JP3567663B2 - Liquid crystal display panel and electronic device using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lighting device that emits planar light by an in-plane discharge generated between a pair of linear electrodes facing each other. The invention also relates to a liquid crystal display device using the lighting device. The invention also relates to an electronic device using the liquid crystal display device.
[0002]
[Prior art]
In recent years, liquid crystal display devices have been widely used as visible information display units for digital still cameras, video cameras, mobile phones, and various other electronic devices. When a liquid crystal display device is used in a digital still camera, a video camera, or the like, the liquid crystal display device often functions as a finder for confirming image pickup. When used in a mobile phone or the like, a liquid crystal display device is used to display a telephone number and other information.
[0003]
This liquid crystal display device displays visible information such as numbers, characters, and images by modulating light by controlling the orientation of liquid crystal.In general, a liquid crystal module having a driving circuit mounted on a liquid crystal panel includes: Further, it is constituted by mounting a lighting device, a reflector and the like.
[0004]
Conventionally, as shown in FIG. 8, a molded glass 52 having a space therein, a glass plate 53 overlapped and joined thereto, and a pair of electrodes 54a and 54a inserted therebetween are used as the lighting device. 54b is known. In the lighting device 51, when a predetermined voltage is applied between the electrode 54a and the electrode 54b, an in-plane discharge is generated between the electrodes, and based on the in-plane discharge, the rectangular outside of the glass plate 53 is formed. Surface light is emitted from the surface, that is, the light emitting surface 53a.
[0005]
By the way, as will be described later, the lighting device according to the present invention is required to provide a reflection area on the light emitting surface. A lighting device disclosed in Japanese Patent No. 53403 is known. However, the lighting device shown here does not use a so-called flat fluorescent tube based on in-plane discharge, and there is no idea of providing a reflection area on the light emitting surface. Japanese Patent Application Laid-Open No. 62-229283 discloses an illuminating device using a reflecting plate. However, this illuminating device does not use a flat fluorescent tube. There is no idea to provide a board.
[0006]
[Problems to be solved by the invention]
Now, the cross-sectional structure of the lighting device 51 according to the arrow AA in FIG. 8 is as shown in FIG. 9, and the curve B shows the light emission intensity distribution of this cross-sectional portion. The effective light emitting region D is a region that emits light to illuminate a desired region of the illumination target. For example, when the lighting device 51 is used as a backlight for a liquid crystal display device, the effective light emitting region D Corresponds to the visible information display area of the liquid crystal module. The visible information display area of the liquid crystal module is generally set to be equal to or smaller than the effective light emitting area D.
[0007]
With respect to the conventional lighting device 51, as shown by a light emission distribution curve B, the light emission intensity rises slowly from the edge of the light emitting surface 53a. That is, there is a problem that the light emission intensity decreases near the electrodes 54a and 54b. Therefore, when the illuminating device 51 is used as a backlight for a liquid crystal display device, there is a problem that an edge portion of visible information displayed on the liquid crystal display device is darker than a central portion. It has been observed that this problem occurs not only with respect to the AA cross section of FIG. 8, ie, the cross section across the electrodes 54a and 54b, but also with the CC cross section, ie, a cross section parallel to those electrodes.
[0008]
The present invention has been made in view of the above problems, and in a lighting device that performs planar light emission based on in-plane discharge by a linear electrode, a reduction in luminance at an edge of an effective light emitting region is achieved. It is an object of the present invention to prevent luminance unevenness and to obtain light emission of uniform luminance over the entire effective light emitting area.
[0009]
[Means for Solving the Problems]
The lighting device according to the present invention has a pair of electrodes opposed to each other, and has a planar shape that emits light to the outside through a rectangular light-emitting surface by a discharge generated by applying a predetermined voltage between the pair of electrodes. In the lighting device, a light reflecting member is provided at an edge along four sides on the light emitting surface.
Further, the light reflecting member disposed at the edge on the light emitting surface reflects light going to the outside through the light emitting surface to the inside.
