JPH08271886A - Surface light source device and display device using the same - Google Patents

Abstract

PURPOSE: To provide a compact surface light source device whose outside dimension is not restricted by a tubular light source by housing the tubular light source in the thickness direction of a light transmission plate. CONSTITUTION: This light source device is provided with a lamp housing groove 921 formed nearly in parallel with the long side of the light transmission plate 911 in the center part of its back surface, and the tubular light source 951 is housed in the groove 921. The device is shaped to be tapered so that plate thickness may be reduced toward the end of the plate 911 from the groove 921. Then, light source light made incident on the 1st light introducing plane 921a of the plate 911 is propagated in the plate 911 and a part of the light is emitted from the emitting surface of a 1st projection train 913. In the same manner, the light source light made incident on the 2nd light introducing plane 921b of the plate 911 is also propagated in the plate 911 and a part of the light is emitted from the emitting surface of a 2nd projection train 915. The emitted light emitted from the plate 911 is controlled to be diffused light whose angle 13 about 90 deg., and controlled to be the light source light whose condensing angle is 22 deg. and which faces to a liquid crystal panel 101 by a prism sheet 991.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device and a display device using the same.

[0002]

2. Description of the Related Art A display device represented by a liquid crystal display device is
Utilizing the features of thinness, light weight, and low power consumption, it has come to be used as various display devices for televisions, computers, car navigation systems, and the like.

For example, a light transmission type liquid crystal display device includes a liquid crystal panel in which a liquid crystal layer is held between a pair of electrode substrates,
The liquid crystal panel includes a surface light source device that is disposed on one main surface and guides light source light to the liquid crystal panel.

In such a display device, in order to further reduce the thickness and size of the device, it is necessary to reduce the thickness of the surface light source device, and the surface light source device of the backlight system to the edge light system is used. Has become.

An edge light type surface light source device is, as disclosed in Japanese Utility Model Laid-Open No. 63-24529, a tubular light source and a thin plate shape such as an acrylic resin having a milky white scattering pattern printed on the back side. A light guide plate is included, and one end surface of the light guide plate is disposed in proximity to the tubular light source. Then, the light source light from the tubular light source propagates through the light guide plate, is scattered by the scattering pattern on the back surface of the light guide plate, and is emitted to the main surface of the light guide plate.

According to the above edge light type surface light source device, although the device can be made thin, the light loss due to the scattering pattern and the light emitted from the light guide plate is approximately 180 with respect to the main surface of the light guide plate. Since it has an emission angle (Ω) of °, a large amount of light from the light source does not contribute to the display, resulting in poor light utilization efficiency. Therefore, in order to secure a sufficient display brightness, it is unavoidable to increase the power consumption of the surface light source device.

[0007]

As a solution to the above problems, there are known edge light type surface light source devices disclosed in, for example, JP-A-5-313163 and JP-A-6-75123. ing.

This is because a plurality of protrusions are arranged on the main surface side of the light guide plate facing the display panel, and the light emitted from the light guide plate is controlled by these protrusions, and the conventional scattering pattern can be eliminated. The light utilization efficiency can be improved.

In view of the above technical background, recent display devices are required to be further miniaturized, and in particular, there is an increasing demand for reducing the outer dimensions of the device with respect to the display area, that is, narrowing the frame. .

However, in the above-mentioned edge light type surface light source device, the tubular light source has to be disposed outside the display area because the tubular light source is disposed so as to face the light incident surface of the light guide plate. . Therefore, the frame size is restricted in the region where the tubular light source is arranged.

The present invention has been made in response to the above technical problems, and provides a surface light source device which has a high light utilization efficiency and can achieve a narrow frame, and a display device using the same. The purpose is to do.

[0012]

The invention according to claim 1 is provided with a tubular light source and a light guide plate including a plurality of protrusions on one main surface for selectively emitting the light source light from the tubular light source. In the surface light source device, the light guide plate accommodates the tubular light source in the thickness direction of the light guide plate, and the light formed in the thickness direction to guide the light source light from the tubular light source to the light guide plate. It is characterized in that it is provided with a storage portion including an introduction plane.

