JPH1164826A - Temperature compensator for color liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately correct temperature/optimum output voltage data for each color liquid crystal display element corresponding to its dispersion or change with the passage of time. SOLUTION: Concerning a temperature compensator for color liquid crystal display element utilizing the retardation of liquid crystal and phase difference board, this device is provided with a temperature detection circuit 11, a data table 12 storing digital temperature/optimum output voltage data for reading optimum output voltage data corresponding to temperature data from a temperature detection circuit 11, a voltage correcting means 17 for correcting the optimum output voltage data read out of this data table 12, a D/A converting circuit 13 for D/A converting these optimum output voltage data and sending them to the driving circuit of the liquid crystal display element, a manipulating part 16 for applying the correction data to the voltage correcting means 17, and a control means 14 for correcting the temperature/optimum output voltage data in the data table 12 based on the correction data from this manipulating part 16 and the temperature data from the temperature detection circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensator for a color liquid crystal display device, and more particularly, to a temperature compensator applied to a color liquid crystal display device using retardation.

[0002]

2. Description of the Related Art First, the structure of a color liquid crystal display device using retardation will be schematically described with reference to FIG. In this color liquid crystal display device, the liquid crystal panel 1
Has two transparent substrates 1B, 1B each having a transparent electrode and an alignment film formed on the transparent electrode, and bonded in parallel with each other via a sealing material 1A.

A nematic liquid crystal 1C containing a rotatory substance and having a positive dielectric anisotropy is sealed in a cell between the transparent substrates 1B, 1B. In this case, the twist angle of the liquid crystal molecules is determined by the alignment film. 160-300 degrees. The product (Δn1 × d1) of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer is, for example, 1.2 at 25 ° C.
２．５2.5 μm.

On both surfaces of the liquid crystal panel 1, polarizing plates 2 and 3 are disposed, respectively, and a phase difference plate 4 is disposed between the front polarizing plate 2 and the liquid crystal panel 1. Further, a reflection plate 5 is arranged on the lower surface of the rear polarizing plate 3.

In this color liquid crystal display element, a color display is realized by controlling the voltage applied to the transparent electrode to change the retardation of the liquid crystal.
Therefore, it is possible to provide an inexpensive and bright color display without requiring a color filter, and to provide a low power consumption type color liquid crystal display element which does not require a backlight.

As described above, in this method, colorization is realized by using the retardation of the liquid crystal and the phase difference plate. In general, however, the retardation value of the liquid crystal (Δn1 × d
1) changes with temperature and shows a tendency that the retardation value decreases as the temperature increases. For this reason, even when a clear hue is exhibited near room temperature, the matching of the retardation between the liquid crystal and the retardation plate becomes poor at low and high temperatures, and a vivid color cannot be obtained.

Therefore, conventionally, a temperature compensator for changing the voltage applied to the transparent electrode according to the ambient temperature is provided to optimize the hue. An example will be described with reference to FIG. 5. This temperature compensating device includes a temperature detecting circuit 11 having a temperature sensing element 11 a such as a thermistor, a data table 12 for temperature versus optimum output voltage data, and an output from the data table 12. A D / A conversion circuit 13 converts the optimum output voltage data to an analog signal, and a CPU (Central Processing Unit) 14 as control means.

The optimum output voltage data for temperature is, for example, -2.
This is representative optimum output voltage data at each temperature in the range of 0 ° C. to + 60 ° C., and is stored in the storage medium 15 such as a ROM in advance.

When power is applied to the liquid crystal display element, CP
U14 reads the temperature versus optimum output voltage data from the ROM 15 and writes the data to the data table 12. The current temperature is detected by the temperature detection circuit 11, and the detection signal is provided to the data table 12. Thereby, the optimum output voltage data corresponding to the current temperature is read from the data table 12. This optimum output voltage data is D /
After being converted into an analog signal by the A conversion circuit 13, the signal is output to a drive circuit of a liquid crystal display element for applying a drive voltage between the transparent electrodes.

