JP2003139950A - Method for manufacturing optical retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently and conveniently manufacturing an optical retardation film of which the optical retardation is highly precisely uniformized and which exhibits excellent display quality throughout nearly the entire region when installed in a liquid crystal display device. SOLUTION: A thermoplastic norbornene type resin film is produced by film forming a thermoplastic norbornene type resin composition containing 1-100 pts.wt. thermoplastic resin which is soluble in the thermoplastic norbornene type resin, has a glass transition temperature lower than that of the thermoplastic norbornene type resin and has 200-10,000 number-average molecular weight in relation to 100 pts.wt. of the thermoplastic norbornene type resin. The method for manufacturing the optical retardation film is characterized by immersing the thermoplastic norbornene type resin film in a solvent which does not dissolve the thermoplastic norbornene type resin but dissolves the thermoplastic resin, extracting part of the thermoplastic resin therefrom and stretching the film. Also the method for manufacturing the optical retardation film is characterized by using a melting extrusion film forming method as the film forming method for the thermoplastic norbornene type resin composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a retardation film.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, a reflection type liquid crystal display device is mainly incorporated in a portable information terminal such as a mobile phone or a PDA in order to take advantage of the original advantage of low power consumption.

In recent years, this reflective liquid crystal display device has been
In contrast to the conventional method of using (twisted nematic) liquid crystal to combine two polarizing plates and a reflector on the back surface, a new mode in which brightness is improved by using only one polarizing plate becomes mainstream. It's starting. In this new mode, since circularly polarized light is used for black and white display, a retardation film (phase difference compensation film) for converting linearly polarized light into circularly polarized light must be installed between the polarizing plate and the liquid crystal cell. Is mandatory. On the other hand, this retardation film becomes a circularly polarizing plate when combined with a polarizing plate, and is widely used also for preventing reflection on a touch panel, a PDP (plasma display panel), an EL (electroluminescence) display or the like. .

Thus, the industrially useful retardation film is generally produced by drawing an amorphous thermoplastic resin film. Examples of the thermoplastic resin used include polycarbonate resin, cellulose resin, vinyl chloride resin, acrylonitrile resin, styrene resin, polyolefin resin, polysulfone resin, and thermoplastic saturated norbornene resin. . These thermoplastic resins are formed into films by a casting (solution cast) film forming method, a calender film forming method, a melt extrusion film forming method, or the like, and stretched in the longitudinal direction or the transverse direction to form a retardation film.

The retardation compensation performance of the above retardation film is
It is represented by a so-called retardation value. The retardation value (R) is represented by a relational expression of R = Δn × d, where Δn is the anisotropy (birefringence) of the refractive index of the polymer film and d is the thickness of the film.

On the other hand, in the liquid crystal display device, it is strongly demanded that color unevenness and contrast unevenness hardly occur over the entire surface of the display. In order to provide a liquid crystal display device capable of such a uniform display, it is strongly required that the retardation film has a uniform in-plane retardation regardless of the type of the thermoplastic resin used. Has been.

The occurrence of color unevenness and contrast unevenness is caused when a retardation film is incorporated into a liquid crystal display device and evaluated.
This is because it is easy to distinguish the difference in retardation value between two adjacent points. Therefore, the retardation film is required to have more uniform retardation value. Further, as is clear from the above relational expression, since the retardation value is affected by the thickness of the film, if the thickness variation of the film (thickness unevenness) is large, the variation of the retardation value is also large. In other words, it is possible to improve the uniformity of the retardation value by suppressing the film thickness variation. It is difficult to unambiguously set the standard of uniformity of retardation value because there are individual differences, but as a condition that it is not visually recognized as color unevenness or contrast unevenness, phase difference fluctuation (phase difference unevenness) in a short section is It is required to be small, and specifically, one of the criteria is that the phase difference variation is 1 nm / cm or less.

Conventionally, in order to obtain a retardation film having a uniform retardation, a thermoplastic resin film formed by a casting method has been used because of its excellent thickness accuracy and surface smoothness and high optical uniformity. There is. For example, Japanese Patent Laid-Open No. 4-204503
In the publication, a thermoplastic resin film formed by a casting film forming method, in a method for producing a retardation film having a birefringence by stretching, the solvent content of the thermoplastic resin film is determined by solid content. A method for producing a retardation film which is stretched to 2 to 10% based on the standard is disclosed, and JP-A-5-113506 discloses that a methylene chloride solution of a polycarbonate resin is cast and then stretched. In the method for producing a retardation film having birefringence, when the solvent content of the cast film formed is in the range of 3 to 10% based on the solid content, the film is formed in an atmosphere of 155 to 175 ° C. A method for producing a retardation film that is stretched in the traveling direction is disclosed.

