JPH0130638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material on which information can be reversibly recorded and erased by heating.

Conventionally, spiropyran compounds and metal complex crystals are known as substances that change color and fade depending on temperature, and are used in thermometers and the like. However, this substance repeats reversibly coloring and decoloring depending on temperature changes, has no memory properties, and is used in temperature display materials and the like.

On the other hand, in recent years, thermosensitive materials have been discovered that can reversibly cycle through a cloudy state and a transparent state depending on the heating temperature, and can stably maintain either state below a specific temperature. The heat sensitive body is composed of a matrix material made of a polymer or the like, and an organic low molecular substance dispersed in the matrix material,
The properties of the heat sensitive body are mainly based on the behavior of the organic low molecular weight substance. The heat sensitive body has two state transition temperatures, and depending on the difference in heating temperature,
Does it appear cloudy when cooled below a certain temperature?
Or it represents a transparent state. Heat-sensitive recording materials have been proposed that utilize these properties to freely record and erase information.

However, image information is recorded on the recording material using the thermosensitive member using a heating recording device such as a thermal head, but when the image information is repeatedly recorded many times, the matrix material and the organic low molecule The substance becomes oxidized and no longer exhibits the aforementioned properties. Furthermore, when recording image information, the thermal characteristics of the head change due to the adhesion of matrix materials and organic low-molecular substances to a heating recording device such as a thermal head. Moreover, the surface of the recording material becomes rough and uneven. In addition, even if a matrix material with a high softening temperature is used and there is no guarantee that the matrix material or organic low-molecular substances will adhere to the device due to softening, repeated use of a heating recording device such as a thermal head can cause the surface of the recording material to deteriorate. It has the disadvantage that it wears out and causes diffuse reflection.

The purpose of the present invention is to solve the above-mentioned drawbacks of recording materials, and to make it possible to record and erase information reversibly by heating, and to prevent chemical and physical deterioration of the recording materials. Our goal is to provide durable recording materials.

The heat-sensitive recording material of the present invention comprises polyvinyl chloride,
A matrix material made of at least one kind of polymer selected from a vinyl chloride copolymer, a vinylidene chloride copolymer, and a polyester, and a saturated or unsaturated fatty acid having 10 to 30 carbon atoms dispersed in the matrix material. A transparent antioxidation film and a transparent wear-resistant film are formed in this order on a heat sensitive body made of at least one organic low-molecular substance selected from the group consisting of esters, amides, and ammonium salts of fatty acids.

A mechanism for reversibly recording and erasing information by heating the heat-sensitive recording material of the present invention will be explained.

The heat sensitive body of the heat sensitive recording material of the present invention has a specific temperature.
When maintained at t ₀ or higher, the state changes depending on the temperature. That is, the thermosensitivity has two state transition temperatures t ₁ and t ₂ at a temperature higher than t ₀ .
(t ₁ <t ₂ ), and when the heat-sensitive member is heated to t ₂ or higher and then cooled to t ₀ or lower, it becomes cloudy and exhibits the best light-shielding property. When this heat-sensitive member in the highest light-shielding state is heated and maintained in a range of t ₀ or more and less than t ₁ and then cooled to t ₀ or less, the heat-sensitive member loses its white turbidity and exhibits a reduced light-shielding property. In the above heating temperature range, as the heating temperature of the cloudy heat sensitive body approaches t ₁ , the cloudiness becomes thinner and becomes nearly transparent when the heating temperature is cooled below t ₀ , and the temperature is maintained in the range of t ₁ or more and less than t ₂ . After cooling to below t ₀ , it becomes transparent. Therefore, if a heat-sensitive member in the maximum light-shielding state is heated and held at a temperature in the range of t ₀ or more but less than t ₁ and then cooled to t ₀ or less, as the heating holding temperature increases from t ₀ to t ₁ , the cooling temperature increases. The white turbidity of the thermosensitive member at this time shows the white turbidity of the initial maximum light-shielding state to the continuous intermediate light-shielding state until it becomes transparent.

The color tone change depending on the temperature change of the heat sensitive body is mainly based on the behavior of the organic low molecular weight substance in the heat sensitive body.

In this way, the thermosensitive body can reversibly repeat the cloudy state and the transparent state, and at a specific temperature t ₀
It is also possible to stably maintain any of the states below. Therefore, information such as images and characters can be recorded by partially heating it.
Moreover, since it can be erased when unnecessary, it is suitable as a recording material.

Hereinafter, the heat-sensitive recording material of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a sectional view of the heat-sensitive recording material of the present invention, and the manufacturing method thereof will be described below, as well as its structure will be explained in detail.

As shown in FIG. 1, on a base material 1 such as plastic or glass, the weight ratio of the matrix material to the organic low molecular weight substance is 3:1 to 16:1, preferably 6:1 to 12:1. The mixture is coated using, for example, a casting method to form a film-like heat sensitive member 2 in which both components are uniformly dispersed, with a thickness of 5 to 100 μm, preferably 10 to 50 μm.

