JPH05346510A - Lighting device for liquid crystal - Google Patents

Abstract

PURPOSE:To increase the total quantity of light by adding light emitted from coloring pigment to the quantity of light from a light source by interposing the coloring pigment in a light guide plate. CONSTITUTION:This lighting device is equipped with the light guide plate 11 which is arranged behind a liquid crystal display plate 10 in parallel, light sources 12 arranged on both end parts of the light guide plate 11, and a diffusion plate 13 which diffuses the forward light from the light guide plate 11 to the liquid crystal display plate 10, and coloring pigment films (fluorescent film) 14a and 14b which have a small overlap between light emission wavelength and light absorption wavelength are formed on the front surface and rear surface of the light guide plate 11. This light guide plate 11 is formed of a light-transmissive material such as polymethyl acrylate(PMMA) resin in a flat plate shape; and two side end surfaces of the light guide plate 11 serve as light incidence end surfaces where the lights from the light sources 12 are made incident and high reflecting films are formed on two side end surfaces other than the light incidence end surfaces. The lights from the light sources 12 are entered into the light guide plate 11 and when the lights irradiate the reverse surface of the liquid crystal display plate 10 through the diffusion plate 13, the coloring pigment films 14a and 14b emit lights, so that the quantity of light increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate light guide type illuminating device arranged on the back surface of a light receiving type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, as a back lighting device (backlight) of a liquid crystal display device, polymethylmethacrylate (PMMA) has been demanded as it is required to be thinner.
A light source 2 is arranged on at least one side end of a light guide plate 1 using a light transmissive material such as, and a light scattering material 3 for effectively scattering light is pattern printed on the back surface of the light guide plate 1, Further, a reflection film 4 is provided on the rear surface thereof, and a diffusion film 5 is provided in order to improve the uniformity of the light emitted from the light guide plate 1 as surface brightness (hereinafter referred to as “uniformity”). A light guide plate (light guide) type structure in which a light source reflector 6 (reflector sheet) is provided in order to effectively allow the light emitted from the light source 2 to enter the light guide plate 1 is generally used.

[0003]

In the conventional light guide plate type backlight, it is necessary to reduce the thickness of the light guide plate 1 as thinning is required. But then
Since the light from the light source 2 is incident from the end surface of the light guide plate 1, the light incident area is proportionally reduced, and the display surface becomes low in brightness as the amount of light is reduced. This is contrary to the demand for higher brightness.

In view of the above problems, it is an object of the present invention to provide a liquid crystal lighting device that can achieve high brightness even if the light guide plate is made thin.

[0005]

The means for solving the problems according to the first aspect of the present invention is to illuminate the liquid crystal display panel 10 from the rear side as shown in FIGS. In a liquid crystal lighting device including a light guide plate 11 arranged and a light source 12 arranged at an end of the light guide plate 11, the light guide plate 11 is provided with a luminescent pigment 14a having a small overlap between an emission wavelength and an absorption wavelength. , 14b, 14c are interposed.

As shown in FIGS. 4 and 5, the means for solving the problem according to the second aspect of the present invention is to illuminate the liquid crystal display plate 10 from the rear side, and the light guide plate 11 arranged in parallel behind the liquid crystal display plate 10. And a light source 12 arranged at the end of the light guide plate 11, in the liquid crystal lighting device, a luminescent dye 14c having a small overlap between the emission wavelength and the absorption wavelength is mixed inside or on the surface of the light guide plate 11. Or it is attached.

According to a third aspect of the present invention, as shown in FIG. 2, among the end faces 11a and 11b of the light guide plate 11 according to the first or the second aspect, a surface 11b other than the light incident end face 11a is raised. The reflection film 16 is formed.

[0008]

In the means for solving the problems according to the first and second aspects, the light from the light source 12 is made incident on the inside of the light guide plate 11 and is radiated to the back surface of the liquid crystal display plate through the diffusion plate 13.

