JP2005092192A - Double-faced lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly irradiate two liquid crystal display panels which are arranged back to back and have different display areas. <P>SOLUTION: A larger panel 2 being a liquid crystal display panel which is arranged on one surface of a case 1 of electronic equipment and a smaller panel 3 with a smaller display area which is arranged on the other surface back to back overlap at least partly with each other in the thickness direction. Reflection parts 4a formed of uneven parts reflecting light inwards are provided on at least the top and bottom surfaces of a light guide plate 4 interposed between both panels. Prism sheets 9 and 19 having downward microprisms are arranged closely to the top and bottom surfaces of the light guide plate 4, and a black sheet 6 which is a lusterless light absorbing sheet, has nearly the same external shape as the larger panel 2 and is provided with a through hole 6a in nearly the same shape as the smaller panel 3 is arranged between the light guide plate 4 and smaller panel 3. The black sheet 6 makes the light output from the light guide plate 4 to the the larger panel 2 uniform over the entire display surface by adjusting partial differences of light reflection characteristics on the internal surface of the case 1 of the smaller panel 2 facing the light guide plate 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dual emission lighting unit that is disposed in the middle of two liquid crystal display devices disposed back-to-back on both sides of an electronic device and that irradiates both liquid crystal display devices from the back.

2. Description of the Related Art In recent years, liquid crystal display devices having a thin and easy-to-see backlight mechanism have been widely used as display devices for various electronic devices such as various personal computers, word processors, game machines, and mobile phones. Among them, there are those in which display panels of liquid crystal display devices are arranged back to back on both sides of a case of an electronic device. As a conventional backlight of such a display panel, various devices have been made to obtain a thin and uniform surface light source (for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document). 4). Further, there is known a brightness enhancement film having a number of microprisms on the surface thereof, which are arranged between a display panel and a surface light source and have a function of condensing a backlight in a user's vision (for example, non-patent document). 1).
Japanese Patent No. 2739730 Japanese Patent No. 2747241 JP 2004-78047 A Japanese Patent Application No. 2004-87409 Sumitomo 3M Co., Ltd. catalog, brightness enhancement film (BEF series, RBEF series)

  However, when two sets of lighting units are used to illuminate both liquid crystal display panels, the number of parts is large, the thickness of the lighting unit is increased, and the number of assembly steps is increased. Incurs high costs. Moreover, it becomes heavier and the thickness is increased, and the portability of the final product is deteriorated. Furthermore, since a dedicated light source is used for both display panels, the power consumption is large. On the other hand, in the technology for irradiating two liquid crystal display panels with different display areas arranged on both sides of a single light guide plate that emits light on both sides, the light reflection characteristics of the surface facing the light guide plate are small on the display panel side. However, since the display panel portion is different from the periphery thereof, there is a problem that the light output for irradiating the display panel having a large display area becomes non-uniform under the influence of the reflected light. In order to avoid this, it is necessary to additionally install a diffusion sheet outside the lighting unit, which causes a problem in that the light output decreases.

  The present invention has been made to solve such a conventional problem, and the object thereof is to provide uniform display surfaces of two liquid crystal display panels having different display areas arranged back to back in a case of an electronic device. It is providing the double-sided light emission lighting unit suitable for irradiating to.

  Means of the present invention for solving the above-mentioned problems comprises a light source and a light guide plate having a light-emitting surface disposed on both sides of the light source in the vicinity of the light source, and at least a part of each of them overlaps in the thickness direction. Double-sided light emitting illumination unit disposed between one liquid crystal display panel and a second liquid crystal display panel having a display surface smaller than the first liquid crystal display panel disposed back to back with the first liquid crystal display panel And a brightness enhancement film comprising a plurality of microprisms is disposed on at least one side of the light guide plate, and the second liquid crystal display panel side excluding a portion corresponding to the display surface of the second liquid crystal display panel A light-absorbing sheet is disposed on the surface.

  Further, the brightness enhancement film is a downward prism sheet in which a convex portion of the prism faces the light guide plate direction, and the light absorption sheet is a black sheet.

