JP3254651B2 - Reversible thermosensitive recording material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material for recording and erasing by utilizing a change in transparency depending on temperature, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording materials which can form a temporary image and erase the image when it is no longer needed have attracted attention. A typical example is a glass transition temperature (Tg) of 50 to 60 ° C to 80 ° C.
A reversible thermosensitive recording material is known in which a low-molecular organic substance such as a higher fatty acid is dispersed in a resin base such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature of less than 100 ° C. 54-119377, JP-A-55-15
4198, JP-A-63-39376, JP-A-63-393
Publications such as 107584)

[0003] However, the fact is that such reversible thermosensitive recording materials do not always have good reversible sensitivity characteristics. Therefore, studies are being made from various angles. For example, by adding at least one kind of dicarboxylic acid to the reversible thermosensitive layer (thermosensitive recording layer), the transparency temperature range is widened, and erasing and printing with a thermal head and a heat roll can be repeated (Japanese Patent Laid-Open No. 2-1363). ), And by increasing the content of the organic low-molecular substance toward the support, the repetition of erasure / printing is further improved.

[0004] The reversible thermothermographic material described above is significantly improved in terms of erasing and printing as compared with conventional materials. However, when the reversible thermosensitive recording material is made transparent at a high temperature range, it becomes difficult to become transparent and so-called residual recording is observed. On the other hand, it can be seen that afterimages also occur in the reversible thermosensitive recording material.

According to the study of the present inventors, this afterimage occurs because particles of a high-melting organic low-molecular substance and a low-melting organic low-molecular substance mixed and dispersed in a reversible thermosensitive layer,
This is thought to be due to the fact that the reversible thermosensitive recording material is gradually separated by repeated erasure / printing, and the high melting point organic low molecular weight substance is distributed on the support side and the low melting point organic low molecular weight substance is distributed on the surface side.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive recording system which eliminates the above-mentioned drawbacks and has excellent durability for repeated printing and erasing without being largely influenced by various environmental atmospheres. The present invention provides a material and a method for producing the same.

According to the present invention, the following inventions are provided.
You. In a reversible thermosensitive recording material provided with a thermosensitive recording layer whose transparency reversibly changes depending on temperature on a support, the thermosensitive recording layer has a melting point of 30 to 100 ° C. with a resin matrix.
Organic low molecular weight organic material particles having a melting point of less than
Organic low-molecular substance particles having a temperature of 0 ° C. or higher, and having a melting point of 30 to less than 100 ° C. as approaching the support.
Increased content of a low-molecular-weight organic material particles, the reversible thermosensitive recording material in which the content of melting point of 100 ° C. or more organic low-molecular material particle is characterized by being increased with increasing distance from the support.

The low-melting organic low-molecular substance and the high-melting organic low-molecular substance in the present invention are relative to each other, and naturally include an organic low-molecular substance having a melting point in between. However, in order to make the present invention easy to understand, in this specification, for the sake of convenience, low-melting organic low-molecular particles and high-melting organic low-molecular particles will be described separately. The low-melting organic low-molecular substance has a melting point of 3
The melting point of the organic low molecular weight substance having a high melting point of 0 to less than 100 ° C, preferably 50 to less than 100 ° C, is suitably 100 to 160 ° C.

The second aspect of the present invention is a method for producing a reversible thermosensitive recording material, which has a melting point of 30 to 100 ° C. on a support.
Forming a layer mainly composed of some low-molecular organic material particles and the resin, thereon, by laminating a layer having a melting point as a main component of organic low-molecular material particle and a resin is 100 ° C. or higher, the support
The lower the melting point of the organic low molecular weight particles,
As the weight increases and moves away from the support, the higher melting point
Forming a heat-sensitive recording layer in which the content of the organic low-molecular substance particles is increased . Here, the reversible thermosensitive layer is formed by two layers for the sake of convenience, and three or more layers may be used as long as the above-described concept is satisfied.

In the method for producing a reversible thermosensitive recording material of the present invention, the amount of the residual solvent in both the layer on the support side and the layer on the surface side is adjusted to 50 μg / cm ² or less, preferably 40 μg / cm ² or less. Is desirable.

