JP2006134634A - Light guide plate, planar light source device, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display panel capable of preventing generation of moire fringes, capable of surface illumination with uniform brightness of emission light. <P>SOLUTION: A light, emitted from an LED 6 is incident on an incident face 5 of the light guide plate 4, and transmitted through the inside of the light guide plate 4. The light to be emitted from the emitting face 10 of the light guide plate 4 is deflected in a direction the normal line of the emitting face 10 of the light guide plate 4 by a light control member 11 arranged so as to face the emitting face 10 of the light guide plate 4, and the liquid crystal display panel 3 is illuminated by the deflected light. Many protrusions 15, extending in a direction almost perpendicular to the incident face 5 of the light guide plate 4, are formed on the back face 7 side of the light guide plate 4 along the incident face 5 in parallel with each other, and many protrusions 20, extending in a direction diagonal to the incident face 5 of the light guide plate 4, are formed on the light control member 11 in parallel with each other. Further, the thickness of the light guide plate 4 is gradually reduced as heading in the direction of being separated farther from the incident face 5, and also reduced, as heading from one side face 18 to the other side face 19. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light guide plate of a surface light source device that illuminates a member to be illuminated (for example, a liquid crystal display panel) such as a mobile phone, a portable terminal device, an electronic dictionary, a portable game machine, various electronic devices, and a personal computer from the back side, The present invention relates to a surface light source device as a backlight using an optical plate, and a display device that illuminates a member to be illuminated with the surface light source device.

  Conventionally, as shown in FIG. 21, a surface light source device 102 that illuminates a liquid crystal display panel (illuminated member) 103 such as a personal computer in a planar shape from the back side includes an emission surface 110 of a light guide plate 104, a liquid crystal display panel 103, and the like. The light control member 111 is disposed between them, and the light emitted from the light guide plate 104 is transmitted through the light control member 111, so that the light traveling direction is changed by the light control member 111 to the normal direction of the emission surface 110 of the light guide plate 104. The liquid crystal display panel 103 can be efficiently illuminated by being deflected toward the (Z direction), and the brightness of the display surface of the liquid crystal display panel 103 is increased.

  That is, such a surface light source device 102 is a prism-shaped protrusion 115 having a substantially triangular cross section formed on the back surface 107 side of the light guide plate 104 and extending in a direction orthogonal to the incident surface 105 (Y direction). 115 is a direction normal to the exit surface 110 of the light guide plate 104 in the imaginary plane parallel to the entrance surface 105 of the light guide plate 104 and perpendicular to the exit surface 110 of the light guide plate 104. It is designed to be deflected to the side. Next, a prism-shaped protrusion 120 having a substantially triangular cross section formed on the back surface side of the light control member 111 and extending in a direction substantially parallel to the incident surface 105 (X direction) of the light guide plate 104 is guided. In a virtual plane orthogonal to the incident surface 105 of the light plate 104 and orthogonal to the output surface 110 of the light guide plate 104, light emitted from the output surface 110 of the light guide plate 104 is deflected and transmitted in the normal direction of the light guide plate 104. It is like that. As a result, the liquid crystal display panel 103 is efficiently illuminated by the light emitted from the surface light source device 102.

  However, when such a surface light source device 102 is used to illuminate the liquid crystal display panel 103 from the back side, the brightness of the display surface of the liquid crystal display panel 103 can be increased as described above. It has been known that a striped pattern such as a moire pattern is generated on the display surface of the liquid crystal display panel, causing a problem that the display image on the liquid crystal display panel 103 is difficult to see.

  Therefore, as shown in FIG. 22, the applicant of the present application is configured to incline the prism-shaped protrusion 120 of the light control member 111 with respect to the incident surface 105 of the light guide plate 104 (for example, incline by an inclination angle θ). A surface light source device 102 that can prevent the occurrence of a stripe pattern such as moire stripes on the display surface of the liquid crystal display panel 103 has already been devised (Patent Document 1).

  In addition, the surface light source device 202 illustrated in FIG. 23 has a plurality of protrusions 212 or grooves 224 extending in the thickness direction of the incident surface 205 of the light guide plate 204, and light from the LED 206 is guided through the protrusions 212 or grooves 224. The angle at which the light from the LED 206 enters the light guide plate 204 (the angle at which the light spreads) becomes larger than the light spread angle when the incident surface 205 is a mirror surface. The dark portion (area shown by oblique lines) of the substantially triangular shape generated on the exit surface 210 in the vicinity of the entrance surface 205 is reduced, and the luminance of the illumination light emitted from the exit surface 210 of the light guide plate 204 is made uniform. (Patent Document 2).

