JPH0829619A - Cellulose ester film - Google Patents

Abstract

PURPOSE:To obtain a protective film for a polarizing plate which does not cause deterioration in UV absorbance, coloring or peeling from the polarizing film even when the film is exposed under high temp. high humidity conditions for a long time by incorporating a specified benzotriazole compd. CONSTITUTION:This film contains at least one kind of benzotriazole compd. expressed by formula and a plasticizer. In formula, R1-R5 may be same or different and are hydrogen atoms, halogen atoms, or 5- or 6-member heterorings. R4 and R5 may be bonded to form a 5- or 6-member carbon rings. The amt. of the benzotriazole compd. is preferably 0.1 to 5g per 1m<2> cellulose ester film. The amt. of the plasticizer is 5-20wt.% of the cellulose ester. As for the plasticizer, the amt. of a phosphate-base plasticizer is preferably <40% of the whole plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose ester film, and more specifically, to the durability of the cellulose ester film itself used for a polarizing plate of a liquid crystal display device and to protect the liquid crystal substance from UV (ultraviolet) absorption. The present invention relates to a protective film for a polarizing plate having performance.

[0002]

2. Description of the Related Art Cellulose ester films are widely used in optical applications such as protective films for polarizing plates because they have excellent transparency and can easily form a film having small anisotropy in refractive index. There is.

However, the cellulose ester film has a disadvantage inherent in the film that it turns yellow when it is exposed to ultraviolet rays for a long time.

Therefore, conventionally, a UV absorbing agent is previously mixed in a cellulose ester solution and the solution is used to form a casting film, or a UV absorbing method as described in JP-A-61-98301. It is disclosed that the agent solution is applied or dipped on a cellulose ester film to impart UV absorbability to prevent yellowing.

Further, in order to improve the flexibility and moisture resistance of the film, it is a common practice to add a plasticizer such as a phosphate ester type to the cellulose ester solution in advance.

In the case of a liquid crystal display which is generally used for instrumental display of automobiles, the polarizing plate is required to have severe moisture resistance and heat resistance.

However, when the film produced by the above-mentioned method has a uniform UV absorber when the film is produced under the conditions of high temperature and high humidity in a use environment, for example, in an atmosphere of 80 ° C. and 90% RH for about 1000 hours. Since it is dispersed and contained, the optical characteristics deteriorate due to the bleeding phenomenon, and it turns yellow and UV.
There is a problem that the absorption performance is significantly deteriorated, the adhesive force of the protective film to the polarizing film is significantly weakened, and peeling occurs. In addition, abnormal absorption peaks were observed mainly at wavelengths of 250 to 400 nm in the spectral absorption measurement, and improvement thereof has been strongly desired.

[0008]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to prevent UV even when exposed to severe conditions under high temperature and high humidity for a long time.
It is an object of the present invention to provide a cellulose ester film as a protective film for a polarizing plate, which has no possibility of deterioration of absorption capacity, coloring, or peeling of the polarizing film from the protective film.

[0009]

The above objects of the present invention have been achieved by the following method, and the present invention has been accomplished.

That is, the amount of the plasticizer with respect to at least one of the benzotriazole compounds represented by the following general formula [1] and the cellulose ester is within 20% by weight, and among the plasticizers, the phosphoric acid ester plasticizer is used. A cellulose ester film comprising a plasticizer having an agent content of 40% by weight or less.

[0011]

