JPH0593911A - Illuminating device for liquid crystal - Google Patents

Abstract

PURPOSE:To increase a light utilization rate and to reduce weight by uniformly dispersing the heat from a light source. CONSTITUTION:Slopes 16 and insertion holes 15 are notched on the rear surface of a light transmission plate 11 to decrease the weight of the illuminating device for a liquid crystal. The light with which lateral light sources 12 are directly irradiated is reflected forward from the respective light sources 12 by the slopes 16. A reflection sheet 13 having a high heat transfer property is brought into tight contact with the light sources 12 and the heat from the light sources 12 is dissipated backward while the heat is transmitted over the entire surface of the reflection sheet 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device used for back lighting of a light receiving type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device such as a laptop computer is often used which has a thin liquid crystal illumination device (backlight mechanism). At present, these backlights include a direct type and a light guide type using a light guide plate.

(1) As shown in FIG. 6, in a direct type liquid crystal lighting device, a plurality of light sources 2 such as cold cathode tubes and hot cathode tubes are arranged directly below a liquid crystal display panel 1, and a plurality of them are arranged. A light adjusting film (lighting curtain) 3 and a diffusion plate 4 having a light diffusing function are sequentially provided in front of the light source 2. In the figure, 2a is a reflector.

(2) In the light guide type liquid crystal lighting device, as shown in FIG. 7, the light source 2 is made of a light guide plate 5 made of a translucent material.
On both sides or on one side of the light guide 2 for improving the directivity of the light emitted from the light source 2 and effectively allowing the light to enter the light incident end surface 5a of the light guide plate 5, and the light to the rear surface of the light guide plate 5. A reflection sheet 7 that guides to the emission surface and a diffusion sheet 8 that uniformizes the brightness of the illumination surface on the front surface of the light guide plate 5 are provided. In FIG. 7, 7a is a light scattering material.

[0005]

However, in the conventional direct type liquid crystal lighting device, the distance between the light source 2 and the light adjusting film 3 and the diffusing plate 4 becomes smaller, that is, as the thickness becomes thinner, the diffusing plate becomes diffusing. Light source unevenness (lamp streaks) on the surface of No. 4 occurs. This phenomenon is further promoted by the heat emitted from the light source 2, and it is an important subject to reduce the display quality of the illumination surface and to uniformly disperse the heat emitted from the light source.

Further, the light guide type liquid crystal lighting device has an advantage that it can be made thinner than the direct type liquid crystal lighting device, but the weight of the light guide plate 5 leads to a weight increase as the liquid crystal lighting device. However, it has become an important issue to realize the weight reduction while maintaining the optical characteristics.

In view of the above problems, the present invention has an object of providing a liquid crystal lighting device capable of uniformly dispersing heat from a light source, maintaining optical characteristics and realizing weight reduction.

[0008]

As shown in FIGS. 1 and 2, 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, and comprises a plurality of light sources 12 and the light sources. A light guide plate 11 arranged parallel to the liquid crystal display plate 10 so as to guide the light from the light guide plate 12 to the liquid crystal display plate 10, and a reflection sheet 13 for reflecting the backward light from the light guide plate 11 to the liquid crystal display plate 10 side. A liquid crystal lighting device having a diffusion sheet 14 for making the brightness of the illumination surface uniform over the entire surface, a semi-circular cross section in which the front semi-circular portion of each light source 12 is inserted into the rear surface of the light guide plate 11. A plurality of insertion holes 15 are formed in parallel with each other at a distance, and each light source 12 is inserted into each of the insertion holes 15 with its second half circular portion protruding rearward.
The reflection sheet 13 is closely contacted with the rear surface of the light guide plate 11 protruding rearward, and the rear surface of the light guide plate 11 is from each light source 12 to another light source 12 adjacent thereto. To the middle position, the light is emitted from each light source 12 to the side of the liquid crystal display panel 10 so as to reflect the light to the side.
Is closely related.