Japanese Utility Model Publication No. 5-25426 JP 2002-196151 A

  However, for example, in the surface light source device as shown in FIG. 21 and FIG. 22, the prism-shaped protrusion 115 is formed on the back surface 107 side of the light guide plate 104, and the light guide plate 104 has a high directional emission property. It is difficult for light to be emitted from the vicinity of the surface 105, and the luminance differs greatly between the outgoing light from the vicinity of the incident surface 105 of the light guide plate 104 and the outgoing light from the vicinity of the surface opposite to the incident surface 105 of the light guide plate. It has a problem of causing variation.

  Further, when the projection 212 or the groove 224 of the incident surface 205 of the light guide plate 204 as shown in FIG. 23 is applied to the light guide plate 104 of the surface light source device 102 as shown in FIG. Even though the planar shape (the shape viewed from the normal direction of the exit surface 210 of the light guide plate 204) is formed in a symmetrical shape with respect to the normal direction of the incident surface 205, the prism shape of the light control member 111 Since the projection 120 is inclined with respect to the incident surface 105 of the light guide plate 104, as shown in FIG. 23, the right end L1 and the left end L2 of the light incident in a substantially fan shape have brightness. It was different and it was difficult to make the emitted light luminance uniform.

  Therefore, an object of the present invention is to make it possible to make the luminance of illumination light for illuminating a liquid crystal display panel as an illuminated member even more uniform.

  The invention of claim 1 relates to a light guide plate, wherein light from a light source incident from a side surface is provided with a directivity by a directivity output means in a process of propagating through the inside, and has a desired directivity from the output surface. It comes out. In the light guide plate of the present invention, the side surface has a rectangular shape in which the dimension in the width direction perpendicular to the thickness direction is larger than the dimension in the thickness direction. The light guide plate of the present invention gradually reduces the plate thickness as it goes away from the side surface, and gradually reduces the plate thickness as it goes away from one side surface orthogonal to one end side in the width direction of the side surface. It is like that.

  The invention of claim 2 relates to a surface light source device, comprising: a light guide plate according to the invention of claim 1; and a light control member disposed so as to oppose the emission surface of the light guide plate. It is a feature.

  According to a third aspect of the invention, the light control member of the surface light source device according to the second aspect of the invention is characterized. That is, the light control member is formed with a large number of prism-like projections having a substantially triangular cross section extending in an oblique direction with respect to the side surface of the light guide plate.

  According to a fourth aspect of the invention, the light control member of the surface light source device according to the third aspect of the invention is characterized. That is, the prismatic protrusion is formed so as to extend obliquely from the side surface toward the one side surface.

  A fifth aspect of the invention comprises the surface light source device according to any one of the second to fourth aspects of the present invention, and a member to be illuminated that is illuminated by light emitted from the surface light source device. The present invention relates to a display device.

  A sixth aspect of the present invention relates to the display device according to the fifth aspect, wherein the illuminated member is a liquid crystal display panel.

  According to the present invention, it is possible to promote the emission of light in the vicinity of the incident surface, and to reduce the difference in brightness of the emitted light between the portion where light is difficult to be emitted near the incident surface and other portions. Variation can be reduced, and uniform surface illumination can be achieved.

  In addition, according to the present invention, it is possible to prevent the occurrence of moire fringes when the liquid crystal display panel as the illuminated member is illuminated by light transmitted through the light control member arranged to face the light exit surface of the light guide plate. At the same time, since the image display surface can be illuminated over a wide range with uniform illumination brightness, the display image is easy to see.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings.

[Configuration of surface light source device and display device including the same]
1 to 4 show a display device 1 according to the present embodiment. The display device 1 is configured to illuminate a liquid crystal display panel (illuminated member) 3 in a planar shape by a surface light source device 2.

(Surface light source device)
The surface light source device 2 includes a light guide plate 4, a plurality of LEDs (light emitting diodes) 6 as light sources arranged to face the side surface (incident surface) 5 of the light guide plate 4, and the back surface 7 side of the light guide plate 4. The light reflection member 8 is disposed, and the light control member 11 is disposed so as to face the emission surface 10 of the light guide plate 4.