[0010]

In this manner, the color temperature compensation with respect to the ambient temperature is performed. However, since the temperature vs. optimum output voltage data is representative (average value) data, the liquid crystal display element is required. If the temperature characteristics change due to variations in the temperature or changes over time, the accuracy of temperature compensation will be significantly impaired.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an optimum output voltage data with respect to temperature in accordance with the variation and aging of each color liquid crystal display element. It is an object of the present invention to provide a temperature compensation device for a liquid crystal display element which can be appropriately corrected.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a transparent electrode and an alignment film formed on the transparent electrode, each of which is disposed substantially in parallel with each other.
A nematic liquid crystal containing an optical rotatory substance and having a positive dielectric anisotropy is sandwiched between two transparent substrates, and the twist angle of the liquid crystal according to the alignment direction of the liquid crystal molecules formed by the alignment film of each transparent substrate is 160 to 300. And the product of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer (Δn1 ×
d1) is a predetermined value, and at least one polarizing plate and one retardation plate are provided outside the liquid crystal layer, and a driving circuit for applying a driving voltage between the transparent electrodes is provided. A temperature compensating device for a color liquid crystal display element utilizing the retardation of a liquid crystal and the retardation plate, wherein a temperature detecting circuit including a temperature sensor, digital temperature vs. optimum output voltage data are stored, and the temperature detecting circuit is used. A data table from which the optimum output voltage data corresponding to the temperature data is read, a voltage correction means for correcting the optimum output voltage data read from the data table, and an analog output voltage data from the voltage correction means. A D / A conversion circuit that converts the signal into a signal and sends the signal to the drive circuit; Based on the temperature data from the correction data and the temperature sensing circuit from the work unit is characterized by comprising a control means for modifying the temperature versus optimum output voltage data in the data table.

In this case, it is preferable that the operation unit is an up-down counter and the voltage correction means is a correction counter, so that the color matching adjustment operation can be easily performed only by operating the push buttons. Can be.

In addition to the data table, a save memory in which the temperature vs. optimum output voltage data is written is provided. When the temperature vs. optimum output voltage data is corrected, the corrected data is written in the save memory, and thereafter, the corrected data is written to the save memory. Temperature correction based on the correction data is performed.

According to the present invention, the optimum output voltage data is changed by the voltage correction means by providing the color correction signal from the operation unit. Therefore, the user can appropriately correct the display color so as to obtain the optimum or desired color while watching the color display on the liquid crystal panel.

On the control means side, when a correction end signal is input from the operation unit, for example, all the temperatures are calculated based on a predetermined arithmetic expression from the current temperature from the temperature detection circuit and the corrected output voltage data. The temperature vs. optimum output voltage data in the data table is rewritten over the range, and the rewritten temperature vs. optimum output voltage data is stored in the save memory. Thereafter, the new temperature versus optimum output voltage data is used. Note that the saving in the save memory may be performed by overwriting the corrected data with the old data, or may be written in an area different from the old data.

[0017]

Next, an embodiment of a temperature compensating device according to the present invention will be described with reference to the drawings. In this embodiment, the color liquid crystal display element to be subjected to the temperature compensation is the color liquid crystal display element using the retardation of the liquid crystal and the phase difference plate described above with reference to FIG.

As shown in FIG. 1, this temperature compensating device has, as its basic components, a temperature detecting circuit 11 including a temperature sensing element 11a, similarly to the conventional device of FIG. And a data table 12 for temperature versus optimum output voltage data, a D / A conversion circuit 13, and a CPU 14 as control means. In addition to this, the optimum output voltage data output from the data table 12 is provided. And an operation unit 16 and a voltage correction unit 17 for correcting the error. Also, for example, a rewritable RAM (Random Access Mem) as a data saving memory.
ory) 15a.

In this embodiment, the operation section 16 has a function of an up / down counter, 16a is a count up key, and 16b is a count down key.
In this embodiment, the temperature vs. optimum output voltage data set in the data table 12 has an 8-bit configuration. Therefore, the voltage correction means 17 transmits the 8-bit data based on the count value from the operation unit 16. A correction counter for correcting data is used. This voltage correction means 17
Is connected between the data table 12 and the D / A conversion circuit 13.

