibility between the acrylic resin and the cellulose ester deteriorates. There is a risk. On the other hand, when the content exceeds 150 ppm, white turbidity may occur and transparency may be lowered.

More preferably, the content of the alkali metal or group 2 element in the cellulose ester can be controlled within the range of 1 to 100 ppm by mass in terms of reducing surface roughness and reducing gelled foreign matter. More preferably, each is in the range of 1 to 50 ppm by mass.

In the present invention, the content of alkali metal or group 2 element in the cellulose ester can be measured by the following method.

First, the cellulose ester contained in a film is extracted. And the content of the alkali metal or the Group 2 element in the cellulose ester can be measured by the following atomic absorption method.
(1) Immerse the washed 50 ml capacity magnetic crucible in 2N aqueous nitric acid solution overnight.
(2) A magnetic crucible soaked in 2N nitric acid is washed with pure water, rinsed with ultrapure water, and dried in a drier.
(3) A 2 g film sample is precisely weighed in a magnetic crucible.
(4) Carbonize the sample in the magnetic crucible on the electric heater.
(5) Place the magnetic crucible in an electric furnace and incinerate at 500 ° C. for about 1 hour and at 600 ° C. for about 1.5 hours.
(6) When the ash is completely white, stop the electric furnace and let it cool in the furnace.
(7) Put 10 ml of 0.5N hydrochloric acid aqueous solution in a magnetic crucible and dissolve by heating on a sand bath. (8) The solution is allowed to cool and then transferred to a 50 ml volumetric flask using a washed funnel, and the magnetic crucible is washed with ultrapure water to make up the volume (hydrochloric acid concentration: 0.1 N).
(9) As a standard solution, a standard solution having a concentration of 1000 ppm is diluted with a 0.1N hydrochloric acid aqueous solution and prepared at concentrations of 0.1 ppm, 0.75 ppm, and 1.5 ppm.
(10) Measured by flame atomic absorption.

The calibration curve was created by the following method. The standard solution for the calibration curve was prepared by diluting a commercially available standard solution for atomic absorption (manufactured by Wako Pure Chemical Industries, Ltd.) with 0.1N hydrochloric acid aqueous solution to a concentration of 0.1, 0.75, 1.5 ppm. used. As the atomic absorption device, a trade name “AA-680” manufactured by Shimadzu Corporation was used.

The alkali metal is at least one selected from the group consisting of Li, Na, K, Rb, Cs, and Fr. Among these, at least one selected from the group consisting of Li, Na, and K is preferable from the viewpoint of suppressing coloring during heating, and more preferably K is included.

The group 2 element is at least one selected from the group consisting of Be, Mg, Ca, Sr, Ba, and Ra. Among them, at least one selected from the group consisting of Mg and Ca is preferable from the viewpoint of suppressing coloring during heating, and more preferably Mg is included.

These alkali metals and Group 2 elements may be used singly or in combination of two or more. Moreover, you may use together an alkali metal and a Group 2 element. When used in combination, the content is the total amount of all alkali metals and Group 2 elements contained in the film.

The alkali metal or Group 2 element is present in the film as a monovalent or divalent metal ion, or in the form of an inorganic salt or an organic fatty acid salt. Examples of the inorganic salt include alkali metal or group 2 element halides, hydroxides, oxides, sulfates, nitrates, silicates, and the like. In addition, natural products (for example, talc (Mg ₃ Si ₄ O ₁₀ (OH) ₂ ), etc.) containing an inorganic salt containing an alkali metal or a Group 2 element as a main component, or synthesized natural product-like compounds (synthesized) Hydrotalcite, for example Mg ₆ Al ₁₂ (OH) ₁₆ CO ₃ .4H ₂ O, Mg _4.5 Al ₁₂ (OH) ₁₃ CO ₃ .mH ₂ O (m = 3 to 3.5), Mg _{0.7 a} l0.3 O _1.15, etc., synthetic magnesium silicate _{(2MgO · 6SiO 2 · xH 2} O)) and the like are also suitable. Examples of the organic fatty acid salt include acetate, citrate, maleate and the like. Among them, it is preferable to exist in the form of an inorganic salt or metal ion such as Li, Na, K, Mg, Ca, etc., and an inorganic salt or metal ion of Na, Ca, Mg (Na ⁺ , Ca ²⁺ , Mg ²⁺ ) It is preferable to exist in the form of

The method for adjusting the content of the alkali metal or the Group 2 element in the cellulose ester resin is not particularly limited. For example, a desired amount of organic fatty acid salt or inorganic is added to the cellulose ester resin from which salt is removed or a resin composition containing the same. It can be adjusted by adding (adding) a salt. Moreover, the method of wash | cleaning using the water which adjusted each ion as washing | cleaning water in the manufacturing process of a cellulose-ester resin instead of adding salt directly is mentioned. In general, since water uses ground water and tap water, the ion content varies depending on the region. Therefore, it is preferable to measure and use the ion amount for each region. Adjust the amount of salt to be added; perform partial addition instead of adding all at once (repeat partial neutralization in the aging step (neutralize by adding a base continuously or intermittently)); Adjust the content of the metal contained in the cellulose ester resin by adjusting the amount of the recovered and recycled product used; or by selecting pure water adjusted for each ion amount and repeating washing; The content of the group element can be set to a desired range.

<Resin composition of acrylic resin and cellulose ester resin>
In the resin composition according to the present invention, the content mass ratio of the acrylic resin and the cellulose ester resin is such that the acrylic resin: cellulose ester resin has a mass ratio of 95: 5 to 30:70. This is necessary from the viewpoint of improving the heat resistance of the film, and is preferably in the range of 70:30 to 60:40. When the content ratio of the acrylic resin is within the above range, the characteristics of the cellulose ester resin can be sufficiently obtained, and the resulting film has a low brittleness and a small photoelastic coefficient.

In addition to the acrylic resin and the cellulose ester resin, the resin composition described above may further contain optional components such as an ultraviolet absorber, an antioxidant, a plasticizer, a retardation control agent, and fine particles as necessary. Good.

(UV absorber)
The ultraviolet absorber is a compound that absorbs ultraviolet rays having a wavelength of 400 nm or less, preferably a compound having a transmittance at a wavelength of 370 nm of 10% or less, more preferably 5% or less, and even more preferably 2% or less.

The light transmittance of the ultraviolet absorber can be measured with a spectrophotometer by a conventional method using a solution obtained by dissolving the ultraviolet absorber in a solvent (for example, dichloromethane, toluene, etc.). The spectrophotometer is, for example, a spectrophotometer UVIDFC-610 manufactured by Shimadzu Corporation, a 330-type self-recording spectrophotometer, a U-3210-type self-recording spectrophotometer, a U-3410-type self-recording spectrophotometer, manufactured by Hitachi, Ltd. -4000 self-recording spectrophotometer or the like can be used.