According to a second aspect of the present invention, in the liquid crystal lighting device according to the first aspect, the light guide plate 11 has the radius of the insertion hole 15 as r and the distance between the centers of the adjacent light sources 12 as P. The inclined top portion 16a of the inclined surface 16 is disposed at a distance of P / 2 from the center of each light source 12, and the inclined top portion 1
The notch depth dimension K1 of 6a is set so that the following equation is satisfied.

K1 ≦ (P / 2) tan {sin ⁻¹ (r / P)} In the lighting device for liquid crystal according to claim 1 or 2, the light guide plate 11 is inclined. Face 16
Further, a light scattering material 17 that scatters and reflects the light from the light source 12 on the diffusion sheet 14 is formed.

The means for solving the problem according to claim 4 of the present invention is, as shown in FIGS. 3 and 4, a light source 12 for illuminating the liquid crystal display panel 10 from the rear side, and a rearward irradiation light from the light source 12 on the liquid crystal display panel 10 side. The light source 12 includes a reflection plate 21 for reflecting light to the liquid crystal display panel 10, and a diffusion plate 22 disposed in front of the light source 12 for diffusing the direct light from the light source 12 and the reflection light from the reflection plate 21 into the liquid crystal display panel 10. A plurality of light sources 12 are arranged, and the reflectors 21 are closely contacted to the respective light sources 12. The reflectors 21 are provided with high heat conductivity, and the reflectors 21 are located at an intermediate position between the adjacent light sources 12. The liquid crystal display panel 10 emits light to the side of
The intermediate reflector 24 that reflects the light to the side is formed so as to project forward.

According to a fifth aspect of the present invention, in the liquid crystal lighting device according to the fourth aspect, the radius of the light source 12 is r, and the distance between the centers of the adjacent light sources 12 is P. 24 a of the intermediate reflector 24 is disposed at a distance P / 2 from the center of the light source 12.
The front protrusion size K2 of 4a is set so that the following equation is satisfied.

K2 ≦ r + (P / 2) tan {sin ⁻¹ (r / P)} In the liquid crystal lighting device according to any one of claims 1 to 5, a light guide plate is provided. A light scattering material 17 that scatters and irradiates the light from the light source 12 is formed at a position corresponding to the light source 12 on the front surface of 11.

[0014]

In the means for solving the problems according to the above-mentioned claims 1 to 3, the light from the light source 12 enters the inside of the insertion hole 15 of the light guide plate 11 and then diffuses in the diffusion sheet 14 in front of the light guide plate 11. Then, the back surface of the liquid crystal display panel 10 is irradiated.

At this time, the light from each of the light sources which is intended to directly irradiate the lateral light source is blocked by the inclined surface 16 of the light guide plate 11 and is effectively reflected forward. Further, at the time of reflection on the inclined surface 16, light is scattered by the light scattering material 17a, and the brightness of the illumination surface becomes uniform.

In the means for solving the problems according to claims 4 and 5, the light emitted from the light source 12 to the adjacent light source 12 side is blocked by the intermediate reflector 24 and is effectively reflected forward. The light source 12 according to claim 6
The light heading directly above is scattered by the scattering material 17b in the other directions, and the brightness of the illumination surface becomes uniform.

[0017]

【Example】

(First Embodiment) FIG. 1 is a sectional view of a liquid crystal lighting device (backlight system) showing a first embodiment of the present invention, and FIG. 2 is an enlarged view showing the same optical path.

As shown in the figure, the liquid crystal lighting device of the present embodiment illuminates the liquid crystal display panel 10 from the rear side.
A plurality of light sources 12 and a liquid crystal display panel 1 that emits light from the light sources 12.
The light guide plate 1 arranged in parallel with the liquid crystal display plate 10 so as to lead to 0.
1, a light reflection sheet 13 for reflecting the backward light from the light guide plate 11 to the liquid crystal display panel 10 side, and a diffusion sheet 14 for uniformizing the brightness of the illumination surface over the entire surface. Guide type.

As each of the light sources 12, a straight tube type hot cathode tube composed of a light emitting body such as a filament and an outer tube that covers the light emitting body is used. For example, the diameter thereof is 6.5 mm. .. The light source 12 is inserted into an insertion hole 15 of the light guide plate 11 described below so as to project rearward.