  The double-sided light emitting illumination unit according to claim 2, wherein a case for holding the first liquid crystal display panel also serves as the black sheet.

  The brightness enhancement film is an upward prism sheet in which convex portions of the prism face the light emission direction, and the light absorption sheet is a gray sheet.

  The double-sided light emitting illumination unit according to claim 2, wherein a case for holding the first liquid crystal display panel also serves as the gray sheet.

  Further, the upward prism sheets whose prism directions are orthogonal to each other are arranged in a stack.

  In addition, a transflective sheet is disposed between the light guide plate and the first liquid crystal display panel.

  The transflective sheet is a half mirror sheet.

  The transflective sheet is a transflective white diffusion sheet.

  Further, the light guide plate is characterized in that a reflective portion comprising a plurality of concave and convex portions is formed on at least one of the upper and lower surfaces.

  Further, the uneven portion is formed by a microprism.

  The microprism is an unequal side prism.

  Further, the brightness enhancement film having a size corresponding to the light guide plate is disposed on the second display panel side.

  According to the present invention, the first liquid crystal display panel including the light source and the light guide plate having the light emitting surface disposed on both sides of the light source and having light output surfaces on both sides, the first liquid crystal display panel overlapping at least a portion in the thickness direction, and In a double-sided light emitting illumination unit disposed between a first liquid crystal display panel and a second liquid crystal display panel having a display surface smaller than the first liquid crystal display panel disposed back to back, at least the light guide plate A brightness enhancement film composed of a plurality of microprisms is disposed on one side, and a light absorbing sheet is disposed on the second liquid crystal display panel except for a portion corresponding to the display surface of the second liquid crystal display panel. Therefore, the light is condensed in the user's field of view and the efficiency of the backlight is improved, and the light output of the liquid crystal display panel display surface can be made uniform.

  In addition, since the transflective sheet is disposed between the light guide plate and the first liquid crystal display panel, the output of irradiation light of both liquid crystal display panels can be extremely changed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a cross section of an essential part of an electronic apparatus incorporating a double-sided light emitting lighting unit according to the first embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view showing a portion A of FIG.

  First, the configuration of an electronic device incorporating the double-sided light emitting lighting unit according to the first embodiment of the present invention will be described. In FIG. 1, reference numeral 1 denotes a case of an electronic device such as a mobile phone. 2 is a large panel which is a first liquid crystal display panel disposed on one surface of the case 1, and 3 is a small liquid crystal display panel which is disposed back to back on the other surface of the case 1. It is a panel. The large panel 2 and the small panel 3 are at least partially overlapped in the thickness direction, and the display area of the small panel 3 is smaller than the display area of the large panel 2.

  4 is a light guide plate made of a translucent member, which emits light from a light source incident from the side surface from the upper and lower light exit surfaces, and a reflection portion 4a composed of an uneven portion is formed on at least one upper and lower surfaces of the light guide plate 4. ing. The plane of the light guide plate 4 is substantially the same shape as the display surface of the large panel 2, and the cross section is rectangular or wedge-shaped. As shown in FIG. 2A, the reflecting portion 4a is formed by continuously forming a plurality of microprisms parallel to the light incident side surface. The prism is preferably an unequal side prism with a long hypotenuse on the light source side. Moreover, the reflection part 4a may be a concavo-convex part formed by a plurality of bowl-shaped grooves as shown in FIG.

  Reference numeral 5 denotes a linear light source such as a plurality of light emitting diodes or fluorescent tubes arranged discretely along one side surface of the light guide plate 4. 6 is a light-absorbing sheet disposed between the light guide plate 4 and the small panel 3 to uniformly adjust partially different light reflection characteristics of the inner surface of the case 1 facing the light guide plate 4 on the small panel 3 side. The film-like black sheet with no gloss and has a function of absorbing almost all incident light. As shown in FIG. 1, the black sheet 6 has a planar shape substantially the same as that of the large panel 2, and has a through hole 6 a corresponding to the display surface of the small panel 3.

