JP3533101B2 - Method for producing thermoplastic polymer sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic polymer sheet and a method for producing the same. The thermoplastic polymer sheet of the present invention is excellent in thickness accuracy and has little sheet warpage. INDUSTRIAL APPLICABILITY The thermoplastic polymer sheet of the present invention is suitable for applications such as spacers that require high thickness accuracy and optical sheets that require a display function. For example, spacers for polishing, high precision motor parts It is suitable as a sliding spacer, a transparent sheet for display devices, and the like.

[0002]

2. Description of the Related Art Generally, a thermoplastic polymer sheet produced by a melt extrusion method cannot obtain sufficient thickness accuracy,
Moreover, curling occurs, and the reliability is poor as a spacer used for maintaining a highly accurate gap.

For this reason, a metal plate made of aluminum, copper or the like is also used as a spacer for maintaining a high precision gap. As for a Si wafer polishing spacer for semiconductor use, as in the case of a Si wafer, a metal spacer is polished, and the metal powder becomes a trace impurity when forming a pattern circuit in a later step, which causes a short circuit between circuits.

Further, a glass substrate has been conventionally used for an optical sheet such as a transparent electrode substrate for a liquid crystal display device. In such a liquid crystal display element, it is difficult to reduce the thickness and weight of the liquid crystal display element because the glass substrate itself is thick. Moreover, sufficient properties have not been obtained in terms of flexibility and impact resistance.

In order to overcome the drawbacks of the conventional glass substrate liquid crystal display device, it has been proposed to manufacture a liquid crystal panel using a plastic film. For example, JP-A-53-68099 and JP-A-54-126559.
The publication discloses a technique for continuously producing a liquid crystal display element panel in which a conductive metal oxide substance is vapor-deposited on a long polyester film instead of a glass substrate, but sufficient optical characteristics can be obtained. Not not. Further, such a sheet has poor thickness accuracy as an optical sheet, and die lines are formed on the film, so that it cannot be practically used as a display sheet.

In order to obtain a thermoplastic resin sheet having excellent properties that can be used for optical applications, an increase in retardation of the sheet due to the molecular orientation that occurs in the melt extrusion film forming process becomes a problem. For example, TN (Twist
ed Nematic) type liquid crystal display device, the incident light linearly polarized by the polarizing plate becomes elliptically polarized light that is partially different from the birefringence of the transparent electrode sheet and the deviation within the sheet surface, resulting in lower contrast and uneven display. Cause

Further, conventionally, in the case of performing melt extrusion using a T die or a coat hanger die, in order to improve the thickness accuracy, it is necessary to reduce the variation in the pressure at the die outlet due to shear stress and retention in the flow path of the thermoplastic polymer. , Or
Improvements in the precision of the surface of the die and lips that cause uneven lines called die lines, and methods of providing guide rolls have been adopted, but they have not been solved yet.

As a method for producing a polymer sheet having good thickness accuracy, a solvent casting method is known in which a thermoplastic polymer is dissolved in a solvent, coated on a film or a metal belt, and dried, but a thick sheet is produced. Since the property is low, the residual solvent in the sheet is also a problem.

Further, as another method, there is an injection molding method in which a thermoplastic polymer is enclosed in a mold whose dimensions are finished with high precision and the molding is performed. Although such a method is used for molding a CD disk and has sufficient productivity, a sheet having a thickness of several mm is the limit in the injection molding method, and a more accurate thickness accuracy of several hundred μm can be obtained. Can not.

Further, there is also known a method of performing post-processing in order to improve the curl resistance of the sheet. For example, a sheet whose surface is finished with high precision is used to press a sheet at a certain interval, but such a method has low productivity and is not suitable for mass production. Further, the method of removing the warp of the sheet by using the cooling roll is not economical because it is necessary to make the cooling roll along the sheet extremely large.

Further, even when the polymer sheet is cooled and solidified on a flat surface (without curvature), the sheet warps easily. As described above, it is very difficult to manufacture a thermoplastic polymer sheet having excellent thickness accuracy and a small warp of the sheet.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoplastic polymer sheet which is excellent in thickness accuracy, has no die line, and has little sheet warpage, and a method for producing the same.

