JPH0635070A - Projecting screen - Google Patents

Abstract

PURPOSE:To make the projection screen optically uniform and to improve its color tones by essentially consisting of strands of a polycarbonate resin and forming light absorbers consisting of an acrylic resin as a base material between the strands. CONSTITUTION:The many light transmissive strands 1 are joined and arranged in parallel and the light absorbers 2 are formed between the respective strands 1. The polycarbonate resin is used as the essential component of the transparent strands 1 in terms of dynamic properties, such as impact resistance, heat resistance, water resistance, dimensional stability and fire retardance. The acrylic resin is formed of a copolymer of ethyl acrylate and/or methyl acrylate in a 0 to 15wt.% range as a copolymer of polymethyl acrylate and ethyl acrylate or methyl acrylate. The change of the constitution and formation of the strands 1 and the light absorbers 2 are properly selectable from the molten state to the solidified state by controlling the content of the copolymer within this range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection screen used as a screen for a projection television, a microfilm reader, etc., and more particularly to an optically uniform projection screen without screen spots.

[0002]

2. Description of the Related Art Projection screens such as transmissive screens or reflective screens are widely used for projecting television images, microfilm images and the like to realize a desired display. This type of screen has a predetermined lens shape on the entrance surface and / or the exit surface so that the screen is bright when viewed by an observer and the viewing angle is widened, and a double-sided lenticular lens is generally used. .

In a projection screen using a double-sided lenticular lens, the misalignment of the axes of the double-sided lenses adversely affects the screen characteristics. Therefore, in order to obtain good screen characteristics, it is necessary to accurately align the double-sided lenticular lenses. It becomes necessary to do it. However, as a method for manufacturing a double-sided lenticular lens, an extrusion molding method, a casting method by cell casting, a heat pressing method, or the like is performed, but these are all directly or indirectly using a metal mold or the like. It is a method of transferring to a resin plate, and it is difficult to accurately perform the dimensional accuracy of the master mold, mold temperature control during molding, alignment of the double-sided mold, etc., and sufficiently improve the alignment accuracy of the double-sided lenticular lens. Was difficult.

On the other hand, there is an increasing demand for high definition of large televisions, and the lenticular lens of the projection screen is also required to have a fine pitch.
However, in the conventional manufacturing method as described above, it is not easy to reduce the displacement of the lens position on the front and back sides of the double-sided lenticular lens of about 1 meter square to make it finer pitch, and it is sufficient to meet the demand for fine pitching. I could not respond. Therefore, the present applicant has filed Japanese Patent Application No. 1-3.
As in Japanese Patent Application No. 43778 and Japanese Patent Application No. 2-4117, a method for manufacturing a projection screen is proposed in which a large number of plastic-based strands are melt-spun and the strands are aligned in a sheet shape and adjacent strands are fused together. is doing.

In such a projection screen, polymethylmethacrylate, polycarbonate, which has good transparency as a plastic strand and excellent workability,
Polyvinyl chloride, polystyrene, etc. are used. Among them, polymethyl methacrylate, which is excellent in transparency and processability, is widely used. However, projection screens installed in vehicles such as airplanes and public places are required to be flame retardant from the viewpoint of disaster prevention, and have excellent mechanical properties such as impact resistance and heat resistance. Polycarbonate, which is excellent in flame retardancy as well as dimensional stability such as resistance and water resistance, has been used.

Further, in the case where the lenticular lens is formed on the light incident surface side like the double-sided lenticular lens, the external light incident from the light emitting surface side is partially reflected by the light incident surface side lenticular lens, and Light emitted from the side to make the surface image whitish to reduce the contrast, or part of the regular image light entering from the light incident surface side is reflected by the light emitting surface side lenticular lens, and this reflected light is further reflected on the light incident surface side. The light may be partially reflected by the side lenticular lens and emitted from the side of the light exit surface to cause image bleeding and flare such as double and triple images. In order to solve such a problem in image display, a light absorber in which a light absorber made of a black pigment such as carbon black is mixed in a resin is formed between strands. In general, as the resin serving as the base material of the light absorber, a resin that is the same as or similar to the strand has been used from the viewpoint of adhesion to the strand. That is, in the strand containing polycarbonate as a main component, a light absorber in which carbon black was mixed with polycarbonate was formed.

