JPS61182908A - Manufacture of screen for video projector - Google Patents

Abstract

PURPOSE:To enable to control a casting speed of ultraviolet curing resin freely and to dispose of the same easily for generation of bubbles, by irradiating ultraviolet rays to ultraviolet curing resin filled between a ultraviolet transmittable plate and mold through the ultraviolet transmittable plate. CONSTITUTION:Ultraviolet curing resin is defoamed within a hopper and cast into a mold 4 for a Fresnel lens in the inside of a vacuum container 1 through a resin casting pipe 15 which has been moved up to the upper part of the mold 4. After completion of casting of the ultraviolet curing resin 1A, the inside of a container is restored to a normal pressure and a ultraviolet transmittable plate 6 held by a vacuum pincette 14 is put over the ultraviolet curing resin 1A so that air is not involved in. In addition to the above, when bubbles are mixed with the resin at the time of casting, defoaming can be performed by depressurizing the inside of container 11 lower than the pressure at the beginning. The ultraviolet curing resin 1A is made to cure by irradiating ultraviolet rays to the same through the upper part of the plate 6 finally by a ultraviolet- light irradiation equipment 5 and molded into a shape of the mold 4 for the Fresnel lens. Demolding is performed by removing the above plate 6 after the molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an improvement in a method of manufacturing a transmission screen used in a video projector or the like.

[Conventional technology]

3(a) is a front view of a Fresnel lens as a general transmission screen, and FIG. 3(b) is a sectional view taken along the line [b-1b in FIG. 3(a).

In the figure, (11 is a Fresnel lens, (2) is a lens surface, and (3) is a non-lens surface.

Fresnel lenses like this are manufactured by hot pressing thermoplastic acrylic resin, etc. Conventionally, these methods were manufactured by molding heated acrylic resin with a mold, cooling it, and then releasing it from the mold. .

However, in the above process, cooling C after heating: Therefore, in the case of acrylic resin, for example, a circular Fresnel lens of φl O0011m+, the non-lens surface (3) strongly clamps the mold. It happened. In addition, slow cooling was required to prevent distortion during cooling, and one step took more than 60 minutes.

As a result, it becomes very difficult to release the mold, and the time required for exclusive use of the mold is long, resulting in poor productivity.

For this reason, various manufacturing methods are being considered in order to obtain a Fresnel lens that does not use hot pressing and has the same performance as a Fresnel lens manufactured by a manufacturing method that uses hot pressing.

FIG. 4 is a cross-sectional configuration diagram showing a conventional Fresnel lens manufacturing method. In the figure, (4) is a mold for a Fresnel lens, (51 is an ultraviolet irradiation device, (61 is an ultraviolet transmitting plate, (7) is an injection direction of ultraviolet curable resin, (81 is an injection port, (9) is the exhaust port, and σa is the exhaust direction.

Mold with lens surface mold (4) and ultraviolet transparent plate +6
1 is evacuated from the exhaust port +91 by a vacuum pump (not shown), and the injection port (8) is evacuated.
A UV curable resin is injected into the plate (61) and UV rays are irradiated from the upper part of the plate (61) by an ultraviolet irradiation device 151C to cure the UV curable resin and molded into the shape of the Fresnel lens mold (41). After:: The plate (61) is removed and released from the mold.

[Problem that the invention seeks to solve]

In the conventional manufacturing method described above, the use of ultraviolet curable resin eliminates the need for heating and slow cooling during manufacturing, making it possible to complete one process in a shorter time than with the hot press method. However, during manufacturing (it was necessary to install an inlet and an exhaust port in advance). Furthermore, since connection with a vacuum pump and hopper is required, connection pipes and connection methods for these are required. The injection speed is determined by the diameter of the exhaust port (provided that the accuracy and pressure are constant), but with resin injection methods that use a pipe-shaped injection port, there is a natural limit to the injection speed, and if bubbles are mixed in during injection. There was a problem in that it was difficult to remove bubbles from the exhaust port, and that rework C: required a great deal of time and effort.

The present invention was made to eliminate such problems, and provides a method for manufacturing a screen for a video projector in which the injection speed can be freely controlled and the generation of bubbles can be easily dealt with. This is what I am trying to do.

[Means for solving problems]

The method for manufacturing a video projector screen of the present invention includes injecting an ultraviolet curable resin under reduced pressure into a mold for a video projector screen having a lens surface mold, and covering the resin with an ultraviolet transparent plate. The ultraviolet curable resin filled between the plate and the mold is cured by irradiating ultraviolet rays through the ultraviolet transparent plate, and the cured ultraviolet curable resin is released from the mold to obtain a screen for a video projector.

[Effect]

In this invention, a direct injection port is provided in the screen mold.
Since there is no need to provide an exhaust port, the injection speed can be controlled freely, and there is no need to connect the injection port and exhaust port directly to the hopper and vacuum pump, respectively. Since it can be degassed (there is no need to degas it through an exhaust port), rework is easy and productivity is improved.

