JPH0418301Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a liquid crystal display device. [Prior art and its problems] In recent years, liquid crystal television receivers have been developed as liquid crystal display devices using liquid crystal display panels, and are being put into practical use. And, the above liquid crystal display panel is
Since it does not emit light by itself, it is necessary to provide a reflective plate on the back side to use external light for display, and using external light works well in dark places where sufficient external light cannot enter. Since it is difficult to obtain an image with a good contrast, a light source such as an electroluminescent lighting panel is provided on the back side of the liquid crystal display panel, and this light source is turned on to emit light to illuminate the back side of the liquid crystal display panel. There are known devices that can display images with good contrast even in a dark place. This type of conventional LCD television receiver is
It is generally constructed as shown in FIGS. 7 to 9. FIG. 7 shows the external appearance of a small portable television receiver, and FIGS. 8 and 9 show its cross section. In Figures 7 to 9,
In the figure, 1a is a front case, 1b is a back case, and a display window 2 with a glass plate (or transparent plastic plate) 3 fitted on the front of the front case 1a.
A channel display section 4 and a speaker sound emitting section 5 are provided. In FIG. 7, 6 is a volume adjustment dial which also serves as a power switch, 7 is a tuning dial, 8 is a VHF-UHF changeover switch, and 9 is an antenna. In addition, in FIGS. 8 and 9, reference numeral 10 denotes a circuit board provided in the cases 1a and 1b in parallel with the front surface of the case;
is an LSI attached to the back surface of a circuit board 10, and this circuit board 10 is fixed to support legs 12, 12 provided in the back case 1b by screws or other means. A liquid crystal display for displaying television images is arranged on the front side of the circuit board 10, facing the display window 2. This liquid crystal display for displaying television images includes a twisted nematic type dot matrix liquid crystal display panel 13 and an illuminator provided on the back side of the liquid crystal display panel 13, for example, over the entire display area of the liquid crystal display panel 13. Electroluminescent lighting panel (hereinafter referred to as EL)
(abbreviated as illumination panel) 14.
Reference numeral 15 denotes a display support frame fixed to the front surface of the circuit board 10 by means of adhesive or screws. The panel 14 is a flat plate portion 15b of this support frame 15.
It is adhesively fixed to the board with double-sided adhesive tape or the like. Further, the liquid crystal display panel 13 is inserted through the flat plate portion 15b of the support frame 15 to form the circuit board 10.
Panel retainers 17, 17 are supported from the back side by interconnectors 16, 16 sandwiched between the terminal array portion of the liquid crystal display panel 13, and are screwed to the rising wall 15a of the support frame 15.
It is fixed by pressing both side edges from the front side. The EL lighting panel 14 utilizes a fluorescent material that emits fluorescent light when an electric field is applied, and a dielectric layer containing the fluorescent material is provided between a transparent full-surface electrode and a front electrode facing it. A capacitor is formed by sandwiching the two electrodes, and by applying an alternating current voltage between the two electrodes, the fluorescent material is made to emit light. Examples of the above-mentioned fluorescent substances include zinc sulfide, zinc sulfide selenide, zinc cadmium sulfide selenide, and the like, and by selecting this fluorescent substance, light of any color can be obtained. The terminals 14a, 14a of this EL lighting panel 14 are brought into contact with terminal electrodes (not shown) on the back surface of the circuit board 10 by bypassing the side edges of the circuit board 10, as shown in FIG. 9, and soldered as necessary. It is fixed by 18. Note that 27 is a light-shielding hood surrounding the display window 2, which can be attached as necessary. In conventional LCD television receivers equipped with illuminators that illuminate the liquid crystal display panel as described above, the illuminators are fixedly provided and always turn on during TV reception, regardless of the amount of surrounding light. There is. However, this type of LCD television receiver is portable and uses a battery as a power source, so if the illuminator is always turned on regardless of the amount of surrounding light as described above, the battery life will be limited. There was a problem that the life of the illuminating body itself was also shortened. In order to solve this problem, a method can be considered in which a switch for turning on/off the illuminant is provided separately from the power switch, and the illuminant is turned off in bright places. However, with this method, when the illuminator is turned off, the light source itself is in the optical path of the LCD panel, which reduces the light reflection efficiency of the LCD panel, making it impossible to obtain sufficient contrast even in bright places. There is a problem. [Purpose of the invention] The present invention was made in view of the above points, and its purpose is to display an image with sufficient contrast in both bright and dark places, and to illuminate the battery and liquid crystal display panel. It is an object of the present invention to provide a liquid crystal display device that can improve the life of an illuminator and has good portability. [Summary of the invention] The present invention provides a liquid crystal display device equipped with a liquid crystal display panel that displays images using natural light, in which the natural light from the back side of the liquid crystal display panel is emitted to the front side of the liquid crystal display panel. A light-emitting element that illuminates the liquid crystal display panel from the back side using power from the main body of the liquid crystal display device is removably provided on the optical path leading to the display, and observation can be performed using natural light or the illumination from the light-emitting body. That is. [Embodiments of the invention] Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the same members as those of the conventional liquid crystal television receiver shown in FIGS. 7 to 9 are given the same reference numerals and detailed explanations will be omitted. FIG. 1 shows the external appearance of a small portable television receiver according to the present invention, and FIG. 2 shows its cross section. Further, FIG. 3 shows a cross-sectional view of the EL lighting panel. In Figure 1, 61 is case 1
