WO2011111484A1

WO2011111484A1 - Method for producing cellulose ester, cellulose ester, and cellulose ester film

Info

Publication number: WO2011111484A1
Application number: PCT/JP2011/053229
Authority: WO
Inventors: 学松岡; 笠原　健三
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-03-09
Filing date: 2011-02-16
Publication date: 2011-09-15
Also published as: JPWO2011111484A1

Abstract

Disclosed is a method for producing a cellulose ester, with which variations in properties among production lots of the cellulose ester is suppressed and a cellulose ester film with reduced film surface defects (such as oblique streaks, lateral steps, or egg unevenness) can be produced. Also disclosed are a cellulose ester produced by the method, and a cellulose ester film using the cellulose ester. The method for producing a cellulose ester comprises a milling step of milling starting material cellulose, an activation step, an esterification step, an aging step, and a post-treatment step. The milling step is a mechanochemical milling step in which starting material cellulose and a solvent are mixed and milled.

Description

Method for producing cellulose ester, cellulose ester, and cellulose ester film

The present invention relates to a cellulose ester production method, a cellulose ester, and a cellulose ester film, and suppresses variation in performance between production lots of cellulose ester and reduces the film surface failure (diagonal streaks, horizontal dan, egg unevenness, etc.). The present invention relates to a method for producing a cellulose ester capable of producing a film, a cellulose ester produced thereby, and a cellulose ester film using the cellulose ester.

Conventionally, cellulose ester has been suitably used as a raw material for a protective film of a polarizing plate used in a liquid crystal display device because of its high transparency, low birefringence, and excellent adhesion with a polarizer. In addition, it is suitably used as a raw material for optical films such as a retardation film, a field-of-view expansion film, and an antireflection film.

Cellulose esters used in the above products are generally activated (pretreatment) in which the raw cellulose coarsely pulverized in the pulverization step is activated in order to react with acyl groups, and the cellulose ester is produced under carboxylic acid and acid catalyst. An esterification step for esterifying a hydroxyl group, an aging step for converting the acyl group substituted in the esterification step to a desired acyl group substitution degree by deacylation or the like, if necessary, hydrolyzing the carboxylic acid anhydride, and a base The product is obtained by precipitating, purifying and drying the product through a neutralization step of neutralizing the acid catalyst.

Conventionally, cellulose ester films used for optical applications are generally formed into solutions, and are formed using a chlorinated solvent such as methylene chloride. Cellulose esters are greatly involved in properties such as solubility and viscosity due to changes in acyl group substitution degree distribution and polymerization degree. If an optical film is made using cellulose ester whose distribution of acyl group substitution degree or degree of polymerization is not uniformly adjusted, insoluble matter may remain and cause bright spot foreign matter, or optically fatal such as phase difference Therefore, it is important to precisely adjust the esterification process and the aging process. However, cellulose is a natural polymer, and there are large variations in the molecular weight, molecular chain, crystallinity, etc. of the raw material itself, resulting in uneven reaction in the activation process, esterification process, and aging process, and no unevenness. If the time of each process is taken long or the temperature is raised, the degree of polymerization is lowered and control is difficult. A technique for making the distribution uniform by precisely controlling the esterification step and the ripening step is disclosed (for example, see Patent Document 1), but has not yet achieved a sufficient effect.

Patent Document 2 includes a step of activating cellulose with an activating agent, a step of esterifying cellulose with an acylating agent having at least 2 carbon atoms (particularly at least 3 carbon atoms) in the presence of an acylation catalyst, And a method for producing a cellulose ester, comprising a step of saponifying and ripening the produced cellulose ester, and after the esterification step, the esterification reaction terminator is added to 0.1 mol of the acylating agent remaining in the reaction system. A technique for remarkably improving the generation of bright spot foreign matter by adding cellulose at a rate of 3 to 10 equivalents / minute to produce a cellulose ester is disclosed.

However, in the recent production of wide and thin cellulose ester films, when cellulose esters having non-uniform acyl group substitution degree distributions or cellulose esters having non-uniform polymerization degree distributions are used, film formation may occur depending on the lot of cellulose esters. However, the film surface quality (diagonal streaks, horizontal dunes, egg unevenness, etc.) is not stable, and there are new problems not described in the above patent document. It was rare.

JP 2006-117896 A JP 2007-197563 A

An object of the present invention is to provide a method for producing a cellulose ester capable of producing a cellulose ester film capable of producing a cellulose ester film with reduced film surface failures (diagonal streaks, horizontal dans, egg unevenness, etc.) by suppressing variation in performance between production lots of cellulose esters. The object is to provide a produced cellulose ester and a cellulose ester film using the cellulose ester.

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

1. In a cellulose ester production method including a raw material cellulose pulverization step, an activation step, an esterification step, an aging step, and a post-treatment step, the pulverization step mixes and pulverizes the raw material cellulose and a solvent, and a mechanochemical pulverization step The manufacturing method of the cellulose ester characterized by the above-mentioned.

2. The above-mentioned solvent is characterized in that the solvent is at least one solvent selected from carboxylic acids, alcohols, ketones, ethers and cellosolves, or a mixed solvent of at least one solvent and water. The manufacturing method of the cellulose ester as described in any one of.

3. 3. The method for producing a cellulose ester according to 1 or 2, wherein a filtration step is provided between the esterification step and the aging step.

4. The cellulose ester has an average acyl group substitution degree of 1.2 to 2.95, an acyl group total carbon number of 2.0 to 9.5, and an average weight molecular weight of 100,000 to 500,000. 3. The method for producing a cellulose ester according to 1 or 2 above.

5. A cellulose ester produced by the method for producing a cellulose ester according to any one of 1 to 4 above.

6. 6. A cellulose ester film comprising the cellulose ester as described in 5 above.

According to the present invention, there is provided a method for producing a cellulose ester capable of producing a cellulose ester film capable of producing a cellulose ester film with reduced film surface failures (diagonal stripes, horizontal dans, egg unevenness, etc.) by suppressing variation in performance between production lots of cellulose esters. The produced cellulose ester and a cellulose ester film using the cellulose ester can be provided.

It is a schematic diagram which shows the manufacture flow of the cellulose ester of this invention.

Hereinafter, modes for carrying out the present invention will be described in detail, but the present invention is not limited to these.

A conventional method for producing a cellulose ester is generally to dry-grind raw material cellulose to form a cotton, and then activate it with an acetic acid aqueous solution or hot water. However, when dry pulverization of the raw material cellulose, it is easy to form a finely pulverized cotton-like product with uneven pulverized particle size, and a uniform cellulose ester is formed by the activation process and esterification process in the next step. There was a problem that it was difficult to be done.

Furthermore, in the ripening step, it was necessary to spend a certain amount of time in order to uniformly give the desired degree of acyl group substitution, but if the time was taken to make the degree of substitution distribution uniform, the degree of polymerization would be lowered. There was a problem.

Further, according to the study of the present inventors, when the acyl group substitution degree and polymerization degree obtained in this way are non-uniform depending on the lot, a cellulose ester film is produced using the cellulose ester. It was found that breakdowns (diagonal stripes, horizontal dunes, egg unevenness, etc.) are likely to occur. This is because when the acyl group substitution degree and the degree of polymerization are non-uniform from lot to lot, the viscosity of the film-forming composition is uneven, and it is difficult to form a uniform film when cast from a die or the like. Is. In particular, defects are likely to appear in the case of film formation by the melt casting method.

As a result of intensive studies in view of the above problems, the present inventor has found that in the cellulose ester production method including a raw cellulose pulverization step, an activation step, an esterification step, an aging step, and a post-treatment step, the pulverization step is the raw cellulose This is a mechanochemical pulverization process that mixes and pulverizes with a solvent. It has been found that the problem of streaks, horizontal dunes, egg unevenness, etc.) can be solved, and the invention according to claim 1 of the present application has been achieved.

