JPH0764059A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crustal display device capable of automatically adjusting a frame frequency due to the change of a temperature and having excellent contrast in a wide temperature range by providing a control means consisting of a microcomputer varying the frame frequency without varying a circuit constant of a driving circuit according to the temperature and setting the program of the microcomputer. CONSTITUTION:By the CPU 21 of the microcomputer 2, m' pieces of dots independent of display is set in the direction of a segment electrode 31 in addition to mXn pieces of dots being a display area of a liquid crystal pannel 3, and the original display data corresponding to (m) pieces and the non-display data independent of display dealing with m' pieces are made coexist to be outputted to a segment driver 4. The frame frequency in such a case is changed by varying the m' being the number of pieces of dots independent of display. By the CPU 21, the m' where the display of the liquid crystal pannel 3 becomes optimum for a signal (a) from a temperature senser 1 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device having a good contrast in a wide temperature range.

[0002]

2. Description of the Related Art Generally, in a liquid crystal display device, the threshold voltage and the response speed change depending on the operating environment temperature, so that the contrast ratio changes greatly with temperature, and it is difficult to obtain a good display in a wide temperature range. there were.

In order to compensate for such a change in the contrast ratio due to a change in temperature, for example, the resistance of the clock generator of the drive circuit is formed by a thermistor, and the change in the resistance value of the thermistor due to a change in temperature is used to generate a clock. Adjusting the frequency (frame frequency) (Japanese Patent Laid-Open No. 4-204627)
No.) or a circuit for adjusting the frame frequency,
There is known one that adjusts a frame frequency according to a temperature change (Japanese Patent Laid-Open No. 4-324420).

[0004]

However, in the former case, it is difficult to select a thermistor having a characteristic such that a frame frequency with which the display is optimized can be selected. In the latter case, a circuit for adjusting the frame frequency is provided exclusively. Therefore, there is a problem that the circuit becomes complicated and the cost becomes high.

[0005]

In order to solve the above problems, the present invention provides a liquid crystal display device having a simple matrix type liquid crystal panel and a drive circuit for driving the liquid crystal panel by a voltage averaging method. In accordance with the above, the control means including a microcomputer for changing the frame frequency without changing the circuit constant of the drive circuit is provided.

[0006]

By setting the program, the frame frequency due to temperature change can be automatically adjusted, and a liquid crystal display device having a good contrast in a wide temperature range can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of the embodiment. Reference numeral 1 is a temperature sensor for measuring a use environment temperature and converting it into an electric signal a. Reference numeral 2 is for receiving a signal a from the temperature sensor 1 at that time. Microcomputer that controls the frame frequency (described later) so that it is optimal for the temperature of the
A display control for controlling the CPU 21 in which a predetermined processing program is stored and a common electrode described later to be sequentially selected and scanned according to an instruction of the CPU 21 and synchronously outputting a display data signal b to a segment electrode described below. And a liquid crystal controller 22 that outputs a signal c.

Reference numeral 3 denotes a simple matrix type liquid crystal panel. The liquid crystal panel 3 has a plurality of segment electrodes (signal electrodes) 31 arranged in the horizontal direction of the drawing and a plurality of common electrodes (scanning electrodes) 32 arranged in the vertical direction of the drawing. And a liquid crystal layer (not shown) made of a twisted nematic (TN) liquid crystal substance or a super TN liquid crystal substance, which are opposed to each other with a space therebetween. The number 32 is n, which constitutes a total of m × n dots (pixels).

Reference numeral 4 is a segment driver connected to the segment electrode 31 of the liquid crystal panel 3, and 5 is a common driver also connected to the common electrode 32. The segment driver 4 and the common driver 5 form a drive circuit, and The liquid crystal panel 3 is driven by the voltage averaging method (multiplex) according to the signals b and c.

By the way, normally, in the driving by the voltage averaging method, the display data signal b is a pulse which is time-divided, and each dot is intermittently subjected to voltage excitation in a certain cycle, and is transmitted to the segment driver 4. When the number of data of the display data signal b to be generated is D bits / second, the frame frequency fr at this time can be expressed by D / (m × n) Hz.

The present invention changes the frame frequency according to the temperature without changing the circuit constant (driving voltage). Specifically, as shown in FIG.
CPU 21 sets m ′ dots which are irrelevant to the display in the direction of the segment electrode 31 in addition to the m × n dots which are the display area of the liquid crystal panel 3, and the display data signal b is
Original display data corresponding to m pieces and non-display data irrelevant to display corresponding to m'pieces are mixed and output to the segment driver 4. The frame frequency fr ′ in this case is D / ((m + m ′) × n)
It can be expressed in Hz and is lower than the frame frequency fr. That is, the frame frequency is changed by changing "m '", which is the number of dots unrelated to the display.

