JP2002172675A - Polymeric sheet, method of manufacturing polymeric sheet, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a polymeric sheet excellent in heat resistance and the smoothness of a sheet surface and having few projections. SOLUTION: In this method, a polyether sulfone having a glass transition point of 150 deg.C or above, a number-average molecular weight (Mn) of 11,000-25,000 and a molecular-weight distribution (Mw/Mn) of 3.0 or below is melt-extruded by a T-die or a coathanger die and thereby the polymeric sheet of a thickness 70-1,000 μm or below is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polymer sheet having excellent heat resistance, excellent sheet surface smoothness, and having few projections. The present invention further relates to a method for producing an optical sheet such as a liquid crystal display device. The present invention relates to a suitable polymer sheet and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Conventionally, a glass substrate has been used as a transparent electrode substrate for a liquid crystal display device. However, a liquid crystal display device using a glass substrate has the drawback that it is difficult to reduce the thickness of the liquid crystal display device itself because the glass substrate itself is thick, and it is difficult to reduce the weight. There was a problem in point.

As a method for improving the disadvantages of the glass substrate liquid crystal display element, a liquid crystal panel is manufactured by using a plastic film to reduce the weight of the liquid crystal panel,
Improvement of impact resistance is being studied.

[0004] As a liquid crystal cell using a thermoplastic resin sheet (polymer sheet) is put into practical use, the display area becomes larger, and the electrodes are kept at uniform intervals. Is required. In some cases, the thickness of the base material has exceeded 300 μm from the initial thickness of 100 μm, and development using a polymer sheet has been conducted, but the contrast of the liquid crystal display due to flat retardation and the surface smoothness are insufficient. Therefore, problems of display defects, peeling of the liquid crystal sealing portion due to warpage, and deformation of the element have been issues, and an immediate improvement is desired.

[0005] Regarding the surface smoothness, the melt extrusion method using a T die or a coat hanger die depends on the shear stress and stagnation in the flow path through which the thermoplastic polymer passes, and further, the precision of the die surface and lip. Streaks called die lines, which are supposed to occur, are formed on the sheet surface, and the surface smoothness is reduced. As a means to improve surface smoothness,
A solvent casting method is known in which a thermoplastic polymer is dissolved in a solvent, and a film or a metal belt is coated and dried. However, productivity and a residual solvent in the sheet when the thickness of the sheet increases become a problem. .

[0006] In addition, an injection molding method in which a thermoplastic polymer is sealed in a mold whose surface is finished with high precision and molded can also control retardation as is known for CD disks.
Although productivity is not a problem, it is considered a promising candidate. However, in the injection molding method, a sheet having a thickness on the order of several millimeters is the limit, and cannot be applied to a thickness of several hundred micrometers.

Further, it has been found that an increase in projections caused by a high molecular weight gelled product generated in a melt extrusion film forming process is a serious drawback. For example, in a liquid crystal display device using a polymer sheet for a substrate, there is a problem that a point defect of display is caused by a projection on the substrate surface.

[0008] The high molecular weight gelled product is produced during or after the raw material stage of polymerization and various thermal processing steps. The gelled material generated in this raw material stage can be removed with a mesh or the like at the time of heat melting, but it is in a high temperature state even after passing through the mesh, and during a short time until it is cooled,
It was inevitable that the high molecular compounds in the resin reacted with each other to produce a high molecular weight gel. This tendency has the property of becoming more pronounced as the sheet thickness increases, and has become a serious drawback as the display screen becomes larger.

Thus, the sheet surface is excellent in smoothness,
In addition, it was difficult with the state of the art to produce a polymer sheet having few projections.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polymer sheet having excellent heat resistance, excellent sheet surface smoothness, and having few projections. An object of the present invention is to provide a polymer sheet that can be suitably used as an optical sheet for a panel and a liquid crystal display device using the same.

[0011]

