JP2000214533A - Transmission screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission screen that deflection in the screen caused by the peripheral environmental change can be restrained to a minimum and an optimum picture is always displayed while improving adhesion between respective lens sheets such as a lenticular lens sheet, a Fresnel lens sheet, or a prism lens sheet. SOLUTION: As to this transmission screen constituted of plural sheets including the Fresnel lens sheet 1a, and the lenticular lens sheet 1b, and attached to a rear projection video display device so that the respective sheets are brought into close contact with each other, the thickness of the sheet that is the largest among the plural sheets is >=2 mm, the warping of the sheet in a state where the sheet having the largest thickness is not restrained is <=5 mm, the coefficient of saturated water absorption of the thickest sheet is <=1%, and warping of the transmission screen is <=5 mm in a state where the transmission screen is attached to the rear projection video display device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive screen for a rear projection type video display device in which an image from a projection device is projected from the back of the screen, and has a large number of pixels such as a liquid crystal panel and a DMD. This is a transmission type screen suitably used for a rear projection type video display device provided with a single lens type projection device using an image panel.

[0002]

2. Description of the Related Art In recent years, a rear projection type video display device equipped with a single lens type projection device using an image panel having a large number of pixels such as a liquid crystal panel and a DMD has been actively developed. In this projection device, an image panel such as a liquid crystal panel or a DMD does not emit light by itself, but of light emitted from a light source disposed on the back side of the image panel, light modulated by the image panel and transmitted therethrough passes through a magnifying lens. Projected onto the screen. FIG. 3 shows a schematic configuration diagram of an example of a rear projection type video display device including a single lens system projection device using a liquid crystal panel or the like. The transmission screen used in the conventional rear projection type image display device shown in FIG. 3 includes a Fresnel lens sheet 1a, a lenticular lens sheet 1b, and a front plate 1c. A divergent light beam from an image source 2 composed of a light source, an image panel and the like is projected from one surface of a Fresnel lens sheet 1a having a Fresnel lens formed on the surface of a transparent resin plate, and this image light beam is transmitted to the Fresnel lens sheet 1a. Is converted into a parallel light beam or a convergent light beam. The parallel light beam or the convergent light beam transmitted through the Fresnel lens sheet 1a is transmitted through a lenticular lens sheet 1b formed on both sides of a convex lens which is repeatedly formed in a horizontal direction.
By b, the horizontal viewing angle on the observation side is enlarged to create a projection image. The front plate 1c functions to protect the lenticular lens sheet 1b and the like.

Normally, a diffusing agent composed of fine particles such as quartz, glass, cross-linked polymer resin or the like is dispersed in the lenticular lens sheet 1b, whereby the viewing angle in the horizontal direction as well as in the vertical direction is expanded. . Similarly, a diffusing agent may be dispersed in the Fresnel lens sheet 1a in order to increase the horizontal and vertical viewing angles. FIGS. 4 and 5 are schematic diagrams showing another example of a rear projection type video display device provided with a single lens system projection device using a liquid crystal panel or the like. The rear projection type video display device shown in FIG. In FIG. 5, a prism lens sheet 1d is disposed for the purpose of improving the directivity of a projected image. In the rear projection type image display device shown in FIG. 5, a reinforcing plate 1e is disposed for increasing structural strength.

[0004] Each sheet constituting the transmissive screen of the rear projection type image display device is generally made of a synthetic resin, and the ambient temperature and humidity change during use.
The sheets constituting the transmission type screen may expand and contract due to the influence of distortion or the like remaining during sheet production, and the screen may be bent or a gap may be generated between the sheets constituting the screen. This causes image defects such as a decrease in resolution. In order to solve the problem such as the bending of the screen due to such changes in the ambient temperature and humidity,
A technology for the screen mounting structure to absorb the expansion and contraction of each sheet, at least one of the sheets constituting the screen is formed into a curved shape in advance, and the space between each sheet is made using the elastic force of the sheet. Technology to prevent the occurrence of floating by making close contact (Japanese Utility Model Application Laid-Open No.
And Japanese Patent Application Laid-Open No. 9-15727) have been developed.

[0005]

A liquid crystal panel or the like is used as compared with a CRT type rear projection type video display device having a projection device using three light valves corresponding to three colors of R, G and B. In a rear projection type video display device provided with a projection device of a single lens system, it is difficult to perform electrical processing in order to correct distortion between a central portion and a peripheral portion. For this reason, a technique of preventing the sheet constituting the screen from floating by keeping the sheet constituting the screen curved has been proposed for a rear projection type video display apparatus equipped with a single lens type projection apparatus utilizing a liquid crystal panel or the like. When applied to a transmissive screen, image distortion and defocus due to screen curvature and the like are likely to occur. Further, in a rear projection type video display device provided with a projection device of a single lens system, since the depth of focus is shallow, an image is easily blurred when the screen is bent due to expansion and contraction due to a change in temperature and humidity. If a rear-projection image display device equipped with a single-lens projection system is used for applications that require high-definition images such as computer screens, the effects of distortion, defocus and blurring of these images will occur. Is particularly large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a plurality of sheets such as a lenticular lens sheet, a Fresnel lens sheet, and a prism lens sheet. For the transmission screen with each sheet warped, the distortion and defocus of the image are eliminated, and the bending of the screen due to the temperature and humidity changes of the surrounding environment during use is minimized. An object is to provide a screen capable of displaying an image.

