JP2003183328A - Optical film - Google Patents

Abstract

(57) [Problem] To provide an optical film having heat resistance and excellent transparency. SOLUTION: 4,4-Diacetyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene or 4-acetyl-4-ethoxycarbonyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene An optical film comprising a polymer obtained by polymerizing the polymer. The polymer is suitable as an optical film because it has good moldability into a film, good transparency of the obtained film, and low phase difference. The glass transition temperature of the polymer is 120 ° C
To 250 ° C., and the number average molecular weight is preferably 20,000 to 500,000.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical film having excellent heat resistance. More specifically, the present invention relates to an optical film which is made of a polymer of a specific compound or a polymer containing a specific repeating unit and has excellent heat resistance and transparency.

[0002]

2. Description of the Related Art Various optical films are used in the field of liquid crystal display devices, and typical examples thereof include retardation films, polarizer films, polarizer protective films, transparent conductive films and the like. Further, by utilizing its transparency, optical films are used for lighting equipment, office supplies, photographic films, and surface protection also in fields other than liquid crystal display devices.

Examples of plastics used for these optical films include acrylic resins such as polymethylmethacrylate which are excellent in transparency and low retardation. However, acrylic resins have the problem of low heat resistance, and many attempts have been made to improve the heat resistance of acrylic resins. For example, methods of copolymerizing N-substituted maleimide with methyl methacrylate and (co) polymerizing a monomer in which a bulky alicyclic hydrocarbon substituent is introduced into the ester portion of methacrylate have been investigated.
However, when a maleimide compound is copolymerized, the transparency may be impaired, and it is difficult to balance heat resistance and mechanical strength when introducing a bulky substituent into the ester portion.

Japanese Patent Publication No. 9-502429 discloses a polymer having a repeating unit having a cyclic structure in the main chain as shown in the general formula (3).

[0005]

[Chemical 3]

(Wherein R ² and R ³ are independently COO
Selected from the group consisting of R, CN, aryl, substituted aryl, COOH, halogen, C (O) NHR ⁵ , C (O) NR ⁶ R ⁷ ; X and Y are independently COOH, COO.
R, CN, R ⁴ CO-, C (O) NHR ⁵ , C (O) NR
⁶ R ⁷ , P (O) (OR ⁸ ) ₂ and SO ₂ R ⁹ ; provided that when R ² and R ³ are both COOCH ₃ or both phenyl, then both X and Y are H. Or X and Y together with the carbon atom to which they are attached form a carbocyclic or heterocyclic ring system which may contain oxygen, sulfur or nitrogen atoms. to; R is, C ₁ -C ₁₈ alkyl; C ₂ -C ₁₈ alkenyl; C ₂ -C ₁₂ alkynyl; C ₅
C ₈ cycloalkyl; or any of the above, wherein hydroxy, amino, azido, cyano,
Nitro, aldehyde, thioether, sulfonyl, cyanato, isocyanato, thiocyanato, isothiocyanato, epoxy, silyl, silyloxy, aziridine, acyloxy, carboxy, ester, carbamoyl, carbonyldioxy, urethane, ureylene, carbonyl, C
₁ -C ₆ dialkoxy phosphoryl, C ₁ -C ₆ dialkoxy thio phosphoryl, tri (C ₁ -C ₆ alkoxy) silyl,
C ₁ -C ₆ alkoxy, those are substituted with a substituent selected from the group consisting of from phenyl; substituted aryl, _{halogen, - [(CH 2) m} O] n -H and - [(CH _{2) m}
O] _n -alkyl, where m and n are integers; or any combination of any of the above groups; any or combination of those groups is reacted in a pre- or post-polymerization step. R ⁴ may be a C ₁ -C ₆ alkyl group, a cycloalkyl group or a substituted aryl group; R ⁵ may be H, C ₁
C ₁₈ alkyl, C ₂ -C ₁₈ alkenyl, C ₂ -C ₁₂ alkynyl; C ₅ -C ₈ cycloalkyl; or any of the above, hydroxy, amino, azide,
Cyano, cyanato, isocyanato, epoxy, silyl,
Silyloxy, carboxy, ester, carbamoyl, C
₁ -C ₆ alkoxy, phenyl, those are substituted with a substituent selected from the group consisting of substituted aryl and halogen; or, any combination of any of the foregoing groups;
Any or a combination of those groups may be reacted in a pre- or post-polymerization step to further modify their functionality; R ⁶ and R ⁷ are independently C ₁ -C ₁₈ alkyl; C ₁ -C ₈ cycloalkyl, aralkyl and alkylaryl; R ⁸ is, H is selected from C ₁ -C ₁₈ group consisting of alkyl; R ⁹ is, C ₁ -C ₁₈ alkyl, more aryl or substituted aryl Further, in the above publication, R in the general formula (3) is an ethyl group,
Disclosed is a transparent thin film composed of a polymer in which X and Y are ethoxycarbonyl groups, and the glass transition temperature of the polymer measured by a differential scanning calorimeter (DSC) is 85 ° C. and the glass transition temperature of polyethylmethacrylate ( Somewhat higher than 65 ° C).

