JPH062428B2 - Thermal recording - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a heat-sensitive recording material, and more particularly to a heat-sensitive recording material capable of recording from both the front surface side of a heat-sensitive layer and the back surface side of a support. Is.

(Prior Art) Thermal recording materials used for recording sheets such as facsimiles and recorders recently, as well as tickets, cards, etc., usually have a leuco dye and a color developer on a support such as paper. A heat-sensitive layer mainly containing a thermochromic composition contained,
It was a type in which recording was performed by heating from the surface side by means of a thermal head, a heating pen, laser light, etc., and reading from the surface side.

However, with the recent expansion of the use of thermal recording media, the thermal head is heated by contacting the thermal head from the backside (non-thermosensitive layer) side of the support for applications such as tags and labels, causing the thermal recording layer on the front side to develop color, and the backside. There was a request from the side to read the recorded image.

(Problems to be solved by the invention) However, as described above, the conventional thermal recording media are unidirectional.
That is, only recording and reading can be done from the heat sensitive layer side,
Recording and reading from the rear direction is impossible.

That is, since the paper of the support is opaque in the conventional thermal recording medium,
Even if recording from the back side (back side), it cannot be read from the back side, so the support must be a transparent film base. It is natural that a thermosensitive recording medium can read a recorded color image from the back side by using this transparent thermoplastic resin film as a support, but at the time of recording from the back side of the support, a support resin by a heating head such as a thermal head is used. Softening of the resin, that is, a sticking phenomenon, etc. occurred due to the contact heating with the heat-sensitive recording, and heat-sensitive recording itself was impossible.

(Means for Solving Problems) The present invention has been made as a result of earnest research to solve the above problems, and a heat-sensitive layer is provided on the surface of a transparent support and a silicone rubber is provided on the back surface of the transparent support. Alternatively, by providing a silicone resin layer, a heat-sensitive recording material was obtained in which recording was possible not only from the surface of the heat-sensitive layer but also from the back surface of the support.

The basic constitution of the thermosensitive recording medium of the present invention is as shown in FIG. In FIG. 1, 1 is a specific transparent support defined in the present invention (hereinafter simply referred to as a transparent support), 2 is a heat-sensitive layer on the upper surface, and 3 is a rear surface treatment made of silicone rubber or silicone resin on the lower surface. It is a layer.

An embodiment having another structure of the present invention is as shown in FIG. The structure is such that an under layer 4, a heat sensitive layer 2, and a protective layer 6 are sequentially provided on a transparent support 1, and the transparent support 1
A primer layer 5 and a silicone rubber or silicone resin layer 3 are sequentially provided underneath. In this case, the transparent support, the heat-sensitive layer and the silicone rubber or the silicone resin layer are essential constituents of the present invention, but the under layer, the protective layer and the primer layer are optional constituents and may be optionally provided.

Each of the above layers will be described in detail.

As the support, a plastic film that causes a sticking phenomenon by contact heating with a thermal head that generates a surface temperature of about 300 ° C. for a heating pulse width of several ms, that is, polyesters such as polyethylene terephthalate, polystyrene, polyvinyl chloride and copolymers thereof, A thermoplastic resin such as polymethacrylate and its copolymer, polyethylene or polyamide is used to form a transparent film.

The film thickness usually used is 5 to 100 μm, preferably 10 to 50 μm.

As the silicone rubber, a heat-curable silicone rubber can be used, but a room-temperature-curable silicone rubber is more preferred, and is represented by a one-pack type silicone rubber obtained by curing a reactive polysiloxane and a diorganopolysiloxane having a functional group at the end. A base polymer obtained by curing the base polymer with a curing agent is used. Condensation reaction type resins, addition reaction type resins, and peroxide curing reaction type resins are known as silicone resins, but any of them may be used.

The heat-sensitive layer includes a combination of [I] a leuco dye and a developer and a combination of [II] a higher fatty acid metal salt and a reducing agent.

The details of each material are as follows.

[I] Thermosensitive Layer Combining Leuco Dye and Developer A color former is mainly used, and a binder, a sensitizer such as fatty acid amide, an oil-absorbing white pigment, a lubricant such as a higher fatty acid metal salt, and an antioxidant are appropriately used. Composed of blended materials.

<Leuco dye> Crystal violet lactone, 3-
Indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 3-diethylamino-5-methyl-7-
t-Butylfluorane, 3-buethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6
-Methyl-7-p-butylanilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane,
3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-piperidino-6-methyl-7-toluidinofluorane, 3-pyrrolidino-6-methyl- 7- (p-toluidino) fluorane, 3-piperidino-6-methyl-
7-anilinofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-
Diethylamino-7- (n-trifluoromethylanilino) funouran 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylaminophthalide) and the like.