[0010]
According to this lighting device, light that is going to radiate from the edge of the light emitting surface to the outside can be reflected by the light reflecting member to the inside of the lighting device and guided to the edge of the effective light emitting region. Can increase the light emission luminance at the edge of. As a result, it is possible to obtain light emission with uniform luminance over the front surface of the effective light emitting area of the light emitting surface. In particular, if a reflection area made of a light reflecting member is provided near the electrode at the edge of the light emission surface, light from the electrode can be effectively collected by the reflection area. The light emission luminance at the edge can be more reliably increased.
[0011]
The light emitting surface is often formed in a square shape as shown by reference numeral 18a in FIGS. However, the shape can be any other shape as needed. Further, the above-mentioned reflection region can be formed by any method. For example, a reflection region can be formed by arranging a reflection plate formed of a predetermined shape using a white resin on a light emitting surface. In this case, for example, white PET (polyethylene terephthalate) can be used as the white resin. Further, as a method of forming the reflection area, a method of printing white ink on the light emitting surface can be considered.
[0012]
The reflection region can be provided over the entire edge of the light emitting surface 18a as shown by reference numeral 4 in FIG. 4, or a pair of linear electrodes 20a and 20b can be provided as shown by reference numeral 4 in FIG. May be provided only at the edge along the line. Further, it can be provided at the edges F0, F0 that do not correspond to the linear electrodes 20a and 20b.
[0013]
It is desirable to include a conductive material in the reflection region. As a method of inclusion, a method is considered in which a conductive film is further superimposed on a white resin or the like provided on the light emitting surface as a reflection region. In addition, a method is also conceivable in which conductive particles are mixed in white ink, and a reflection region of a predetermined pattern is formed on the light emitting surface by printing using the white ink.
[0014]
When a conductive material is included in the reflective region in this manner, seed electrons that trigger the discharge when a discharge is generated between the pair of electrodes can be induced, so that the lighting device can be quickly and reliably turned on. . That is, the lighting startability is improved.
[0015]
Next, a liquid crystal display device according to the present invention includes a liquid crystal panel and a lighting device, wherein the liquid crystal display device displays visible information in an effective display area of the liquid crystal panel using light emission of the lighting device. The lighting device has a pair of electrodes facing each other, and emits light to the outside through a rectangular light-emitting surface by a discharge generated by applying a predetermined voltage between the pair of electrodes, so that four sides on the light-emitting surface A light reflecting member is disposed so as to overlap the pair of electrodes at an edge along the edge of the liquid crystal panel, and an inner edge of the light reflecting member is located within a light shielding area provided outside the effective display area of the liquid crystal panel. It is characterized by being located .
[0016]
According to this liquid crystal display device, by providing the reflection area on the light emitting surface of the lighting device, the light emission luminance at the edge of the effective light emitting area of the light emitting surface can be increased, and therefore, the effective light emitting area of the effective light emitting area can be increased. Brightness over the entire surface can be made uniform. In general, the effective light-emitting area of the lighting device corresponds to the display area of the liquid crystal display device. Therefore, as described above, the fact that the brightness of the edge of the effective light-emitting region of the lighting device can be increased means that the display area of the liquid crystal display device can be improved. This means that the edges can be brightly illuminated, and therefore, even when the display area of the liquid crystal display device is set wide, the entire area within the wide display area can be displayed with uniform brightness.
[0017]
In this liquid crystal display device, it is desirable that the reflection area provided on the light emitting surface of the lighting device is provided outside the display area of the liquid crystal panel. This can prevent the display area of the liquid crystal display device from being narrowed by providing the reflection area on the light emitting surface of the lighting device.
[0018]
By the way, in a general liquid crystal display device, a light-shielding region 16 may be formed outside the display region V of the liquid crystal module 2 as shown in FIG. If there is nothing around the display area V, light from a backlight (not shown) leaks from the outside of the display area V to the outside, and a high-luminance frame can be seen around the area V. This high-brightness frame may be uncomfortable for a viewer. The reason why the light shielding region 16 is provided around the display region V as described above is to prevent such light from leaking from around the display region V.
