JPH05297350A - Temperature compensating device for liquid crystal optical element - Google Patents

Abstract

PURPOSE:To facilitate the use in practical environment by improving the large temperature dependency of the liquid crystal element using a ferroelectric macromolecular liquid crystal material which facilitates an increase in the area of a screen. CONSTITUTION:The temperature of the display part of a liquid crystal panel 12 is detected by a temperature sensor 22. A temperature compensation control circuit 40 in a temperature detection part 20 controls a clock signal generation part 36 or driving reference voltage source 38 according to the detected temperature to supply a driving signal which has pulse width and/or a voltage for holding variation in the display contrast ratio of the liquid crystal panel 12 within 20% to the liquid crystal panel 12 through a signal electrode driver 14 and a scanning electrode driver 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating device for a liquid crystal optical element for compensating the temperature of a display image contrast ratio of a liquid crystal display element used in an electronic device display device or the like.

[0002]

2. Description of the Related Art In recent years, a liquid crystal element using a ferroelectric low molecular weight liquid crystal material has a memory function and has an extremely high electric field response, so that versatile research utilizing this characteristic has been conducted. .. The liquid crystal element having such a function is
Since it is necessary to form an extremely thin cell and it is difficult to control the alignment, it is difficult to manufacture a large-area liquid crystal element. On the other hand, the ferroelectric polymer liquid crystal material has a film-forming property,
There is an advantage that a liquid crystal element having a large area can be easily produced by combining it with a flexible substrate such as a plastic substrate which has excellent orientation.

[0003]

However, the ferroelectric polymer liquid crystal material has a large temperature dependence of various characteristics such as response time, and it is difficult to use it in a practical environment under a single driving condition. , This improvement is a challenge.

As an example of improving this problem, there is a "liquid crystal device" disclosed in JP-A-63-306426. In the "liquid crystal device" of Japanese Patent Laid-Open No. 63-306426, a dot matrix type ferroelectric liquid crystal element is driven by superimposing a DC voltage on an AC voltage applied to a pixel portion. Then, the DC voltage value is changed in accordance with the temperature change, and the temperature is compensated.
By the way, in the "liquid crystal device" in Japanese Patent Laid-Open No. 63-306426, the DC voltage component must be greatly increased / decreased when the temperature compensation is performed, especially when a liquid crystal element having a large temperature dependency is used. Therefore, the liquid crystal material may be deteriorated or decomposed when it is used for a long time.

The present invention has been made in view of the above problems, and improves a large temperature dependency in a liquid crystal element using a ferroelectric polymer liquid crystal material which can easily increase the area of a screen. An object of the present invention is to provide a temperature compensating device for a liquid crystal optical element, which can be easily used in a practical environment.

[0006]

In order to achieve the above object, a temperature compensating device for a liquid crystal optical element of the present invention contains a ferroelectric polymer liquid crystal material, and has an electrical and optical response time of 1 or less.
In a temperature compensating device for a liquid crystal optical element, the temperature of a display section of the liquid crystal optical element is detected in a temperature compensating device for a liquid crystal optical element in which a liquid crystal composition that is sandwiched between substrates with electrodes has a liquid crystal composition that changes more than twice with respect to a temperature change of 0 ° C. Temperature detecting means, and drive signal generating means for supplying to the liquid crystal optical element a drive signal having a pulse width and / or a voltage for keeping the change of the display image contrast ratio in the liquid crystal optical element within 20% according to the detected temperature. Is provided.

A preferred embodiment of the temperature compensating device for a liquid crystal optical element of the present invention will be described below with reference to the drawings. The liquid crystal element is configured by sandwiching a liquid crystal composition containing a ferroelectric polymer liquid crystal material having excellent orientation and film-forming properties between substrates with electrodes. In particular, when combined with a flexible plastic substrate or the like, a series of continuous manufacturing methods such as film forming, laminating and orientation by bending can be used, and productivity is remarkably improved.
In addition, it is possible to easily manufacture a display liquid crystal element having an extremely large area in meters (m). Ferroelectric polymer liquid crystal materials have large temperature dependence of various characteristics such as response time, and under a single driving condition, display quality beyond a certain level may not be obtained even under a normal environment. In general, a liquid crystal composition containing a ferroelectric polymer liquid crystal material has an electrical and optical response time which changes about 2 to 10 times with respect to a temperature change of 10 ° C. It is difficult to obtain the desired display quality with temperature compensation to the extent that it is performed.

Next, a liquid crystal optical element temperature compensating device for effectively performing such temperature compensation will be described.
FIG. 1 shows a configuration example of a temperature compensating device for a liquid crystal optical element. In FIG. 1, this example is a display unit 10 having a liquid crystal panel, a temperature detection unit 20 for detecting the temperature of the liquid crystal panel in the display unit 10, and a drive signal generation unit 30 for generating and transmitting a predetermined drive waveform. It is roughly composed of and. The display unit 10 includes a liquid crystal panel 12, a well-known signal electrode driver 14 and a scan electrode driver 16. The temperature detection unit 20 is arranged in contact with or in the vicinity of the liquid crystal panel 12 of the display unit 10 to detect the temperature sensor 22 for detecting the temperature of the liquid crystal panel 12 and the contrast ratio of the display image on the liquid crystal panel 12. Contrast monitor 2
4 and.

