KR20030033996A - Surface light source unit and image display device - Google Patents

Abstract

PURPOSE: To provide a technology in which reduction of an outgoing light luminance can be prevented and the outgoing light luminance can be homoge nized effectively when an LED is arranged at the rear face side of a light guide plate and the light of the LED is made to be a surface-formed illuminating light via the light guide plate. CONSTITUTION: Among the light from the LED 4, the light directly outgoing from an outgoing face 5 without being reflected at an inclined face 12 of the light guide plate 2 is reflected at a light reflecting part 10b of a light shielding member 10 to be returned back to the inside of the light guide plate 2, and effectively utilized later as the illuminating light. Further, a highly luminous light component to apt to become an anomalous light emission is absorbed at a light absorbing part 10a of the light shielding member 10. As a result, as for an image display device 1, homogenization of the luminance of outgoing light can be aimed at without inviting the reduction of the luminance.

Description

Surface light source device and image display device {SURFACE LIGHT SOURCE UNIT AND IMAGE DISPLAY DEVICE}

The present invention relates to an image display apparatus having a surface light source device and an illumination member illuminated in a plane shape by the surface light source device. The present invention is applied to, for example, image display apparatuses in portable telephones, portable electronic terminal apparatuses, electronic organizers, car navigation apparatuses, video cameras, digital cameras, VTR apparatuses, and surface light source apparatuses used in these image display apparatuses. Examples of the illuminated member illuminated by the surface light source device in a plane shape include a liquid crystal display panel and other image display panels.

For example, in portable telephones, video cameras, and the like, liquid crystal display devices are widely used as image display devices. In most cases, the liquid crystal display device includes a liquid crystal display panel as a member to be illuminated, which is illuminated in a planar shape by the surface light source device from the rear side.

7 and 8 show an example of such an image display apparatus. As shown in these figures, the image display device 30 includes a light guide plate 31 and an LED (light emitting diode) 33 as a primary light source. The light guide plate 31 has an exit surface (surface; 35) and an equal back surface (back surface) 32, and an inclined surface 34 is formed at one end portion.

The LED 33 is disposed at a position suitable for supplying light to this inclined surface 34. When the LED 33 is turned on, the light reaches the inclined surface 34 through the rear surface 32 and is internally reflected there, and propagates the inside of the light guide plate 31 away from the inclined surface 34. In this internal propagation process, light enters the exit surface 35 many times.

As is widely known, a part of the light which does not satisfy the total reflection condition at the time of this internal incidence is emitted from the emission surface 35 toward the liquid crystal display panel 36, and the remaining light is internally reflected.

Most of the internally reflected light passes through the internal reflection by the rear surface 32 or the like and is again internally incident on the exit surface 35, thereby giving an opportunity for exit. By such a process, the illumination light beam extended in planar form from the emission surface 35 as a whole is output.

The problem here is that the LED 33 supplies light with directivity toward the narrow inclined surface 34, so that a contrast variation occurs on the exit surface 35. In particular, since the LED having directivity as a point light source is generally used, the contrast on the emission surface 35 tends to be more remarkable than when using a rod-shaped fluorescent lamp. In order to avoid this problem, for example, in Japanese Unexamined Patent Application Publication No. 2000-299011, a prism surface is formed on a portion of the light guide plate rear side opposite to the light source (LED chip), and then the light from the light source is dispersed in various directions. It is proposed to introduce into the light guide plate. According to this proposal, the directivity of the light from the light source is relaxed, and the luminance uniformity of the exit surface is once improved (first prior art).

For example, like the image display apparatus 45 shown in FIG. 9, there also exists a method of arrange | positioning the light shielding tape 40 in the emission surface 38 side of the light guide plate 37. As shown in FIG. As for the surface of the light-shielding tape 40 at the light guide plate 37 side, as shown in FIG. 10, a dark color paint is applied to the nearest site | part 42 of the light-emitting body 41, and the other site | region 43 For light paints are painted. According to this method, much light from the light emitting body 41 is absorbed in the dark part of the closest part 42 of the light emitting body 41, and the display body 44 is uniformly illuminated (2nd prior art; See Japanese Laid-Open Patent Publication No. 2000-310703).

However, in the first conventional technique, as shown in FIG. 8, a substantial portion of the light from the LED 33 incident on the inside of the light guide plate 31 from the rear surface 32 side is not reflected on the inclined surface 34. Reaching the direct exit surface 35 cannot be avoided. Most of this light 46 is emitted from the exit surface 35 as it is. Therefore, the emitted light luminance is locally increased at the side where the LED 33 is disposed (left end side of the drawing), and eventually uniformity of sufficient emitted light luminance is difficult to achieve.