[0013]

[Means for Solving the Problems] The inventors of the present invention have conducted various studies on the conventional method for producing a thermoplastic polymer sheet, and found that the temperature of the molten resin from the die to the cooling step is strictly controlled. The present invention has been completed based on the knowledge that a product having extremely excellent dimensional accuracy and no curl can be obtained.

[0014] The present invention is melt-extruded a plastic polymer through a T-die or coat hanger die into a sheet, Li
Touch the chill roll with the molten sheet that has separated from the
It is a method of manufacturing a sheet that is solidified by a cooling process.
Moves the sheet from the lip tip to the cooling roll.
The space temperature management, there is provided a method for producing the molten sheet of the front and back side with a thermoplastic polymer sheet surface temperature difference you wherein the movement of Serco while maintaining within 15 ℃ of .

The sheet obtained in the present invention is preferably
Is a thermoplastic polymer having a glass transition temperature of 150 ° C or higher.
Sheet thickness 150 to 1000 μm, in-plane thickness of sheet
Tolerance ( Rmax ) 20 μm or less, roughness of sheet surface 0 .
1 μm or less and flat retardation of sheet 2
It is 0 nm or less.

[0016]

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an unexpectedly uniform sheet was obtained by keeping the temperature distribution on the sheet surface between the tip of the die slip and the cooling roll as small as possible. The die lip tip zone of the usual melt extrusion method is heated by radiant heat, and a provisional means is provided so that a non-uniform temperature distribution does not occur in the molten sheet. However, the temperature of the polymer sheet decreases due to heat dissipation using air as a medium, and the front and back sides of the sheet surface,
A non-uniform temperature distribution occurs at the left and right positions in the width direction of the sheet. Furthermore, the molecular orientation is completely solidified by contact with the cooled portion.

In the method of the present invention, the section from the tip of the lip to the cooling roll is sufficiently insulated along the flow of the sheet to perform strict temperature control. For example, a method of controlling the temperature by shutting off the outside air with a metal plate or a heat insulating material until the film melt-extruded from the die touches the cooling roll, or by installing a heater or the like to forcibly control the temperature. Examples include control and management methods. In addition, a method of installing a baffle plate to eliminate the temperature change due to the air flow that occurs near the cooling roll or the die, and further, controlling the atmospheric temperature in the room so as not to generate the air flow, but from the lip tip Any of various methods may be used as long as strict temperature control can be performed along the sheet flow up to the cooling roll.

In the process in which the melt-extruded thermoplastic polymer sheet is transferred to the cooling portion, the surface temperature difference between the front side and the back side of the strip-shaped thermoplastic polymer sheet is set within 15 ° C, preferably within 10 ° C. To do. If the surface temperature difference between the front side and the back side of the polymer sheet is larger than this, birefringence in the thickness direction of the polymer sheet increases, and irregularities on the sheet surface called die lines become large and the surface accuracy deteriorates.

Further, in the process of transferring the melt-extruded thermoplastic polymer sheet to the cooling portion, the surface temperature difference in the width direction of the band-shaped molten sheet is set within 15 ° C., preferably within 10 ° C. If the surface temperature difference in the width direction of the sheet is larger than this, the thickness accuracy decreases. It is considered that this is because when the polymer sheet is stretched from the die slip and cooled by the cooling roll, stretching unevenness occurs due to the difference in elastic modulus due to the temperature distribution. Further, the adhesion to the cooling roll also becomes uneven, and the birefringence in the plane and the thickness direction is deteriorated due to the uneven cooling efficiency. Further, the die line is increased in the same manner as described above, and the surface accuracy of the sheet is deteriorated.

In the present invention, when the glass transition point of the melt extruded thermoplastic polymer sheet is Tg, T
Temperature of dies such as dies and coat hanger dies (D1)
Is Tg + 80 <D1 <Tg + 150 [° C.]. The temperature (D1) of T-die or coat hanger die is Tg +
If the temperature is 80 [° C.] or less, the resin viscosity is high, and back pressure is applied to the die, and extrusion cannot be performed. Also, D1 is Tg + 1
When the temperature is 50 [° C.] or higher, the resin causes thermal decomposition, which leads to discoloration or generation of foreign matter.

