JP2001164000A - Method of producing norbornene based resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of allowing fine ruggedness of a film or streaks of the film which are parallel to the stretching direction to cause phase difference nonuniformity in the film after stretching when a norbornene based resin film produced by solution casting is uniaxially stretched in the lengthwise direction to produce a phase difference film. SOLUTION: The method of producing a norbonene based resin film by solution casting comprises passing the obtained film between a pair of nip rolls whose clearance is set at 95-100% average thickness of the film in a drying oven whose temperature is set in the range of from the initiation temperature of deforming the film to not higher than the initiation temperature of deforming the film plus 100 deg.C at the last stage of the drying step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a norbornene resin film by a solution casting method. More specifically, the present invention relates to a method for producing a transparent optical norbornene resin film that can be suitably used as a retardation film of a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In a reflection type liquid crystal display device developed in recent years, a retardation film made of a material having a low wavelength dispersion is demanded in consideration of the wavelength dispersion of a liquid crystal used in the device.

[0003] Norbornene-based resins are characterized by having a smaller birefringence when stress is applied and a smaller wavelength dispersion characteristic of the refractive index than engineering plastics such as polycarbonate and polysulfone and triacetyl cellulose. Therefore, it is attracting attention as an optical film material suitable for a reflection type liquid crystal display device.

It has been disclosed that a norbornene-based resin film can be formed by a solution casting method.
No., published in Japanese Unexamined Patent Publication No.

[0005]

However, when a retardation film is manufactured by longitudinally and uniaxially stretching a norbornene-based resin film manufactured by a solution casting method, fine unevenness of the film or stripes parallel to the stretching direction are generated after stretching. There was a problem that retardation unevenness was caused in the film.

The present inventor has conducted intensive studies to solve the above-mentioned problems. As a result, fine irregularities or streaks parallel to the stretching direction of the norbornene-based resin cast film are promoted at the time of stretching, causing phase difference unevenness. Found that it was possible to solve the problem by passing a cast film between nip rolls under specific conditions, and completed the present invention.

An object of the present invention is to provide a method for producing a transparent optical norbornene resin film which can prevent a local change in retardation when used as a retardation film.

[0008]

That is, the present invention relates to a method for producing a norbornene-based resin film by a solution casting method, wherein at the end of the drying step, a temperature not lower than the film deformation start temperature and not higher than the deformation start temperature + 100 ° C. A method for producing a norbornene-based resin film, characterized in that the obtained film is passed between a pair of nip rolls having a clearance set to 95 to 100% of the average film thickness in a drying furnace set in a range. Things.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail.

[0010] The present invention is to prevent the retardation unevenness occurring in the transparent norbornene resin retardation film by improving the thickness accuracy. The thickness accuracy of the cast film largely depends on the film formation, but this is related to the viscosity of the solution and the compatibility of the coater, or various conditions such as drying conditions and casting base materials. Although it is possible to increase the film thickness accuracy by reducing these conditions, the present invention is excellent in that the thickness accuracy can be more easily increased and the occurrence of phase difference unevenness can be prevented.

In the present invention, the norbornene-based resin film is formed by a solution casting method, and the solvent used for adjusting the solution and the solution casting method can be used by a conventionally known means as it is.

In the solution casting method, the norbornene-based resin used in the resin solution is a thermoplastic saturated norbornene-based resin, and is, for example, a known one disclosed in JP-A-3-14882 and JP-A-3-122137. It is a resin, and a conventionally known thermoplastic saturated norbornene-based resin can be suitably used.

Examples of monomers constituting the thermoplastic saturated norbornene resin include, for example, norbornene, 5-
Methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5
-Cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-
Norbornene, 5-phenyl-5-methyl-2-norbornene, ethylene-tetracyclododecene copolymer, 6
-Methyl-1,4: 5,8-dimethano-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Ethyl-1,4: 5,8-dimethano-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Ethyl-1,4: 5,8-ethylidene-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Chloro-1,4: 5,8-dimethano-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Cyano-1,4: 5,8-dimetano-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Pyridyl-1,4: 5,8-dimetano-1,4,4a,
5,6,7,8,8a-octahydronaphthalene, 6-
Methoxycarbonyl-1,4: 5,8-dimetano-1,
4,4a, 5,6,7,8,8a-octahydronaphthalene, 1,4-dimethano-1,4,4a, 4b, 5
8,8a, 9a-octahydrofluorene, 5,8-methano-1,2,3,4,4a, 5,8,8a-octahydro2.3-cyclopentadienonenaphthalene, 4,
9: 5,8-Dimethano-3a, 4,4a, 5,8,8
a, 9,9a-octahydro-1H-benzoindene,
4,11: 5,10: 6,9-trimethano-3a, 4,4
4a, 5, 5a, 6, 9, 9a, 10, 10a, 11,
11a-dodecahydro-1H-cyclopentaanthracene and the like.