In addition, in the first conventional technology, since the prism face is formed on the light guide plate 31, a fine processing must be performed on the exit molding die of the light guide plate 31, resulting in an increase in the cost required for the mold.

On the other hand, in the second conventional technology, since the light-shielding tape 40 is made to be uniform in the emitted light luminance, the same problem as in the first conventional technology does not occur. However, since the light-shielding tape 40 employed in the second prior art is to form a light pattern 43, 42, 43, 42, 43 on the entire surface of the surface facing the light guide plate 37, Even if the uniformity of the luminance is sufficient, a substantial portion of the light emitted from the emission surface is lost due to light absorption due to the light and shade pattern, and thus cannot contribute to illumination. That is, the utilization efficiency of light becomes low.

Accordingly, it is an object of the present invention to solve the above-described drawbacks of the prior art with respect to a surface light source device of the type which spreads light into a light guide plate by using internal reflection by an inclined surface formed at the side end, and has a simple configuration. It is an improvement that the fall of utilization efficiency is small and uniform luminance can be obtained.

Another object of the present invention is to provide an image display apparatus which can efficiently display with uniform brightness by using such an improved surface light source device.

1 is an exploded perspective view showing an image display device according to a first embodiment of the present invention.

2 is a plan view showing an image display device according to a first embodiment of the present invention.

FIG. 3 is a sectional view along the line A-A for the image display device shown in FIG. 2; FIG.

4 is a plan view showing a light blocking member.

FIG. 5 is a cross-sectional view showing a cross section of an image display device according to a second embodiment of the present invention in the same depiction manner as in FIG. 3; FIG.

6 is a cross-sectional view showing an image display device according to a third embodiment of the present invention.

7 is a plan view of a conventional image display apparatus.

Fig. 8 is a sectional view showing a section along B-B for the image display device shown in Fig. 7;

9 is an exploded perspective view for explaining an image display device according to a third conventional art.

Fig. 10 is a plan view showing a light shielding member used in the image display apparatus according to the third prior art.

* Description of the main symbols in the drawing

1, 30: image display device

2, 31, 37: light guide plate

3, 32: back (back side)

4, 33: LED (light source)

5, 35, 38: exit surface

6, 36 liquid crystal display panel (lighting member)

8, 20: cotton

10: light blocking member

10a: light absorption unit

10b: light reflecting part

11: surface light source device

12: slope

13, 19: edge

17: light diffusion sheet (light control member)

18a, 18b: Prism sheet (light control member)

The present invention firstly comprises a light guide plate having an exit surface, an inclined back surface formed on the exit surface, and an inclined surface formed at a side end portion, and a primary light source for supplying light from the back side toward the inclined surface. The light supplied by is applied to the surface light source device which is adapted to be diverted away from the inclined surface by the internal reflection by the inclined surface.

According to the present invention, a light shielding member is disposed along the exit surface at a predetermined dimension width from near the edge of the inclined surface. The light shielding member has a band-shaped light absorbing portion extending substantially parallel to the inclined surface at an edge of the side farther from the inclined surface, and further reflects light toward the exit surface side in a portion except the light absorbing portion. The light reflection part is formed. As the primary light source, for example, one using a light emitting diode may be employed.

Next, the present invention includes a light guide plate having an exit surface, an inclined back surface formed on the exit surface, and an inclined surface formed at the side end portion, and a primary light source for supplying light from the back side toward the inclined surface, wherein the primary light source Is applied to an image display device including a surface light source device adapted to be redirected away from the inclined surface by an internal reflection by the inclined surface, and an illumination member disposed to face the exit surface. .

According to the present invention, a light shielding member is disposed along the exit surface at a predetermined dimension width from near the edge of the inclined surface. The light shielding member has a band-shaped light absorbing portion extending substantially parallel to the inclined surface at an edge of the side farther from the inclined surface, and further reflects light toward the exit surface side in a portion except the light absorbing portion. The light reflection part is formed. As the primary light source, for example, one using a light emitting diode may be employed.

Embodiment

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

[First embodiment]

1 to 3 show, respectively, an exploded perspective view (FIG. 1), a plan view (FIG. 2), and a cross sectional view along the line AA in FIG. 2 (FIG. 3) of the configuration of the image display device according to the first embodiment of the present invention. will be.

