JPH0375110A - Continuous production of optical polycarbonate sheet - Google Patents

Abstract

PURPOSE:To drastically enhance refractive index and surface roughness by introducing polycarbonate resin specified in mol.wt. between a pair of double belts and press- molding it at the specified temp. and pressure in the inlet roll part thereof and then leading the molded form to an outlet part to take it while slowly cooling it at the specified temp. conditions between the double belts. CONSTITUTION:Aromatic polycarbonate having 15,000 - 35,000 mol.wt. is melted in an extruder 1 and extruded into a sheet shape from a T-die 2 and led to the inlet part of a double belt pressing device. The sheet shape is pinched between the upper and lower specular steel belts 3, 3' and press-molded at 160 - 280 deg.C and 10 - 250kg/cm<2> by the rolls 4, 4' in the inlet part. The specular surfaces of the steel belts 3, 3' are transferred and the sheet shape is molded into prescribed thickness. Then it is passed through the guide rolls 6. 6' in a state wherein it is pinched between the specular steel belts 3, 3'. It is slowly cooled at 160 - 240 deg.C in 0.5 - 10 minutes in the slowly cooling zones 9, 9' to remove an optical strain. Then it is led to the cooling zones 10, 10' and slowly cooled at <= 150 deg.C. The upper and lower specular steel belts 3, 3' are peeled in the peeling roll 7, 7' parts and thereafter the molded article is taken out from the double belt pressing device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for continuous production of polycarbonate resin sheets suitable for optical applications, particularly as substrates for optical disks and optical cards.

[Conventional technology and its problems]

Aromatic polycarbonate resin (hereinafter referred to as PC) has transparency, heat resistance, impact resistance, dimensional stability, etc., so it is widely used in the optical field, especially in compact discs and other products. It is often used as a substrate for optical disks.

These PC boards for optical discs are mainly manufactured by injection molding, but this method has the problem of large optical distortion. That is, the required performance as a substrate for an optical disk is a single-pass birefringence of 200 m or less, and it is desirable that the substrate does not change due to annealing in a molding machine or the like. These injection molding PCs for optics are generally used with a molecular weight of about 14,000 to 18,000 and excellent fluidity, but for substrates with a diameter of 200+ nm or more, the birefringence is 20 nm over the entire circumference. It was difficult to keep it below.

On the other hand, compact discs are required to be made into even lower-cost products, and the conventional injection molding method of producing a substrate on which the standby signal is transferred and processing this has been replaced with a method of directly processing it with the aim of lowering costs. Methods such as printing or laminating resin films on which signals have been formed have been proposed. For practical application of this proposed method, it is advantageous to use a sheet, which requires a sheet with a smooth surface and low birefringence. However, with the method of extruding this sheet from a conventional T-die extruder and pressing it with a roll, it is difficult to prevent birefringence due to press stress, scratches on the sheet surface in the T-die extrusion direction, and surface roughness due to the roll. Ta.

[Means to solve the problem]

The present inventors have completed the present invention as a result of extensive research into a method for manufacturing a PC sheet with birefringence of 200 m or less in a single pass and a smooth surface.

That is, the present invention has a molecular weight of 15.000 to 35.00.
0 polycarbonate resin is extruded into a sheet by a T-die extruder, and then introduced between a pair of double belts moving at a predetermined speed of a double belt press device,
Temperature at the inlet roll part: 160-280℃, pressure 10℃
It is characterized in that it is press-molded at ~250 kg/cor, then slowly cooled between double belts at a temperature of 160-240°C for 0.5-10 minutes, guided to an exit section, and taken out at a temperature of 150°C or less. A method for continuous production of optical polycarbonate sheets, wherein the belt of the double-belt device is a mirror-finished stainless steel belt with a surface roughness of 0.1- or less, and has a heating mechanism for slow cooling. Temperature 16 in 0.5-10 minutes in primary cooling zone
0 to 180°C, and then cooled to 140°C or less in a cooling zone having a cooling mechanism, and the optical polycarbonate sheet produced has a birefringence of 20n.
m or less.

The configuration of the present invention will be explained below.

First, the polycarbonate resin of the present invention is a polycarbonate resin with a molecular weight of 15.000 to 35, which is manufactured by a known method using dihydric phenol and phosgene or diphenyl carbonate.
．． 000 low-dust aromatic polycarbonate (low-dust PC), homo- and copolycarbonate resins, end-modified ones with long-chain alkyl groups or alkyl ester groups as end groups, branched ones, etc. Not limited. Typical aromatic polycarbonate resins include those produced by interfacial polymerization using 2゜2-bis(4-hydroxyphenyl〉propane (=bisphenol A)) and phosgene. The type of extruder used can be a single-screw or twin-screw extruder with or without a vent, and the form can be selected as appropriate, such as a powder containing water, powder, pellet, etc.