The surface temperature (S1) of the polymer sheet when in contact with the cooled portion is Tg + 30 <S1 <Tg + 100.
[° C]. The surface temperature (S1) of the polymer sheet is Tg
When the temperature is +30 [° C.] or less, the polymer sheet is stretched from the die slip and cooled by a cooling roll, but the birefringence in the plane of the polymer sheet increases during stretching. When the surface temperature (S1) of the polymer sheet is Tg + 100 [° C.] or more, the temperature difference between the polymer sheet and the cooling roll is too large, and the stress at the time of forming into a sheet increases, resulting in increased birefringence and insufficient cooling capacity. The polymer sheet is easily fused to the cooling roll, resulting in poor appearance.

The cooling roll temperature (R1) is Tg-3.
0 <R1 <Tg + 30 [° C.]. If the cooling roll temperature (R1) is Tg-30 [° C] or lower, cooling wrinkles occur and the appearance becomes poor. Cooling roll temperature (R1) is Tg +
When the temperature is 30 [° C.] or higher, the polymer sheet is fused to the cooling roll, resulting in poor appearance.

The thickness of the thermoplastic polymer sheet is 150 to
1000 μm is preferable, and more preferably 200 to 50
It is 0 μm. If the thickness of the polymer sheet is thinner than this, it is difficult to handle when using a general-purpose liquid crystal panel production line, and it is difficult to maintain the liquid crystal cell gap. Especially, in a large-area liquid crystal display element, it is difficult to maintain the cell gap. Can not do it. On the other hand, when the thickness exceeds this range, the liquid crystal display causes a display defect called double image, and the thickness of the liquid crystal display element becomes thicker, which is not preferable in terms of function.

The planar retardation is preferably 2
It is 0 nm or less, more preferably 10 nm or less. The plane retardation is represented by Re = (Nx−Ny) × d, where Nx is the maximum refractive index in the polymer sheet surface and Ny is the minimum refractive index in the polymer sheet surface. is there. d is the thickness of the sheet. Retardation is 20n
When it exceeds m, the contrast of the liquid crystal display deteriorates,
The display cannot be seen clearly.

In-plane thickness tolerance of polymer sheet is 20 μm
The following is preferable, and 10 μm or less is more preferable.
If the in-plane thickness tolerance exceeds 20 μm, the cell may not be divided even when half-cut during the assembly of the liquid crystal cell. In addition, it is difficult to use as a high precision spacer.

Maximum surface roughness of polymer sheet (Rmax)
Is preferably 0.1 μm or less, more preferably 0.0 μm or less.
It is 5 μm or less. If the maximum surface roughness is larger than 0.1 μm, an abnormal cell gap of the liquid crystal occurs, resulting in display failure.

The glass transition point (Tg) of the thermoplastic polymer used in the present invention is preferably 150 ° C. or higher, more preferably 180 ° C. or higher. If the Tg of the thermoplastic polymer is less than 150 ° C., the sheet is softened at the heat treatment of the liquid crystal assembly process, for example, the baking of the alignment film and the seal curing temperature, which causes a defect in the product. Examples of such a thermoplastic resin include polysulfone, polyether sulfone, polyetherimide, norbornene-based resin, polyarylate, and resins obtained by blending these. Particularly, polyethersulfone has heat resistance, transparency, and dimensions. It is preferable because there is little change. Further, the resin used in the present invention may contain a small amount of a stabilizer, a lubricant, a dye or the like as an additive depending on the purpose.

The optical properties of the sheet of the present invention were measured by the following methods. Sheet temperature measurement method: A thermocouple was brought into contact with the surface of the thermoplastic polymer sheet melt-extruded from a die to measure the temperature. Sheet thickness: It is an average value measured in the plane of the polymer sheet with a contact type dial gauge. Thickness tolerance in the plane of the sheet: The difference between the maximum value and the minimum value measured in the plane of the polymer sheet with a contact type dial gauge.

Maximum surface roughness of polymer sheet (Rma
x) Contact-type precision step gauge (TENCOR INSTRUMENTS made AIPHA-STE
P200) is the maximum value of the unevenness measured over the width of the polymer sheet with a scan width of 2 mm. Retardation of Polymer Sheet Using a polarizing microscope BH2 manufactured by Olympus Optical Co., Ltd. and a Berek compensator, retardation at a wavelength of 550 nm was measured.

