JP2009080945A - Double-sided light-emitting face light source device, and liquid crystal display device using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided light-emitting face light source device and a liquid crystal display device in which an outline of a sub liquid crystal is not visually recognized, and increase in the number of parts and increase in man-hour can be suppressed to the minimum. <P>SOLUTION: This is the double-sided light-emitting face light source device and the liquid crystal display device in which the main liquid crystal panel 11 is arranged on one face side of a light guide plate 3 to irradiate light from a light source (LED chip 2) from both faces, and a sub liquid crystal panel 12 smaller in the area than that of the main liquid crystal panel 11 is arranged on the other face side. A transreflective sheet (selective reflection polarizing film 5f) is arranged on a sub liquid crystal panel 12 side face of the light guide plate 3. Otherwise, an area of an optical sheet group 5 arranged on the sub liquid crystal panel 12 side face of the light guide plate 3 is enlarged more than that of the sub liquid crystal panel 12, and made the area equal to that of the optical sheet group 4 of the main liquid crystal panel 11 side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a double-sided light emitting surface light source device corresponding to a main liquid crystal panel and a sub liquid crystal panel, and further relates to a liquid crystal display device incorporating the double-sided light emitting surface light source device.

  In recent years, liquid crystal display devices having features such as light weight, thinness, and low power consumption are widely used as display devices for information devices such as personal computers and word processors, and display devices for video devices such as televisions, video movies, and car navigation systems. . In many cases, such a liquid crystal display device adopts a configuration in which a backlight unit (surface light source device) for applying illumination light from behind the liquid crystal panel is incorporated in order to realize a bright display screen.

  Here, the backlight unit is classified into an edge light system and a direct system according to the location of the light source. For example, the edge light system is a system in which a point light source device such as an LED is disposed on the edge of a light guide plate facing a liquid crystal panel. The direct method is a method in which a plurality of straight tubular light sources such as fluorescent discharge tubes are arranged on the back surface of the liquid crystal panel, and a diffusion plate is arranged between the liquid crystal panel and the light source. Among these methods, the edge light method is advantageous in terms of thinning, and can be said to be a method suitable for a display device of a portable electronic device such as a mobile phone or a notebook personal computer.

  By the way, for example, the usage forms of mobile phones are diversified, and mobile phones including a main liquid crystal and a sub liquid crystal are widely used in order to cope with various usages (see, for example, Patent Document 1). ). For example, in a folding mobile phone, the main liquid crystal display is used in the opened state, and information such as incoming mail is confirmed by the sub liquid crystal in the closed state. In addition, mobile phones with cameras are used in such a way that both the main liquid crystal and the sub liquid crystal are used separately depending on the case where the user or the other person is photographed.

For this reason, the backlight for the main side and the sub side is also required for the backlight having the irradiation function of the liquid crystal display unit. In this case, if the main liquid crystal and the sub liquid crystal are irradiated on each side using two backlights, an increase in thickness and an increase in the number of parts cannot be avoided. Double-sided light-emitting backlights that illuminate the sub-side simultaneously are becoming mainstream.
JP 2005-202058 A

  As described above, the double-sided light emitting backlight has a function of simultaneously illuminating two liquid crystal panels (main liquid crystal panel and sub liquid crystal panel) with one backlight, but the main liquid crystal and the sub liquid crystal have different sizes. There is a big problem that the outline of the sub liquid crystal panel is visually recognized when the liquid crystal panel is viewed. In order to make the outline of the sub liquid crystal invisible from the main liquid crystal panel side, for example, it has been attempted to arrange a large number of optical sheets. However, for this reason, there is a problem that the number of members is increased and an assembly man-hour is required. Newly occurs.

  The present invention has been proposed in view of such a conventional situation, and the outline of the sub liquid crystal is not visually recognized, and the increase in the number of parts and the increase in the number of man-hours can be minimized. An object of the present invention is to provide a double-sided light emitting surface light source device and a liquid crystal display device.

  In order to achieve the above-mentioned object, a double-sided light emitting surface light source device according to the present invention has a main liquid crystal panel disposed on one side of a light guide plate that irradiates light from a light source from both sides, and the other side. A surface light source device in which a sub liquid crystal panel having a smaller area than the main liquid crystal panel is disposed, and a transflective sheet is disposed on a surface of the light guide plate on the sub liquid crystal panel side. .