A lighting panel insertion slot provided on the top surface of a, 1b,
62 is a lid that covers this illumination panel insertion opening 61. The EL lighting panel 14 is set on the back side of the liquid crystal display panel 13 inserted into the cases 1a and 1b through the lighting panel insertion opening 61, and is also pulled out to the outside as necessary.
The EL lighting panel 14 can be set on the back side of the liquid crystal display panel 13 and the liquid crystal display panel 13 can be illuminated by the EL lighting panel 14, or the EL lighting panel 14 can be taken out to the outside and natural light can be used as explained in the conventional technology. The image is then displayed on the liquid crystal display panel 13. As shown in FIG. 3, the EL lighting panel 14 has an EL light emitting layer 72 provided over the entire surface of the housing 71, which is a flat plate whose surface is recessed except for the peripheral edge. , a total reflection plate 7 is provided on the back surface of the housing 71.
3 is provided. The EL light emitting layer 72 is a dielectric layer 7 containing a fluorescent substance that emits fluorescent light when an electric field is applied.
2a is sandwiched between a transparent front-side full-surface electrode plate 74a and a back-side full-surface electrode plate 74b made of metal to form a capacitor, and when an AC voltage is applied between the electrode plates 74a and 74b, a capacitor is formed. A light substance emits light. A pair of terminals 75a and 75 are provided on the front surface of the case insertion side of the EL lighting panel 14.
b, one terminal 75a is connected to the front-side full-surface electrode plate 74a via a lead (not shown), and the other terminal 75b is connected to the back-side full-surface electrode plate 7.
4b via a lead 76. In addition, in Figures 2 and 3, 77a and 77b are EL
These are panel contact pieces that come into contact with terminals 75a and 75b of the lighting panel 14, respectively, and their base ends are attached by solder 78 to lighting panel connection terminals (not shown) formed on the back surface of the circuit board 10. It is bent so as to go around the edge of the circuit board 10 so as to come into elastic contact with the terminals 75a and 75b from the surface side. Then, the EL lighting panel 14 is inserted into the cases 1a and 1b from the lighting panel insertion port 61 by removing the lid 62 covering the lighting panel insertion port.
The insertion end side of the EL lighting panel 14 that is pushed into the home position, that is, the position directly facing the back surface of the liquid crystal display panel 13, has spring contact pieces 77a and 77b. By elastically deforming it outward and entering the inside thereof, it is elastically held on the flat plate part 15b of the display support frame 15 by the spring contact pieces 77a and 77b, and the outer end of the EL lighting panel 14 is inserted into the lighting panel. It is adapted to be held in the mouth 61 as shown in FIG. That is, the spring contact pieces 77a, 77b
These not only serve as connections between the terminals 75a and 75b of the EL lighting panel 14 and the lighting panel drive circuit of the circuit board 10, but also serve as members for fixing the insertion end of the EL lighting panel 14. By configuring as described above, the EL lighting panel 14 can be attached and detached, and can be replaced with an EL lighting panel of a different luminescent color, for example. The drive control of the EL lighting panel 14 is performed by a control circuit shown in FIG. 4.
That is, in FIG. 4, numeral 31 is a signal line, to which a vertical synchronizing signal V.SYNC separated from the video signal by a synchronizing signal separation circuit in the television main body circuit (not shown) is applied. Then, a vertical synchronizing signal V・SYNC is applied to the signal line 31.
is input to the set terminal S of the R-S flip-flop 32, and is also input to the trigger terminal T of the retriggerable multivibrator 33. This multivibrator 33 has an output time width set to be sufficiently longer than the period of the vertical synchronizing signal V.SYNC, and its output is inputted to an AND circuit 34 together with a timing signal φ _h having a predetermined time width. The output of this AND circuit 34 is the flip-flop 3
2 as a reset signal. The Q side output of flip-flop 32 is sent to switching element 35 as an on/off control signal.
The switching element 35 is provided between the EL drive circuit 37 and a DC power supply 36 of, for example, 100V, which is obtained by boosting the battery voltage, and controls the supply of power to the EL drive circuit 37 on and off. The EL driving circuit 37 drives the EL lighting panel 14 with AC in synchronization with a clock pulse when the DC power supply 36 is supplied, and the details thereof will be described later. In FIG. 4 above, when the TV main circuit is tuned to the TV radio wave by the tuning operation, the vertical synchronizing signal V.SYNC is applied from the TV main circuit to the signal line 31, the flip-flop 32 is set, and its output is ” becomes. As a result, the switching element 35 is turned on, and the DC power supply 36 is supplied to the EL drive circuit 37. this
When the EL driving circuit 37 is supplied with the DC power supply 36, the EL driving circuit 37 drives the EL lighting panel 1 in synchronization with the clock pulse.
4 is driven with alternating current to emit light. The television screen is displayed in monochromatic color due to the light emission from the EL lighting panel 14. On the other hand, the vertical synchronization signal V.SYNC applied to the signal line 31 is input to the retriggerable multivibrator 33 and triggers this multivibrator 33. As described above, this multivibrator 33 has its output time width set to be sufficiently longer than the synchronization of the vertical synchronization signal V・SYNC.