  Reference numeral 9 denotes a prism sheet as a brightness enhancement film in which a plurality of microprisms are formed on one side of the sheet in parallel with one side of the sheet. The prism sheet 9 has a size corresponding to the outgoing surface of the light guide plate 4 and is disposed so that the convex portion of the prism faces the light guide plate 4 side (hereinafter referred to as “downward”). Reference numeral 19 denotes a prism sheet that is made of the same material as the prism sheet 9 and is arranged in the same manner, but only the size corresponds to the small panel 3. The light source 5, the light guide plate 4, the black sheet 6, and the downward prism sheets 9 and 19 constitute a double-sided light emitting illumination unit.

  Next, the operation and effect of the first embodiment of the present invention will be described. The light emitted from the light source 5 enters from the side surface of the light guide plate 4 and propagates through the inside, is reflected by the reflecting portion 4a, and is uniformly emitted from the upper and lower surfaces of the light guide plate 4 to the outside. At this time, if the reflecting portion 4a is an unequal side microprism, the amount of emitted light on the upper and lower surfaces is substantially equalized. A part of the light emitted from the light guide plate 4 is reflected by the surface of the downward-facing prism sheet 9, but most of the light is transmitted and reaches the user's eyes by irradiating the large panel 2 and the small panel 3 from the back side. The light emitted obliquely from the light guide plate 4 is totally reflected by the prism surface when passing through the downward prism sheet 9 or 19, and is emitted in the front direction which is the required visual field, thereby improving the luminance.

  Most of the light emitted from the light guide plate 4 to the small panel 3 side is absorbed by the black sheet 6 having a high light absorption rate, and is reflected to the same extent as the slight reflected light on the small panel 3 surface and the downward prism sheet 19 surface. do not do. Accordingly, the reflected light from the small panel 3 side becomes substantially uniform, and even if the light output on the display surface of the large panel 2 is affected, luminance unevenness does not occur there.

  Next, the structure of the electronic device incorporating the double-sided light emitting illumination unit according to the second embodiment of the present invention will be described. FIG. 3 is a schematic view showing a cross section of the main part of an electronic apparatus incorporating a double-sided light emitting illumination unit according to the second embodiment of the present invention. In FIG. 3, reference numeral 8 denotes a half mirror sheet as a transflective sheet disposed between the light guide plate 4 and the large panel 2. The half mirror sheet 8 has a function of reflecting a part of incident light and transmitting the other part to divide the traveling direction of the light into two, thereby reducing the transmitted light output. Since other configurations are the same as those of the first embodiment, the same reference numerals and names are used for the same components, and detailed description thereof is omitted. The light source 5, the light guide plate 4, the black sheet 6, the half mirror sheet 8, and the downward prism sheets 9 and 19 constitute a double-sided light emitting illumination unit.

  Next, the operation and effect of the second embodiment of the present invention will be described. Similar to the effect of the first embodiment, the luminance of the display surface of the large panel 2 is uniform. Further, a part of the light emitted from the light guide plate 4 through the downward prism sheet 9 and emitted to the large panel 2 side is reflected by the half mirror sheet 8, so that the light output is partially reduced. On the other hand, the light emitted from the light guide plate 4 to the small panel 3 side is added with the reflected light f of the half mirror sheet 8, so that the light output is slightly increased. Therefore, the light output of both display panels can be changed extremely. For example, it is convenient when the electronic device is a mobile phone and it is desired to increase the output to the back surface.

  Next, the configuration of an electronic apparatus incorporating the double-sided light emitting illumination unit according to the third embodiment of the present invention will be described. FIG. 4 is a schematic diagram showing a cross-section of the main part of an electronic apparatus incorporating a double-sided light emitting illumination unit according to the third embodiment of the present invention. In FIG. 4, reference numeral 7 denotes a gray sheet as a light absorbing sheet disposed on the surface of the case 1 on the small panel 3 side so as to face the light guide plate 4. The gray sheet 7 has a function of reflecting part of light and absorbing light of other parts, and is for adjusting the reflection characteristics of the surfaces having partially different light reflection characteristics. The gray sheet 7 has substantially the same planar shape as the light guide plate 4 and has a through hole 7 a corresponding to the display surface of the small panel 3.