However, there is no specific example of the polymer represented by the general formula (3), which has a glass transition temperature higher than that of polymethylmethacrylate (104 ° C.) and gives a transparent film.

[0008]

The polymer having a glass transition temperature of about 85 ° C., which is specifically disclosed in the above publication, has insufficient heat resistance, and thus even if a transparent thin film is obtained, it can be used as an optical film. Cannot be applied. Therefore, the present inventor has conducted various studies for the purpose of obtaining a film which can improve the heat resistance of the polymer without impairing the transparency of the thin film and can be used for optical applications.

[0009]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, among the monomers giving the polymer of the general formula (3), a polymer of a specific compound is used. We have found that the film has heat resistance required for optical applications and is excellent in transparency, and completed the present invention.

That is, the present invention provides an optical film comprising a polymer of a compound represented by the following general formula (1).

[0011]

[Chemical 4]

(Wherein R ¹ represents a methylcarbonyl group or an ethoxycarbonyl group). The present invention also provides an optical film comprising a polymer whose repeating unit is represented by the following general formula (2). Is.

[0013]

[Chemical 5]

(In the formula, R ¹ represents a methylcarbonyl group or an ethoxycarbonyl group) wherein, in the above polymer,
The glass transition temperature measured by a differential scanning calorimeter (DSC) is preferably 120 to 250 ° C., and the polystyrene-reduced number average molecular weight measured by gel permeation chromatography is preferably 20,000 to 500,000.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer used in the optical film of the present invention is 4,4-diacetyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene or 4-
It is obtained by polymerizing acetyl-4-ethoxycarbonyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene.

The glass transition temperature of the polymer obtained by using 4,4-diacetyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene is 4-acetyl-4-ethoxycarbonyl-2,6- It is higher than the glass transition temperature of the polymer obtained by using bis (methoxycarbonyl) -1,6-heptadiene, and a preferable optical film is obtained from the viewpoint of heat resistance.

Further, instead of these monomers, 2,
4,4,6-tetrakis (methoxycarbonyl) -1,
When 6-heptadiene is used, a polymer having the same high heat resistance can be obtained, but it is not preferable as a polymer for film formation because the molded product is brittle.

The above-mentioned monomers are the same as those described in JP-A-9-50242.
It can be obtained by the reaction of acetylacetone or ethyl acetoacetate with methyl 2- (bromomethyl) propenoate according to the method described in JP-A-9.

The method for producing the polymer of the present invention is not particularly limited, and generally known polymerization methods such as radical polymerization, anionic polymerization, cationic polymerization, group transfer polymerization, and coordinated anionic polymerization can be adopted. Radical polymerization is most preferable because of its simplicity.

For example, the polymer used for the optical film of the present invention can be obtained by radical polymerization using azobisisobutyronitrile as an initiator.

Here, the molecular structure of the obtained polymer is considered to be a polymer composed of the repeating unit represented by the general formula (2),
It is possible to identify the structure by NMR analysis.

Differential scanning calorimetry (DSC) of the above polymers
The glass transition temperature measured by the method is preferably 120 to 250 ° C. from the viewpoint of heat resistance and molding processability, and 130 to 230
C is more preferred. If the glass transition temperature is low, the optical film cannot be used at a high temperature, or the temperature dependence of optical properties such as retardation tends to increase even at a high temperature, which is not preferable. On the other hand, if the glass transition temperature is too high, molding and processing become difficult.