At this time, the luminescent dye films 14a and 14b or the luminescent color material 14c emit light, and the amount of light increases.

In the problem solving means according to the third aspect, the light incident from the light incident end surface 11a of the light guide plate 11 is reflected by the high reflection film 16 on the other surface 11b, so that the light loss here is reduced.

[0011]

【Example】

(First Embodiment) FIG. 1 is a sectional view showing a first embodiment of a liquid crystal lighting device of the present invention, FIG. 2 is a plan view of a light guide plate and a light source,
FIG. 3 is a diagram showing the characteristics of the emission spectrum and the absorption spectrum of the luminescent dye film.

As shown in the figure, the liquid crystal lighting device of this embodiment illuminates the liquid crystal display plate 10 from the rear by a light guide plate (light guide) system, and is arranged in parallel behind the liquid crystal display plate 10. The light guide plate 11, a light source 12 arranged at both ends of the light guide plate 11, and a diffusion plate 13 for diffusing the light from the light guide plate 11 to the liquid crystal display plate 10. Luminescent dye films 14a and 14b (fluorescent films) having a small overlap between the emission wavelength and the absorption wavelength are formed on the front surface and the rear surface.

As shown in FIGS. 1 and 2, the light guide plate 11 is formed in a flat plate shape using a translucent material such as polymethylmethacrylate (PMMA) resin. The two-side end surface 11a of the light guide plate 11 is a light-incident end surface on which light from the light source 12 is incident, and the two-side end surface 11b other than the light-incident end surface 11a.
A high reflection film 16 (high reflection film) is formed on the. On the back surface of the light guide plate 11, a light scattering material 17 such as TiO ₂ having a function of a light scattering effect is pattern-printed, and a high reflection film 18 is formed on the rear surface of the light scattering material.

As the light source 12, for example, a straight tube type cold cathode tube or a hot cathode tube having a diameter of 4.1 mm is used.
Around the light source 12, as shown in FIG. 1, an existing light source reflector 15 (reflector sheet) that reflects light from the light source 12 to the outside toward the light guide plate 11 is attached.

As the diffusion plate 13, a light-white polycarbonate (PC) film is used as shown in FIG.
It is formed in the same area as 1.

The luminescent dye films 14a and 14b are shown in FIG.
For example, the following dyes are used as those having the spectral characteristic of.

[0017]

[Chemical 1]

In FIG. 3, L1 is the absorption spectrum and L1 is
2 shows the emission spectrum. Both spectra L1,
It can be seen that the L2s have different wavelength characteristics and therefore do not substantially overlap. Therefore, the emitted light is not reabsorbed and is efficiently emitted.

In the above structure, the light from the light source 12 is
The light is incident from the light incident end surface of the light guide plate 11 to the inside thereof and repeats total reflection inside the light guide plate 11.

At this time, the light emitting dye films 14a and 14b are also irradiated with light. Then, depending on the amount of light from the light source 12,
Light emitted from the light-emitting dye films 14a and 14b is added, and the total amount of light greatly increases according to the intensity of incident light.

If there is a large overlap between the emission spectra and absorption spectra of the luminescent dye films 14a and 14b, the emitted light will be absorbed again by the surrounding dyes, and the emitted light will be used as a whole. The efficiency will be reduced. However, in this embodiment, as shown in FIG. 2, since the overlapping of the emission wavelength and the absorption wavelength of the light emitting dye film 14 is reduced, it is possible to prevent the light from the light emitting dye films 14a and 14b from being reabsorbed. ..

Further, since the high reflection film 16 is provided on the end surface 11b other than the light incident end surface 11a of the light guide plate 11, it is possible to suppress the light loss here and improve the light utilization efficiency.

After that, the light in the light guide plate 11 is distributed to the diffusion plate 13, and the light, which is almost evenly distributed, is applied to the back surface of the liquid crystal display plate 10 via the diffusion plate 13.

