JPH0381626A - Liquid crystal sheet thermometer - Google Patents

Abstract

PURPOSE:To find accurate temperature with good response by applying a rectangular or triangular voltage, measuring the response time when a dipole is inverted in ferroelectric phase from the peak of a polarization inverting current, and using data on the temperature and response time. CONSTITUTION:When a control means 41 commands a voltage applying means 20 to apply a voltage to a specific position of a sheet type temperature sensing means 10, an applying means 20 applies the rectangular wave, etc., to an electrode line corresponding to the specific position between electrodes 14 and 15 according to the command. When the rectangular wave voltage, etc., is applied from the applying means 20, the dipole of liquid crystal molecules of the liquid crystal cell at the part applied with the voltage is inverted as the polarity of the voltage is varied so that the polarization inverting current flows to the liquid crystal cell. A current variation measuring means 30 measures the current polarization inverting current and sends the result to the calculation part 42 of a processing part 40. The calculation part 42 finds the response speed tm or tw of the liquid crystal cell from the current variation sent from a varying means 30 and finds the temperature corresponding to the response speed tm or tw from the response-speed/temperature characteristic data of the ferroelectric high polymer liquid crystal which is stored previously in a data storage means 43.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal temperature sensor using ferroelectric polymer liquid crystal.

[Prior Art] Liquid crystals are widely used in color televisions, displays for various types of equipment, and are used in various devices in various fields. One of these is the use of liquid crystals as temperature-sensitive devices.

Conventionally, there are devices shown in Japanese Patent Application Laid-open Nos. 49-31386, 50-130483, and 50-28382, which have been used as liquid crystal temperature-sensitive devices.

Among these, Japanese Patent Application Laid-Open No. 49-31386 discloses a thermometer that mainly uses cholesteric liquid crystal and utilizes the change in color of its characteristic reflection with respect to temperature changes. Further, Japanese Patent Application Laid-Open No. 130483/1983 discloses a technique for measuring a planar (two-dimensional) temperature distribution by using a heat-sensitive liquid crystal (thermo-sensitive film).

Further, Japanese Patent Application Laid-Open No. 50-28382 discloses a technique in which a nematic liquid crystal is used and the temperature is measured using the low temperature operating limit as a temperature reference.

[Problems to be Solved] Among the above-mentioned conventional techniques, those described in Japanese Patent Application Laid-Open Nos. 49-31386 and 50-130483 all have the following problems:
This method attempts to measure temperature changes based on changes in color, and there is a problem in that accurate temperature measurements cannot be made without quantitative performance.

In addition, the method described in JP-A-50-28:182 uses properties other than color change of liquid crystal, so there is no problem in terms of accuracy, but since it uses nematic liquid crystal, It had poor responsiveness and could not be used as a large-area two-dimensional thermometer.

The present invention has been made in view of the above problems, and uses ferroelectric polymer liquid crystal.

The purpose of this invention is to provide a liquid crystal sheet thermometer that can quantitatively measure two-dimensional temperature distribution.

[Means for solving the problem] A temperature sensing means made of a ferroelectric polymer liquid crystal element, a voltage applying means for applying a voltage to the temperature sensing means, and a means for measuring changes in current flowing through the temperature sensing means upon application of the voltage. , and a temperature calculation means for determining the response speed of the liquid crystal (4') from this current change and calculating the temperature from this response speed, preferably, the ferroelectric polymer liquid crystal element of the temperature sensing means is arranged in a planar manner. It has a configuration in which the electrodes are arranged in a matrix.

[Function] According to a liquid crystal sheet thermometer with such a configuration, a rectangular wave or triangular wave voltage is applied, and the response time for reversal of the dipole (spontaneous polarization) in one ferroelectric phase is measured from the peak of the polarization reversal current. Furthermore, by using data on temperature and response time, it is possible to obtain accurate temperature with good responsiveness.

[Example] Hereinafter, an example of the liquid crystal sheet thermometer of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the overall configuration of the embodiment thermometer, and FIG. 2 is a partially enlarged sectional view of the temperature sensing means.