The ultraviolet absorber may be an oxybenzophenone compound, a benzotriazole compound, a salicylic acid ester compound, a benzophenone compound, a cyanoacrylate compound, a triazine compound, a nickel complex salt compound, an inorganic powder, etc. In order not to impair the transparency, benzotriazole-based UV absorbers and benzophenone-based UV absorbers are preferable, and benzotriazole-based UV absorbers are more preferable.

Specific examples of ultraviolet absorbers include 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, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin Tinuvins such as 328 and Tinuvin 928 (manufactured by BASF Japan Ltd.) are included.

The content of the ultraviolet absorber depends on the type of the ultraviolet absorber, but is preferably in the range of 0.5 to 10% by mass, and in the range of 0.6 to 4% by mass with respect to the optical film. More preferably.

(Antioxidant)
In the process of producing a film by the melt extrusion method, since a film material such as a resin is melt-kneaded at a high temperature, the film material such as a resin is easily decomposed by heat or oxygen. In order to suppress such decomposition of a film material such as a resin due to heat or oxygen, the resin composition according to the present invention preferably further contains an antioxidant as a stabilizer.

Examples of antioxidants include phenolic compounds, hindered amine compounds, phosphorus compounds, compounds containing unsaturated double bonds, and the like. Examples of the phenolic compound include a compound having a 2,6-dialkylphenol structure (for example, 2,6-di-t-butyl-p-cresol). Examples of commercially available phenolic compounds include Irganox 1076, Irganox 1010, manufactured by BASF Japan Ltd., and Adeka Stub AO-50, manufactured by ADEKA Corporation.

Examples of phosphorus compounds include tris (2,4-di-t-butylphenyl) phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite, and the like. Examples of commercially available phosphorus compounds include Sumitizer GP manufactured by Sumitomo Chemical Co., Ltd., ADK STAB PEP-24G manufactured by ADEKA Co., Ltd., ADK STAB PEP-36 and ADK STAB 3010, IRGAFOS P-EPQ manufactured by BASF Japan K.K. This includes GSY-P101 manufactured by Kogyo Corporation.

Examples of hindered amine compounds include Tinuvin 144 and Tinuvin 770 manufactured by BASF Japan Ltd., ADK STAB LA-52 manufactured by ADEKA Corp., and the like. These antioxidants may be only one kind or a mixture of two or more kinds.

Examples of the compound containing an unsaturated double bond include Sumitizer GM and Sumilizer GS manufactured by Sumitomo Chemical Co., Ltd.

The content of the antioxidant is preferably in the range of 1 ppm to 2.0% by mass relative to the resin component, more preferably 10 ppm to 1.0%, and more preferably 10 ppm to 0.1%. More preferably, it is within the range.

(Fine particles (matting agent))
The fine particles have a function of increasing the slipperiness of the surface of the obtained optical film. The fine particles may be inorganic fine particles or organic fine particles. Examples of the inorganic fine particles include silicon dioxide and zirconium oxide, and silicon dioxide is particularly preferable in order to reduce an increase in the haze of the film.

Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (above, manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), Nip Seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs), and the like.

The shape of the fine particles is irregular, acicular, flat or spherical, and is preferably spherical in order to ensure the transparency of the resulting film.

The size of the primary particles of fine particles or aggregates thereof is preferably in the range of 80 to 180 nm in order to obtain sufficient slipperiness. The size of the primary particles of the fine particles or the aggregates thereof can be obtained as an average value of the particle diameters of 100 particles by observing the particles with a transmission electron microscope at a magnification of 500 to 2 million times.

The content of the fine particles is preferably 0.01 to 5.0% by mass, more preferably 0.05 to 1.0% by mass with respect to the resin component described above. When the content of the fine particles is more than 5.0% by mass, aggregates can be reduced.

<Method for producing optical film by melt casting method>
FIG. 5 is a diagram schematically showing the steps of the melt casting film forming method preferable for the present invention.

In FIG. 5, the manufacturing method of the optical film of the present invention is such that after mixing film materials such as acrylic resin and cellulose ester resin, the extruder 1 is used to melt and extrude from the casting die 4 onto the first cooling roller 5. In addition to circumscribing the first cooling roller 5, the film is further circumscribed by a total of three cooling rollers, the second cooling roller 7 and the third cooling roller 8, in order to cool and solidify the film 10. Next, the film 10 peeled by the peeling roller 9 is then stretched in the width direction by gripping both ends of the film by the stretching device 12 and then wound by the winding device 16. In addition, an elastic touch roller 6 that clamps the molten film on the surface of the first cooling roller 5 is provided to correct the flatness. The elastic touch roller 6 has an elastic surface and forms a nip with the first cooling roller 5.

Extruder 1 is a melt-kneading extruder, and has a cylinder and a screw rotatably provided therein. A hopper (not shown) for supplying film material is provided at the supply port of the cylinder. The shape of the screw may be full flight, mudock, dull mage, etc., and is selected according to the viscosity of the molten resin and the required shearing force. The extruder 1 may be a single screw extruder or a twin screw extruder.

A filter 2 for filtering the molten resin may be further provided between the extruder 1 and the casting die 4. The filter 2 can be, for example, a leaf disk type filter. The filtration accuracy of the filter is preferably 3 to 15 μm. The material of the filter may be stainless steel or a sintered product thereof.

Between the extruder 1 and the casting die 4, a mixing device such as a static mixer 3 for uniformly mixing the resin, a gear pump (not shown) for stabilizing the extrusion flow rate, and the like are further provided. Also good.

The casting die 4 may be a known one, such as a T die. The material of the casting die 4 can be hard chrome, chromium carbide or the like. The lip clearance of the casting die 4 is preferably 900 μm or more, and more preferably in the range of 1 to 2 mm.

When foreign substances such as scratches and plasticizer aggregates adhere to the inner wall surface of the casting die 4, streaky defects (die lines) may occur on the surface of the extruded molten resin. In order to reduce surface defects such as a die line, a structure in which a resin staying portion is difficult to adhere to the inner wall surface from the extruder 1 to the tip of the casting die 4; The inner wall surface up to the tip of 4 is preferably free from scratches.

The inner wall surfaces of the extruder 1 and the casting die 4 are preferably subjected to surface processing for reducing the surface roughness or reducing the surface energy in order to make the molten resin difficult to adhere. Examples of such surface processing include processing for polishing to have a surface roughness of 0.2 S or less after hard chrome plating or ceramic spraying.