Referring to these drawings, the image display apparatus 1 includes a light guide plate 2, an LED (light emitting diode; 4), a liquid crystal display panel (lighting member; 6), and a reflective sheet 7. A plurality of LEDs (light emitting diodes) 4 are used to constitute a primary light source.

The light guide plate 2 is a major surface, which has an exit surface 5 and a back surface 3 and is cut obliquely from one rear end (left side end in FIG. 3) to the exit surface 5 at one side end (left side end in FIG. 3). It has an inclined surface 12. The LED (Light Emitting Diode) 4 is disposed at a position suitable for supplying light by shaping the inclined surface 12 from the back surface 3 side of the light guide plate 2. In this example, it is arrange | positioned just below the inclined surface 12 in FIG.

On the other hand, the liquid crystal display panel (lighting member) 6 is disposed along the exit surface 5 of the light guide plate 2, and the reflective sheet 7 is disposed along the back surface 3 of the light guide plate 2. And the light shielding member 10 is adhere | attached on the inner surface (surface of the exit surface 5 side) 8 of the liquid crystal display panel 6 by fixing means, such as an adhesive agent or a double-sided tape.

The image display device 1 can also be regarded as being composed of a liquid crystal display panel 6 and a surface light source device 11 that illuminates it. Here, the surface light source device 11 includes at least the light guide plate 2, the LED 4, and the reflective sheet 7. It goes without saying that the light blocking member 10 also constitutes a part of the surface light source device 11 depending on the viewing direction.

The light guide plate 2 is comprised from materials excellent in light transmittance, such as PMMA (methyl polymethacrylate), PC (polycarbonate), and cycloolefin resin. In addition, the thickness of the light guide plate 2 is shape | molded so that it may become thinner as it moves away from the inclined surface 12, and the cross-sectional shape becomes substantially wedge shape. The planar shape is approximately rectangular.

The inclined surface 12 internally reflects light from the LED 4 and redirects it away from the inclined surface 12. The inclination angle of the inclined surface 12 is determined so that the advancing direction of most components of the light after this redirection is substantially parallel to the exit surface 5 (rightward in Fig. 3).

Further, on the back surface 3 of the light guide plate 2, a light scattering pattern (not shown) for scattering light propagating inside the light guide plate 2 and promoting the emission from the exit surface 5 is formed by screen printing or the like. It is. The light scattering pattern is composed of, for example, a plurality of fine wrinkled surface regions (uneven surface regions), and light incident inside the scattered fine regions is scattered. As is well known, this scattering diversifies the direction of propagation of the internal propagation light, so that emission from the emission surface 5 is likely to occur.

In general, it is preferable that such emission promotion works relatively strongly at a portion far from the inclined surface 12 in order to achieve uniformity in luminance. Therefore, in general, the light scattering pattern is formed such that the density (coating rate) increases as the distance from the inclined surface 12 increases.

The reflective sheet 7 is formed of a film excellent in light reflectivity such as white PET (polyethylene terephthalate). Most of the light emitted from the back 3 side of the light guide plate 2 is reflected by the reflection sheet 7 and returns to the inside of the light guide plate 2.

Next, the light shielding member 10 provided in the exit surface 5 side of the light guide plate 2 is demonstrated. This light shielding member 10 has a function of preventing the light from the LED 4 from leaking directly from the exit surface 5 near the edge 13 of the inclined surface 12. The light shielding member 10 extends substantially parallel to the inclined surface 12, and has a band shape having a predetermined width (width along the direction orthogonal to the edge 13; L). Moreover, the length (length along the edge 13) of the light shielding member 10 substantially coincides with the width W of the light guide plate 2. As described above, the light blocking member 10 is adhered to the inner side surface of the liquid crystal display panel 6 (surface facing the exit surface 5; 8) by fixing means such as adhesive or double-sided tape. • It is fixed.

Importantly, as shown in FIG. 4, the light blocking member 10 is divided into a light absorbing portion 10a on the side far from the inclined surface 12 and a light reflecting portion 10b on the side close to the inclined surface 12. It is lost. That is, a light absorbing material (for example, black ink) is applied in a band shape along the edge of one side of the film such as white PET having excellent light reflectivity (edge far from the inclined surface 12; 19) at a predetermined width L2, and this black color is applied. The ink coating portion is used as the light absorption portion 10a, while the remaining portion of the width L1 (white surface is exposed) is used as the light reflection portion 10b. In addition, L = L1 + L2.