[0007]

However, as shown in FIG. 6, a strand 1 containing polycarbonate as a main component is used.
In addition, when the light absorber 2 based on polycarbonate is formed, they influence each other in the process of solidifying, and the lens portion of the lenticular lens does not have a desired shape, so that the lens portion is relatively shaped like 1 '. A portion having a lens shape with a gentle curvature is generated, a defective portion of focal light diffusion is generated, which causes screen unevenness, and an optically nonuniform portion is generated on the screen.

[0008] Such a phenomenon is caused by melt-spinning a large number of plastic-based strands, aligning these strands in a sheet shape, and fusing adjacent strands together to form a light absorber at the same time. It is likely to occur due to the delicate positional accuracy of the light absorber discharge holes, slight temperature unevenness inside and outside the nozzle, fluctuations in the discharge amount, and the like, which is a particular problem.

[0009]

In view of such circumstances, the inventors of the present invention have arrived at the present invention as a result of earnestly examining the material of the plastic strand and the material of the light absorber.

That is, the projection screen of the present invention is a projection screen in which a large number of transparent plastic strands are arranged in parallel, and adjacent strands are joined and integrated into a sheet shape. With polycarbonate resin as the main component,
A light absorber having an acrylic resin as a base material is formed between the strands.

In the projection screen of the present invention, as shown in the partially enlarged view of FIG. 1, a large number of translucent strands 1 are joined and arranged in parallel, and a light absorber 2 is provided between each strand 1. Has been formed. FIG. 2 shows an enlarged view showing a cross section of the projection screen of the present invention.

The translucent strand of the present invention contains a polycarbonate resin as a main component from the viewpoint of mechanical properties such as impact resistance, heat resistance, water resistance, dimensional stability and flame retardancy. Examples of the polycarbonate resin include those having about 10 to 400 repeating units represented by the following general formula (1).

[0013]

[Chemical 1]

Where A is a divalent aromatic group,
Specifically, the following (2) to (6) can be exemplified.

[0015]

[Chemical 2]

[0016]

[Chemical 3]

[0017]

[Chemical 4]

[0018]

[Chemical 5]

[0019]

[Chemical 6]

Such a polycarbonate resin is produced, for example, by the method described in US Pat. No. 3,989,672 and has a refractive index of 1.57 to 1.5.
9 is preferable. In the present invention, the polycarbonate produced by the reaction of bisphenol A and phosgene, that is, A in the above general formula (1) is an aromatic group of the above (6), and the number of repeating units is 40 to 40.
A refractive index of 400 of about 1.58 is preferred.

In the present invention, a colored and transparent material in which an appropriate colorant is mixed as a light-transmissive strand may be used, or a light diffusing agent may be mixed in the whole or in a layer form. Further, if necessary, additives such as a light stabilizer and a heat deterioration preventing agent may be added.

In the present invention, it is important to form a light absorber using an acrylic resin as a base material. This shows a proper interaction between the acrylic resin of the light absorber and the polycarbonate resin of the translucent strand,
This is because there is little influence on the lens shape formation during the solidification process of the polycarbonate-based resin, and the adhesive strength between the translucent strand and the light absorber becomes sufficient. As the acrylic resin, a homopolymer of methyl acrylate or methyl methacrylate, a copolymer of methyl acrylate and methyl methacrylate, methyl acrylate or methyl methacrylate and ethyl (meth) acrylate, butyl (meth) acrylate, (meth) Examples thereof include a copolymer with acrylonitrile. Among them, polymethyl methacrylate and a copolymer of polymethyl methacrylate and ethyl acrylate or methyl acrylate are particularly preferable.

The copolymer of polymethylmethacrylate and ethyl acrylate or methyl acrylate is preferably such that the copolymerization amount of ethyl acrylate and / or methyl acrylate is in the range of 0 to 15% by weight. By controlling the above, it is possible to appropriately select the change in the structure formation of the strand and the light absorber from the molten state to the solidification, which is preferable in terms of shape control of the lenticular lens, height control of the light absorber, and the like. When the copolymerization amount of ethyl acrylate and / or methyl acrylate exceeds 15% by weight, the interaction with the polycarbonate resin is impaired and the heat resistance is deteriorated, which is not preferable.

