JP2002072234A - Liquid crystal display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display apparatus having a simple constitution, where the reduction of thickness and the miniaturization of the apparatus are attained. SOLUTION: The liquid crystal display apparatus is provided with a liquid crystal element 1, a control circuit for liquid crystal for controlling the liquid crystal display element 1, a printed board 2 for liquid crystal, disposed adjacently to the liquid crystal display element 1 and having the control circuit for liquid crystal provided on one surface thereof and an LED element 46 mounted on the printed board 2 for the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective, anti-transmissive, and transmissive liquid crystal display device provided in a portable terminal device, a personal computer, or the like.

[0002]

2. Description of the Related Art A liquid crystal display device is mainly used for a display device of a portable information terminal or a portable telephone, which is a mobile information terminal, and a light source of the liquid crystal display device is generally a cold cathode tube.
However, this cold cathode tube is not suitable for a portable information terminal or a cellular phone, which is particularly small and light because of its large volume such as a transformer of a driving inverter, peripheral circuit parts, and a connector. Therefore, a liquid crystal display device using LEDs instead of the cold cathode tubes has been proposed. The LED also has desirable features such as not requiring high frequency and high voltage, having excellent safety, and not being a source of radio interference.

FIG. 11 is an exploded perspective view of a conventional liquid crystal display device using an LED as a light source. 1 is a liquid crystal display element,
A liquid crystal printed circuit board 2 is located on one side of the short side. 3 arranged on the upper surface of the liquid crystal printed circuit board 2
This is a TCP on which an IC chip constituting a liquid crystal control circuit is mounted.

An LED 40 is a light source of the liquid crystal display device.
Unit. 41 is a lead frame type LED element having lead terminals extending from the package, and 42 is the L
This is a printed circuit board for LED elements on which a plurality of ED elements 41 are mounted. The LED element printed circuit board 42 includes an LED.
In addition to the element 41, a resistor 43 for controlling the current of the LED element 41, a diode 44 for preventing an overvoltage of the LED element 41, and a connector 45 with a lead wire for supplying power to the LED element 41 are mounted. ing.

[0005] Further, 5 is a light guide made of a light transmitting material,
Reference numeral 6 denotes a reflecting material that reflects light scattered by the light guide 5, 7 denotes a diffusing material that diffuses light emitted from the upper surface of the light guide 5, 8
Is a reflector for reflecting the irradiation light from the LED element 41. Reference numeral 9 denotes a chassis holding the above-described members 1 to 3, 40, 5 to 8, and 10 denotes a frame made of sheet metal or the like, which is a protection member for protecting the liquid crystal display element 1 from above.

FIG. 12 is a sectional view taken along line XX 'in FIG. Light emitted from the LED element 41 is reflected by the reflector 6 and the reflector 8 sandwiching the LED element 41 from above and below.
The light guide 5 facing the LED element 41 while reflecting at
Incident on the incident surface 5a. The light that has entered the light guide 5 has the lower surface of the light guide 5 covered with the reflecting material 6.
As the light travels rightward, the light exits from the exit surface 5b of the light guide 5. The emitted light is scattered by the scattering material 7 and then enters the lower surface of the liquid crystal display element 1 and passes therethrough. At this time, the liquid crystal display element 1 performs display using liquid crystal on the upper surface.

FIG. 13 shows a configuration diagram of the liquid crystal display device.
The liquid crystal control circuit 11 is configured by an IC chip mounted on the TCP 3 and mounted on the liquid crystal printed circuit board 2. The liquid crystal control circuit 11 receives a control signal S1 and a logic voltage V from a control unit (not shown) of the liquid crystal display device.
1 and the liquid crystal drive voltage V2, the liquid crystal display element 1 is controlled via the TCP 3 based on these inputs S1, V1, V2. On the other hand, the LED element printed circuit board 42
The LED element 41 mounted on is turned on and off by the LED element driving voltage V3 input from the control unit.

[0008]

As described above, in the conventional liquid crystal display device, the liquid crystal printed board 2 and the LED element printed board 42 are provided independently, and at least the liquid crystal drive voltage V2 and the LED element Two or more power supply circuits for supplying the driving voltage V3 were required. Therefore, it is necessary to secure a space for accommodating the two printed circuit boards 2 and 42 in the chassis 9, and it is not possible to cope with a reduction in thickness and size of the device. In addition, since the configuration is complicated, manufacturing and assembly costs are high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a liquid crystal display device having a simple structure in which the device is made thinner and smaller.

[0010]

In order to achieve the above object, a liquid crystal display device according to the present invention comprises a liquid crystal display element, a liquid crystal control circuit for controlling the liquid crystal display element, and an adjoining liquid crystal display element. And a printed circuit board provided with a liquid crystal control circuit on one surface, and an LED element as a light source, and the LED element is mounted on the printed board.