<Developer (acidic substance)> 4-phenylphenol, 4-
t-butylphenol, 4-hydroxyacetophenone, α-naphthol, β-naphthol, 2,2′-dihydroxydiphenyl, 2,2′-methylenebis (4-chlorophenol), 2,2′-methylenebis (4-methyl-6) -T-butylphenol), methyl-4-hygroxybenzoate, benzyl-4-hydroxybenzoate, 4,4'-isopropylidene bis (2-methylphenol), 4,4'-ethylenebis (2-methylphenol), 1,1′-bis (4′-hydroxyphenyl) -cyclohexane, 4,4′-isopropylidenediphenol, 4,4′-cyclohexylidenebis (2-isopropylphenol), novolac type phenol resin, 3-5 Di-α-methylbenzyl salicylic acid, 4-
Hydroxybenzoic acid esters <Binder> Casein, gelatin, styrene-maleic anhydride copolymer, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer Combined, polyacrylic amide, modified polyacrylic amide, carboxymethyl cellulose, polyvinyl acetate, polystyrene, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer and the like.

<Sensitizers> stearic acid amide, palmitic acid amide, oleic acid amide, lauric acid amide, ethylene bis stearoamide, methylene bis stearoamide, methylol stearoamide, paraffin wax, etc., with higher alcohols and higher resins Acid or the like may be added.

<Oil absorbing white pigment> Inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax stone, kaolin, aluminum hydroxide and calcined kaolin, and organic pigments such as urea formalin resin and polyethylene powder. Used.

[II] Heat sensitive layer in which higher fatty acid metal salt and reducing agent are combined An example of the combination of both in this case is shown below Primer layer: a surface treatment agent which is applied to the surface of an adherend in advance in order to improve the adhesion between a room temperature-curable silicone rubber or resin and a support, and is used as a film-forming agent, silane coupling agent, solvent, It is a catalyst, a pigment and other additives, and is effective for improving the above-mentioned adhesion by evaporating a solvent, hydrolysis and condensation, and forming an adhesive film after being applied to the surface of an adherend. Instead of this primer, the surface of the support may be subjected to corona discharge treatment.

Protective layer: A coating film, which is not essential to the invention, consisting of a water-soluble polymer binder and an inorganic or organic pigment, is applied on the heat-sensitive layer to protect the surface of the heat-sensitive layer. As the water-soluble polymer binder, polyvinyl alcohol, methyl cellulose,
Examples thereof include starch, carboxymethyl cellulose, styrene-maleic acid copolymer, polyamide resin, polyacrylamide resin, diisobutylene-maleic acid copolymer and the like. As the pigment added to this, inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, calcined kaolin, and aluminum hydroxide, urea formalin resins, and organic pigments of polyethylene powder are used.

The coating amount (dry weight) of the protective layer is 0.2 to 3.0 g / m ^2, preferably 0.5 to 3 g / m ² , and a low coating amount has a function of preventing fusion of the thermal head and physical protection from the outside. The properties such as the function to perform are insufficient, and the thermal reactivity of thermal coloring is deteriorated at a large coating amount.

The under layer can be omitted because it can maintain the adhesiveness with the heat-sensitive layer by performing corona discharge treatment on the surface of the support, but it can be applied uniformly on the support film, and a material with strong adhesive force can be used. To be selected. Further, a dissolved substance can be absorbed during recording, and an oil-absorbing white pigment and a synthetic rubber or a latex binder such as vinyl acetate, a copolymer of styrene maleic anhydride, polyvinyl alcohol and the like are used.

(Operation) The thermosensitive recording medium of the present invention has the constitution as shown in FIG. 1 or FIG. 2, and even if a general-purpose thermoplastic resin which normally causes sticking is used as the transparent support 1. As a result of being protected by the heat-resistant silicone rubber or the silicone resin layer 3 provided on the back surface thereof, recording from both upper and lower surfaces without sticking,
Reading can be achieved.

This state will be described with reference to FIG. 3. FIG. 3 shows a case where a recorded image 7 is formed on the thermosensitive recording layer 2 and the relationship between the recording directions H ₁ and H ₂ and the reading R ₁ and R ₂ of the recorded image 7. The following four methods are possible.

Recording H ₁ from the back side and reading from the back side (R ₁ ) Recording from the back side (H ₁ ) and reading from the front side of the thermosensitive layer 2
(R ₂ ) Recording (H ₂ ) from the surface side of the thermosensitive layer 2 and reading from the back side (R ₁ ) Recording (H ₂ ) from the surface side of the thermosensitive layer 2 and reading from the surface side. (R ₂ ) ... (Similar to the conventional technique) (Example) The present invention will be described below with reference to examples.
However, all parts are parts by weight.