[0019]
In addition to providing the light-blocking region 16 as described above, in a general liquid crystal display device, the liquid crystal module 2 and a backlight are housed in a case 21, and only the display region V is externally exposed through an opening 21 a of the case 21. Exposure to In this configuration, there is no problem if the edge of the case opening 21a is located inside the light-shielding region 16, but usually, the width W of the light-shielding region 16 is very narrow, about 0.6 mm to 1 mm. Therefore, it is very difficult to attach the case 21 to the liquid crystal module 2 so that the edge of the case opening 21a enters the narrow light-shielding region 16, and in many cases, the edge of the case opening 21a and the light-shielding region 16 A gap G is formed between the outer edge and the outer edge. In this case, light from the backlight leaks to the outside through the gap G, so that a high-luminance frame can be seen around the display area V, which impairs the appearance.
[0020]
In view of such a situation, when forming a reflection area at the edge of the light emitting surface of the lighting device according to the present invention, the inner edge of the reflection area is positioned corresponding to the inside of the light shielding area in the liquid crystal module. Is desirable. With this configuration, the reflection area provided on the light emitting surface of the lighting device is always positioned outside the light-shielding area in the liquid crystal module without forming a gap, so that the reflection area is located outside the light-shielding area in the liquid crystal module. Light traveling toward the region is reflected inside by the reflection region and does not leak out. Therefore, as shown in FIG. 6, even if a gap G is generated between the case opening 21a and the light shielding region 16 when the liquid crystal module 2 is housed in the case 21, light from the backlight is Leakage to the outside from the gap G can be reliably prevented.
[0021]
Next, an electronic device according to the present invention is an electronic device including the above-described liquid crystal display device according to the present invention. The electronic apparatus includes at least a liquid crystal display device, a power supply unit that supplies power to the liquid crystal display device, and a control unit that controls the operation of the liquid crystal display device. Still cameras, video cameras, mobile phones, and various other electronic devices are conceivable.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 1 shows an embodiment of a lighting device and an embodiment of a liquid crystal display device according to the present invention. The liquid crystal display device 1 shown here includes a liquid crystal module 2, an illuminating device 3, and a rectangular annular reflecting member 4. The reflecting plate 4 is formed of an annular reflecting member 6 formed of a light reflecting material such as white PET (polyethylene terephthalate) and a conductive member formed of a conductive material such as aluminum foil and formed in the same shape as the reflecting member 6. The film 7 is formed by overlapping each other. Alternatively, the conductive film 7 can be formed by applying a paint containing aluminum particles to the reflective member 6.
[0023]
In the case of the present embodiment, the liquid crystal module 2 is configured by an active matrix type liquid crystal module using an MIM element as an active element. More specifically, the liquid crystal module 2 includes a pair of transparent substrates 8a and 8b as shown in FIG. On one transparent substrate 8a, a plurality of linear lead electrodes 11 are formed, a plurality of pixel electrodes 12 are formed between the lead electrodes 11, and each pixel electrode 12 and each lead electrode are formed. The electrodes 11 are connected by MIM elements (not shown). On the other transparent substrate 8b, a plurality of stripe-shaped transparent electrodes 13 are formed.
[0024]
The transparent substrates 8a and 8b are overlapped so that the lead electrode 11 and the transparent electrode 13 are orthogonal to each other, and the substrates are sealed with a sealing material 9 in a state where a predetermined gap, that is, a so-called cell gap is formed between the substrates. And a liquid crystal is sealed in the cell gap to form a liquid crystal panel. The liquid crystal module 2 is formed by fixing the driver ICs 14a and 14b to the transparent substrates 8a and 8b on the liquid crystal panel thus formed. Each of the driver ICs 14a and 14b is conductively connected to the lead electrode 11 and the transparent electrode 13, respectively, and applies a liquid crystal driving voltage to each electrode.