  The surface light source device 2 allows light from the LED 6 to enter the inside of the light guide plate 4 from the incident surface 5 of the light guide plate 4, and then out of the light propagating inside the light guide plate 4. The light whose incident angle with respect to is less than the critical angle is emitted from the emission surface 10 of the light guide plate 4, and the emitted light is deflected by the light control member 11 toward the normal direction of the emission surface 10 of the light guide plate 4. It has become.

(Light guide plate)
The light guide plate 4 is formed using a material having excellent light transmittance such as polymethyl methacrylate (PMMA), polycarbonate (PC), and cycloolefin resin material. As shown in FIGS. 1 to 5, the light guide plate 4 is a plate-like body having a substantially rectangular planar shape, and one end 12 in the width direction (longitudinal direction indicated by X) of the incident surface 5 on which the LED 6 is disposed. The plate thickness on the side is formed to be the thickest, and the plate thickness is gradually decreased (for example, the plate thickness is gradually decreased at the inclination angle α) as it moves away from the incident surface 5 (toward the Y direction), and at the same time, The plate thickness is gradually reduced from the side surface (abbreviated as one side surface) 18 side to the other side surface (the other side surface opposite to the one side surface 18) orthogonal to the incident surface 5 (for example, the plate thickness at an inclination angle β). Is gradually reduced). That is, in the light guide plate 4, the maximum inclination direction R of the back surface 7 is closer to the diagonal direction from the one end 12 side, which is the thickest part of the incident surface 5, and the maximum inclination angle ε with respect to the horizontal plane 17 of the back surface 7. Is generated in the maximum inclination direction R, the plate thickness near the diagonal end portion 14 extending from the one end 12 side of the incident surface 5 is the thinnest.

  Then, on the back surface 7 of the light guide plate 4, prism-like protrusions (directed emission providing means) 15 extending in a direction substantially orthogonal to the incident surface 5 are parallel along the longitudinal direction (X direction) of the incident surface 5. In addition, many are formed continuously. The prism-shaped protrusion 15 has a substantially triangular cross section, and is formed over the entire area from the incident surface 5 of the back surface 7 of the light guide plate 4 to the opposite end surface 16 thereof. The prism-shaped protrusion 15 deflects the light from the LED 6 toward the normal direction of the exit surface 10 of the light guide plate 4 in a virtual plane parallel to the entrance surface 5 of the light guide plate 4 and orthogonal to the exit surface 10. It is like that.

  Here, as long as the directional emission property imparting unit imparts directional emission property to the light propagating through the inside so that the light emitted from the emission surface 10 is emitted with a desired directivity, as described above, The protrusion 15 formed on the back surface 7 of the light guide plate 4 is not limited to the prism-like protrusion 15 extending in a direction substantially orthogonal to the incident surface 5, and is a protrusion formed on the output surface 10 of the light guide plate 4. In addition, prismatic protrusions extending in a direction substantially orthogonal to the incident surface 5 and protrusions formed on the back surface 7 and the exit surface 10 of the light guide plate 4, extending in a direction substantially orthogonal to the incident surface 5. A prism-like protrusion may be used. Further, the directional emission imparting means is a rough surface formed on the back surface 7 and / or the emission surface 10 of the light guide plate 4 to such an extent that light emitted from the emission surface 10 can maintain a desired directional emission property. May be. Further, the directional emission imparting means is an emission promotion pattern formed on the back surface 7 and / or the emission surface 10 of the light guide plate 4, and the light emitted from the emission surface 10 can maintain a desired directional emission property. It may be formed to the extent. In addition, as an emission promotion pattern, projections or dents such as hemispherical, pyramidal, and conical shapes are conceivable. Here, the directional emission property means that a large amount of light is emitted toward a specific emission angle direction, unlike a state where light is randomly diffused and emitted from the light guide plate 4. The directional emission providing means includes a scatterer in an amount that does not disturb the output directivity in the light guide plate 4, and includes a mode in which light is internally scattered by this scatterer and emitted directionally.

  Based on FIG. 5, when the angle (maximum inclination direction angle) formed by the maximum inclination direction R of the back surface 7 of the light guide plate 4 and one side surface 18 of the light guide plate 4 is δ, the maximum inclination direction angle δ is expressed by Equation 1. The maximum inclination angle ε is expressed by Equation 2.