Example 1 [Liquid A] 3-N-methylcyclohexylamino-6-methyl-
6-Methyl-7-anilinofluorane ... 10 parts ○ Polyvinyl alcohol (10% aqueous solution) ... 10 parts ○ Water ... 10 parts [solution B] ○ Bisphenol A ... 20 parts ○ Calcium carbonate ... 20 parts ○ Polyvinyl alcohol ... 10 Parts (10% aqueous solution) O Water ... 50 parts The above-mentioned solutions A and B were dispersed in a ball mill for 24 hours, and then the following formulation was used to prepare a thermosensitive coloring layer coating material.

These were uniformly mixed and applied on the surface of a polyethylene terephthalate film having a thickness of 25 μm so that the solid content was 5.0 g / m ² and dried to form a heat-sensitive layer.

[C liquid]

The above composition was dispersed by a ball mill, and the resulting C liquid was added to 3
Parts, polyvinyl alcohol (10% aqueous solution) 70 parts, polyamide resin 5 parts, and fatty acid metal salt (20% suspension) 2 parts were mixed to prepare a protective layer coating material.

The protective layer coating material was applied on the heat-sensitive layer in an amount of 5 g of solid component adhered /
It was applied to m ² and dried.

Next, on the back surface of the support, room temperature curable silicone rubber (product name PRX305 manufactured by Toray Silicone Co., Ltd.) solid content 30%
Was diluted to a solid content of 5% with n-hexane to prepare a coating material for the back surface treatment layer. This coating material was applied to a thickness of 15 μm to obtain a thermosensitive recording medium of the present invention.

This thermal recording material was applied to a commercially available thermal printer (Bar code printer BP-70 manufactured by Teraoka Seiko Co., Ltd.)
That is, when recording was performed from the silicone rubber coated surface side, a clear image having an image density of 1.3 could be read from the back surface side by a Macbeth reflection densitometer without causing a sticking phenomenon.

The heat-sensitive recording material of the present invention can of course obtain a clear recorded image even from the surface side of the heat-sensitive layer.

Example 2 A coating obtained by diluting a room temperature curable silicone resin (Toray Silicone Co., Ltd., trade name SR2411, solid content 20%) with n-hexane to a solid content of 5% to provide a back surface treatment layer to be used on the back surface of the support. A thermosensitive recording medium of the present invention was obtained in the same manner as in Example 1 except that the above was used.

Using a commercially available thermal printer (Barcode Printer BP-70 manufactured by Teraoka Seiko Co., Ltd.) for the obtained thermal recording medium,
When recording was performed from the rear side, a sticking phenomenon did not occur, and a clear recorded image with an image density of 1.43 could be read from the rear side.

Comparative Example 1 When the recording was performed using a thermal head from the back side of the support without the back side treatment layer of silicone rubber shown in Example 1, sticking occurred on the support layer and recording could not be performed.

Comparative Example 2 A thermal recording medium for comparison was prepared in the same manner as in Example 1 except that silicone oil was used in place of the silicone rubber of the thermal recording medium shown in Example 1. When the obtained comparative thermal recording medium was continuously recorded with a commercially available thermal printer, the oil migrated to the thermal head due to insufficient adhesion between the silicone oil and the support, and the head was contaminated. However, the sticking phenomenon of the support resin gradually occurred with continuous use, which was a serious problem in practical use.

(Effects of the Invention) According to the present invention, the back surface of the support is provided by providing the back surface of the support with a back treatment layer made of silicone rubber or silicone resin having a higher softening point than the thermoplastic resin forming the support. Can be recorded without any hindrance.

As a result, the present invention produces the following effects.

Recording from both the heat-sensitive layer side and the back surface became possible.

Even if the surface of the heat-sensitive layer has a low smoothness, or contains a substance that destroys the thermal head, it can be used by recording it from the back surface.

The lift wear of the recorder can be the same as before.

Since the record can be read from the back side of the support, when it is used as a label, the support also acts as a protective layer, it is hard to erase the record against oil, water, etc., various effects such as scratches and indentations It plays.

Since the thermal recording material of the present invention has the effects as described above, when used as a label for courier etc., there is no need for a film cover on the label, and after the recorded image such as a drawing is put out by a thermal plotter, It is possible to collate them by superimposing them, which has the effect of expanding its application.

[Brief description of drawings]

1 and 2 are sectional views showing an embodiment of the present invention.
The drawings are illustrations of the recording and reading functions of the thermosensitive recording medium according to the present invention. 1: transparent support 2: heat sensitive layer 3: silicone rubber or silicone resin layer 4: under layer 5: primer layer 6: protective layer

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a transparent support made of a transparent thermoplastic resin, a heat-sensitive layer provided on the surface, and a backside treatment layer made of silicone rubber or silicone resin on the backside.