JPH0589827A - Photo-convergenece type back light - Google Patents

Abstract

PURPOSE:To provide a back light for small-sized display, in which light is converged on the front through effective utilization of the light from a light source. CONSTITUTION:A back light is equipped with a light source and a diffusion plate 12a for diffusing light from the source and projecting ahead uniformly, wherein a light convergence sheet 20 in the form of a micro-prism is furnished to converge the light cast diffusively from the diffusion plate 12a to the front.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for a liquid crystal display panel of an electric viewfinder (EVF) of a VTR or a display of a camcorder (trade name), and more particularly to a backlight for a small display.

[0002]

2. Description of the Related Art As an example of a conventional display backlight, there is a straight tube reflector system shown in FIG. In this system, as shown in the figure, a straight tube fluorescent lamp 40 is used as a light source, and the straight tube fluorescent lamp 40 is surrounded by a reflecting plate 42 from the rear side, and light is projected forward. On the other hand, straight tube fluorescent lamp 40
A diffusing plate 44 is disposed in front of, and irradiates the front while diffusing the projected light.

A flat fluorescent lamp type backlight shown in FIG. 8 is intended to save space in comparison with the straight tube reflecting type backlight. In this structure, two electrodes 16 are inserted into a thin rectangular parallelepiped main body 12 formed by laminating glass or glass and ceramics, and a chip 18 for injecting gas into the main body 12 is formed. Is attached. Although not shown, a fluorescent paint is applied to the inner surface of the main body 12. The front glass of the main body 12 is treated for diffusion in the form of frosted glass.

There is also a backlight of a light guide plate type. Each of these backlights employs a method of diffusing light from a light source in order to make the luminous intensity uniform. In addition, a display having a large screen generally requires a somewhat large viewing angle to be used, and therefore a diffusion method is indispensable for expanding the light of the backlight.

[0005]

However, in the case of a color EVF that can be seen only from the front or a small display, for example, a display having a size of about 3 inches or less, one operator of the apparatus can view it from the front. It is only necessary to be able to see, and the light emitted from the backlight peripheral portion 12b due to the diffusion of the light escapes to the side and becomes useless light. Therefore, this backlight peripheral part 12b
There is also a problem that the peripheral area of the display corresponding to is dark. A larger backlight is needed to brighten the periphery of this display.

[0006] Therefore, an object of the present invention is to provide a backlight for a small-sized display in which light from a light source is effectively used to collect light on the front surface.

[0007]

In view of the above object, the present invention provides a backlight having a light source and a diffuser plate for diffusing light from the light source to uniformly illuminate the front. A condensing type backlight provided with a microprism-shaped condensing sheet for condensing light diffused from a plate in a front front direction.

[0008]

The light emitted from the light source is projected forward by the diffuser plate with a uniform light intensity, and the light projected forward is diffused not only in the front but also in an oblique direction due to the diffusion. The light that has spread in the direction is condensed in the front front direction by the microprism-shaped condensing sheet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on the embodiments shown in the accompanying drawings. First, referring to FIG. 3 and FIG. 4, the condensing type backlight according to the present invention has a structure in which a micro prism-shaped condensing sheet 20 is attached to the front surface of the above-mentioned flat fluorescent lamp type backlight. . That is, the two electrodes 1 are attached to the main body 12 of the rectangular parallelepiped shape made of glass.
6 is inserted, and a tip 18 for injecting gas is attached inside. The front glass 12a of the glass body 12 is treated for diffusion in the form of frosted glass, and the inner surface 14 of the body 12 is further coated with a fluorescent paint.

This thin plate-shaped backlight is based on the electrode 1 described above.
When voltage is applied to 6, fluorescence is emitted.

A microprism-shaped light collecting sheet 20 is attached on the front glass 12a. FIG. 1 shows an enlarged view of a state in which the microprism-shaped light collecting sheet 20 is attached to the front glass 12a. The micro prism-shaped light collecting sheet 20 is fixed to the diffusion front glass 12a through a transparent adhesive 22, and the light passing through the diffusion front glass 12a receives the adhesive 22 and the micro prism light collecting sheet. After passing through 20, the front liquid crystal display panel 28 is illuminated from the rear.