When the LED element is of a side view type in which light emitted from an LED chip is reflected by a package in a direction parallel to a mounting surface, lead terminals from the package are different from those of a conventional lead frame type. It does not extend, and the LED element is reduced in size.

When a light reflection film is formed by silk printing around a portion of the printed circuit board on which the LED elements are mounted, a reflector for reflecting light emitted from the LED elements is provided as in the prior art. No need.

Further, if an LED element drive voltage generating circuit for adjusting the liquid crystal drive voltage for driving the liquid crystal display element and outputting the same as the LED element drive voltage to the LED element is provided, the circuit for supplying the liquid crystal drive voltage is provided. The LED element driving voltage can be supplied to the LED element only by the power supply circuit.

In the above liquid crystal display device, output switching means for permitting and prohibiting output of the LED element driving voltage to the LED element by the LED element driving voltage generation circuit, and input of a control signal for controlling the liquid crystal display element. There is provided an LED element control circuit for controlling the output switching means according to the presence or absence of the control signal. If no control signal is input, the LED element control circuit prohibits the output switching means from outputting the LED element driving voltage. That is, the LED element does not light unless a display is made on the liquid crystal display element.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Note that members having the same configuration as the prior art shown in FIGS. 11 to 13 are denoted by the same reference numerals in the drawings.
Duplicate description will be omitted.

First, a first embodiment according to the present invention will be described. FIG. 1 is an exploded perspective view showing the liquid crystal display device of the present embodiment. As shown in the figure, in this embodiment, a plurality of LED elements 46 are mounted on the lower surface of the liquid crystal printed circuit board 2.

As shown in FIG. 2, which is a cross-sectional view taken along the line XX 'in FIG.
Is mounted on the liquid crystal printed circuit board 2, and is of a side view type in which emitted light is reflected by the package 46b and travels in a direction parallel to the mounting surface. The light exit surface of the package 46b faces the entrance surface 5a of the adjacent light guide 5. The lower surface of the liquid crystal printed circuit board 2 has L
The LED unit 4 is formed by mounting the diode 43 and the resistor 44 in addition to the ED element 46.

As described above, in the liquid crystal display device of the present embodiment, the LED element 46 is mounted on the liquid crystal printed circuit board 2 so that the printed circuit board is unified into one. Therefore, the number of components is reduced as compared with the conventional technique, and the chassis 9 can be reduced accordingly. In addition, costs for manufacturing and assembly can be reduced. In particular, since the connector 45 with a lead wire is not required (see FIG. 11), the work of laying the lead wire on the chassis 9 and the work of connecting the connector 45 to a device equipped with the liquid crystal display device such as a portable terminal device are eliminated. Therefore, it is even more effective for cost reduction.

The side view type LED element 4
6 is a conventional lead frame type LED element 41
Since it is smaller than that of FIG. 12 (see FIG. 12), the LED unit 4 is reduced in size, which is effective for making the chassis 9 thinner and smaller.

Further, the mounting position of the TCP 3 having the IC chip constituting the liquid crystal control circuit on the upper surface of the liquid crystal printed circuit board 2 is determined by its own mounting area. The mounting position is inevitably determined. Therefore, in the present embodiment, the configuration is such that the LED elements 46 are mounted on the lower surface of the liquid crystal printed circuit board 2 on which the TCP 3 is not mounted, so that they can be arranged freely.

Next, a second embodiment according to the present invention will be described. FIG. 3 is a partially enlarged view of a side cross section of the liquid crystal display device. The liquid crystal display device of the present embodiment has an LED element 46.
It is characterized by a configuration for guiding light emitted from the light guide 5 to the light guide 5, and the other configuration is the same as that of the first embodiment. That is, instead of the reflector 8 (see FIG. 2), a white light reflecting film 12 is formed on the lower surface of the liquid crystal printed circuit board 2 by silk printing. The light reflecting film 12 reflects the diffused light (arrow A in the figure) from the LED element 46.

As described above, when the light reflecting film 12 is provided on the liquid crystal printed circuit board 2 instead of the reflector 8, the number of parts is reduced and the cost for manufacturing and assembly can be reduced. In addition, silk printing for forming the light reflecting film 12 is as follows.
If silk printing and printing are performed in common for printing the arrangement area and number of each electric component mounted on the liquid crystal printed circuit board 2, the same process is required, so that it is more effective to reduce costs.

Next, a third embodiment according to the present invention will be described. The liquid crystal display device of the present embodiment has an LED element 46.
The configuration is characterized in that power is supplied to the power supply, and the other configuration is the same as that of the first embodiment. FIG. 4 shows a configuration diagram of this liquid crystal display device. As shown in the figure, the liquid crystal printed circuit board 2 is provided with an LED element drive voltage generation circuit 13 in addition to the liquid crystal control circuit 11.