以上のようにして決定される最大傾斜方向角δ及び最大傾斜角εは、光制御部材１１の突起２０の傾斜角θや求められる出射光特性に応じて、最適の数値が設定される。

The maximum inclination direction angle δ and the maximum inclination angle ε determined as described above are set to optimum numerical values according to the inclination angle θ of the protrusion 20 of the light control member 11 and the required outgoing light characteristics.

  FIG. 6 is a diagram for explaining the operation of such a light guide plate 4. As shown in FIGS. 6A and 6B, among the light incident from the thin side (B side) of the incident surface 5 of the light guide plate 4, the light spreading in the direction parallel to the incident surface 5 is on the thin side ( The light is easily guided from the (B side) to the thick side (A side). The light guided to the side surface 18 side of the light guide plate 4 is emitted from the vicinity of the incident surface 5 side and from the vicinity of the side surface 18 side by the action of the emission promoting means (for example, the protrusion 15) of the light guide plate 4. In addition, the light is emitted from one side 18 to the outside, reflected by a reflection member such as a frame, and re-entered the light guide plate 4. The light is emitted from the vicinity of the incident surface 5 and from the vicinity of the one side 18. Emission at the part that was difficult to do is prompted. Also, as shown in FIGS. 6A and 6C, the other side surface 19 side of the light guide plate 4 is thinner than the one side surface 18 side, so that the incident surface out of the light incident from the incident surface 5. 5, the number of times the light traveling toward the end surface 16 located on the opposite side of 5 is reflected by the exit surface 10 and the back surface 7 of the light guide plate 4 is greater than the number of reflections of the light propagating on one side 18 side of the light guide plate 4, The amount of light emitted in the vicinity of the incident surface 5 increases, and the emission at the portion that was difficult to emit conventionally is promoted. As a result, the light guide plate 4 according to the present embodiment can achieve uniform emission light luminance of light emitted from the entire emission surface 10.

(Light control member)
The light control member 11 is formed into a film shape with a resin material (for example, polyethylene terephthalate (PET), PMMA, PC) having excellent light transmittance, and the planar shape is guided as shown in FIGS. It is formed so as to have a rectangular shape that is substantially the same as the exit surface 10 of the optical plate 4. Then, the light control member 11 has a direction oblique to the incident surface 5 of the light guide plate 4 at an inclination angle θ on the side facing the emission surface 10 of the light guide plate 4 (the lower surface side in FIGS. 1 and 4). A large number of prism-shaped protrusions 20 extending in parallel (continuously upward at an inclination angle θ from the incident surface 5 to one side surface 18) are formed in parallel (see FIG. 2). The prism-shaped protrusion 20 of the light control member 11 is formed in a substantially triangular shape in cross section, and is emitted from the light guide plate 4 in a virtual plane orthogonal to the incident surface 5 of the light guide plate 4 and orthogonal to the output surface 10. It functions to deflect the light emitted from the surface 10 toward the normal direction of the emission surface 10 of the light guide plate 4.

  In the light control member 11 shown in FIGS. 1 to 4, the inclination direction of the prism-shaped protrusions 20 is a direction that rises to the right with respect to the incident surface 5 of the light guide plate 4, but is not limited thereto. A light control member 11 (see FIG. 19) having a prism-like protrusion 20 in the direction of rising to the left with respect to the incident surface 5 of the light guide plate 4, or a prism-like protrusion extending in parallel to the incident surface 5 of the light guide plate 4. The use of the light control member 11 (FIG. 20) with 20 is conceivable. Among these, the surface light source device 2 using the light control member 11 formed with the prism-like projections 20 inclined in the upward direction with respect to the incident surface 5 of the light guide plate 4 is defined as a first mode (see FIG. 2). The surface light source device 2 that uses the light control member 11 formed with the prism-like protrusions 20 inclined in the upward direction toward the left shoulder with respect to the incident surface 5 of the light guide plate 4 is a second mode (see FIG. 19). The surface light source device 2 using the light control member 11 formed with the prism-like protrusions 20 extending in parallel to the four incident surfaces 5 is defined as a third mode (see FIG. 20).