The light absorber of the present invention is the above acrylic resin containing a light absorber in the range of 0.1 to 3% by weight. The light absorber is a dye type or carbon black. A system or a mixed system of these can be used. In the present invention, the light absorber has a flame retardant,
You may add additives, such as a matting agent, as needed.

The projection screen of the present invention is manufactured by the melt extrusion method in principle. An example of manufacturing the projection screen of the present invention will be described below with reference to FIGS. 3 to 5.

In FIG. 3, 3 is an extruder, 4 is a nozzle holder equipped with a nozzle, and melted polycarbonate resin is discharged from an orifice. The discharging direction may be either upward or downward, but it is preferable to discharge upward in terms of uniform strands, pitch setting, and the like. As the nozzle, for example, the one in which the orifices 12 and 13 as shown in FIGS. 4 and 5 (a partially enlarged view of FIG. 4) are arranged in a substantially horseshoe shape is used. The orifice 12 discharges a polycarbonate resin for forming a strand, and the orifice 13 discharges a mixture of an acrylic resin for a light absorber and a light absorber.

In the annular sheet 5 of translucent strands of polycarbonate resin discharged, adjacent strands are fused and integrated between the strands, and a light absorber is formed between the strands on one surface of the strands. It is pulled up along the inner wall of the annular guide 6, and the annular sheet is spread by the trowel-shaped guide 7 and the rod-shaped straight guide 8 into a flat sheet, and at the same time the advancing direction of the sheet is changed by the rod-shaped straight guide, and the sheet is taken by the nip roller 9. It is wound up on the reel 10. If necessary, the sheet may be subjected to a slight heat extension.

The projection screen obtained has a cross-sectional shape as shown in FIG. In the figure, 1 is a translucent strand made of a polycarbonate resin, and a light absorber 2 made of an acrylic resin and a light absorber is formed between the strands. The translucent strand 1 has a substantially oval cross section, but various shapes such as a circular shape or a daruma shape can be appropriately selected depending on the nozzle cross section shape and spinning conditions. The size of the light-transmissive strand 1 is about 0.1 to 1.5 mm, although it varies depending on the use and purpose of the screen, and is sufficiently compatible with the fine pitch of the screen. Furthermore, the outer surface of the light-transmissive strand 1 may be smooth, or may be formed with fine irregularities to prevent external light from being reflected.

The projection screen of the present invention is preferably formed of a single sheet, but may be formed by connecting a plurality of sheets. When the projection screen of the present invention is used as a transmissive screen, it can also be used as a configuration in which a Fresnel lens or a lens sheet in which a Fresnel lens and a lateral lenticular lens are combined is used on the light source side.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A projection screen was manufactured with the apparatus shown in FIG. 3 using the nozzles shown in FIGS. 4 and 5. In the nozzle, 1000 orifices 12 having a hole diameter of 1 mm for the light-transmissive strand are annularly arranged at a pitch of 1.15 mm.
The same number of orifices 13 having a hole diameter of 0.5 mm for the light absorber are arranged between them.

Polycarbonate resin (Upilon # 2000 manufactured by Mitsubishi Gas Chemical Co., Inc.) is used for the orifice 12 in an amount of 4% by weight.
0.2 g / min was supplied to each orifice of the mixed melt containing the inorganic silica, and 4% by weight of inorganic silica and 2% by weight of carbon black were added to the orifice 13 in polymethylmethacrylate (VH manufactured by Mitsubishi Rayon Co., Ltd.). 0.02 g / min per orifice of the mixed melt
It was extruded upward at a nozzle temperature of 260 ° C. After being extruded, the annular sheet 5 formed by fusion bonding of the adjacent strands is pulled up along the inner wall of the annular guide 6 at a speed of 1.3 m / min while being planarized by the trowel-shaped guide 7 and the rod-shaped straight guide 8. Unfold it on the sheet and reel 1
It was wound up to 0. The sheet was cooled by passing warm water of 40 ° C. into each guide. In the obtained sheet, 1000 light-transmissive strands with a pitch of 0.4 mm are uniformly arranged in a plane, and a light absorber is formed between the strands, and the shape of the lens surface of each strand is It was what I wanted. Further, the adhesive strength between the light absorber and the strand was also sufficient.

