JPH01196393A - Electrothermal transfer recording medium - Google Patents

Abstract

PURPOSE:To impact flame resistance to the title medium without enhancing the electric resistance of a resistor layer, by using a polyvinyl butyral resin as a binder for the resistor layer, and using an inorganic metallic compound flame retarder. CONSTITUTION:A resistor layer is provided by using a polyvinyl butyral resin as a binder and mixing it with a conductive powder, e.g., carbon black, and an inorganic metallic compound used as a flame retarder. It is preferable that the polyvinyl butyral resin has a medium or high polymerization degree, from the viewpoint of film-forming ability, heat resistance or the like. The conductive powder is preferably a powder of the material generally called conductive carbon. The inorganic metallic oxide flame retarder may be, for example, antimony trioxide or magnesium hydroxide. By this, it is possible to obtain an electrothermal transfer recording medium to be fire retardant without enhancing the electric resistance of the resistor layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording medium for electrical transfer. More specifically, the recording medium and the receptor are stacked, the recording electrode needle and the return electrode are brought into contact with the recording medium, and a signal voltage is applied between the two to energize the recording medium and generate heat, thereby removing the colored components of the recording medium. The present invention relates to a recording medium used in an electric transfer recording method that performs recording by transferring onto a receptor.

[Conventional technology]

Some such recording media for electrical transfer have a structure in which a resistance layer is provided on one side of an insulating base film and a thermal transfer ink layer is provided on the other side.The base film is a polyester film, and the resistance layer is made of polyester resin or the like. It is known to use a binder in which conductive powder such as carbon black is dispersed.

[Problem that the invention attempts to solve]

In the case of recording media used in the current transfer recording method, there is a risk of fire since electricity is applied to generate heat, so flame retardancy is required like electronic components.

However, the conventional recording medium has low flame retardance and cannot pass the UL-9411B standard, for example.

Therefore, it is possible to make the resistance layer flame retardant by adding a flame retardant, but for example, if a phosphorus-based or halogen-based flame retardant is mixed with the polyester resin used in the conventional resistance layer, the resistance value will increase. There are other problems. If the resistance value becomes large, the applied voltage must be increased, which causes problems with the apparatus and also makes it difficult to produce density gradations when printing a multi-gradation image, which is not desirable.

In view of the above points, the present invention provides a recording medium for electrical transfer that is made flame retardant without increasing the resistance value.

[Means to solve the problem]

The present invention relates to a recording medium for electrical transfer, in which the electrical resistance layer is composed of a binder containing polyvinyl butyral resin as a main component, a conductive powder such as carbon black, and an inorganic metal compound flame retardant.

[For production]

By using polyvinyl butyral resin as the binder of the resistance layer and using an inorganic metal compound flame retardant as the flame retardant, flame retardation can be achieved without increasing the resistance value of the resistance layer.

〔Example〕

Next, a case will be described in which the present invention is applied to a recording medium for electrical transfer having a structure in which a resistance layer is provided on one side of a base film and a thermal transfer ink layer is provided on the other side, but as will be described later, the present invention is not limited to this. It's not a thing.

The resistance layer in the present invention uses polyvinyl butyral resin as a binder, and mixes conductive powder such as carbon black and an inorganic metal compound as a flame retardant.

As the polyvinyl butyral resin, general polyvinyl butyral resins can be used without particular restrictions, but those with a medium to high degree of polymerization are preferred from the viewpoint of film-forming ability, heat resistance, etc.

In addition to polyvinyl butyral resin, other resins such as styrene resins such as polystyrene, acrylic resins such as polymethyl methacrylate, and vinyl chloride resins such as polyvinyl chloride may be used within a range that does not impair the purpose of the present invention. A small amount of these may be used together.

As the conductive powder, what is generally called conductive carbon is preferably used. Examples of the conductive carbon include Palkan XC-72R.

Palkan XC-72, Palkan P, Black Pearls 2
000 (both manufactured by Cabot Corporation), Ketchen Black EC (manufactured by Akzo Corporation), etc.

