KR100420193B1 - Surface light source device and image display device with the same device - Google Patents

Abstract

The image display device 27 includes a liquid crystal display panel 16 and a surface light source device 1 for illuminating the same panel. The surface light source device 1 includes a light guide plate 4, a primary light source 7, a reflective sheet 3, a prism sheet 5, and the like. The reflecting sheet 3 has a protrusion beyond the rear side 22 side edge 21 of the incident end face 6. The light absorption layer 28 is formed by dividing into the 1st area | region 28a and the 2nd area | region 28b by the front-end | tip 3a side of a protrusion part. The light absorbing layer 28 is formed of, for example, a dot pattern of an ink dot, and its light absorbing ability gradually increases in the first region 28a and gradually increases in the second region 28b as it is separated from the tip 3a. It is decreasing. While suppressing the light absorption at the part away from the edge 21 low, the luminance nonuniformity by the illumination of an edge etc. is prevented. The light absorbing layer may be constituted only of a region formed so as to increase gradually as the light absorbing ability is separated from the tip 3a.

Description

Surface light source device and image display device provided with the surface light source device {SURFACE LIGHT SOURCE DEVICE AND IMAGE DISPLAY DEVICE WITH THE SAME DEVICE}

The present invention relates to a surface light source device for illuminating an image display panel such as a portable personal computer or a navigation device, and an image display device provided with the surface light source device.

As is well known, a light source device for outputting illumination light extended in a plane shape is called a surface light source device, and is widely used for lighting means of an image display panel. For example, a portable personal computer, a navigation device, or the like is typically provided with an image display device of a type which supplies an output illumination light of a surface light source device to a liquid crystal display panel (image display panel) and displays an image on the liquid crystal display panel. It is.

6, an image display device 40 of this type is illustrated. As shown in the figure, the surface light source device 41 is provided in the image display device 40 as the illumination light supply means.

The surface light source device 41 includes a light guide plate 42, a fluorescent lamp (primary light source; 44) arranged to face the side end surface (incident end surface provided by the minor surface; 43), and a bottom surface of the light guide plate 42. (Rear sheet 45 provided by one major surface; 42a), and prism sheet 46 disposed on the upper surface of the light guide plate 42 (emission surface provided by the other major surface; 42b). ) And a reflector 47 arranged so as to surround the fluorescent lamp 44 from behind.

When the fluorescent lamp 44 is turned on, light is introduced into the light guide plate 42 through the incident end face 43 of the light guide plate 42. This light is repeatedly reflected on the upper surface 42b and the lower surface 42a of the light guide plate 42 and transmitted to the inside of the light guide plate 42. In the process, at the time of internal incidence to the upper surface 42b or the lower surface 42a, a part of the light having an angle of incidence below the critical angle escapes to the outside of the light guide plate 42.

On the other hand, most of the escaped light from the lower surface 42a side of the light guide plate 42 is reflected by the reflective sheet 45 and reincident into the light guide plate 42. The reincident light propagates again in the light guide plate 42, and has an opportunity to become escape light (outgoing light) from the upper surface 42b. If the re-incidence light has an incident angle of less than or equal to the critical angle when the incident light enters the upper surface 42b internally, part of the light is emitted from the upper surface 42b.

In this way, outgoing light (expanded light from the upper surface 42b) that is extended into a plane shape through various path histories is generated. As is already known, the main propagation direction of this outgoing light is considerably inclined forward. The prism sheet 46 corrects this toward the liquid crystal display panel 48 and supplies illumination light from a direction substantially perpendicular to the liquid crystal display panel 48.

It should be noted here that, as shown in Fig. 6, there exists light H that enters into the light guide plate 42 via the edge 50 on the incident end surface side. As shown in FIG. 7, this light H generates a linear bright line 51 on the output surface (upper surface) 46a of the prism sheet 46. The bright line 51 is shown in substantially parallel with the incident end surface 43 in the vicinity of the incident end surface 43. This phenomenon is also called "illumination of the edge."

In addition, since the vicinity of the incident end face 43 is at a close distance from the fluorescent lamp 44, the amount of light emitted from the upper surface of the light guide plate 42 tends to be larger than that of the area far from the fluorescent lamp 44. Therefore, in contrast to the light of the edges, a region of excessive brightness tends to occur in the vicinity of the fluorescent lamp 44. This phenomenon is called " light leakage ", and causes the luminance unevenness to occur along with the edge illumination (brightness line 51).