[0025]
In the liquid crystal module 2, individual pixels for image display are formed at points where each pixel electrode 12 and the transparent electrode 13 intersect, and a display region V is formed by a group of these pixels. An annular light-shielding region 16 is formed on one of the transparent substrates 8a and 8b by chrome (Cr) or the like so as to surround the display region V. The light-shielding region 16 prevents the leakage of light from around the display region V, so that a high-luminance frame can be seen around the display region V and the viewer does not feel uncomfortable.
[0026]
Returning to FIG. 1, the lighting device 3 includes a molded glass 17 having a space inside, a glass plate 18 to be overlapped and joined thereto, a pair of electrodes 20 a and 20 b inserted therebetween, and And a bottom reflector 19 disposed on the bottom surface of the molded glass 17. Reference numeral 18a indicates a rectangular outer surface of the glass plate 18, and this surface functions as a light emitting surface.
[0027]
When assembling the liquid crystal module 2, the reflection plate 4, and the lighting device 3 with each other, as shown in FIG. An opening 21a is formed on the upper surface of the case 21, and the display area V of the liquid crystal module 2 is exposed to the outside through the case opening 21a. Further, the reflection plate 4 is annularly disposed on the surface of the glass plate 18 of the lighting device 3, that is, over the entire area of the edge of the light emitting surface 18a. Further, the reflection plate 4 is provided in a region outside the display region V of the liquid crystal module 2. The inner peripheral edge 4 a of the reflection plate 4 is located at a position corresponding to the internal area of the light shielding area 16 formed in the liquid crystal module 2.
[0028]
Hereinafter, the operation of the illumination device and the liquid crystal display device having the above-described configurations will be described. In FIG. 3B, a predetermined voltage is applied between the electrode 20a and the electrode 20b. Then, an in-plane discharge is generated between the electrodes, and based on the in-plane discharge, planar light is emitted from the outer surface of the glass plate 18, that is, the light emitting surface 18a.
[0029]
On the other hand, in the liquid crystal module 2, in FIG. 2, the lead electrodes 11 are sequentially selected by the operation of the driver IC 14a on the MIM element side and a voltage is applied, while the opposing electrode is operated by the operation of the driver IC 14b on the opposite substrate side. 13 is selected and a voltage is applied. In this manner, some of the plurality of pixel electrodes 12 arranged in a matrix are selected, and a voltage equal to or higher than the threshold voltage is applied to the MIM element attached thereto to make the MIM element conductive. The video signal is written to the liquid crystal capacitance in each of the individual pixels. Further, during the non-selection period, the MIM element is turned off to prevent leakage of the video signal. Thus, the desired orientation of the liquid crystal in the pixel is controlled to modulate the light from the light emitting surface 18a of the illuminating device 3, thereby displaying visible information such as characters and figures in the display area V.
[0030]
In FIG. 3B, when the lighting device 3 emits light, the light emitted at the edge of the light emitting surface 18a is reflected by the reflecting member 6 of the reflecting plate 4 and returned to the inside of the lighting device 3 so as to be directed to the outside. Leakage is prevented, and further, the light is reflected by the bottom reflector 19 and radiated to the outside through the edge of the effective light emitting region D (that is, the display region V). As a result, the light emission luminance at the edge of the effective light emission area D is increased, and therefore, the luminance in the entire area within the effective light emission area D becomes uniform as shown by the light emission distribution curve E. This phenomenon is not limited to the AA cross section in FIG. 3A, but also occurs in the CC cross section. As a result, the entire effective light emitting region D emits light with uniform luminance. By this uniform light emission, the entire display area V of the liquid crystal module 2 can be displayed with uniform luminance.
[0031]
In FIG. 1, in a region H of the light-emitting surface 18 a of the lighting device 3 which is close to the electrodes 20 a and 20 b, the luminance is particularly low and often dark. However, according to the present embodiment in which the reflection plate 4 is provided at the edges along the electrodes 20a and 20b, it is possible to reliably prevent the brightness from decreasing at such edges. Further, in the present embodiment, since the reflection plate 4 is configured to include the conductive film 7, when starting lighting of the lighting device 3, seed electrons serving as triggers of discharge can be easily induced. The device 3 can be stably and smoothly turned on. That is, a stable lighting startability can be obtained.
