JP2003005295A - Method for manufacturing sheet member for optical screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively imparting warpage to a sheet member under the conditions of suppressing dimensional changes or deformation of the surface form. SOLUTION: The sheet member for an optical screen is manufactured by heat treating a sheet member made of a resin at the temperature T lower by 5 deg.C to 20 deg.C than the thermal deformation temperature of the resin for a period t or longer to impart warpage to the sheet member. The period t is determined by measuring the relaxation modulus of the resin at the above temperature T and measuring the time when the relaxation modulus decreases to 1/5 of the initial relaxation modulus at the time when the measurement is started.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sheet-like member for an optical screen, for example, for a transmission screen of a projection television. 2. Description of the Related Art An optical screen such as a transmission screen of a projection television is usually constituted by sheet members such as a Fresnel lens sheet, a lenticular lens sheet, and a front panel. In general,
A configuration in which a Fresnel lens sheet and a lenticular lens sheet are superposed has been adopted, and in recent years, a configuration in which a front panel has been further superimposed has been employed for the purpose of protecting these lens sheets. In the above optical screen, a phenomenon called "floating" occurs between the sheet-like members due to a change in temperature and humidity in the installation environment, which may cause a problem such as a reduction in image resolution. In order to solve this problem, a method of imparting a warp to a sheet-like member for the purpose of enhancing the adhesion between the sheet-like members is known.
Japanese Patent Application Laid-Open No. 216773 describes a method in which a sheet-like member is extruded into a curved shape and then heated on a mold having a curved shape. [0004] However, in the conventional method, when the sheet-like member is warped, a dimensional change or deformation of the surface shape may be caused, or the warpage is insufficiently applied. The object of the present invention is to solve these problems and to efficiently warp the sheet-like member under the condition that the dimensional change and the deformation of the surface shape are suppressed. Is to provide. As a result of intensive studies, the present inventor has found that the above object can be achieved by subjecting a sheet-like member to heat treatment under a specific temperature condition for a specific time. The invention has been completed. That is, according to the present invention, a sheet-like member made of a resin is heat-treated at a temperature T lower by 5 to 20 ° C. than the thermal deformation temperature of the resin for the following time t or more. The present invention relates to a method for producing a sheet member for an optical screen by giving a warp. Time t: when the relaxation elastic modulus of the resin is measured at the temperature T, the relaxation elastic modulus is 1/1 / the relaxation elastic modulus at the start of the measurement.
Time to reach 5. Hereinafter, the present invention will be described in detail.
The sheet member used in the method of the present invention is made of a resin, and a thermoplastic resin having high transparency is usually used as the resin. Examples of the thermoplastic resin include acrylic resins such as methyl methacrylate polymer, methyl methacrylate-methyl acrylate copolymer, methyl methacrylate-styrene copolymer, and methyl methacrylate-styrene-butadiene copolymer. Resins, polycarbonate resins, and the like can be used, and two or more of them can be used as necessary. These resins may be those reinforced with rubber, and various additives such as light diffusing agents, antioxidants, plasticizers, release agents, coloring agents, antistatic agents, ultraviolet absorbers, flame retardants, etc. Is one or two depending on the purpose
More than one kind may be added. The above-mentioned sheet-like member is for constituting an optical screen such as a transmission type screen of a projection television, and is, for example, a sheet-like screen constituting member such as a Fresnel lens sheet, a lenticular lens sheet and a front panel. And a sheet-like base material used as a so-called original plate when producing them. As a Fresnel lens sheet, for example,
It may be obtained by cast molding, may be a sheet-like substrate obtained by extrusion molding or the like, and may be formed by imparting a Fresnel lens shape by press molding, or may be an ultraviolet ray Curable resin may be cured so as to form a Fresnel lens shape. The lenticular lens sheet may be, for example, a sheet obtained by extrusion or cast molding, or a sheet-like substrate having a lenticular lens shape formed by press molding. Then, a film obtained by laminating a film having a lenticular lens shape formed on its surface with an ultraviolet-curable resin to a sheet-like substrate may be used. As the front panel, for example,
It may be obtained by extrusion molding or cast molding, or may have been subjected to a surface treatment such as a hard coat or a low reflection coat. Further, the sheet-like base material (Fresnel lens original plate) and the front panel for the Fresnel lens may be subjected to surface processing such as a surface mat, a prism, a lenticular lens, and a linear Fresnel lens. [0013] The sheet-like member is placed on a warp table having a desired curved shape or the like, and is heat-treated.