The cooling rollers 5, 7 and 8 are high-rigidity metal rollers and have a structure in which a temperature-controllable medium can be circulated. The surface material of the cooling rollers 5, 7, and 8 can be stainless steel, aluminum, titanium, or the like. The surface of the cooling rollers 5, 7 and 8 may be subjected to a surface treatment such as hard chrome plating in order to facilitate the peeling of the resin. The arithmetic average roughness Ra of the surfaces of the cooling rollers 5, 7 and 8 is preferably 0.1 μm or less, and more preferably 0.05 μm or less in order to keep the haze of the resulting film low.

The elastic touch roller 6 is disposed to face the cooling roller 5. The molten resin extruded from the casting die 4 is nipped between the cooling roller 5 and the elastic touch roller 6. As the elastic touch roller 6, a silicon rubber roller covered with a thin film metal sleeve described in JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096 and the like is used.

The stretching apparatus 12 is not particularly limited, but a roller stretching machine, a tenter stretching machine, or the like is preferably used. A roller stretching machine and a tenter stretching machine may be combined. The tenter stretching machine preferably has a preheating zone, a stretching zone, a holding zone, and a cooling zone, and preferably has a neutral zone for insulating between the zones.

Next, the step of obtaining an optical film using a film manufacturing apparatus will be described. The optical film is, for example, a step of preparing pellets made of the resin composition described above (pelletizing step); a step of melt-kneading the film material containing the pellets with the extruder 1 and then extruding from the casting die 4 (melt extrusion) Step); a step of obtaining a film by cooling and solidifying the extruded molten resin (cooling and solidification step); and a step of stretching the film (stretching step).

(Pelletization process)
The resin composition containing the acrylic resin and cellulose ester is preferably kneaded and pelletized in advance. Pelletization can be performed by a known method. For example, the above resin composition is melt-kneaded with an extruder and then extruded from a die in a strand shape. The molten resin extruded in a strand form can be cooled with water or air, and then cut to obtain pellets.

The raw material of the pellet is preferably dried before being supplied to the extruder 1 in order to prevent decomposition. For example, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more so that the water content is 200 ppm or less, preferably 100 ppm or less.

The mixture of the antioxidant and the resin component may be mixed with each other; the antioxidant dissolved in the solvent may be impregnated with the resin component; and the antioxidant may be mixed with the resin. The ingredients may be sprayed and mixed. A vacuum nauter mixer or the like is preferable because the raw materials can be dried and mixed at the same time. The atmosphere in the vicinity of the hopper of the extruder 1 and in the vicinity of the exit of the casting die 4 is preferably an atmosphere of dehumidified air or N ₂ gas in order to prevent deterioration of the raw material of the pellet.

In the extruder 1, it is preferable to knead at a low shearing force or at a low temperature so as not to cause deterioration of the resin (decrease in molecular weight, increase in coloration, generation of high molecular weight bodies or gel-like foreign matters, etc.). For example, when kneading with a twin-screw extruder, it is preferable to use a deep groove type screw and to rotate the two screws in the same direction. In order to knead uniformly, it is preferable that two screw shapes mesh with each other.

Instead of pelletizing the resin composition, an optical film may be produced by melting and kneading the resin composition that has not been melt-kneaded as a raw material in the extruder 1 as it is.

(Melt extrusion process)
The obtained molten pellets and other additives as required are fed from the hopper to the extruder. The supply of pellets is preferably performed under vacuum, reduced pressure, or inert gas atmosphere in order to prevent oxidative decomposition of the pellets. Then, in the extruder 1, the film material containing the molten pellet is melt-kneaded.

Although the melting temperature of the film material in the extruder 1 depends on the type of the film material, it is preferably in the range of Tg to (Tg + 100) ° C., more preferably when the glass transition temperature of the film is Tg. It is within the range of (Tg + 10) to (Tg + 90) ° C. The residence time of the film material in the extruder 1 is preferably 5 minutes or less. The residence time can be adjusted by the number of rotations of the screw, the depth of the groove, L / D which is the ratio of the cylinder length (L) to the cylinder inner diameter (D), and the like.

The molten resin extruded from the extruder 1 is filtered with a filter 2 or the like as necessary, and further mixed with a static mixer 3 or the like, and extruded from a casting die 4 into a film. The melting temperature Tm of the resin at the exit portion of the casting die 4 can be about 200 to 300.degree.

(Cooling solidification process)
The resin extruded from the die is nipped between the cooling roller 5 and the elastic touch roller 6 so that the film-like molten resin has a predetermined thickness. Then, the film-like molten resin is cooled stepwise with a plurality of cooling rollers 7 and 8 and solidified.

The surface temperature Tr1 of the cooling roller 5 can be Tg or less, where Tg is the glass transition temperature of the resulting film. The surface temperature Tr2 of the second cooling roller 7 can be (Tg−50) ° C. ≦ Tr2 ≦ Tg ° C. The film surface temperature Tt on the elastic touch roller 6 side can be (Tr1-50) ° C. ≦ Tt ≦ (Tr1-5) ° C.

The film-shaped molten resin solidified by the cooling rollers 5, 7 and 8 is peeled by the peeling roller 9 to obtain a web. When peeling the film-like molten resin, it is preferable to adjust the tension in order to prevent deformation of the resulting web.

(Stretching process)
The obtained web is stretched by the stretching device 12 to obtain a film. The stretching may be performed in at least one direction, and is preferably performed in both the web width direction (TD direction) and the web conveyance direction (MD direction).

When stretching in both the web width direction (TD direction) and the web conveyance direction (MD direction), the web width direction (TD direction) stretching and the web conveyance direction (MD direction) stretching are sequential. Or may be performed simultaneously.

The draw ratio may be 1.01 to 3.0 times, preferably 1.1 to 2.0 times in each direction. When stretching in both the web width direction (TD direction) and the web conveyance direction (MD direction), the final direction is 1.01 to 3.0 times, preferably 1.1 to 2.0 times in each direction. It is preferable to do.

The stretching temperature is preferably Tg to (Tg + 50) ° C. The stretching temperature is preferably uniform in the width direction of the web (TD direction) or the transport direction (MD direction), and the variation in the width direction or transport direction of the web stretching temperature is preferably ± 2 ° C. or less, The temperature is more preferably ± 1 ° C. or less, and further preferably ± 0.5 ° C. or less.

In order to adjust the retardation of the film obtained after stretching or reduce dimensional change, the film obtained after stretching is shrunk in the transport direction (MD direction) or the width direction (TD direction) as necessary. May be. To shrink the film obtained after stretching in the transport direction (MD direction), for example, release the clip gripped in the width direction and loosen it in the transport direction; gradually reduce the interval between adjacent clips in the transport direction. To relax in the transport direction.

The width of the obtained optical film is preferably in the range of 1.3 to 4 m, and more preferably in the range of 1.4 to 3.0 m.