Hereinafter, the present invention will be described in more detail. As mentioned above, for the sake of convenience, it is assumed that the thermosensitive recording layer is formed of two layers. The reversible thermosensitive recording material of the present invention is described in JP-A-2-1363, JP-A-5-8538, JP-A-54-119377, JP-A-55-154198 and the like on a support. In a base material such as a vinyl chloride resin, for example, a layer in which organic low-molecular-weight material particles mainly composed of a high-melting fatty acid having a low melting point is formed is formed. By forming a layer in which organic low-molecular substance particles containing a higher fatty acid as a main component are dispersed, a heat-sensitive recording layer (thickness: 5 to 30 μm) in which an upper layer has a high melting point and a lower layer has a low-melting organic low-molecular substance distribution Preferably 8-20μ
m).

Here, the heat-sensitive layer is formed with two layers, but three or more layers may be formed as described above. However, in each case, the low-melting organic low-molecular substance particles are located on the support side, and the high-melting organic low-molecular substance particles are located on the surface side. is necessary. In the figure, 1 is a support, 2 is a heat-sensitive layer, 21 is a low-melting organic low-molecular substance particle, 22 is a mixture of a high-melting organic low-molecular substance and a low-melting organic low-molecular substance (or high-melting organic low-molecular substance) Organic low-molecular substance particles having an intermediate melting point between the melting point and the low melting point), 23 represents high-melting organic low-molecular substance particles, and 25 represents a resin matrix.

In the reversible thermosensitive recording material of the present invention,
If necessary, refer to JP-A-62-221087 and JP-A-6-221087.
A protective layer as described in JP-A-2-152550, JP-A-63-310600, JP-A-5-8538 and the like can be provided. Further, an intermediate layer as described in JP-A-1-133798 can be provided between the support and the protective layer, if necessary.

As the support, a plastic sheet such as polyester, a glass plate, a metal plate or the like is used. The support may be provided with other recording or storage materials, such as magnetic, magneto-optical, IC, and the like. In order to increase the contrast, an aluminum vapor deposition or colored layer may be provided on the surface of the support, or an air layer may be provided. In addition, a resin such as polyester, polyurethane, polyvinyl alcohol, or polyvinyl chloride can be provided between the support and the heat-sensitive layer to increase the adhesiveness. Is also good.

When printing (white turbidity) of this reversible thermosensitive recording material with a thermal head and erasing with a thermal head, a heat roll, a heat block and a hot stub were repeated, an afterimage could not be formed. This is because the energy from the thermal head is higher in the upper layer of the heat-sensitive recording layer and lower in the lower layer, so that it uniformly melts and causes transparent turbidity, and even if the low-melting organic low-molecular substance partially melted moves to the upper layer. This is probably due to the presence of a high-melting organic low-molecular substance that can be mixed. On the other hand, in the conventional heat-sensitive recording layer, it is presumed that, due to energy shortage, half-way energy repetition occurred, and only the material having a low melting point was melted, separated upward, and changed to the state shown in FIG. You.

From these phenomena, it is considered that in the reversible thermosensitive recording material of the present invention, an organic low-molecular substance having a high melting point of about 100% exists near the upper side (upper layer) of the thermosensitive recording layer. Can be In addition, when an organic low-molecular substance having a high melting point is present in the upper layer, head scum due to exudation with a low melting point is reduced, and particles can be present even within 95% of the heat-sensitive layer from the support side. Further, the content of the particles existing at a thickness of 1/5 on the side of the support is better when the area ratio is 20% or less. This is because the separation of an organic low-molecular substance, which is a part of the afterimage, starts to flow to the lower layer boundary or prevents melting due to halfway energy.

[0017]

Next, the present invention will be described more specifically with reference to examples. Parts here are by weight.