As shown in FIG. 1, the light guide plate 11 is formed of a transparent acrylic resin or the like into a substantially flat plate shape having a thickness of 6.0 mm.

On the rear surface of the light guide plate 11, there are formed a pair of insertion holes 15 having a semicircular cross section for inserting the front semicircular portion of the light source 12 from behind. The insertion hole 1
The hole diameter of 5 is substantially the same as that of the light source 12. The light source 12 is provided with the insertion hole 15 on the rear surface of the light guide plate 11.
This is because the latter half of the circle is brought into contact with the reflection sheet 13 and is separated from the light emitting surface of the light guide plate 11 as much as possible, so that the light from here is guided to the illumination surface as uniformly as possible.

Further, the rear surface of the light guide plate 11 has the respective light sources 12
From the light source 12 to the other light source 12 adjacent thereto, the light source 12 is notched forward so as to reflect the light emitted laterally from each light source 12 toward the liquid crystal display panel 10 side. Has been done.

Assuming that the radius of the insertion hole 15 is r and the distance between the centers of adjacent light sources 12 is P, the inclined top portion 16a of the inclined surface 16 is P / 2 from the center of each light source 12.
Are located at a distance of. The notch depth K1 of the inclined top portion 16a is set so that the expression (1) is established.

K1 ≦ (P / 2) tan {sin ⁻¹ (r / P)} (1) The notch depth dimension K1 of the inclined top 16a is set according to the equation (1) for each light source 12. This is because the light that is about to be directly emitted from the adjacent light source 12 is reflected forward in the middle of the light. That is, as shown in FIG. 2, the light L1 from the tube axis center point O1 of one light source 12 to the tangential direction of the light source 12 adjacent thereto is θ from the line L2 connecting the tube axis center points O1 and O2.
Phase by the angle of. This θ can be represented by θ = sin ⁻¹ (r / P) (2). Further, the light L1 at a position apart from the center point O1 by P / 2 is positioned ahead of the line segment L2 by K1 = (P / 2) tan θ (3). Therefore, the equation (1) can be obtained from the equations (2) and (3).

Further, the reason why the inclined surface 16 has a substantially arc shape is that the light from the light source 12 is reflected at an angle almost perpendicular to the irradiation surface while the light is uniformly distributed to the diffusion sheet 14 side. is there.

Then, the rear surface of the inclined surface 16 and the light guide plate 1
The light scattering material 1 which scatters and irradiates the light from the light source 12 on the diffusion sheet 14 at the position corresponding to the light source 12 on the front surface of
7a and 17b are formed. The light scattering materials 17a, 1
As 7b, white ink such as TiO ₂ or BaSO ₄ is used. The light-scattering material 17b, particularly in the front part, is pattern-printed so that the light-scattering material 17b in the front part is gradually darkened according to the center so as to finally adjust the light emitted from the light guide plate 11 to the diffusion sheet 14. ..

The light source 12 is provided on the end surface of the light guide plate 11.
It is desirable to attach a mirror-like light leakage prevention wall so as to prevent light from the outside from leaking to the outside.

As the reflection sheet 13, a specular reflection plate made of aluminum or the like having high heat conductivity is used. The reflection sheet 13 is not only adhered to the inclined surface 16 of the light guide plate 11 but also receives heat from the light source 12 in the reflection sheet 13. It is in close contact with the rear half of the light source 12 so as to conduct to the entire surface and radiate backward.

The diffusion sheet 14 is made of a synthetic resin plate such as milky white acrylic film.

The operation of the illumination device having the above structure will be described. The light from the light source 12 enters the inside from the insertion hole 15 of the light guide plate 11. After that, the incoming light irradiates the back surface of the liquid crystal display panel with light that is substantially evenly distributed from the front surface through the diffusion sheet.

At this time, the insertion hole 15 is formed in the rear surface of the light guide plate 11.
Since the light source 12 is provided and the light source 12 is incorporated therein, the light source 12 can be arranged directly below the liquid crystal display panel 10.
Therefore, the total luminous flux of the light source 12 is more effectively irradiated from the inside of the light guide plate 11 to the liquid crystal display panel 10 side as compared with the conventional case, the light utilization efficiency is improved, and a high brightness backlight system can be realized.