The CPU 14 receives a temperature signal from the temperature detection circuit 11 and a corrected voltage signal from the operation unit 16, and the RAM 15a has a typical (average) signal as in the conventional device. (Value-wise) temperature-optimum output voltage data is written in advance.

When the power of the color liquid crystal display element is turned on, the CPU 14 reads out typical temperature vs. optimum output voltage data from the RAM 15a and sets the data in the data table 12. The current temperature is detected by the temperature detection circuit 11, and the detection signal is provided to the data table 12.

As a result, the optimum output voltage data corresponding to the current temperature is read out from the data table 12. When the color correction is not required, the optimum output voltage data is stored in the D / A conversion circuit 13 as in the conventional device. Is converted into an analog signal, and is applied as a drive voltage between transparent electrodes (not shown).

On the other hand, when a color correction request signal is issued from the operation unit 16, a guidance screen as shown in FIG. 2 is displayed on the liquid crystal panel 1 (see FIG. 4). In this embodiment, the current temperature is displayed as “〇〇 ° C.” on the guidance screen, and the count-up key 16a and the count-down key are displayed so that the white, red, blue, and green colors on the screen are clearly displayed. The user is instructed to operate the key 16b and confirm with the "execute key".

In this embodiment, adjustments are made in this embodiment so that "blue" is clearly produced. That is, “white”, “red”, and “green” are linked to the “blue” voltage by a predetermined gradation method and gradation ratio,
The reason for matching with “blue” is that the voltage at which the transmittance is minimum matches the voltage of the bluest blue.

When the key operation of count-up or count-down is performed in response, the data table 1
2 is corrected by the voltage correction means (correction counter) 17 to higher or lower voltage data, and the transparent data of the liquid crystal panel 1 is transmitted through the D / A conversion circuit 13. Applied between the electrodes.

When the "execute key" (not shown) of the operation unit 16 is pressed to confirm the color correction, the CPU 1
Reference numeral 4 denotes a temperature vs. optimum output voltage data in the entire temperature range (for example, -25 ° C. to + 60 ° C.) based on the current temperature signal from the temperature detection circuit 11 and the corrected (corrected) output voltage data according to a predetermined arithmetic expression. ° C), and the new temperature versus optimum output voltage data is reset in the data table 12 and stored in the saving RAM 15a.

That is, in the graph of temperature versus optimum output voltage data shown in FIG. 3, if the solid line curve in FIG. 3 is the initially set optimum output voltage data, the optimum output voltage data will The output voltage is changed so as to have any one of the dashed lines, and thereafter, the optimal output voltage data corrected this time is used until the color correction is performed again. Note that FIG. 3 shows three chain-line curves as corrected curves, but these are merely examples.

Note that, unlike the above embodiment, the operation unit 16
Even when the manual adjustment is performed, if the current temperature is within a specific temperature range, the threshold voltage of the liquid crystal panel 1 needs to be corrected, and if the current temperature is outside the specific temperature range, the optimum output voltage data can be adjusted. May be rewritten based on a predetermined arithmetic expression. Next, another embodiment will be described.

First, the RAM 15a stores -20 to +60.
It is assumed that typical (average) temperature-optimum output voltage data D (−20) to D (60) are written before shipment at 1 ° C. intervals. The CPU 14 has a register for adjusting the variation of the threshold voltage for each liquid crystal panel. It is assumed that the threshold voltage adjustment data d is written in this register in advance at the time of shipment.

In this alternative embodiment, if the temperature at the time of adjustment is in the range of, for example, +15 to + 35 ° C., only the threshold voltage adjustment data d is corrected based on the adjustment data from the operation unit 16. , The data in the RAM 15a is not rewritten.

That is, when the temperature falls within this temperature range, the threshold voltage adjustment data d is uniformly added or subtracted from the temperature vs. optimum output voltage data output from the data table 12, and the data in the RAM 15a is rewritten. Do not do.