The total content of the acrylic resin and the cellulose ester resin in the obtained optical film is preferably 55% by mass or more, more preferably 60% by mass or more, and 70% by mass or more with respect to the optical film. More preferably.

As described above, in the acrylic resin according to the present invention, the weight average molecular weight Mw is not more than a certain value, and the content of residual components such as unreacted monomers, radical polymerization initiators or chain transfer agents is adjusted to be not more than a certain amount. Therefore, the production of a high molecular weight resin can be reduced when the acrylic resin and the cellulose ester resin are melt-kneaded. Therefore, even if the optical film is a thin film, surface roughness does not occur.

<Physical properties of optical film>
(Film thickness)
The thickness of the optical film is not particularly limited, but is preferably in the range of 10 to 35 μm, more preferably in the range of 10 to 30 μm, and in the range of 15 to 25 μm It is particularly preferable for providing a film.

(Phase difference)
The retardation value Ro in the in-plane direction of the optical film is preferably in the range of 0 to 100 nm, and more preferably in the range of 0 to 250 nm. The retardation value Rt in the thickness direction is preferably in the range of −100 to 100 nm, and more preferably in the range of −50 to 50 nm. The retardation value can be adjusted by, for example, the content ratio of acrylic resin and cellulose ester, stretching conditions, and the like.

Retardation values Ro and Rt are represented by the following formulas, respectively.

Formula _{(I) Ro = (n x} -n y) × d
Formula (II) Rt = {(n _x + n _y ) / 2−n _z } × d
(N _x: the slow axis direction of the refractive index of the film plane, n _y: the film plane, the refractive index in the direction perpendicular to the slow axis, n _z: refractive index of the film in the thickness direction, d : Film thickness (nm)
The retardation values Ro and Rt can be determined by the following method, for example.

(1) The average refractive index of the film is measured with a refractometer.

(2) Retardation value Ro in the in-plane direction when light having a wavelength of 590 nm is incident from the normal direction of the film by KOBRA-21AWR manufactured by Oji Scientific Instruments in an environment of a temperature of 23 ° C. and a relative humidity of 55% RH. Measure.

(3) Retardation value R (θ) when light having a wavelength of 590 nm is incident from the angle θ (incident angle (θ)) with respect to the film normal direction by using KOBRA-21AWR manufactured by Oji Scientific Instruments. To do. θ is greater than 0 °, preferably in the range of 30 ° to 50 °.

(4) From the measured Ro and R (θ) and the above-mentioned average refractive index and film thickness, nx, ny and nz are calculated by KOBRA-21AWR manufactured by Oji Scientific Instruments, and Rt is calculated.

The angle θ1 (orientation angle) formed by the in-plane slow axis of the optical film and the width direction of the film is preferably −5 ° or more and + 5 ° or less, and more preferably −1 ° or more and + 1 ° or less. . The orientation angle θ1 of the optical film can be measured using an automatic birefringence meter KOBRA-21AWR (Oji Scientific Instruments).

(Haze)
The haze of the optical film measured in accordance with JIS K-7136 is preferably less than 1.0%, more preferably 0.2% or less, and 0.1% or less. More preferably, it is particularly preferably 0.05% or less. In order to reduce the haze of the optical film, as described above, for example, the amount of residual components contained in the acrylic resin is set to a certain level or less, and the generation of gel-like foreign matters is suppressed by using a purified cellulose ester resin preferable for the present invention. Is preferred.

The haze of the optical film can be measured by a method based on JIS K-7136; specifically, the following method can be used.

(1) The obtained optical film is conditioned at a temperature of 23 ° C. and a relative humidity of 55% RH for 5 hours or more. Thereafter, dust attached to the surface of the film is removed with a blower or the like.

(2) Next, the haze of the optical film is measured with a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.) under the condition of 23 ° C. and 55% RH. The light source of the haze meter may be a 5V9W halogen sphere, and the light receiving part may be a silicon photocell (with a relative visibility filter).

(Transmittance)
The total light transmittance of the optical film is preferably 90% or more, and more preferably 93% or more. The total light transmittance can be measured with a spectrophotometer. The spectrophotometer is, for example, a spectrophotometer UVIDFC-610 manufactured by Shimadzu Corporation, a 330-type self-recording spectrophotometer, a U-3210-type self-recording spectrophotometer, a U-3410-type self-recording spectrophotometer, manufactured by Hitachi, Ltd. -4000 self-recording spectrophotometer or the like can be used.

(Glass-transition temperature)
The glass transition temperature of the optical film is preferably in the range of 110 to 200 ° C, and more preferably in the range of 120 to 190 ° C. The glass transition temperature of the optical film can be measured by a method based on JIS K7121 (1987). Specifically, using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer), the glass transition temperature (Tmg) when the optical film was heated at a heating rate of 20 ° C./min. Can be measured as

(Moisture permeability)
The moisture permeability of the optical film at 40 ° C. and 90% RH measured in accordance with JIS Z 0208 is preferably in the range of 200 to 1500 (g / (m ² · 24 hr)), and is preferably 400 to 1200 ( g / (m ² · 24 hr)) is more preferable. In order to reduce the moisture permeability of the optical film, for example, the content ratio of the acrylic resin may be increased.

<Polarizing plate>
The optical film of the present invention is suitable for bonding to a polarizer to produce a polarizing plate.

(Polarizer production)
A polarizer is an element that allows only light having a polarization plane in a certain direction to pass therethrough. A typical example of the polarizer is a polyvinyl alcohol-based polarizing film, and there are one in which a polyvinyl alcohol-based film is dyed with iodine and one in which a dichroic dye is dyed.

The polarizer may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing with iodine or a dichroic dye, or after dyeing a polyvinyl alcohol film with iodine or a dichroic dye, A uniaxially stretched film (preferably a film further subjected to durability treatment with a boron compound) may be used. The thickness of the polarizer is preferably in the range of 5 to 30 μm, more preferably in the range of 10 to 20 μm.

The polyvinyl alcohol film may be a film formed from a polyvinyl alcohol aqueous solution. The polyvinyl alcohol film is preferably an ethylene-modified polyvinyl alcohol film because it is excellent in polarizing performance and durability performance and has few color spots. Examples of the ethylene-modified polyvinyl alcohol film include an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99 described in JP-A Nos. 2003-248123 and 2003-342322. 0.0-99.99 mol% film is included. In addition, it is preferable to prepare a polarizer by the method described in JP 2011-1000016 A, JP 4691205 A, and JP 4804589 A, and laminate the polarizer with the optical film of the present invention.

Examples of dichroic dyes include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes and anthraquinone dyes.

(Preparation of polarizing plate)
The optical film of the present invention may be disposed directly on at least one surface of the polarizer, or may be disposed via another film or layer.