Needless to say, the luminance unevenness significantly lowers the quality of the illumination output light of the surface light source device 41, and when applied to illumination of the liquid crystal display panel 48, the image of the liquid crystal display panel 48 becomes difficult to see. .

Therefore, the applicant of the present invention previously proposed to solve this problem by the research shown in Fig. 8 (Japanese Patent Laid-Open No. Hei 10-112214). The point of the proposal is that the tip of the reflective sheet 45 disposed along the lower surface of the light guide plate 42 protrudes toward the fluorescent lamp 44 beyond the incident end surface side edge 50. Thereby, the light H which tries to enter inside the light guide plate 42 via the edge 50 is blocked by the reflection sheet 45, and the generation | occurrence | production of a bright line is suppressed. In addition, the light absorption layer 52 is formed in the upper surface 45a of the reflective sheet 45 in the range corresponding to the periphery of the edge 50.

As a result, excessive emission in the vicinity of the incident cross section 43 is suppressed, and light leakage is less likely to occur. However, the problem here is how to actually form the light absorption layer 52. The light absorption layer 52 of the reflection sheet 45 used by the said proposal is as showing in FIG. That is, gray or black ink having a light absorption layer is formed in a dot pattern shape. The dot pattern is designed such that the area occupied by the dot 53 decreases as it becomes farther from the tip (fluorescent lamp side tip 54).

Therefore, a portion of the light absorbing layer 52 having a high light absorbency protrudes from the edge 50 toward the fluorescent lamp 44, so that much light before being incident on the incident end face 43 is absorbed. Therefore, the amount of light introduced into the light guide plate 42 is reduced, resulting in a decrease in the luminance level.

In other words, the prior art of the above proposal has the side effect of reducing the amount of light introduced into the light guide plate 42, although there is an effect of suppressing edge illumination and light leakage.

The present invention has been proposed under the above background. One object of the present invention is to provide a surface light source device which reduces the decrease in luminance level due to the reduction of the amount of light introduced into the light guide plate while exhibiting the effect of suppressing the light of the edge and the light leakage. Another object of the present invention is to provide an image display apparatus which can obtain a display screen that is bright and easy to use by using such an improved surface light source device.

1 is an exploded perspective view of a surface light source device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of principal parts of the surface light source device along the line A-A in FIG. 1.

Fig. 3 is a partial plan view of the reflecting sheet used in the first embodiment, Fig. 3A shows a light absorbing layer forming portion of the reflecting sheet, and Fig. 3B shows an enlarged part of symbol B of Fig. 3A.

4 is a sectional view showing the main parts of a surface light source device according to a second embodiment of the present invention.

FIG. 5A shows a light absorbing layer forming portion of the reflecting sheet, and FIG. 5B shows an enlarged portion of symbol C of FIG. 5A.

6 is a cross-sectional view of a surface light source device showing one conventional example.

FIG. 7 is a view for explaining the problems of the conventional example shown in FIG. 6, FIG. 7A shows a front side cross section, and FIG. 7B is a plan view.

8 is a sectional view of a surface light source device showing another conventional example.

FIG. 9 is a partial plan view of the reflection sheet used in the conventional example shown in FIG. 8, in which FIG. 9A shows a light absorbing layer forming portion, and FIG. 9B shows an enlarged drawing of the portion indicated by symbol (D) in FIG. 9A.

* Description of the symbols for the main parts of the drawings *

1, 41: surface light source device 2: frame

3, 45: reflection sheet 4, 42: light guide plate

5, 46: prism sheet 6, 43: incident cross section

7, 44: fluorescent lamp (primary light source) 16, 48: liquid crystal display panel

18, 28: light absorption layer 20, 30: dot

21, 50: edge 22, 42a: lower surface of the light guide plate (back)

23, 42b: upper surface of the light guide plate (emission surface) 28a: first region of the light absorption layer

28b: second region of the light absorption layer

The present invention provides a light guide plate having an emission surface and a back surface provided by a major surface, a light incident plate having an incident surface provided by a minor surface, a primary light source arranged to supply primary light to the light guide plate through the incident surface, and leakage from the rear surface. It is applicable to a surface light source device having a reflecting member disposed along the rear surface for returning the light into the light guide plate, and an image display device employing the same surface light source device for illumination of the image display panel.