Embedded image

In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different, and a hydrogen atom, a halogen atom (chlorine,
Bromine, iodine, fluorine), nitro group, hydroxyl group, alkyl group (eg, methyl, ethyl, n-propyl, iso-
Propyl, aminopropyl, n-butyl, sec-butyl, te
rt-butyl, chlorobutyl, n-amyl, iso-amyl, hexyl, octyl, nonyl, stearylamidobutyl,
Decyl, dodecyl, pentadecyl, hexadecyl, cyclohexyl, benzyl, phenylethyl, phenylpropyl, etc.), alkenyl groups (eg vinyl, allyl,
Methallyl, dodecenyl, tridecenyl, tetradecenyl, octadecenyl etc.), aryl groups (eg phenyl, 4-methylphenyl, 4-ethoxyphenyl, 2-hexoxyphenyl, 3-hexoxyphenyl etc.), alkoxy groups (eg methoxy, ethoxy) , Propoxy, butoxy, chlorobutoxy, deoxy, diaminophenoxy, ethoxy, pentadecoxy, octadecoxy, etc.), acyloxy groups (eg, carbomethoxy, carbobutoxy, carbohexoxy, carbopentadecoxy, etc.), aryloxy groups (eg, phenoxy, 4 -Methylphenoxy, 2-propylphenoxy, 3-amylphenoxy, etc.), alkylthio groups (eg methylthio,
Ethylthio, t-butylthio, t-octylthio, benzylthio, etc.), arylthio groups (eg, phenylthio,
Methylphenylthio, ethylphenylthio, methoxyphenylthio, ethoxyphenylthio, naphthylthio, etc.), mono- or dialkylamino groups (eg, N-ethylamino, Nt-octylamino, N, N-diethylamino, N,
N-di-t-butylamino, etc.), an acylamino group (eg, acetylamino, benzoylamino, methanesulfonylamino, etc.), a 5- or 6-membered heterocyclic group containing oxygen or nitrogen (eg, piperidino, morpholino, pyrrolidino, Piperazino) and R ₄ and R ₅ may be closed to form a 5- or 6-membered ring composed of carbon atoms.

In the general formula [1], the substituent represented by R _{1 to} R ₅ preferably has ₅ to 36 carbon atoms, and the alkyl group preferably has 1 to 18 carbon atoms.

Examples of compounds represented by the above general formula are shown below, but the present invention is not limited thereto.

(1-1) 2- (2'-hydroxy-5'-t-butylphenyl) -benzotriazole (1-2) 2- (2'-hydroxy-3 ', 5'-di-t- Butylphenyl) -benzotriazole (1-3) 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole (1-4) 2- (2'-hydroxy -3 ', 5'-Di-t-butylphenyl) -5-chlorobenzotriazole (1-5) 2- (2'-hydroxy-5'-isooctylphenyl) -benzotriazole (1-6) 2- (2'-Hydroxy-5'-n-octylphenyl) -benzotriazole (1-7) 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl) -benzotriazole (1-8) ) 2- (2′-hydroxy-5′-dodecylphenyl) -benzotriazole (1-9) 2- (2′-hydroxy-5′-hexadecylphenyl) -benzotriazole (1-10) 2- ( 2'-Hydroxy-3'-t-amyl-5'-benzophenyl) -benzotriazole In the present invention, JP-A-60-128434 disclosed by the same applicant as the present invention, including the above compounds, is disclosed. Page 10-First
The compound examples (IV-1) to (IV-39) described on page 2 can be used.

The benzotriazole compounds according to the present invention may be used alone or in combination of two or more.

The above-mentioned benzotriazole compound used in the present invention can be easily synthesized by, for example, the method described in JP-B-44-29620 or a method similar thereto.

The amount of these benzotriazole compounds used is not uniform depending on the type of compound and the operating conditions.
The amount is preferably 0.1 to 5 g, and particularly preferably 0.2 to ² g per 1 m ^{2 of the} cellulose ester film. As a method of addition, a solution previously dissolved in an organic solvent (eg, methanol, methylene chloride, etc.) may be added to the dope composition such as cellulose triacetate according to the present invention, or may be added directly.

Examples of the plasticizer according to the present invention include phthalate esters such as dimethyl phthalate, diethylene phthalate, dibutyl phthalate, dioctyl phthalate and dimethoxyethyl phthalate, ethyl phthalyl ethylene glycolate, ethyl phthalyl ethyl glycolate, ethyl glycol. Examples thereof include glycolic acid ester compounds such as dibutyrate and ethylene glycol dipropionate, diacetylene, triacetin, and glycerin derivatives. Examples of the phosphate plasticizer include triphenyl phosphate and tricresyl phosphate.

The amount of these plasticizers used is preferably 5 to 20% by weight relative to the cellulose ester. Also, the content of phosphate ester plasticizer is 40% of the total plasticizer.
%, The performance is deteriorated such as the deterioration of the spectral absorption characteristics and the performance is unfavorable when it is left under a condition of high temperature and high humidity for a long time.

