JPH0732083Y2 - Thermal recording medium that can be kept secret - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a thermosensitive recording medium capable of keeping confidential information such that output information of a facsimile, a computer or the like is not known to a third party.

"Prior Art" Since thermal recording media are relatively inexpensive, and the recording equipment is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields. Has been done. Especially in the case of facsimiles, etc., the output information is often important, but it is recorded so that it can be seen by anyone, so it is suitable for outputting important, secret, or private information. Absent.

For the purpose of hiding information, it has been proposed to cover the secret information portion of the heat-sensitive recording layer with an opaque cover (Japanese Patent Laid-Open Nos. 61-248785 and 61-248784), but the cover has been proposed. And the recording layer are partially adhered, the surface of the cover is wavy and the recording device is not suitable, and the opacity (concealment) decreases when the thickness of the base material is reduced to maintain the recording sensitivity. Therefore, it is necessary to provide an opaque treatment such as providing a vapor deposition layer of aluminum or the like or providing an opaque coating layer, which increases the cost and the thickness of the opaque layer increases, resulting in a decrease in recording sensitivity. Cause If only a part of the cover is attached,
Since unevenness in the adhesiveness at the thermal head part occurs during recording,
There are problems such as variations in recording density and poor running properties.

"Problems to be Solved by the Invention" The present invention aims to provide a thermal recording medium which solves the above-mentioned problems so that the output information to the thermal recording medium by a printer or a facsimile is not known to a third party. It is what

"Means for Solving the Problem" The inventors of the present invention previously applied for a thermal recording medium using an opaque film having a transparent portion as a part of a concealing cover. As a result,
A thermosensitive recording medium having the following constitution was completed. That is, according to the present invention, in a heat-sensitive recording medium (1) capable of keeping secrets, in which a cover is provided on the recording layer of the heat-sensitive recording medium, the cover (2) is substantially the same size as the heat-sensitive recording body (3), A transparent or semi-transparent base material (4) is provided with a concealing layer (5) containing a heat-meltable substance as a main component, leaving a part thereof.
A heat-sensitive recording medium which can be kept secret, wherein the entire surface is adhered with a peelable adhesive so that the concealing layer and the recording layer (6) face each other.

[Operation] The concealment cover (2) used in the present invention has a part (9) for recording the address (8) on the transparent or semi-transparent substrate (4), and the concealment part (8) for the heat-melting substance. 10) is provided.

As the cover substrate (4), polyester, polycarbonate, polypropylene, polyethylene, polyimide,
Polyetherimide, aramid, cellophane, condenser paper, glassine paper and the like can be used, but a polyester film which is excellent in heat resistance and physical strength and is inexpensive is preferable. Also, the thinner the thickness, the better the recording sensitivity. Therefore, the thickness of 25 μm or less, preferably 10 μm or less can be used. Further, a thermal property modifier, a release agent, an antistatic agent, a conductive agent, a cross-linking agent, etc. are added to the inside of the coating layer and / or the cover substrate for the purpose of improving thermal conductivity, thermal stability and the like. Good.

Further, the base material may be provided with a transparency control layer (14) for the purpose of supplementing the hiding power of the heat-fusible substance so that the address and the like can be visually recognized and the recording sensitivity is not unnecessarily lowered.

In the present invention, the hiding layer (5) made of a heat-fusible substance means that the heat-fusible substance contains a colored colorant for hiding the recorded information (11) of the heat-sensitive recording layer (6) invisible. However, since it has an effect of efficiently transmitting the heat transmitted from the thermal head to the thermal recording layer during recording, high density recording can be performed.