In FIG. 1, reference numeral 10 denotes a temperature sensing means, and the rear side of the ferroelectric polymer liquid crystal layer 11 is held between a substrate 12 having an electrode 14 and a substrate 13 having an electrode 15.

For the liquid crystal layer 11, a primary ferroelectric liquid crystal material containing polymer liquid crystal is used.

In addition, as the ferroelectric liquid crystal material, any material can be used as long as it takes a ferroelectric liquid crystal state, including polymer liquid crystal (liquid crystal polymer). Examples include mixtures of ferroelectric low-molecular liquid crystal compounds.

Examples of ferroelectric liquid crystal polymers include acrylate main chain liquid crystal polymers, methacrylate main chain liquid crystal polymers,
These include chloroacrylate main chain liquid crystal polymers, oxirane main chain liquid crystal polymers, siloxane main chain liquid crystal polymers, ester main chain liquid crystal polymers, and the like.

Examples of the repeating unit of the acrylate main chain liquid crystal polymer include (A), (B), and the like.

Examples of repeating units of the methacrylate main chain liquid crystal polymer include (C) (D) CI.

Examples include.

Examples of the repeating unit of the chloroacrylate main chain liquid crystal polymer include (E) (J').

Examples of the repeating unit of the oxirane main chain liquid crystal polymer include (F).

Examples of the repeating unit of the siloxane main chain liquid crystal polymer include (G) Cu2.

The repeating unit of the ester main chain liquid crystal polymer is as follows: for example, (H) (I) (J) Examples include.

Note that the side chain skeletons in the repeating units of the above-mentioned ferroelectric liquid crystal polymer may be replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, or a phenyl 4-phenylbenzoate skeleton, respectively. The benzene ring inside is a pyrimidine ring,
Pyridine ring, pyridazine ring, pyrazine ring, tetrazine ring.

May be substituted with a cyclohexane ring, dioxane ring, dioxaborinane ring, may be substituted with a halogen group such as fluorine or chlorine, or a cyano group, l-methylalkyl group, 2-fluoroalkyl group, 2-chloroalkyl group, 2-chloro-3-methylalkyl group, 2-trifluoromethylalkyl group, 1-alkoxycarbonylthyl group, 2-alkoxy-1-methylethyl group, 2-alkoxypropyl group, 2-chloro-1-methylalkyl group , 2-alkoxycarbonyl-1-trifluoromethylpropyl group, etc., or these optically active groups may be substituted via an ester bond or an ether bond.1 The length of the spacer is determined by the methylene chain length. 1~
It may vary within a range of 30.

Further, the above ferroelectric liquid crystal polymer has a number average molecular weight of 1,
000 to 200.000 can be used.

Examples of ferroelectric low-molecular liquid crystal compounds include Schiff base-based ferroelectric low-molecular liquid crystal compounds, azo and azoxy-based ferroelectric low-molecular liquid crystal compounds, biphenyl and aromatics ester-based ferroelectric low-molecular liquid crystal compounds, and halogen-based ferroelectric low-molecular liquid crystal compounds. , a ferroelectric low-molecular liquid crystal compound into which a ring substituent such as a cyano group has been introduced, a ferroelectric low-molecular liquid crystal compound having a heterocycle, and the like.

Examples of the ship base-based dielectric low-molecular liquid crystal compound include the following compounds (1) to (4).

(1) nlI5~10,12.14 (2) n=7 to 10.11 (3> n=7.8.14 (4) nm4,8.12 As an azo and azoxy-based ferroelectric low-molecular liquid crystal compound is 1
Examples include (5) and (6) shown below.

(5) (6) n snow 16 Examples of biphenyl and aromatics ester-based ferroelectric low-molecular liquid crystal compounds include the following compounds (7
) and (8).

(7) (8) n=8 Examples of ferroelectric low-molecular liquid crystal compounds into which ring substituents such as halogen and cyano groups are introduced include the following compounds (9
) to (11).