[0031]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples. [Example 1] Polyether sulfone resin (Sumitomo Chemical Co., Ltd.
Victorex PES4100G, Tg = 22
(6 ° C.) was melt extruded from a coat hanger die, and this molten thermoplastic polymer sheet was subjected to a cooling step to produce a thermoplastic polymer sheet. A sheet made of stainless steel was placed between the lip tip and the cooling roll at both sides where the width of the cooling roll was 50 mm from the surface of the polymer sheet to surround the sheet. Dice temperature is 350
C., and the cooling roll temperature was set to 220.degree. The temperature difference between the front and back surfaces of the polymer sheet was 5 ° C, the temperature difference between the surfaces in the width direction was 8 ° C, and the temperature of the polymer sheet when the cooling roll and the polymer sheet were in contact was 300 ° C. The thickness of the obtained sheet was 400 μm.

As a result, the in-plane thickness tolerance of the polymer sheet
(Rmax) is 15 μm, the retardation on a plane is 15 nm, and the maximum roughness of the surface of the polymer sheet is
A sheet having a high dimensional accuracy of (Rmax) of 0.06 μm was obtained.

The sheet obtained in Example 1 (thickness 400 μm
An organic layer was formed on m) as follows. That is,
Epoxy acrylate prepolymer (Showa Polymer Co., Ltd.)
Made, VR-60, molecular weight 1540, melting point 70 ° C) 100
Parts by weight, 400 parts by weight of butyl acetate, 100 parts by weight of cellosolve acetate and 2 parts by weight of benzoin ethyl ether are stirred and dissolved at 50 ° C. to prepare a uniform solution, which is prepared on the sheet using a gravure roll coater. Applied. Then, heat at 80 ° C. for 10 minutes to remove the solvent,
30 at a distance of 15 cm with a high pressure mercury lamp of 80 w / cm
The resin was cured by irradiation for 2 seconds to form an organic layer having a thickness of 0.5 μm. The organic layer was formed on both sides. Next, a mixed gas of oxygen / argon gas 9% was introduced at an initial vacuum degree of 3 × 10 ⁻⁴ Pa, and an inorganic layer of SiO ₂ was formed on the sheet by a DC magnetron method under the condition of 3 × 10 ⁻¹ Pa. Was deposited (500Å thickness). When the oxygen barrier property of this inorganic film was measured by the Mocon method, it was 1 cc / 24 hr · m.
² and the surface resistivity was measured to be 8.1 x 10
It was ¹² Ω.

Next, a transparent conductive film was similarly formed by the DC magnetron method. That is, the initial vacuum degree is 3 × 10 ⁻⁴
Introduce a mixed gas of oxygen / argon gas 4% at Pa,
A film was formed under the condition of 1 × 10 ⁻¹ Pa and In / In
In ² O ³ , SnO ² having an atomic ratio of + Sn of 0.98
To obtain a transparent conductive film. As a result of the measurement, the film thickness is 160
0 Å, specific resistance was 4 × 10 ⁻⁴ Ω-cm. After the film formation, a resist is applied and developed to obtain an etching solution of 10
pattern etching in vol% HCl, liquid temperature 40 ℃,
A pattern for an active matrix having a diagonal length of 3 inches and L / S = 150/50 μm was formed. After forming the pattern, an alignment film was applied and baked at 150 ° C. for 2 hours, followed by rubbing. After the rubbing treatment, spacers were scattered, a sealant was applied, the seal was cured at 150 ° C. to form a cell, and a liquid crystal was injected. After injecting liquid crystal,
The cell was divided by half-cutting the substrate, but could be divided without problems. In addition, when a polarizing plate was attached to the position where the contrast was maximum and a lighting test was performed, no disconnection was observed, and there was no display defect due to sheet retardation or liquid crystal cell gap abnormality. Indicated.