  Here, the convex portions of the prisms of the prism sheets 9 and 19 are arranged so as to face the light emitting direction (hereinafter referred to as “upward”). In addition, the upward prism sheets 9 are arranged in two layers so that the prism directions are perpendicular to each other. Since other configurations are the same as those of the first embodiment, the same reference numerals and names are used for the same components and detailed description thereof is omitted. The light source 5, the light guide plate 4, the semi-reflective absorption sheet 7 and the upward prism sheets 9 and 19 constitute a double-sided light emitting illumination unit.

  Next, the operation and effect of the third embodiment of the present invention will be described. Light incident on the prism surface of the upward prism sheet 9 or 19 at a total reflection angle or more becomes recycled light r that returns to the light guide plate 4 side without being refracted as shown in FIG. On the other hand, the reflected light f from the gray sheet 7 returns to the light guide plate 4 side. Therefore, the light output from the display surface of the large panel 2 can be obtained by using the gray sheet 7 set so that the intensity of the reflected light f is balanced with the intensity of the recycled light r on the small panel 3 side. It can be made uniform. In the first and third embodiments, the prism sheet 19 or 9 is omitted if the light absorption rate of the gray sheet 7 is sufficiently adjusted and the brightness on the small panel 3 side can be satisfied. You can also.

  The light output angle is narrowed by the prism action of the upward prism sheet 9 or 19, and the backlight efficiency is improved with respect to the display panel in which the upward prism sheets 9 and 19 are arranged by being condensed within the viewing angle of the user. . By arranging two upwardly facing prism sheets 9 or 19 whose prism directions are perpendicular to each other, the light in the vertical and horizontal ranges is condensed and the backlight efficiency is further improved.

  Next, the configuration of an electronic apparatus incorporating the double-sided light emitting illumination unit according to the fourth embodiment of the present invention will be described. FIG. 5 is a schematic diagram showing a cross-section of an essential part of an electronic apparatus incorporating a double-sided light emitting lighting unit according to the fourth embodiment of the present invention. As shown in FIG. 5, this embodiment is different from the third embodiment in that a half mirror sheet 8 is disposed between the large panel 2 and the upward prism sheet 9. Since other configurations are the same as those of the third embodiment, the same reference numerals and names are used for the same components, and detailed description thereof is omitted. The light source 5, the light guide plate 4, the gray sheet 7, the half mirror sheet 8, and the upward prism sheets 9 and 19 constitute a double-sided light emitting illumination unit.

  Next, functions and effects of the fourth embodiment of the present invention will be described. Similar to the effect of the third embodiment, the light output of the display surface of the large panel 2 becomes uniform. Further, the backlight efficiency for each display panel is improved. Further, the addition of the half mirror sheet 8 reduces the luminance of the display surface of the large panel 2, and instead increases the luminance on the small panel 3 side due to the reflection effect of the half mirror sheet 8. Therefore, the light output of both display surfaces can be changed extremely.

  Next, the configuration of an electronic apparatus incorporating the double-sided light emitting illumination unit according to the fifth, sixth, seventh and eighth embodiments of the present invention will be described. 6, 7, 8, and 9 are schematic views showing a cross section of an essential part of an electronic device incorporating a double-sided light emitting illumination unit according to the fifth, sixth, seventh, and eighth embodiments of the present invention. is there. The fifth, sixth, seventh, and eighth embodiments of the present invention differ from the first, second, third, and fourth embodiments in that only the size of the prism sheet, The prism sheet on the small panel 3 side is a prism sheet 9 having a size corresponding to the light guide plate 4. Since other configurations are the same as those of the first, second, third, and fourth embodiments, the same components are denoted by the same reference numerals and names, and detailed description thereof is omitted.