The sheet-shaped member can be warped. When the sheet-like members are placed on the warp table, a plurality of the sheet-like members may be laminated as necessary, so that a plurality of sheet-like members can be heat-treated at one time. Is reduced, the number of sheets is appropriately adjusted. Examples of the heat treatment method include a method in which hot air is blown to the sheet member in a hot air oven or the like, a method in which the sheet member is heated using an infrared heater, and the like. The heat treatment is performed at a temperature T that is 5 to 20 ° C. lower than the thermal deformation temperature of the resin constituting the sheet-shaped member for the following time t or more. Time t: time required for the relaxation elastic modulus of the resin constituting the sheet-shaped member to be 1/5 of the relaxation elastic modulus at the start of the measurement when measured at the above temperature T. The heat treatment temperature T is equal to the thermal deformation temperature of the resin minus 5 ° C.
When the heat treatment temperature T is less than the thermal deformation temperature of the resin −20 ° C., it takes a long time to impart a desired warp. And productivity is not sufficient. If the heat treatment time is less than t, the warpage is insufficiently provided. The thermal deformation temperature of the resin is determined according to JIS K7202.
Alternatively, it can be measured by the test method specified in ASTM D648. The relaxation modulus of the resin is
Introduction to Polymer Chemistry (1st edition) 154 issued by Kagaku Dojin
As described on pages 156 to 156, the relaxation elastic modulus at various temperatures can be measured, and the composite curve of the relaxation elastic modulus at a certain reference temperature can be obtained by superimposing time-temperature. it can. The sheet-like member manufactured as described above is manufactured by a method in which a dimensional change and a surface shape change are suppressed.
It has a desired warpage and is suitably used as a constituent member of an optical screen or a base material thereof. The present invention will now be described by way of examples, which should not be construed as limiting the invention thereto. Hereinafter, as the acrylic resin, an impact-resistant acrylic resin having a heat distortion temperature of 100 ° C. [SUMIPEX B HT018E manufactured by Sumitomo Chemical Co., Ltd.]
Was used. (Measurement of Relaxation Modulus)
Using an extruder (manufactured by Tanabe Plastics Machine Co., Ltd.) with a screw diameter of 40 mm through this roll, the resin temperature was 260
It was extruded at 2 ° C. into a resin sheet having a thickness of 2 mm. A sample of 5 mm × 45 mm was cut out from the obtained sheet, and the sample was subjected to 70 ° C., 80 ° C. using a viscoelasticity measuring device [RDA-2 manufactured by Rheometrics Co., Ltd.].
At each temperature of 85 ° C., 90 ° C., 95 ° C., and 100 ° C., the relaxation modulus was measured at an initial strain of 1%. The relaxation modulus at the start of the measurement was 700 MPa. Based on these measured values, a composite curve of the relaxation elastic modulus with a reference temperature of 80 ° C. was prepared. as a result,
The relaxation modulus at each conversion time is 70 at 0.001 second.
0 MPa, 400 MPa at 1000 seconds, 200 MPa at 10,000 seconds, 140 MPa at 20,000 seconds, 7000
It was 70 MPa at 0 seconds. The transfer coefficient at each temperature is 20 at 70 ° C. and 1, 8 at 80 ° C. (reference temperature).