The actual values of the above-described dimensions L, L1, and L2 are determined at design time so that the light absorption by the light absorbing portion 10a is as small as possible, and the intensity (luminance) of the emitted light can be achieved. In general, the optimum values of these dimensions L, L1, and L2 vary depending on various design conditions such as the plate thickness T of the light guide plate 2 and the number of installation of the LEDs 4.

In addition, a material having excellent light reflectivity may be adhered or applied to a part of the light absorbing film to form the light reflecting portion 10b, and the remaining portion may be the light absorbing portion 10a. In addition, the light reflection part 10b may have scattering reflectivity. In general, this light scattering property is assumed to work advantageously to equalize the emitted light brightness.

The image display device 1 configured as described above is housed in the housing recess 15 of the case 14. Thereby, each side wall of the case 14 opposes the inclined surface 12 or each side surface 16a, 16b, 16c of the light guide plate 2. These side walls function to reflect the light emitted from the inclined surface 12 or each side surface 16a, 16b, 16c, and to return to the inside of the light guide plate 2. As shown in FIG.

In addition, the area (effective utilization area) which actually outputs illumination light among the exit surfaces 5 of the light guide plate 2 is the part which is not covered with the light shielding member 10, and is shown with the oblique part in FIG. 1 and FIG. . The emitted light from this effective area is used for illuminating the liquid crystal display panel 6.

The outline of the behavior of the light in the image display apparatus 1 is summarized as follows. When the LED 4 is turned on, light first passes through the vicinity of one end of the back surface 3 and is introduced into the light guide plate 2, but most of it directly reaches the inclined surface 12 and is internally reflected. By this internal reflection, the traveling direction of the light is switched to become internal propagated light having a traveling direction parallel to or close to the exit surface 5. The internal propagation light is propagated far from the inclined surface 12 as a whole and closer to the side surface 16a on the opposite side.

In this internal propagation process, emission gradually occurs from the effective utilization area of the emission surface 5. As described above, the light scattering pattern formed on the back surface 3 promotes this emission. The light emitted from the effective area of the exit surface 5 is supplied to the liquid crystal display panel 6, and contributes to display by a well-known principle.

It should be noted, however, that some of the light from the LED 4 is internally incident on the exit surface 5 near the inclined surface 12 and part of the light is emitted from the exit surface 5. . As described above, when this light is supplied to the liquid crystal display panel 6 as it is, local contrast is produced on the display.

In this embodiment, most of such output light is reflected by the light reflection part 10b of the light shielding member 10 and returned to the inside of the light guide plate 2, and is then effectively used as illumination light through various paths in the light guide plate. do.

However, a part of the light reflected by the light reflection part 10b is internally reflected by the back surface 3, and returns directly to the emission surface 5. When the returned light is emitted from the exit surface 5, abnormal light emission is observed. This return light has a high probability of coming from a part slightly away from the edge 13, but in this embodiment, since the light absorption part 10a is formed there, abnormal light emission can be avoided. Moreover, although light loss generate | occur | produces by the light absorption part 10a, since the light absorption part 10a is formed only in a part of the light shielding member 10, light loss can be suppressed small.

In addition, in this embodiment, since the light shielding member 10 was adhere | attached on the inner side surface 8 of the liquid crystal display panel 6, the fixing means, such as an adhesive agent or a double-sided tape, does not act directly on the light emitted from the light guide plate 2. This does not cause a decrease in luminance due to light absorption. In addition, if the adhesive or the double-sided tape is located between the light blocking member 10 and the light guide plate 2, it is easy to generate light leakage from the portion of the adhesive or the double-sided tape, but in the present embodiment, such light leakage may occur. There is no concern.

Second Embodiment

FIG. 5 is a cross-sectional view of an image display device according to a second embodiment of the present invention, which corresponds to FIG. 3 in the first embodiment. In addition, the same code | symbol is attached | subjected to the same component as 1st Embodiment, and the overlapping description is abbreviate | omitted suitably, and this Embodiment is described.

As shown in FIG. 5, in the image display apparatus 1 according to the present embodiment, the light diffusion sheet 17 and the prism sheet are disposed between the emission surface 5 of the light guide plate 2 and the liquid crystal display panel 6. Light control members such as 18a and 18b are disposed. Among these light control members, the light shielding member 10 is adhered and fixed to the inner surface (surface facing the light guide plate 2) 20 of the light control member (light diffusion sheet 17) at the innermost side (near the light guide plate).