Further, as a method for producing a retardation film by the melt extrusion film forming method, for example, JP-A-2-256003 is used.
In the publication, a thermoplastic resin film having a sinusoidal thickness variation with a pitch of 50 mm or less and an amplitude of thickness of 0.5 μm or more when continuously measuring the change in thickness in the extrusion direction, And a film formed by uniaxially or biaxially stretching the film at right angles to the extrusion direction, and having a retardation value of 120.
A retardation film having a thickness of 0 nm or less and a retardation width of 10% or less is disclosed.

However, in the case of the retardation film disclosed in the above publication, when the pitch is 50 mm and the thickness amplitude is 0.5 μm, the thickness variation is 0.1 μm / cm.
It turns out that. Since the thickness of the retardation film currently in practical use is generally about 50 μm, when the relational expression of the retardation value is taken into consideration, the retardation variation becomes proportional to the thickness variation, and thus it is in practical use. Four
With a phase difference of 00 to 2000 nm, 0.8 to 4.0 nm /
The phase difference fluctuation is about cm, and most of the phase difference becomes unsatisfactory.

On the other hand, among the above-mentioned amorphous thermoplastic resins, thermoplastic saturated norbornene resins have a relatively high glass transition temperature and a very small photoelastic constant, so that the stability of the phase difference against environmental changes is stable. Is more suitably used as the base polymer of the retardation film.

However, even if a thermoplastic saturated norbornene-based resin is used as the base polymer and a retardation film is produced by the production method disclosed in the above publications, the obtained retardation film has a large thickness variation. The phase difference of the retardation film is difficult to be uniformized to a level that is sufficiently satisfactory for practical use, and when the retardation film is incorporated into a liquid crystal display device, it has a fine pitch that can be visually discriminated. There is a problem that color unevenness occurs.

[0013]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is that the phase difference is made uniform with high accuracy, and when it is incorporated in a liquid crystal display device, an excellent display quality is obtained over almost the entire area. An object of the present invention is to provide an efficient and simple method for producing an expressed retardation film.

[0014]

The method of producing a retardation film of the present invention is compatible with 100 parts by weight of a thermoplastic norbornene resin and has a glass transition temperature lower than that of 100 parts by weight. Average molecular weight is 200-100
The thermoplastic norbornene-based resin film obtained by forming the thermoplastic norbornene-based resin composition containing 1 to 100 parts by weight of the thermoplastic resin of No. 00 is a thermoplastic resin without dissolving the thermoplastic norbornene-based resin. It is characterized in that it is immersed in a solvent capable of dissolving it, a part of the thermoplastic resin is extracted, and then stretched.

The thermoplastic norbornene-based resin (hereinafter simply referred to as "norbornene-based resin") used in the present invention may be a known norbornene-based resin and is not particularly limited, but for example, norbornene-based resin may be used. Ring-opening (co) polymer of monomer, ethylene if necessary,
Examples thereof include addition (co) polymers of norbornene-based monomers having olefin-based monomers such as propylene and other α-olefins as a copolymerization component, and those having unsaturated bonds are resins saturated by hydrogenation. Is preferred. These norbornene-based resins may be used alone or in combination of two or more kinds.

As the norbornene-based monomer, Japanese Patent Application Laid-Open Nos. 5-39403, 5-212828, 3038825, and 30197 are disclosed.
No. 41, Japanese Patent No. 3030953 and the like known norbornene-based monomer may be used, but not particularly limited, for example, norbornene, methanooctahydronaphthalene, dimethanooctahydronaphthalene, dimethanododeca. Hydroanthracene, dimethanodecahydroanthracene, trimetanododecahydroanthracene, and the like; and substituted products thereof; dicyclopentadiene,
2,3-dihydrocyclopentadiene, methanooctahydrobenzoindene, dimethanodecahydrobenzoindene, methanooctahydrofluorene, dimethanohydrooctafluorene and the like, and substitution products thereof can be mentioned. These norbornene-based monomers may be used alone or in combination of two or more kinds.