According to the present invention, a glass transition point is 150 ° C. or higher, and a number average molecular weight (M _n ) is 1
A polyethersulfone having a molecular weight distribution ( _Mw / _Mn ) of not more than 3.0 having a molecular weight distribution ( _Mw / _Mn ) of not more than 3.0 is extruded with a T die or a coat hanger die, and has a thickness of 70 μm.
A method for producing a polymer sheet, comprising producing a polymer sheet having a thickness of 1000 μm or less. In the method for producing a polymer sheet, the number average molecular weight ( _Mn ) of polyether sulfone as a raw material resin is 15,000 to 2
2000, and the molecular weight distribution (M _w / M _n ) is preferably 2.0 or less. Polyethersulfone is 4,
It is preferably obtained by polycondensing 4'-dichlorodiphenylsulfone and 4,4'-dihydroxydifelsulfone. Further, the present invention is a polymer sheet manufactured by the above manufacturing method. Furthermore, the present invention is a liquid crystal display device assembled using the above polymer sheet.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyethersulfone used in the present invention has various structures and is not particularly limited, but the glass transition point (Tg) must be 150 ° C. or higher. And preferably at least 180 ° C. and 40
0 ° C. or less. If the Tg is lower than 150 ° C., the polymer sheet may be softened by the heat treatment in the liquid crystal assembling step, for example, at the temperature of firing the alignment film and curing the seal, thereby causing a problem.

The polyethersulfone used as a raw material resin in the present invention is preferably obtained by polycondensation of 4,4'-dichlorodiphenylsulfone and 4,4'-dihydroxydifulfone. . The molecular weight, molecular weight distribution, and OH terminal group content of the obtained polyethersulfone can be controlled by adjusting the mixing ratio of the starting monomers and the decondensing agent, reaction conditions, and the like.

The polyethersulfone used in the present invention has a number average molecular weight ( _Mn ) of 11,000 to 25,000.
It is necessary that the molecular weight distribution (M _w / M _n ) is 3.0 or less. Preferably, the number average molecular weight ( _Mn ) is 15
2,000 to 22,000, and the molecular weight distribution (M _w / M _n ) is 1.
It is 0 or more and 2.0 or less. If the number average molecular weight ( _Mn ) of the polyether sulfone is less than 11,000, the solvent resistance is poor, and cracks and wrinkles may occur when various solvents are used in the liquid crystal display cell assembly process. On the other hand, when the number average molecular weight (M _n ) exceeds 25,000, a gel is easily generated in the melt extrusion step, which causes a projection on the substrate surface. On the other hand, if the molecular weight distribution ( _Mw / _Mn ) exceeds 3.0, unevenness occurs in the sheet during melt-extrusion, and a die line is likely to be generated on the sheet surface.

Here, the number average molecular weight (M _n ) and the weight average molecular weight (M _w ) are numerical values measured by GPC and converted into the molecular weight of polystyrene. GPC measurement conditions are as follows:
It is as follows. <Sample preparation> A solution prepared by dissolving 40 mg of a sample with 20 ml of an eluent was used as a measurement solution. <GPC measurement conditions> Column TSKgel GMHHR-H 2 eluents DMF (dimethylformamide) + 10 mM LiBr flow rate 1.0 ml / min Detector MALLS (multi-angle light scattering photometer) + RI (differential refractometer) Injection volume 100 μl

The polymer sheet produced by the present invention has a thickness of 70 μm or more and 1000 μm or less, preferably 10 μm or less.
It is not less than 0 μm and not more than 600 μm. If the thickness of the polymer sheet is less than 70 μm, it is difficult to maintain the cell gap of the liquid crystal, and particularly in the case of a large-area liquid crystal display element, the cell gap cannot be maintained. When the thickness exceeds 1000 μm, the liquid crystal display causes a display defect called a double image, and the thickness of the liquid crystal display element is increased, which is not preferable in function.

In the method for producing a polymer sheet of the present invention, polyether sulfone is melt-extruded with a T-die or a coat hanger die to produce a polymer sheet.
The heat-melted polyether sulfone is brought into close contact with a metal belt, a cooling roll, or the like, formed into a sheet, cooled, and wound up. In order to bring the polymer sheet melt-extruded from the die into close contact with the metal belt, air controlled at a temperature similar to that of the metal belt may be blown, or the polymer sheet may be brought into close contact by charging and fixing.

The polymer sheet produced by the method of the present invention has a diameter of 0.5 mm per 0.1 m ^{2 of} the polymer sheet.
The number of the projections is usually two or less, and the number of the projections is extremely small. The polymer sheet of the present invention thus produced is excellent in heat resistance, excellent in sheet surface smoothness, and has few projections, so that it can be suitably used as an optical sheet for a liquid crystal display panel. By manufacturing a liquid crystal display element using a molecular sheet, a flat liquid crystal display without display defects can be obtained.