According to a second aspect of the present invention, the projection according to the first aspect includes an emission surface for emitting the light source light from the tubular light source propagating in the light guide plate to the outside of the light guide plate, and the light guide surface. It is characterized in that the light source light from the tubular light source propagating in the light plate has a triangular cross section including a reflection surface that guides the light source light to the emission surface or reflects the light in the light guide plate.

According to a third aspect of the present invention, a display panel including a display area including a plurality of display pixels, a tubular light source for irradiating the display panel with surface light source light, and a light source light from the tubular light source are selectively formed. In a display device including a surface light source device having a light guide plate having a plurality of protrusions emitted to a main surface thereof, the light guide plate stores the tubular light source in a thickness direction of the light guide plate, and It is characterized by comprising a storage portion including a light introducing plane formed in the thickness direction so as to guide the light source light from the tubular light source to the light guide plate. The invention described in claim 4 is characterized in that the tubular light source according to claim 3 is arranged corresponding to the inside of the display region of the display panel.

[0015]

According to the present invention, since the tubular light source is housed in the thickness direction of the light guide plate, the outer dimensions of the surface light source device are not restricted by the tubular light source. Therefore, it is possible to provide a small surface light source device and a display device having a small frame size.

Further, according to the present invention, since the light source light incident from the light introducing plane of the light guide plate is controlled by the protrusions arranged on the main surface of the light guide plate, the light loss due to the scattering pattern as in the conventional case is also caused. Therefore, the light utilization efficiency can be improved.

Further, through the projection, a reflecting surface for reflecting the light source light from the tubular light source propagating in the light guide plate into the light guide plate and the light source light from the tubular light source propagating in the light guide plate are emitted to the outside of the light guide plate. By having a triangular cross-section including the exit surface to
The spread of the light emitted from the light guide plate can be sufficiently suppressed, and thus the light utilization efficiency can be further improved.

[0018]

EXAMPLE A liquid crystal display device according to an example of the present invention will be described below.
(1) will be described with reference to the drawings. As shown in FIGS. 1 and 2, a liquid crystal display device (1) of this embodiment is a light transmission type liquid crystal panel (1) that operates in a normally white mode.
01), four X's arranged on one side of the liquid crystal panel (101)
-TAB (801), (802), (803), (804), four X-TAB (806) arranged on one end side facing each other, liquid crystal panel (101)
Two Y-TABs (821), (82) placed at the other end of the
2) X connected to four X-TABs (801), ..., (804)
Drive circuit board (811), X drive circuit board (813) connected to the other four X-TAB (806), Two Y-TAB (82
1) and (823), a Y drive circuit board (831), and a surface light source device (901) arranged on the back side of the liquid crystal panel (101).

Each of the X-TABs (801), ..., (804), (806) reduces the external dimensions of the liquid crystal display device (1).
Bend to the back side of the surface light source device (901)
X drive circuit boards (811), (80
6) is connected to.

The liquid crystal panel (101) has a display area (103) with a diagonal of 14 inches, and as shown in FIG. 4, the array substrate (200) and the counter substrate (300) are made of a sealing material (not shown). No)
5 micron gap is maintained through the gap, and the gap is subjected to rubbing treatment in a direction orthogonal to each other to give orientation, and a positive film is provided through the alignment films (291) and (391). A liquid crystal layer (401) mainly composed of a nematic liquid crystal material having a dielectric anisotropy is held.

As shown in FIGS. 3 to 4, the array substrate (200) has a plurality of scanning lines Yj (j = 1, 2, ..., N) and a plurality of scanning lines on one main surface side of the glass substrate (201). Signal line Xi (i = 1,2, ...,
m) are arranged in a matrix and ITO (Indium-Tin-Oxi) is formed in a region surrounded by the scanning lines Yj and the signal lines Xi.
A transparent pixel electrode (251) composed of de) is arranged.
A thin film transistor (hereinafter abbreviated as TFT) (231) is arranged near each intersection of the scanning line Yj and the signal line Xi. This TFT (231) uses the scanning line Yj itself as a gate electrode (211), an insulating film (213) arranged on the gate electrode (211), and an island-shaped amorphous silicon arranged via the insulating film. (A-Si: H) thin film (215), a-Si: H thin film
(215) Channel protective film (217), aS placed on top
A drain electrode (221) extending from the signal line Xi and electrically connected to the i: H thin film (215), a pixel electrode (251) and a-
A source electrode (2) for electrically connecting to the Si: H thin film (215)
23) and Further, between the drain electrode (221) and the source electrode (223) and the a-Si: H thin film (217),
In order to obtain a good ohmic junction, n ⁺ type a-Si: H thin films (222) and (224) containing phosphorus as impurities are arranged as low resistance semiconductor films.