Examples of inorganic metal compound flame retardants include antimony dioxide and magnesium hydroxide. In addition to the inorganic metal compound flame retardant, other flame retardants such as tetrabromobisphenol A1 decabromodiphenyl oxide, halogen-containing condensed organic phosphoric acid ester, bromine-containing epoxy compound, etc. may be used within a range that does not impair the purpose of the present invention. A small amount of phosphorus-based or halogen-based flame retardants may be used in combination.

The ratio of the polyvinyl butyral resin and the conductive powder in the resistance layer is preferably in the range of 7=3 to 1:1 in terms of capacity ratio. If the proportion of the conductive powder is more than the above range, the resistance value will be too low and the adhesion to the base film will be reduced, which is undesirable, and if it is less than the above range, the resistance value will be too high, which is not preferable.

The content of the flame retardant in the resistance layer is preferably about 10-30% by weight. If the content of the flame retardant is less than the above range, flame retardancy will not be sufficient, while if it is more than the above range, film properties will deteriorate, which is not preferable.

In the present invention, a crosslinking agent may be added to crosslink the polyvinyl butyral resin in order to improve the heat resistance of the resistance layer. Any crosslinking agent that can react with the hydroxyl groups of the polyvinyl butyral resin can be used as such a crosslinking agent, such as polyisocyanate.

The resistance value of the resistance layer is preferably in the range of 0.5 to 2 Ω/cm, with <0.5 to 1 kΩ/cm. If the resistance value is higher than the above range, the applied voltage will become too high, making it difficult to achieve gradation, while if it is lower, the current density will increase, which is not preferable.

In order to achieve the above resistance value, the content of the conductive powder in the resistance layer is about 30 to 50 2% by volume.

The thickness of the resistive layer is preferably about 1 to 5 times in order to generate the required amount of heat and prevent heat diffusion in the surface direction of the recording medium.

As the base film, plastic films used in general thermal transfer recording media can be used without particular restrictions, such as polyester films, polypropylene films, polycarbonate films, etc. with a thickness of 3 to 1 mm.
Approximately 2 portions are used. In terms of heat resistance, strength, etc., polyester films are particularly preferred.

In the present invention, an undercoat layer may be formed to improve the adhesion of the resistance layer to the base film. As the main component of such an undercoat layer, polyester resin (preferably urethane type, polyester type, etc.), resins such as polyurethane resin, coupling agents such as alkoxysilane, etc. are used. Specifically, Byron 50AS (polyester resin manufactured by Toyobo ■),
Byron 29SS (polyester resin manufactured by Himyobo ■),
Nisvel 1520 (polyester resin manufactured by Hitachi Chemical Co., Ltd.), PIE-307 (polyester resin manufactured by Gutdeyer Co., Ltd.), Sunbren TCM350 (Sanyo Chemical Co., Ltd.': L
Polyurethane resin manufactured by Mari>, sp-2200 (silicone urethane resin +1) f), Sl coat 900A (
alkoxysilane), PIE-5833 (polyester resin), Bess Resin S-230G (polyester resin manufactured by Takamatsu Yushi ■), etc. These undercoating agents exhibit particularly excellent adhesion-improving effects when the base film is a polyester film.

The thickness of the undercoat layer is 0.2 to 0.0 mm from the viewpoint of adhesion.
Approximately 6 g/rn' is appropriate.

Moreover, a polyester film which has been previously processed to make it easy to touch is also preferably used.

The above-mentioned easy-to-adhesion treatment includes, for example, reacting a component (A) consisting of an aqueous polyurethane resin and an aqueous acrylic resin, at least one of which has a carboxylic acid group or its base, with a component of (B) an aqueous epoxy resin. Examples include those with a primer layer. The carboxylic acid group or its base in component A is capable of reacting with the epoxy group in component B.