The molecular weight of the polymer of the present invention is 20,000 to 50 in terms of polystyrene equivalent number average molecular weight measured by gel permeation chromatography (GPC).
It is preferably 30,000 and preferably 30,000 to 20.
More preferably, it is 40,000-
200,000 is more preferable. If the number average molecular weight is small, a film having sufficient strength cannot be obtained, or in extreme cases, the heat resistance decreases. On the other hand, when the number average molecular weight is large, moldability and processability tend to be lowered.

The optical film of the present invention can be produced by a melt molding method or a solution casting method. In the case of manufacturing by the melt molding method, a method using a T die or the like can be applied. When the solution casting method is used, it may be cast on a support using a bar coater, comma coater, T-die, T-die with bar, doctor knife, meir bar, roll coat, die coat, etc. it can.

The optical film of the present invention can be stretched by a stretching machine or the like. The temperature condition for stretching is not particularly limited as long as the stretching effect is produced, but it is 30 ° C lower than the glass transition temperature of the film to 50 ° C lower than the glass transition temperature.
It is desirable to operate within a high temperature range. When the stretching is carried out within these temperature ranges, the effect of stretching can be easily obtained.

As the stretching means, a general stretching method such as roll stretching or tenter stretching can be used. Further, the stretching may be carried out by any of uniaxial method, sequential biaxial method and simultaneous biaxial method.

The thickness of the optical film of the present invention can be selected according to the application. Generally, 5-500
The range of μm, preferably 10 to 300 μm is used. When the optical film is produced by stretching, the thickness of the raw film before stretching may be set to a thickness in consideration of the influence of stretching.

Further, the polymer used in the present invention may be blended with an antioxidant and / or an ultraviolet absorber, if necessary. The blending amount is 0.000001 with respect to 100 parts by weight of the polymer. -10 parts by weight, preferably 0.0
0001 to 5 parts by weight.

As other additives, flame retardants, antibacterial agents,
A heat stabilizer, a light stabilizer, a fluidity improver, a plasticizer, a processing aid, an antistatic agent, etc. can be added, and these can be used alone or in combination of two or more.

The optical film of the present invention can be used for various purposes, but it can be used for optical applications such as retardation film and polarizer protective film by utilizing its excellent transparency, heat resistance and low retardation property. Various protective films, antireflection films, transparent conductive films, viewing angle widening films, diffusion films,
It can be used as a reflective film. Among these, it is preferably used for a retardation film.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Each physical property value of the polymer and the film was measured as follows.

Number average molecular weight: GPC manufactured by Waters
Using 510 as the solvent, chloroform was used as a solvent, and the number average molecular weight in terms of polystyrene was measured.

Glass transition temperature: Shimadzu DSC-
50 was used to measure up to 250 ° C. at a temperature rising rate of 20 ° C./min. The glass transition temperature of the polymer was determined from the change point of the DSC profile.

Total light transmittance: Nippon Denshoku Industries turbidity meter 3
The total light transmittance of the film at a temperature of 23 ° C. was measured using 00A.

Haze: Turbidity meter 300 manufactured by Nippon Denshoku Industries Co., Ltd.
A was used to measure the haze of the film at a temperature of 23 ° C.

Phase difference: K ・ S Systems phase difference meter K
OBRA was used to measure the phase difference at 590 nm by the rotation analyzer method.

(Production Example 1) In a 100 mL reaction vessel equipped with a stirrer, 7,4-mL 4,4-diacetyl-2,6-bis (methoxycarbonyl) -1,6-heptadiene, 16 mL acetonitrile, 0.006 azobisisobutyronitrile was added.
9 g was added. After replacing the inside of the reaction vessel with nitrogen, the reaction was carried out at 70 ° C. for 6 hours. Then, the reaction solution was poured into a large amount of n-hexane to stop the reaction. The obtained solid is n-
Polymer 1 was obtained by washing with hexane and vacuum drying at 60 ° C. for 24 hours.

GPC analysis of the polymer 1 showed that
The number average molecular weight was 65,000. Further, it was confirmed from the NMR spectrum that it was a repeating unit of the general formula (2) (in the formula, R ¹ is a methylcarbonyl group). The glass transition temperature by DSC was 180 ° C.