In other words, in the cellulose ester production process, by providing a mechanochemical pulverization process in which solvent and pulp are mixed and pulverized before the activation treatment, the cellulose chains can be uniformly pulverized without damaging them as much as possible. Thus, the reaction in the esterification step / ripening step can be performed smoothly. In particular, since the reaction time in the ripening step can be shortened, it has been possible to achieve both improvement in the uniformity of the reaction and prevention of a decrease in the degree of polymerization, which have been the trade-off.

Moreover, there are not a few impurities in the raw pulp. They are mixed as unacetylated products and impurities in the esterification process. In the present invention, raw material cellulose and solvent are mixed and mechanochemically pulverized to form a slurry state, and the cellulose is made into fine particles by effectively cutting the molecular force and hydrogen bonds of raw material cellulose. In addition, the mixed solution of the solvent and water enters or bonds between cellulose molecules, so that hydrogen bonding between the hydroxyl groups of cellulose can be prevented, and the pulverized cellulose itself becomes activated. In the activation step, which is the next step, it is possible to take a means to replace the activator according to the mixed solvent at the time of pulverization, so that cellulose activated by pulverization by these means can quickly undergo subsequent esterification reactions. It is performed uniformly and has the effect of reducing unacetylated components and impurities.

Furthermore, the invention according to claim 3 of the present application effectively removes impurities contained in the raw material cellulose and unacetylated components that could not be esterified by passing the esterified dope through a filter. This is a preferred embodiment for further enhancing the effects of the present invention.

The mechanochemical pulverization referred to in the present invention is defined as pulverization in which mechano = machine and chemical = chemical reaction are simultaneously performed. That is, by physically crushing a substance with a composition that is difficult to react due to strong hydrogen bonds, etc., the hydrogen bonds are broken and recombined before reacting with another substance such as acetic acid to change chemically, or alcohol etc. It is hydrogen bonding with a solvent. As a result, hydrogen bonds between celluloses can be prevented from recurring.

The present invention has been found that not only variation between lots of cellulose ester after purification but also variation in lots can be remarkably suppressed by mixing and finely pulverizing (mechanochemical pulverization) a solvent and raw material cellulose. .

Hereinafter, the present invention will be described in detail.

<Cellulose ester>
The cellulose ester of the present invention is preferably contained in a cellulose ester film for use in an optical film, and is preferably a cellulose ester having an aliphatic acyl group having 2 or more carbon atoms, and more preferably an acyl total of cellulose ester. A cellulose ester having a substitution degree of 1.0 to 2.95 and a total acyl group carbon number of 2.0 to 9.5.

The total number of acyl groups in the cellulose ester is preferably 4.0 to 9.0, more preferably 5.0 to 8.5. However, the acyl group total carbon number is the sum total of the products of the substitution degree and the carbon number of each acyl group substituted in the glucose unit of the cellulose ester.

Furthermore, the number of carbon atoms of the aliphatic acyl group is preferably 2 or more and 6 or less, 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 hydroxyl group.

The glucose unit constituting cellulose with β-1,4-glycosidic bonds has free hydroxyl groups at the 2nd, 3rd and 6th positions. The cellulose ester in the present invention is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group. The acyl group substitution degree represents the total ratio of cellulose esterified at the 2nd, 3rd and 6th positions of the repeating unit. Specifically, the degree of substitution is 1 when the hydroxyl 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 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.

Preferred cellulose esters other than cellulose triacetate have an acyl group having 2 to 4 carbon atoms as a substituent, and when the substitution degree of acetyl group is X and the substitution degree of propionyl group or butyryl group is Y, the following formula ( It is a cellulose ester including a cellulose ester that simultaneously satisfies I) and (II).

Formula (I) 1.2 ≦ X + Y ≦ 2.95
Formula (II) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used, and 0.1 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 2.8 are particularly preferable. The portion that is not substituted with an acyl group usually exists as a hydroxyl group. The method for measuring the degree of acyl group substitution can be measured according to ASTM-D817-96.

The cellulose ester of the present invention preferably has a weight average molecular weight Mw of 50,000 to 500,000, more preferably 100,000 to 300,000, still more preferably 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. Softwood pulp is preferably used. 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 90% or more (eg, 92 to 100%, preferably 95 to 100%, more preferably about 99.5 to 100%).

<Method for producing cellulose ester>
The cellulose ester production process is largely divided into a raw material cellulose crushing step, activation step, esterification step for substitution with acyl groups, aging step for promoting the elimination of acyl groups and adjusting the degree of substitution, and precipitation / washing of purified products. It is divided into the post-processing (finishing) process to dry.

FIG. 1 shows a production flow of the cellulose ester of the present invention. A filtration step can be incorporated between the esterification step and the aging step. Moreover, the neutralization process can serve as both the ripening stop and the neutralization process, and both are shown by the dotted line.

Hereinafter, each process shown in the figure will be described.

[Crushing process]
The raw cellulose pulverization step according to the present invention is a mechanochemical pulverization step in which raw cellulose and a solvent are mixed and pulverized.

The solvent is preferably at least one solvent selected from carboxylic acids, alcohols, ketones, ethers and cellosolves, or a mixed solvent of the solvent and water.

Of these, carboxylic acids such as acetic acid and propionic acid are preferred, and carboxylic acid is particularly preferred in view of the subsequent activation treatment.

The said solvent is mixed with the solution of the range of 50 mass parts to 1000 mass parts with respect to 100 mass parts of raw material cellulose, and it grind | pulverizes. A more preferable range of the solvent amount is 75 parts by mass to 700 parts by mass, and a range of 95 parts by mass to 500 parts by mass is more preferable.

The raw cellulose may be crushed by adding a dry coarse pulverization step to a size that can be charged into a fine pulverization apparatus as a previous step. It is also preferable to perform pre-stirring at a low speed after adding the solvent in order to promote uniform mixing of the raw material cellulose and the solvent.

The apparatus for pulverizing the raw material cellulose is not particularly limited as long as it is an apparatus that can be finely pulverized in a wet manner, but a ball mill system (planetary ball mill, etc.), a wet pulverizer (ball-in-liquid collision type, slurry type, etc.), and a grinding type. Pulverizers (stone mortar type, screen type, etc.), collision type pulverizers (wet jet mill, etc.), screw type pulverizers, etc. are preferably used, and these may be used in combination.

In the present invention, the raw material cellulose at the time of pulverization is easily amorphized because it is finely pulverized in a liquid or slurry state where the raw material is wet, which is advantageous in the subsequent cellulose ester production process.

Since the temperature may increase during pulverization, the pulverizer is preferably provided with a cooling function, and the temperature setting is preferably controlled at 60 ° C. or lower. The temperature is preferably 10 to 50 ° C, more preferably 20 to 45 ° C.

The pulverization time can be appropriately determined, but is preferably 15 minutes to 45 minutes, and more preferably 20 minutes to 30 minutes.

The raw cellulose is refined by mechanochemical pulverization according to the present invention, and the average particle size of the raw cellulose after pulverization is 100 μm or less, but considering the addition of filtration before the aging step, the reaction in each step is performed in a short time. And from the viewpoint of preventing clogging of the filter medium, it is preferably 10 μm or more and 80 μm or less. The particle size of the raw material cellulose can be measured by using a microscope or the like.

[Activation process]
In the activation step, cellulose is treated with an activator to activate the cellulose. In the present invention, 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, about 25 to 150 parts by weight, preferably 30 to 125 parts by weight, and more preferably 50 to 100 parts by weight (for example, 70 to 100 parts by weight) with respect to 100 parts by weight of cellulose. It may be.