Moreover, since the rear surface of the light guide plate 11 is cut out to form the substantially arcuate inclined surface 16, the light from each light source 12 to be directly irradiated to the adjacent light source 12 is reflected forward in the middle thereof. Therefore, the light utilization rate can be improved as compared with a general direct type liquid crystal lighting device that does not use a light guide plate. Therefore, the brightness of the liquid crystal display panel 10 can be increased.

Here, the light guide plate 11 just above the light source 12 is provided.
Since the thickness of the light source 12 is reduced by the diameter of the insertion hole 15, the light source 12
Like the case of the direct type liquid crystal lighting device, there is a possibility that the lamp unevenness, that is, the bright and dark streaks of the lamp directly below the light source 12, may occur between the light emitting surface of the light guide plate 11 and the light emitting surface of the light guide plate 11. ..

However, in this embodiment, since the scattering material 17b is formed on the light emitting surface of the light guide plate 11 directly above the light source 12, the light traveling to the light emitting surface of the light guide plate 11 immediately above the lamp is not emitted. The light can be scattered on the light emitting surface of the light guide plate 11 other than directly above the lamp. Therefore, the brightness of the light exit surface of the light guide plate 11 directly above the light source 12 can be matched with the brightness of the light exit surface of the other light guide plates 11, and the above-mentioned uneven lamp can be prevented.

Since the light source 12 is exposed to the rear of the light guide plate 11 and the reflection sheet 13 having excellent heat conductivity is in close contact with the light guide plate 11, the heat from the light source 12 is conducted to the entire surface of the reflection sheet 13 to the rear. Can be dissipated to. Therefore, display unevenness of the liquid crystal display panel 10 due to uneven temperature distribution can be prevented at the same time.

Further, the scattering material 1 is provided on the inclined surface 16 of the light guide plate 11.
Since 7a is formed, the light guide plate 1 is provided directly below the light source 12.
Light that cannot be effectively incident on the first light can be scattered by the scattering material 17a and then reflected forward, and the uniformity of light on the illumination surface can be improved.

Further, since the light guide plate 11 is formed with a notch or an insertion hole 15 as the inclined surface 16 and the reflector at the end portion of the light guide plate used in the conventional example of FIG. The weight of the lighting device is reduced.

(Second Embodiment) FIG. 3 is a sectional view of a liquid crystal lighting device showing a second embodiment of the present invention, and FIG.
FIG.

As shown in the figure, the liquid crystal display device of this embodiment is
A direct type, a pair of light sources 12 that illuminate the liquid crystal display plate 10 from the rear, a reflection plate 21 that reflects the rearward irradiation light from the light sources 12 toward the liquid crystal display plate 10, and the light sources 12 A diffuser plate 22 disposed in front of the diffuser plate 22 for diffusing the direct light from the light source 12 and the reflected light from the reflector plate 21 to the liquid crystal display panel 10, and a light scattering material 17b for equalizing the amount of light to the diffuser plate 22 are provided. The light sources 12 are arranged in a pair, and the light sources 12 are provided at an intermediate position between adjacent light sources 12 of the reflection plate 21.
An intermediate reflector 24 that reflects light from the side to the side of the liquid crystal display panel 10 is formed so as to project forward.

As shown in FIGS. 3 and 4, the reflecting plate 21 is made of a metal plate having a reflectance of 90%, and is bent to have a substantially arcuate cross section corresponding to each light source 12. The reflector 21 is in close contact with the rear end of the light source 12 in order to conduct the heat from the light source 12 to the entire surface of the reflector 21 and to dissipate the heat rearward.

The arcuate joints of the reflection plate 21 are formed in a mountain shape as shown in FIG.
It is supposed to be 4. Here, when the radius of the light source 12 is r and the distance between the centers of the adjacent light sources 12 is P, the intermediate reflector 2
The top portion 24a of 4 is arranged at a distance of P / 2 from the center of the light source 12. The front projection size K2 of the top portion 24a of the intermediate reflector 24 is set according to the equation (4).