Examples of the cellulose ester film according to the present invention include cellulose acetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, and the like.
Cellulose triacetate with 250 to 400 and a bound acetic acid amount of 54 to 62% is preferable.

Examples of the solvent for the cellulose ester film according to the present invention include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol and n-butanol, lower fatty acids such as cyclohexanedioxane and methylene chloride. Group hydrocarbons and the like can be used.

The solvent ratio is preferably 70 to 95% by weight of methylene chloride, and 30 to 5% by weight of other solvents. The concentration of cellulose ester is preferably 10 to 50% by weight. The heating temperature after the addition of the solvent is preferably not lower than the boiling point of the solvent used and in the range in which the solvent does not boil, and is preferably set to 60 ° C. or higher and 80 to 110 ° C., for example. The pressure is set so that the solvent does not boil at the set temperature.

After the dissolution, it is taken out from the container while being cooled, or is taken out from the container by a pump or the like and cooled by a heat exchanger or the like, and this is used for film formation.

The method for producing the cellulose ester film in the present invention is not particularly limited and may be a method generally used in the art, for example, US Pat. No. 2,492,978,
2,739,070, 2,739,069, 2,492,977, 2,33
6,310, 2,367,603, 2,492,978, 2,607,704
No., British Patent No. 64071, No. 735892, Japanese Patent Publication No. 45-9074,
49-4554, 49-5614, 60-27562, 61-39890
No. 62-4208, etc. can be referred to.

The thickness of the cellulose ester film according to the present invention is preferably 10 to 500 μm, particularly 30 to 200 μm.

If necessary, fine particles such as silicon oxide may be added as a matting agent to the cellulose ester film of the present invention.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 The following dope composition was prepared by adding the UV absorbers shown in Table 1.

Cellulose triacetate (oxidation degree 61.0%) 100 parts by weight Triphenyl phosphate 3 parts by weight Ethylphthalylethyl glycolate 12 parts by weight Exemplified compound 1-3 1 part by weight Exemplified compound 1-7 1 part by weight Methylene chloride 430 parts by weight 90 parts by weight of methanol The above composition was placed in a closed container, kept at 80 ° C. under pressure and completely dissolved while stirring.

Next, this dope was filtered, cooled and kept at 33 ° C., and a rotating length of 6 m (effective length) set in two drums.
(5.5m) evenly cast on an endless stainless band, and after evaporating the solvent until peeling is possible,
After peeling from the stainless steel band, the drying was completed while being conveyed by a large number of rolls to obtain a film having a thickness of 80 μm.

The cellulose triacetate film prepared above was used as a protective film, and a part of the film was alkali-saponified by the following method to make the surface hydrophilic, and then the polarizing film film prepared by the following method was used. A polarizing plate was prepared by bonding with a vinyl alcohol adhesive.

-Alkali saponification treatment of cellulose acetate film-A part of the acetate film (TAC film) of 2N60 was prepared from the 80 μm cellulose prepared above.
It was immersed in a sodium hydroxide aqueous solution at 0 ° C. for 3 minutes, washed with water and dried to obtain a cellulose triacetate film having a hydrophilic surface.

-Production of Polarizing Film- A polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part by weight of iodine, 2 parts by weight of potassium iodide and 4 parts by weight of boric acid, and stretched 4 times at 50 ° C. A polarizing film was obtained.

-Production of Polarizing Plate- The alkali-saponified cellulose triacetate film is cut into a size of 18 cm × 5 cm and placed on a glass plate.

The polarizing film is cut into the same size as the film sample, and immersed in a polyvinyl alcohol adhesive solution tank having a solid content of 2% by weight for 1 to 2 seconds (both sides).

Excess adhesive attached to the polarizing film is gently removed and placed on the film sample.

The alkali-saponification-treated cellulose triacetate film having the same size as the above is superposed so that the adhesive surface of the film sample is in contact with the adhesive surface.

Excess adhesive and air bubbles are removed from the ends using a hand roller, and they are bonded together. The pressure of this roller is about 2-3 kg / cm ² , and the roller speed is about 2 m / min.

The three-layered sample obtained in step 3 is placed in a dryer at 80 ° C. and left for about 10 minutes.

[Evaluation Method] Adhesion Property Initial Adhesion Property: When the polarizing plate was cut into a 5 cm × 5 cm square by using a single blade, it was evaluated whether or not the edge of the adhesive surface did not float.