Next, the present invention will be explained with reference to the drawings.

Figure 1 shows the T-die extruder used in the manufacturing process of the present invention.
- It is an example of a schematic diagram showing a double belt press device from the gou part.

In Fig. 1, it is melted in the extruder (1), and from the T-gui (2) at the tip thereof, the temperature is usually 250 to 320°C, the die lip interval is 0.5 to 5.0 mm, and the width is 200 to 2 mm.
The molten PC sheet (A) extruded into a sheet of 000 mm, especially 400 to 1.000 mm, is led to the inlet of a double belt press device, and is placed between the upper and lower mirror-finished steel belts (3, 3'). Sandwiched, population department roll (4,
4°), temperature 160-280℃, pressure 10-250℃
kg/cd1 preferably 170~220℃, pressure 50~
Brass molded at 150 kg/cut to transfer a mirror surface of steel bell)' (3.3°), usually 0.3~
It is molded to a predetermined thickness selected from the range of 3.0 am, preferably 0.3 to 2.0 mm.

Here, the upper and lower mirrored steel bells) (3,3°) are
Double belt entrance roll or exit roll (4,4″
.

5.5°) from the population toward the exit at a predetermined speed, the speed of movement being determined by the desired residence time in the cooling zone for gradual cooling;
Usually selected from the range of 0.5 to 5.0 m/min. If the press molding temperature is less than 160℃, the mirror transfer will be insufficient and the scratches in the extrusion direction when extruded from the T-Gui will not be completely erased, and if the temperature is too high, the sheet will stick strongly at the roll part and peel off. This may cause inconveniences such as difficulty.

Next, it is passed through guide rolls (6, 6') while being sandwiched between mirror-polished steel bells (3, 3') and cooled to 0 at 160 to 240°C in a slow cooling zone (9, 9'') equipped with a heating mechanism.
．． For 5 to 10 minutes, preferably in the slow cooling zone <9,9
1 so that the temperature at the outlet of the
The PC sheet (A) is gradually cooled down for ~5 minutes to relieve stress and remove optical distortion. temperature is 160
If the time in the range of ~240°C is less than 0.5 minutes, the removal of optical distortion will be insufficient, and if the temperature is maintained for more than 10 minutes, the apparatus will become large, which is not preferable. In addition, if the temperature is less than 160°C, optical distortion cannot be removed, and if the temperature is too high, rapid cooling will be required in the next cooling zone that has a cooling mechanism, which may cause distortion due to contraction of the steel belt, which is not preferable. Not only is this undesirable, but it also generates shrinkage stress.

Next, a cooling zone (10, 10'
) is gradually cooled to a temperature of 150℃ or less, preferably 140℃ or less, and the upper and lower mirror-finished steel bells (3,3') are peeled off by a peeling roll (7, 7'). It is taken out from the belt press device, passes through holding rolls (8, 8'''), and is appropriately cut into predetermined dimensions to become a product.When the temperature of PC sheet (A) at the time of peeling is 150°C or higher, it will not have a mirror finish. This is not preferable because the peelability from the belt is insufficient and the sheet surface becomes rough due to peeling resistance.

The manufacturing method of the present invention has been explained above with reference to the schematic diagrams, together with its conditions. However, as the T-Guy extruder, a conventional T-die extruder for sheets may be used, but it is important that it has low dust. Since it is essential, it is preferable to select a material that generates less polycarbonate resin gel.

In addition, the upper and lower mirror-finished steel belts of the double belt press device are moved at a predetermined speed and subjected to constant tension by the inlet, outlet, or both rolls, and the material is preferably a mirror-finished belt made of stainless steel, and the surface has an average roughness. SaO,
It is preferable to have a mirror finish of ba++ or less, particularly 0.05p or less. The heating/pressurizing mechanism for the inlet roll and the driving mechanism for the inlet or outlet rolls are not particularly limited, but heating may be performed using a heating medium, pressurization may be performed using a hydraulic mechanism, or driving may be performed with smoother speed control. A motor is a typical example. Also,
The heating mechanism of the cooling zone (stress relaxation or pre-cooling zone) that has a heating mechanism is an infrared heater, heat medium, etc.
The cooling mechanism for a cooling zone that has a cooling mechanism is typically a method using air blowing, a heating medium, or the like.