When the optical film of the present invention is disposed on one surface of the polarizer, a protective film (other protective film) other than the optical film of the present invention may be disposed on the other surface of the polarizer. Other protective films are not particularly limited, and may be ordinary cellulose ester films and the like. Examples of commercially available cellulose ester films include commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC4UY, KC4UY, CC6UY KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, 2UAH, KC4UAH, KC6UAH, and above, manufactured by Konica Minolta Advanced Layer Co., Ltd.) are preferably used.

The polarizing plate can be usually obtained through a step of bonding a polarizer and the above-described optical film. As an example of the adhesive used for bonding, a completely saponified polyvinyl alcohol aqueous solution or the like is preferably used.

In addition, the optical film of the present invention and the polarizer can be bonded together using an active energy ray-curable adhesive or the like, but the resulting adhesive layer has a high elastic modulus and deforms the polarizing plate. From the viewpoint of easy suppression, it is preferable to use a photocurable adhesive.

Preferred examples of the photocurable adhesive include (α) cationic polymerizable compound, (β) photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm, as disclosed in JP 2011-08234 A. And a photo-curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other photocurable adhesives may be used.

Hereinafter, an example of a method for producing a polarizing plate using a photocurable adhesive will be described. The polarizing plate includes (1) a pretreatment step for easily adhering the surface of the optical film to which the polarizer is bonded, and (2) at least one of the adhesive surfaces of the polarizer and the optical film. (3) A bonding step of bonding the polarizer and the optical film through the obtained adhesive layer, and 4) A polarizer and the optical film are bonded through the adhesive layer. It can manufacture by the manufacturing method including the hardening process which hardens an adhesive bond layer in the match | combined state. What is necessary is just to implement the pre-processing process of (1) as needed.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the adhesive surface of the optical film with the polarizer. When bonding an optical film to both surfaces of a polarizer, easy adhesion processing is performed on the bonding surface of each optical film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Adhesive application process)
In the adhesive application step, the photocurable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When the photocurable adhesive is directly applied to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting a photocurable adhesive between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(Bonding process)
Thus, after apply | coating a photocurable adhesive agent, it uses for a bonding process. In this bonding step, for example, when a photocurable adhesive is applied to the surface of the polarizer in the previous application step, an optical film is superimposed thereon. When a photocurable adhesive is applied to the surface of the optical film in the previous application step, a polarizer is superimposed thereon. In addition, when a photocurable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In the case where the optical film is bonded to both surfaces of the polarizer, and the photocurable adhesive is used on both surfaces, the optical film is superimposed on the both surfaces of the polarizer via the photocurable adhesive. Usually, in this state, both sides (if the optical film is superimposed on one side of the polarizer, the polarizer side and the optical film side, and if the optical film is superimposed on both sides of the polarizer, The film is pressed with a roller or the like from the film side). As the material of the roller, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, the active energy ray is irradiated to the uncured photocurable adhesive to cure the adhesive layer containing the epoxy compound or the oxetane compound. Thereby, the overlapped polarizer and the optical film are bonded via the photocurable adhesive. When bonding an optical film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or an optical film side. Moreover, when bonding an optical film on both surfaces of a polarizer, an active energy ray is applied from either one of the optical films in a state where the optical film is superimposed on both surfaces of the polarizer via a photocurable adhesive. It is advantageous to irradiate and simultaneously cure the photocurable adhesive on both sides.

As the active energy rays, visible rays, ultraviolet rays, X-rays, electron beams and the like can be used, and since they are easy to handle and have a sufficient curing rate, electron beams or ultraviolet rays are generally preferably used.

Any appropriate conditions can be adopted as the electron beam irradiation conditions as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. When the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. When the acceleration voltage exceeds 300 kV, the penetrating force through the sample is too strong and the electron beam rebounds, and an optical film or polarized light. There is a risk of damaging the child. The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent optical film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can harden the said adhesive agent. Preferably the dose of ultraviolet rays in the range of 50 ~ 1500mJ / cm ² in accumulated light amount, and even more preferably in the range of within the range of 100 ~ 500mJ / cm ^2.

<Liquid crystal display device>
The liquid crystal display device includes a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell. And at least one is a polarizing plate which has the optical film of this invention among a pair of polarizing plates, More preferably, both of a pair of polarizing plates are polarizing plates which have the optical film of this invention.

The display method of the liquid crystal cell is not particularly limited, and is a TN (Twisted Nematic) method, an STN (Super Twisted Nematic) method, an IPS (In-Plane Switching) method, an OCB (Optically Compensated Birefringence Ventilation method). (MVA: Multi-domain Vertical Alignment and PVA; including Patterned Vertical Alignment), HAN (Hybrid Aligned Nematic), etc. From the viewpoint of a relatively wide viewing angle, the IPS system is preferable, and from the viewpoint of high contrast, the VA system is preferable.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

1. Preparation of optical film material (A) Acrylic resin Monomers that serve as raw materials for the acrylic resin are shown below.

Methyl methacrylate (MMA): Asahi Kasei Chemicals Corporation
Acryloylmorpholine (ACMO): manufactured by Kojin Co., Ltd. (Synthesis Example 1)
An acrylic resin was synthesized according to the flow shown in FIG. 4 using the monomer material described above. That is, as shown in FIG. 4, methyl methacrylate (MMA) and acryloylmorpholine (ACMO) are added to a 10 L catalyst dissolution tank (SUS304, with paddle blade agitator, with jacket), MMA is 88.8% by mass, Charged so that ACMO is 11.2% by mass (so that the total charge molar ratio is MMA / ACMO = 85/15); 2,2′-azobis (2-methylpropio) as a polymerization initiator Nitrile) (AIBN) was added in an amount of 0.262% by mass based on the total amount of monomer components contained in the catalyst solution and monomer mixture described below. These components were mixed with stirring, and AIBN was completely dissolved to obtain a catalyst solution. A refrigerant was adjusted through the jacket so that the temperature in the catalyst dissolution tank was 5 ° C. The obtained catalyst solution was continuously fed to a 10 L polymerization reactor (SUS304, with a helical ribbon blade agitator, with a jacket) at a flow rate of 1.47 kg / Hr by a pump.

On the other hand, in a 20 L monomer preparation tank (SUS304, with paddle blade stirrer, with jacket), methyl methacrylate (MMA) and acryloylmorpholine (ACMO) are contained, MMA is 88.8 mass%, and ACMO is 11.2 mass. The n-octyl mercaptan as a chain transfer agent was further added to 0.137% by mass with respect to the total amount of monomer components contained in the catalyst solution and the monomer mixture. These components were mixed with stirring. The refrigerant was adjusted through the jacket so that the temperature in the monomer preparation tank was 5 ° C. The obtained monomer mixed solution was fed to the aforementioned polymerization reactor by a pump at a flow rate of 13.279 kg / hr.