The substituent in the above-mentioned substituent may be a known hydrocarbon group or polar group and is not particularly limited, but examples thereof include an alkyl group, an alkylidene group, an aryl group, an alkoxycarbonyl group, a halogen group, Hydroxyl group, carboxylic acid group, non-hydroxyl group, ester group, amino group,
Examples thereof include a pyridyl group, a cyano group, a silyl group, an epoxy group, an acryl group and a methacryl group. These substituents may be used alone or in combination of two or more.

Specific examples of the norbornene-based monomer substituted with a substituent are not particularly limited, but for example, 5-methyl-2-norbornene and 5,5-
Dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-
Norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5
-Phenyl-2-norbornene, 5-phenyl-5-methyl-2-norbornene and the like can be mentioned.

The norbornene-based resin used in the present invention is not particularly limited, but has a number average molecular weight in terms of standard polystyrene of 5000 to 5,000 by GPC measurement (solvent: tetrahydrofuran or cyclohexane).
It is preferably 40,000, more preferably 7,000.
˜35,000, more preferably 8,000
~ 30,000.

When the number average molecular weight of the norbornene-based resin is less than 5,000, the mechanical strength of the obtained norbornene-based resin film or retardation film may be insufficient. On the contrary, when it exceeds 40,000, the norbornene-based resin may be used. The moldability (film-forming property) of the resin composition may deteriorate.

Commercially available products of the above norbornene resins are not particularly limited. For example, products having a polar group, such as the product name "Arton" manufactured by JSR Co., Ltd., and products having no polar group. Examples include the product name “Zeonor” series manufactured by Nippon Zeon Co., Ltd.

The thermoplastic resin used in the present invention is required to be compatible with the norbornene resin and have a lower glass transition temperature (Tg) than the norbornene resin.

When the Tg of the thermoplastic resin is equal to or higher than the Tg of the norbornene-based resin, the norbornene-based resin film is usually stretched at a temperature near the Tg of the norbornene-based resin, so that the thermoplastic resin does not melt sufficiently. It becomes impossible to obtain a uniform retardation film.

The thermoplastic resin must have a number average molecular weight in terms of standard polystyrene measured by GPC (solvent: chloroform) of 200 to 10,000, preferably 200 to 5,000, and more preferably 500. Is 5,000, and more preferably 1,000 to 4,000 from the viewpoint of optical properties.

The number average molecular weight of the thermoplastic resin is 200.
If it is less than 1, the tear strength of the obtained norbornene-based resin film or retardation film becomes insufficient, and conversely 1
When it exceeds 0000, the moldability (film-forming property) of the norbornene-based resin composition is deteriorated, and the extraction rate of the thermoplastic resin from the obtained norbornene-based resin film with the solvent is slowed.

The thermoplastic resin having such characteristics is not particularly limited, but examples thereof include alicyclic olefins, alicyclic olefin-based oligomers, alicyclic olefin-based polymers, and the like. However, compounds having a cyclohexene ring, a cyclopentene ring, a cyclooctene ring, a norbornene ring or the like in the molecular structure are preferably used. Further, the thermoplastic resin may be a compound having a plurality of olefinic monomer ring structures by another reaction. These thermoplastic resins are preferably saturated by hydrogenation when an unsaturated bond is present in the molecule. Further, these thermoplastic resins may be used alone or in combination of two or more kinds.

The thermoplastic resin can be synthesized from, for example, a cyclopentene-based monomer, a cyclopentadiene-based monomer, a norbornene-based monomer or the like by a metathesis polymerization reaction or a Diels-Alder reaction.

Commercially available products of the above-mentioned thermoplastic resins are not particularly limited, but for example, the product name "Arcon" series manufactured by Arakawa Chemical Industry Co., Ltd., the product name "Polystar" series manufactured by Yasuhara Chemical Co., Ltd. Examples include the "Clearon" series and the product name "Escorets" series manufactured by Tonex.

In the method for producing a retardation film of the present invention, first, a norbornene resin composition containing 1 to 100 parts by weight of the above-mentioned thermoplastic resin is formed into a film with respect to 100 parts by weight of the norbornene resin. A norbornene-based resin film is produced. Then, the norbornene-based resin film is dissolved without dissolving the norbornene-based resin.
The retardation film is formed by immersing the thermoplastic resin in a solvent capable of dissolving it, extracting a part of the thermoplastic resin, drying it if necessary, and stretching it.