[Example 2] Amorphous norbornene type resin manufactured by Nippon Zeon Co., Ltd .: ZEONOR1600 (Tg16)
5 ° C.), the die temperature was set to 250 ° C., and the cooling roll temperature was set to 180 ° C. to produce a sheet. The temperature difference between the front and back surfaces of the polymer sheet is 5 ° C, the temperature difference between the surfaces in the width direction is 8 ° C, and the temperature of the polymer sheet when the cooling roll and the polymer sheet are in contact with each other is 220 ° C. Enclose from the lip tip to the cooling roll with a stainless steel enclosure,
A sheet having a thickness of 600 μm was formed. As a result, the in-plane thickness tolerance (Rmax) of the polymer sheet is 18 μm, the retardation in the plane is 15 nm, and the maximum surface roughness (Rmax) of the polymer sheet is 0.06 μm. Got

Comparative Example 1 A sheet was manufactured in the same manner as in Example 1 except that the stainless steel enclosure was removed.
The temperature difference between the front and back of the sheet was 17 ° C, and the width direction was 20 ° C. The thickness tolerance of the obtained sheet was 30 μm, the retardation was 40 nm, and the surface roughness was 0.2 μm. When assembled as a liquid crystal cell in the same manner, disconnection occurred when the liquid crystal cell was divided into cells, and the yield was reduced due to the inability to divide the cells. Furthermore, the contrast of the liquid crystal device was poor, and display defects due to uneven cell gaps occurred.

Comparative Example 2 A sheet was prepared in the same manner as in Example 1 except that a heater was installed in Example 1 and the temperature at which the polymer sheet came into contact with the cooling roll was 340 ° C. . The thickness tolerance of the obtained sheet is 25μ
m, retardation is 70 nm, and sheet surface roughness is 0.
It was 05 μm. When a liquid crystal cell was assembled using this sheet in the same manner as in Example 1, the contrast was poor and the display was difficult to see.

[0038]

EFFECTS OF THE INVENTION The thermoplastic polymer sheet of the present invention has a small planar retardation, excellent surface smoothness, less warp of the substrate and no die line. This sheet is most suitable as a spacer sheet and an optical sheet, and exhibits high-definition display without display unevenness when mounted on a liquid crystal display panel as a transparent electrode sheet for flexible liquid crystal display elements, for example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29L 7:00 B29L 7:00 11:00 11:00 C08L 81:06 C08L 81:06 (56) References JP-A-8- 171001 (JP, A) JP 10-86208 (JP, A) JP 9-11317 (JP, A) JP 2000-219752 (JP, A) JP 60-214923 (JP, A) 58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 B29C 47/00 C08L 81/06

Claims (6)

(57) [Claims] 1. A thermoplastic polymer is melt extruded in a sheet form from a T die or a coat hanger die, and the lip tip is
Cooling work by touching the chill roll with the separated molten sheet
A method for manufacturing a sheet that is solidified by applying
Temperature in the space where the sheet moves from the tip to the chill roll
Managing method of the molten sheet on the front side and the back side heat <br/> thermoplastic polymer sheet surface temperature difference you wherein the movement of Serco while maintaining within 15 ℃ of. 2. The surface temperature difference in the width direction of the molten sheet is 15
The method for producing a thermoplastic polymer sheet according to claim 1 , wherein the temperature is within the range of ℃. 3. A die as claimed in claim 1 or 2 of a thermoplastic polymer sheet manufacturing method comprising applying thermal insulation between the cooling steps. 4. The glass transition point of the thermoplastic polymer is Tg,
If the temperature of T die or coat hanger die is D1,
Tg + 80 ° C. <D1 <Tg + 150 ° C. When the surface temperature of the thermoplastic polymer when subjected to the cooling step is S1, Tg + 30 ° C. <S1 <Tg + 100 ° C., and when the cooling roll temperature is R1, Tg− 30 ° C <R1 <T
The method for producing a thermoplastic polymer sheet according to claim 1 , wherein the temperature is g + 30 ° C. 5. The obtained sheet has a glass transition point of 150.
Made of thermoplastic polymer with a temperature of ℃ or above
1000 μm, in-plane thickness tolerance of sheet ( Rmax ) 20μ
m or less, sheet surface roughness 0 . 1 μm or less, and
The planar retardation of the sheet is 20 nm or less.
1. The manufacturing method of 1. 6. The thermoplastic polymer is polyethersulfone.
The manufacturing method according to claim 5.