Examples of the heat-fusible substance include higher fatty acids such as palmitic acid, threaric acid, and 12-hydroxystearic acid, fatty acid metal salts such as zinc stearate, and solid fatty acid esters such as myricyl cerotate, ceryl montanate, and myricyl stearate. Or their partially saponified products, solid fatty acid amides such as stearic acid amide, coconut oil fatty acid amide, higher alcohols, polyhydric alcohol esters, paraffin wax, microcrystalline wax, carnauba wax, montan wax, auri Natural waxes such as Curie wax, candelilla wax, wooden wax, rice wax, beeswax, so-called wax such as Fischer-Tropsch wax, polyethylene wax, oxidized wax, hydrogenated wax and other synthetic or modified waxes Polyolefins such as low molecular weight polypropylene and polybutylene, low molecular weight oxidized polyolefins, halogenated polyolefins, olefins or α-olefins and maleic anhydride, (meth) acrylic acid, (meth) acrylic acid esters, vinyl acetate Low molecular weight copolymer, (α-methyl) styrene resin, vinyltoluene resin, acrylic resin, polyamide resin,
Polyester resin, polyurethane resin, polyvinyl butyral resin, vinyl chloride-vinyl acetate copolymer, cellulose resin, phenol resin, rosin resin, petroleum resin, terpene resin, alicyclic resin, silicone resin, silicone modified Resins, so-called heat-meltable resins such as perfluoro group-containing low molecular weight resins, and the like can be mentioned.
It is used by selecting more than one species.

Examples of colored colorants include black dyes and pigments such as graphite, carbon black and oil black, yellow dyes, red dyes, blue dyes and other colored dyes, polymer dyes, polymer graft pigments, surface coating pigments, One or more kinds of dyes and pigments known for use in conventional printing inks such as dye-pigment-containing resin fine particles, recording, and other coloring applications are selected and used.

In the concealing layer with a heat-melting substance, if necessary, anionic, nonionic, cationic or amphoteric surfactants, dispersants, viscosity modifiers, softeners, plasticizers, gloss imparting agents, Various auxiliaries such as an antioxidant, a stabilizer, an antistatic agent and / or an antistatic agent, and a release agent may be appropriately added. Also,
As long as the characteristics of the present invention are not impaired, if necessary, fillers,
For example, it is also possible to add calcium carbonate, talc, kaolin, natural or synthetic silicic acids, titanium oxide, aluminum hydroxide, zinc oxide, plastic pigments.

The thermosensitive recording medium (3) comprises a thermosensitive recording layer (6) provided on a support (12) such as paper, synthetic paper, film or cloth.

Various combinations can be applied as the color-forming substance constituting the heat-sensitive recording layer (6), and specific examples thereof include the following.

(A) A compound having a secondary alcoholic hydroxyl group and a melting point of 100 to 180 ° C., which is described in JP-B-41-14510.
A combination consisting of sulfur and metal inorganic salts or metal acetates.

Examples of the compound having a secondary alcoholic hydroxyl group include benzoin compounds such as benzoin, 2-methoxybenzoin, 4-chlorobenzoin, 4-dimethylaminobenzoin, 2-chloro-4'-dimethylaminobenzoin, and diphenylcarbinol. Carbinols such as
Resorcin, pyrogallol, 3-hydroxytoluene-
Phenolic compounds such as 4-sulfonic acid, 4-nitroresorcin, 4,6-dibromoresorcin, and fatty acid polyhydric alcohols such as erythritol, sorbit, galactose, maltose, mannitol and saccharose. The metal inorganic salts and metal acetates include many of the metals that react with hydrogen sulfide to produce colored sulfides, such as copper, lead, tin, molybdenum, cobalt, chromium, nickel, manganese, Titanium,
There are antimony, rhodium, osmium, mercury, iron, barium, bismuth, arsenic, magnesium, indium, iridium and the like.

(B) A combination in which various inorganic metal salts in the composition of (a) described in JP-B-41-14511 are replaced with hexamethylenetetramine / metal salt adducts.

(C) A combination of a carbohydrate and a dehydrating agent described in JP-B-42-13237.

Here, as carbohydrates, sucrose, fructose,
Examples include galactose and starch, and examples of the dehydrating agent include sulfuric acid, acetic anhydride, anhydrous zinc chloride, and paratoluenesulfonic acid.

(D) Combination of long-chain fatty acid iron salts such as ferric stearate and ferric myristate with phenols such as tannic acid, gallic acid and ammonium salicylate.