  Alternatively, a surface light source in which a main liquid crystal panel is disposed on one side of a light guide plate that irradiates light from a light source from both sides, and a sub liquid crystal panel having a smaller area than the main liquid crystal panel is disposed on the other surface The apparatus is characterized in that the area of the optical sheet disposed on the surface of the light guide plate on the sub liquid crystal panel side is larger than the area of the sub liquid crystal panel.

  Furthermore, the liquid crystal display device of the present invention is characterized by having a main liquid crystal panel and a sub liquid crystal panel and incorporating the above-described double-sided light emitting surface light source device.

  By disposing the transflective sheet (selective reflective polarizing film) on the sub liquid crystal panel side of the light guide plate, the state in which the outline of the sub liquid crystal panel cannot be visually recognized from the main liquid crystal panel side is maintained, and the display quality is improved. Similarly, by enlarging the area of the optical sheet disposed on the surface of the light guide plate on the sub liquid crystal panel side to be larger than the area of the sub liquid crystal panel, the state in which the outline of the sub liquid crystal panel cannot be seen from the main liquid crystal panel side is maintained. After all, the display quality is improved. Moreover, since it is only necessary to add a transflective sheet (for example, a selective reflection polarizing film), an increase in the number of parts and an increase in the number of man-hours can be minimized.

  According to the present invention, it is possible to provide a double-sided light emitting surface light source device and a liquid crystal display device in which the outline of the sub liquid crystal is not visually recognized and the increase in the number of parts and the increase in the number of man-hours can be minimized. Is possible.

  Hereinafter, a double-sided light emitting surface light source device according to the present invention and a liquid crystal display device using the same will be described.

(First embodiment)

  FIG. 1 shows a basic configuration of a double-sided light emitting surface light source device (backlight unit) 1 to which the present invention is applied. As shown in FIG. 1, the backlight unit 1 of the present embodiment includes an LED chip 2 that is a point light source device, a light guide plate 3, and optical sheet groups 4 and 5 arranged on both surfaces of the light guide plate. The light from the LED chip 2 that is a point light source is converted into a surface light source by the light guide plate 3. The light incident on the light guide plate 3 is emitted from both surfaces of the light guide plate 3, and thus is configured as a double-sided light emission type backlight.

  The main liquid crystal side and the sub liquid crystal side of the light guide plate 3 are supported by the frames 6 and 7 of the liquid crystal display device, respectively, but the area of the opening 6a of the frame 6 on the main liquid crystal side is on the sub liquid crystal side. It is larger than the area of the opening 7a of the frame 7. This is because the display area of the main liquid crystal panel is larger than the display area of the sub liquid crystal panel.

  The optical sheet groups 4 and 5 are designed in consideration of uniform light and efficient irradiation, and are configured by combining, for example, a diffusion film and a prism film. In the case of this embodiment, each optical sheet group 4 and 5 is comprised by the three optical sheets 4a, 4b, 4c, 5a, 5b, and 5c, respectively. The optical sheets 4a and 5a are, for example, diffusion sheets, and the optical sheets 4b, 4c, 5b, and 5c are, for example, prism sheets (light collecting sheets).

  The diffusion sheet plays a role of diffusing and uniformizing the light transmitted through the light guide plate 3. For example, a film in which light diffusion particles are dispersed in a light-transmitting resin film is used. . As the resin film, for example, a film such as polyethylene terephthalate or polycarbonate is used.

  The prism sheet plays a role of condensing light in one direction to improve luminance, and is a film having a form in which prisms having a condensing function are arranged. The light transmitted through the light guide plate 3 and the diffusion films (optical sheets 4a and 5a) is aligned in a predetermined direction (a direction substantially perpendicular to the film surface) by the prism films (optical sheets 4b, 4c, 5b and 5c). Therefore, efficient light irradiation is performed, and as a result, luminance is improved.