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 a range of 0 ° C. to 100 ° C. In order to perform the activation treatment without applying industrial load, it is usually 10 ° C. to 40 ° C., preferably about 15 ° C. to 35 ° C. It is. The activation treatment time can be selected in the range of 0.1 to 72 hours, and is usually about 0.1 to 3 hours, preferably about 0.2 to 2 hours.

In the case of the present invention, when the solvent used for pulverizing the raw material cellulose is carboxylic acid, the activation process proceeds in the fine pulverization stage, so the standing time is short, and it is immediately put into the esterification reaction vessel. be able to.

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]
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. Turn into. As the acid catalyst, Lewis acid or strong acid can be used, but sulfuric acid is generally used.

Usually, acid anhydrides [for example, acid anhydrides of carboxylic acids having 2 or more carbon atoms (carboxylic anhydrides)], for example, C2-6 alkanoic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, etc. Things can be used. A carboxylic acid having an acyl group having at least 2 carbon atoms (for example, at least a C2-6 carboxylic 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 acid catalyst (especially sulfuric acid) used in the esterification step is, for example, in the range of 3 to 20 parts by weight, preferably 5 to 18 parts by weight, more preferably about 7 to 15 parts by weight with respect to 100 parts by weight of cellulose. Usually, it is about 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 (acid anhydride) may be used, and for example, selected from acid anhydrides corresponding to C2-6 carboxylic acid A plurality of acid anhydrides 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 C2-4 alkanecarboxylic anhydrides, for example, at least one selected from C2-4 carboxylic anhydrides (such as acetic anhydride or propionic anhydride), 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, about 1.1 to 4 equivalents, preferably 1.1 to 2 equivalents, more preferably about 1.3 to 1.8 equivalents relative to the hydroxyl group of cellulose. is there.

Only in the case of acetylation, when obtaining a cellulose ester having a small degree of acetyl substitution, the amount of acetic anhydride used in the esterification step is 0.5 equivalent or less (about 0 to 0.3 equivalent) relative to the hydroxyl group of cellulose. ), Or less than 0.2 equivalent (0.01-0.1 equivalent), and may not be used substantially.

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 about 50 to 700 parts by weight, preferably 150 to 600 parts by weight, and more preferably about 200 to 550 parts by weight with respect to 100 parts by weight of cellulose.

The esterification reaction can be performed at a temperature of about 0 to 50 ° C., preferably 5 to 45 ° C., more preferably about 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 about 45 to 100 minutes from the start of the esterification reaction. The esterification time at 10 to 50 ° C. is 10 minutes or more and 20 to 90 minutes, preferably 30 to 80 minutes, 40 minutes 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 at least water is often included. The quenching agent that promotes hydrolysis may be composed of at least one selected from water, an esterification solvent, an alcohol, and a neutralizing agent. More specifically, examples of the quenching agent include water alone, a mixture of water and carboxylic acid, a mixture of water and alcohol, a mixture of water and neutralizing agent, water, an organic carboxylic acid and alcohol, and the like. Examples thereof include a mixture with a hydrating agent.

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 the alcohol include straight chain 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 esterification solvent or alcohol with respect to 100 parts by mass of water, usually 25 to 120 parts by mass, preferably 50 parts by mass. ~ 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 process of filtering the reaction solution once may be introduced.

This reaction stopping step can be omitted if necessary.

[Filtering process]
In this invention, it is preferable to provide a filtration process between the said esterification process and the aging process mentioned later.

The solution after the conventional cellulose esterification reaction was clogged immediately after filtration because of its high viscosity, but clogging is less likely to occur by grinding in the solvent of the present invention. Thus, a filtration step can be provided before the aging step.

The solution after completion of the esterification reaction contains unacetylated, low-acetylated components and impurities that did not react with the raw material cellulose. Time is further shortened, and specific cleavage of molecular chains and substituents occurring in the reaction solution is difficult 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.

Therefore, the filter medium used in the cellulose ester slurry after the esterification step of the present invention preferably has an absolute filtration accuracy of 10 μm or less, more preferably in the range of 1 to 8 μm, and still more preferably in the range of 3 to 5 μm.

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 the present invention, it is preferable to use a pressure filter equipped with the 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 20 ° C. to 90 ° C., preferably 25 ° C. to 80 ° C., more preferably 30 ° C. to 70 ° C. The ripening reaction may be performed in a nitrogen atmosphere or in an air atmosphere You may go on.

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, 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-treatment process (precipitation, filtration, washing, drying)]
After neutralizing the acid catalyst in the neutralization step, the product is precipitated by precipitation.

In order to cause precipitation, a mixed solution of water and carboxylic acid is preferably used. These precipitation solvents are not limited, and ketones, alcohols, ethers, esters and the like alone or water mixed solvents may be used.

The process of filtering and washing the precipitated product is repeated until the free acid concentration is 500 ppm or less, preferably 300 ppm or less, more preferably 150 ppm or less.

Then, it is dried with dry air to obtain the desired cellulose ester.

[Others]
Industrially, cellulose ester is synthesized using sulfuric acid as a catalyst, but this sulfuric acid is not completely removed, and the residual sulfuric acid causes various decomposition reactions during melt film formation, and the resulting cellulose ester film In order to affect the quality, the residual sulfuric acid content in the cellulose ester used in the present invention is preferably in the range of 0.1 to 40 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 40 ppm, the deposit on the die lip during heat melting increases, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable. A smaller amount is preferable, but if it is less than 0.1, it is not preferable because the burden of the washing step of the cellulose resin becomes too large. This is not well understood, although an increase in the number of washings may affect the resin. Furthermore, the range of 0.1 to 30 ppm is preferable. The residual sulfuric acid content can be similarly measured by ASTM-D817-96.

By washing the synthesized cellulose ester more sufficiently than when used in the solution casting method, the residual sulfuric acid content can be within the above range, and when producing a film by the melt casting method. In addition, adhesion to the lip portion is reduced, and a film having excellent flatness can be obtained.

<Method for producing cellulose ester film>
A cellulose ester film for use in an optical film is produced using the cellulose ester obtained by the above operation.

The method for producing a cellulose ester film is roughly classified into a solution casting film forming method and a melt casting film forming method, and the effects of the present invention can be achieved by using either method.

[Melt casting method]
In the method for producing a cellulose ester film comprising the cellulose ester of the present invention, at least a polymer forming the film, particulate matter and additives are mixed and melted, the melt is filtered by a filtration device, and then extruded from a normal die. Cast on a cooling roll.

Hereinafter, the whole manufacturing method will be described.

<Melted pellet manufacturing process>
The mixture of the polymer, particulate matter, plasticizer and other additives that form the film used for melt extrusion is preferably kneaded in advance and pelletized.

Pelletization may be performed by a known method. For example, a polymer, a plasticizer, and other additives that form a film are supplied to an extruder with a feeder, and are kneaded using a single-screw or twin-screw extruder. Extruded into a shape, water-cooled or air-cooled and cut.

Pre-drying of raw materials before extrusion is important for preventing decomposition of the raw materials. In particular, since the polymer forming the optical film is likely to absorb moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer so that the moisture content is 300 ppm or less, further 100 ppm or less.

Additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly.

Mixing of the antioxidants may be performed by mixing solids, and if necessary, the antioxidant may be dissolved in a solvent and impregnated with a polymer forming an optical film, or may be mixed or sprayed. May be mixed.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

The extruder is preferably processed at as low a temperature as possible so as to be able to be pelletized so that the shear force is suppressed and the resin does not deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. It is also possible to feed the raw material powder directly to the extruder with a feeder and form a film as it is without pelletization.