[0019]

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

[A] The physical properties of the polymer sheet and the physical properties of the production apparatus were measured by the following methods. (1) Thickness of polymer sheet Use a contact-type dial gauge to measure 20
It was measured at mm intervals. The average value was defined as the thickness of the polymer sheet. (2) Maximum surface roughness of polymer sheet (Rmax) Contact-type precision step meter (TENCOR INSTRUME)
The maximum value of the unevenness obtained by measuring the entire width of the polymer sheet with a scanning width of 2 mm in the width direction of the polymer sheet using AIPHA-STEP200 manufactured by NTS. (3) Retardation of Polymer Sheet The retardation at a wavelength of 550 nm was measured using a polarizing microscope BH2 manufactured by Olympus Optical Co., Ltd. and a Berek compensator. (4) Warpage of the polymer sheet 300 mm long in the flow direction of the polymer sheet and 3 in the width direction
The height of the polymer sheet, which is the largest away from the surface of the surface plate, when the square sample cut to a length of 00 mm is placed with the front side of the polymer sheet up and down with respect to the surface plate, The maximum value was measured as the warpage of the sheet. (5) Maximum surface roughness of the metal belt (Rmax) Contact type surface roughness meter (Surf Test 3 manufactured by Mitutoyo Corporation)
01) is the maximum value of the unevenness when the entire width is measured at a cutoff length of 0.8 mm in the width direction of the metal belt. (6) Maximum surface roughness of die (Rmax) Contact surface roughness meter (Surf Test 3 manufactured by Mitutoyo Corporation)
01), the cutoff length 0.8 in the width direction of the die.
The maximum value of unevenness when measuring the entire width in mm.

[B] As a raw material resin, polyethersulfone (PES) obtained by polycondensation of 4,4'-dichlorodiphenylsulfone and 4,4'-dihydroxydifrusulfone was used. The number average molecular weight, weight average molecular weight, and molecular weight distribution of polyethersulfone are as follows. In addition, Tg is 226 degreeC in all cases. (1) PES-1 _Mn : 19000, _Mw : 30000, _Mw / _Mn : 1.5
8 (2) PES-2 _Mn : 22000, _Mw : 69000, _Mw / _Mn : 3.1
3 (3) PES-3 _Mn : 10000, _Mw : 26000, _Mw / _Mn : 2.6
0 (4) PES-4 _Mn : 28000, _Mw : 92000, _Mw / _Mn : 3.2
8

Example 1 A die having a maximum surface roughness (Rmax) of 0.4 μm and a lip gap of 3 mm using PES-1 as a raw material resin was used, and a maximum surface roughness (Rm) was obtained.
ax) was 0.1 μm, and the polymer sheet extruded from the die was formed into a cooled sheet using a metal belt having a contact time of 22 seconds with no curvature in the flow direction.
The temperature (V1) of the first part in contact with the metal belt is 25
0 ° C., the temperature (V2) of the metal belt in the portion having no curvature with respect to the flow direction of the polymer sheet is 210 ° C., and the temperature (V3) of the metal belt in the portion where the cooled polymer sheet is separated from the metal belt is The temperature was 110 ° C., and the surface of the polymer sheet opposite to the surface in contact with the metal belt was set to the same temperature as the sheet surface temperature on the metal belt side by an infrared heater. As a result, the thickness was 400 μm, the retardation in the plane was 15 nm, and the maximum surface roughness (Rmax) of the polymer sheet in contact with the metal belt surface was obtained.
Was 0.06 μm, and a 300 mm square polymer sheet having a maximum warpage of 2 mm was obtained. 0.1
When 10 sheets of m ² were visually inspected, there were no die lines, and all the protrusions having a diameter of 0.5 mm or more were 2 or less, and the average was 1.2.

