JPH02238922A - Apparatus for preparing thermoplastic resin sheet and film capable of adjusting automatically optical distorsion - Google Patents

Abstract

PURPOSE:To obtain a sheet with a preset optical distorsion by placing a birefringence measuring device and a thickness meter between a glazing unit and a take-up unit and connecting an arithmetic unit to a speed rate setting device. CONSTITUTION:A molten resin 5 extruded from a die 1 is fed between a lower roll 2a and a middle roll 2b and is forwarded around the upper roll 2c approximately half round to transfer a sheet surface during this period. It is then cooled and solidified and the glazing is finished and the thickness of the sheet is determined. It is finally taken up on take-up rolls 10a and 10b. During this procedure, the thickness of the sheet is successively measured by means of a thickness measuring sensor 6 and a thickness meter 7 and the birefringence of the sheet is also successively measured by means of birefringence measuring sensors 8a and 8b and a birefringence measuring device 9. The values of the thickness and the birefringence of the sheet is put in an arithmetic unit 15 to operate a birefringence. Comparing the operated birefringence with the aimed birefringence set by means of a birefringence setting device 17, a signal is sent to a speed rate setting device so as to make these values equal and the rotating speed of the take-up rolls 10a and 10b to the glazing rolls 2a, 2b and 2c is controlled. E.g. if a sheet with little optical distorsion is required, the set value is made zero.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to thermoplastic resin sheets and films (hereinafter referred to as
The present invention relates to an extrusion molding apparatus (described as a sheet), and more particularly to a sheet manufacturing apparatus that automatically adjusts optical distortion caused to a sheet extruded from a T-die. [Prior Art] Thermoplastic resin sheets with low or constant optical distortion are required in optical applications such as optical recording materials and lenses, and in the field of secondary processed products that undergo thermoforming. Sheets produced using a combination of a T-die, a polishing device, and a pulling device had considerably large optical distortions or were unusable due to large variations. As a method for producing a sheet with low optical anisotropy, for example, the method described in Japanese Patent Application Laid-Open No. 60-40223 is known. In this process, thermoplastic resin A is coextruded into a sheet with both sides covered with non-adhesive thermoplastic resin B, and then the outer thermoplastic resin B layer is peeled off and contacted with the inner wall of the die. This is a method to obtain a sheet with low optical anisotropy by extracting only the part that is not subject to almost any shear stress. Furthermore, Japanese Patent Application Laid-open No. 57-2725 describes a method and apparatus for manufacturing a continuous plastic sheet or film,
A method and apparatus for controlling the speed of a stripping roll during stripping of a sheet from a roll to obtain a sheet having a predetermined degree of residual strain is described.

[Problem to be solved by the invention]

However, the above conventional technology has the following problems. Thermoplastic resin A is coextruded into a sheet with both sides covered with non-adhesive thermoplastic resin B to form a thermoplastic resin B layer/thermoplastic resin A layer/thermoplastic resin B layer 3.
The method of obtaining a layered sheet requires expensive equipment for coextrusion, and in order to obtain a high-quality sheet with low optical anisotropy, the thickness ratio of layer A to the entire sheet must be 90%. It had to be as follows, which had the disadvantage that a large amount of coating material used for the B layer was wasted.

It also controls the speed of the stripping roll,
The method of obtaining a sheet with a predetermined amount of residual strain does not have a mechanism to detect the strain state and automatically adjust the strain, and the roll speed must be controlled after measuring the residual strain of the finished sheet. Therefore, the sheet obtained while controlling the speed will not have the desired residual strain, and the residual strain will not be the same even at the set roll speed due to non-uniformity of the surrounding environment during the cooling process, such as fluctuations in temperature. The drawback was that it fluctuated.

[Means to solve the problem]

Therefore, as a result of intensive study on how to adjust the optical distortion caused to the sheet during sheet manufacturing to a constant value, the present invention was achieved.

That is, the present invention was obtained as a result of studies to eliminate the various drawbacks of the above-mentioned prior art, and includes a T-gui, a polishing device,
In the thermoplastic resin sheet and film manufacturing apparatus, the thermoplastic resin sheet and film manufacturing apparatus includes a take-off device arranged at a distance from the burnishing device, and the thermoplastic resin sheet and film are separated between the burnishing device and the take-off device. A glazing roll motor control panel is equipped with a birefringence measuring device to measure refraction and a thickness gauge to measure thickness, and a glazing roll motor control panel that controls the motor that drives multiple glazing rolls attached to the glazing device. A take-up roll motor control panel that controls the motor that drives the take-up roll attached to the take-up device is connected via a speed ratio setting device, and a birefringence measuring device, a thickness gauge, and a birefringence meter are connected to the speed ratio setting device. The present invention provides an apparatus for manufacturing thermoplastic resin sheets and films, characterized in that an arithmetic unit is connected to a rate setting device. [Function] According to the sheet manufacturing apparatus according to the present invention, the value per unit thickness obtained by calculating the measured values from the birefringence measuring device and the thickness meter disposed between the polishing device and the take-up device. In order to keep the birefringence value (hereinafter referred to as birefringence index) constant and the birefringence index preset in the birefringence setting device, the rotation speed of the polishing roll attached to the polishing device and the pull By sending a signal to the speed ratio setting device that determines the rotation speed ratio of the take-up rolls attached to the take-up device and automatically adjusting the roll rotation speed ratio, it is possible to obtain a sheet with a preset optical distortion. becomes.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. In FIG. 1, 1 is a gouer for extruding the molten resin extruded from an extruder (not shown) into a sheet, and the sheet-shaped molten resin 5 extruded from the die 1 is placed between the lower roll 2a and the middle roll 2b. The sheet is supplied and rolled with rolls to smooth the sheet surface, and is brought into close contact with the roll surface to cool it, and after making approximately half a turn around the middle roll 2b, it makes approximately half a turn around the upper roll 2c, during which time the sheet surface is transferred and cooled and solidified. After polishing and applying the sheet, the thickness of the sheet is determined, the sheet is taken up by take-up rolls 10a and 10b disposed downstream, and the sheet further proceeds to a post-processing step (not shown). Reference numeral 3 denotes a frame of a polishing device for supporting the bearings at both ends of the polishing rolls 2a, 2b, 2C and the detent motors 4a, 4b, 4c of each roll; 12 denotes the bearings at both ends of the take-up rolls 10a, 10b; This is a frame of a take-off device for supporting the decoupling motor l1. The thickness of the sheet stripped from the upper roll 2C of the polishing device is sequentially measured by a thickness measurement sensor 6 and a thickness gauge 7 before being taken off by take-up rolls loa and 10b of a take-up device. At the same time, the birefringence of the sheet is sequentially measured by the birefringence measuring sensor 8as8b and the birefringence measuring device 9, and these values of plate thickness and birefringence are input into the calculator 15 to calculate the birefringence.