  A characteristic of the surface light source device of the present embodiment is that the area of the optical sheet group 4 disposed on the main liquid crystal side of the light guide plate 3 and the area of the optical sheet group 5 disposed on the sub liquid crystal side are substantially the same. It is the same. As described above, the display area of the main liquid crystal panel is larger than the display area of the sub liquid crystal panel. Therefore, for example, as shown in FIG. 2, the size (area) of the optical sheet group 4 disposed on the main liquid crystal side is large, and the size (area) of the optical sheet group 5 disposed on the sub liquid crystal side is small. It is normal to do. In such a setting, there is a possibility that the outline of the sub liquid crystal may be seen when viewing the display from the main liquid crystal side. On the other hand, as described above, the size of the optical sheet group 5 on the sub liquid crystal side is enlarged, and the area of the optical sheet group 4 on the main liquid crystal side and the area of the optical sheet group 5 on the sub liquid crystal side are made substantially the same. Thus, the reflection of the contour of the sub liquid crystal on the main liquid crystal is reduced.

  The surface light source device having the above configuration is incorporated as a backlight unit in a liquid crystal display device. Next, a liquid crystal display device incorporating the above-described surface light source device will be described.

  FIG. 3 shows a schematic configuration of a liquid crystal display device in which a surface light source device (backlight unit) is incorporated. As shown in FIG. 3, the liquid crystal display device of the present embodiment includes a main liquid crystal panel 11, a sub liquid crystal panel 12, and the above-described surface light source device 1, and the periphery thereof is held by a resin frame 13 and integrated. It tries to become.

  The main liquid crystal panel 11 and the sub liquid crystal panel 12 are configured by enclosing a liquid crystal material between the array substrates 11a and 12a and the counter substrates 11b and 12b, respectively. The array substrates 11a and 12a have pixels corresponding to display pixels. Electrodes and switching elements (thin film transistors) are formed in a matrix. In addition, on the array substrates 11a and 12a, a signal line for sending an electric signal to the pixel electrode and a gate line for supplying a switching signal to the thin film transistor which is a switching element are wired orthogonally to each other. On the other hand, on the opposing substrates 11b and 12b, the opposing electrodes are formed on almost the entire surface with a transparent electrode material (for example, ITO), and a color filter layer is formed corresponding to each pixel. Further, polarizing plates 14, 15, 16, and 17 are bonded to the outer surfaces of the array substrates 11a and 12a and the counter substrates 11b and 12b, respectively, with their polarization axes orthogonal to each other.

  The main liquid crystal panel 11 and the sub liquid crystal panel 12 are mounted with an LSI for supplying a drive signal (here, only the LSI 18 of the sub liquid crystal panel 12 is shown), and the above-mentioned is based on the drive signal from the external circuit board. The switching element is driven to display an image. A region where this image display is performed is a display region, and the main liquid crystal panel 11 and the sub liquid crystal panel 12 have a display region in which a large number of pixels are arranged.

  The double-sided light emitting surface light source device 1 used as a backlight unit irradiates light from the back side of the main liquid crystal panel 11 or the sub liquid crystal panel 12 to make the display on the main liquid crystal panel 11 or the sub liquid crystal panel 12 bright and easy to see. Is. As described above, as described above, the light guide plate 3 for irradiating the light from the LED chip 2 as the light source to the back surfaces of the main liquid crystal panel 11 and the sub liquid crystal panel 12, and the light guide plate 3 An optical sheet group 4 disposed between the main liquid crystal panels 11 and an optical sheet group 5 disposed between the light guide plate 3 and the sub liquid crystal panel 12 are provided. The LED chip 2 as a light source is provided along at least one side of the light guide plate 3. In the present embodiment, the LED chip 2 is installed on the short side of the light guide plate 3.

  The frame 13 is formed of a resin material or the like, and is formed with a main liquid crystal accommodating portion 13 a that constitutes an accommodating space for the main liquid crystal panel 11 and a sub liquid crystal accommodating portion 13 b that constitutes an accommodating space for the sub liquid crystal panel 12. The main liquid crystal accommodating portion 13a is formed to support the periphery of the main liquid crystal panel 11, and the sub liquid crystal accommodating portion 13b is formed with an opening 13c corresponding to the display area of the sub liquid crystal panel 12. .