Example 1 A mixture of 10 parts of Byron 200 (manufactured by Toyobo Co., Ltd.) and 90 parts of toluene was applied on a polyester film (manufactured by Toray Industries, Inc., metal me) having a thickness of about 50 μm using a wire bar. After drying for a minute, an adhesive layer having a thickness of 0.5 to 1.0 μm is formed. Next, 1 part of lignoceric acid (manufactured by Miyoshi Oil & Fat Co., mp 80 ° C.) 1 part Vinyl chloride-vinyl acetate copolymer (manufactured by Kaneka Corporation, degree of polymerization 1800, vinyl acetate ratio 20%) 3.9 parts THF (tetrahydrofuran) 20 parts toluene 7 parts Polysiloxane copolymer (manufactured by Toray Dow Corning Co., Ltd., 0.1 parts ST102PA1% THF) was coated with a mixture using a wire bar, and then 100 parts.
C. for 2 minutes to dry the lower heat-sensitive recording layer (8-9 μm thick).
m). On this, eicosane diacid (manufactured by Okamura Oil Co., mp 120 ° C.) 1 part Vinyl chloride-vinyl acetate copolymer (manufactured by Kaneka Corporation, degree of polymerization 1800, vinyl acetate ratio 20%) 3.9 parts THF 20 parts Toluene 7 parts Polysiloxane copolymer (manufactured by Toray Dow Corning Co., Ltd., 0.1 part ST102PA1% THF) was applied with a mixture using a wire bar, and then 100 parts.
At 2 ° C. for 2 minutes to form an upper heat-sensitive recording layer (8 to 9 μm thick).
m). Subsequently, a mixture consisting of 10 parts of urethane acrylate (C7-157, manufactured by Dainippon Ink and Chemicals, Inc.) and 10 parts of IPA (isopropyl alcohol) was applied using a wire bar, and 90 ° C.
And then irradiate with a UV lamp (80 W / cm) and cure to form a protective layer (4-5 μm thick).
A black magnetic card was stuck to this to prepare a reversible thermosensitive recording material.

The reversible thermosensitive recording material was subjected to a durability test (500 intermittent tests, storage: 50) by an issuing machine and a processing machine (JR-10 and JS-10) manufactured by Sankyo Seiki Co., Ltd.
C., 50 to 70% RH), the results shown in Table 1 were obtained. Further, when this heat-sensitive recording layer was polished from above, below and above the surface to extract fatty acids and measured by liquid chromatography, the ratio with lignoceric acid was as follows: upper layer: eicosane diacid 40-80%, middle layer: eicosan 2
The acid was 30 to 60%, the lower layer: eicosane diacid 10 to 40%, and the residual solvent when only the upper layer was formed was 55 μg / cm ^{2 as} measured by gas chromatography.

Example 2 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that only the upper heat-sensitive recording layer was dried at 120 ° C. When subjected to the durability test of Example 1, the results shown in Table 1 were obtained. The residual solvent when only the upper layer was formed was 45 μg / cm ^{2 as} measured by gas chromatography.

Example 3 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that only the upper and lower heat-sensitive recording layers were formed at 120 ° C. When this was subjected to the durability test of Example 1, the results shown in Table 1 were obtained. The residual solvent in the lower layer
45 μg / c as measured by gas chromatography
m ² .

Example 4 The reversibility was measured in the same manner as in Example 3 except that the upper layer of the heat-sensitive recording layer was air-dried for several seconds until the drying temperature reached 120 ° C. and dried immediately before the precipitation of eicosane diacid. A thermal recording material was prepared. When this was subjected to the durability test of Example 1, the results shown in Table 1 were obtained. When the thermosensitive recording layer of the reversible thermosensitive recording material was observed with a TEM image, the particles distributed from the support side in Examples 1 to 3 to 90% from the support side were distributed to 95% in thickness. Was seen. Further, the content of the organic low-molecular substance in the heat-sensitive recording layer was measured as shown in FIG.

COMPARATIVE EXAMPLE 1 A thermosensitive recording layer forming solution was applied in a single layer with a wire bar using the same mixture of upper and lower layers as in Example 1.
A reversible thermosensitive recording material was prepared and subjected to a durability test in the same manner as in Example 1 except that the material was dried to form a thermosensitive recording layer having a thickness of 16 to 17 μm. The results shown in Table 1 were obtained. The use of this comparative reversible thermosensitive recording material resulted in high afterimages. The thermosensitive recording layer was polished from the surface above, inside and below to extract fatty acids and measured by liquid chromatography. Eicosane diacid was converted to lignoceric acid. Upper layer: 40
６０60%, middle layer: 40-60%, lower layer 40-60%.