0.2 at 5 ° C, 0.05 at 90 ° C, 0.00 at 95 ° C
8, 0.0008 at 100 ° C. Therefore,
The time required for the relaxation elastic modulus at each temperature to be 1/5 of the relaxation elastic modulus at the start of measurement is 400,000 seconds at 70 ° C. (20,000 seconds × 20) and 200 at 80 ° C. (reference temperature).
00 seconds, 4000 seconds at 85 ° C. (20,000 seconds × 0.
2) at 90 ° C. for 1000 seconds (20,000 seconds × 0.0
5) at 95 ° C. for 160 seconds (20,000 seconds × 0.00)
8) at 100 ° C. for 16 seconds (20,000 seconds × 0.000
8). (Preparation of sheet-like member)
Using a 150 mm screw extruder [manufactured by Hitachi Zosen Corporation] through three rolls at a resin temperature of 265 ° C.
It was extruded into a resin sheet having a thickness of 1.8 mm, a width of 900 mm, and a length of 1200 mm. From the obtained sheet, 75c
A sample of m (width direction during extrusion molding) × 30 cm (length direction during extrusion molding) was cut out to obtain a sheet-like member.
The sheet-shaped member is suspended by supporting the central portion of one long side so that the long side is horizontal and the short side is vertical, and the amount of warpage in the long side direction (maximum warp depth) is measured. It was about 6 mm. Example 1 The above sheet-like member was 75 cm × 3 as shown in FIG.
It is made of 0cm plywood, and the amount of warp in the long side direction is 15m
The sheet-shaped member was allowed to stand with the convex surface of the sheet-shaped member facing downward on a warp table 1 having a concave mounting surface of m and placed in a hot-air dryer at 90 ° C. for 30 minutes to perform heat treatment. After cooling to room temperature, the amount of warpage in the long side direction was measured in the same manner as described above. As a result, the amount of warpage was 15 mm, and the same amount of warpage as that of the warp table could be provided. The relaxation modulus at 90 ° C. for 30 minutes (1800 seconds) obtained from the composite curve of the relaxation modulus and the transfer coefficient is 100 MPa (the same as the actually measured value), which is 14% of the relaxation modulus at the start of the measurement. It is. Comparative Example 1 The same operation as in Example 1 was performed, except that the heat treatment was performed in a hot-air dryer at 85 ° C. for 15 minutes. The warpage in the long side direction was 7 mm, and the increase in the warpage due to the heat treatment was slight. The relaxation modulus at 85 ° C. for 15 minutes (900 seconds) obtained from the composite curve of the relaxation modulus and the transfer coefficient is 300 MPa (same as the actually measured value), which is 42% of the relaxation modulus at the start of the measurement. It is. Comparative Example 2 The same operation as in Example 1 was performed, except that the heat treatment was performed in a hot air drier at 80 ° C. for 60 minutes. The warpage in the long side direction was 8.5 mm, and the increase in the warpage due to the heat treatment was slight. The relaxation modulus at 80 ° C. for 60 minutes (3600 seconds) obtained from the composite curve of the relaxation modulus and the transfer coefficient is 290 MPa, which is 41% of the relaxation modulus at the start of the measurement. According to the present invention, a sheet-like member for an optical screen having a desired warpage can be manufactured under the condition that the dimensional change and the deformation of the surface shape are suppressed. It is possible to prevent a decrease in image resolution due to occurrence of "floating".

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing an entire warp table used in an embodiment. [Explanation of Signs] 1 ... Warp

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Claims (1)

Claims: 1. A sheet-like member made of a resin is heat-treated at a temperature T 5 to 20 ° C. lower than a thermal deformation temperature of the resin for at least the following time t to obtain a sheet-like member. A method for producing a sheet-like member for an optical screen, wherein the member is warped. Time t: when the relaxation elastic modulus of the resin is measured at the temperature T, the relaxation elastic modulus is 1/1 / the relaxation elastic modulus at the start of the measurement.
Time to reach 5.