According to a feature of the invention, the reflecting member has a protruding portion protruding toward the primary light source side beyond the edge on the back side of the incident cross section, and the surface on the side opposite to the light guide plate extends over the same edge in the vicinity of the same edge. A light absorbing layer is distributed. The light absorbing layer is formed on the protruding portion so that the light absorbing ability decreases as it approaches the tip of the protruding portion.

This makes it possible to reduce the light absorbed by the light absorbing layer before reaching the incident cross section among the light supplied by the primary light source. On the other hand, in the protruding portion, the light absorbing ability is increased as the edge on the rear side approaches, so that the light absorbing for preventing the edge from being projected can be sufficiently secured.

In addition, it is preferable that the light absorbing layer of the reflecting member has, in addition to the protruding portion, a portion that becomes smaller as the light absorbing ability moves away from the same edge. This is because, in the portion excluding the protrusion (part corresponding to the lower surface of the light guide plate), except for the extremely near edge of the rear side, light falling off therefrom generates light that is involved in the above-described edge projection or light leakage. This is because it becomes difficult to do so, and the necessity of light absorption becomes slim.

Typical examples of the form of the light absorbing layer include a dot pattern of the light absorbing ink or a film of the light absorbing ink (an ink layer expanded in a planar shape without being dispersed in a dot shape). In either case, in the present invention, as described above, the light absorption capacity must be changed around the edge.

This "change in light absorption capacity" can be realized by changing at least one of the area of each dot and the occupancy density of the dot, for example, when the former is employed. In the case where the latter is adopted, for example, it can be realized by changing the light absorption rate of the film. In addition, the light absorption rate of a film can be controlled by adjusting a film thickness, ink concentration, etc.

With respect to the surface light source device according to the present invention, an image display panel according to the present invention is constructed by arranging the image display panels so as to receive the output illumination light of the same surface light source device. The advantages (reduction of luminance unevenness and avoidance of lowering luminance level) of the surface light source device improved according to the present invention are also reflected in the image display apparatus, and the deterioration of image display quality is prevented.

(1st embodiment)

With reference to FIGS. 1-3, the surface light source device which concerns on 1st Embodiment of this invention is demonstrated. In Fig. 1, an exploded perspective view of a surface light source device in which the entirety is indicated by reference numeral (1). 2, the cross section along the line A-A line in FIG. 1 is drawn. FIG. 3 is a view for explaining the light absorbing layer employed in the present embodiment. FIG. 3A shows the formation range of the light absorbing layer, and FIG. 3B shows the formation mode of the light absorbing layer.

First, in Figs. 1 and 2, reference numeral 2 denotes a frame made into a substantially rectangular shape, in which the reflective sheet 3, the light guide plate 4, and the prism sheet 5 are sequentially stacked and accommodated therein. It is.

Fluorescent lamps (primary light sources; 7) are disposed opposite to one side end surface (incident cross section; 6) side of the light guide plate 4, and both ends of the fluorescent lamp 7 have a frame body of the frame 2 ( 8) is fixed in a detachable state.

In addition, the periphery of the fluorescent lamp 7 is covered with the reflector 10 by leaving an opening, and after the light of the fluorescent lamp 7 is reflected directly or by the reflector 10, it enters the incident end surface 6 through the opening. Incident. The reflector 10 is formed of the white PET film which has the outstanding light reflection property. The frame 2 is an injection molded body of white synthetic resin, and includes protrusions 11 and 12 for supporting a substantially rectangular frame 8, a reflective sheet 3, and the like from below, and an upper cutout portion of the frame 8. The plate member 15 fixed to the 13 with the screw 14 is provided.

On the upper surface side of the frame 8 and the plate member 15, panel engaging portions 17a and 17b for engaging the liquid crystal display panel (image display panel 16) are formed. When the liquid crystal display panel (image display panel; 16) is superimposed on the surface light source device (1) using this, a liquid crystal display device (image display apparatus) 27 is configured.