<Process for extruding molten mixture from die to cooling roll>
The produced pellets are extruded using a single-screw or twin-screw type extruder, the melting temperature Tm is about 200 to 350 ° C., filtered by the filtration device of the present invention to remove foreign matters, and then formed into a film from the T die. And solidified on a cooling roll and cast while pressing with an elastic touch roll.

When introducing into the extruder from the supply hopper, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere. Tm is the temperature of the die exit portion of the extruder.

∙ If foreign matter such as scratches or plasticizer aggregates adheres to the die, streaky defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

The inner surface that comes into contact with the molten resin, such as an extruder or a die, is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material with low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

There is no particular limitation on the cooling roll, but it is a roll having a structure in which a heat medium or a cooling medium whose temperature can be controlled flows with a high-rigidity metal roll, the size of which is not limited, but a melt-extruded film The diameter of the cooling roll is usually about 100 mm to 1 m.

The surface material of the cooling roll includes carbon steel, stainless steel, aluminum, titanium and the like. Further, in order to increase the hardness of the surface or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying.

The surface roughness of the cooling roll surface is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable that the surface processed is further polished to have the above-described surface roughness.

Examples of the elastic touch roll of the present invention include JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97-028950, JP-A-11-235747, JP-A-11-235747. As described in JP 2002-36332 A, JP 2005-172940 A, and JP 2005-280217 A, a thin-film metal sleeve-covered silicon rubber roll can be used.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

The film obtained as described above is preferably stretched by a stretching operation after passing through a step in contact with a cooling roll.

As the stretching method, a known roll stretching machine or tenter can be preferably used. The stretching temperature is usually preferably in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

Before winding, the end may be slit and cut to the product width, and knurled (embossed) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused.

[Solution casting film forming method]
<Organic solvent>
An organic solvent useful for forming a dope when a cellulose ester film is produced by a solution casting method can be used without limitation as long as it dissolves cellulose ester and other additives simultaneously.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, thermoplastic acrylic resins and cellulose ester resins in non-chlorine organic solvent systems There is also a role of promoting dissolution of the.

In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least 15 kinds of thermoplastic acrylic resin, cellulose ester resin, and acrylic particles are used. A dope composition in which 45% by mass is dissolved is preferable.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

<Solution casting method>
In the production of a cellulose ester film by a solution casting method, a step of preparing a dope by dissolving a cellulose ester and an additive in a solvent, a step of casting the dope on a belt-shaped or drum-shaped metal support, and casting. It is performed by a step of drying the dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

The concentration of the cellulose ester and the additive in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of the cellulose ester is too high, the load during filtration increases. Thus, the filtration accuracy is deteriorated. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

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

The cast width can be 1 ~ 4m. The surface temperature of the metal support in the casting step is set to −50 ° C. to below the temperature at which the solvent boils and does not foam. A higher temperature is preferred because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate.

A preferable support temperature is appropriately determined at 0 to 100 ° C., and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

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

When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. .

Particularly, it is preferable to efficiently dry by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

In order for the cellulose ester film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Particularly preferred is 20 to 30% by mass or 70 to 120% by mass.

The amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Particularly preferred is 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged at the top and bottom are alternately passed through the web for drying) or a tenter method for drying while transporting the web is employed.

<Additives used for cellulose ester film>
In order to improve the fluidity and flexibility of the composition, it is also preferable to use a plasticizer in combination with the cellulose ester film. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester. It is selected from plasticizers, acrylic plasticizers, carbohydrate ester plasticizers and the like. Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

The polyhydric alcohol ester plasticizer is a plasticizer composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. A divalent to 20-valent aliphatic polyhydric alcohol ester is preferred.

The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula (a) Ra- (OH) n
(However, Ra represents an n-valent organic group, n represents a positive integer of 2 or more, and an OH group represents an alcoholic and / or phenolic hydroxyl group.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

Preferred examples of the monocarboxylic acid include the following, but the present invention is not limited to this.

As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

Examples of preferable alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as alkyl group, methoxy group or ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

The carboxylic acid used in the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

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

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

Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabtylate, saccharose octaacetate, saccharose octabenzoate and the like. Among these, saccharose octaacetate, saccharose Octabenzoate is more preferred, and sucrose octabenzoate is particularly preferred. For example, monopet SB: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., monopet SOA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. can be cited as commercially available products.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the cellulose ester film. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

The cellulose ester film preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones. Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding. be able to.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

Furthermore, various antioxidants can be added to the cellulose ester film in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

For the cellulose ester film, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

In the cellulose ester film, a matting agent can be added in order to impart slipperiness, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

The shape of the matting agent is preferably a spherical shape, rod shape, needle shape, layer shape, flat plate shape or the like. Examples of the matting agent include oxidation of metals such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Inorganic fine particles such as materials, phosphates, silicates, carbonates and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

<Thermoplastic acrylic resin>
In the cellulose ester film of the present invention, a thermoplastic acrylic resin may be mixed with the cellulose ester as a resin.

The acrylic resin used in the present invention preferably exhibits negative birefringence with respect to the stretching direction of the film, and the structure is not particularly limited, but is obtained by polymerizing an ethylenically unsaturated monomer. It is preferable that a polymer having a weight average molecular weight of 500 or more and 1000000 or less is appropriately selected. The proper molecular weight range of the acrylic polymer is as described above, but when it is contained in an amount of 30% by mass or more, the weight average molecular weight is preferably 80,000 to 1,000,000 from the viewpoint of compatibility with the cellulose ester.

The mass ratio of the thermoplastic acrylic resin and the cellulose ester is preferably thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50. More preferably, it is 90:10 to 60:40.

Thermoplastic acrylic resin includes methacrylic resin. The thermoplastic acrylic resin is not particularly limited, but is preferably composed of 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith. Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Examples thereof include maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like, and these can be used alone or in combination of two or more monomers.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used. Further, the weight average molecular weight (Mw) is preferably 80,000 to 500,000, and more preferably 110,000 to 500,000. The weight average molecular weight of the thermoplastic acrylic resin can be measured by the gel permeation chromatography described above, including the measurement conditions. There is no restriction | limiting in particular as a manufacturing method of a thermoplastic acrylic resin, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. The polymerization temperature may be 30 to 100 ° C. for suspension or emulsion polymerization, and 80 to 160 ° C. for bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent. Commercial products can also be used. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more thermoplastic acrylic resins can be used in combination. As the thermoplastic acrylic resin, a graft copolymer obtained by grafting a (meth) acrylic resin to a copolymer of (meth) acrylic rubber and an aromatic vinyl compound described in JP-A-2009-84574 is used. May be. In the graft copolymer, a copolymer of (meth) acrylic rubber and an aromatic vinyl compound forms a core, and the (meth) acrylic resin forms a shell around the copolymer. -A shell-type graft copolymer is preferred.

<Physical properties of cellulose ester film>
The cellulose ester film according to the present invention is preferably a “film that does not cause ductile fracture”. Here, the ductile fracture is a fracture caused by applying a stress larger than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or drawing of the material until the final fracture. The fracture surface is characterized by numerous indentations called dimples.

「Whether or not it is a“ film that does not cause ductile fracture ”shall be evaluated based on the fact that no breakage such as breakage is observed even when a large stress is applied to bend the film in two.

The size of liquid crystal display devices is increasing, and the brightness of backlight light sources is increasing. In addition, the use of digital signage and other outdoor applications demands higher brightness. The cellulose ester film of the present invention is required to be able to withstand use in a high temperature environment, and if the tension softening point is 105 ° C. to 145 ° C., it can be determined that it exhibits sufficient heat resistance, In particular, it is preferable to control at 110 ° C. to 130 ° C.