Example 2 400 μm obtained in Example 1
m polymer sheet, molecular weight 1540, melting point 7
Epoxy acrylate prepolymer at 0 ° C (Showa Polymer
VR-60), 100 parts by weight, butyl acetate 40
0 parts by weight, 100 parts by weight of cellosolve acetate, and
2 parts by weight of benzoin ethyl ether was stirred at 50 ° C.
A gravure roll coater that dissolves into a uniform solution
And heated at 80 ° C. for 10 minutes to remove the solvent.
30 seconds at a distance of 15 cm with a high-pressure mercury lamp of 0 w / cm
The resin is cured by irradiation for a while, and an organic layer having a thickness of 0.5 μm is
Formed on the surface. Next, a DC magnetron is placed on this sheet.
Initial vacuum degree 3 × 10^-FourPull to Pa, oxygen / al
Introduce a gas mixture of gon gas (oxygen content 9vol%), 3
× 10 ^-1An inorganic layer is formed under the condition of Pa
Thick SiO_TwoI got The oxygen barrier property of this inorganic film is
1cc / 24hr · m measured by the Con method^Twoso
Yes, the surface resistivity was measured to be 8.1 × 10¹²In Ω
there were. Next, as a transparent conductive film, DC magnetro
Initial vacuum degree 3 × 10 ^-FourPull to Pa, oxygen / a
Introducing a mixed gas of Lugon gas (oxygen content 4vol%)
And 1 × 10^-1The film was formed under the condition of Pa
In in which the atomic ratio of (In + Sn) is 0.98_TwoO_Three, S
nO_TwoWas obtained. As a result of the measurement, the film thickness
1600 °, specific resistance 4 × 10^-FourΩ · cm. Success
After film formation, apply and develop resist and use salt as an etchant.
Acid (1 mol / l), pattern etchin at 40 ℃
3 inches (7.5 cm) diagonal, L / S (conductor
(Line width / conductor line spacing) = 150/50 μm active mask
A pattern for tricks was formed. After pattern formation,
Coating film was applied and baked at 150 ° C for 2 hours.
Thereafter, a rubbing treatment was performed. After rubbing, spacer
Spray, apply sealant, and seal at 150 ° C
Then, a cell was formed, and a liquid crystal was injected. Contrast polarizing plate
And the lighting test was performed.
At this time, no display defects due to sheet protrusions were
A good indication of the trust was shown.

Comparative Example 1 A polymer sheet was produced in the same manner as in Example 1 except that PES-2 was used as a raw material resin, and a die line was generated on the sheet surface during melt extrusion.

Comparative Example 2 A polymer sheet was produced in the same manner as in Example 1 except that PES-3 was used as a raw material resin. When 10 sheets of 0.1 m ² sheet were visually inspected, there were no die lines, and all the protrusions having a diameter of 0.5 mm or more were 2 or less, and the average was 0.9. Using this sheet, an epoxy acrylate prepolymer was applied in the same manner as in Example 2 and heated at 80 ° C. for 10 minutes to remove the solvent. As a result, cracks occurred in the sheet.

Comparative Example 3 A polymer sheet was produced in the same manner as in Example 1 except that PES-4 was used as a raw material resin. Die lines were generated on the sheet surface during melt extrusion. As a result of visually inspecting ten sheets of 0.1 m ² , all the protrusions having a diameter of 0.5 mm or more were more than two, and the average was 8.9. When a liquid crystal cell was prepared using this sheet in the same manner as in Example 2, a display defect due to a projection on the sheet was confirmed.

[0027]

According to the present invention, a polymer sheet having excellent surface smoothness and having few projections was obtained. Further, when the polymer sheet obtained by the present invention was mounted on a liquid crystal display panel as a transparent electrode sheet for a flexible liquid crystal display element, a high definition display without display unevenness was exhibited.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 11:00 B29L 11:00 C08L 81:06 C08L 81:06 (72) Inventor: Dai Takahashi Shinagawa-ku, Tokyo 2-5-8 Higashishinagawa Sumitomo Bakelite Co., Ltd. (72) Inventor Toshimasa Eguchi 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. (72) Inventor Kunihisa Sato Kasuga, Konohana-ku, Osaka-shi No. 3-98 No. 1-98 Sumitomo Chemical Co., Ltd. F-term (reference) 2H090 JB03 LA01 4F071 AA64 AA81 AA86 AF45 AH12 BA01 BB06 BC01 BC12 4F207 AA34 AE10 AG01 AH73 AJ02 AR12 AR20 KA01 KA17 KK64 KK74 KL76 KL84 A005

Claims (5)

[Claims] (1) a glass transition point of 150 ° C. or more;
Number average molecular weight (M _n) Is 11000-25000,
Molecular weight distribution (M_w/ M_n) Is 3.0 or less
Lusulfone is melt-pushed with T-die or coat hanger die
Take out, and the thickness is 70 μm or more and 1000 μm or less.
Manufacturing a polymer sheet, characterized by manufacturing a child sheet
Construction method. 2. The polyethersulfone has a number average molecular weight ( _Mn ) of 15,000 to 22,000 and a molecular weight distribution ( _Mw).
/ _Mn ) is 2.0 or less, The manufacturing method of the polymer sheet of Claim 1. 3. The polymer sheet according to claim 1, wherein the polyethersulfone is obtained by polycondensing 4,4′-dichlorodiphenylsulfone and 4,4′-dihydroxydifelsulfone. Production method. 4. A polymer sheet produced by the production method according to claim 1. 5. A liquid crystal display device assembled using the polymer sheet according to claim 4.