(9) n-5,8,10 (10) r+118 (l 1) n=4.5 Examples of ferroelectric low-molecular liquid crystal compounds having a heterocycle include the following compounds (12), (13), Can be mentioned.

(12> (13) n=6.8.11 The above compound is a typical compound of 1 ferroelectric low molecular liquid crystal compound, and the ferroelectric low molecular liquid crystal compound of the present invention,
The product is not limited to these 4Ii structures in any way.

These ferroelectric liquid crystal materials may be used alone or in combination of two or more. If necessary, other polymers such as thermoplastic resins such as halogenated vinyl polymers, unsaturated alcohol or ether polymers, unsaturated carboxylic acid polymers, and crosslinkable resins such as epoxy resins and unsaturated polyesters may also be used. may be added, and furthermore, epoxy adhesive, acrylic adhesive, etc. may be added as an adhesive,
In addition, plasticizers, dyes, etc. may be added.

The thickness of the liquid crystal layer 11 is about 1 to 100 JL11, preferably about 2 to 20 JL11. If the liquid crystal layer 11 is made too thick, a high voltage must be applied, resulting in a lack of practicality.

Base type As the substrates 12 and 13 in the present invention, various kinds of known ones can be used.

Specifically, for example, ordinary glass, Vycor glass, quartz or special glass such as quartz glass, calcium fluoride, sodium chloride, potassium bromide,
Examples include various ceramic substrates such as alumina, inorganic substrates such as metals, organic substrates such as various plastics, rubber, and paper, and composite material substrates.

Among these, plastics such as thermoplastic resins or glass are preferred from the viewpoint of economy, versatility, processability, etc., as they have particularly excellent flexibility and are extremely easy to expand into large areas.
Flexible plastics such as flexible thermoplastic resins are particularly preferred since continuous production is particularly easy.

As the thermoplastic resin, various kinds can be used, among others, for example, polyethylene terephthalate (PET), polyether sulfone (PES), etc.
Materials with excellent flexibility, strength, heat resistance, durability, etc., such as polycarbonate (PC), can be suitably used.

The thickness of the substrates 12 and 13 is about log to several square meters.

The average 3 electrodes 14 and 15 are located on the inside of each substrate 12 and 13,
That is, they are provided so as to be located between the liquid crystal layer 11 and each of the substrates 12 and 13, respectively. The material for these electrodes 14 and 15 is metal such as AI, Au, Ag, etc. 1 [Use a film (or vapor deposited film), conductive oxide film, conductive organic film, etc. These electrodes 14,15 do not necessarily have to be transparent electrodes.

Further, in order to make the temperature sensing means 10 planar and to know the temperature at any position within the plane, electrodes 14 and 15 provided on both sides of the liquid crystal layer ti are connected to a large number of electrode wires as shown in FIG. These electrodes 14.15 are arranged in a matrix pattern so as to sandwich the liquid crystal fill.

In FIG. 1, reference numeral 20 denotes a voltage applying means, which periodically applies a voltage such as a rectangular wave or a triangular wave to any electrode line of the striped electrodes 14, 15.

30 is a current change measuring means, and the electrode 1 of the temperature sensing means lO
4. Measure the change in the current flowing through the liquid crystal layer 11 when a voltage is applied to 15. In other words, when an external electric field such as a rectangular wave or triangular wave whose polarity is periodically reversed is applied to a liquid crystal cell, the dipoles (spontaneous polarization) of the liquid crystal molecules are reversed in response to this combined electric field, causing the liquid crystal cell to undergo polarization reversal. Because current flows
Measure this.

For example, when a rectangular wave voltage as shown in FIG. 4(a) is applied to a liquid crystal cell, a polarization inversion current as shown in FIG. 4(b) flows. Measure change.

40 is a processing section, which includes a voltage application control means 41, a temperature calculation means 42, a data storage means 43, and an output.

Among these, the voltage application control means 41 determines which voltage is to be applied to which electrode wire of the electrodes 14 and 15,
The voltage application means 20 is controlled.