Matrix material is a material that forms a film that holds organic low-molecular substances evenly dispersed.
By including a particulate organic low-molecular substance that changes its state from cloudy to transparent in the matrix material, it has the effect of more clearly indicating the state change. Therefore, it is suitable for this matrix material to be a polymer that has good transparency, is mechanically stable, and is easy to form into a film. Such matrix materials include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. Use one or more polymers selected from vinyl chloride copolymers such as polymers, vinylidene chloride copolymers such as vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers, and polyesters. I can do it.

In the present invention, the organic low-molecular-weight substance that is the constituent material of the thermosensitive member changes its refractive index as the state changes due to heating, and at the same time maintains that state through interaction with the matrix member. One or more selected from acids, saturated or unsaturated fatty acids having 10 to 30 carbon atoms, such as arachic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, etc., or esters, amides, and ammonium salts of these fatty acids. Compounds can be used.

There are preferable combinations of such matrix materials and organic low-molecular substances. One of the reasons for this combination is that the refractive index of the matrix material and the refractive index of the organic low-molecular substance are selected so that they are equal at temperature t ₁ and different at temperature t ₂ or higher.

In addition, the following alkanols can be used as substances having similar properties to the organic low-molecular substances;
Alkanediols; halogenalkanols or halogenalkanediols; alkylamines; alkanes; alkenes; alkynes; halogenalkanes; halogenalkenes; halogenalkynes; cycloalkanes; cycloalkenes; cycloalkynes;
Saturated or unsaturated halogenated fatty acids or their esters, amides, or ammonium salts; Arylcarboxylic acids or their esters, amides, or ammonium salts; Halogenated arylcarboxylic acids or their esters, amides, or ammonium salts; Thioalcohols; Thiocarboxylic acids Examples include organic low-molecular substances such as acids or their esters, amides, or ammonium salts; carboxylic acid esters of thioalcohols and mixtures thereof. The number of carbon atoms in these compounds is 10 to 60, preferably 10 to 38, particularly preferably 10 to 30. The alcohol group moiety in the ester is saturated or unsaturated,
Furthermore, it may be substituted with halogen. The halogen atom is chlorine or bromine, with chlorine being particularly preferred. Preferably, the halogen compound has 1 to 20 halogen substituents. The aryl group is preferably phenyl or substituted phenyl.

In addition, in this specification, organic low molecular substances are 100 to
700 preferably an organic compound with a molecular weight of 300-500. and the organic low molecular weight substance has a phase change of at least 5%, preferably 5% when it undergoes a phase change from solid to liquid.
It is preferable to use one whose volume changes by ~15%.

Regarding the mixing ratio of the matrix material and the organic low-molecular substance, if the weight ratio of the matrix material is less than 3 to 1 part of the organic low-molecular substance, it is difficult to form a film that properly retains the organic low-molecular substance in the matrix material. If the matrix material exceeds 16, the amount of organic low-molecular substances that become cloudy due to temperature is small, so when used as a recording material, recorded information cannot be clearly read, which is not preferable. The organic low-molecular substance is preferably uniformly dispersed in the matrix material and sufficiently solidified, and may be partially dissolved in the matrix material.

Base materials include plastic, glass, paper, cloth,
Although metal can also be used, it is preferable that the change in cloudiness of the heat-sensitive member can be clearly seen, and transparent plastic or glass is usually used. Furthermore, when plastic is used as the base material, it is preferable that it has good thermal weldability and adhesion to the matrix material, and the preferred plastic is determined by the type of matrix material used.

As other methods for forming the film-like heat-sensitive member 2, a wide variety of known methods for molding the polymer used as the matrix material can be used.

In addition, in order to impart appropriate physical properties to the heat sensitive body,
In order to improve processability, plasticizers may be added as necessary.
A lubricant, a stabilizer, etc. can be added.

In addition, as shown in FIG. 2, the thermosensitive body 2 can be formed thickly by using a large amount of matrix material and organic low-molecular substance, and a base material can be used if the thermosensitive body itself can sufficiently maintain its solid shape. It is also possible to constitute a heat-sensitive recording material.

Next, SiO ₂ , SiO, MgO, ZnO,
A transparent inorganic substance with relatively low oxygen permeability such as TiO ₂ is coated with a film thickness of 0.1 to 10 μm, preferably 0.5 to 2 μm.
The anti-oxidation film 3 is formed by laminating the two layers.

Next, a transparent and highly abrasion-resistant inorganic material such as Al ₂ O ₃ or Ta ₂ O ₅ is deposited on the anti-oxidation film 3 to a thickness of 0.1 to 10 μm by sputtering or vacuum evaporation.
The wear-resistant film 4 is preferably laminated to a thickness of 0.5 to 2 μm.

Anti-oxidation film 3 and wear-resistant film 4 thus created
When writing image information using a heating recording device such as a thermal head, the recording material with the heat sensitive body 2 protected by the abrasion resistant film 4 protects the heating recording device from matrix-forming polymers and organic low molecules. Even if substances do not stick to the recording material and polymers with a high softening temperature are used, so there is no risk of sticking to the device due to softening, the recording material surface is prevented from abrasion due to frequent writing, resulting in increased durability. Excellent. Furthermore, by providing the anti-oxidation film 3, chemical deterioration due to oxidation is prevented even if frequent heating is repeated, so that the light-shielding performance is extremely unlikely to deteriorate. For these reasons, a recording material that can withstand frequent repeated use is provided.