(Light reflecting member)
The light reflecting member 8 is made by mixing a white pigment with a sheet of PET sheet having excellent light reflectivity and a metal having excellent light reflectivity such as aluminum on the surface of the sheet-like resin member (for example, PET sheet). The film-shaped member is a vapor-deposited member, and has a rectangular shape that is substantially the same as the back surface 7 of the light guide plate 4 as shown in FIGS. 1, 3, and 4. The light reflecting member 8 functions to reflect the light emitted from the back surface 7 side of the light guide plate 4 and return it to the inside of the light guide plate 4. The light reflecting member 8 has a housing (not shown) in which the light guide plate 4 is housed as a surface having excellent light reflectivity (whitened surface), and the housing itself having the light reflecting function. May be a light reflecting member. The light reflecting member 8 may be a mirror reflecting member made of silver or aluminum.

[Measurement result of emitted light brightness]
7 to 9 show the results of measuring the distribution of the emitted light luminance of the surface light source device 2 of the first aspect (see FIGS. 1 to 4) to which the present invention is applied. 10 to 12 show the results of measuring the distribution of the emitted light luminance of the surface light source device 2 of the second mode (see FIG. 19) to which the present invention is applied. FIGS. 13 to 15 show the results of measuring the distribution of emitted light luminance of the surface light source device 2 of the third aspect (see FIG. 20) to which the present invention is applied. On the other hand, FIGS. 16 to 18 show the results of measuring the distribution of emitted light luminance of the conventional surface light source device 102 shown in FIG.

7, 10, 13, and 16 schematically show the emission surfaces 21, 21, 21, 121 of the light control members 11, 11, 11, 111 of the surface light source devices 2, 2, 2, 102. , The emission light luminances at nine places on the emission surfaces 21, 21, 21, 121 are shown. That is, at three measurement points at substantially equal intervals in the X direction (lateral direction) along the incident surfaces 5, 5, 5, 105 of the light guide plates 4, 4, 4, 104, and the light guide plates 4, 4, 3 in the vicinity of the incident surfaces 5, 5, 5, 105 in the Y direction (longitudinal direction) orthogonal to the incident surfaces 5, 5, 5, 105 of 4, 104, the central portion, and the vicinity of the end surfaces 16, 16, 16, 116. A total of nine measurement points are determined. The average emitted light luminance is an arithmetic average of the emitted light luminance values for each area in FIGS. 7, 10, 13, and 16. Further, the emitted light luminance is the luminance (cd / m ² ) on the light control members 11, 11, 11, 111 measured from the normal direction of the emission surfaces 10, 10, 10, 110 at each measurement point. is there.

  8, 11, 14, and 17 are emitted from the emission surfaces 21, 21, 21, 121 of the light control members 11, 11, 11, 111 of the surface light source devices 2, 2, 2, 102. It is a figure which shows the light emission luminance distribution (emitted light luminance distribution of FIG.7, FIG.10, FIG.13, FIG.16) in three dimensions, and shows a pattern pattern for each emitted light luminance area of 0-500 thru | or 3500-4000. Instead, it is a three-dimensional representation. In FIG. 8, FIG. 11, FIG. 14, and FIG. The axis corresponds to the direction along the incident surfaces 5, 5, 5, 105 of the light guide plates 4, 4, 4, 104, and the Y axis corresponds to the incident surfaces 5, 5, 5, 105 of the light guide plates 4, 4, 4, 104. 105 corresponding to the direction orthogonal to 105, the Z-axis corresponds to the normal direction of the exit surfaces 10, 10, 10, 110 of the light guide plates 4, 4, 4, 104, and 0 to 4000 in 500 steps in the Z-axis direction. Represents the emitted light luminance (see FIGS. 1, 2, 19, 20, and 22).

  9, FIG. 12, FIG. 15, and FIG. 18 are two-dimensional representations of the three-dimensional emitted light luminance distributions shown in FIG. 8, FIG. 11, FIG. 14, and FIG.

  Further, as shown in FIGS. 2 and 19, the surface light source device 2 of the first form shown in FIGS. 7 to 9 and the surface light source device 2 of the second form shown in FIGS. The basic configuration is the same except that the inclination directions of the eleven prism-shaped protrusions 20 are reversed. That is, in the surface light source device 2 of the first embodiment, as shown in FIG. 2, the inclination direction of the prismatic protrusions 20 of the light control member 11 rises to the right with respect to the incident surface 5 of the light guide plate 4. It is configured. On the other hand, in the surface light source device 2 according to the second embodiment, as shown in FIG. 19, the inclination direction of the prism-shaped protrusion 20 of the light control member 11 rises to the left with respect to the incident surface 5 of the light guide plate 4. It is configured as follows.