The reflective sheet 3 is formed of a white PET sheet having excellent reflectivity. It should be noted that the reflective sheet 3 has a size that is accommodated in the frame 8 of the frame 2, and one end thereof is larger than the incidence end surface 6 of the light guide plate 4. It is protruding to the side.

And the reflection sheet 3 is equipped with the light absorption layer 18 in the inner side to upper surface (surface on the light guide plate 4 side; 3b) in the vicinity of the incident end surface 6. An example of the light absorption layer 18 is shown in FIG. 3A and FIG. 3B. Referring to the figure, a plurality of dots made of an ink having light absorbency such as gray or black are distributed to form a dot pattern.

As the dot pattern moves away from the tip 3a on the side of the fluorescent lamp of the reflective sheet 3, the area of the dot 20 increases, and as a result, away from the tip 3a, light absorption of the light absorption layer 18 occurs. It is designed to increase capacity (per unit area).

Here, the length of the region where the light absorption layer 18 of the reflective sheet 3 is formed (length along the direction perpendicular to the incident end surface 6; L) is the light guide plate 4, the reflective sheet 3, and the frame. Designing decision is made in consideration of manufacturing error of (2), assembly error of light guide plate 4, reflective sheet 3, frame 2, and the like. However, the light absorption layer 18 is in the range from at least the front end 3a on the side of the fluorescent lamp to the edge where the incident end surface 6 and the lower surface 23 meet (hereinafter also referred to as "lower edge") 21. To be formed. For example, in the present embodiment, the length L for forming the light absorption layer 18 is 2 to 3 mm, and the length L1 of the protrusion extending beyond the lower edge 21 is designed to be about 1 mm. have.

The light guide plate 4 is an injection molded product of synthetic resin such as acrylic resin, for example, and the outlines of the two major surfaces (upper surface 22 and lower surface 23) are substantially rectangular. It is preferable that the cross-sectional shape is substantially wedge shape. The incident end surface 6 is provided by the side cross section of the side with the thick wedge-shaped thickness. In addition, the incident end surface 6 of the light guide plate 4 may be roughened to adjust the amount of emitted light in the vicinity of the incident end surface 6 to serve as a shedding light. Further, a light diffusing ink (for example, an ink made of magnesium carbonate, titanium oxide, or the like) is selectively attached to the upper surface 22 or the lower surface 23 of the light guide plate 4, or the uneven surface (rough surface) May be partially formed, and light may be diffused appropriately to adjust the distribution of the emission intensity.

The prism sheet 5 is formed of a light-transmitting sheet material such as polycarbonate, and a prism surface 24 having a large number of prism rows substantially triangular in cross section is formed on a surface (lower surface) facing the light guide plate 4. It is. The orientation of the prism sheet 5 is determined so that these prism rows extend substantially in parallel with the incident end face 6.

As is well known, the prism sheet 5 arranged in this manner is corrected toward the liquid crystal display panel 16 by correcting the traveling direction of the light emitted by being inclined from the upper surface 22 of the light guide plate 4. There is an action that makes it possible.

The reflector 10 is accommodated in the frame 2 in a state of being bent in an arc shape so as to surround the fluorescent lamp 7 from behind. The upper end 25 of the reflector 10 abuts on the upper surface 22 on the side of the fluorescent lamp 7 of the light guide plate 4, while the lower end 26 is on the side of the fluorescent lamp 7 of the reflective sheet 3. It comes in contact with the lower surface 3c.

Thereby, the light emitted from the fluorescent lamp 7 is guided to the incident end surface 6 of the light guide plate 4 as efficiently as possible. In addition, the lower end part 26 of the reflector 10 is supported by the protrusion part 12 of the frame 2.

The behavior of the light in the surface light source device 1 configured as described above is roughly as follows. When the fluorescent lamp 7 is turned on, light is introduced into the light guide plate 4 from the incident end face 6. This light is repeatedly transmitted from the upper surface 22 and the lower surface 23 of the light guide plate 4 and transmitted to the inside of the light guide plate 4. In the process, at the time of internal incidence to the upper surface 22 or the lower surface 23, a part of the light having an angle of incidence below the critical angle escapes to the outside of the light guide plate 4.