  Next, operations and effects of the fifth, sixth, seventh and eighth embodiments of the present invention will be described. A part of the light emitted from the light guide plate 4 toward the small panel 3 is absorbed by the outer surface of the light guide plate 4 and partially reflected. In the first, second, third and fourth embodiments, the prism sheet 19 on the small panel 3 side is small when viewed from the large panel 2, so that the reflection characteristics and the reflection characteristics of the surrounding surfaces are There was a need to harmonize. In this case, since the prism sheet 9 is a large surface, the reflected light and the transmitted light are the same on the entire surface of the prism sheet 9 and do not affect the light output of the display surface of the large panel 2.

  In the second and fourth and sixth and eighth embodiments described above, a transflective white diffusion sheet may be used instead of the half mirror sheet 8 which is a transflective sheet. In this case, the same effect as that of the half mirror sheet 8 is obtained. Further, in all the embodiments of the present invention, instead of disposing the light absorbing sheet, the case 1 holding the small panel 3 has the same function as the light absorbing sheet so that it also serves as the light absorbing sheet. May be.

  The present invention can be applied to an electronic device such as a mobile phone that has a liquid crystal display panel disposed back to back on both sides of the case.

It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is 1st embodiment of this invention. It is a partial expanded sectional view which shows the A section of FIG. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is 2nd embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is 3rd embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is the 4th embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is the 5th embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is the 6th Embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is the 7th Embodiment of this invention. It is a schematic diagram which shows the cross section of the electronic device incorporating the double-sided light emission illumination unit which is 8th embodiment of this invention.

Explanation of symbols

2 Large panel 3 Small panel 4 Light guide plate 4a Reflector 5 Light source 6 Black sheet 7 Gray sheet 8 Half mirror sheet 9, 19 Prism sheet

Claims (13)

  A first liquid crystal display panel comprising a light source and a light guide plate that is disposed close to the side surface and has light-emitting surfaces on both sides facing each other, and at least a part of each of them overlaps in the thickness direction, and the first liquid crystal display panel And a second liquid crystal display panel having a display surface smaller than the first liquid crystal display panel disposed back to back, and a plurality of micros on at least one side of the light guide plate A brightness enhancement film made of a prism is disposed, and a light absorbing member is disposed on the second liquid crystal display panel side except for a portion corresponding to the display surface of the second liquid crystal display panel. Double-sided lighting unit.   The double-sided light emitting illumination unit according to claim 1, wherein the brightness enhancement film is a downward prism sheet in which a convex portion of the prism faces the light guide plate direction, and the light absorbing member is a black sheet.   The double-sided light emitting illumination unit according to claim 2, wherein a case holding the first liquid crystal display panel also serves as the black sheet.   2. The double-sided light emitting illumination unit according to claim 1, wherein the brightness enhancement film is an upward prism sheet in which a convex portion of the prism faces a light emitting direction, and the light absorbing member is a gray sheet.   The double-sided light emitting illumination unit according to claim 4, wherein a case for holding the first liquid crystal display panel also serves as the gray sheet.   The double-sided light emitting illumination unit according to claim 4 or 5, wherein the upward prism sheets whose prism directions are orthogonal to each other are arranged in a stack.   The double-sided light emitting illumination unit according to any one of claims 1 to 6, wherein a transflective sheet is disposed between the light guide plate and the first liquid crystal display panel.   The double-sided light emitting illumination unit according to claim 7, wherein the transflective sheet is a half mirror sheet.   The double-sided light emitting illumination unit according to claim 7, wherein the transflective sheet is a transflective white diffusion sheet.   The double-sided light emitting illumination unit according to any one of claims 1 to 9, wherein a reflective portion including a plurality of concave and convex portions is formed on at least one of the upper and lower surfaces of the light guide plate.   The double-sided light emitting illumination unit according to claim 10, wherein the uneven portion is formed by a microprism.   The double-sided light emitting illumination unit according to claim 11, wherein the microprism is an unequal side prism. The double-sided light emitting illumination unit according to any one of claims 1 to 12, wherein the brightness enhancement film having a size corresponding to the light guide plate is disposed on the second display panel side.

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