As a specific method for measuring the tension softening point, for example, using a Tensilon tester (produced by ORIENTEC, RTC-1225A), the cellulose ester film is cut out at 120 mm (length) × 10 mm (width) with a tension of 10 N. While pulling, the temperature can be raised at a rate of 30 ° C./min. The temperature at the time when the temperature reaches 9 N is measured three times, and the average value can be obtained.

Also, from the viewpoint of heat resistance, the cellulose ester film preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a heating rate of 20 ° C./min. Point glass transition temperature (Tmg).

In addition, when a cellulose ester film is used as a protective film for a polarizing plate of a liquid crystal display device, unevenness or a change in retardation value occurs due to a dimensional change due to moisture absorption, causing problems such as a decrease in contrast and uneven color. . In particular, the above problem becomes significant when the polarizing plate protective film is used in a liquid crystal display device used outdoors. For this reason, the dimensional change rate (%) is preferably less than 0.5%, and more preferably less than 0.3%.

Further, the cellulose ester film preferably has a defect of 5 μm or more in diameter in the film plane of 1 piece / 10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

Here, the diameter of the defect indicates the diameter when the defect is circular, and when it is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. If the defect is a change in surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation.

In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is more than 1/10 cm square, for example, when a tension is applied to the film during processing in a later process, the film may be broken with the defect as a starting point and productivity may be reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

Also, even when visual confirmation is not possible, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in defects (coating defects). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

Further, the cellulose ester film preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more, as measured in accordance with JIS-K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The thickness of the cellulose ester film is preferably 20 μm or more. More preferably, it is 30 μm or more.

The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying and the like. The thickness of the film can be appropriately selected depending on the application.

The cellulose ester film preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the thermoplastic acrylic resin.

<Reply material suitability>
In the process of making a cellulose ester film from a conventional cellulose ester, a step of appropriately slitting both end portions of the film is provided, and unnecessary end films that appear at that time are reused. This is generally called return material.

In the solution casting film formation, the slit film is dissolved again in the solvent at a relatively low temperature, so that the properties equivalent to those of the new raw material can be maintained, and there is no particular problem in the properties even when the optical film is formed. Even when the cellulose ester film using the cellulose ester of the present invention was used as a recycled material in solution casting film formation, there was no problem as in the prior art.

On the other hand, it is difficult to make full use of the recycled material in the case of a melt cast film as in the case of a solution cast film. That is, in the melt casting film forming process, since high-temperature heat is applied to the cellulose ester at the time of melting, the cellulose ester molecules have been deteriorated and decomposed, and when reused, the decomposition and deterioration further proceed. Components that adversely affect the film for optical use such as a deteriorated product, a gel foreign material, and a bright spot foreign material are likely to be generated, and the recycled material has not been actually used.

However, since the cellulose ester of the present invention is extremely uniform and has few impurities, even if the film obtained by melt casting is used again as a recycled material, there is little occurrence of deterioration and coloring, and optical use It turns out that the quality of the film has been fully achieved.

The use ratio of the recycled material is preferably 0 to 70% by mass, more preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass with respect to the solid content of the main unused raw material.

When the recycled material is used, the additives contained in the cellulose ester film such as plasticizers, ultraviolet absorbers, and fine particles are reduced according to the amount used, and the final cellulose ester film composition becomes the design value. It is preferable to make such adjustments.

<Functional layer>
The cellulose ester film of the present invention can be provided with functional layers such as an antistatic layer, a backcoat layer, an antireflection layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer.

<Hard coat layer>
The hard coat layer used in the present invention contains an actinic radiation curable resin, and is a layer mainly composed of a resin that cures through a crosslinking reaction by irradiation with an actinic ray (also referred to as an active energy ray) such as an ultraviolet ray or an electron beam. Preferably there is.

As the actinic radiation curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used, and an actinic radiation curable resin layer is formed by curing by irradiation with actinic radiation such as ultraviolet rays or electron beams. The

Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but the resin that is cured by ultraviolet irradiation is excellent in mechanical film strength (abrasion resistance, pencil hardness). preferable.

As the ultraviolet curable resin, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. Of these, ultraviolet curable acrylate resins are preferred.

In addition, it is preferable that the hard coat layer contains a photopolymerization initiator to accelerate the curing of the actinic radiation curable resin. The amount of the photopolymerization initiator is preferably contained in a mass ratio of photopolymerization initiator: active ray curable resin = 20: 100 to 0.01: 100.

Specific examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto.

The hard coat layer preferably contains fine particles of an inorganic compound or an organic compound.

As inorganic fine particles, silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silicic acid Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

As organic particles, polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin powder, A polyolefin resin powder, a polyester resin powder, a polyamide resin powder, a polyimide resin powder, a polyfluoroethylene resin powder, or the like can be added.

The average particle diameter of these fine particle powders is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.01 to 1.0 μm. Moreover, you may contain 2 or more types of microparticles | fine-particles from which a particle size differs. The average particle diameter of the fine particles can be measured by, for example, a laser diffraction particle size distribution measuring device.

The ratio of the ultraviolet curable resin composition and the fine particles is desirably 10 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the resin composition.

These hard coat layers are coated using a known method such as a gravure coater, dip coater, reverse coater, wire bar coater, die coater, ink jet method, and the like. And can be formed by UV curing.

The dry film thickness of the hard coat layer is an average film thickness of 0.1 to 30 μm, preferably 1 to 20 μm, particularly preferably 6 to 15 μm.

As a light source for UV curing treatment, any light source that generates ultraviolet rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 200 mJ / cm ² .

<Back coat layer>
In the cellulose ester film of the present invention, a back coat layer may be provided on the surface opposite to the side on which the hard coat layer is provided to prevent curling and sticking.

As particles added to the backcoat layer, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, tin oxide, and oxide. Mention may be made of indium, zinc oxide, ITO, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate.

The particles contained in the backcoat layer are preferably 0.1 to 50% by mass with respect to the binder. When the back coat layer is provided, the increase in haze is preferably 1.5% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less.

The binder is preferably a cellulose ester resin such as diacetylcellulose.

<Antireflection layer>
The cellulose ester film of the present invention can be used as an antireflection film having an external light antireflection function by coating an antireflection layer on the hard coat layer.

The antireflection layer is preferably laminated in consideration of the refractive index, the film thickness, the number of layers, the layer order, and the like so that the reflectance is reduced by optical interference. The antireflection layer is preferably composed of a low refractive index layer having a refractive index lower than that of the support, or a combination of a high refractive index layer having a refractive index higher than that of the support and a low refractive index layer. Particularly preferably, it is an antireflection layer composed of three or more refractive index layers, and three layers having different refractive indexes from the support side are divided into medium refractive index layers (high refractive index layers having a higher refractive index than the support). Are preferably laminated in the order of a layer having a lower refractive index) / a high refractive index layer / a low refractive index layer. Alternatively, an antireflection layer having a layer structure of four or more layers in which two or more high refractive index layers and two or more low refractive index layers are alternately laminated is also preferably used.

As the layer structure of the antireflection film, the following structure can be considered, but it is not limited to this.

Cellulose ester film / hard coat layer / low refractive index layer Cellulose ester film / hard coat layer / medium refractive index layer / low refractive index layer Cellulose ester film / hard coat layer / medium refractive index layer / high refractive index layer / low refractive index Layer Cellulose ester film / Hard coat layer / High refractive index layer (conductive layer) / Low refractive index layer Cellulose ester film / Hard coat layer / Anti-glare layer / Low refractive index layer Low refractive index essential for antireflection film The refractive index layer preferably contains silica-based fine particles, and its refractive index is lower than the refractive index of the cellulose film as the support, and is in the range of 1.30 to 1.45 when measured at 23 ° C. and wavelength of 550 nm. It is preferable.