[0032]
Further, in the present embodiment, since the reflector 4 is provided outside the display area V of the liquid crystal module 2, there is no fear that the provision of the reflector 4 lowers the light emission luminance at the edge of the display area V. Further, in the present embodiment, since the inner peripheral edge 4a of the reflection plate 4 is located at a position corresponding to the internal area of the light shielding area 16 of the liquid crystal module 2, a gap is provided between the case opening 21a and the light shielding area 16. Even when G is formed, the light traveling toward the gap G is blocked by the reflector 4. For this reason, light does not leak out from the gap G, so that a high-luminance frame or line does not enter the eyes of the viewer, and the viewing state can always be maintained in a favorable state.
[0033]
(2nd Embodiment)
FIG. 7 shows an embodiment of an electronic device according to the present invention. This embodiment is an embodiment in which the lighting device and the liquid crystal display device according to the present invention are used as a finder of a digital still camera as an electronic apparatus. While an ordinary camera exposes a photosensitive film with an optical image of a subject, this digital still camera generates an image signal by photoelectrically converting an optical image of the subject using an image sensor such as a CCD.
[0034]
This digital still camera includes a light receiving unit 27 provided on the front side of a camera case 26, a shutter button 28 provided on an upper surface of the camera case 26, and a liquid crystal display device 1 provided on the back side of the camera case 26. Having. The liquid crystal display device 1 functions as a finder for displaying a subject, and can be configured using, for example, a liquid crystal display device having the structure shown in FIG. The light receiving unit 27 includes a shutter that opens and closes in conjunction with a shutter button 28, an optical lens, and an image sensor such as a CCD camera.
[0035]
A circuit board 29 on which a control circuit is mounted is provided inside the camera case 26, and the control circuit includes a memory. Further, a video signal output terminal 31 and an RS-232C input / output terminal 32 are provided on the side surface of the camera case 26, and a television monitor 33 is connected to the video signal output terminal 31 as necessary. A personal computer 34 is connected to the RS-232C input / output terminal 32. The television monitor 33 includes a television signal reproduction circuit 36 and a CRT display 37.
[0036]
Since the digital still camera is configured as described above, the photographer turns the camera toward the subject and presses the shutter button 28. Then, the shutter opens in the light receiving unit 27, and an imaging signal corresponding to the subject is output to an output terminal of a CCD camera or the like. This imaging signal is stored in a memory on the circuit board 29 and output to the personal computer 34 and the television monitor 33 as necessary.
[0037]
In this embodiment, the liquid crystal display device 1 acting as a finder has the reflector 4 at the edge of the light emitting surface 18a of the lighting device 3 as shown in FIG. It is possible to increase the light emission luminance at the edge of D, that is, to emit light with uniform luminance over the entire effective light emitting region D. Therefore, if a finder is configured using the liquid crystal display device 1, a clear subject image can be displayed on the entire surface of the finder.
[0038]
(Other embodiments)
As described above, the present invention has been described using the preferred embodiments. However, the present invention is not limited to the embodiments, and can be variously modified within the scope of the invention described in the claims.
[0039]
For example, in the above-described embodiment, the reflection area is formed on the light emitting surface 18a by mounting the reflection plate 4 on the light emission surface 18a. However, instead of mounting the reflection plate 4, white ink or the like is printed. A reflection area can also be formed. Further, in the above embodiment, the conductive film 7 is included in the reflection plate 4, but the reflection plate 4 can be configured only by the reflection member 6 without including the conductive film 7. In addition, as a method of including a conductive material in the reflection region, a method of mixing conductive particles in white ink can be adopted in addition to a method of overlapping the conductive film 7 on the reflection member 6.