As shown in the plan view of FIG. 5, the micro-prism-shaped light-condensing sheet 20 has a large number of equilateral triangular pyramids 20a surrounded by equilateral triangular faces. An example of the length l of one side of the regular triangular pyramid 20a is 170 μm. Light that has passed through the front glass 12a and the adhesive 22 enters each regular triangular pyramid 20a as shown in FIG. 2 and is refracted when emitted to the outside atmosphere. This micro-prism-shaped light-condensing sheet 20 is made of polyvinyl chloride, and since its refractive index is larger than that of air, it bends as shown in FIG. 2, and as a result, diffused light is emitted in the front front direction of the backlight. Collects light.

An alternate long and two short dashes line 24 in FIG. 3 indicates an effective light emitting area of a flat fluorescent lamp type backlight.
The length of this diagonal line is 17.78 mm (0.7 inches), and the present invention is suitable for a small-sized backlight having a diagonal dimension of about 76.2 mm (3 inches) or less.

The microprism-shaped light collecting sheet 20 covers this region 24. Therefore, the front glass 1 for diffusion
All the light that has diffused from the periphery of the light emitting region 24 through 2a and is emitted forward or diagonally sideways is condensed in the frontal front direction and leaks diagonally laterally without illuminating the liquid crystal display panel 28 in front. The collected light can be collected to effectively illuminate the liquid crystal display panel 28. According to one experimental result, the brightness of the liquid crystal display panel is improved by about 20%.

Therefore, the microprism-shaped light collecting sheet 2
Even if 0 is configured to cover only the peripheral portion of the light emitting region 24 without covering the entire light emitting region 24, the light leaking to the oblique side can be condensed and sent to the front front direction. That is, the light of the light source can be effectively used.

The microprisms of the microprism-shaped light collecting sheet 20 are not necessarily the regular triangular pyramid 20a, but may be the hemisphere 30a as shown in FIG.

[0017]

As is apparent from the above description, according to the present invention, the light leaked obliquely laterally from the light emitting region due to the diffusion method in the related art can be effectively used, thus improving the brightness. .. In particular, the brightness around the display is improved. Therefore, it is possible to provide a backlight for a small-sized display, in which light from a light source is effectively used to collect light on the front surface. It also saves energy and extends the battery life of the light source in things like camcorders.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a condensing type backlight according to the present invention in which a microprism-shaped condensing sheet is attached to the front surface of a flat fluorescent lamp type backlight.
4 is a cross-sectional view taken along the line AA of FIG.

FIG. 2 is an operation explanatory view of the micro-prism-shaped light collecting sheet of FIG.

FIG. 3 is a plan view of a condensing type backlight according to the present invention in which a micro prism-shaped condensing sheet is attached to the front surface of a flat fluorescent lamp type backlight.

FIG. 4 is a side view of the condensing type backlight according to the present invention taken along the line B of FIG.

FIG. 5 is a partially enlarged plan view of the micro-prism-shaped light collecting sheet shown in FIG.

FIG. 6 is a partially enlarged cross-sectional view showing another embodiment of the condensing type backlight according to the present invention.

FIG. 7 is a perspective view showing an example of a conventional backlight.

FIG. 8 is a perspective view showing another example of a conventional backlight.

[Explanation of symbols]

 12 Backlight Main Body 12a Backlight Main Body Front Glass 16 Electrode 20 Micro Prism Condensing Sheet 20a Regular Triangular Pyramid Micro Prism 22 Transparent Adhesive 28 Liquid Crystal Display Panel 30 Micro Prism Condensing Sheet 30a Hemispherical Micro Prism

Claims (1)

[Claims] 1. A backlight having a light source and a diffusing plate for diffusing light from the light source to irradiate the front evenly, wherein the light diffusing from the diffusing plate is condensed in the front front direction. A condensing type backlight provided with a micro prism-shaped condensing sheet.