Hereinafter, examples and comparative examples of the recording material of the present invention will be given and explained in more detail.

Example 1 A mixture consisting of 1.5 g of Saran resin R-200 (manufactured by Asahi Dow Co., Ltd., vinylidene chloride-acrylonitrile copolymer) and 0.25 g of behenic acid was sufficiently dissolved in 8 g of tetrahydrofuran, and then placed on a Mylar film (polyester film). Apply with an 8mm blade and heat at 80℃ for 20 minutes.
It was dried for a minute to form a film-like heat sensitive member with a film thickness of 20 μm. Next, SiO ₂ was deposited on the heat sensitive body using an RF sputter to form an antioxidant film with a thickness of 1 μm. Next, Ta ₂ O ₅ was vapor-deposited on the anti-oxidation film using an RF sputter to form a wear-resistant film with a thickness of 2 μm. The heat sensitive body constituting the recording material thus prepared was in a cloudy state. When the recording material was heated and held in a temperature controller at 68° C. and then taken out and rapidly cooled, the cloudiness disappeared and it became a stable transparent state at room temperature.

The recording material was subjected to a surface temperature of 300°C and a pressing pressure of 8
When heated for 2 msec using a thermal head with an applied voltage of 9 W/mm ² and an applied voltage of 9 W/mm ² , the heated area became cloudy. When the cloudy recording material was heated and held in a temperature controller at 68° C. and then taken out and rapidly cooled, the cloudiness disappeared and the recording material became transparent again. This operation was repeated and a transparent and opaque reversible reaction was performed 1000 times, but there was almost no change in this performance.

Example 2 A film-like heat sensitive member was formed on a Mylar film using the same formulation and method as in Example 1. Next, MgO was vapor-deposited on the heat sensitive body using RF sputtering to form an oxidation-preventing film with a thickness of 1 μm. Next, Al ₂ O ₃ was deposited on the oxidation-preventing film using an RF sputter to form a wear-resistant film with a thickness of 2 μm. The thus prepared recording material was made transparent by the same operation as in Example 1, and then the same operation was repeated using a thermal head under the same conditions as in Example 1 to perform a reversible transparent and opaque reaction 1000 times. As in Example 1, there was almost no change in the performance of the recording material.

Comparative Example 1 A film-like heat sensitive member was formed on a Mylar film using the same formulation and method as in Example 1, and was used as a recording material without providing a protective layer. Using a thermal head, the same operation as in Example 1 was carried out under the same conditions to produce a transparent and opaque reversible reaction.
When this was repeated several times, the resin of the heat sensitive body adhered to the thermal head, and the surface of the heat sensitive body became quite rough and uneven, causing diffuse reflection. Furthermore, behenic acid itself no longer became transparent.

Comparative Example 2 A film-like heat susceptor was formed on a Mylar film using the same formulation and method as in Example 1, and then SiO ₂ was evaporated onto the heat susceptor using RF sputtering to give a film thickness of 2 μm.
An anti-oxidation film was formed. A recording material having only a layer of anti-oxidation film on the heat sensitive body without forming an abrasion-resistant film was obtained. Using a thermal head on the recording material, the same operation as in Example 1 was repeated under the same conditions to conduct a transparent and opaque reversible reaction 1000 times.
The light transmittance of the recording material in the transparent state after the completion of the operation is 20% compared to the light transmittance in the initial transparent state.
% had fallen.

As is clear from Comparative Example 1, it has been proven that if a heating recording device such as a thermal head is brought into direct contact with the surface of a heat sensitive body without any protective layer, the surface of the heat sensitive body becomes rough and immediately becomes unusable.

Comparative Example 2 demonstrated that the use of only the antioxidant film caused a decrease in light transmittance, which was thought to be due to surface wear.

From the Examples and Comparative Examples, it was found that the recording material in which the anti-oxidation film and the abrasion-resistant film were formed on the heat susceptor was prevented from chemical deterioration and physical deterioration, had a significantly extended lifespan, and exhibited excellent durability.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of examples of the heat-sensitive recording material of the present invention. DESCRIPTION OF SYMBOLS 1... Base material, 2... Heat sensitive body, 3... Anti-oxidation film, 4... Abrasion resistant film.

Claims (1)

[Claims] 1 A matrix material made of at least one kind of polymer selected from polyvinyl chloride, vinyl chloride copolymer, vinylidene chloride copolymer, and polyester, and a matrix material having 10 to 30 carbon atoms dispersed in the matrix material. A transparent antioxidant film and a transparent wear-resistant film are formed in this order on a heat sensitive body made of at least one organic low-molecular substance selected from saturated or unsaturated fatty acids, or esters, amides, and ammonium salts of the fatty acids. A heat-sensitive recording material.