The thermoplastic saturated norbornene-based resin is obtained, for example, by subjecting (a) a ring-opening polymer or a ring-opening copolymer of a norbornene-based monomer to modification such as addition of maleic acid or cyclopentadiene, if necessary. Hydrogenated resin, (b) a resin obtained by addition polymerization of a norbornene-based monomer, (c) a resin obtained by addition polymerization of a norbornene-based monomer and an olefin-based monomer such as ethylene or α-olefin, and (d) a norbornene-based monomer. Resins obtained by addition polymerization with a cyclic olefin monomer such as cyclopentene, cyclooctene, 5,6-dihydrodicyclopentadiene, and modified products of these resins.

In the above polymerization, for example, I
r, Os, Ru trichloride hydrate, MoC_l5, W
C_l6, ReCl_Five, (C_TwoH_Five)_ThreeAl, (C_TwoH_Five)_ThreeAl
/ TiCl_Four, (Π-C_FourH₇)_FourMo / TiCl_Four, (Π
-C_FourH₇)_FourW / TiCl_Four, (Π-C _ThreeH_Five)_ThreeCr / W
Cl₆And the like, using a conventional method.

As the above-mentioned thermoplastic saturated norbornene resin, trade names "ZEONOR", "Z
"EONEX", product name "ART" from JSR Corporation
ON ", which is marketed by Mitsui Petrochemical Company as" APEL ".

When the number average molecular weight of the thermoplastic saturated norbornene resin decreases, the moisture resistance decreases and the moisture permeability increases, and as the number average molecular weight increases, the film formability decreases. Therefore, the gel permeation chromatograph using a toluene solvent is used. When measured, it is preferably 25,000 to 100,000, and more preferably 30,000 to 80,000.

The solvent for dissolving the norbornene resin may have a boiling point of 100 ° C. or higher, preferably 120 ° C.
The above are preferred, for example, toluene, xylene,
There are ethylbenzene, trimethylbenzene, chlorobenzene and the like. Among them, toluene, ethylbenzene and chlorobenzene are preferred. The concentration of the resin solution is 10 ~
50% by weight is preferred.

The solution casting method is not particularly limited, and a general solution casting method used for producing an optical film such as a polycarbonate resin film can be used. Specifically, a bar coater, a roll coater, a die coater, Using a comma coater or the like, the resin solution can be cast on a heat-resistant material such as polyethylene terephthalate or a flat plate or a roll such as a steel belt as a support.

The drying step after the casting of the resin solution is not particularly limited, and a conventionally known method can be used. However, the drying is preferably performed in several steps, and the drying in one step is performed at a relatively low temperature of 100 ° C. or less. And drying at a temperature at which foaming due to rapid evaporation of the solvent does not occur.

In the present invention, in the last stage of the drying, a zone is provided in the drying furnace where the drying temperature is from the deformation start temperature of the resin film to the deformation start temperature + 100 ° C. In this zone, the final thickness of the film is 95%. Pass between nip rolls with clearance adjusted to ~ 100%. In the present invention, the term "deformation start temperature" refers to the elongation measured by elongation at a temperature of 5 ° C./min while applying a constant load of 10 g with a tensile tester equipped with a heating furnace in which the distance between chucks is set to 50 mm.
The temperature exceeds. The deformation start temperature can be appropriately adjusted depending on the content, viscosity, etc. of the solvent contained in the film. When the temperature is higher than the deformation starting temperature and exceeds 100 ° C., the resin film is easily deformed, and the width, thickness, and the like deviate from the settings. In addition, the releasability from the nip roll is deteriorated, which may cause deformation of the film and decrease the thickness accuracy.

It is preferable that the surface of the nip roll is subjected to a surface treatment having a high releasability from the resin. For example, there are hard chrome plating and tungsten carbide treatment, but the treatment method is not limited, and a treatment method suitable for resin characteristics may be used.

As a method of heating the drying furnace in which the nip roll is installed, a hot air heating method is preferable from the viewpoint of temperature uniformity. However, since the heating is performed in a temperature range where the film can be easily deformed, the wind speed and the wind direction are minimized. It is necessary to set so as not to cause unnecessary deformation. For example, there is a counter flow method in which a wind parallel to the running direction of the film is passed. Alternatively, a method using both a hot air heating method and a far infrared heating or infrared heating method can be used.

The film passed through the nip roll under the above conditions has a high thickness accuracy and can be suitably used as a retardation film having no retardation unevenness by stretching.