The LED driving voltage generating circuit 13 inputs the liquid crystal driving voltage V inputted in the same manner as the liquid crystal control circuit 11.
2 and set it as LE driving voltage V3 for LE.
Input to the D element 46. Therefore, in the present embodiment, it is only necessary to provide a power supply circuit (not shown) for supplying the liquid crystal driving voltage V2, and the LED element driving voltage V
There is no need for a power supply circuit for supplying 3. Therefore, the configuration is simplified.

FIG. 5 shows an example of the LED element drive voltage generating circuit 13. The liquid crystal driving voltage V2 input to the input terminal 13a of the LED element driving voltage generating circuit 13 is a resistor R
1, the voltage drops by R2 and is input to the plus terminal 14a of the operational amplifier 14. The operational amplifier 14 amplifies and outputs the comparison voltage between the plus terminal 14a and the minus terminal 14b. The voltage at the output terminal 14c is fed back to the minus terminal 14b via negative feedback.
A constant voltage is obtained as the LED element drive voltage V3 at the output terminal 13b of the LED element drive voltage generation circuit 13.

As described above, the following effects can be obtained if the liquid crystal driving voltage V2 is amplified to obtain the LED element driving voltage V3. That is, as shown in FIG. 6, the liquid crystal drive voltage _VA generally tends to decrease as the ambient temperature increases. Therefore, in the present embodiment, the liquid crystal driving voltage V2 input to the liquid crystal control circuit 11 is adjusted according to the temperature change by the voltage adjusting circuit (not shown) provided in the power supply circuit.
Therefore, the LE obtained by the LED element drive voltage generation circuit 13
The D element drive voltage V3 also changes according to the ambient temperature.

The behavior of the LED element drive voltage V3 is conform to general LED element input allowable voltage V _B and trends of the LED element drive voltage V _C that decreases with increasing ambient temperature, as shown in FIG. 6 I do. Therefore, in the related art, the LED element driving voltage V3 is adjusted according to the temperature change by the voltage adjusting circuit provided in the power supply circuit. However, in the present embodiment, the voltage adjusting circuit is provided to adjust the LED element driving voltage V3. No need. Therefore, the structure is further simplified.

Next, a fourth embodiment according to the present invention will be described. The liquid crystal display device of the present embodiment has an LED element 46.
The configuration is characterized in that power is supplied to the power supply, and the other configuration is the same as that of the first embodiment. FIG. 7 shows a configuration diagram of this liquid crystal display device. The printed circuit board 2 for liquid crystal has a third
An LED element drive voltage generation circuit 13 is provided similarly to the embodiment, and L obtained by amplifying the liquid crystal drive voltage V2 is obtained.
The ED element drive voltage V3 is input to the LED element 46.

An LED element control circuit 15 is provided in the liquid crystal control circuit 11, and the LED element drive voltage generation circuit 13 controls the LED element drive voltage generation circuit 13 according to the presence or absence of the input of the control signal S1 to the liquid crystal control circuit 11. The signal S2 is input. Then, the LED element drive voltage generation circuit 13 allows and prohibits the LED element 46 from outputting the LED element drive voltage V3 according to the LED element control signal S2.

FIG. 8 shows an example of the LED element drive voltage generation circuit 13 of the present embodiment. The LED element drive voltage generation circuit 13 is characterized by the configuration of the output from the operational amplifier 14, and the other configuration is the same as the LED element drive voltage generation circuit 13 of the third embodiment shown in FIG. Here, an analog switch 16 is provided between the branch point 13c to the negative feedback and the output terminal 13b, and the analog switch 16 has a configuration in which the contact is switched by the LED element control signal S2.

The LED element control circuit 15 shown in FIG. 7 outputs the LED element control signal S2 when the control signal S1 is input to the liquid crystal control circuit 11, and outputs the LED element drive voltage V3 from the output terminal 13b. Analog switch 1
Switch 6 contacts. On the other hand, when the control signal S1 is not input to the liquid crystal control circuit 11, the LED element control signal S
2 and outputs the LED element driving voltage V3 to the output terminal 13b.
The contact of the analog switch 16 is switched so as not to output more.

That is, when a display is made on the liquid crystal display element 1, the LED element 46 is turned on.
The D element 46 is turned off. As described above, the present embodiment uses the LE
The management function of the D element 46 can be added to the liquid crystal control circuit 11.

Although the liquid crystal display devices according to the first to fourth embodiments have a back light type configuration, the present invention may of course be implemented with a front light type configuration. The fifth embodiment described below is a front light type liquid crystal display device. FIG. 9 is an exploded perspective view of the liquid crystal display device, and FIG. 10 is a cross-sectional view taken along line YY ′ in FIG.