On the other hand, most of the escaped light from the lower surface 23 side of the light guide plate 23 is reflected by the inner side surface of the reflective sheet 3 and reincident into the light guide plate 4. The reincident light propagates again in the light guide plate 4 and has an opportunity to become escape light (outgoing light) from the upper surface 22. If the re-incidence light has an incident angle of less than or equal to the critical angle when the incident light is internally incident on the upper surface 22, a part of the light is emitted from the upper surface 22.

In this way, outgoing light (expanded light from the upper surface 22) that is extended into a planar shape through various path histories is generated. As is well known, the main propagation direction of this emitted light is considerably inclined forward. The prism sheet 5 corrects this toward the liquid crystal display panel (image display panel) 16 and supplies illumination light from a direction substantially perpendicular to the liquid crystal display panel 16.

As described in relation to the prior art, some light is intended to enter the light guide plate 4 via the lower edge 21, as indicated by the reference sign H in FIG. As described above, when this light H is strong, linear bright lines are generated (illuminated) on the output surface (upper surface) of the prism sheet 5.

In addition, as described above, unlike the edge illumination, an area of excessive luminance is likely to occur in the vicinity of the fluorescent lamp 7 (light leakage), and the cause of the non-uniformity of the line with the edge illumination is generated. do.

In this embodiment, such luminance nonuniformity is prevented, and also the side effect (loss of light) resulting from it is suppressed low. In this embodiment, the reflective sheet 3 has a protrusion extending beyond the edge 21, and on the inner side of the protrusion, the light absorption layer 18 gradually absorbs light as the tip 3a approaches. It is because it is formed so that capability may fall.

Light from the fluorescent lamp 7 arriving near the edge 21 is physically shielded by the protruding portion of the reflective sheet 3, and a substantial part of the light from the reflective sheet 3 is located near the edge 21. Absorbed in the light absorbing layer 18. Therefore, the light H that causes the light is weakened, and the tendency of excessive emission (light leakage) from the upper surface 22 around the incident end surface 6 is also reduced.

In addition, it is important here that the light absorption capability of the light absorption layer 18 is not made constant, but since the above-described equalization is performed, the light absorption action of the light absorption layer 18 is sufficiently obtained from the edge 21. It can be greatly reduced in the remote location. In other words, the phenomenon that the light supplied from the fluorescent lamp 7 is absorbed before reaching the incident end surface 6 is greatly alleviated. As a result, the utilization efficiency of light improves.

In particular, the effect is remarkable when the incident end surface 6 of the light guide plate 4 is roughened. That is, when the incident end surface 6 is roughened, a part of the light emitted from the fluorescent lamp 7 is diffusely reflected at the incident end surface 6 depending on the degree of roughening, and a substantial portion of the diffused light is reflected sheet 3. Incident on the protruding portion.

Under such conditions, if the light absorbing layer having a strong light absorbing ability is provided at the portion away from the edge 21 on the light source (fluorescent lamp 7) side, the loss of the amount of light due to this becomes large, and the luminance decreases remarkably. In this embodiment, such a situation is avoided.

It goes without saying that such an advantage of the surface light source device 1 of the present embodiment is reflected in the image display device 27 in which it is formed, that is, the output illumination light with suppressed illumination and light leakage is efficiently supplied. The liquid crystal display panel 16 can perform high quality image display which is easy to see brightly.

(2nd embodiment)

Next, with reference to FIG. 4, FIG. 5, the surface light source device which concerns on 2nd Embodiment of this invention is demonstrated. In FIG. 4, the surface light source device of 2nd Embodiment which indicated the whole by the code | symbol 1 is shown by the same sectional drawing as FIG. 5 is a figure for demonstrating the light absorption layer employ | adopted in this embodiment, FIG. 5A has shown the formation range of a light absorption layer, and FIG. 5B has shown the formation aspect of a light absorption layer.

In addition, the code | symbol used in 1st Embodiment is used in common as much as possible. In addition, this embodiment employ | adopts the structure similar to 2nd Embodiment except the structure related to the light absorption layer formed in a reflection sheet. Therefore, repeated description is abbreviate | omitted about the matter which is common in 1st Embodiment.