K2 ≦ r + (P / 2) tan {sin ⁻¹ (r / P)} (4) This is as shown in FIG.
This is because the light that is going to be radiated directly to the front is reflected in the middle of the light. That is, the distance h from the line segment O1-O2 connecting the tube axis center points of the adjacent light sources 12 to the top portion 24a of the intermediate reflector 24 is estimated by the equation (1) of the first embodiment (5). It becomes like a formula.

H ≦ (P / 2) tan {sin ⁻¹ (r / P)} (5) Further, the front projection size K 2 of the top portion 24 a of the intermediate reflector 24 is set.
Is h + r, as is apparent in FIG. Than this,
Equation (4) can be derived.

The diffuser plate 22 is formed in a rectangular flat plate shape using, for example, milky white translucent acrylic, and is arranged in parallel with the display plate behind the display plate.

The light-scattering material 17b is formed by depositing TiO ₂ , BaSO ₄ on a film 25 such as polyethylene terephthalate.
Etc. is a dot-patterned writing curtain.

In FIG. 4, reference numeral 26 is a holder for the light source 12.

When the light source 12 is caused to emit light in use in the liquid crystal lighting device having the above-described configuration, the light from the light source 12 to the front is directly reflected and the light from the light source 12 to the rear is once reflected by the reflecting plate 21. Thereafter, the light scattering material 17b uniformly distributes the light forward, and the diffuser 22 diffuses the light to illuminate the display plate from the rear.

At this time, since the intermediate reflector 24 is provided at an intermediate position between the light sources 12 adjacent to each other on the reflection plate 21, the light radiated rearward of the light ray L1 grazing the apex 24a, that is, the adjacent light Light that cannot be effectively used as the surface brightness of the diffusion plate 22 can be effectively reflected to the liquid crystal display panel 10 side only by irradiating the matching light sources 12 with each other.

This light is emitted mainly in the oblique front direction of the light source 12, and contributes to the brightness up of the portion of the diffuser plate 22 where the brightness is the lowest. Therefore, the brightness of the diffusion plate 22 can be improved as a whole.

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 each of the above embodiments, the light source 12 has two
Although it is a book, it is not limited to this.

The light scattering materials 17a and 17b are made of TiO.
₂ 、 BaSO ₄ etc. were pattern printed,
For example, a dot pattern may be formed by vapor deposition of aluminum on a film such as polyethylene terephthalate.

[0053]

According to claims 1 and 2 of the present invention, there are the following effects (1) to (4).

(1) Since a notch or an insertion hole as an inclined surface is formed in the light guide plate and a reflector is not used at the end of the light guide plate, the weight of the liquid crystal lighting device can be reduced accordingly.

(2) Since the intermediate position of each light source on the rear surface of the light guide plate is cut out to form an inclined surface, the light from each light source to be directly irradiated to the side light source can be reflected forward. Can effectively illuminate the front. Therefore, the brightness of the liquid crystal display panel can be increased.

(3) Since the insertion hole is formed in the rear surface of the light guide plate and the light source is incorporated in each insertion hole, the light source can be arranged directly below the liquid crystal display plate. Therefore, the entire luminous flux of the light source is more effectively irradiated to the liquid crystal display panel side than in the conventional case, the light utilization efficiency is improved, and a high brightness backlight system can be realized.

(4) Since the light source is inserted so as to project rearward and the highly heat conductive reflection sheet is closely attached to the rear surface of the light source,
The heat from the light source can be dissipated rearward while being conducted to the entire surface of the reflection sheet. Therefore, it is possible to prevent display unevenness of the liquid crystal display panel due to uneven temperature distribution.

According to the third aspect, since the scattering material is formed on the inclined surface of the light guide plate, it is possible to scatter the light from the light source by the scattering material and then reflect the light forward. The uniformity of can be improved.

According to claims 4 and 5, the following (5)-
There is an effect of (6).

(5) Since the highly heat-conductive reflector is in close contact with the light source, the heat from the light source can be dissipated rearward while being conducted to the entire surface of the reflector. Therefore, it is possible to prevent display unevenness of the liquid crystal display panel due to uneven temperature distribution while maintaining the weight reduction peculiar to the direct type without using a separate member.