  Light emitted from the LED chip 2 that is a light source is guided to the light guide plate 3, passes through the light guide plate 3 and the optical sheet group 4, and is then irradiated to the main liquid crystal panel 11. Similarly, after passing through the light guide plate 3 and the optical sheet group 5, the sub liquid crystal panel 12 is irradiated. In the main liquid crystal panel 11 and the sub liquid crystal panel 12, the irradiated light is transmitted, and images such as characters and videos are displayed with a predetermined brightness.

  In the liquid crystal display device of this embodiment, the size of the optical sheet group 5 on the sub liquid crystal side is enlarged as described above, and the area of the optical sheet group 4 on the main liquid crystal side and the area of the optical sheet group 5 on the sub liquid crystal side are increased. Since they are substantially the same, the outline of the sub liquid crystal panel 12 is not seen from the main liquid crystal panel 11 side. Further, in the liquid crystal display device of the present embodiment, it is only necessary to change the size of the optical sheet, and it is not necessary to increase the number of parts and man-hours.

(Second Embodiment)
In the double-sided light emitting surface light source device and the liquid crystal display device of the present embodiment, the reflection of the outline of the sub liquid crystal panel 12 is eliminated by using a transflective sheet (here, a selective reflection polarizing film).

  FIG. 4 shows a schematic configuration of a liquid crystal display device incorporating the double-sided light emitting surface light source device of this embodiment. The only difference from the double-sided light emitting surface light source device and the liquid crystal display device of the first embodiment is the configuration of the optical sheet group 5 on the sub liquid crystal panel 12 side. Therefore, with respect to other components, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the optical sheet group 5 on the sub liquid crystal side is composed of two diffusion sheets 5d and 5e and one selective reflection polarizing film 5f.

  The selective reflection polarizing film 5f is obtained by integrating a prism film portion and a reflective polarizing film. Here, the prism film portion has the same form and function as the previous prism sheets 5b and 5c, and contributes to the improvement in luminance. The reflective polarizing film was developed based on the reflective polarizing technology, and plays a role of reflecting a part of light from the light source (LED chip 2) and returning it to the main liquid crystal panel 11 side. .

  As the selective reflection polarizing sheet 5f, a commercially available film can be used. Specific examples thereof include, for example, a product name DBEF manufactured by Sumitomo 3M Limited. The selective reflection polarizing sheet 5f can be greatly reduced in thickness as compared with the case where the prism film and the reflective polarizing film are separately used, the thickness of the double-sided light emitting surface light source device, and further the liquid crystal display device This is useful for further thinning.

  In the double-sided light emitting surface light source device and the liquid crystal display device of the present embodiment, the reflection of the contour of the sub liquid crystal panel 12 on the main liquid crystal panel 11 is reduced by the function of the selective reflection polarizing sheet 5f. Further, since the size of the optical sheet group 5 is enlarged to be substantially the same as the size of the optical sheet group 4 on the main liquid crystal side, the same effect as in the case of the first embodiment can be realized. In addition, it is possible to realize a liquid crystal display device that has a display quality superior to that of the first embodiment and has no sub-liquid crystal reflection. For example, not only when the sub liquid crystal panel 12 is a transflective liquid crystal panel, but also when the sub liquid crystal panel 12 is a transmissive liquid crystal panel, it is possible to maintain a state where the outline cannot be visually recognized. Furthermore, since only the configuration of the optical sheet group 5 needs to be changed, there is an advantage that an increase in the number of parts and an increase in man-hours can be minimized.

  In addition, as a structure of the said optical sheet group 5, it is not necessarily limited to what is shown in FIG. 4, A various change is possible. For example, the optical sheet group 5 may be a diffusion sheet, two or one condensing sheet (prism sheet), a transfer prevention sheet, and a selective reflection polarizing film in order from the light guide plate 3 side. Alternatively, as the optical sheet group 5, it is also possible to arrange only one white transflective sheet.

(Third embodiment)
In the double-sided light emitting surface light source device and the liquid crystal display device of the present embodiment, a sub-liquid crystal panel 12 is provided by arranging a transflective sheet (here, a selective reflection polarizing film) on the main liquid crystal side in addition to the sub liquid crystal side. This is to eliminate the reflection of the outline.