As shown in FIG. 4, FIG. 5A, FIG. 5B, in this embodiment, the formation area | region of the light absorption layer 28 of the reflection sheet 3 is ensured wider than the case of 1st Embodiment, and is 1st. It is formed by dividing into the area | region 28a and the 2nd area | region 28b. The first region 28a is a region extending from the vicinity of the tip 3a of the reflective sheet 3 over the edge 21, and the light absorption capability thereof is far from the tip 3a of the reflective sheet 3. It is gradually increasing.

In addition, in the area | region adjacent to the 1st area | region 28a, the 2nd area | region 28b becomes that the length (length along the direction perpendicular | vertical to the incidence cross section 6) is about the same as the 1st area | region 28a. have. And the light absorption capacity of the 2nd area | region 28b is falling as it moves away from the edge 21. As shown in FIG. That is, the equalization of the light absorption capacities of the two regions 28a and 28b is designed in such a manner that the light absorption capacities are maximized at the boundary in opposite directions. In addition, you may make the width of both area | regions 28a and 28b different as needed.

In this embodiment, the position where the light absorption capacity is maximized is located at a small distance (for example, about several mm) inward from the edge 21. The position where the light absorption capacity is maximized may be just below the edge, or in some cases, on the side of the fluorescent lamp 7 rather than just below the edge. The optimal position is preferably determined by design.

Such spreading of the light absorption capability can be realized by forming the ink dot pattern as shown in FIG. 5B instead of the ink dot pattern shown in FIG. 3B.

In the dot pattern in 2nd Embodiment, in the 1st area | region 28a, the area of the dot 30 becomes large as it moves away from the front end 3a, and as it moves away from the front end 3a, the light absorption layer It is formed so that the light absorption capacity (per unit area) of (28) becomes large. Also, in the second region 28b, the area of the dot 30 decreases as it moves away from the edge 21, and as a result, the light absorption capacity of the light absorption layer 28 decreases as it moves away from the edge 21. Per unit area) is formed to be small.

The outline of the behavior of the light in the present embodiment configured as described above is the same as in the case of the first embodiment. Also in this embodiment, as shown by the symbol H in FIG. 4, there exists light which tries to enter the light guide plate 4 via the lower edge 21. When this light H is strong, linear bright lines are generated (illuminated) on the output surface (upper surface) of the prism sheet 5. In addition, as described above, apart from the edge illumination, a region of excess linearity tends to occur in the vicinity of the fluorescent lamp 7 (light leakage), and the cause of luminance nonuniformity is caused along with the edge illumination. do.

Also in this embodiment, such a luminance nonuniformity is prevented by the light absorption layer 28, and also the side effect (loss of light) accordingly is suppressed low. This is because the reflective sheet 3 is also formed so that the light absorbing ability gradually decreases as the reflective sheet 3 approaches the projecting portion exceeding the edge 21.

In addition, in this embodiment, since the light absorption layer 28 is taken widely compared with the light absorption layer 18 of 1st Embodiment, the light H which becomes a cause of light becomes weak more remarkably, and an incident cross section (6) The tendency of excessive emission (light leakage) from the upper surface 22 in the vicinity is also significantly reduced. In addition, such an operation is particularly remarkable when the incident end surface 6 of the light guide plate 4 is roughened, as in the case of the first embodiment.

It goes without saying that such an advantage of the surface light source device of the present embodiment is reflected in the image display device 27 in which it is formed. That is, the liquid crystal display panel 16 to which the output illumination light which suppresses the reflection and the light leakage is efficiently supplied can perform high quality image display which is easy to see brightly.

(Other Embodiments)

The embodiment described above is not intended to limit the present invention. For example, the following modifications are allowed.

(1) In the said embodiment, the light absorption layers 18 and 28 are changing the light absorption rate by changing the area of the dots 20 and 30 of a dot pattern. However, this does not limit the present invention. For example, the light absorption rate may be changed by changing the dot distribution density (number per unit area) of the dot pattern. In addition, the light absorption layers 18 and 28 may change the density | concentration (light absorption rate) of the paint which has light absorption. In this case, the light absorbing layers 18 and 28 may be formed in the form of a film that is widened in a planar shape instead of a dot pattern.

(2) Although the dot shape illustrated the circular thing, it is not limited to this, It can change suitably to elliptical shape, a rectangular shape, etc.