The film thickness of the low refractive index layer is preferably 5 nm to 0.5 μm, more preferably 10 nm to 0.3 μm, and most preferably 30 nm to 0.2 μm.

The composition for forming a low refractive index layer preferably contains at least one kind of particles having an outer shell layer and porous or hollow inside as silica-based fine particles. In particular, the particles having the outer shell layer and having a porous or hollow interior are preferably hollow silica-based fine particles.

Note that the composition for forming a low refractive index layer may contain an organosilicon compound represented by the following general formula (OSi-1), a hydrolyzate thereof, or a polycondensate thereof.

General formula (OSi-1): Si (OR) ₄
In the organosilicon compound represented by the above general formula, R represents an alkyl group having 1 to 4 carbon atoms. Specifically, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and the like are preferably used.

In addition, a solvent, and if necessary, a silane coupling agent, a curing agent, a surfactant and the like may be added.

<Polarizing plate>
A polarizing plate using the cellulose ester film of the present invention will be described. The polarizing plate can be produced by a general method. The back side of the cellulose ester film of the present invention is subjected to alkali saponification treatment, and a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing film prepared by immersing and stretching the treated cellulose ester film in an iodine solution. It is preferable to bond them together.

The cellulose ester film may be used on the other surface, or another polarizing plate protective film may be used. For example, a non-oriented film having retardation Ro of 590 nm at 0 to 5 nm and Rt of −20 to +20 nm described in JP-A No. 2003-12859 can be mentioned as an example.

In addition, an optical compensation film (retardation film) having a retardation of in-plane retardation Ro of 590 nm, 20 to 70 nm, and Rt of 70 to 400 nm may be used to obtain a polarizing plate capable of widening the viewing angle. it can. These can be produced, for example, by the method of JP-A-2002-71957. Alternatively, it is preferable to use an optical compensation film having an optical anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

Also, commercially available polarizing plate protective films preferably used include KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-2, KC4FR-2, KC4FR-2, KC8FR-2 KC4UE (Konica Minolta Opto Co., Ltd.) etc. are mentioned.

The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this.

As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. A polarizing film having a thickness of 5 to 30 μm, preferably 8 to 15 μm is preferably used.

A polarizing plate is formed by laminating one side of the cellulose ester film of the present invention on the surface of the polarizing film. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

<Liquid crystal display device>
By incorporating a polarizing plate produced using the cellulose ester film of the present invention into a display device, various image display devices with excellent visibility can be produced.

The cellulose ester film of the present invention is incorporated in a polarizing plate and is a reflective type, transmissive type, transflective liquid crystal display device or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type. It is preferably used in liquid crystal display devices of various driving systems such as OCB type.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Manufacture of cellulose ester>
<Production Example 1>
100 parts by mass of raw material pulp (α cellulose 93% or more) and 100 parts by mass of glacial acetic acid were put into a mixer and stirred to form a slurry, and then put into a stone mortar pulverizer and ground at 40 ° C. for 30 minutes. The average pulverized particle size of the pulverized raw material pulp was 63 μm by microscopic observation.

Next, 50 parts by mass of acetic acid was added to the pulverized raw material pulp, and activation treatment was performed for 1 hour.

The acetic acid-containing pulp is put into a reactor, and 250 parts by mass of propionic anhydride, 400 parts by mass of propionic anhydride, and 9 parts by mass of sulfuric acid are sequentially added, and the temperature is gradually raised from room temperature to 40 ° C. and kept at 40 ° C. The mixture was kept warm for 1 hour to allow the esterification reaction to proceed.

Next, after neutralizing by adding 250 parts of 30% acetic acid aqueous solution in the primary neutralization step, 150 parts by mass of 80% by mass acetic acid aqueous solution was put in order to hydrolyze the remaining carboxylic anhydrides in the aging step, and 60 ° C. And allowed to stir for 1 hour.

Then, in order to stop the reaction, 15 parts by mass of a 30% by mass aqueous magnesium acetate solution was added to neutralize the sulfuric acid.

The cellulose ester precipitated in the precipitation process was filtered off, washed 5 times with warm water at 50 ° C., and the remaining acetic acid aqueous solution was eluted, followed by drying at 70 ° C. for 3 hours, acetyl substitution degree 0.61, propionyl substitution A cellulose ester of Production Example 1 which is a cellulose acetate propionate having a degree of 2.07 and a total degree of substitution of 2.68 was obtained. The weight average molecular weight (Mw) was 200,000 as a result of measurement using the following measurement method.

<Production Example 2 to Production Example 20>
Cellulose according to Production Examples 2 to 20 was changed in the same manner as in Production Example 1 by changing the conditions of the pulverization step, activation step, esterification step, filtration step, and aging step as described in Tables 1 to 9. Esters were made. Table 6, Solution A of Production Example 15: EG represents ethylene glycol.

The following grinder was used.

a: Stone mill type grinding mill (Massko Sangyo Co., Ltd. Microcoder MKZA10-15J (Grinder type: MKM))
b: Planetary ball mill crusher (Planet750F manufactured by Nagao System)
c: Wet grinding machine (Ashizawa Finetech Co., Ltd. Star Mill Nano Getter)
d: Dry jet mill (Sunrex Industry Co., Ltd. Nano Grounding Mill NJ300)
e: Cutting mill (Lecce Cutting Mill SM 2000)
f: No pulverizer Further, in Production Examples 10 to 12, a filtration step was provided between the esterification step and the aging step, and filtration was performed using a pressure filter equipped with a polypropylene filter medium having an opening of 5 μm.

<Preparation of cellulose ester film 1>
Subsequently, using the cellulose ester obtained in Production Example 1, a cellulose ester film 1 was produced according to the following melt casting method.

<Melt casting method>
A cellulose ester film was prepared by the melt casting method with the following composition.

<Cellulose ester film composition>
Production Example 1 Cellulose ester 94 parts by mass Plasticizer: Glycerin tribenzoate 5 parts by mass Irganox 1010 (manufactured by BASF Japan Ltd.)
0.5 parts by mass Irgafos P-EPG (manufactured by BASF Japan Ltd.)
0.3 parts by mass HP-136 (manufactured by BASF Japan Ltd.) 0.2 parts by mass The cellulose ester was dried under reduced pressure at 70 ° C. for 3 hours and cooled to room temperature, and then each additive was mixed.

The above mixture was formed into a film by a manufacturing apparatus using an elastic touch roll. In a nitrogen atmosphere, it was melted at 240 ° C., extruded from the casting die onto the first cooling roll, and molded by pressing the film between the first cooling roll and the touch roll. Further, silica particles (manufactured by Nippon Aerosil Co., Ltd.) were added as a slip agent from the hopper opening in the middle of the extruder so as to be 0.1 part by mass.

The heat bolt was adjusted so that the gap width of the casting die was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations. As a touch roll, 80 degreeC water was poured as cooling water in the inside.

The circumference of the first cooling roller from the position P1 where the resin extruded from the casting die contacts the first cooling roll to the position P2 at the upstream end in the first cooling roll rotation direction of the nip between the first cooling roll and the touch roll. The length L along the surface was set to 20 mm. Thereafter, the touch roll was separated from the first cooling roll, and the temperature T of the melted part immediately before being sandwiched in the nip between the first cooling roll and the touch roll was measured. The temperature T of the melted portion immediately before being sandwiched between the first cooling roll and the touch roll is 1 mm upstream from the nip upstream end P2, and a thermometer (HA-200E manufactured by Anritsu Keiki Co., Ltd.) It was measured by. As a result of the measurement, the temperature T was 141 ° C. The linear pressure of the touch roll against the first cooling roll was 14.7 N / cm. Furthermore, after introducing into a tenter and stretching 1.3 times at 160 ° C in the width direction, cooling to 30 ° C while relaxing 3% in the width direction, then releasing from the clip, cutting off the clip gripping part, Was subjected to a knurling process having a width of 20 mm and a height of 25 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%. In addition, the film thickness was 40 micrometers, the winding length was 4000 m, and the cellulose-ester film 1 of refractive index 1.49 was produced.

