JPS61167922A - Image recording medium - Google Patents

Abstract

PURPOSE:To make possible the preservation and rewriting of an image by sandwiching a porous material which is formed into a sheet-like thin film with a pair of flexible substrates and packing the pores of the porous material with a liquid crystal material exhibiting a thermooptic effect. CONSTITUTION:A PET sheet having 50mum film thickness is used as the flexible substrates 1 and 2. A 'Teflon(R)' porous body having 40mum film thickness, 1mum average pore size and 75% voids is used for the porous material 3 of the thin film. The liquid crystal which exhibits a smectic A phase at an ordinary temp. is packed into the pores of the material 3 by which an image recording medium 4 is obtd. The thin film consisting of the porous material having prefer ably 20-100mum film thickness, 0.1-1mum average pore size and 50-75% voids is adequate. A liquid crystal mixture composed of a nematic liquid crystal and cholesteric liquid crystal or a smectic liquid crystal having a nematic phase, etc. are used as the liquid crystal. A large area ratio of the recording medium is thus easily obtd. and the flexible recording medium is made obtainable by the integral formation with the flexible substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording medium, and particularly to a rewritable image recording medium.

[Prior Art] and [Problems to be Solved by the Invention] In recent years, the demand for using rewritable media for image recording has increased, but the conventional technology has had some practical problems. For example, display devices have come into widespread use in order to make offices paperless, but display devices such as CRTs have difficulty displaying high-definition texts such as text, and images can be stored as images for long periods of time. The problem is that it can't be done. 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 was made in view of the problems of the prior art described above, and an object of the present invention is to provide a recording medium on which images can be stored and rewritable.

[Means for Solving the Problems] The present invention uses a porous material in the form of a thin film,
It is sandwiched between a pair of flexible substrates, and the pores of the porous material are filled with a liquid crystal material that exhibits a thermo-optic effect.

[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 phase, and its alignment state is stabilized in the smectic phase. When an electric field is applied when the state in the liquid crystal layer passes through the nematic phase, the molecular alignment in the liquid crystal layer becomes vertically aligned M'& due to the effect of slow cooling of the liquid crystal and the alignment effect of the electric field.
It becomes optically transparent. On the other hand, during the cooling process, if no voltage is applied, the molecular arrangement within the liquid crystal layer remains in a random isotropic liquid phase and rapidly cools down, resulting in an optically cloudy state.

In the present invention, image information is written by applying the property of liquid crystal exhibiting such a thermo-optic effect. That is, by sequentially applying heat and voltage to the recording medium holding the liquid crystal layer described above, two display states of "transparent" and "cloudy" can be obtained. Furthermore, in the present invention, the liquid crystal material is sandwiched between flexible substrates, and the liquid crystal material is filled into the pores of a thin sheet-like porous material. You can get sex.

[Example] FIG. 1 is a block diagram showing an example of an image recording medium according to the present invention. In this example, flexible substrates 1 and 2 are made of PET (polyethylene Use a sheet of tereftate. In addition, as the thin film porous material 3, a Teflon porous body (trade name: Chloropore) with a film thickness of 404 m, an average pore diameter of 14 m, and a porosity of 75% is used, and in the pores of this porous material 3, An image recording medium 4 was obtained, which was a liquid crystal (trade name, manufactured by BHD Co., Ltd., filled with rS-5J, not shown) exhibiting a smectic A phase at room temperature.

A case where image information is actually recorded using the image recording medium 4 obtained in this manner will be described.

FIGS. 2(a) to 2(C) show each recording process on the image recording medium 4. FIG.

FIG. 2(a) is a diagram showing the heating process (or erasing process). The image recording medium 4 shown in FIG.
The liquid crystal in the image recording medium 4 is heated to an isotropic liquid phase by the power supply 12 and the heating lamp 5.

FIG. 2(b) is a diagram showing the process of applying an electric field by the corona charger 7. At this time, it is necessary to apply an electric field of preferably about 20 V/10 pm to the liquid crystal 1 in the image recording medium 4. In this embodiment, the surface potential difference of the substrate is 200 to
An electric field was applied to about 300V. In the process of applying the electric field, the liquid crystal in one image recording medium 4 is cooled from an isotropic liquid phase to a nematic phase to a smectic phase, and becomes transparent.

Next, FIG. 2(C) is a diagram showing the writing process. Image information is recorded on the image recording medium 4 through this writing process. That is, the image recording medium 4 that has come into contact with the thermal head 8 is sequentially fed by the platen roller 9. At this time, the thermal head 8 controlled by the signal source 10 generates heat in response to the image information, and due to this heat generation, the liquid crystal in the image recording medium 4 is heated from the smectic phase to the isotropic liquid phase. Since the phase is rapidly cooled without applying an electric field, it becomes cloudy and predetermined image information is written.
It became cloudy when heat was applied at about J/cm''.

The thin film made of the porous material used in the present invention preferably has a film thickness of 20 to 10 QILm and an average pore diameter of 0.1 to 14
m, a porosity of 50 to 75% is suitable, and in addition to the above examples, a porous material with a film thickness of 20 pm and an average pore diameter of 0.02 g
Good results were also obtained using polychloroacrylonitrile with a porosity of 50 to 60%.

Similar effects can also be expected by using other porous polymers, sintered ceramics, or thin films of metal with holes as shown in Figure 3 as the porous material. 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.

Furthermore, although a flexible recording medium was provided in the above embodiments, a rigid recording medium could also be obtained by using glass or the like as a 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 images are recorded using the thermo-optic effect, so that image information can be easily stored and rewritten. can. In addition, by filling the pores of the thin sheet-like porous material with liquid crystal, it is easy to increase the area of the recording medium, and by integrally forming it with a flexible substrate, flexible recording It became possible to obtain media.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an image recording medium according to the present invention, FIG. 2 (&) is a diagram showing a heating process, and FIG.
b) A diagram showing an electric field application process, FIG. 2(C) is a diagram showing a thermal writing process, and FIG. 3 is a diagram showing another example of porous material.

Claims (1)

[Claims] An image recording medium comprising a thin film of a porous material and a pair of flexible substrates sandwiching the thin film, the pores of the thin film being filled with a liquid crystal material exhibiting a thermo-optic effect. .