On the other hand, the decoupling motors 4a, 4b, and 4C that control the polishing rolls attached to the polishing device are controlled by the polishing roll motor control panels 13a, 13b, and 13c that control the glossing rolls 2a, 2b, and 2b. . The panels 13a, 13b, 13c and the take-off roll motor control board l4 are connected via a speed ratio setting device l6, and the take-off rolls 10a, lOb are connected to the polishing wheels 2a, 2b,
It is controlled to rotate at a speed that is a constant ratio to 2c. The birefringence calculated by the calculator l5 in the above,
The target birefringence set in the birefringence setter l7 is compared with the target birefringence, and a signal is sent to the speed ratio setter l6 so that the birefringence becomes equal. The rotation speed of 10b is controlled.

Here, the birefringence set in the birefringence setter 17 can be set arbitrarily; for example, when trying to obtain a sheet with very little optical distortion, the set value may be set to O. Further, when adjusting the average value of the birefringence index in the width direction of the sheet to be constant, the thickness measurement sensor 6 and the birefringence measurement sensors 8a and 8b may be simultaneously scanned in the width direction.

As for the arrangement of the polishing rolls, in this example, three rolls are arranged vertically as shown in the figure, but there is a roll located downstream of the polishing device that rotates at a speed that is a constant ratio to the rotational speed of the polishing rolls. It is possible to use any conventional arrangement of glazing rolls provided that a controlled take-off device is provided. A polymethyl methacrylate sheet with a thickness of 2.0 mm+ produced using the apparatus of this example was sampled every hour, and the birefringence was measured using an automatic ellipsometer DVA-3 6 L type manufactured by Mizojiri Optical Co., Ltd. When measured twice, the maximum deviation from the average value was 4.78 nm. Next, without using the birefringence measuring sensors 8a, 8b and the birefringence measuring device 9, the rotational speed of the polishing rolls 2a, 2b, 2C is determined. While keeping the rotational speed ratio of the take-up rolls 5a and 5b constant, the thickness was 2.0M in the same manner as above.
As a result of sampling polymethyl methacrylate sheets and measuring their birefringence, the maximum deviation from the average value was 3.
It was 5.85 nm.

〔Effect of the invention〕

According to the apparatus of the present invention, the birefringence of the cooled and solidified sheet is directly measured between the glazing device and the take-up device, and the glazing roll is rotated so that the birefringence value becomes a preset value. Since the ratio of rotational speed of the take-up roll to the speed is determined, it is possible to reduce variations in optical distortion even in the case of non-uniformities in the surrounding environment such as temperature fluctuations during the cooling process, and the rotation speed of the take-up roll is automatically controlled. Since this process is carried out in a very economical way, it is possible to obtain sheets with a desired optical strain in large quantities extremely economically.

[Brief explanation of drawings]

FIG. 1 is a concrete configuration diagram of an apparatus showing an embodiment of the present invention. 1: T-die 2a, 2b, 2c: Glazing roll 3: Attachment device frame: Thickness measurement sensor: Thickness gauge a, 8b: Birefringence measurement sensor: ? J [Refractometer Oa, 10b: Taking-off roll 2: Taking-off device frame 5: Arithmetic unit 6: Speed ratio setting device 7: Birefringence setting device

Claims (1)

[Claims] A thermoplastic resin sheet and film manufacturing apparatus comprising a T-die, a glazing device, and a take-off device disposed at a distance from the glazing device, wherein the glazing device and the take-off device are provided. A birefringence measuring device for measuring the birefringence of the thermoplastic resin sheet and film and a thickness gauge for measuring the thickness are arranged between them, and a motor for stirring a plurality of polishing rolls attached to the polishing device. A polishing roll motor control panel that controls the speed ratio and a take-up roll motor control board that controls the motor that drives the take-up roll attached to the take-up device are connected via a speed ratio setting device, and further, the speed ratio A thermoplastic resin sheet and film manufacturing apparatus, characterized in that a setting device is connected to an arithmetic unit to which the birefringence measuring device, the thickness gauge, and the birefringence setting device are connected.