<Production of cellulose ester films 2 to 20>
Similarly to the production of the cellulose ester film 1, cellulose ester films 2 to 20 were produced using the cellulose esters produced in Production Examples 2 to 20.

The melt casting temperature when the cellulose esters of Production Examples 3 to 5 were used was adjusted to 260 ° C.

<Evaluation>
(Yield of cellulose ester)
The ratio of the mass of the produced cellulose ester to the mass of the input cellulose was shown as a percentage (%).

(Acyl group substitution degree of cellulose ester)
The acyl group substitution degree was measured in accordance with ASTM-D817-96.

The abbreviations in the table are as follows.

Pr: propionyl group, AC: acetyl group, Bu: butyrate group, total: total acyl group (average molecular weight)
The average molecular weight and molecular weight distribution of the cellulose ester were measured using high performance liquid chromatography, and the weight average molecular weight (Mw) and molecular weight distribution were calculated.

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.

<Dispersion of cellulose ester (vinegar cotton)>
1. 1. Variation in molecular weight distribution: standard deviation of 1/10 width of molecular weight distribution of 10 samples of different production lots. Variation of acyl group substitution degree: standard deviation of 1/10 width of acyl group substitution degree distribution of vinegar cotton of 10 samples of different production lots <Film surface failure of cellulose ester film>
The film surface failure was visually evaluated on the following evaluation scale.

5: No film surface failure (diagonal streaks, horizontal dan, egg unevenness, etc.) 4: Slightly slanted lines are not noticeable 3: Diagonal lines are slightly conspicuous, horizontal dans are slightly conspicuous 2: Diagonal lines are clearly conspicuous, Horizontal lines are also recognized 1: Diagonal streaks, horizontal dunes, and egg unevenness 0: Diagonal streaks, horizontal dunes, and egg unevenness are very conspicuous In addition, the variation between lots of film surface failures was evaluated on the following scale.

◎: There is no variation in film surface failure among lots. ○: The cellulose ester of different production lots has a probability of 10%, and the level of film surface failure is shifted by 1. △: The cellulose ester of different production lots has a probability of 20%. The level of surface failure shifts by 1 △: The cellulose ester of different production lots has a probability of 40%, and the level of film surface failure shifts 1 to 2 △: The cellulose ester of different production lots has a probability of 60% of film surface failure The level is not stable. X: The cellulose ester in different production lots has a probability of 80% and the film surface failure level is not stable. A list of the production conditions of the cellulose ester and the above evaluation results are shown in Tables 1 to 9 below.

The cellulose esters of Production Examples 1 to 16 produced by the method for producing cellulose esters of the present invention have small variations in vinegared cotton, and film surface failure when film is formed (oblique lines, horizontal dunes, egg unevenness, etc.) It is clear that this is superior.

In addition, it can be seen that the cellulose esters of Production Examples 10 to 12 in which a filtration step is added between the esterification step and the aging step are more excellent in film surface failure when a film is formed.

Example 2
The cellulose ester film 1 using the cellulose ester produced in Production Example 1 of Example 1 was chipped as a return material, and a cellulose ester film 21 was produced according to the following formulation.

<Cellulose ester film composition>
Production Example 1 Cellulose ester 54 parts by mass Returning material cellulose ester film 1 chip 40 parts by mass Plasticizer: Glycerin tribenzoate 5 parts by mass Irganox 1010 (manufactured by BASF Japan Ltd.)
0.5 parts by mass Irgafos P-EPG (manufactured by BASF Japan Ltd.)
0.3 parts by mass HP-136 (manufactured by BASF Japan Ltd.) 0.2 parts by mass The cellulose ester was dried under reduced pressure at 70 ° C. for 3 hours and cooled to room temperature, and then each additive was mixed.

Using the above cellulose ester film composition, a cellulose ester film 21 was produced by the melt casting method in the same manner as in Example 1.

Similarly, cellulose ester films 2 to 20 using the cellulose ester produced in Production Example 2 to Production Example 20 of Example 1 were used as recycled materials, and cellulose ester films 22 to 41 were produced by a melt casting method. .

<Evaluation>
<Number of deteriorated foreign matters (pieces / m ² )>
Since the returned material component has a heat history, when it is heated again, there may be a slight foreign matter colored brown. These deteriorated foreign substances were evaluated as follows.

1 m ² minutes were cut out from the winding of the molten film obtained by the melt casting film formation, the light of a green lamp was applied to the film, and the surface unevenness was visually checked. The contents of the checked parts were examined with an optical microscope, and the colored components were separated from external foreign matters such as dust, and the colored components were determined as the number of deteriorated foreign matters.

As an optical film, it is preferable that it is 15 pieces / m < ² > or less, More preferably, it is less than 10 pieces / m < ² >.

<Coloring of film: Yellow index>
The yellow index (yellowness) is obtained by the method described in JIS standard K7105-6.3. For the yellow index, the tristimulus values X, Y, and Z of the color were determined using a spectrophotometer U-3200 manufactured by Hitachi, Ltd. and the attached saturation calculation program, and the yellow index was determined according to the following formula.

Yellow index = 100 (1.28X-1.06Z) / Y
Evaluation was performed on the following scale from the obtained yellow index.

The difference from the yellow index of the molten film using 40% by mass of recycled material when the yellow index of the molten film not using recycled material is 0 is shown below.

As an optical film, there is no practical problem if it is ○ △ to ○.

○: 0 to less than 0.05 ○ △: 0.05 to less than 0.1 △: 0.1 to less than 0.2 Δ ×: 0.2 to less than 0.5 ×: 0.5 or more The evaluation results are shown in Table 10 below.

From the above table, the cellulose ester films 1 to 16 produced using the cellulose esters of Production Examples 1 to 16 of the present invention have a small number of deteriorated foreign matters even when used as recycled materials in the melt casting method. It turns out that coloring is excellent and it can be used as an optical use film.

Example 3
Using the cellulose ester produced in Production Example 1 to Production Example 20 of Example 1, a cellulose ester film was produced under the conditions of the following solution casting method 1 and solution casting method 2, and the same membrane as in Example 1 When the surface failure was determined, the cellulose ester film using the cellulose ester produced in Production Examples 1 to 16 according to the present invention by reproducing Example 1 was excellent in film surface failure.

<Solution casting method 1>
(Preparation of dope solution)
The following materials were sequentially put into a sealed container, the temperature in the container was raised from 20 ° C. to 80 ° C., and the mixture was stirred for 3 hours while maintaining the temperature at 80 ° C. to completely dissolve the cellulose ester. . The silicon oxide fine particles were added dispersed in a solution of a solvent to be added in advance and a small amount of cellulose ester. This dope was filtered using a filter paper (Azumi filter paper No. 244, manufactured by Azumi Filter Paper Co., Ltd.) to obtain a dope solution A.