From the lower part of the polymerization reactor, the catalyst solution and the monomer mixture are added, and the polymerization reaction is carried out at an average residence time of 26 minutes at a temperature of 175 ° C. ± 2 ° C. until an average polymerization rate of 56% by mass. A liquid polymer composition was obtained. Thereafter, the obtained liquid polymer composition was taken out from the upper part of the polymerization reactor and fed to a heater (inner diameter 16.7 mm × length 3 m, with jacket).

The obtained polymer composition was fed to a devolatilizing extruder while heating the liquid polymer composition to 20 kg / cm ² G and 200 ° C. in a heater. The devolatilizing extruder is a twin screw extruder (TEX-30) manufactured by Nippon Steel Co., Ltd., different direction rotation method, screw diameter 30 mm, cylinder length 1200 mm, 1 rear vent, 3 fore vents. Using. Each vent of the devolatilizing extruder was evacuated, the cylinder temperature was about 250 ° C., the liquid polymer composition was devolatilized, and volatile components mainly composed of unreacted monomers were taken out from the vent. The taken-out unreacted monomer was recovered in a monomer recovery tower (inner diameter 100 mm, length 3 m, SUS304, 3/8 inch SUS Raschig ring packed tower, concentration section length 0.7 m, recovery section length 0.3 m).

The obtained polymer in a molten state was extruded into a strand shape, cooled with water, and then cut to obtain pellets. Thus, acrylic resin A1 was obtained at an average rate of 13.5 kg / hr.

The contents of the monomer, polymerization initiator and chain transfer agent remaining in the obtained acrylic resin A1 were measured by the following method. That is, 0.1 g of acrylic resin was dissolved in 2 ml of acetone and sonicated for 30 minutes. To this solution, 50 ppm of ethylene glycol monomethyl ether as an internal standard component was added, and then diluted to 10 ml with hexane to obtain a sample solution. The contents of the monomer, polymerization initiator, and chain transfer agent contained in this sample solution were measured by GC / MS. The GC / MS measurement apparatus and measurement conditions were as follows.

Equipment: HP 6890GC / HP5973MSD (manufactured by Hewlett-Packard)
Column: DB-624 (0.25 mm. × 30 ML.) Manufactured by J & W
Oven program: 40 ° C (3min) -20 ° C / min-230 ° C (8min)
Inj: 160 ° C
AUX: 250 ° C
(Synthesis Examples 2 to 6)
Exhaust amount of volatile components (including monomer) from the vent of the devolatilizing extruder and polymerization temperature or polymerization time in the polymerization reactor so that the content of the remaining monomer is within the range shown in Table 1. Acrylic resins A2 to A6 were obtained in the same manner as in Synthesis Example 1 except for the changes.

However, the acrylic resin A2 tried to reduce the content of residual unreacted monomer to 50 ppm, but it was difficult to reduce it.

(Synthesis Examples 7 to 10)
Synthesis was performed except that the amount of the polymerization initiator charged into the catalyst preparation tank and the polymerization temperature or polymerization time in the polymerization reactor were changed so that the content of the remaining polymerization initiator was within the range shown in Table 1. In the same manner as in Example 1, acrylic resins A7 to A10 were obtained.

However, the acrylic resin A7 tried to reduce the content of the residual polymerization initiator to 5 ppm, but it was difficult to reduce.

(Synthesis Examples 11 to 14)
Other than changing the charge amount of the chain transfer agent to the monomer preparation tank and the polymerization temperature or polymerization time in the polymerization reactor so that the content of the remaining chain transfer agent is within the range shown in Table 1 Acrylic resins A11 to A14 were obtained in the same manner as in Synthesis Example 1.

However, although the acrylic resin A11 tried to reduce the content of the residual chain transfer agent to 5 ppm, the reduction was difficult.

(Synthesis Examples 15 and 16)
Acrylic resins A15 and A16 were obtained in the same manner as in Synthesis Example 1 except that the monomer composition of the acrylic resin was changed as shown in Table 1.

(Synthesis Examples 17 to 22)
The same procedure as in Synthesis Example 1 except that the amount of radical polymerization initiator charged and the polymerization time in the polymerization reactor were changed so that the weight average molecular weight (Mw) of the resulting acrylic resin was within the range shown in Table 1. Thus, acrylic resins A17 to A22 were obtained.

However, the acrylic resin A22 tried to reduce the content of residual unreacted monomer to 50 ppm, the content of residual polymerization initiator to 5 ppm, and the content of residual chain transfer agent to 5 ppm, but it was difficult to reduce.

The composition and physical properties of the acrylic resin obtained are summarized in Table 1.

　（Ｂ）セルロースエステル樹脂
　下記のセルロースエステル樹脂の合成で用いる原料セルロースエステルＡ～Ｅのアセチル基置換度、プロピオニル基置換度、ブチリル基置換度及び重量平均分子量（Ｍｗ）を表２に示す。なお、表２に記載のセルロースエステルは下記の商品として購入又は合成した。

(B) Cellulose Ester Resin Table 2 shows the acetyl group substitution degree, propionyl group substitution degree, butyryl group substitution degree, and weight average molecular weight (Mw) of raw material cellulose esters A to E used in the synthesis of the following cellulose ester resins. In addition, the cellulose ester of Table 2 was purchased or synthesize | combined as the following goods.

　（セルロースエステルＢ１の合成）
　２０ｇのセルロースエステルＡ（原料セルロースエステル）に、セルロースエステル溶液の溶媒として１８ｇの水、１００ｇのアセトン及び１００ｇのＴＨＦを加え、５０℃で撹拌して溶解し、セルロースエステル溶液を調製した。 A: CAP381-20 (Eastman Chemical)
B: DAC L50 (Daicel Chemical Industries)
C: SCAP (synthesized by a known method)
D: CAP504-0.2 (Eastman Chemical)
E: CAP482-0.5 (Eastman Chemical)

(Synthesis of cellulose ester B1)
To 20 g of cellulose ester A (raw material cellulose ester), 18 g of water, 100 g of acetone and 100 g of THF were added as a solvent for the cellulose ester solution and dissolved by stirring at 50 ° C. to prepare a cellulose ester solution.

In Table 3, the raw material cellulose ester, its mass, the solvent of the cellulose ester solution, its mass and dissolution temperature are shown.

A poor solvent composed of 100 g of water, 50 g of acetone and 50 g of THF was dropped into the cellulose ester solution prepared as described above at a dropping temperature of 25 ° C. over 2 hours.

After completion of dropping, the mixture was stirred at 25 ° C. for 2 hours, and the precipitated granular solid was filtered. The filtrate was washed with pure water until the pH of the filtrate became 7, and then dried at 60 ° C. to obtain a cellulose ester resin B1.