This aqueous polyurethane resin preferably has increased affinity for water with a carboxylic acid group or its base,
Such water affinity-imparting groups are usually introduced during or after polyurethane synthesis. Introduction of a carboxylic acid group or its base can be carried out, for example, by using a carboxylic acid group-containing polyhydroxy compound as one of the raw material polyhydroxy compounds during polyurethane synthesis, or by introducing a hydroxyl group-containing carboxylic acid into the isocyanate group of a polyurethane having unreacted isocyanate groups. This can be carried out by reacting a carboxylic acid or an amino group-containing carboxylic acid, and then adding the reaction product to water or an aqueous alkali solution under high-speed stirring to neutralize it. The amount of carboxylic acid group or its base to be introduced is 0.1 to 15% by weight.
is preferred.

Further, in order to improve water dispersibility, in addition to the carboxylic acid group and its base, a sulfonic acid group or a sulfuric acid half ester group may be introduced into the polyurethane resin.

Examples of polyhydroxy compounds used in the synthesis of aqueous polyurethane resins include polyethylene glycol, polypropylene brecol, polyethylene propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 5-pentadiol, diethylene glycol, l- Examples include diethylene glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, glycerin, etc. . Examples of the polyisocyanate compound include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylolpropane, and an adduct of hexamethylene diisocyanate and trimethylolethane. Examples of the carboxylic acid-containing polyol include dimethylolpropionic acid, dimethylolbutyric acid, dimethylolyoshiwara acid, and trimellitic acid bis(ethylene glycol) ester. Examples of the amino group-containing carboxylic acid include β-aminopropionic acid, γ-aminobutyric acid, and p-aminobenzoic acid. Examples of the hydroxyl group-containing carboxylic acid include 3-hydroxypropionic acid, γ-hydroxybutyric acid, p-(2-hydroxyethyl)benzoic acid, and malic acid.

Aqueous polyurethane resins can be synthesized using these compounds by conventionally well-known methods. Further, such aqueous polyurethane resin can be formed into a stable aqueous dispersion or aqueous solution by using a dispersion aid if desired.

In addition, water-based acrylic resins (preferably those having a carboxylic acid group or its base; such a water affinity-imparting group is usually obtained by copolymerizing a monomer containing a carboxylic acid group or its base with a part of the polymerization component of the acrylic). For example, such carboxylic acid groups can be introduced with carboxylic acid-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc., or with alkyl monomers such as itaconic acid, maleic acid, fumaric acid, etc. The same size can be obtained by copolymerizing one or more monoester monomers with other vinyl compounds.Also, the introduction of carboxylic acid groups can be achieved by, for example, metal salts, ammonium salts, or tertiary amine groups of the monomers. This can be carried out by copolymerization, or by neutralizing with an alkaline aqueous solution after the synthesis of the resin or after the synthesis of the maleic anhydride and itaconic anhydride copolymer resin.The amount of the carboxylic acid group or its base to be introduced is 0.1 ~15% by weight is preferred.

Other vinyl monomers copolymerizable with the above monomers include, for example, alkyl acrylates or methacrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t- butyl group, 2-ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); Natural monomers; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N, N
-dimethylol acrylamide, N-methylol methacrylamide, N-methoxymethyl acrylamide, N-
Amide group-containing monomers such as methoxymethyl methacrylamide and N-phenylacrylamide; amino group-containing monomers such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate:
glycidyl acrylate, glycidyl methacrylate,
Epoxy group-containing monomers such as allyl glycidyl ether; monomers containing sulfonic acid groups or their salts such as styrene sulfonic acid, vinyl sulfonic acid, or their salts (sodium salt, potassium salt, ammonium salt, etc.); other vinyl Isocyanate Examples include allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, acrylonitrile, methacrylate trile, vinylidene chloride, vinyl acetate, and vinyl chloride.

The ratio of water-based polyurethane resin to water-based acrylic resin is 10:1 to 1:10, and 10:1 to 1.
:1, particularly preferably in the range of 4=1 to 1.1:1. The amount of carboxylic acid group or base introduced into the aqueous polyurethane resin and/or aqueous acrylic resin is 0.1 to 15% by weight, based on the total amount of the aqueous polyurethane resin and aqueous acrylic resin. Preferably, it is 0.1 to 5% by weight.