(E) Organic acid heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury and silver salts such as acetic acid, stearic acid and palmitic acid, and alkaline earth metal sulfides such as calcium sulfide, strontium sulfide and barium sulfide. Or a combination of the organic acid heavy metal salt and an organic chelating agent such as S-diphenylcarbazide and diphenylcarbazone.

(F) A combination of a heavy metal oxalate such as an oxalate of silver, lead, mercury or thorium and a sulfur compound such as Na-tetrathionate, sodium thiosulfate or thiourea.

(G) ferric stearate such as ferric stearate and ferric salt of 3,4
In combination with an aromatic polyhydroxy compound such as dihydroxytetraphenylmethane.

(H) A combination of an organic acid noble metal salt such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin or glycol.

(I) A combination of an organic acid noble metal salt such as silver behenate and silver stearate and an aromatic organic reducing agent such as protocatechuic acid, spiroindane and hydroquinone.

(J) A combination of a ferric fatty acid salt such as ferric pelargonate and ferric lauric acid with a thiosemicarbazide or an isothiosemicarbazide derivative.

(K) A combination of an organic acid lead salt such as lead caproate, lead pelargonate or lead behenate and a thiourea derivative such as ethylene thiourea or N-dodecyl thiourea.

(L) A combination of a higher fatty acid heavy metal salt such as ferric stearate and copper stearate and zinc dialkyldithiocarbamate.

(M) A compound that forms an oxazine dye, such as a combination of resorcin and a nitroso compound, or a compound that forms an azo dye.

(N) What forms an azo dye, such as a combination of a diazonium salt and a coupler compound.

(O) A combination of a colorless or pale basic dye such as crystal violet lactone and a coloring agent such as bisphenol A.

Among the various combinations as described above, a thermal recording material using a combination of a basic dye and a color developing agent is general and often used.

The adhesive (7) used for adhering the heat-sensitive recording material (3) and the concealing cover (2) on the entire surface is polyvinyl alcohol, gum arabic, a sizing agent such as starch, polyvinyl acetate, ethylene-acetic acid. Vinyl copolymer, acrylic resin, styrene-vinyl acetate copolymer, natural rubber resin,
A dispersion emulsion type sizing agent such as a silicone resin can be used. In addition, waxes such as paraffin wax, microcrystalline wax, carnauba wax, silicone wax and the like can also be stuck.

This bonding is done until the thermal recording material reaches the recipient.
That is, it is necessary that the adhesive strength is such that it does not peel off during delivery or leaving by a third party, and that the recording layer does not transfer to the adhesive layer side so that the recipient can easily peel it off. Must be

If the adhesive strength is too strong when using resin-based sizing agents, inorganic pigments such as calcium carbonate, talc, kaolin, natural or synthetic silicic acid, titanium oxide, aluminum hydroxide, zinc oxide, urea-formaldehyde resin particles Adhesive strength can be reduced by adding extender pigments such as organic pigments such as polystyrene-based resin particles and silicone-based resin particles. If the adhesive strength is too weak when using waxes, etc. Adhesion may be performed while appropriately adjusting the adhesive force such as adding a sizing agent. It is also possible to provide a layer for controlling the adhesive force of the resin or pigment on the surface of the thermosensitive recording medium.

A non-adhesive portion may be provided on at least a part of the end of the recording body so that the recipient can easily open it, and it is impossible to intentionally remove the concealing cover. It is also possible to use such a strong adhesive as around the periphery of the recording material or at the edges. In this case, it is possible to make a perforation near the strong adhesive so that the adhesive can be separated.

In the present invention, when an overcoat layer (13) containing a resin as a main component is provided on the surface of the concealing cover (2), suitability for recording equipment such as running property of a recording medium is improved and heat resistance is further improved. preferable.