On the other hand, when the temperature at the time of adjustment is, for example, +3
When the temperature is within the range of 6 to + 60 ° C., the correction data D (36) to D (6) of +36 to + 60 ° C. in the RAM 15a is based on the data D (T) at + 25 ° C.
0) is rewritten as D (T) ′ obtained by the following equation (1).

[0033]

(Equation 1)

The temperature at the time of adjustment is, for example, -20 to +1.
When the temperature is within the range up to 4 ° C., −20 to 20 ° C.
The correction data D (−20) to D (14) up to + 14 ° C. is rewritten to D (T) ′ obtained by the following equation (2).

[0035]

(Equation 2)

In each of the above embodiments, the save memory 1
Although a RAM is used as 5a, another recording medium such as a floppy disk or a memory card may be used. In the above embodiment, the optimum output voltage data for temperature is set in the data table 12, and the optimum output voltage data corresponding to the temperature signal is selected from the data.
A calculation formula of the temperature versus the optimum output voltage data may be programmed in U14, and the CPU 14 may calculate the optimum output voltage data corresponding to the temperature every time the temperature signal changes.

[0037]

As described above, according to the present invention,
In a color liquid crystal display device using retardation, a user can appropriately correct variations in temperature versus color characteristics that cannot be individually adjusted at the time of shipment from a manufacturer.

Similarly, it is possible for the user to appropriately correct the temporal change of the temperature versus color characteristics. For this reason, adjustment at the time of shipment from the manufacturer can be omitted in some cases. Furthermore, since the accuracy is improved, the number of circuits and memories can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a temperature compensation device according to the present invention.

FIG. 2 is a diagram of a guide screen displayed on a liquid crystal panel when performing color correction in the embodiment.

FIG. 3 is a graph of temperature versus optimal output voltage data.

FIG. 4 is a schematic cross-sectional view for explaining a configuration of a color liquid crystal display element using retardation.

FIG. 5 is a block diagram showing a conventional temperature compensation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Temperature detection circuit 12 Data table 13 D / A conversion circuit 14 CPU 15a Saving memory 16 Operation part 17 Voltage correction means

Claims (3)

[Claims] 1. A semiconductor device comprising: a transparent electrode; and an alignment film formed on the transparent electrode.
A nematic liquid crystal containing an optical rotatory substance and having a positive dielectric anisotropy is sandwiched between two transparent substrates, and the twist angle of the liquid crystal according to the alignment direction of the liquid crystal molecules formed by the alignment film of each transparent substrate is 160 to 300. And the product of the refractive index anisotropy (Δn1) of the liquid crystal layer and the thickness (d1) of the liquid crystal layer (Δn1 ×
d1) is a predetermined value, and at least one polarizing plate and one retardation plate are provided outside the liquid crystal layer, and a driving circuit for applying a driving voltage between the transparent electrodes is provided. A temperature compensating device for a color liquid crystal display element utilizing the retardation of a liquid crystal and the retardation plate, wherein a temperature detecting circuit including a temperature sensor, digital temperature vs. optimum output voltage data are stored, and the temperature detecting circuit is used. A data table from which the optimum output voltage data corresponding to the temperature data is read, a voltage correction means for correcting the optimum output voltage data read from the data table, and an analog output voltage data from the voltage correction means. A D / A conversion circuit that converts the signal into a signal and sends the signal to the drive circuit; Control means for correcting the temperature versus the optimum output voltage data in the data table based on the correction data from the working unit and the temperature data from the temperature detection circuit. Compensator. 2. A temperature compensating device for a color liquid crystal display device according to claim 1, wherein said operation section comprises an up / down counter, and said voltage compensating means comprises a compensation counter. 3. A save memory in which the temperature vs. optimum output voltage data is written separately from the data table, wherein the control means, when correcting the temperature vs. optimum output voltage data, stores the corrected data in the save memory. 2. A temperature compensating device for a color liquid crystal display element according to claim 1, wherein the temperature is written in the device.