JPS61197671A - Image recording method - Google Patents

Abstract

PURPOSE:To enable image recording to be conducted by widening a temperature range within which the memory state of image can be kept, by using a liquid crystal contg. a 4'-alkyl-4-fluorobiphenyl and recording image information by conducting specified means in order. CONSTITUTION:A liquid crystal element formed by putting the following liquid crystal having a thermooptical effect between upper and lower substrates, a means for externally heating said liquid crystal element, a means for applying an electrical field to said element and a means for locally heating said element, are used. Said element is passed through these means in order, whereby the recording of image information is conducted. Said liquid crystal contains a 4'-alkyl-4-fluorobiphenyl of the formula (wherein R is a 1-10C alkyl) such as 4'-pentyl-4-fluorobiphenyl or 4'-propyl-4-fluorobiphenyl.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording method, and particularly to a simple image recording method using a rewritable medium. ' In recent years, there has been an increase in demand for the use of rewritable media for image recording, but there have been some practical problems with conventional technology. However, with display devices such as CRTs, it is difficult to display high-definition images such as a single sentence, and there is a problem that images cannot be stored as images for a long period of time. Furthermore, since hard copy images produced by so-called printers cannot be rewritten, there is a problem in that the amount of paper used increases. On the other hand, although cards such as cash cards and credit cards are widely used, there is also a demand for recording amounts and other information on these cards. Although it is possible to meet these demands by using a flat display device, for example, the device has disadvantages such as requiring a power source and having a complicated structure.

The present invention has been made in view of the above-mentioned drawbacks of the prior art. The object of the present invention is to provide an image recording method that allows practical handling of recording media.

[Means for Solving the Problems] The present invention makes a liquid crystal element having a thermo-optic effect sandwiched between substrates, and makes the surface of the liquid crystal element transparent by heating the entire liquid crystal element and applying an electric field. First, image information is written by locally heating means.

The liquid crystal used in the present invention is preferably a mixed liquid crystal of nematic liquid crystal and cholesteric liquid crystal, or a smectic liquid crystal having a nematic phase.More specifically, the general formula: (However, in the above formula, R has 1 to 10 carbon atoms. A liquid crystal containing 4'-alkyl-4-fluorobiphenyl represented by ) is used. Examples of compounds represented by the above general formula include 4'-pentyl-4-fluorobiphenyl, 4'-7'ropyru-4-fluorobiphenyl, etc., and all compounds in which R has 1 to 10 carbon atoms, They can be used alone or in mixtures or in combination with other liquid crystal materials.

[Function] The operating principle will be explained when a smectic liquid crystal is used as a liquid crystal exhibiting a thermo-optic effect.

When the liquid crystal layer is heated, the orientation state of the liquid crystal molecules becomes an isotropic liquid phase state. Thereafter, during the cooling process, the liquid crystal layer changes from an isotropic liquid phase state to a nematic phase and a smectic A phase, and its alignment state is stabilized in the smectic A phase. When an electric field is applied while the state in the liquid crystal layer passes through the nematic phase, the molecules in the liquid crystal layer become vertically aligned due to the effect of slow cooling of the liquid crystal and the alignment effect of the electric field, resulting in an optically transparent state. becomes. On the other hand, in the cooling process,
When no voltage is applied, the molecular arrangement within the liquid crystal layer is rapidly cooled while remaining in a random state of an isotropic liquid phase, resulting in an optically cloudy state.

The liquid crystal containing the compound represented by the above general formula exhibits a smectic phase at room temperature, has a low melting point, and has a low viscosity in the liquid crystal state. Therefore, in the image recording method of the present invention, the operating temperature and operating threshold voltage can be set low, and writing and erasing of information to the liquid crystal element becomes extremely easy.

[Example] An example of the image recording method of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 is a block diagram showing one embodiment of the liquid crystal element used in the present invention. In Figure 8, 1 and 3 are substrates of 7 glass plates. In the fifth embodiment, the thickness of the substrate l is 507L. ■, board 3
The thickness of the substrate was set to 1■■, and the inner surface of each was subjected to vertical alignment treatment, and the space thickness between the upper and lower substrates was set to 20 layers. Place it between these two boards at room temperature.

A liquid crystal element 4 was obtained by encapsulating 4'-propyl 70-robiphenyl exhibiting a block phase.

A method of recording an image on this liquid crystal element 4 will be explained next. Second
Each recording process on the liquid crystal element 4 is shown in FIGS.