In the first embodiment, the behavior of light in the image display device 1 configured as described above is different from that added by the light control member such as the light diffusion sheet 17 and the prism sheets 18a and 18b. Is the same as the behavior of light. Here, these light control members correct | orient directivity by light-diffusion and a prism action with respect to the light whose emission luminance was uniform by the same light shielding member 20 employ | adopted in 1st Embodiment. Therefore, it does not need to explain in particular that it can also show the same effect as 1st Embodiment also in 2nd Embodiment.

In addition, in this embodiment, the light guide plate 2, the LED 4, the reflective sheet 7, the light control member (light diffusion sheet 17, prism sheets 18a, 18b), and the light shielding member 20, It can be seen that the surface light source device 11 illuminating the liquid crystal display panel 6 is configured.

[Third Embodiment]

FIG. 6 is a cross-sectional view of an image display device according to a third embodiment of the present invention, which corresponds to FIG. 3 in the first embodiment. In addition, the same code | symbol is attached | subjected to the same component as 1st Embodiment, and the overlapping description is abbreviate | omitted suitably, and this Embodiment is described.

In this embodiment, as shown in FIG. 6, the light reflection part 10b of the light shielding member 10 is extended to the lower edge 21 of the inclined surface 12 of the light guide plate 2, and the light reflection part 10b ), The inclined surface 12 of the light guide plate 2 is covered. In this way, leakage of light from the minute gap generated between the case 14 and the light guide plate 2 and the minute gap generated between the case 14 and the liquid crystal display panel 6 can be prevented.

In addition, although the extension part of the light reflection part 10b of the light shielding member 10 is inserted in the clearance gap between the inclined surface 12 of the light guide plate 2, and the case 14, it is provided in the light guide plate 2 and the case 14. It should not be glued. Also in this embodiment of such a configuration, it is not necessary to describe in particular that the same effects as in the above-described first or second embodiment can be obtained.

The three embodiments have been described above, but these are merely examples, and the following modifications are allowed, for example.

(a) In the above-described embodiment, the light guide plate 2 is one whose cross-sectional shape is substantially wedge shaped. However, it is not limited to this, You may employ | adopt that a cross-sectional shape is substantially rectangular (the light guide plate of the whole thickness is the same).

(b) In the above embodiment, black ink is employed as the light absorbing material, but this is only an example. The light absorbing material may be generally one capable of absorbing light, and may be colored ink such as dark gray or green.

(c) The surface of the light reflection part 10b should just be a color excellent in light reflection property generally, and is not limited to white. For example, a silver surface may be formed by silver deposition or the like.

As described above, according to the present invention, the light emitted from the emission surface directly without reflecting from the inclined surface of the light guide plate among the light from the primary light source such as an LED is reflected by the light reflection portion of the light shielding member and returned to the inside of the light guide plate, It can be used effectively later as illumination light. In addition, the light absorbing portion of the light blocking member can absorb high luminance light components that tend to be abnormally emitted.

Therefore, it is possible to provide the surface light source device which aims at equalizing the emitted light brightness while suppressing the decrease in the brightness. In addition, by using such an improved surface light source device, it becomes possible to provide an image display device capable of high quality image display without difference in contrast.

Claims (4)

A light guide plate having an exit surface, an inclined back surface formed on the exit surface, an inclined surface formed at a side end portion, and a primary light source for supplying light from the back side toward the inclined surface, In the surface light source device, the light supplied by the primary light source is redirected away from the inclined surface by the internal reflection by the inclined surface, A light blocking member is arranged along the exit surface at a predetermined dimension width from near the edge of the inclined surface, The light shielding member has a band-shaped light absorbing portion that extends substantially parallel to the inclined surface at an edge on a side far from the inclined surface, A surface light source device, characterized in that a light reflecting portion for reflecting light toward the exit surface side is formed at portions except the light absorbing portion. The method of claim 1, The primary light source is a surface light source device using a light emitting diode. A light guide plate having an exit surface, an inclined back surface formed on the exit surface, an inclined surface formed at a side end portion, and a primary light source for supplying light from the back side toward the inclined surface, A surface light source device in which the light supplied by the primary light source is diverted away from the inclined surface by internal reflection by the inclined surface; An image display apparatus comprising an illumination member disposed to face the exit surface, Between the illumination member and the exit surface, a light shielding member is arranged at a predetermined dimension width from near the edge of the inclined surface, The light shielding member has a band-shaped light absorbing portion that extends substantially parallel to the inclined surface at an edge on a side far from the inclined surface, And a light reflecting portion for reflecting light toward the exit surface side is formed in a portion except for the light absorbing portion. The method of claim 3, wherein And the light source is a primary light source.