Furthermore, since the PC sheet manufactured by the manufacturing method of the present invention is intended for use in optical applications, the extruder, T-Gui, double belt press device, take-up machine, and other auxiliary tools used in the manufacturing method are All designed to minimize dust generation.
It is designed to remove dust and is class 10.0.
It is installed in a clean room of class 5.000 or lower, preferably class 5.000 or lower.

〔Example〕

Hereinafter, a detailed explanation will be given using Examples and Comparative Examples.

Examples 1 to 3 and Comparative Examples 1 to 4 As a T-die extruder, an axle with a screw diameter of 50 mm and a lip spacing of 2111111. T- with a width of 400 mm
I used dice.

As a double belt press device, 5US with a width of 800mm
316 mirror finish belt with a surface roughness of 0.04-, a drive mechanism, a hydraulic mechanism, and a diameter 80mm belt with a heat medium jacket that can be heated by a heat medium through a rotary joint inside.
0mm inlet roll, diameter 1.000 with drive mechanism
mm exit roll, roll axis spacing at entrance and exit 6,200m
2,100 mm from the guide roll to the end of the cooling zone having a heating mechanism using a far-infrared heater, and 1,500 au from the cooling zone having a cooling mechanism using cold air blowing to the peeling roll.

Viscosity average molecular weight 29,000, size 0.5-1.0
Using a bisphenol A polycarbonate resin pellet containing 25,000 particles/g of dust, this was fed to an extruder and melted at a temperature of 260 to 280°C.
Extrude from T-gui at 80℃, immediately lead to double belt press inlet, press pressure of inlet roll is 150kg
/cnf, and the roll interval was adjusted so that the sheet thickness was 1.2 mm.

As shown in Table 1, the surface temperature of the inlet roll section, the temperature of the cooling zone (1) having a heating mechanism, the temperature of the cooling zone (2) having a cooling mechanism, and the residence time of each zone are adjusted by the belt speed. PC sheets were manufactured by changing the conditions.

Regarding the obtained PC sheet, birefringence was measured using an ellipsometer, and surface roughness was measured using a stylus meter.

These results are shown in Table 1.

Table 1-1 From the results in Table 1, it can be seen that if the temperature between the cooling zones with the heating mechanism is low, the elimination of optical distortion is insufficient, and when extruded from the T-gui Scratches in the extrusion direction are not sufficiently removed, and the surface roughness (average) is also large.Also, if the sheet is taken out without sufficient cooling in the cooling zone, the peelability of the sheet will be insufficient and the surface roughness will increase. It is understood that the texture becomes rough.

[Operation and effects of the invention]

PC manufactured by continuous production method of optical PC sheet according to the present invention
The sheet has significantly improved birefringence and surface roughness compared to conventional sheets, and has desirable properties for use in compact discs and optical cards. Moreover, since it has excellent productivity, it is also industrially excellent.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the manufacturing process of the continuous manufacturing method of an optical polycarbonate sheet of the present invention.

Claims (1)

[Claims] 1. A polycarbonate resin having a molecular weight in the range of 15,000 to 35,000 is extruded into a sheet using a T-die extruder, and then extruded between a pair of double belts moving at a predetermined speed of a double belt press device. At the inlet roll part, the temperature is 160-280℃ and the pressure is 10-250kg/cm.
Press molding at ^2, then temperature 16 between double belts.
A continuous manufacturing method for an optical polycarbonate sheet, which comprises slowly cooling the sheet at 0 to 240°C for 0.5 to 10 minutes, guiding it to an outlet and taking it out at a temperature of 150°C or lower. 2 The belt of the double belt device has a surface roughness of 0.1 μm.
2. The method for continuously producing an optical polycarbonate sheet according to claim 1, wherein the polishing belt is made of stainless steel and has a mirror finish. 3. The slow cooling is performed in a primary cooling zone having a heating mechanism at a temperature of 0.
2. The method for continuously producing an optical polycarbonate sheet according to claim 1, wherein the temperature is raised to 160 to 180°C for 5 to 10 minutes, and then the cooling is carried out to 140°C or lower in a cooling zone having a cooling mechanism. 4 Birefringence of the optical polycarbonate sheet is 20n
2. The method for continuously producing an optical polycarbonate sheet according to claim 1, wherein the polycarbonate sheet is less than or equal to m.