  FIG. 5 shows a schematic configuration of a liquid crystal display device incorporating the double-sided light emitting surface light source device of this embodiment. The only difference from the double-sided light emitting surface light source device and liquid crystal display device of the second embodiment is the configuration of the optical sheet group 4 on the main liquid crystal panel 11 side. Therefore, for the other components, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the optical sheet group 4 on the main liquid crystal side is also composed of two diffusion sheets 4d and 4e and one selective reflection polarizing film 4f. In this case, the selective reflection changing film 4f is arranged so that the polarization axis thereof is orthogonal to the polarization axis of the selective reflection polarizing film 5f of the optical sheet group 5 on the sub liquid crystal side.

  In the double-sided light emitting surface light source device and the liquid crystal display device of the present embodiment, the reflection from the sub liquid crystal side can be effectively controlled by the functions of the selective reflection polarizing sheet 4f and the selective reflection polarizing film 5f on the sub liquid crystal side. In addition, the reflection of the contour of the sub liquid crystal panel 12 on the main liquid crystal panel 11 is further reduced.

  The configuration of the optical sheet group 4 on the main liquid crystal side is not limited to that shown in FIG. 5, and various modifications can be made. For example, the optical sheet group 4 may be a diffusion sheet, two or one condensing sheet (prism sheet), a transfer prevention sheet, and a selective reflection polarizing film in order from the light guide plate 3 side. Further, the selective reflection polarizing film 4 f can be formed integrally with the polarizing plate 15 of the main liquid crystal panel 11. In this case, a hard coat may be applied to the surface. Furthermore, another diffusion sheet can be disposed on the selective reflection polarizing film 4f.

It is a schematic sectional drawing which shows the arrangement | positioning state of the component of the double-sided light emission surface light source device of 1st Embodiment. It is a schematic sectional drawing which shows an example of the double-sided light emission surface light source device whose optical sheet by the side of a sub liquid crystal is smaller than the optical sheet by the side of a main liquid crystal. It is sectional drawing which shows schematic structure of the liquid crystal display device of 1st Embodiment. It is sectional drawing which shows schematic structure of the liquid crystal display device of 2nd Embodiment. It is sectional drawing which shows schematic structure of the liquid crystal display device of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Double-sided light emission surface light source device, 2 LED chip, 3 Light guide plate, 4,5 Optical sheet group, 4f, 5f Selective reflective polarizing film (semi-transmissive semi-reflective sheet), 11 Main liquid crystal panel, 12 Sub liquid crystal panel, 13 Frame , 14, 15, 16, 17 Polarizing plate

Claims (7)

A double-sided light emitting surface light source in which a main liquid crystal panel is disposed on one side of a light guide plate that irradiates light from the light source from both sides, and a sub-liquid crystal panel having a smaller area than the main liquid crystal panel is disposed on the other side A device,
A double-sided light-emitting surface light source device, wherein a transflective sheet is disposed on a surface of the light guide plate on a sub liquid crystal panel side.   2. The double-sided light-emitting surface light source device according to claim 1, wherein the transflective sheet is a selective reflection polarizing film in which a prism sheet and a reflective polarizing sheet are integrated.   The double-sided light-emitting surface light source device according to claim 1 or 2, wherein an area of the optical sheet disposed on the surface of the light guide plate on the sub liquid crystal panel side is larger than an area of the sub liquid crystal panel.   A selective reflection polarizing film having a polarization axis substantially perpendicular to a polarization axis of the selective reflection polarizing film disposed on the surface on the sub liquid crystal panel side is disposed on a surface on the main liquid crystal panel side of the light guide plate. The double-sided light emitting surface light source device according to any one of claims 1 to 3. A double-sided light emitting surface light source in which a main liquid crystal panel is disposed on one side of a light guide plate that irradiates light from the light source from both sides, and a sub-liquid crystal panel having a smaller area than the main liquid crystal panel is disposed on the other side A device,
The double-sided light emitting surface light source device characterized in that the area of the optical sheet disposed on the surface of the light guide plate on the sub liquid crystal panel side is larger than the area of the sub liquid crystal panel.   The double-sided light-emitting surface light source device according to claim 1, wherein the light source is an LED, and is disposed to face an end surface of the light guide plate.   7. A liquid crystal display device having a main liquid crystal panel and a sub liquid crystal panel and incorporating the double-sided light emitting surface light source device according to any one of claims 1 to 6.

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