Example 5 A reversible thermosensitive recording material was prepared in the same manner as in Example 4 except that the formulation of the lower layer of the thermosensitive recording layer was as follows. When this was subjected to the same test as in Example 1, the results shown in Table 1 were obtained. 0.5 parts Lignoceric acid (mp 80 ° C) 0.5 parts Behenyl behenate (mp 70 ° C)

Comparative Example 2 A reversible thermosensitive recording material was prepared in the same manner as in Example 4 except that the formulations of the upper and lower layers of the thermosensitive recording layer were as follows. When this was subjected to the same test as in Example 1, the results shown in Table 1 were obtained. (Upper layer) Lignoceric acid 0.5 part Eicosane diacid 0.5 part Vinyl chloride-vinyl acetate copolymer 3.9 parts THF 20 parts Toluene 7 parts ST102PA (1% THF) 0.1 part (Lower layer) Behenic acid 0 0.5 parts Eicosan diacid 0.5 parts Vinyl chloride-vinyl acetate copolymer 3.9 parts THF 20 parts Toluene 7 parts ST102PA (1% THF) 0.1 part

Example 6 Only the amount of resin in the upper and lower layers of the heat-sensitive recording layer was 2.9 in the upper layer.
A reversible thermosensitive recording material was prepared in the same manner as in Example 4 except that the lower part and the lower layer were 4.9 parts. When this was subjected to the same test as in Example 1, the results shown in Table 1 were obtained.
Further, the content of the organic low-molecular substance in the heat-sensitive recording layer was measured as shown in FIG.

[0027]

[Table 1]

[0028]

According to the reversible thermosensitive recording material of the present invention, printing and erasing can be repeated for a long period of time.

[Brief description of the drawings]

FIG. 1 is a view for explaining an outline of a reversible thermosensitive recording material of the present invention.

FIG. 2 is a diagram for explaining an outline of a comparative reversible thermosensitive recording material.

FIG. 3 is a graph showing the content of the organic low-molecular substance in each layer with respect to the total organic low-molecular substance when the heat-sensitive recording layer of the reversible thermosensitive recording material of Example 4 is divided into five equal parts in the thickness direction.

FIG. 4 is a graph showing the content of the organic low-molecular substance in each layer relative to the total organic low-molecular substance when the heat-sensitive recording layer of the reversible thermosensitive recording material of Example 6 is divided into five equal parts in the thickness direction.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 support 2 heat-sensitive recording layer 21 low-melting organic low-molecular substance particles 22 particles obtained by mixing high-melting organic low-molecular substance and low-melting organic low-molecular substance 23 high-melting organic low-molecular substance particles (or high-melting organic low-molecular substance particles) Organic low-molecular substance particles having a melting point between the melting point and the low melting point) 25 Resin matrix

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-129793 (JP, A) JP-A-2-1363 (JP, A) JP-A-7-137449 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B41M 5/36

Claims (3)

(57) [Claims] 1. A reversible thermosensitive recording material comprising a support and a thermosensitive recording layer whose transparency reversibly changes depending on temperature, wherein the thermosensitive recording layer has a melting point of 30 % with a resin matrix.
Organic low molecular weight material particles having a melting point of less than -100 ° C;
And low-molecular-weight organic substance particles having a melting point of 100 ° C. or higher, and having a melting point of 30 to 100 ° C. as approaching the support.
Increased content of the organic low-molecular material particle is less than a reversible thermosensitive recording the content of the melting point of 100 ° C. or more organic low-molecular material particle moves away from the support is characterized by being increased material. 2. The method according to claim 1, wherein the melting point on the support is from 30 to less than 100 ° C.
Forming a layer mainly composed of certain organic low molecular material particle and a resin, on which, by laminating a layer having a melting point as a main component an organic low-molecular material particle and a resin is 100 ° C. or higher, the support To
Inclusion of the low-melting organic low-molecular substance particles as they approach each other
The high melting point as the amount increases and moves away from the support.
A method for producing a reversible thermosensitive recording material, comprising forming a thermosensitive recording layer in which the content of low-molecular substance particles is increased . 3. The method for producing a reversible thermosensitive recording material according to claim 3, wherein both the layer on the support side and the layer on the surface side have a residual solvent amount of 50 μg / cm ² or less.