Further, an auxiliary capacitance line Cj made of the same material as the scanning line Yj and wired substantially parallel to the scanning line Yj is arranged on the glass substrate (201), and has a pixel electrode (251) and an auxiliary capacitance line Cj. The auxiliary capacitance (Cs) is formed by.

The counter substrate (300) is mounted on the glass substrate (301) facing the array substrate (200) and the TF of the array substrate (200).
T (231), between the light-shielding film (311) and the light-shielding film (311) arranged so as to shield the gap between the signal line Xi and the pixel electrode (251) and the gap between the scanning line Yj and the pixel electrode (251). A color filter layer (321) composed of red (R), green (G), and blue (B) color portions, and a counter electrode (331) composed of ITO disposed on the color filter layer (321). Including.

Then, the array substrate (200) and the counter substrate (3
Polarizing plates (411) and (421) are attached to the outer surface of (00), respectively, and thus the liquid crystal panel (101) having a plurality of display pixels is constructed.

Next, the surface light source device (901) will be described. As shown in FIG. 2, the surface light source device (901) is made of acrylic resin and has an effective display area (1) of the liquid crystal panel (101).
A light guide plate (911) of a substantially rectangular shape slightly larger than 03), a tubular light source arranged in the lamp storage groove (921) of the light guide plate (911).
(951) and the reflective film (96
1) includes a prism sheet (991) disposed between the light guide plate (911) and the liquid crystal panel (101).

The light guide plate (911) is formed in a region corresponding to the effective display region (103) of the liquid crystal panel (101), more specifically, in the central portion of the back surface, substantially parallel to the long side of the light guide plate (911). A lamp storage groove (921) is provided, and the tubular light source (951) is stored in the lamp storage groove (921). And the lamp storage groove (921)
The taper shape is formed so that the plate thickness becomes thinner toward the end of the light guide plate (911).

As shown in FIG. 5A, the light guide plate 911 has a region corresponding to the lamp housing groove 921 as a third region and first and second regions sandwiching the third region. Functionally classified.

The lamp receiving groove (921) is provided in the light guide plate (911).
The first light introducing plane (921) formed in the thickness direction of the light guide plate (911) so as to guide the light source light from the tubular light source (951) to the first region of the
a), the light guide plate to guide the light source light to the second area of the light guide plate (911)
A second light introducing plane (921b) formed in the thickness direction of (911),
The light guide plate (91) is configured to guide the light source light to the third area of the light guide plate (911).
The third light introducing plane (921) formed substantially parallel to the main surface of (1)
c) Including and.

In the first area on the main surface of the light guide plate (911),
The first projection row (913) having a triangular cross-section is arranged first to selectively spread the light source light introduced from the first light introducing plane (921a) and suppress the spread of the light source light emitted from the light guide plate (911). A plurality of rows are arranged substantially parallel to the one light introduction plane (921a). Further, the light source light introduced from the second light introducing plane (921b) is selectively applied to the second region on the main surface of the light guide plate (911), and the spread of the light source light emitted from the light guide plate is suppressed. As described above, a plurality of second protrusion rows (915) having a triangular cross section are arranged substantially parallel to the second light introducing plane (921b). These first and second projection rows (9
The gaps of 13) and (915) become denser as they are farther from the tubular light source (951), thereby ensuring the uniformity of display brightness.

As shown in FIG. 4, each of the first protrusion rows (913) has a reflecting surface (913a) on the first light introducing plane (921a) side and an emitting surface (913) on the edge side of the light guide plate (911). 913b) is included. Also, the second
Each of the protrusion rows (915) also includes a reflecting surface (915a) on the second light introducing plane (921b) side and an emitting surface (915b) on the end side of the light guide plate (911). That is, in the light guide plate (911), the first region and the second region are symmetrical with respect to the third region.

From the tubular light source (951) to the first light introducing plane side (921
Since the light guide plate (911) is made of acrylic resin, a light source light incident via the side a) and the side of the second light introduction plane (921b) is perpendicular to the vertical line of the first light introduction plane (921a). About 42
The light is incident at a condensing angle of Ω (Ω1) and a condensing angle of about 42 ° (Ω1) with respect to the perpendicular of the second light introducing plane (921b).

From the above, the first light introducing plane (921
a) and the vertical line of the second light introducing plane (921b) with respect to each projection row (9
The angle between the reflecting surfaces (913a) and (915a) of (13) and (915) (θ
1) is set to 40 °, and the angle (θ2) formed between the projection lines (913) and (915) and the emission surfaces (913b) and (915b) is set to about 90 °. Here, the angle (θ1) is set to 40 °, but the angle (θ1) is not limited to this, and the light source light incident from the first and second light introduction planes (921a) and (921b) is used. Is approximately the output surface (913) of each projection row (913), (915).
Anything can be set as long as it is set to lead to b) and (915b). However, if the angle (θ1) is too small, each projection row (9
Since it is not possible to arrange a large number of 13) and (915), which may lead to uneven brightness, it is desirable to set within the range of 20 to 40 °. In particular, in this embodiment, since the plate thickness of the light guide plate (911) is tapered so that it becomes thinner from the tubular light source (951) toward the end of the light guide plate (911), each projection row (913), The angle (θ1) formed by the reflecting surfaces (913a) and (915a) of the (915) can be set to a large value, for example, exceeding 42 °, whereby a large number of protrusion rows (913) and (915)
Can be arrayed, which makes it possible to further suppress uneven brightness.

Although the angle (θ2) is set to about 90 ° here, it is preferably 80 ° or more in order to reduce the spread of the emitted light, and may be an obtuse angle exceeding 90 °.

With this structure, the first protrusion row (913)
From the light emitting surface (913b) of the light guide plate (911), the light source light condensed at a divergence angle (Ω2) of about 90 ° is emitted toward one end side, and the light emitting surface of the second protrusion row (915). From (915b), the light source light condensed at a spread angle (Ω2) of about 90 ° is emitted toward the other end of the light guide plate (911).

The prism sheet (991) disposed between the liquid crystal panel (101) and the light guide plate (911) protrudes toward the light guide plate (911) side, and the projection row (913) of the light guide plate (911). , (915) and a plurality of projection rows (993), (995) arranged substantially parallel to each other.
These protrusion rows (993) and (995) include refraction surfaces (993a) and (995a) that guide the light emitted from the light guide plate (991) to the liquid crystal panel (101) side, and are the main surface of the prism sheet (991). And refracting surface (993a),
The angle (θ3) formed with (995a) is set to about 35 °.

As a result, the light source light emitted toward the edge of the light guide plate (911) is controlled to the light source light having the converging angle (Ω3) 22 ° toward the liquid crystal panel (101) side. Also, the light guide plate
The light source light incident from the third light incident plane (921c) of (911) is emitted from the light guide plate (911) through the light diffusion sheet (981). Light diffusion sheet (981) on the third area of the light guide plate (911)
Is provided to prevent the light source brightness in the third region from becoming extremely higher than that in the first and second regions, and the light diffusion sheet (981) is provided in the third light introducing plane (921c). And the tubular light source (951), and the main surface of the light guide plate (911) in the third region or the third light introducing plane (921c) may be roughened in a satin shape.

With the above structure, this liquid crystal display device (1)
Works as follows: From the tubular light source (951) to the light guide plate (9
The light source light incident on the third light introducing plane (921c) of (11) enters the light guide plate (911) from the third light introducing plane (921c), passes through the light diffusing sheet (981), and further the prism sheet. It is incident on the liquid crystal panel (101) via (991).

The light source light incident on the first light introducing plane (921a) of the light guide plate (911) propagates inside the light guide plate (911), and a part of the light source surface (913) of the first protrusion row (913). It is emitted from 913b). Similarly, the light source light incident on the second light introducing plane (921b) of the light guide plate (911) also propagates inside the light guide plate (911), and a part of the light source
The light is emitted from the emission surface (915b) of the row of protrusions (915).

In this way, the emitted light emitted from the light guide plate (911) is controlled to be a diffused light of about 90 °. And
The light emitted from the light guide plate (911) is the prism sheet.
(991) causes the light collection angle toward the liquid crystal panel (101) (Ω
3) The light source is controlled to 22 °.

As described above, according to the liquid crystal display device (1) of this embodiment, the tubular light source (951) has the effective display area.
Since the light guide plate (911) corresponding to (103) is housed in the thickness direction, the external dimensions of the liquid crystal display device (1) are not restricted by the tubular light source (951), and thus the device can be downsized. Can be achieved. Moreover, the light guide plate (911) is tapered, and the X drive circuit boards (811), (8
Since 06) is arranged, the frame of the liquid crystal display device (1) can be further narrowed.

The tubular light source (951) is a liquid crystal display device.
(1) can be easily attached / detached from the back or side, so maintenance is easy. For example, if the tubular light source (951) and the reflection film (961) are unitized and can be attached to and detached from the light guide plate (911), the light source can be easily replaced.

Further, since the light source light from the surface light source device (901) is controlled to have a small converging angle, the light utilization efficiency is high, and the power consumption of the device can be reduced.

According to this embodiment, for example, as compared with the conventional surface light source device in which the scattering pattern is arranged on the back surface of the light guide plate,
The display brightness in the liquid crystal display device could be sufficiently improved.

In the above-described embodiment, the case where the tubular light source (951) is arranged in the central portion of the light guide plate (911) has been described as an example, but the present invention is not limited to this, and for example, FIG. As shown in b), it may be arranged near the edge of the light guide plate (911).

Further, in the above-mentioned embodiment, the light guide plate (911)
The case where the lamp housing groove (921) is arranged in the central portion of the above has been described as an example, but this may be one that penetrates the light guide plate (911).

[0046]

According to the surface light source device of the present invention, the light utilization efficiency is high, and according to the display device using the surface light source device, the frame of the device can be narrowed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the display device taken along the line AA ′ in FIG.

FIG. 3 is a partial schematic front view of an array substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a partial schematic cross-sectional perspective view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining the function of the surface light source device according to the embodiment of the present invention.

[Explanation of symbols]

 (1) ... Liquid crystal display device (100) ... Array substrate (300) ... Counter substrate (901) ... Surface light source device (913), (915) ... Projection row (913a), (915a) ... Reflective surface (913b), (915b)… Exit surface (951)… Tubular light source

Claims (4)

[Claims] 1. A surface light source device comprising: a tubular light source; and a light guide plate having a plurality of protrusions for selectively emitting the light source light from the tubular light source on one main surface thereof, wherein the light guide plate comprises the tubular light source. The light guide plate is provided in a thickness direction, and the light guide plate is provided with a storage portion including a light introducing plane formed in the thickness direction so as to guide the light source light from the tubular light source to the light guide plate. Surface light source device. 2. The projection according to claim 1, wherein the projection has an emission surface for emitting the light source light from the tubular light source propagating in the light guide plate to the outside of the light guide plate, and the tubular light source propagating in the light guide plate. A surface light source device having a triangular shape in cross section including a reflection surface that guides the light source light from the light source to the emission surface or reflects into the light guide plate. 3. A display panel including an effective display area composed of a plurality of display pixels, a tubular light source for irradiating the display panel with surface light source light, and a plurality of protrusions for selectively emitting light source light from the tubular light source. In a display device including a surface light source device including a light guide plate included in one main surface, the light guide plate stores the tubular light source in a thickness direction of the light guide plate, and the light source light from the tubular light source. A display device comprising: a storage part including a light introducing plane formed in the thickness direction so as to guide the light to the light guide plate. 4. The display device according to claim 3, wherein the tubular light source is arranged corresponding to the effective display area of the display panel.