Then, the luminescent dye films 14a, 1 are formed.
The action of 4b and the high reflection film 16 makes it possible to realize a high brightness backlight system with a reduced thickness.

(Second Embodiment) FIG. 4 is a sectional view showing a second embodiment of the liquid crystal lighting device of the present invention, and FIG. 5 is a schematic view showing an optical path of the second embodiment.

The liquid crystal lighting device of this embodiment is provided with a light guide plate 11.
The luminescent color material 14c in which the emission wavelength and the absorption wavelength do not overlap each other is mixed in the inside.

In this embodiment, assuming that the refractive index of the light guide plate 11 is n, as shown in FIG. 5, the emitted light propagates to the front of the light guide plate 11 at the ratio of the following equation (1). ..

[0028]

[Equation 1]

FIG. 5 shows how the emitted light P from the luminescent color material 14c is emitted and refracted at an incident angle θ = sin ⁻¹ (1 / n).

Also in this embodiment, in addition to the amount of light from the light source 12, the total luminance can be improved because the luminescent color material 14c emits light.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, in the first embodiment, the luminescent dye film 1
Although 4a and 14b are formed on both the front surface and the rear surface of the light guide plate 11, they may be formed on only one of them.

In the first embodiment, the luminescent dye film 14 is used.
Only a and 14b are provided, and in the second embodiment, the luminescent color material 1
Although only 4c was mixed, these may be combined at the same time.

Furthermore, in both of the above embodiments, the light source 12 is arranged at both ends of the light guide plate 11, but the light source 12 may be arranged on only one side of the light guide plate 11.

[0035]

As is apparent from the above description, according to claims 1 and 2 of the present invention, since the light-emitting dye is interposed in the light guide plate, the amount of light emitted from the light source is set to the emission light from the light-emitting dye. It can be added to increase the total amount of light.

Since the overlap between the emission wavelength and the absorption wavelength of the luminescent dye is reduced, it is possible to prevent the light emitted by the luminescent dye from being reabsorbed.

Therefore, the overall brightness of the liquid crystal lighting device can be increased.

According to the third aspect, since the high reflection film is provided on the end surface other than the light incident end surface of the light guide plate, it is possible to suppress the light loss here and improve the light utilization efficiency. is there.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a liquid crystal lighting device of the present invention.

FIG. 2 is a plan view of a light guide plate and a light source.

FIG. 3 is a diagram showing characteristics of an emission spectrum and an absorption spectrum of a luminescent dye film.

FIG. 4 is a sectional view showing a second embodiment of the liquid crystal lighting device of the invention.

FIG. 5 is a schematic diagram showing an optical path of a second embodiment.

FIG. 6 is a cross-sectional view of a conventional liquid crystal lighting device.

[Explanation of symbols]

 10 Liquid Crystal Display Plate 11 Light Guide Plates 11a, 11b End Face 12 Light Source 13 Diffusers 14a, 14b Luminescent Pigment Film 14c Luminescent Color Material 15 Light Source Reflector 16 High Reflection Film

Claims (3)

[Claims] 1. A liquid crystal display for illuminating a liquid crystal display plate from the rear, comprising a light guide plate arranged in parallel behind the liquid crystal display plate, and a light source arranged at an end of the light guide plate. In the illuminating device, the illuminating device for liquid crystal, wherein the light guide plate is provided with a luminescent dye having a small overlap between an emission wavelength and an absorption wavelength. 2. A liquid crystal display for illuminating a liquid crystal display plate from the rear, comprising a light guide plate arranged in parallel behind the liquid crystal display plate, and a light source arranged at an end of the light guide plate. In the illuminating device, the illuminating device for liquid crystal, wherein a luminescent dye having a small overlap between an emission wavelength and an absorption wavelength is mixed or attached inside or on the surface of the light guide plate. 3. A liquid crystal lighting device, wherein a high-reflection film is formed on a surface of the light guide plate according to claim 1 or 2 other than the light incident end surface.