[0040]
The reflection area constituted by the reflection plate 4 or the like can be provided in a ring shape over the entire edge of the reflection surface 18a as shown in FIG. 1, but instead of this, as shown in FIG. Alternatively, it may be arranged only on the side along the electrode 20b. Also, it can be provided on other sides F0 and FO.
[0041]
Also, considering the liquid crystal display device of the present invention, in the embodiment shown in FIG. 1, an active matrix type liquid crystal module using MIM elements is used as the liquid crystal module 2, but any other type of liquid crystal module, For example, an active matrix type liquid crystal module using a TFT (Thin Film Transistor) or a simple matrix type liquid crystal module using no active element can be used.
[0042]
Further, in consideration of the electronic apparatus of the present invention, the embodiment shown in FIG. 7 is considered to be applied to a digital still camera. However, in addition to this, the present invention is applied to a video camera, a mobile phone, and various other electronic apparatuses. Of course, the invention can be applied.
[0043]
【The invention's effect】
According to the lighting device, the liquid crystal display device, and the electronic apparatus of the present invention, when performing planar light emission based on discharge by the electrodes, it is possible to prevent a decrease in luminance at the edge of the effective light emitting region, Uniform light emission without luminance unevenness can be obtained over the entire surface of the effective light emitting region.
[0044]
According to the lighting device of the present invention, it is possible to increase the light emission luminance of the portion by guiding light to a portion having a low light emission luminance that is likely to be generated along the electrode.
[0045]
According to the lighting device of the present invention, the entire area of the effective light emitting region can be made uniform in luminance by increasing the light emission luminance of the entire area of the edge of the effective light emitting area on the light emitting surface.
[0046]
According to the lighting device of the present invention, seed electrons that trigger discharge can be induced, so that the lighting startability can be improved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of a lighting device and a liquid crystal display device according to the present invention.
FIG. 2 is a plan view illustrating an example of a liquid crystal module.
FIG. 3 is a view showing a state where the liquid crystal display device of FIG. 1 is assembled and a light emission distribution state of the lighting device.
FIG. 4 is a perspective view showing an example of how to arrange a reflection area.
FIG. 5 is a perspective view showing another example of how to arrange the reflection areas.
FIG. 6 is a plan view showing a positional relationship between a light shielding area formed in the liquid crystal module and an inner peripheral edge of a case storing the liquid crystal module.
FIG. 7 is a perspective view illustrating an embodiment of an electronic apparatus according to the invention.
FIG. 8 is a perspective view showing an example of a conventional lighting device.
FIG. 9 is a diagram showing a light emission distribution of a conventional lighting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal module 3 Illumination device 4 Reflector 6 Reflector 7 Conductive films 8a, 8b Transparent substrates 14a, 14b Driver IC
Reference Signs List 16 Light-shielding area 17 Molded glass 18 Glass plate 18a Light-emitting surface 19 Bottom reflector 20a, 20b Electrode 21 Case 21a Case opening D Effective light-emitting area H of lighting device Dark area V Display area of liquid crystal module

Claims (4)

A liquid crystal display device having a liquid crystal panel and a lighting device, and displaying visible information in an effective display area of the liquid crystal panel using light emission of the lighting device,
The lighting device has a pair of electrodes facing each other, and emits light to the outside through a rectangular light-emitting surface by discharge generated by applying a predetermined voltage between the pair of electrodes,
A light reflecting member is disposed at an edge along four sides on the light emitting surface so as to overlap the pair of electrodes ,
The liquid crystal display device according to claim 1, wherein an inner edge of the light reflecting member is located in a light shielding area provided outside the effective display area of the liquid crystal panel . The liquid crystal display device according to claim 1, wherein the conductive film is provided before Symbol light reflecting member. The liquid crystal display device according to claim 1, wherein a reflection surface of the light reflection member is white. 4. An electronic apparatus comprising: the liquid crystal display device according to claim 1 ; a power supply unit that supplies power to the liquid crystal display device; and a control unit that controls an operation of the liquid crystal display device. .

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