Table 4 shows the poor solvent, the dropping temperature, the dropping time, and the stirring time.

(Synthesis of cellulose esters B2 to B6)
In cellulose ester B1, the raw material cellulose ester, its mass (g), the solvent of the cellulose ester solution, the dissolution temperature, the poor solvent temperature condition, its dropping temperature / time and stirring time were changed as shown in Table 3 and Table 4. Otherwise, the same operation was performed to obtain cellulose esters B2 to B6 shown in Tables 3 and 4.

When acetic acid was used as the solvent, after filtration, the filtrate was washed with pure water until the pH of the filtrate became 7 as measured at a temperature of 23 ° C.

　（ＳＰ値の数値ｓとａ値）
　表３、表４に示したセルロースエステル溶液と貧溶媒を混合した後の溶媒全体のＳＰ値を、Ｐｏｌｙｍｅｒ　Ｈａｎｄ　Ｂｏｏｋ　（Ｓｅｃｏｎｄ　Ｅｄｉｔｉｏｎ）第IV章　Ｓｏｌｕｂｉｌｉｔｙ　Ｐａｒａｍｅｔｅｒ　Ｖａｌｕｅｓより求め、その数値をｓとした。

(SP value numerical value s and a value)
The SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent shown in Tables 3 and 4 was determined from Polymer Hand Book (Second Edition) Chapter IV, Solubility Parameter Values, and the value was taken as s.

Further, the a value was obtained from the following formula (1) using the total number of acyl groups carbon t per glucose unit of the cellulose ester shown in Table 2.

Formula (1) a = s + 0.8t
(In the formula, s is the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent, and t is the total number of acyl group carbon atoms per glucose unit of the cellulose ester. 0.8t above) Is a term relating to the contribution of the acyl group to the SP value.)
The a value preferably satisfies the following formula (2) for controlling the crystallized product shape.

Formula (2) 31 ≦ a ≦ 40
(Evaluation of crystallized shape)
The total amount of the obtained crystallized product was sieved, and the ratio of the mass of the crystallized product remaining on the 15 mm sieve with respect to the total mass of the crystallized product was calculated to evaluate the crystallized product shape. It can be said that the smaller the amount of crystallized matter remaining on the sieve, the better the crystallized product having a better shape and the more refined cellulose ester resin.

The results are shown in Table 5.

(Alkali metal or Group 2 element content)
The type and content of alkali metal and the type and content of Group 2 element were measured by the above methods. The results are shown in Table 5.

　２．光学フィルムの作製
　（実施例１）
　下記成分を、真空ナウターミキサーにて８０℃、１Ｔｏｒｒの条件下で３時間混合しながら乾燥させて、混合物を得た。

2. Production of optical film (Example 1)
The following components were dried in a vacuum nauter mixer with mixing at 80 ° C. and 1 Torr for 3 hours to obtain a mixture.

<Composition of the mixture>
(Resin composition)
Acrylic resin A1 obtained in Synthesis Example 1 (dried at 90 ° C. for 3 hours to obtain a water content of 1000 ppm) 65 parts by mass Cellulose ester B6 35 parts by mass (additive)
Tinuvin 928 (manufactured by BASF Japan) 1.1 parts by mass GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.25 parts by mass Irganox 1010 (manufactured by BASF Japan) 0.5 parts by weight Sumizer GS (Sumitomo Chemical) 0.24 parts by mass Aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by mass Sea Hoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) 0.02 parts by mass It melt-kneaded at 235 degreeC with the extruder, and extruded to strand form. The resin composition extruded in a strand form was cooled with water and then cut to obtain pellets.

The obtained pellets were dried by circulating dehumidified air at a temperature of 70 ° C. for 5 hours or more, and then put into a single screw extruder while maintaining the temperature at 100 ° C. The moisture content of the pellets charged into the single screw extruder was 120 ppm.

Using the obtained pellets, a film was produced using the film production apparatus shown in FIG. That is, the obtained pellets were melt-kneaded at 235 ° C. with a single screw extruder (extruder 1), and then extruded from the T die (die 4) onto the cooling roller 5 having a surface temperature of 90 ° C. And after pressing the resin extruded on the cooling roller 5 with the elastic touch roller 6 whose surface metal layer has a thickness of 2 mm, the resin is further cooled with the cooling roller 7 and the cooling roller 8 to have a thickness of 60 μm. Got the web.

The cooled and solidified web was peeled off by the peeling roller 9 and then stretched by a roller stretching machine at 175 ° C. in the web conveyance direction (MD direction) at a stretching ratio of 1.6 times (60%). The obtained film was introduced into a tenter stretching machine having a preheating zone, a stretching zone, a holding zone, and a cooling zone, and further having a neutral zone between each zone. And it extended | stretched 1.7 times (70%) of draw ratios at 175 degreeC in the width direction (TD direction) of the film with the tenter drawing machine. Then, it cooled until the film temperature became 30 degreeC, and the clip of the tenter stretching machine was removed. And the both ends of the width direction of a film were cut off, and the optical film with a film thickness of 20 micrometers and a film width of 2500 mm was obtained.

(Examples 2 to 13)
In the same manner as in Example 1, except that the content of the residual unreacted monomer, the residual polymerization initiator, and the residual chain transfer agent in the acrylic resin A1 was changed to the acrylic resin type as shown in Table 6. A film was obtained.

(Examples 14 to 18)
An optical film was obtained in the same manner as in Example 1 except that the type of cellulose ester resin was changed as shown in Table 6.

(Examples 19 to 21)
An optical film was obtained in the same manner as in Example 1 except that the thickness of the optical film was changed as shown in Table 6.

(Comparative Examples 1 to 5)
An optical film of a comparative example was obtained in the same manner as in Example 1 except that acrylic resins A6, A10, A14, and A17 containing a large amount of residual unreacted monomer, residual polymerization initiator, and residual chain transfer agent were used. .

Further, an optical film of a comparative example was obtained in the same manner as in Example 1 except that acrylic resin A16 in which the composition ratio (mass%) of MMA and ACMO was changed to 30:70 was used.

<Evaluation 1>
About the said resin composition, calculation of the high molecular weight body formation rate H was performed.

(1) Calculation of high molecular weight product generation rate H A resin composition containing acrylic resin and cellulose ester resin as a sample in a mass ratio of 65:35 is a thermal analyzer manufactured by SII (EXSTAR6000 TG / DTA). The sample was melted by heating for about 1 hour while keeping the temperature at 260 ° C. in a nitrogen stream using about 5 to 10 mg of the sample.

Using the obtained resin composition before and after heating and melting, the molecular weight was measured by the following GPC.

GPC measurement conditions are as follows.