is maintained in the triggered state while it is normally applied. While this multivibrator 33 is held in the triggered state, its side output is "0" and the gate of the AND circuit 34 is closed.
Therefore, even if the timing signal φ _h is applied to the AND circuit 34, the output of the AND circuit 34 is held at "0" and the flip-flop 32 is not reset. As a result, while the vertical synchronization signal V・SYNC is normally applied, the EL lighting panel 14
is driven to emit light. Therefore, in a state where the EL lighting panel 14 is driven to emit light as described above, a tuning operation is performed in order to receive other TV radio waves,
Meanwhile, the vertical synchronization signal V・SYNC is on the signal line 31
When the multivibrator 33 is no longer given to
returns to a stable state, and the output on that side becomes "1" and is input to the AND circuit 34. Therefore, when the timing signal φ _h is applied to the AND circuit 34, the output of the AND circuit 34 becomes "1" and the flip-flop 32 is reset. As a result, the output of the flip-flop 32 becomes "0", turning off the switching terminal 35 and cutting off the connection between the EL drive circuit 37 and the DC power supply 36. Therefore, the EL drive circuit 37 stops driving the EL lighting panel 14. Then, when the tuning operation for other TV radio waves is finished, the vertical synchronization signal V・SYNC is output again.
is now input to the signal line 31, and as a result, as described above, the EL drive circuit 37
Driving of the illumination panel 14 is started. That is,
EL lighting panel 1 while receiving TV signals
4, and when television waves are not being received normally, such as when tuning other channels, the driving of the EL lighting panel 14 is stopped to reduce power consumption. Next, details of the EL drive circuit 37 will be explained with reference to FIG. In the figure, 41 and 42 are power supply terminals, and one terminal 41 is supplied with a positive voltage of 100V from a DC power supply via a switching element 35.
The other terminal 42 is grounded. The above terminals 41, 4
Bridge-connected P channel type transistors 43, 44 and N channel type transistors 45, 46 are provided between the two. That is, terminal 4
1 is connected to the emitters of transistors 43 and 44, and its collectors are connected to transistors 45 and 44, respectively.
It is connected to the terminal 42 via the collector-emitter of 46. The collectors of the transistors 43 and 45 and the transistors 44 and 4 are connected in common.
The EL lighting panel 14 is connected between the collector 6 and the collector 6. In addition, the terminal 41 is connected to resistors 47 and 4.
8 to the collector of an N-channel transistor 49, and also to the collector of an N-channel transistor 52 via resistors 50 and 51. The emitters of the transistors 49 and 52 are connected to the terminal 4 through resistors 53 and 54, respectively.
Connected to 2. And transistors 45, 4
For example, a 400Hz clock pulse φ _A is placed at the base of 9.
is input to the bases of transistors 46 and 52 via the clock pulse _φA inverter 55. Further, the connection point between the resistors 47 and 48 is connected to the base of the transistor 44, and the connection point between the resistors 50 and 51 is connected to the base of the transistor 43. The EL drive circuit 37 configured as described above is
When clock pulse _φA is at high level (“1”), transistors 45 and 49 are on;
6 and 52 are turned off. When the transistor 49 is turned on, its collector current causes a voltage drop across the resistor 47, applying a forward bias to the base of the transistor 44, turning the transistor 44 on. On the other hand, when the transistor 52 is off, the base of the transistor 43 has
A power supply voltage of 100V is directly applied via the resistor 50. Therefore, the transistor 43 has a base
The emitters are at the same potential and turned off. In this way, when the clock pulse _φA is at a high level, transistors 45 and 44 are on, and transistors 46 and 4 are on.
3 is turned off, and the EL lighting panel 14 has +100V on the side connected to the transistor 44 and the terminal 42 on the other side.
It becomes the ground level through. Also, clock pulse _φA is at low level (“0”)
When , transistors 45 and 49 are turned off and transistors 46 and 52 are turned on. As a result, contrary to the above case, a voltage drop occurs across the resistor 50 and forward bias is applied to the transistor 43. Further, since the power supply voltage of 100V is directly applied to the transistor 44 via the resistor 47, the transistor 44 is turned off. Therefore, in the EL lighting panel 14, the side to which the transistor 43 is connected is at +100V, and the other side is at the ground level. In this way, the polarity of the voltage supplied to the EL lighting panel 14 is reversed in synchronization with the high and low levels of the clock pulse _φA , and the EL lighting panel 14 is driven with alternating current. If a portable small television receiver is constructed as in this embodiment,
As shown in the prior art, for example, images can be displayed using natural light by providing a reflective plate on the back side of a liquid crystal display panel, or the liquid crystal display can be displayed in a dark place by attaching a light source such as electroluminescence. Images can be displayed by illuminating the panel, and when using natural light, it is possible to display images from the back side of the LCD display panel.
Since the EL lighting panel can be removed, images can be displayed with sufficient contrast. In the above embodiment, a monochromatic color display can be performed by using the EL lighting panel 14 as a colored lighting panel, but it is possible to perform a monochromatic color display by using the EL lighting panel 14 as a colored lighting panel. If a color filter 28 is provided on the surface of the liquid crystal display panel 13 as shown in FIG. Alternatively, it is also possible to display a monochromatic color that is a combination of both of the photocoloring and the emission color of the EL lighting panel 14. The table below shows some examples of screen colors obtained by combining the emitted light color of the EL lighting panel 14 and the light coloring by the color polarizing plate and color filter 28.