FIG. 2(a) is a diagram showing the heating process. Here, the liquid crystal element 4 is sent in the direction of the arrow by a belt 20, and the liquid crystal element 4 is heated to an isotropic liquid phase by a power supply lO and a resistance wire or a heating lamp 5. do.

FIG. 2(b) is a diagram showing the process of applying an electric field by the corona charger 6. Here, 20V/10g is applied to the liquid crystal 2 of the liquid crystal element 4 sent by the belt 21 in the direction of the arrow.
An electric field of about m is applied. In this case, while an electric field is applied to the liquid crystal 2, the liquid crystal layer needs to be cooled through an isotropic liquid phase to a smectic phase, so it is desirable that the charging width be relatively wide. By going through these two processes, the image display surface of the liquid crystal element 4 becomes transparent.

FIG. 2(c) is a diagram showing the thermal writing process. In FIG. 2(C), the liquid crystal element 4 that has come into contact with the thermal head 7 is sent by the platen roller 9 in the direction of the arrow. At this time, the liquid crystal 2 is heated from the smectic phase to the isotropic liquid phase in accordance with the local heat generation of the thermal head 7 controlled by the signal source 8, but in this process,
Since no electric field is applied, the liquid crystal 2 is rapidly cooled after passing through the thermal head 7 and becomes cloudy. That is, the selected surface portion of the liquid crystal element 4 is locally heated by the thermal head 7 and becomes cloudy, creating an optical density difference between the selected surface portion and the unheated portion, thereby recording image information.

In this example, in the heating process, heat is applied so that the temperature at which the liquid crystal 2 becomes an isotropic liquid crystal phase is 43°C or higher.Then, in the electric field application process, the corona charger 6 is heated to about 40°C.
When an electric field with an electric field strength of 30 V/20 h 11 was applied, the display surface of the liquid crystal element 4 became transparent. moreover,
In the thermal writing process, the liquid crystal 2 mentioned above is again
As a result of pulsed heat application using a thermal head to maintain a temperature of 3° C. or higher, a good cloudy image could be obtained.

The cloudy image thus obtained had good memory even at room temperature, and the memory did not change even with changes in temperature or body temperature when handled with one hand.

In the above embodiment, if the heat from the thermal head 7 is diffused by the substrate 1 on one side of the liquid crystal element 4, the image will be distorted, so it is desirable that the thickness of the substrate 1 on one side be several hundred mm or less.

[Application Example 1] By mixing a dye into the liquid crystal 2, it was possible to obtain not only two types of display, "transparent" and "cloudy", but also color recording. Furthermore, as another application example, a flexible recording medium could be obtained by using a substrate such as PET (polyethylene terephthalate) instead of a glass substrate.

[Effects of the Invention] In the present invention, a liquid crystal exhibiting a thermo-optic effect is used as an image information recording medium, and an image is recorded by the thermo-optic effect, which saves image information more easily than conventional methods. , can be easily rewritten. Moreover, the recording medium of the present invention requires less heat to be applied during image recording.
This is an energy-saving recording method, and the medium can be handled at room temperature after recording, making it extremely practical.

Furthermore, since the compound of the general formula shown in the present invention has high mutual solubility with other conventionally known liquid crystal substances, it is possible to obtain a wide range of liquid crystal mixtures and to obtain liquid crystal elements having desired characteristics. can. Therefore, the design of the image recording process becomes extremely easy.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a liquid crystal element used in the present invention, and FIGS. 2(a) to (C) are explanatory diagrams of each recording process in an embodiment of the image recording method according to the present invention. It is. 1.3...Substrate, 2...Liquid crystal, 4...Liquid crystal element,
5... Heat lamp, 6... Corona charger, 7...
Thermal head, 8... Signal source, 9... Platen roller, 10... Power supply, 20, 21... Belt.

Claims (1)

[Scope of Claims] 1) A liquid crystal element comprising a liquid crystal exhibiting a thermo-optical effect sandwiched between upper and lower substrates, a means for externally heating the liquid crystal element, a means for applying an electric field, and a means for locally heating the liquid crystal element. In an image recording method in which image information is recorded by sequentially applying these means to the liquid crystal element, the liquid crystal used in the liquid crystal element has a general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, the above An image recording method characterized by containing a 4'-alkyl-4-fluorobiphenyl represented by the formula (in which R represents an alkyl group having 1 to 10 carbon atoms). 2) The image recording method according to claim 1, wherein the means for locally heating is a thermal head. 3) The image recording method according to claim 1, wherein the means for applying the electric field is a corona charger.