This overcoat layer (13) includes nitrocellulose, cellulose acetate, epoxy resin, melamine resin, phenol resin, polyimide resin, silicone resin, fluorine resin,
Formed from resins such as polysulfone resin, polycarbonate resin, polyvinyl alcohol, butyral resin, polyester resin, acrylic resin, and wax,
Lubricants such as talc, release agents such as silicone oil and silicone resin particles, phosphate ester-based surfactants, antistatic agents such as silicone-based surfactants, conductive agents such as carbon black and conductive titanium oxide, calcium carbonate Additives such as extender pigments such as boron nitride may be added as necessary.
It is also possible to use a substance that undergoes a crosslinking reaction such as isocyanates and a metal-based crosslinking agent, or a resin that cures with an electron beam or ultraviolet rays, for this layer.

The overcoat layer is a dry weight 2 g / m ² or less, preferably provided so as to be 0.05 to 1 g / m ² approximately.

In the present invention, the size, position, number, etc. of the transparent or translucent portions are not particularly limited. In the case of computer output recording, it is sufficient to program so that the destination is recorded in the transparent area. In the case of facsimile, use a display unit that matches the receiver's recording medium, transmission paper that can be recognized by the concealment unit, etc. do it.

The heat-sensitive recording medium which can be kept secret according to the present invention can be used after being processed into a shape suitable for a recording device or application such as a winding shape, a sheet shape, a printer foam shape.

[Examples] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples. or,
Unless otherwise specified, parts and% in the examples are "parts by weight".
And "% by weight".

Example Using a polyester film (thickness of 4.5 μm) as a support,
Commercially available gravure ink varnish for polyester 10
0.5 g / m ² dry weight of a coating solution for a transparency control layer prepared by adding 1 part of carbon black fine powder for coloring and 1 part of matting agent (amorphous silica fine powder) to 0 part was applied.
3g / m ² of hot-melt black ink for fax (carbon black, paraffin wax and ink of ethylene / vinyl acetate copolymer, melting point 68 ℃) was applied by hot-melt coating method. After providing the concealing layer, an overcoat layer composed of a runnability improver containing a heat resistant resin as a main component was provided at a dry weight of 0.3 g / m ² over the entire reaction surface of the support to obtain a concealing cover.

Next, 1 g / m ^{2 of} microcrystalline wax was coated on a commercially available thermosensitive recording paper, and the above-mentioned concealing cover was adhered under heat and pressure (50 ° C., linear pressure 2 kg / cm) to keep it secret. Got

Comparative Example A secret-sensitive heat-sensitive recording medium was obtained in the same manner as in Example except that 3 g / m ^{2 of} black gravure ink for polyester was applied instead of the heat-meltable black ink.

A thermal printer (head voltage 14
When recording was performed using V), it was a thermosensitive recording medium useful for keeping secret that the contents of the concealing portion could not be visually recognized unless the concealing cover was peeled off.

Further, when the recording densities of the both were compared, it was as shown in Table-1.

[Effect] The thermosensitive recording medium of the present invention is capable of keeping secret and is suitable for recording equipment, and as is clear from Table 1, is highly sensitive and suitable for high speed recording and low energy recording.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the layer structure of a thermosensitive recording medium as an example of the present invention, and FIG. 2 is a cross-sectional view showing the layer structure when an overcoat layer 13 and a transparency control layer 14 are provided. FIG. 3 and FIG. 4 are front views showing a state of recording on the recording medium. 1: Thermal recording medium capable of keeping confidential 2: Concealment cover 3: Thermal recording medium 4: Cover substrate, 5: Concealment layer 6: Thermal recording layer, 7: Adhesive layer 8: Address, 9: Display section 10 : Concealment section, 11: Confidential information 12: Support, 13: Overcoat layer 14: Transparency control layer

Claims (1)

[Scope of utility model registration request] 1. A heat-sensitive recording medium (1) capable of keeping secrets, wherein a cover is provided on the recording layer of the heat-sensitive recording medium, and the cover (2) is substantially the same size as the heat-sensitive recording medium (3). A transparent or semi-transparent base material (4) is provided with a concealing layer (5) containing a heat-meltable substance as a main component, leaving a part thereof.
A heat-sensitive recording medium which can be kept secret, wherein the entire surface is adhered using a peelable adhesive (7) so that the concealing layer and the recording layer (6) face each other.