(Preparation of dope solution A)
Cellulose ester of Production Example 1 (to Production Example 20) 100 parts by mass Trimethylolpropane tribenzoate 5 parts by mass Ethylphthalylethyl glycolate 5 parts by mass Fine particles of silicon oxide 0.1 part by mass (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.)
Tinuvin 109 (manufactured by BASF Japan) 1 part by weight Tinuvin 171 (manufactured by BASF Japan) 1 part by weight Methylene chloride 400 parts by weight Ethanol 40 parts by weight Butanol 5 parts by weight The above materials are mixed to obtain a dope solution A. The dope A thus obtained was cast through a casting die kept at a temperature of 35 ° C. onto a support having a temperature of 35 ° C. made of a stainless steel endless belt to form a web.

Next, the web was dried on the support, and the web was peeled from the support with a peeling roll when the residual solvent amount of the web reached 80% by mass.

Next, the web is transported while being dried with a drying air of 90 ° C. in a transport and drying process using a plurality of rolls arranged on the top and bottom, subsequently gripping both end portions of the web with a tenter, and then before stretching in the width direction at 130 ° C. The film was stretched so as to be 1 time. After stretching with a tenter, the web was dried with a drying air of 130 ° C. in a transport drying process using a plurality of rolls arranged vertically. After heat treatment for 15 minutes in an atmosphere with an atmosphere substitution rate of 15 (times / hour) in the drying step, the film was subjected to a knurling process with a width of 10 mm and a height of 10 μm at both ends of the film, cooled to room temperature, and wound on a core. A cellulose ester film having a thickness of 0.5 m, a thickness of 40 μm, and a length of 4000 m was produced.

<Solution casting method 2>
(Preparation of dope solution B)
Commercially available thermoplastic acrylic resin (Dianar BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw 280000) 70 parts by weight Cellulose ester of Production Example 1 (to Production Example 20) 30 parts by weight Methylene chloride 300 parts by weight Ethanol 40 parts by weight The above composition Was sufficiently dissolved with heating to prepare a dope solution B.

The produced dope solution B was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. The peeled thermoplastic acrylic resin / cellulose ester resin web was evaporated at 35 ° C., slit to 1.6 m width, and then stretched 1.1 times in the width direction with a tenter, followed by a drying temperature of 130 ° C. And dried. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C. and 140 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film Then, a knurling process having a height of 10 μm was applied and wound around the core to obtain a cellulose ester film. The film thickness was 40 μm and the winding length was 4000 m.

Example 4
<Preparation of Polarizing Plate 101>
According to the following steps 1 to 4, the polarizing plate 101 was produced by laminating the cellulose ester film 1 produced in Example 1 on both sides of the polarizing film.

(A) Production of Polarizing Film A material obtained by impregnating 10 parts by mass of glycerin and 170 parts by mass of water into 100 parts by mass of polyvinyl alcohol (hereinafter abbreviated as PVA) having a saponification degree of 99.95 mol% and a polymerization degree of 2400. After melt-kneading and defoaming, it was melt-extruded from a T-die onto a metal roll to form a film. Then, it dried and heat-processed and obtained the PVA film.

The obtained PVA film had an average thickness of 25 μm, a moisture content of 4.4%, and a film width of 3 m.

Next, the obtained PVA film was continuously processed in the order of pre-swelling, dyeing, uniaxial stretching by a wet method, fixing treatment, drying, and heat treatment to produce a polarizing film. That is, the PVA film was immersed in water at a temperature of 30 ° C. for 30 seconds to be pre-swelled, and immersed in an aqueous solution having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter at a temperature of 35 ° C. for 3 minutes. Subsequently, the film was uniaxially stretched 6 times in a 50% aqueous solution with a boric acid concentration of 4% under a tension of 700 N / m. The potassium iodide concentration was 40 g / liter, and the boric acid concentration was 40 g / liter. Then, it was immersed in an aqueous solution having a zinc chloride concentration of 10 g / liter and a temperature of 30 ° C. for 5 minutes for fixing treatment. Thereafter, the PVA film was taken out, dried with hot air at a temperature of 40 ° C., and further heat-treated at a temperature of 100 ° C. for 5 minutes. The obtained polarizing film had an average thickness of 13 μm, a polarizing performance of a transmittance of 43.0%, a polarization degree of 99.5%, and a dichroic ratio of 40.1.

(B) Production of Polarizing Plate Step 1: The polarizing film described above was immersed in a storage tank of a polyvinyl alcohol adhesive solution having a solid content of 2% by mass for 1 to 2 seconds.

Step 2: The cellulose ester film 1 was subjected to alkali saponification treatment under the following conditions. Next, excess adhesive adhered to the polarizing film immersed in the polyvinyl alcohol adhesive solution in Step 1 was lightly removed, and the cellulose ester film 1 was bonded to the polarizing film so as to be sandwiched from both sides.

(Alkaline saponification treatment)
Saponification step 2.5M-KOH 50 ° C 120 seconds Water washing step Water 30 ° C 60 seconds Neutralization step 10 parts HCl 30 ° C 45 seconds Water washing step Water 30 ° C 60 seconds After saponification treatment, water washing, neutralization, water washing in this order And then dried at 100 ° C.

Step 3: The laminate was laminated with two rotating rollers at a pressure of 20 to 30 N / cm ² and a speed of about 2 m / min. At this time, it was carried out with care to prevent bubbles from entering.

Step 4: The sample prepared in Step 3 was dried in a dryer at a temperature of 100 ° C. for 5 minutes to prepare a polarizing plate.

Step 5: A commercially available acrylic pressure-sensitive adhesive is applied to one side of the cellulose ester film 1 of the polarizing plate prepared in Step 4 so that the thickness after drying is 25 μm, and dried in an oven at 110 ° C. for 5 minutes to form an adhesive layer. And a peelable protective film was attached to the adhesive layer. This polarized light was cut (punched) into a size of 576 × 324 mm, and the polarizing plate 101 was produced.

<Production of Liquid Crystal Display Device 101>
The polarizing plate of the NEC notebook PC LaVie G type liquid crystal panel was peeled off, and the adhesive layer of the produced polarizing plate 101 and the liquid crystal cell glass were bonded as a polarizing plate on the viewing side. Moreover, the polarizing plate 101 was bonded to the liquid crystal cell also on the backlight side in the same manner as the above procedure, and the liquid crystal display device 101 was produced.

<Production of Polarizing Plates 102 to 120, Production of Liquid Crystal Display Devices 102 to 120>
In the same manner as the polarizing plate 101 and the liquid crystal display device 101, the polarizing plates 102 to 120 and the liquid crystal display devices 102 to 120 were produced using the cellulose ester films 2 to 20 produced in Example 1.

As a result of visual evaluation of the visibility of the manufactured liquid crystal display devices 101 to 120, the use of the cellulose ester films 1 to 16 of the present invention for the polarizing plate shows no film surface failure and good visibility (clearness). It was found that a liquid crystal display device can be obtained.

Claims

In a cellulose ester production method including a raw material cellulose pulverization step, an activation step, an esterification step, an aging step, and a post-treatment step, the pulverization step mixes and pulverizes the raw material cellulose and a solvent, and a mechanochemical pulverization step The manufacturing method of the cellulose ester characterized by the above-mentioned.
The solvent is at least one solvent selected from carboxylic acids, alcohols, ketones, ethers, cellosolves, or a mixed solvent of at least one solvent and water. A method for producing a cellulose ester according to 1.
The method for producing a cellulose ester according to claim 1, wherein a filtration step is provided between the esterification step and the aging step.
The cellulose ester has an average acyl group substitution degree of 1.2 to 2.95, an acyl group total carbon number of 2.0 to 9.5, and an average weight molecular weight of 100,000 to 500,000. The method for producing a cellulose ester according to claim 1 or 2.
A cellulose ester produced by the method for producing a cellulose ester according to any one of claims 1 to 4.
A cellulose ester film comprising the cellulose ester according to claim 5.