[0007]

A transmission screen according to the present invention for solving the above-mentioned problems comprises a plurality of sheets including a Fresnel lens sheet and a lenticular lens sheet, and is mounted on a rear projection type image display device. A screen, wherein the largest sheet thickness of a plurality of sheets attached to the rear-projection image display device in close contact with each other is 2 mm or more, and the largest sheet thickness is not restricted. In this state, the warpage of the sheet was 5 mm or less, the sheet having the largest thickness had a saturated water absorption of 1% or less, and the transmission screen was mounted on a rear projection type video display. In this state, the size of the warp of the transmission screen is 5 mm or less. Here, the magnitude of the warpage in a state where the sheet is not restrained in the present specification means that the sheet is gradually lowered from a state in which one end of the sheet is supported and is hung down, toward an appropriate board, and Assuming a straight line connecting the upper end and the lower end of the sheet with the lower end hitting the board, the point on the sheet farthest from the straight line (the point inside the warped sheet) and the point It means the distance from the straight line (the above distance is indicated by L in FIG. 2 when the sheet is viewed from the lateral direction). The direction of the warp may be on either the short side or the long side. Either the observer side may be warped so as to be concave or the observer side may be warped so as to be convex. Note that the saturated water absorption is ASTM.
D is a value measured by the method specified in 570.

In the present invention, the thickness of the lenticular lens sheet constituting the transmission screen is set to TL (mm).
When the plate thickness of the Fresnel lens sheet is represented by TF (mm), TL and TF satisfy TF / TL> 1.
Satisfying the relationship of 3 is effective because the deterioration of the image due to the bending of the screen can be further suppressed.

In the present invention, the transmission type screen is composed of a Fresnel lens sheet and a lenticular lens sheet.
When composed of two sheets, it is preferable that the thickness of the Fresnel lens sheet is larger than the thickness of the lenticular lens sheet, and the size of the warp of the lenticular lens sheet in an unconstrained state is 80 mm or more. Is preferred.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described below. As described above, in a rear projection type video display device including a single lens system projection device using a liquid crystal panel or the like, it is difficult to perform electrical processing to correct distortion between the central portion and the peripheral portion. When the size of the warp of the transmission type screen is set to 5 mm or less in a state where the transmission type screen is attached to the rear projection type image display device according to the present invention, image distortion and defocus due to excessive curvature of the screen. Can be eliminated. Further, for a sheet having a maximum thickness of 2 mm or more, the magnitude of the warpage of the sheet in an unconstrained state is 5 mm or less, and the saturated water absorption of the sheet is 1%.
With the following, a single lens system projection device having a feature that the screen can expand and contract by absorbing or releasing moisture and the position of the screen can be reduced, and the depth of focus is shallow. It is possible to eliminate blur of an image of the rear projection type video display device. The sheet having the largest thickness preferably has a saturated water absorption of 0.8% or less.

The transmissive screen of the present invention is not limited to a screen composed of two sheets, a Fresnel lens sheet and a lenticular lens sheet, but also a Fresnel lens sheet and a lenticular lens sheet as shown in FIG. , A front plate is added, a prism lens sheet is added to both sheets as shown in FIG. 4, and a reinforcing plate is added to both sheets as shown in FIG. Is also included.
When a front plate or a reinforcing plate is added to the Fresnel lens sheet and the lenticular lens sheet to form a transmission screen, the front plate or the reinforcing plate may be installed separately from the lenticular lens sheet or the Fresnel lens sheet. In such a case, among the Fresnel lens sheet and the lenticular lens sheet, the larger thickness of the sheet is 2 mm or more, and the warpage of the sheet in an unconstrained state is 5 mm or less. Water absorption is 1% or less.

[0012]