〔Example〕

A method for manufacturing a Fresnel lens using an ultraviolet curable resin according to an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are cross-sectional configuration diagrams showing the method of manufacturing this Fresnel lens in order of steps. In the figure, (IA) is an ultraviolet curable resin, (11) is a vacuum container, α is a gasket, θ9 is a supply and exhaust port, and (14) is a vacuum pincer l-
1 (151 is a resin injection tube.

First, as shown in Fig. 1, a Fresnel lens mold (4) having a mold for the lens surface and an ultraviolet-transparent plate (61) are placed in a vacuum container I, which is evacuated by a vacuum pump (not shown). The pressure inside the container (II) is reduced to 10 Torr.

Next, the ultraviolet curable resin is degassed in a hopper (not shown) and injected into the Fresnel lens mold (4) in the vacuum container (11) through the resin injection tube (15) that has moved above the mold (4). The amount of injection should be such that it rises to the top of the mold due to the surface tension of the resin. When (6) is covered, bubbles will be drawn in.

Also, a Fresnel lens mold 14 placed inside the vacuum container αυ
The necessary condition for + is that it be placed almost horizontally. After the injection of the ultraviolet curable resin (IA) is completed, the resin injection tube (19) is withdrawn, the inside of the container is returned to normal pressure, and the ultraviolet transparent plate (6) held by the vacuum tweezers α4 is injected with the ultraviolet curable resin. (IA) Top C: Cover it so as not to trap bubbles (air).At this time, use ultraviolet curable resin (IA).
Since it was returned to normal pressure from a vacuum, the pressure of 1 atmosphere is heated up, and the resin is apparently not affected by that pressure. Therefore, if you do not inject a little more resin (according to the surface tension) into the Fresnel lens mold (4) when covering the UV transmitting plate (61), the UV transmitting plate (6) and the UV curable resin (IA) will not be injected. This results in air being drawn into the interface between the resin and the resin.Also, if bubbles are mixed into the resin during injection, they can be removed by reducing the pressure in the inner chamber of the reactor even further than the initial pressure. The plate (6) may be covered with ultraviolet curable resin (IA)≦: It may be done either inside the vacuum vessel aυ or outside the vessel, and finally, as shown in Figure 2, ultraviolet rays are applied from the top of the plate (6). Irradiation device (5)C
2) The above ultraviolet curable resin (IA) is irradiated with ultraviolet light.
) is cured and molded into the shape of a Fresnel lens mold (4). After molding, the plate (61) is removed and the mold is released.

The Fresnel lens thus obtained satisfied the same properties as those obtained using a conventional mold.

Further, in the above embodiment, a case was described in which a Fresnel lens was manufactured as a method for manufacturing a screen for a video projector, but a lenticular lens can be obtained by using a mold with a lenticular lens surface, and furthermore, a lenticular lens can be obtained. By shaping the surface of the plate facing the lens surface into a suitable lens surface type, a screen having Fresnel lens surfaces and lenticular lens surfaces on both sides can be obtained in the same manner as in the above embodiment.

〔Effect of the invention〕

As explained above, this invention involves injecting an ultraviolet curable resin under reduced pressure into a mold for a video projector screen having a lens surface mold, covering it with an ultraviolet transparent plate, and combining the ultraviolet transparent plate and the mold. By irradiating the UV curable resin filled in the space with UV rays through the UV transparent plate and curing it, and then releasing the cured UV curable resin from the mold, it is no longer necessary to attach an injection port and an exhaust port in advance during manufacturing. In addition, it eliminates the need to connect those connecting pipes, and it also simplifies injection, makes it easier to control the injection speed, and allows for quick response to bubble contamination, making it possible to assemble video projector screens with high productivity. It has the effect of being manufacturable.

Ru.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional configuration diagrams showing the manufacturing method of a Fresnel lens according to an embodiment of the present invention in the order of steps.
The figure shows the resin injected, and FIG. 2 shows the resin cured. Figure 3(a) is a front view of a typical Fresnel lens;
Figure (t)l is lb - Wb H in Figure 3 ta+,
f (side view, Figure 4 is a cross-sectional configuration diagram showing the conventional Fresnel lens manufacturing method. In the figure, (IA) is an ultraviolet curable resin, and (4) is the gold of a video projector screen (Fresnel lens). A mold, (5) is an ultraviolet irradiation device, (6) is an ultraviolet transmitting plate, αυ is a vacuum container, and (19 is a resin injection tube. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] (1) Injecting ultraviolet curable resin under reduced pressure into a video projector screen mold having a lens surface mold,
Covered with a UV-transparent plate, the UV-curable resin filled between the UV-transparent plate and the mold is cured by irradiating the UV-curable resin through the UV-curable plate, and the cured UV-curable resin is released from the mold. A method of manufacturing a screen for a video projector. (2) A method for manufacturing a screen for a video projector according to claim 1, wherein the lens surface is a Fresnel lens surface; (3) The method for manufacturing a screen for a video projector according to claim 1, wherein the lens surface is a lenticular lens surface. (4) The method for manufacturing a screen for a video projector according to claim 2, wherein the surface of the ultraviolet-transparent plate facing the lens is a lenticular lens surface.