[0025]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

Example 1 Using a norbornene resin "ZEONEX" manufactured by Zeon Corporation and having a resin concentration of 4
A 0% by weight toluene solution was prepared. This was dried on a PET film using a comma coater to a dry thickness of 80μ.
m. 100 ° C, 120 ° C,
It was dried through a drying zone consisting of three zones at 140 ° C. At this time, the line speed is 1 m / min, and the residence time in each zone is 5 minutes. A ZEONEX film was cut into a width of 25 mm, a sample was set with a tensile tester equipped with a heating furnace with a distance between chucks of 50 mm, a constant load of 10 g was applied, and the temperature was raised at 5 ° C./min. When the temperature exceeding the temperature (deformation start temperature) was measured, the deformation start temperature was 62 ° C. The thickness was 79 μm. Next, PE
ZEONEX film peeled from T film
Drying was performed by passing through a drying zone of 0 ° C. and 150 ° C. at a line speed of 1 m / min. The residence time in each drying zone is 25 minutes. The drying zone at 150 ° C. was provided with a pair of nip rolls whose clearance was adjusted to 74 μm. 7
An optical transparent norbornene resin film having a thickness of 5.4 μm was obtained.

Example 2 A toluene solution having a resin concentration of 30% by weight was prepared using a norbornene resin "ARTON" manufactured by JSR Corporation. This was cast on a PET film using a comma coater so that the dry thickness was 80 μm. 100 ° C, 120 ° C, 140
It dried through the drying zone which consists of three zones of ° C.
At this time, the line speed is 1 m / min, and the residence time in each zone is 5 minutes. The ARTON film is cut into 25 mm width, and the distance between the chucks is set to 50 using a tensile tester equipped with a heating furnace.
mm, the sample was set, a constant load of 10 g was applied, and the temperature at which the elongation exceeded 1% (deformation start temperature) was measured while raising the temperature at 5 ° C./min.
° C. The thickness was 80 μm. Next, the ARTON film peeled from the PET film was heated at 125 ° C. for 1 hour.
Drying was performed at 50 ° C. at a line speed of 1 m / min. The residence time in each drying zone is 25 minutes. 150
A pair of nip rolls whose clearance was adjusted to 76 µm was provided in the drying zone at ° C. A 76.1 μm thick transparent optical norbornene resin film was obtained.

Comparative Example 1 A film was prepared in the same manner as in Example 1 except that the nip roll clearance was fully opened (10 mm) to obtain a 75.1 μm thick transparent optical norbornene resin film.

Comparative Example 2 A film was prepared in the same manner as in Example 2 except that the nip roll clearance was fully opened (10 mm), to obtain a transparent optical norbornene resin film having a thickness of 76 μm.

"Evaluation of Film" (1) Measurement of Thickness The thickness was measured at 1 mm intervals from the edge of the film, and the results are shown in Table 1.

[0031]

[Table 1] Thickness variation ... maximum thickness-minimum thickness Thickness unevenness ... maximum thickness difference at a point 5mm away

(2) Unevenness of retardation The films of Examples and Comparative Examples were stretched, and the uniformity of retardation was evaluated. The results are shown in Table 2. Stretching conditions Example 1, Comparative example 1: preheating zone / stretching zone / magnification
120 ° C / 130 ° C / 175% Example 2, Comparative Example 2: Preheating zone / stretching zone / magnification
140 ° C./150° C./175% retardation measurement Retardation at 550 nm was measured at 1 mm intervals from the edge of the film.

[0033]

[Table 2] Phase difference variance: Maximum phase difference value-Minimum phase difference value Phase difference unevenness: Maximum value of the difference in phase difference value at a point separated by 5 mm Color spot observation: Transmission of a polarizing plate between a pair of polarizing plates having a pair of transmission axes parallel to each other The axis and the stretching axis of the stretched film were arranged at about 45 degrees, and this was placed on a diffusion light source and observed. At this time,
A sample in which no color spots on the streaks could be confirmed was rated as “○”, and a sample in which color spots were confirmed was rated as “x”.

[0034]

The norbornene-based resin film obtained by the present invention has excellent thickness uniformity and can reduce local change in retardation when used as a retardation film.

Claims (1)

[Claims] In a method for producing a norbornene-based resin film by a solution casting method, at the end of a drying step, the temperature is equal to or higher than the film deformation start temperature and the deformation start temperature is +100.
A norbornene-based resin film production characterized in that the obtained film is passed through a pair of nip rolls having a clearance set to 95 to 100% of the average film thickness in a drying furnace set to a temperature range of not more than ℃. Method.