As shown in the figure, a plurality of LED elements 46 are mounted on an upper surface of a liquid crystal printed circuit board 2 'located on one side of the long side of the liquid crystal display element 1, and an LED unit 4 is formed. . TCP3 is mounted on the lower surface. The light guide 5 is located above the liquid crystal display element 1,
The light incident surface 5a is connected to the package 46b of the LED element 46.
Are opposed to the emission surface. As described above, even in the front-light type configuration, when the LED element 46 is mounted on the upper surface of the liquid crystal printed circuit board 2 'on which the TCP 3 is mounted on the lower surface, the device can be made thinner and the same as in the first embodiment. Miniaturization can be achieved.

[0035]

As described above, in the liquid crystal display device of the present invention, since the LED element is mounted on the printed circuit board provided with the liquid crystal control circuit, the printed circuit board for the LED element and the connector with the lead wire are not required. Therefore, the number of parts is reduced as compared with the prior art, so that the cost for manufacturing and assembling can be reduced, and the device can be made thinner and smaller. In particular, by providing a liquid crystal control circuit on one surface of a printed circuit board and mounting an LED element on the other surface, the arrangement of the LED elements can be set freely.

Further, by using the side view type LED element, the configuration of the LED unit can be reduced as compared with the lead frame type LED element in which the lead terminals extend from the package. Therefore, it is effective in reducing the thickness and size of the device.

Further, when the light reflecting film is formed on the printed circuit board instead of the reflector for reflecting the light from the LED element, the cost for manufacturing and assembly can be reduced by reducing the number of parts. In particular, if this light reflection film is formed on the same plate as silk printing for printing symbols on a printed circuit board, there is no inconvenience such as an additional manufacturing process and an increase in cost.

Further, since the power supply can be shared by obtaining the LED element drive voltage from the liquid crystal drive voltage, the power supply circuit can be simplified and the cost can be reduced. Furthermore, if the power supply to the LED element is linked to the display of the liquid crystal display element, the turning on and off of the LED element can be controlled without using a special circuit.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a side sectional view of the first embodiment.

FIG. 3 is a side sectional view of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 5 is an electric circuit diagram of an LED element drive voltage generation circuit according to the third embodiment.

FIG. 6 shows a liquid crystal driving voltage, an LED input allowable voltage, and L
5 is a graph showing a temperature characteristic of an ED drive voltage.

FIG. 7 is a configuration diagram of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 8 is an electric circuit diagram of an LED element drive voltage generation circuit according to the fourth embodiment.

FIG. 9 is an exploded perspective view of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 10 is a side sectional view of the fifth embodiment.

FIG. 11 is an exploded perspective view showing an example of a conventional liquid crystal display device.

FIG. 12 is a side sectional view of the conventional liquid crystal display device.

FIG. 13 is a configuration diagram of the conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2 Printed circuit board for liquid crystal 2 'Printed circuit board for liquid crystal 3 TCP 4 LED element unit 12 Light reflection film 46 LED element 46a LED chip 46b Package

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01L 33/00 G02F 1/1335 530 F term (Reference) 2H091 FA14Z FA23Z FA45Z GA11 LA11 2H092 GA51 PA06 PA13 2H093 NC42 ND42 ND54 5F041 DC23 EE23 EE25 FF11 5G435 AA00 AA18 BB12 BB15 EE27 EE33 EE37 EE40 FF03 FF08 GG23 GG26

Claims (5)

[Claims] 1. A liquid crystal display device comprising: a liquid crystal display element; a printed circuit board provided with a liquid crystal control circuit disposed adjacent to the liquid crystal display element; and an LED element serving as a light source. Is a liquid crystal display device mounted on the printed circuit board. 2. The liquid crystal display device according to claim 1, wherein said LED element is of a side view type in which light emitted from an LED chip is reflected by a package in a direction parallel to a mounting surface. 3. The liquid crystal display device according to claim 1, wherein a light reflection film is formed by silk printing around a portion of the printed circuit board on which the LED elements are mounted. . 4. A liquid crystal driving voltage for driving the liquid crystal display element is adjusted, and the LED driving voltage is adjusted as the LED element driving voltage.
The liquid crystal display device according to any one of claims 1 to 3, further comprising an LED element drive voltage generation circuit that outputs the output to the D element. 5. An output switching means for permitting and inhibiting output of the LED element drive voltage to the LED element by the LED element drive voltage generation circuit, and presence or absence of a control signal for controlling the liquid crystal display element. And an LED element control circuit for controlling the output switching means in response to the control signal. If there is no input of the control signal, the LED element control circuit prohibits the output switching means from outputting the LED element driving voltage. 5. The method according to claim 4, wherein
3. The liquid crystal display device according to 1.