The liquid crystal panel 3 has a slow response speed when the temperature is low and a fast response speed when the temperature is high.
When the response speed is high, the contrast ratio is low and the display is difficult to see. To compensate for this, when the temperature is low, "m '" is increased to lower the frame frequency,
By changing "m '" so that "m'" is decreased and the frame frequency is increased at high temperature, the drop of the voltage substantially applied to the dots can be reduced and the contrast ratio can be improved. Since the relationship between the frame frequency and the temperature is obtained by an experiment, the data obtained by the experiment is stored in the RAM (not shown) of the microcomputer 2 and the CPU 21 displays the signal a from the temperature sensor 1 on the liquid crystal panel 3. The frame frequency can be automatically adjusted by selecting the optimum "m '", and a liquid crystal display device with good contrast can be obtained in a wide temperature range. The microcomputer 2 changes the frame frequency. It becomes the control means to make.

Needless to say, the present invention can be applied in various ways within the scope of the invention.

[0015]

According to the present invention, in a liquid crystal display device having a simple matrix type liquid crystal panel and a drive circuit for driving the liquid crystal panel by the voltage averaging method, the circuit constant of the drive circuit is changed according to the temperature. It is equipped with a control means consisting of a microcomputer that changes the frame frequency without changing the frame frequency.By setting the microcomputer program, the frame frequency can be automatically adjusted and the contrast in a wide temperature range is good. The conventional problems such as selecting a thermistor having the characteristic of obtaining a frame frequency that optimizes the display and providing a dedicated circuit for adjusting the frame frequency, which has the effect of obtaining a liquid crystal display device. The point can be solved.

Further, a liquid crystal panel having different temperature characteristics can be dealt with by changing the program of the microcomputer, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a display data structure of the embodiment.

[Explanation of symbols]

 1 temperature sensor 2 microcomputer (control means) 3 liquid crystal panel 4 segment driver (driving circuit) 5 common driver (driving circuit)

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[Procedure amendment]

[Submission date] October 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Generally, a liquid crystal display device , for example, has a high temperature because its response speed changes depending on the ambient temperature.
Then, the so-called frame response phenomenon causes a contrast ratio.
It becomes difficult to see as the
Large change and good display in wide temperature range
Was difficult. Here, the frame response phenomenon is
In case of positive display, it is necessary to display opaque at the display area.
The transmittance at the ON point where a voltage is applied becomes high and the negative display
In the case of, the voltage for transmissive display is applied at the display area.
The transmittance of the ON point is reduced, and in any of these cases
The transmittance ratio calculated by the ratio with the off point decreases, and this transmission
Meaning that the contrast ratio determined by the ratio decreases
There is.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The liquid crystal panel 3 has a slow response speed when the temperature is low and a fast response speed when the temperature is high.
When the response speed is high, the contrast ratio is low and the display is difficult to see. To compensate for this, when the temperature is low, "m '" is increased to lower the frame frequency,
By changing "m '" so that "m'" is decreased and the frame frequency is increased at high temperature, Iwayu
It is possible to suppress the frame response phenomenon that occurs and improve the contrast ratio. Since the relationship between the frame frequency and the temperature is obtained by the experiment, the data obtained by the experiment is stored in the ROM (not shown) of the microcomputer 2, and the CPU 21 displays the signal a from the temperature sensor 1 on the liquid crystal panel 3. The frame frequency can be automatically adjusted by selecting the optimum "m '", and a liquid crystal display device with good contrast can be obtained in a wide temperature range. The microcomputer 2 changes the frame frequency. It becomes the control means to make.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Sato 1-190-1, Fujihashi, Nagaoka City, Niigata Prefecture 1 R & D Center, Nippon Seiki Co., Ltd. (72) Inventor Masaharu Watanabe 2 Higashi Zao, Nagaoka City, Niigata Prefecture No. 2-34 Nippon Seiki Co., Ltd.

Claims (1)

[Claims] 1. A liquid crystal display device having a simple matrix type liquid crystal panel and a drive circuit for driving the liquid crystal panel by a voltage averaging method, without changing the circuit constant of the drive circuit according to temperature. A liquid crystal display device characterized by comprising a control means comprising a microcomputer for changing a frame frequency.