By dipping the norbornene-based resin film in the above solvent, the thermoplastic resin existing in the vicinity of both surface layers of the film can be relatively easily extracted, but the thermoplastic resin existing in the vicinity of the core layer of the film. Is not easily extracted. As a result, the norbornene-based resin film includes both surface layers that are rich in norbornene-based resin and have a relatively high Tg, and cores that have a relatively low Tg because the norbornene-based resin and the thermoplastic resin are present in an amount close to the original blending ratio. It is a three-layered film composed of layers.

Next, by stretching the above-mentioned three-layered film, both surface layers rich in norbornene resin and having a relatively high Tg exhibit excellent retardation. on the other hand,
The core layer having a relatively low Tg does not contribute to the development of retardation, but contributes to ensuring the thickness. As a result, the obtained retardation film exhibits an excellent retardation and has a small variation in retardation (unevenness in retardation).

In the above norbornene resin composition,
If the content of the thermoplastic resin is less than 1 part by weight based on 100 parts by weight of the norbornene-based resin, the above effect due to the addition of the thermoplastic resin cannot be sufficiently obtained, and conversely 10
When the amount exceeds 0 parts by weight, the retardation exhibiting property of the norbornene-based resin is offset, and the retardation film obtained does not exhibit a sufficient retardation.

The film-forming method for the norbornene-based resin composition is not particularly limited, and examples thereof include a melt-extrusion film-forming method, a calender film-forming method and a solution cast (casting) film-forming method. Any film forming method may be adopted, but among them, it is preferable to adopt the melt extrusion film forming method because it is excellent in productivity and environmentally symbiotic.

The solvent used in the present invention may be any solvent as long as it can dissolve the thermoplastic resin without dissolving the norbornene resin, and the kind of norbornene resin and thermoplastic resin used. It may be appropriately selected according to The above solvents may be used alone or in combination of two or more depending on the extraction conditions. Furthermore, when the thermoplastic resin is extracted with the above solvent, the temperature of the solvent may be appropriately adjusted according to the desired extraction speed and extraction amount.

The extraction amount of the thermoplastic resin may be appropriately determined according to the level of retardation, thickness, etc. desired to be imparted to the obtained retardation film, and is not particularly limited.
Generally, the residual amount of the thermoplastic resin after being partially extracted is 0.5 to 5 with respect to 100 parts by weight of the norbornene-based resin.
The amount is preferably 0 part by weight, more preferably 1 to 20 parts by weight.

The method for stretching the norbornene resin film after a part of the thermoplastic resin is extracted in the solvent is not particularly limited, but for example, a longitudinal uniaxial stretching method using a roll or a tenter is used. Horizontal uniaxial stretching method,
A sequential biaxial stretching method, a simultaneous biaxial stretching method, and the like using these combinations may be mentioned, and any stretching method may be adopted.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The following examples are given to illustrate the present invention in more detail, but the present invention is not limited to these examples. In addition, "part" in an Example means a "weight part."

Example 1 100 parts of trade name "Zeonor 1600" (manufactured by Zeon Corporation) as a norbornene-based resin, and "ESCOLETS F2" as a thermoplastic resin
28 "(number average molecular weight: 500, manufactured by Tonex) 1
0 parts were blended to prepare a norbornene-based resin composition, and then the norbornene-based resin composition was supplied to a melt extrusion molding machine in which a T-die was arranged in a single-screw melt extruder, and 230
The film was formed at a melting temperature of ° C to prepare a norbornene-based resin film having a thickness of 60 µm. Next, the norbornene-based resin film was immersed in a toluene bath at 60 ° C. for 5 minutes and then dried to obtain a norbornene-based resin film in which a part of “ESCOLETS F228” was extracted. Then, the norbornene-based resin film was longitudinally uniaxially stretched to prepare a retardation film.