  Further, in the surface light source device 2 of the third embodiment shown in FIGS. 13 to 15, as shown in FIG. 20, the prism-like protrusion 20 of the light control member 11 is in the direction along the incident surface 5 of the light guide plate 4 (X The basic configuration is the same as that of the surface light source device 2 of the first form and the second form except that it is formed in the direction).

  2, 19, and 20, the right end portion (one end 12) of the incident surface 5 of the light guide plate 4 is the thickest portion, and the incident surface 5 is incident from one side surface 18 on the right end portion side. The plate thickness is gradually reduced toward the longitudinal direction (X direction) of the surface 5 and the plate thickness is gradually reduced from the incident surface 5 toward the end surface 16 direction (Y direction).

  On the other hand, in the surface light source device 102 shown in FIGS. 16 to 18 and 22, the thickness of the light guide plate 104 gradually decreases at an inclination angle α as it goes in the direction perpendicular to the incident surface 105 (Y direction). However, the thickness of the light guide plate 104 is not gradually reduced in the direction along the incident surface 105 (X direction). The surface light source device 102 shown in FIG. 16 to FIG. 18 is configured such that the inclination direction of the prism-shaped protrusion 120 of the light control member 111 rises to the right (see FIG. 22).

  Comparing the first mode (FIGS. 7 to 9), the second mode (FIGS. 10 to 12), the third mode (FIGS. 13 to 15) and the conventional example (FIGS. 16 to 18), the average emitted light intensity Is slightly higher in the conventional example than in the first, second, and third aspects. However, in the first aspect, the second aspect, and the third aspect, the same emission light luminance region (an emission light luminance region (2500-3000) much higher than the average emission light luminance) 22 is provided at the central portion of the emission surface 21. In contrast to existing in a wide range, the conventional example has only the same light emission luminance range (2500-3000) 122 in a narrow range in the central portion of the emission surface 121, and variation in emission light luminance is large. Further, in the conventional example, as shown in FIG. 16, an area in which light hardly reaches the left and right end portions on the LED (lower) side is generated. On the other hand, as shown in FIGS. 7, 10, and 13, the first mode, the second mode, and the third mode are emitted light at a portion where the light on the left and right ends on the LED (lower) side is difficult to reach. Brightness can be increased.

  As a result, when the surface light source devices 2, 2, 2, 102 are used as backlights of the liquid crystal display panels 3, 3, 3, 103, the surface light source devices 2, 2, 2 of the first to third aspects are It is possible to illuminate a wide range with light having a uniform luminance as compared with the conventional surface light source device 102. Therefore, in the display device 1 using the surface light source devices 2, 2, and 2 of the first to third aspects, the display image on the liquid crystal display panel 3 is easier to see than when the conventional surface light source device 102 is used. Become.

  When comparing the first aspect and the second aspect, the value of the average emitted light luminance is higher in the first aspect than in the second aspect, and the luminance distribution of the emitted light is almost the same value in both the first and second aspects. It has become. Here, the luminance distribution is a numerical value obtained by dividing the lowest value among the emitted light luminances at nine measurement points by the maximum value, and is a numerical value that allows the variation degree of the emitted light luminance to be known. From such a comparison result, the surface light source device 2 of the first aspect can achieve a uniform surface illumination with higher brightness than the surface light source device 2 of the second aspect. However, the second mode is much superior in luminance distribution compared to the conventional example, and can achieve planar illumination that is much more uniform than the conventional example.

  Further, in the third aspect, when compared with the first aspect and the second aspect, the average emitted light luminance is larger than the other aspects, and the numerical value of the luminance distribution is slightly smaller than those of the first aspect and the second aspect. However, the third mode is far superior in luminance distribution numerical value as compared with the conventional example, and can achieve planar illumination much more uniform than the conventional example. Therefore, the surface light source device 2 according to the third aspect can be used when the generation of moire fringes does not become a problem when the liquid crystal display panel 3 is illuminated, and enables high luminance and uniform surface illumination. Become. On the other hand, in the surface light source device 2 according to the first and second aspects, since the prism-like protrusions of the light control member are formed to be inclined with respect to the incident surface of the light guide plate, the occurrence of moire fringes is a problem. And uniform surface illumination is possible.