The temperature sensor 22 can use a conventional temperature detecting element, for example, a thermistor, a thermocouple or the like. In addition to such a direct temperature measuring element, a device that electrically or optically measures the response time of the pixel portion of the display unit or the non-image display unit, or the temperature change of the dielectric property of the liquid crystal material is electrically performed. A detection device may be used. The drive signal generation unit 30 determines a display data storage unit 32 for storing display image data, an output pulse width, and a drive signal determination unit based on the stored data from the display data storage unit 32. And a controller 34. Further, the drive signal generation unit 30 supplies the clock signal generation unit 36 that changes the frequency, that is, the pulse width by control, and outputs the clock signal, the signal electrode driver 14 of the liquid crystal panel 12, and the scan electrode driver 16. Drive reference voltage source 3 for outputting a voltage which is a drive signal for
8 and a control signal based on the detection signal from the temperature detection unit 20 and a clock signal generation unit 36 and a driving reference voltage source 38.
And a temperature compensation control circuit 40 for outputting
The temperature compensation control circuit 40 stores in advance a pulse width and / or voltage in which the change of the contrast ratio is within 20% for each temperature in a memory (not shown) and reads the stored data, that is, a so-called lookup table (conversion table).
Is stored.

Next, the operation and function of this device will be described. Drive signals are supplied to the signal electrodes and the scanning electrodes of the liquid crystal panel 12 from the signal electrode driver 14 and the scanning electrode driver 16, respectively. This drive signal changes according to the control signal from the drive controller 34.
The drive controller 34 determines the pulse width according to the clock signal from the clock signal generator 36, and also determines the content of the display image based on the stored data from the display data storage 32. The drive voltage of the liquid crystal panel 12 is supplied from the drive reference voltage source 38 to the signal electrode driver 14 and the scan electrode driver 16. The temperature sensor 22 detects the temperature of the liquid crystal panel 12 and sends a detection signal, which is the temperature information, to the temperature compensation control circuit 40. The temperature compensation control circuit 40 outputs a control signal, which is compensation information based on the value of the detection signal, to the clock signal generation unit 36 and the driving reference voltage source 38.
Output to. In this case, the temperature compensation control circuit 40 reads out a pulse width and / or a voltage in which the change of the contrast ratio is 20% or less for each temperature in advance through the look-up table and outputs it.

Instead of the temperature detection by the temperature sensor 22,
The change in the contrast ratio of the liquid crystal panel 12 is detected, and the pulse width and /
Alternatively, the voltage can be controlled to a predetermined value. That is, with the contrast monitor 24 such as a photo sensor,
The pulse width and / or the voltage, which is a drive signal for which the change in the contrast ratio is within 20%, is measured from the drive controller 34 and the drive reference voltage source 38 to the signal electrode driver 14 and the scan electrode driver. 16, a clock signal generator 36 and a driving reference voltage source 38 through a temperature compensation control circuit 40.
Control.

As described above, the switching between the first stable state and the second stable state in the ferroelectric polymer liquid crystal material of the liquid crystal panel 12 is usually performed by, for example, a rectangular pulse in the time width of the pulse. This occurs when a pulse having a (pulse width) and a threshold value determined by the voltage is applied. Therefore, in the case of the matrix type panel, the scan electrode and the signal electrode are respectively applied so that a pulse of a threshold value or more is applied to the selected pixel among the pixels located at the fulcrum of the scan electrode and the signal electrode and a threshold value is applied to the other pixels. Multiplexing drive can be performed by applying a pulse suitable for.

As a suitable pulse to be applied to each of the scan electrode and the signal electrode, either the pulse width or the voltage, or both are changed. That is, the temperature detection unit 20 detects the temperature of the liquid crystal panel 12, and according to the temperature, the drive signal generated by the drive signal generation unit 30 is controlled so as to keep the change in the display contrast ratio within 20%. Signal electrode driver 14 and scan electrode driver 16
Supply through. In this case, the ferroelectric polymer liquid crystal material has a greater temperature dependency than the ferroelectric low-molecular liquid crystal material, and therefore both are preferably changed simultaneously to expand the temperature compensation range. By setting the change of the actual display contrast ratio within 20%, it is possible to perform temperature compensation which is practically acceptable. When the contrast ratio changes by 20% or more depending on the temperature, it is not preferable because it is visually recognized as a large change.

[0014]

According to the temperature compensating device for a liquid crystal optical element having the above-mentioned structure, a drive signal of a pulse width and / or a voltage for keeping the change of the display image contrast ratio in the liquid crystal optical element within 20% according to the detected temperature is generated. It is supplied to the liquid crystal optical element.