The three sheets wound on the reel 10 are taken up by using the first nip roller, and the ambient temperature 14
Pass through the first far-infrared heater at 0 ° C. while extending it 1.05 times by the second nip roller,
The winding habit of the sheet was removed. Then, the ambient temperature 16
After passing through a second far-infrared heater at 0 ° C. while being stretched 1.1 times using a third nip roller,
Immediately, the three sheets were fused by a curved bar-shaped bending guide while being close to each other, and cut into a length of 1 m by a cutter.

A Fresnel lens was combined with this projection screen to form a transmissive screen, which was attached to a color projection television for observation, and an optically uniform, clear screen with no screen spots was obtained. Was given.

Example 2 Using the same nozzle and apparatus as in Example 1, 4 wt% of inorganic silica and carbon were added to polymethylmethacrylate (MD made by Mitsubishi Rayon) in which 8.5 wt% of methyl acrylate was copolymerized in the orifice 13. A sheet was produced in the same manner as in Example 1 except that the mixed melt obtained by mixing 2% by weight of black was supplied. The obtained sheet has a pitch of 0.4.
The light transmissive strands of 1,000 in mm are evenly arranged in a plane, and a slightly low convex light absorber is formed between the strands. The shape of the lens surface of each strand is as desired. there were. Further, the adhesive strength between the light absorber and the strand was also sufficient.

The obtained sheet was treated in the same manner as in Example 1 to obtain a projection screen having a length of 1 m. A Fresnel lens was combined with this projection screen to form a transmissive screen, which was attached to a color projection television for observation, and an optically uniform screen with no screen spots and a clear screen with good color tone and contrast was obtained.

Comparative Example 1 Using the same nozzle and apparatus as in Example 1, a mixture of 4 wt% of inorganic silica and 2 wt% of carbon black in polycarbonate resin (Iupilon # 2000 manufactured by Mitsubishi Gas Chemical Co., Inc.) was mixed in the orifice 13. A sheet was produced in the same manner as in Example 1 except that the melt was supplied. In the obtained sheet, 1000 translucent strands were arranged uniformly in a plane with a pitch of 0.4 mm, and a light absorber was formed between the strands. Although the adhesive strength between the light absorber and the strand was extremely high, the strand contained some strands having a gentler curvature than the desired lens shape.

The obtained sheet was treated in the same manner as in Example 1 to obtain a projection screen having a length of 1 m. A Fresnel lens was combined with this projection screen to form a transmissive screen, which was then attached to a color projection TV for observation, and dark streak-like screen spots appeared in the strands with a curvature that is gentler than the desired lens shape. The screen was optically non-uniform.

[0039]

The projection screen of the present invention has mechanical properties such as impact resistance due to the use of a polycarbonate resin as a main component in a transparent plastic strand and an acrylic resin as a light absorber as a base material. ,Heat-resistant,
It is excellent in water resistance, dimensional stability and flame retardancy, is optically uniform without screen spots, and can provide a clear image with good color tone and contrast.

[Brief description of drawings]

FIG. 1 is an enlarged perspective view showing a part of a projection screen of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of the projection screen of the present invention.

FIG. 3 is a schematic side view of an apparatus used to manufacture the projection screen of the present invention.

FIG. 4 is a schematic ejection surface view of a nozzle used for manufacturing the projection screen of the present invention.

FIG. 5 is a schematic enlarged discharge surface view showing a part of the nozzle used for manufacturing the projection screen of the present invention.

FIG. 6 is an enlarged sectional view showing a part of a conventional projection screen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 translucent strand 2 light absorber 3 extruder 4 nozzle holder 5 annular sheet of translucent strand 6 annular guide 7 trowel-like guide 8 rod-shaped straight guide 9 nip roller 10 reel 11 nozzle 12 orifice for translucent strand 13 light Orifice for absorber

Claims (2)

[Claims] 1. A projection screen in which a large number of translucent plastic strands are arranged in parallel, and adjacent strands are joined to be integrated into a sheet, and the strands are mainly composed of a polycarbonate resin. In addition, the projection screen is characterized in that a light absorber whose base material is an acrylic resin is formed between the strands. 2. The projection screen according to claim 1, wherein the acrylic resin is polymethyl acrylate obtained by copolymerizing 0 to 15% by weight of ethyl methacrylate and / or methyl methacrylate.