The present invention will be specifically described below with reference to examples. FIG. 1 is a schematic longitudinal sectional view of an example of a transmission screen according to the present invention before assembling. This transmission screen 1 is composed of two sheets, a Fresnel lens sheet 1a and a lenticular lens sheet 1b. The Fresnel lens sheet used in the test had a plate thickness of 2.15 mm (a Fresnel lens formed of a 0.15 mm-thick 2P resin layer was formed on a plate made of an acrylic styrene copolymer resin having a plate thickness of 2 mm). The saturated water absorption is 0.8%.), And it has a warp of 3 mm in an unconstrained state. The lenticular lens sheet is made of an acrylic resin, has a thickness of 0.95 mm, and has a warp of 80 mm in an unrestricted state. That is, the Fresnel lens sheet corresponds to the sheet having the largest thickness in this transmission screen. Immediately after this transmission screen is attached to the frame of the rear projection type image display device so that the size of the warp is 4 mm, and at 40 ° C., 90% R.C.
H. Table 1 shows the results of image evaluation of each image after being left for 24 hours under high humidity. Table 1 shows the magnitude of the warpage of the Fresnel lens sheet (Examples 2 and 4), the saturated water absorption of the Fresnel lens sheet (Example 3), or the transmission screen when mounted on the frame of the rear projection type image display device. The results of image evaluation are shown together with the warpage (Examples 2 to 4) different from that of Example 1. Further, the magnitude of the warpage of the Fresnel lens sheet and the magnitude of the warpage of the transmission screen when attached to the frame of the rear projection type image display device (Comparative Example 1),
Table 1 also shows the results of image evaluation for the case where the plate thickness of the Fresnel lens sheet (Comparative Example 2) or the saturation water absorption of the Fresnel lens sheet (Comparative Example 3) was out of the range of the present invention. Shown in

[0013]

[Table 1]

The warpage of the Fresnel lens sheet alone is 5 m
m or less, the image did not have a problem even after being left under high humidity, but the Fresnel lens sheet alone had a large warp of 7 mm, and the comparative example 1 had a large warp when mounted. Immediately after being mounted on the frame of the projection type image display device, the image quality in the peripheral portion was slightly inferior, and after leaving the device under high humidity, the image quality was significantly reduced. In Comparative Example 2 in which the plate thickness of the Fresnel lens sheet was small, there was no problem in the image quality immediately after the Fresnel lens sheet was mounted on the frame of the rear projection type image display device. The decline was significant. In Comparative Example 3 in which the composition ratio of the acrylic styrene copolymer resin as the base resin of the Fresnel lens sheet was changed to change the saturated water absorption to 1.3%, the same as in Comparative Example 2, after being left under high humidity. The warpage increased and the image quality was significantly reduced.

As shown in FIG. 4, the transmission screen of the present invention is composed of three lenticular lens sheets, a prism lens sheet and a Fresnel lens sheet (Examples 5 and 6). As shown in FIG. 3, in the case of three lenses (a lenticular lens sheet, a Fresnel lens sheet, and a front plate) (Examples 7 and 8), the conditions such as plate thickness and warpage of each sheet and the results of image evaluation are shown. It is shown in FIG. Here, Example 5
In Nos. 6 and 7, the lenticular lens sheet, the prism lens sheet and the Fresnel lens sheet are set in the rear projection type image display device so as to be in close contact with each other, and the prism lens sheet corresponds to the sheet having the largest thickness. In Examples 7 and 8, the lenticular lens sheet, the Fresnel lens sheet and the front plate are set in the rear projection type image display device so as to be in close contact with each other, and the front plate corresponds to the sheet having the largest plate thickness. As shown in Table 2, in each of the configurations, the image of the transmission screen of the present invention was good immediately after setting and after being left at high humidity.

[0016]

[Table 2]

[0017]

According to the present invention, it is possible to obtain a transmissive screen which is less likely to be deformed due to moisture absorption and desorption and has a small decrease in image quality due to changes in temperature and humidity.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a transmission screen of the present invention.

FIG. 2 is a diagram illustrating a measurement point of a warpage of a transmission screen.

FIG. 3 is a schematic perspective view of an example of a rear projection type video apparatus to which the present invention is applied.

FIG. 4 is a schematic perspective view of another example of a rear projection type video device to which the present invention is applied.

FIG. 5 is a schematic perspective view of another example of the rear projection type video apparatus to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmissive screen 2 ... Image source 1a ... Fresnel lens sheet 1b ... Lenticular lens sheet 1c ... Front plate 1d ... Prism lens sheet 1e ... Reinforcement plate

Claims (4)

[Claims] 1. A transmissive screen comprising a plurality of sheets, including a Fresnel lens sheet and a lenticular lens sheet, attached to a rear projection type video display, and attached to the rear projection type video display so as to be in close contact with each other. The thickness of the sheet having the largest thickness among the plurality of sheets is 2 mm or more, and the size of the warp of the sheet in a state where the sheet having the largest thickness is not restrained is 5 m.
m or less, the largest sheet thickness of the sheet having a saturated water absorption of 1% or less, and the size of the warp of the transmission screen in a state where the transmission screen is attached to the rear projection type image display device. A transmissive screen having a thickness of 5 mm or less. 2. A lenticular lens sheet having a thickness T
L (mm), the thickness of the Fresnel lens sheet is TF (m
m), TL and TF are TF /
2. The transmission screen according to claim 1, wherein a relationship of TL> 1.3 is satisfied. 3. The Fresnel lens sheet according to claim 1, wherein the sheet having the largest thickness among the plurality of sheets is a Fresnel lens sheet.
The transmission screen as described. 4. The transmissive screen according to claim 3, wherein the size of the warp of the lenticular lens sheet in an unconstrained state is 80 mm or more.