  The surface light source device of the present invention can be widely used not only as a display device using a liquid crystal display panel as a member to be illuminated, but also as a surface light source for indoor lighting devices and advertising plates.

(A) is a disassembled perspective view of the surface light source device of the 1st aspect to which this invention is applied, and a display apparatus provided with the same, (b) is a figure which expands and shows the A section of (a), (c) is an enlarged view of a portion B in (a). It is a top view of the surface light source device of the 1st mode to which the present invention is applied. (A) is sectional drawing cut | disconnected and shown along the C1-C1 line | wire of FIG. 3, (b) is a figure which expands and shows the D section of (a). (A) is sectional drawing cut | disconnected and shown along the C2-C2 line | wire of FIG. 3, (b) is a figure which expands and shows the E section of (a). (A) is a perspective view of a light-guide plate, (b) is a figure which expands and shows the F section of (a), (c) cut | disconnects and shows along the C3-C3 direction of (a). It is an enlarged view. (A) is an external appearance perspective view for demonstrating the effect | action of a light-guide plate, (b) is a figure which shows typically the propagation state of the light which looked at the entrance plane of the light-guide plate from the direction orthogonal to an entrance plane, (c) is a figure which shows typically the propagation state of the light seen from the direction orthogonal to one side of a light-guide plate. It is a figure which shows the emitted light brightness in the output surface of the light control member of a 1st aspect by a numerical value for every 9 areas. It is the figure which showed the emitted light luminance distribution of FIG. 7 in three dimensions. It is the figure which showed the emitted light luminance distribution of FIG. 8 planarly. It is a figure which shows the emitted light brightness in the output surface of the light control member of a 2nd aspect by a numerical value for every 9 areas. It is the figure which showed the emitted light luminance distribution of FIG. 10 in three dimensions. It is the figure which showed the emitted light luminance distribution of FIG. 11 planarly. It is a figure which shows the emitted light luminance in the output surface of the light control member of a 3rd aspect numerically for every 9 areas. It is the figure which showed the emitted light luminance distribution of FIG. 13 in three dimensions. It is the figure which showed the emitted light luminance distribution of FIG. 14 planarly. It is a figure which shows the emitted light brightness in the output surface of the conventional light control member numerically for every 9 areas. It is the figure which showed the emitted light luminance distribution of FIG. 16 in three dimensions. It is the figure which showed the emitted light luminance distribution of FIG. 17 planarly. It is a top view of the surface light source device of the 2nd aspect to which this invention is applied. It is a top view of the surface light source device of the 3rd mode to which the present invention is applied. It is a disassembled perspective view of the surface light source device which shows a 1st prior art example. It is a disassembled perspective view of the surface light source device which shows a 2nd prior art example. It is a top view of the surface light source device which shows a 3rd prior art example, (a) is a whole top view, (b) is a top view which expands and shows a part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... Surface light source device, 3 ... Liquid crystal display panel (illuminated member), 4 ... Light guide plate, 5 ... Incident surface (side surface), 6 ... LED (light source), 10 ... ... Exit surface, 11... Light control member, 12... One end, 15... Projection (directional emission imparting means), 18.

Claims (6)

The light from the light source incident from the side surface is provided with a directivity in the process of propagating through the interior by the directivity output means, and is emitted from the output surface with a desired directivity,
The side surface has a rectangular shape in which the dimension in the width direction perpendicular to the thickness direction is larger than the dimension in the thickness direction,
A light guide plate characterized by gradually reducing the plate thickness as it goes away from the side surface, and gradually reducing the plate thickness as it goes away from one side surface orthogonal to one end side in the width direction of the side surface.   A surface light source device comprising: the light guide plate according to claim 1; and a light control member disposed so as to oppose the emission surface of the light guide plate.   3. The surface light source device according to claim 2, wherein the light control member includes a plurality of prismatic protrusions having a substantially triangular cross section extending in an oblique direction with respect to the side surface of the light guide plate.   The surface light source device according to claim 3, wherein the prismatic protrusion is formed to extend obliquely from the side surface toward the one side surface.   5. A display device comprising: the surface light source device according to claim 2; and a member to be illuminated illuminated by light emitted from the surface light source device.   6. The display device according to claim 5, wherein the illuminated member is a liquid crystal display panel.

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