◯: There is no floating on the adhesive surface. Δ: Slight (within 2 mm) floating occurs. ×: 3 mm or more floating occurs. High temperature and high humidity durability: 5 cm × 5 using the polarizing plate with a single edge.
Create a sample that is cut into squares with a size of 80 cm and 90% R
After being left under the condition of H for 1000 hours, it is evaluated whether or not the edge of the adhesive surface is floating.

◯: There is no floating of the adhesive surface Δ: Slight (within 2 mm) floating occurs ×: 3 mm or more floating occurs Evaluation of transmittance change rate The cellulose triacetate film prepared above was heated to 80 ° C.
Enclose in a closed container under conditions of high temperature and high humidity of 90% RH, leave it at the same temperature for 1000 hours, then use a spectrophotometer to measure 250-600nm
Was measured and the maximum degree of change ΔT ₁ (%) in the range of 250 to 350 nm with respect to the spectral absorption characteristics of the cellulose triacetate film prepared as described above, which was similarly left under the condition of 23 ° C. and 55% RH, and The maximum change ΔT ₂ (%) in the range of 400 to 600 nm was evaluated.

◯: Change of 2% or less △: Change of 2 to 10% ×: Change of 11 to 20% XX: Change of 20% or more Evaluation of alteration of film 15 cm of the cellulose triacetate film prepared above
Cut into a size of × 10 cm, put in a bottle with a capacity of 1000 ml that has been replaced with air at 80 ° C and 90% RH, seal, and leave for 1000 hours at 80 ° C and 90% RH under high temperature and high humidity, then color, The damage such as cracks was evaluated.

◯: Almost no change, transparent sheet-like Δ: Brown-colored sheet-like ×: Brown-colored, powdery when bent Example 2 The following dope composition was prepared in the same manner as in Example 1. did.

Cellulose triacetate (oxidation degree: 61.0%) 100 parts by weight Triphenyl phosphate 4 parts by weight Ethylphthalylethyl glycolate 9 parts by weight Exemplified compound 1-3 1.5 parts by weight Methylene chloride 550 parts by weight Methanol 30 parts by weight n-butanol 60 Parts by weight This dope was then filtered, cooled and kept at 33 ° C. and evenly flowed from the first casting port shown in FIG. 2 located on a rotating 6 m long endless stainless band placed on two drums. Then, the dope described in Example 2 was applied from the second casting port to a finished film thickness of 80 μm, and 80% and 20%, respectively.
%, The solvent is evaporated until it can be peeled off from the stainless steel band, then peeled from the stainless steel band, and the drying is completed while being conveyed by multiple rolls. A film having a thickness of 80 μm was obtained.

The cellulose triacetate film thus obtained was evaluated in the same manner as in Example 1.

The evaluation results are shown in Table 1.

Example 3 The following dope composition was prepared and a cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1.

Cellulose triacetate (oxidation degree 61.0%) 100 parts by weight Ethylphthalylethyl glycolate 12 parts by weight Exemplified compound 1-5 2 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight Cellulose acetate film thus obtained Was evaluated in the same manner as in Example 1.

The evaluation results are shown in Table 1.

Comparative Example 1 The following dope composition was prepared and a cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1.

Cellulose triacetate (oxidation degree 61.0%) 100 parts by weight Triphenyl phosphate 8 parts by weight Ethylphthalylethyl glycolate 6 parts by weight Exemplified compound 1-3 1 part by weight Exemplified compound 1-7 1 part by weight Methylene chloride 430 parts by weight 90 parts by weight of methanol The cellulose triacetate film thus obtained was evaluated in the same manner as in Example 1.

The evaluation results are shown in Table 1.

Comparative Example 2 A triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1 by adding the following benzophenone-based compound as an ultraviolet absorber and adjusting the following dope composition.

Cellulose triacetate (oxidation degree 61.0%) 100 parts by weight Triphenyl phosphate 4 parts by weight Ethylphthalylethyl glycolate 9 parts by weight Ultraviolet absorber (Compound 2-1 below) 1.1 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight Parts The cellulose triacetate film thus obtained was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 3 A triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1 by adding the following benzophenone-based compound as an ultraviolet absorber and adjusting the following dope composition.