(Production Example 2) 4,4-diacetyl-2,6
-Bis (methoxycarbonyl) -1,6-heptadiene instead of 4-acetyl-4-ethoxycarbonyl-
Polymer 2 was synthesized in the same manner as in Production Example 1 except that 2,6-bis (methoxycarbonyl) -1,6-heptadiene was used.

When the GPC analysis of the polymer 2 was conducted,
The number average molecular weight was 40,000. The glass transition temperature by DSC was 140 ° C.

(Production Example 3) 4,4-diacetyl-2,6
A polymer was prepared in the same manner as in Production Example 1 except that 2,4,4,6-tetrakis (methoxycarbonyl) -1,6-heptadiene was used instead of -bis (methoxycarbonyl) -1,6-heptadiene. 3 was synthesized.

When GPC analysis of the polymer 3 was carried out,
The number average molecular weight was 31,000. The glass transition temperature by DSC was 165 ° C.

(Production Example 4) 4,4-diacetyl-2,6
A polymer was prepared in the same manner as in Production Example 1 except that 2,4,4,6-tetrakis (ethoxycarbonyl) -1,6-heptadiene was used instead of -bis (methoxycarbonyl) -1,6-heptadiene. 4 was synthesized.

When GPC analysis of the polymer 4 was carried out,
The number average molecular weight was 30,000. The glass transition temperature by DSC was 85 ° C.

(Example 1) Polymer 1 synthesized in Production Example 1
Methylene chloride solution (22% by weight) was prepared, cast on a polyethylene terephthalate film using a glass rod, and allowed to dry at room temperature. The film thickness of the obtained film was 50 μm. When the total light transmittance and haze of this film were measured, they were 93% and 0.
It was 3%. The retardation of the film was 7 nm.

(Example 2) Polymer 2 synthesized in Production Example 2
A film was prepared in the same manner as in Example 1.
The film thickness of the obtained film was 50 μm. When the total light transmittance and haze of this film were measured, they were 93% and 0.2%, respectively. The retardation of the film was 8 nm.

Comparative Examples 1 and 2 Methylene chloride solutions (20% by weight) of the polymers 3 and 4 synthesized in Production Examples 3 and 4 were prepared and cast on a polyethylene terephthalate film using a glass rod, It was left to dry at room temperature. When polymer 3 was used, fine cracks were formed after casting, and a film could not be produced. When the polymer 4 was used, a film could be prepared and the film thickness was 50 μm. When the total light transmittance and haze of this film were measured, they were 92% and 0.3%, respectively.
Met. The retardation of the film was 8 nm.

(Comparative Example 3) A methylene chloride solution (20% by weight) of polymethylmethacrylate (Sumitpex LG, manufactured by Sumitomo Chemical Co., Ltd.) was prepared, cast on a polyethylene terephthalate film, and allowed to dry at room temperature. The film thickness was 50 μm. When the total light transmittance and haze of this film were measured, they were 93% and 0.2%, respectively. The retardation of the film was 8 nm.

The results of Examples 1 and 2 and Comparative Examples 1 to 3 are summarized in Table 1.

[0050]

[Table 1]

As is clear from the above results, the polymer used in the present invention can provide an optical film having good moldability into a film and high heat resistance.

[0052]

The optical film of the present invention has heat resistance, excellent transparency and low retardation, and is useful as a retardation film and various optical protective films.

Claims (4)

[Claims] 1. An optical film comprising a polymer of a compound represented by the following general formula (1). [Chemical 1] (In the formula, R ¹ represents a methylcarbonyl group or an ethoxycarbonyl group) 2. An optical film in which the repeating unit comprises a polymer represented by the following general formula (2). [Chemical 2] (In the formula, R ¹ represents a methylcarbonyl group or an ethoxycarbonyl group) 3. A differential scanning calorimeter (DSC) of the polymer.
The glass film according to claim 1, which has a glass transition temperature of 120 to 250 ° C. measured by. 4. The optical film according to claim 1, wherein the polymer has a polystyrene reduced number average molecular weight of 20,000 to 500,000 as measured by gel permeation chromatography.