(6) Since the intermediate reflector is provided at an intermediate position between the adjacent light sources, the light which is emitted from the light sources to the adjacent light sources and cannot be effectively used as the surface brightness of the diffusion plate is displayed on the liquid crystal display plate side. Can be reflected.

According to the sixth aspect, since the scattering material is formed right above the light source, it is possible to scatter the light traveling directly above the light source in other directions. Therefore, it is very effective to prevent uneven lamps on the illumination surface.

[Brief description of drawings]

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

FIG. 2 is an enlarged view showing the optical path of the same.

FIG. 3 is a cross-sectional view of a liquid crystal lighting device showing a second embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG.

FIG. 5 is an enlarged view showing the optical path of the same.

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

FIG. 7 is a cross-sectional view of a conventional light guide type liquid crystal lighting device.

[Explanation of symbols]

 10 liquid crystal display plate 11 light guide plate 12 light source 13 reflection sheet 14 diffusion sheet 15 insertion hole 16 inclined surface 16a inclined top 17a, 17b light scattering material 21 reflector 22 diffuser 24 intermediate reflector 24a top

Claims (6)

[Claims] 1. A light source for illuminating a liquid crystal display plate from the rear, a plurality of light sources, a light guide plate arranged parallel to the liquid crystal display plate so as to guide light from the light sources to the liquid crystal display plate, A liquid crystal lighting device comprising: a reflection sheet for reflecting backward light from a light guide plate to a liquid crystal display plate side; and a diffusion sheet for making the brightness of an illumination surface uniform over the entire surface. On the rear surface, a plurality of insertion holes having a semicircular cross section for inserting the front semicircular portion of each light source are formed in parallel at a distance.
Each light source is inserted into each of the insertion holes so that the rear half of the circular portion thereof projects rearward, and the reflection sheet is closely contacted with the rear surface of each light source projecting rearward, and the reflection sheet has high heat conductivity. , The rear surface of the light guide plate is cut out at an intermediate position from each light source to another light source adjacent to the light source plate so as to be inclined forward so as to reflect side light from each light source to the liquid crystal display panel side. The liquid crystal lighting device, wherein the reflective sheet is closely attached to the inclined surface. 2. The liquid crystal lighting device according to claim 1, wherein the radius of the insertion hole is r, and the distance between the centers of adjacent light sources is P, and the inclined top of the inclined surface of the light guide plate is from the center of each light source. The liquid crystal lighting device is arranged at a distance of P / 2, and the cutout depth dimension K1 of the inclined top is set so that the following expression is established. K1 ≦ (P / 2) tan {sin ⁻¹ (r / P)} 3. The liquid crystal lighting device according to claim 1, wherein a light scattering material that scatters and reflects light from the light source to a diffusion sheet is formed on the inclined surface of the light guide plate. Lighting equipment. 4. A light source for illuminating the liquid crystal display panel from the rear,
A reflector for reflecting the backward irradiation light from the light source to the liquid crystal display plate side, and a diffuser plate disposed in front of the light source for diffusing direct light from the light source and reflected light from the reflector to the liquid crystal display plate. A plurality of the light sources are arranged, the reflectors are in close contact with the respective light sources, the reflectors are made to have high heat conductivity, and the light sources are provided at intermediate positions between the adjacent light sources of the reflectors. An illuminating device for liquid crystals, characterized in that an intermediate reflector for reflecting light from the side to the liquid crystal display panel side is formed so as to project forward. 5. The liquid crystal lighting device according to claim 4, wherein the radius of the light source is r, and the distance between the centers of adjacent light sources is P.
, The top of the intermediate reflector is P from the center of the light source.
The liquid crystal lighting device is arranged at a distance of / 2, and the front projection size K2 of the top of the intermediate reflector is set to satisfy the following equation. K2 ≦ r + (P / 2) tan {sin ⁻¹ (r / P)} 6. The liquid crystal lighting device according to claim 1, wherein a light scattering material for scattering and irradiating light from the light source is formed at a position corresponding to the light source on the front surface of the light guide plate. A lighting device for liquid crystal, which is characterized by: