JPH08271885A - Surface light source device and display device using the same - Google Patents

Abstract

PURPOSE: To provide a surface light source excellent in productivity and uniform. CONSTITUTION: This surface light source device is provided with a tubular light source 961 and a light transmission plate 911 propagating light source light from the tubular light source 961 ; and the light transmission plate 911 includes plural projections 913 integrated with the light transmission plate 911 and arranged on one main surface side of the plate 911 so that the light source light propagated in the plate 911 may be selectively projected from one main surface side of the plate 911, and an optical path changing means integrated with the plate 911 and arranged on the other main surface side faced to one main surface of the plate 911 so that the light source light propagated in the plate 911 may be selectively projected from one main surface side of the plate 911.

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, so that the surface light source device of the backlight system to the edge light system is used. It's coming.

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, there is a light loss due to the scattering pattern, and it is necessary to separately print the scattering pattern, so that the productivity is reduced. Improvement was desired.

[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. Moreover, the light utilization efficiency can be improved.

However, in the above-mentioned edge light type surface light source device, there is a restriction on the molding of the protrusion,
The protrusions cannot be arranged in a sufficiently narrow pitch.
For this reason, in-plane variation occurs in the surface light source light from the surface light source device, and thus uniform display quality cannot be ensured.

The present invention has been made in view of the above technical problems, and provides a surface light source device having high light utilization efficiency and excellent productivity, and a display device using the same. Has an aim.

[0011]

According to a first aspect of the present invention, in a surface light source device including a tubular light source and a light guide plate for propagating light source light from the tubular light source, the light guide plate includes the light guide plate. A plurality of protrusions integrated with the light guide plate arranged on the one main surface side of the light guide plate so as to selectively emit the light source light propagating in the light plate from the one main surface side of the light guide plate; Integrated with the light guide plate arranged on the other main surface side opposite to the one main surface of the light guide plate so that the light source light propagating in the light plate is selectively emitted from the one main surface side of the light guide plate. And an optical path changing means.

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

According to a third aspect of the invention, there is provided the optical path changing means according to the first aspect, wherein a plurality of first optical paths are formed on the other main surface and reflect the light source light to the one main surface side of the light guide plate. The feature is that it has two reflecting surfaces.

The invention described in claim 4 is characterized in that the first reflecting surface according to claim 3 is disposed between the second reflecting surfaces in a plane. The invention according to claim 5 includes a surface light source device including a display panel including an effective display region including a plurality of display pixels, a tubular light source, and a light guide plate that propagates light source light from the tubular light source. In the display device, the light guide plate is arranged on the one main surface side of the light guide plate so that the light source light propagating in the light guide plate is selectively emitted from one main surface side of the light guide plate. A plurality of protrusions integrated with the light plate, and another main surface facing the one main surface of the light guide plate so that the light source light propagating in the light guide plate is selectively emitted from the one main surface side of the light guide plate. It is characterized by including an optical path changing means integrated with the light guide plate arranged on the front surface side.

[0015]

According to the present invention, the light source light propagating in the light guide plate is not limited to the plurality of protrusions formed on the one main surface side of the light guide plate but also the other main surface facing the one main surface of the light guide plate. Light is emitted from one main surface side of the light guide plate by the optical path changing means disposed on the side.

Therefore, even if the pitch of the protrusions arranged on the one main surface side of the light guide plate is restricted, the optical path changing means allows
It is possible to compensate for the in-plane variation of the light source light, thereby ensuring uniform surface light source light and further excellent display quality. Furthermore, each of the protrusion and the optical path changing means arranged on the one main surface side of the light guide plate is formed integrally with the light guide plate, so that excellent productivity can be secured.

[0017]

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), 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), Y drive circuit board (831) connected to two Y-TAB (821), (823), Surface light source device (901) arranged on the back side of liquid crystal panel (101) Including and

Each of the X-TAB (801), ..., (804) is
The surface light source device (901) is bent to the back side of the surface light source device (901) so as to reduce the external dimensions of the liquid crystal display device (1).
Is connected to the X drive circuit board (811) arranged on the back side of the.

The liquid crystal panel (101) has a display area (103) having 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 Yj 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 a molded body made of acrylic resin and has a substantially rectangular light guide plate (911) which is slightly larger than the effective display area (103) of the liquid crystal panel (101). ), A tubular light source (951) that is arranged in close proximity with one end surface of the light guide plate (911) as a light introduction surface (921), and a reflective film (guide film that efficiently guides the light source light from the tubular light source (951) to the light guide plate (911). 9
61) includes a prism sheet (991) disposed between the light guide plate (911) and the liquid crystal panel (101).

The main surface of the light guide plate (911) has a light introduction surface (92
1) Selective light from the light source introduced from the light guide plate (911)
A plurality of first protrusion rows (913) having a triangular cross section are arranged substantially parallel to the light introducing surface (921) so as to suppress the spread of the light source light emitted from the light source. In addition, on the other main surface of the light guide plate (911), the second projection row (915) having a triangular cross-section is formed so that the light source light introduced from the light introduction surface (921) is selectively emitted from one main surface side. ) Are arranged in a plurality of rows substantially parallel to the light introduction surface (921). In addition, the first protrusion row (913) and the second protrusion row (91
5) are staggered in plan and also tubular light sources (951)
They are arranged so that the arrangement pitch becomes denser as they get farther from.

As shown in FIG. 4, each of the first protrusion rows (913) has a reflecting surface (913a) and a light guide plate (9) on the light introducing surface (921) side.
An emission surface (913b) is included on the end side of 11). Also, the second protrusion row
Each of the (915) has a reflective surface (9
Including 15a).

The light source light incident from the light introducing plane (921) of the tubular light source (951) is approximately 42 with respect to the vertical line of the light introducing surface (921) because the light guide plate (911) is made of acrylic resin. The light is incident on the light guide plate (911) with a converging angle of Ω (Ω1).

From the above, the angle (θ1) formed by the reflecting surface (913a) of the first projection row (913) with respect to the perpendicular of the light introducing surface (921) is set to 40 °, and the projection row (913) The angle (θ2) formed by the emission surfaces (913b) and (915b) of is set to about 90 °. Here, the angle (θ1) is set to 40 °, but the angle (θ1) is not limited to this,
Light from the light source incident from the light introduction surface (921) is almost
Anything can be used as long as it is set so as to be guided to the emission surface (913b) of 3). However, if the angle (θ1) is too small, it becomes impossible to arrange a large number of the projection rows (913), which may lead to uneven brightness. Therefore, it is preferable to set the angle within the range of 20 to 40 °.

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)
Light from the light emitting surface (913b) is emitted toward the one end of the light guide plate (911) at a spread angle (Ω2) of about 90 °.

Further, the light source light incident from the light introducing surface (921) of the light guiding plate (911) has a condensing angle (Ω1) of about 42 ° with respect to the perpendicular of the light introducing surface (921). Since the light is incident on the inside of 911), the angle (θ3) formed by the reflecting surface (915a) of the second projection row (915) with respect to the perpendicular of the light introducing surface (921) is set to 20 °. Here, the angle (θ3) is set to 20 °, but the angle (θ3) is not limited to this, and the light source light incident from the light introducing surface (921) is guided to one main surface side. Anything can be set as long as it is set. However, if the angle (θ3) is too small, it becomes impossible to arrange a large number of the projection rows (915), which may cause uneven brightness. Therefore, it is desirable to set the angle within the range of 10 to 25 °.

The other surface (915b) of the second projection row (915)
Need only be formed so that the light from the light source propagating in the light guide plate (911) is not reflected.
Although 4) is set to about 90 °, it may be set so as not to exceed 132 °.

With this structure, the second projection row (915)
Light source light reflected by the reflective surface (915a) of the light guide plate (911)
The light will be emitted from one of the main surfaces. LCD panel (10
Prism sheet placed between 1) and light guide plate (911)
(991) protrudes toward the light guide plate (911) side and
11) Multiple projection rows arranged almost parallel to the projection row (913)
Including (993). These protrusion rows (993) include a refraction surface (993a) that guides the light emitted from the light guide plate (991) to the liquid crystal panel (101) side, and is formed by the main surface and the refraction surface (993a) of the prism sheet (991). The formed angle (θ5) is set to about 40 °.

As a result, the light source light emitted toward the light guide plate (911) or toward the edge is controlled to be the light source light toward the liquid crystal panel (101) side. With the above configuration, the liquid crystal display device (1) operates as follows.

The light source light incident from the tubular light source (951) to the light introduction surface (921) of the light guide plate (911) propagates inside the light guide plate (911), and a part of it propagates through the first protrusion row (913). The light is emitted from the emission surface (913b). Similarly, a part of the light source light propagating in the light guide plate (911) is reflected by the reflection surface (913a) of the second protrusion row (915), and is emitted from the one main surface side of the light guide plate (911). To be done.

The outgoing light emitted from the light guide plate (911) in this way is guided by the prism sheet (991) to the liquid crystal panel (10).
It is controlled to a uniform surface light source that is focused toward 1). As described above, according to the liquid crystal display device of this embodiment, the light source light emitted from the light guide plate toward the liquid crystal panel has the first protrusion integrally formed with the light guide plate on one main surface of the light guide plate. Not only the rows, but also the second projection row formed integrally with the light guide plate on the other main surface of the light guide plate is converted into the surface light source light toward the liquid crystal panel side, so there is a restriction on the forming pitch of each projection. However, a uniform surface light source light can be obtained, and thus a good display image without uneven brightness can be obtained.

In this embodiment, a row of protrusions is provided on the other main surface side of the liquid crystal panel to guide the light from the light source to one main surface side. However, the cross section is triangular and the reflecting surface is provided on the tubular light source side. Needless to say, it may be a groove. Further, a reflection film may be provided on the other main surface side of the light guide plate, or a metal material may be attached to improve the reflectivity.

In this embodiment, the light guide plate made of acrylic resin is used, but other materials may be used. In this case, since the solid angle of the light source light incident from the light introducing surface is slightly different, the angle formed by each protrusion or groove may be appropriately changed in consideration of the above circumstances.

Further, in this embodiment, one end face of the light guide plate is used as the light introduction face and the tubular light source is arranged close to this one end face. However, the tubular light source has a groove or the like formed in the light guide plate corresponding to the display area. You may arrange it. By doing so, the external dimensions of the surface light source device with respect to the display area can be configured to be sufficiently small,
Therefore, a narrow frame of the display device is achieved.

[0040]

According to the surface light source device of the present invention, the light utilization efficiency is high and the in-plane variation of the display brightness can be sufficiently reduced without impairing the productivity. Also,
According to the display device using this surface light source device, it is possible to obtain a good display image without display unevenness.

[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 partial schematic cross-sectional view of the liquid crystal display device taken along the line AA ′ in FIG.

FIG. 3 is a schematic front view of an array substrate of the liquid crystal display device of FIG.

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

[Explanation of symbols]

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

Claims (5)

[Claims] 1. A surface light source device comprising a tubular light source and a light guide plate for propagating the light source light from the tubular light source, wherein the light guide plate is configured to transmit the light source light propagating in the light guide plate to the light guide plate. A plurality of protrusions integrated with the light guide plate arranged on the one main surface side of the light guide plate so as to be selectively emitted from the one main surface side, and the light source light propagating in the light guide plate of the light guide plate. A surface including an optical path changing unit integrated with the light guide plate, which is disposed on the other main surface side of the light guide plate facing the one main surface so as to selectively emit from the one main surface side. Light source device. 2. The projection according to claim 1, wherein the projection has a first emission surface that emits the light source light from the tubular light source that propagates in the light guide plate to the outside of the light guide plate, and the protrusion that propagates in the light guide plate. A surface light source device having a triangular cross section including a first reflection surface that guides the light source light from a tubular light source to the first emission surface or reflects into the light guide plate. 3. The optical path changing means according to claim 1, which is a plurality of second reflecting surfaces formed on the other main surface and reflecting the light source light to the one main surface side of the light guide plate. Surface light source device. 4. The surface light source device according to claim 3, wherein the first reflecting surface is arranged between the second reflecting surfaces in a plane. 5. A display device comprising: a display panel including an effective display region including a plurality of display pixels; and a surface light source device including a tubular light source and a light guide plate for propagating light source light from the tubular light source. A plurality of light guide plates are integrated with the light guide plate arranged on the one main surface side of the light guide plate so that the light source light propagating in the light guide plate is selectively emitted from the one main surface side of the light guide plate. And the other main surface of the light guide plate facing the one main surface of the light guide plate so that the light source light propagating in the light guide plate is selectively emitted from the one main surface side of the light guide plate. A display device comprising: an optical path changing unit integrated with the light guide plate.