【table】

[Effect of idea]

As detailed above, according to the present invention, in a liquid crystal display device equipped with a liquid crystal display panel that displays images using natural light, the above-mentioned A removable illuminator is provided that illuminates the liquid crystal display panel from the back side using power from the main body of the liquid crystal display device, so images can be displayed with sufficient contrast even in a dark place by attaching the illuminator. be able to. In addition, in areas where the surroundings are bright and there is no need for the illumination of an LCD panel, it is possible to reduce power consumption and improve battery life by receiving television without installing an illuminator. It is possible to improve usage efficiency and extend its lifespan. Furthermore, in this case, the illuminating body is no longer present on the optical path from when natural light enters the liquid crystal display panel to when it exits to the front side of the liquid crystal display panel on the back side of the liquid crystal display panel. Since unnecessary attenuation of natural light by the body is avoided, sufficient contrast can be obtained. Furthermore, since the illuminator uses the power source of the LCD device itself, the illuminator itself can be made smaller and lighter, making it easier to install, but even if it is attached to the LCD device itself, it will not significantly impair its appearance or portability. Never.

[Brief explanation of drawings]

Figures 1 to 5 show an embodiment of the present invention. Figure 1 is an external perspective view, Figure 2 is a vertical side view, Figure 3 is a cross-sectional view of the EL lighting panel, and Figure 4 is a cross-sectional view of the EL lighting panel.
Circuit configuration diagram showing the drive control section of the EL lighting panel,
Fig. 5 is a circuit configuration diagram showing details of the EL drive section in Fig. 4, Fig. 6 is a sectional view of a liquid crystal display panel showing another embodiment of the present invention, and Fig. 7 is a conventional liquid crystal television receiver. 8 and 9 are a cross-sectional bottom view and a side view, respectively. 1a, 1b...case, 2...display window, 13...
...Liquid crystal display panel, 14...Electroluminescence illumination panel, 31...Signal line, 32...
Flip-flop, 33... Retriggerable multivibrator, 35... Switching element, 37
...EL drive circuit, 61...Lighting panel insertion slot.

Claims (1)

[Claims for Utility Model Registration] In a liquid crystal display device equipped with a liquid crystal display panel that displays images using natural light, the liquid crystal display on the back side of the liquid crystal display panel after natural light enters the liquid crystal display panel. On the optical path leading to the front side of the display panel, an illuminator is removably installed to illuminate the liquid crystal display panel from the rear side using power from the main body of the liquid crystal display device, and natural light or the illuminator is used to illuminate the liquid crystal display panel from the back side. A liquid crystal display device that allows observation by illumination.