[0015]

EXAMPLES The temperature compensating apparatus for liquid crystal optical elements of the present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. Example 1

[0016]

[Chemical 1]

IT in which the above liquid crystal material is patterned in a stripe shape as a 25% by weight dichloromethane solution
A dot-matrix liquid crystal device was produced by coating a film on the electrode surface of a polyether sulfone (PES) substrate with an O electrode using a microgravure coater, and laminating it with a substrate of the same type to which nothing was coated after solvent evaporation. The liquid crystal element is a dot matrix type with a 5.08 mm pitch (electrode width 4.88 mm, gap 0.20 mm), and the number of scanning lines is 2.
The number was 4, and the number of signal boards was 72. The size of the liquid crystal element is about 150 mm × 400 mm. When the response time t _10-90 with respect to the measurement temperature (° C.) of the present liquid crystal element was measured, the results shown in Table 1 below were obtained. [Table 1] ────────────────────────────────── Measurement temperature (℃) 10 20 30 40 40 ─── ─────────────────────────────── Response time t _10-90 12ms 3.1ms 700μs 280μs ─────── ─────────────────────────── As shown in the results in Table 1, the temperature dependence is large. The response time t _10-90 is the time required for the amount of change in light transmittance to change from 10% to 90% when the liquid crystal element is arranged under crossed Nicols and a driving voltage of ± 10 V is applied. Defined as The alignment treatment was performed at room temperature by applying shearing due to bending deformation to the entire liquid crystal element while applying a DC voltage of 40V.

First, well-known 2 pulses at room temperature of 20 ° C., 1 /
It was driven by the 3-bias method. Figure 2 shows these two pulses,
Waveforms of voltage applied to the signal electrodes and scan electrodes in the 1/3 bias method driving are shown, and FIG. 3 shows an example of the waveform of the voltage applied to the pixel portion. The temperature compensating device for liquid crystal optical element shown in FIG. 1 was used as this device. When the applied voltage in the drive signal is 10 V, pulse width tp = 4
A good-quality display image was obtained in ms, and the contrast ratio was 11. Next, the temperature of the liquid crystal element (corresponding to the liquid crystal panel 12 in FIG. 1) is changed in the range of room temperature from 10 ° C. to 40 ° C., and the applied voltage V and the pulse width tp (ms) with respect to the liquid crystal element temperature (° C.). When the driving conditions for the contrast ratio were determined, the results shown in Table 2 below were obtained. [Table 2] ────────────────────────────────── Liquid crystal element temperature (℃) 10 20 30 40 ── ──────────────────────────────── Applied voltage V (V) 20 10 6 4 ───────── ────────────────────────── Pulse width tp (ms) 7 4 1.5 0.6 ─────────── ──────────────────────── Contrast ratio 9 11 10 10 10 ──────────────────── ──────────────

As can be seen from the results shown in Table 2, in the liquid crystal element exhibiting extremely large temperature dependence, it was possible to reduce the change in the display contrast ratio by changing the applied voltage V. Next, a thermocouple (Fig. 1
(Corresponding to the display data storage unit 32 in FIG. 1) in which the driving condition data shown in Table 2 is stored in advance by arranging the temperature sensor 22) and converting the voltage output according to the temperature into analog-digital. The driving conditions corresponding to the digital output were read out from (1) to drive the liquid crystal element. as a result,
When the liquid crystal element temperature was in the range of 10 ° C. to 40 ° C., the contrast ratio was in the range of 9 to 11, and a substantially constant and good quality display image was obtained.

[0020]

As described above, according to the temperature compensating device for a liquid crystal optical element of the present invention, the large temperature dependence of the liquid crystal element using the ferroelectric polymer liquid crystal material which facilitates the enlargement of the screen area is improved. And can be easily put into practical use.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of one example of a temperature compensating device for a liquid crystal optical element of the present invention.

FIG. 2 is a voltage waveform diagram applied to a signal electrode and a scan electrode in the 2-pulse, 1/3 bias method driving.

FIG. 3 is a voltage waveform diagram applied to a pixel portion of a liquid crystal element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Display part 12 ... Liquid crystal panel 14 ... Signal electrode driver 16 ... Scan electrode driver 20 ... Temperature detection part 22 ... Temperature sensor 24 ... Contrast monitor 30 ... Drive signal generation part 32 ... Display data storage part 34 ... Drive controller 36 ... Clock signal generator 38 ... Driving reference voltage source 40 ... Temperature compensation control circuit

Claims (1)

[Claims] 1. A liquid crystal optical element comprising a ferroelectric polymer liquid crystal material, and a liquid crystal composition having electrical and optical response times which change by a factor of 2 or more with respect to a temperature change of 10 ° C. is sandwiched between substrates with electrodes. In a temperature compensating device for a liquid crystal optical element for performing temperature compensation, a temperature detecting means for detecting a temperature of a display portion of the liquid crystal optical element, and a display image contrast in the liquid crystal optical element according to the temperature detected by the detecting means. A temperature compensating device for a liquid crystal optical element, comprising: a drive signal generating means for supplying a drive signal having a pulse width and / or a voltage for keeping the change of the ratio within 20% to the liquid crystal optical element.