Cellulose triacetate (oxidation degree 61.0%) 100 parts by weight Triphenyl phosphate 13 parts by weight Ultraviolet absorber (compound 2-2 below) 1.2 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight Cellulose thus obtained The triacetate film was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 4 The following dope composition was prepared and a cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1.

Cellulose triacetate (acetylation degree 61.0%) 100 parts by weight Triphenyl phosphate 9 parts by weight Ethylphthalyl ethylene glycolate 16.5 parts by weight Exemplified compound 1-5 1.6 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight The cellulose triacetate film thus obtained was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 5 The following dope composition was prepared and a cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1.

Cellulose triacetate (acetylation degree 61.0%) 100 parts by weight Triphenyl phosphate 20 parts by weight Ethylphthalylethyl glycolate 10 parts by weight Exemplified compound 1-5 2 parts by weight Methylene chloride 430 parts by weight Methanol 90 parts by weight The cellulose triacetate film thus obtained was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 6 The following compound of benzophenone type was added as an ultraviolet absorber to prepare the following dope composition, and a cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1.

Cellulose triacetate (acetylation degree 61.0%) 100 parts by weight Triphenyl phosphate 9 parts by weight Ethylphthalylethyl glycolate 16 parts by weight Exemplified compound (Compound 2-1 below) 1.5 parts by weight Cellulose thus obtained The triacetate film was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

Comparative Example 7 A cellulose triacetate film having a thickness of 80 μm was obtained in the same manner as in Example 1 by adding the following benzophenone-based compound as an ultraviolet absorber and adjusting the following dope composition.

Cellulose triacetate (acetylation degree 61.0%) 100 parts by weight Triphenyl phosphate 22 parts by weight Exemplified compound (Compound 2-1 below) 1.5 parts by weight The cellulose triacetate film thus obtained was treated in the same manner as in Example 1. It was evaluated by. Table 1 shows the evaluation results
It was shown to.

[0067]

Embedded image

A part of the spectral absorption characteristics is shown in FIG.

In the figure, (1) shows the sample of Example 1 at 23 ° C. and 55%
After being left for 1000 hours at RH, (2) is the sample of Example 1 of 80
After left at 1000 ° C. and 90% RH for 1000 hours, (3) shows the sample of Comparative Example 1 at 23 ° C. and after left at 55 ° C. RH for 1000 hours, (4) shows the sample of Comparative Example 1 at 80 ° C. and 90 ° C. It is the spectral absorption characteristics of the film after standing at RH for 1000 hours.

[0070]

[Table 1]

As can be seen from the table, the cellulose ester film obtained by the method of the present invention has no coloring or film deformation even under severe conditions, and is used as a polarizing plate for a long time in a harsh atmosphere. It can be seen that there is no deterioration in the adhesiveness with the polarizing film.

[0072]

EFFECTS OF THE INVENTION According to the method of the present invention, (1) UV absorption performance is not deteriorated, (2) Spectral absorption characteristics are not deteriorated even when left for a long time under severe high temperature and high humidity conditions. 3)
An excellent cellulose ester film was obtained as a protective film for a polarizing plate, which has high durability such as no deterioration such as discoloration and cracking, and (4) no deterioration in adhesiveness between the polarizing film and the protective film.

[Brief description of drawings]

FIG. 1 is a diagram showing the spectral absorption characteristics of a film after being left for 1000 hours at room temperature, high humidity and high temperature.

FIG. 2 is a cross-sectional view of the film forming machine used in Example 2.

[Explanation of symbols]

 1 First casting port 2 Endless stainless steel band 3 Second casting port 4 Separation position

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Ishibashi 1st Sakura-cho, Hino City, Tokyo Konica Stock Company In-house

Claims (1)

[Claims] 1. The amount of the plasticizer with respect to at least one of the benzotriazole compounds represented by the following general formula [1] and the cellulose ester is within 20% by weight, and the phosphoric acid ester plasticizer among the plasticizers is used. A cellulose ester film comprising a plasticizer having an agent content of 40% by weight or less. Embedded image [In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different, and are a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group,
It represents an alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group or a 5- or 6-membered heterocyclic group, and R ₄ and R ₅ are ring-closed and are 5 or 6-membered. It may form a carbocycle. ]