From the current change measured by the current change measuring means 30, the temperature calculating means 42 calculates the time t from electric field reversal to the peak or the half width of the peak tw, which represents the response speed of the liquid crystal cell.
(see Figure 4(b)).

As shown in FIG. 4-(c), the data storage means 43 determines the relationship between response speed and temperature in advance and stores this relationship as characteristic data. Note that the peak of the polarization reversal current appears only in the ferroelectric phase of the liquid crystal, so that it can be used only in the temperature range of the ferroelectric phase.

Reference numeral 44 denotes a display or output means such as a display or a printer for displaying or outputting various data in the processing section 40.

According to the liquid crystal sheet thermometer having such a configuration, it is possible to easily obtain a large-area sheet thermometer.

Next, a case will be described in which the temperature of a certain place is measured using the liquid crystal sheet thermometer of the above embodiment.

When the control means 41 instructs the voltage application means 20 to apply a voltage to a specific position of the sheet-shaped temperature sensing means 10, the voltage application means 20 responds to this command by ? l
A rectangular wave or the like (FIG. 4(a)) is applied to the electrode wires corresponding to specific positions of the t-poles 14 and 15.

When a voltage such as a rectangular wave is applied from the voltage applying means 20-, the dipoles of liquid crystal molecules in the liquid crystal cell in the part where the voltage is applied are reversed as the voltage polarity changes, causing polarization inversion in the liquid crystal cell. A current flows (FIG. 4(b)), and the current change measuring means 30 measures the polarization inversion current at this time and sends it to the calculation section 42 of the processing section 40.

The calculation unit 42 calculates the response speed tm or tw of the liquid crystal cell based on the current change sent from the current change means 30, and calculates the response speed of the ferroelectric polymer liquid crystal minus the temperature stored in the data storage means 43 in advance. The temperature corresponding to the response speed tm or tw is determined from the characteristic data.

As mentioned above, since the striped electrodes 14 and 15 are arranged in a matrix to sandwich the liquid crystal layer, by sequentially selecting segments on a plane, a planar (two-dimensional) temperature distribution can be obtained. You can know.

The temperature data thus obtained and other various data are displayed on the display 44. Otherwise, it is output by the printer 44.

This liquid crystal sheet thermometer is used to measure phase separation of the surface temperature of heating elements such as televisions, and temperature distribution on walls of special rooms. Furthermore, in the case of a flexible substrate, it is also possible to measure the temperature distribution on a curved surface portion.

According to this liquid crystal sheet thermometer, temperature measurement in the range of -20 to 150°C is possible by changing the type of liquid crystal used.

[Effects of the Invention] As described above, according to the liquid crystal sheet thermometer of the present invention, two-dimensional temperature measurement can be performed accurately and with good responsiveness.

[Brief explanation of drawings]

Fig. 1 is a block configuration diagram of an embodiment of the liquid crystal sheet thermometer of the present invention, Fig. 2 is a partially enlarged sectional view of the temperature sensing means, Fig. 3 is an explanatory diagram of the arrangement of electrodes, and Fig. 4 (a). is the applied voltage waveform diagram, Figure 4(b) is the polarization inversion current waveform diagram, and Figure 4(c) is the waveform diagram of the polarization inversion current.
is a characteristic diagram showing the relationship between response speed and temperature. 10: Temperature sensing means ll: Liquid crystal layer 12゜13: Substrate 14゜15, electrode 20: Voltage application means 30: Current change measuring means 40: Processing section 42: Calculation means

Claims (2)

[Claims] (1) a temperature sensing means made of a ferroelectric polymer liquid crystal element, a voltage application means for applying a voltage to the temperature sensing means, and a means for measuring changes in current flowing through the temperature sensing means by applying the voltage;
A liquid crystal sheet thermometer characterized by comprising temperature calculation means for determining the response speed of the liquid crystal from this current change and calculating the temperature from this response speed. (2) The liquid crystal sheet thermometer according to claim 1, characterized in that the ferroelectric polymer liquid crystal element of the temperature sensing means is formed in a planar manner, and the electrodes are arranged in a matrix.