JP2004078047A - Double-sided display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided display device which absorbs external light from the subdisplay side and shields the transmission light when a user looks at the main display of the double-sided display device, therefore, prevents the main display quality from being affected by the subdisplay side, has excellent portability and is low-cost. <P>SOLUTION: The double-sided display device is composed of a main display device 1 which consists of a light transmission plate 2 arranged proximately to the edge surface of a light source (LED3), an optical sheet 4 disposed on the light emitting surface (upper surface) 2a side of the light transmission plate 2, a main display panel 5 disposed on the upper surface of the optical sheet 4 and reflective sheet 6 disposed on the lower surface side of the light transmission plate 2 and a subdisplay panel 7 disposed back to back with the main display device 1. When the main display panel 5 is in a display state, electricity is applied and black display is imparted to the subdisplay panel 7 and the external light from the back surface is absorbed as a shielding means preventing the transmission of the external light from the back surface. Otherwise, the subdisplay panel 7 is set in black display state, that is, LED is set normally black. Thereby, transmission light from the back surface is shielded, the visibility of the main display is improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a double-sided display device used for a consumer device such as a personal computer, a printer, a PDA, a facsimile, a pager, and a mobile phone.
[0002]
[Prior art]
2. Description of the Related Art In recent years, liquid crystal display devices (LCDs) having a thin and easy-to-see backlight mechanism have been widely used as display devices for various electronic devices such as notebook personal computers, PDAs, and mobile phones such as mobile phones equipped with an optical communication function. I have. As a conventional double-sided display device having such an LCD, for example, an LCD backlight of a mobile phone will be described.
[0003]
FIG. 2 is a perspective view showing a state of use when the case of the mobile phone is opened. In FIGS. 2A and 2B, reference numeral 11 denotes a case body provided with a plurality of buttons (not shown); Is a display portion of the case hinged to the case body 11. Reference numeral 13 denotes a front-side liquid crystal display panel (main display panel) disposed on the facing side of the display unit 12, and 14 denotes a rear-side liquid crystal display panel (sub-display) disposed back to back with the main display panel 13. Panel).
[0004]
In FIG. 2A, as shown by an arrow A, external light (direct sunlight or the like) is received from the back surface, and transmitted light (arrow B) on the back (sub) display surface is used as shown in FIG. 2B. The image of the sub-display panel 14 floats on the front (main) display surface like a window 14A.
[0005]
FIG. 3 is an essential part cross-sectional view showing the structure of the display unit of the double-sided display unit of the mobile phone. 3, the main display device 15 will be described. Reference numeral 16 denotes a light guide plate on the side of the main display device, which is made of a light-transmissive member made of transparent plastic or the like. The light guide plate has a flat or wedge-shaped cross section and a substantially rectangular planar shape. The upper surface 16a of the light guide plate 16 is a light emitting surface, and the lower surface 16b is a light source disposed close to the end surface of the light guide plate 16, for example, irregular reflection such as minute unevenness which reflects light from the LED 17 in the direction of the upper surface 16a. A part is formed. On the light exit surface (upper surface 16a) side of the light guide plate 16, an optical sheet 18 which is a prism sheet or a light diffusion sheet is provided. The prism sheet condenses light and improves surface luminance. The light diffusion sheet is disposed above or below the prism and has a function of correcting unevenness in surface luminance. Further, a main display panel 13 provided on the upper surface of the optical sheet 18 and a reflection sheet 19 provided on the lower surface side of the light guide plate 16 are provided.
[0006]
3, the sub display device 20 will be described. With the same configuration as the main display device 15 described above, the light guide plate 21 on the sub display device side, the LED 22 disposed on the end face of the light guide plate 21, and the optical sheet 23 disposed on the light exit surface side of the light guide plate 21, A reflection sheet 24 is arranged on the side of the light guide plate 21 opposite to the light exit surface.
[0007]
The main display device 15 and the sub-display device 20 described above are housed in a case 25 back to back to form a double-sided display unit.
[0008]
Next, the operation of the main display device having the above configuration will be described. The LED 17 as the light source is fully lit at the time of an incoming call and during use. The light emitted from the LED 17 is introduced from the end face of the light guide plate 16 into the inside thereof, diffuses by repeating total reflection inside the light guide plate 16, and is upwardly reflected by the reflection surface of the lower surface 16 b of the light guide plate 16. Is projected from the upper surface (light emitting surface) 16a of the light guide plate 16 to the outside. The light emitted from the lower surface of the light guide plate 16 toward the reflection sheet 19 returns to the reflected light guide plate 16 and eventually exits from the upper surface 16a to the optical sheet 18 side. This light increases the brightness by the action of the optical sheet 18 and irradiates the main display panel 13 without unevenness. The same applies to the operation of the sub-display device 20 disposed back to back with the main display device 15 described above.
[0009]
Although the structure of the display unit of the double-sided display unit of the mobile phone described above uses two sets of lighting units, one set of lighting units that is further simplified will be described.