(Example 2) 100 parts of a trade name "ARTON D4532G" (manufactured by JRS) as a norbornene-based resin, and 5 parts of 5-norbornene-2-methanol as a thermoplastic resin were dissolved in 14 parts of chloroform. Then, 0.017 part of a ruthenium complex (metathesis polymerization catalyst) represented by the following formula (1) and 1-hexene of 0.
After adding 5 parts and reacting for 24 hours, a norbornene-based oligomer (number average molecular weight: 1100) obtained by performing reprecipitation purification three times in a toluene / methanol mixed solvent system
After preparing 4.2 parts of the norbornene-based resin composition by blending, 4.2 parts of the norbornene-based resin composition was fed to the same melt extrusion molding machine as in Example 1 to form a film at a melting temperature of 260 ° C. Then, a norbornene-based resin film having a thickness of 60 μm was produced. Next, the norbornene-based resin film was immersed in a cyclohexane bath at 40 ° C. for 15 minutes and then dried to obtain a norbornene-based resin film in which a part of the norbornene-based oligomer was extracted. Then, the norbornene-based resin film is longitudinally uniaxially stretched,
A retardation film was produced.

[Chemical 1] (In the formula, Cy represents a cyclohexyl group and t-Bu represents a tertiary butyl group)

(Comparative Example 1) "Zeonor 1600" was used as the norbornene-based resin, and the above norbornene-based resin was supplied to the same melt extrusion molding machine as in Example 1 and 2
The film was formed at a melting temperature of 30 ° C. to prepare a norbornene-based resin film having a thickness of 60 μm. Then, the norbornene-based resin film was longitudinally uniaxially stretched to prepare a retardation film.

(Comparative Example 2) A retardation film was produced in the same manner as in Example 1 except that "ESCOLETS F228" was not extracted with a solvent (toluene).

(Comparative Example 3) Using "Alton D4532G" as the norbornene resin, the above norbornene resin was supplied to the same melt extrusion molding machine as in Example 1 to form a film at a melting temperature of 260 ° C. A norbornene-based resin film having a thickness of 60 μm was produced. Then, the norbornene-based resin film was longitudinally uniaxially stretched to prepare a retardation film.

The performance (retardation, retardation unevenness, thickness unevenness) of the retardation films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was evaluated by the following methods. The results are shown in Table 1.

Phase difference and phase difference unevenness: The phase difference of the phase difference film at 590 nm wavelength light was measured in the width direction by the rotational analyzer method, the full width in the width direction, and the length of 10 cm in the stretching direction was measured at a pitch of 5 mm. And the maximum value of the phase difference unevenness were determined. Thickness unevenness: The thickness of the retardation film was measured with a thickness meter to measure the entire width in the width direction and a length of 10 cm in the stretching direction at a pitch of 5 mm to obtain the maximum value of the thickness unevenness.

[0045]

[Table 1]

[0046]

INDUSTRIAL APPLICABILITY In the method for producing a retardation film of the present invention, a norbornene resin containing a specific amount of a thermoplastic resin having a specific Tg and a specific number average molecular weight with respect to the specific amount of the norbornene resin. A norbornene-based resin film made of the composition is dipped in a specific solvent,
Since a part of the thermoplastic resin is extracted and then stretched, the obtained retardation film exhibits an excellent retardation and a small variation in retardation (unevenness in retardation).

As described above, according to the manufacturing method of the present invention, the phase difference is made uniform with high accuracy, and when the liquid crystal display device is incorporated, excellent display quality is exhibited over almost the entire area. A retardation film can be manufactured efficiently and easily.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 65/00 C08L 65/00 101/00 101/00 G02F 1/13363 G02F 1/13363 // B29K 45: 00 B29K 45:00 B29L 7:00 B29L 7:00 11:00 11:00 F Term (reference) 2H049 BA06 BB42 BC03 BC09 BC22 2H091 FA11X FA11Z FB02 FB12 FC01 FC07 FC21 LA12 LA16 4F073 AA14 BA34 BB01 EA01 EA03 4F210AA12 AG01 QC02 QC03 QC06 QC07 QG01 QG11 QG18 4J002 BK00W BK00X CE00W CE00X GA01 GS00

Claims (2)

[Claims] 1. A thermoplastic norbornene-based resin that is compatible with 100 parts by weight of a thermoplastic norbornene resin, has a glass transition temperature lower than that, and has a number average molecular weight of 200 to 100.
The thermoplastic norbornene-based resin film obtained by forming the thermoplastic norbornene-based resin composition containing 1 to 100 parts by weight of the thermoplastic resin of No. 00 is a thermoplastic resin without dissolving the thermoplastic norbornene-based resin. A method for producing a retardation film, comprising dipping in a solvent capable of dissolving, extracting a part of the thermoplastic resin, and then stretching. 2. The method for producing a retardation film according to claim 1, wherein the method for forming the thermoplastic norbornene resin composition is a melt extrusion film forming method.