(3) In each of the above embodiments, when the plate member 15 is fixed to the frame 8 with the screws 14, the reflecting sheet 3 is pressed against the edge 21 on the incident end surface side. You may also In this way, the reflective sheet 3 is slightly deformed, so as to cover the edge 21 reliably, and the incident sheet of light H from the edge 21 can be more reliably shielded by the reflective sheet 3.

(4) In each of the above embodiments, the light guide plate 4 having a substantially wedge-shaped cross section is employed, but this is merely an example. For example, the upper surface (emission surface; 22) and the lower surface (back surface; 23) of the light guide plate 4 are formed in parallel. Other suitable shape light guide plate 4 may be used.

(5) A plurality of side cross-sections of the light guide plate 4 may be incident cross-sections, and light introduction may be performed there. In that case, the protrusion part and the absorption layer of a reflection sheet can also be made into multiple numbers with it.

(6) The primary light source is not limited to the fluorescent lamp. For example, a plurality of light emitting diodes arranged in a row may be used as the primary light source.

(7) In each said embodiment, although the aspect which arrange | positions only one prism sheet 5 on the upper surface 22 of the light guide plate 4 was shown, this is only an example, For example, the upper surface (of the light guide plate 4 ( 22) A diffusion sheet, two prism sheets, a protective sheet, or the like, which are combined such that the prism face is substantially orthogonal, may be appropriately arranged.

The surface light source device constructed in accordance with the present invention can reduce the lowering of the luminance level due to the reduction of the amount of light introduced into the light guide plate while exhibiting an effect of suppressing edge projection and light leakage.

In addition, the image display device according to the present invention can obtain a display screen that is bright and easy to use by using the improved surface light source device as described above.

Claims (8)

A light guide plate each having an exit surface and a back surface provided by the major surface, and an incident cross section provided by the minor surface; A primary light source arranged to supply primary light to the light guide plate through the incident cross section; And In the surface light source device having a reflecting member disposed along the rear surface to return the light escaped from the rear surface into the light guide plate: The reflecting member has a protrusion projecting toward the primary light source side beyond an edge of the back side of the incident end face, In addition, the reflective member includes a light absorption layer for absorbing light in the vicinity of the edge on a surface of the side opposite to the light guide plate, The light absorbing layer is distributed over the edges, and is formed on the protruding portion such that the light absorbing ability decreases as the tip is closer to the tip of the protruding portion. The surface light source device according to claim 1, wherein the light absorption layer has a portion outside the protruding portion in which the light absorption capacity decreases as it moves away from the edge. The light absorbing layer of claim 1 or 2, wherein the light absorbing layer is formed of a dot pattern of a light absorbing ink, The said dot pattern is formed so that light absorption capacity may change by changing at least one of the area of each dot and the occupancy density of a dot, The surface light source device characterized by the above-mentioned. The method of claim 1 or 2, wherein the light absorption layer is made of a film of light absorbing ink, The film is a surface light source device, characterized in that the light absorption capacity is changed by changing the light absorption rate of the film. An image display apparatus comprising a surface light source device and an image display panel disposed to overlap the surface light source device, and to display an image by receiving the output illumination light of the surface light source device. The surface light source device includes: a light guide plate each having an exit surface and a back surface provided by a major surface, and an incident cross section provided by a minor surface; A primary light source arranged to supply primary light to the light guide plate through the incident cross section; And A reflecting member disposed along the back surface to return the light escaped from the back surface into the light guide plate; The reflecting member has a protrusion projecting toward the primary light source side beyond an edge of the back side of the incident end face, In addition, the reflective member includes a light absorption layer for absorbing light in the vicinity of the edge on a surface of the side opposite to the light guide plate, And the light absorbing layer is distributed over the edges, and is formed such that the light absorbing ability decreases as it approaches the tip of the projecting portion. 6. The image display apparatus according to claim 5, wherein the light absorbing layer has a portion outside the protruding portion, the light absorbing ability of which decreases as it moves away from the edge. The method of claim 5 or 6, wherein the light absorption layer is made of a dot pattern of light absorbing ink, The dot pattern is formed such that the light absorption capacity is changed by changing at least one of the area of each dot and the occupancy density of the dot. 7. The light absorbing layer according to claim 5 or 6, wherein the light absorbing layer is formed of a film of light absorbing ink, And the film is formed such that the light absorption capacity changes by changing the light absorption rate of the film.