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 Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

As shown in FIG. 2, the detection sensitivity value difference obtained by subtracting the detection sensitivity value of GPC before heating and melting from the detection sensitivity value of GPC after heating and melting is plotted against the horizontal axis molecular weight (Mw). The positive difference area (a) shown in FIG. The positive differential area (a) was defined as the area on the high molecular weight side from the molecular weight value indicating the GPC detection sensitivity peak value before heating of the resin composition.

To obtain the above areas (a) and (b) from the obtained GPC waveform, the area was obtained using a multi-station GPC-8020 model II manufactured by Tosoh Corporation.

The high molecular weight product formation rate H is a value obtained by dividing the positive difference area (a) by the peak area (b) of the GPC before heating, and was obtained by the following formula.

Formula H = (a / b) × 100 (%)
<Evaluation 2>
The obtained optical film was measured for (2) surface roughness and (3) generation of gel-like foreign matters by the following method. All measurements were performed in an atmosphere of a temperature of 23 ° C. and a relative humidity of 55% RH. The optical film used was stored in advance in an atmosphere of a temperature of 23 ° C. and a relative humidity of 55% RH for 24 hours.

(2) Surface Roughness Surface roughness refers to a state where the surface of the optical film obtained by casting film formation is rough like a pine bark or dry rice paper.

(Rough surface evaluation method)
The optical film is irradiated with light from a point light source at an angle of 45 degrees, an image projected on a plain screen is observed, and the surface roughness of a pine skin or dried rice paper is visually confirmed.

◎ ・ ・ ・ Cannot be confirmed before or after stretching ○ ・ ・ ・ Can be confirmed before stretching, but cannot be confirmed when stretched × ・ ・ ・ Can be confirmed even when stretched (3) Gel-like foreign material Melt casting film formation 1 m ² minutes were cut out from the winding of the optical film obtained in the above, the light of a fluorescent lamp was applied to the film, and the uneven reflection on the surface was visually confirmed. Examine the contents of the confirmed part with an optical microscope, separate it from external foreign substances such as dust, and the major axis (the longest diameter connecting the end part of the particle projection image) is less than 100 μm Was counted as the number of gel-like foreign matters.

In the case of the number of checks of several hundred pieces / m ² level, the evaluation area was appropriately reduced and the result converted to 1 m ² was defined as the number of gel-like foreign matters.

Table 6 summarizes the structure and evaluation results of the optical film.

　表６の記載から分かるように、残留未反応モノマー、残留重合開始剤、及び残留連鎖移動剤の含有量を低減し、本発明に係る高分子量体生成率Ｈが本発明の範囲内にある樹脂組成物を用いて作製した光学フィルムは、薄膜化しても面荒れの発生がなく、同時にゲル状異物も大幅に低減していることが分かる。

As can be seen from the description in Table 6, the content of the residual unreacted monomer, the residual polymerization initiator, and the residual chain transfer agent is reduced, and the high molecular weight product formation rate H according to the present invention is within the scope of the present invention. It can be seen that the optical film produced using the composition does not cause surface roughness even when it is thinned, and at the same time, the gel-like foreign matters are greatly reduced.

Further, as the cellulose ester resin, the amount of crystallized matter remaining on the sieve is reduced by adjusting the solvent and its use conditions so that the value a according to the present invention is within the preferred range, and the alkali metal in the cellulose ester resin Alternatively, it can be seen that the purified cellulose ester resins B4 to B6 having a reduced group 2 element content have a great effect in reducing gel-like foreign substances.

It can also be seen that the thickness of the optical film is preferably in the range of 15 to 25 μm from the viewpoint of surface roughness.

The glossy film of the present invention is an optical film that does not cause surface roughness and has reduced gel-like foreign matter, and is suitable for polarizing plates, liquid crystal display devices, and other wide display devices.

1 Extruder 2 Filter 3 Static Mixer 4 Casting Die 5 Cooling Roller (First Cooling Roller)
6 Elastic touch roller 7 Cooling roller (second cooling roller)
8 Cooling roller (3rd cooling roller)
9 Peeling roller 11, 13, 14, 15 Conveying roller 10 Film 12 Stretching device 16 Winding device

Claims (6)

A method for producing an optical film for melt casting using a resin composition containing at least an acrylic resin and a cellulose ester resin in a mass ratio within a range of 95: 5 to 30:70, comprising: A method for producing an optical film, characterized in that the high molecular weight product formation rate H defined by the following formula is within the range of 0 to 10%.
Formula H = (a / b) × 100 (%)
Here, H is a molecular weight (Mw) on the horizontal axis and a detection sensitivity value on the vertical axis in gel permeation chromatography (GPC) measurement of the resin composition containing the acrylic resin and the cellulose ester resin. The difference in detection sensitivity value obtained by subtracting the detection sensitivity value of GPC before heating of the resin composition from the detection sensitivity value of GPC after heating the resin composition at a temperature of 260 ° C. for 1 hour is expressed as a molecular weight (Mw ) And the value obtained by dividing the positive difference area (a) of the obtained waveform by the area (b) of GPC before heating of the resin composition ((a / b) × 100 (%)) ). The positive differential area (a) is an area on the higher molecular weight side than the molecular weight value indicating the GPC detection sensitivity peak value before heating of the resin composition. The weight average molecular weight Mw of the acrylic resin is in the range of 2.0 × 10 ⁴ to 5.0 × 10 ⁵ , and the content of residual unreacted monomer in the acrylic resin is in the range of 100 to 1000 ppm. The method for producing an optical film according to claim 1. The content of the residual polymerization initiator of the acrylic resin is in the range of 10 to 500 ppm, and the content of the residual chain transfer agent is in the range of 10 to 500 ppm. The manufacturing method of the optical film of 2. It is a manufacturing method of the optical film as described in any one of Claim 1- Claim 3, Comprising: The said cellulose ester resin is manufactured by mixing a cellulose-ester solution and a poor solvent, and precipitating a cellulose ester. In this case, the content of water with respect to the solvent contained in the cellulose ester solution is in the range of 10 to 60% by mass, and the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent. And the total number of acyl groups (t) per glucose unit of the cellulose ester precipitated satisfies the following formulas (1) and (2).
Formula (1) a = s + 0.8t
Formula (2) 31 ≦ a ≦ 40
(In the formula, s is the SP value of the whole solvent after mixing the cellulose ester solution and the poor solvent, and t is the total number of acyl group carbon atoms per glucose unit of the cellulose ester. 0.8t above) Is a term relating to the contribution of the acyl group to the SP value.) The optical film according to any one of claims 1 to 4, wherein the content of an alkali metal or a Group 2 element in the cellulose ester resin is in the range of 1 to 150 ppm. Manufacturing method. The method for producing an optical film according to any one of claims 1 to 5, wherein the thickness of the optical film is within a range of 10 to 35 µm.

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