[0010]
FIG. 4 is a cross-sectional view of a main part showing the structure of the display unit of the double-sided display unit of the mobile phone. Referring to FIG. 4, the main display device 30 will be described. Reference numeral 31 denotes a light guide plate on the main display device side, and the configuration of the light guide plate 31 is the same as that of the above-described light guide plate. For example, an LED 32 is provided as a light source near the end face of the light guide plate 31. On the light exit surface (upper surface 31a) side of the light guide plate 31, an optical sheet 33 that is a prism sheet or a light diffusion sheet is provided. Further, a main display panel 34 provided on the upper surface of the optical sheet 33 and a reflection sheet 35 provided on the lower surface side of the light guide plate 31 are provided. The reflection sheet 35 is a semi-transmissive reflection film, and has a function of partially reflecting light from the light guide plate 31 and partially transmitting light.
[0011]
A sub display panel 36 is disposed on the lower surface of the reflection sheet 35 so as to be back to back with the main display device 30. The main display device 30 and the sub display panel 36 are housed in one case 37.
[0012]
The operation of the double-sided display unit having the above configuration will be described. The light emitted from the light source and the LED 32 is introduced into the inside of the light guide plate 31 from the end face thereof, and is diffused by repeating total reflection inside the light guide plate 31, and reflected upward by the reflection surface of the lower surface 31 b of the light guide plate 31. The emitted light is projected from the upper surface (light emitting surface) 31a of the light guide plate 31 to the outside. Part of the light that has exited to the reflection sheet 35 on the lower surface of the light guide plate 31 returns to the reflected light guide plate 31 and eventually exits from the upper surface 31a to the optical sheet side. The emitted light increases the brightness by the action of the optical sheet 33 and irradiates the main display panel 34 without unevenness.
[0013]
In addition, part of the light emitted from the lower surface of the light guide plate 31 to the reflection sheet 35 side passes through the reflection sheet 35 and irradiates the sub display panel 36.
[0014]
[Problems to be solved by the invention]
In the above-described double-sided display unit, as shown in FIG. 3, when two sets of lighting units are used, a special sheet having a light-shielding function is provided as a backlight sheet in order to prevent light leakage on each display surface. In some cases, as shown in FIG. 2B, when external light (arrow A) is received from the back (sub) side, the transmitted light on the back (sub) display surface is The light is transmitted to the front surface (main) side (arrow B), and rises in a window shape on the front (main) display surface, making it difficult to see the display surface. In addition, the number of lighting units is two, the number of components increases, the number of assembling steps is increased, and the use of special sheets further increases the cost. There has been a problem that the weight of the lighting unit becomes heavy and lacks portability.
[0015]
In addition, as shown in FIG. 4, when a single light source and a single light guide plate are used, the above-described cost and portability problems are solved. When receiving external light (arrow A), the transmitted light on the back (sub) display surface is transmitted to the front (main) side (arrow B), and the visibility of the front (main) is lacking. This tendency appears remarkably.
[0016]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a dual-sided display device, in which a user does not look at a back (sub) side when looking at a front (main) display. Even when receiving external light from the (sub) side, it does not affect the surface (main) display quality. Another object of the present invention is to provide an inexpensive double-sided display device that is excellent in portability.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a double-sided display device according to the present invention includes a light source, a light guide plate disposed close to an end face of the light source, and an optical sheet disposed on a light exit surface (upper surface) side of the light guide plate. A main display device including a front side liquid crystal display panel (main display panel) provided on an upper surface of the optical sheet; and a reflection sheet provided on a lower surface side of the light guide plate, and back to back with the main display device. In a double-sided display device provided with a sub-display device having a rear-side liquid crystal display panel (sub-display panel) disposed in the sub-display panel, when the main display panel is in a display state, the sub-display panel transmits external light from the back. It is characterized by providing a shielding means for preventing.
[0018]
Further, the shielding means for preventing transmission of external light from the back surface applies black electricity by applying electricity to the sub-display panel, and absorbs external light from the back surface in the black-displayed sub-display panel. It is characterized by having a function of blocking light outside the sub-display panel.
[0019]
The shielding means for preventing the transmission of outside light from the back surface causes the sub display panel to display black in a normally black state in which no electric power is applied, and the sub display panel in which the black display is performed to prevent the sub display panel from being exposed from the back. Light is absorbed, and the sub-display panel is provided with an external light blocking function.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a double-sided display device according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part showing a structure of a display unit of a double-sided display unit of a mobile phone according to an embodiment of the present invention. In FIG. 1, the main display device 1 will be described. The main display device 1 is the same as the prior art described with reference to FIG. That is, for example, an LED 3 is provided as a light source in the vicinity of the end face of the light guide plate 2. An optical sheet 4 that is a prism sheet or a light diffusion sheet is disposed on the light exit surface (upper surface 2a) side of the light guide plate 2. The main display panel 5 disposed on the upper surface of the optical sheet 4 and the lower surface (2b) side of the light guide plate 2 have a function of partially reflecting light from the light guide plate 2 and partially transmitting light. The semi-transmissive reflection sheet 6 is provided. A sub display panel 7 is disposed on the lower surface of the reflection sheet 6 so as to be back to back with the main display device 1. The main display device 1 and the sub display panel 7 are housed in one case 8.