The carboxylic acid group or its base is preferably a carboxylic acid group or its amine base from the viewpoint of crosslinking reactivity with epoxy.

The aqueous epoxy resin as the B component to be reacted with the A component described above preferably has two or more epoxy groups, for example, H2Br υ
Uυ (where m = 1 to 3) (where m = 1 to 13) (where n = 1 to 13) C) Water-soluble or water-dispersible epoxy such as 12-011 H3 and addition condensate of bisphenol A with epichlorohydrin Compounds can be mentioned.

The aqueous brimer coating liquid consisting of components A and B may be an aqueous solution or an aqueous dispersion, and is not particularly limited. The ratio of A component and B component in the coating solution is such that B component is 1 to 4% of the sum of A component and B component (solid content).
Preferably, it accounts for 0% by weight.

As the thermal transfer ink layer used in the present invention, conventional types such as a thermal melt transfer type and a thermal sublimation transfer type are used.As a thermal melt transfer type, for example, waxes and/or resins are used as the main components of the vehicle. Colorants containing various pigments and dyes are used as appropriate. The ink layer may be of a single color, or a plurality of ink layers of different colors (eg, yellow, cyan, magenta, etc.) may be juxtaposed on the same base film. The coating amount of the ink layer is 0.5 to lOg/rr? A certain amount is enough.

Note that a conductive layer (low electrical resistance) such as a metal vapor deposited layer may be provided on one side of the base film, and a resistive layer may be provided thereon.

In addition, conventional recording media include those in which the recording medium is composed only of a resistive layer, and the resistive layer itself has a melt transfer function or an R flower transfer function to transfer the colored components contained in the resistive layer to a receptor. It is effectively used as a resistance layer in various known electrical transfer recording media.

Next, the present invention will be explained with reference to Examples.

Examples 1-2 Thickness 3.5 8 Adhesive processed polyester film (Teijin ■ single-sided easily adhesive processed polyester film, C3P)
35 parts by weight of polyvinyl butyral resin (Sekisui Chemical Oki Esle Tsuku B ll-3, W polymerization degree type, butyral foundation QG5 ± 3 mol%, acetyl group content 3 mol% or less) on the easily adhesive processed surface of 35 parts by weight of conductive carbon (EC), 25 parts by weight of antimony trioxide (Polysafe 60, manufactured by Ajinomoto), and parts by weight of polyisocyanate (Coronet 1-11L) Sffl.
Apply a coating solution dissolved and dispersed in a solvent such as toluene, volatilize the solvent, heat at 90°C for 10 seconds, and dry the coating amount: 2.4 g/n? A resistive layer was formed. Then, an ink containing wax, resin, and carbon black as main components and having a melting point of 80° C. was hot-melt coated on the opposite side of the film to form a heat-melt transfer ink layer having a thickness of 2 terms.

Example 2 A recording medium for electrical transfer was produced in the same manner as in Example 1 except that magnesium hydroxide (Kisma 5B, manufactured by Kyowa Chemical Industry Co., Ltd.) was used instead of antimony trioxide.

The resistivity of the resistive layer (kΩ/c
m) was measured and flame retardancy (UL-9411B) was investigated. The resistivity was determined as M1 using a resistance meter (Uresta PP manufactured by Mitsubishi Yuka ■).

The results are shown in Table 1.

Table 1: Polyvinyl butyral resin (Product name: Sletsku BM)
-8 (manufactured by Block Chemical Industry ■, medium polymerization degree type, butyral group content 70 mol% or more, acetyl group content 4-6 mol%)
Alternatively, when the product under the trade name S-LocBMS was used, the same excellent results as in the above example were obtained.

〔Effect of the invention〕

In a recording medium for electrical transfer, flame retardancy can be achieved without increasing the resistivity of the resistive layer, and clear printing can be performed without any danger.

Claims (1)

[Claims] 1. A recording medium for electrical transfer, wherein the electrical resistance layer is comprised of a binder containing polyvinyl butyral resin as a main component, conductive powder, and an inorganic metal compound flame retardant.