[0021]
When the user is viewing the front (main) display, he or she does not look at the display on the back (sub) side, so that when the front (main) display is performed, electricity is applied to the sub display panel 7 to display black. This has a function of absorbing external light and preventing external light (arrow A) from the rear surface from passing through the sub-display panel 7 on the rear surface.
[0022]
The operation of the double-sided display unit having the above configuration will be described. The light emitted from the LED 3 serving as a light source is introduced into the inside of the light guide plate 2 from the end face, and is diffused by repeating total reflection inside the light guide plate 2, and is reflected upward by the reflection surface of the lower surface 2 b of the light guide plate 2. The headed light is projected from the upper surface (light emitting surface) 2a of the light guide plate 2 to the outside. A part of the light emitted from the lower surface of the light guide plate 2 toward the reflection sheet 6 returns to the inside of the light guide plate 2 that has been reflected, and eventually emerges from the upper surface 2a toward the optical sheet. The emitted light increases the brightness by the action of the optical sheet 4 and irradiates the main display panel 5 without unevenness. In addition, part of the light emitted from the lower surface of the light guide plate 2 to the reflection sheet 6 side passes through the reflection sheet 6 and irradiates the sub display panel 7.
[0023]
When the user views the front (main) display by opening the case of the double-sided display device, electricity is applied to the sub-display panel 7 on the back, and the display is black, so that external light from the back (arrow A) ) Are absorbed by the sub-display panel 7 displayed in black. Therefore, the external light from the rear (sub) display surface is shielded by the sub display panel 7 to prevent the transmission of the external light and does not float on the front (main) display, thereby impairing the display quality of the front (main). Never.
[0024]
Further, in consideration of the power consumption of the double-sided display device, the sub display panel 7 is displayed in black without applying electricity. By setting the so-called normally black state, the sub-display panel 7 absorbs transmitted light from the back. Therefore, the transmitted light on the back (sub) display surface does not float on the front (main) display, and the visibility of the front (main) display is improved.
[0025]
When the case is closed, a part of the light transmitted through the semi-transmissive reflection sheet 6 illuminates the sub display panel 7 so that the display on the sub display panel 7 can be visually recognized.
[0026]
【The invention's effect】
As described above, according to the present invention, when the user is viewing the front (main) display, the user applies electricity to the back (sub) side display device to display black, or the electricity is applied. By setting the normally black state, which is not performed, the external light from the back (sub) can be absorbed and the transmitted light can be shielded, so that the back (sub) display becomes a window on the front (main) display. It does not rise. Therefore, the display of the surface (main) is easy to see, and the visibility is improved.
[0027]
Further, it is possible to provide an inexpensive double-sided display device which has a small number of parts constituting the device, is lightweight, has good portability, and has excellent display quality.
[Brief description of the drawings]
FIG. 1 is a fragmentary cross-sectional view showing a structure of a display unit of a double-sided display unit of a mobile phone according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a state of use of a conventional mobile phone with a case opened.
3 is a cross-sectional view of a main part showing a structure of a display unit of a double-sided display unit of the mobile phone of FIG.
FIG. 4 is a cross-sectional view of a main part showing a structure of a display unit of a double-sided display unit of another conventional mobile phone.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main display device 2 Light guide plate 3 Light source (LED)
4 Optical sheet 5 Front (main) display panel 6 Reflective sheet 7 Back (sub) display panel

Claims (3)

A light source, a light guide plate disposed close to an end face of the light source, an optical sheet disposed on a light exit surface (upper surface) side of the light guide plate, and a front side liquid crystal display panel disposed on an upper surface of the optical sheet (Main display panel), a main display device including a reflection sheet disposed on the lower surface side of the light guide plate, and a rear liquid crystal display panel (sub display panel) disposed back to back with the main display device. In a double-sided display device provided with a sub-display device, when the main display panel is in a display state, the sub-display panel is provided with shielding means for preventing transmission of external light from the back surface. The shielding means for preventing transmission of external light from the back surface applies black electricity by applying electricity to the sub-display panel, and absorbs external light from the rear surface in the black-displayed sub-display panel. 2. The double-sided display device according to claim 1, wherein the panel has an external light shielding function. The shielding means for preventing the transmission of external light from the rear surface causes the sub display panel to display black in a normally black state in which no electricity is applied, and the black sub display panel controls external light from the rear. 2. The double-sided display device according to claim 1, wherein the sub-display panel has an external light shielding function by absorbing light.

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