JPH01196392A - Electrothermal transfer recording medium - Google Patents

Abstract

PURPOSE:To prevent a lowering in resistance or releasing of a resistor layer from occurring, by using a polyvinyl butyral resin as a binder for the resistor layer, and interposing an undercoat layer between the resistor layer and the base film so as to improve the adhesion between the resistor layer and the base film. CONSTITUTION:An electrothermal transfer recording medium comprises a resistor layer on one side of a base film, and a thermal transfer ink layer on the other side. In the recording medium, the resistor layer comprises a binder, comprising a polyvinyl butyral resin as a main constituent, and a conductive powder such as carbon black, and an undercoat layer having favorable adhesives is provided between the resistor layer and the base film. A polyester resin, a coupling agent (e.g., alkoxysilane) or the like is used as a main constituent of the undercoat layer. This ensures that the content of the conductive powder such as carbon black can be increased, and the powder can be dispersed favorably. Therefore, the resistance of the resistor layer can be set to a lower value of not more than 2kOMEGA/cm, and the problems such as releasing of the resistor layer at the time of recording will not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] 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.

[Prior Art] There is a recording medium for electrical transfer that has a structure in which a resistive layer is provided on one side of an insulating base film and a heat-melting transfer ink layer is provided on the other side, and the base film is a polyester film. It is known to use, as a resistance layer, a material in which conductive powder such as carbon black is dispersed in a binder such as polyester resin.

[Issue to be solved by the invention] However, in the conventional recording medium, the dispersibility of conductive powder such as carbon black is poor, and the amount of the conductive powder cannot be increased (up to about 30% capacity), so the resistance layer is The resistance value could not be lowered, and for this reason, conventionally only a high resistance value of 2Ω4 or more could be obtained.

If the resistance value of the resistive layer is too high, the applied voltage must be increased, which causes problems with the device and also makes it difficult to produce density gradations when printing a multi-gradation image.

To solve this problem, the content of conductive powder such as carbon black can be increased by using polyvinyl butyral resin as a binder, but the polyvinyl butyral resin layer has poor adhesion with base films such as polyester films. Unfortunately, new gaps such as peeling occurred due to the sliding movement of the recording electrode needle during current recording.

In view of the above points, the present invention provides a recording medium for electrical transfer in which the resistance layer has low resistance and good adhesion to the base film.

[Means for Solving the Problems] The present invention provides a recording medium for electrical transfer comprising a base film having a resistive layer on one side and a thermal transfer ink layer on the other side, wherein the resistive layer is mainly made of polyvinyl butyral resin. 1. A recording medium for electrical transfer, comprising a binder and a conductive powder such as carbon black, and having an undercoat layer with good adhesion interposed between the resistive layer and the base film. Regarding.

[Function] By using polyvinyl butyl resin as a binder for the resistance layer, a good dispersion state can be maintained even if the content of conductive powder such as carbon black is increased (for example, from 30% to 50% by volume). Therefore, the resistance value can be reduced to a low value of 2KJ' or less,
Furthermore, since an undercoat layer with good adhesion was interposed between the resistive layer and the base film, problems such as peeling of the resistive layer during recording did not occur.

[Example] The resistance layer in the present invention uses polyvinyl butyral resin as a binder, and mixes conductive powder such as carbon black with it.

As the polyvinyl butyl resin, general polyvinyl butyl resins can be used without any particular restrictions, but polyvinyl butyl resins having a medium to high degree of polymerization are preferred from the viewpoint of film-forming ability, heat resistance, and the like.

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

As the conductive powder, what is generally called conductive carbon is preferably used. Examples of conductive carbon include Palkan xC-72R1 Palkan XC-72
, Palkan P1 Black Pearls 2000 (all manufactured by Cabot), and Ketchen Black EC (manufactured by Akzo).

In the present invention, by using polyvinyl butyral resin as a binder, the content of conductive powder such as conductive carbon in the resistance layer can be increased in a well-dispersed state, so that the resistance value of the resistance layer can be reduced to about IKΩ4 or less. It can be lowered to

Note that the lower limit of the resistance value of the resistance layer is preferably about 0.5 to 6 Ω so that the current density does not become excessively large.

Therefore, the resistance value of the resistance layer is preferably in the range of 0.5 to 2KQ4', particularly 0.5 to IKΩ4.

In order to achieve the above resistance value, the content of the conductive powder in the resistance layer is about 30 to 508 m%.

The ratio of the polyvinyl butyral resin to the conductive powder is preferably in the range of 7:3 to 1:1 in terms of volume 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. If it is less than the above range, the resistance value will be too high, which is not preferable.

In the present invention, a flame retardant may be added to make the resistance layer flame retardant. Examples of such flame retardants include inorganic metal compound flame retardants such as antimony trioxide and magnesium hydroxide, phosphorus-based flame retardants such as tetrabromobisphenol A1 decabromodiphenyl oxide, halogen-containing condensed organic phosphoric acid esters, and bromine-containing epoxy compounds; Halogen flame retardants can be used. The inorganic metal compound flame retardant is preferable because it can provide flame retardancy without increasing the resistance value. If a flame retardant is added, the content in the resistance layer should be 1O~30
It is said to be about % by weight.

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 group of the polyvinyl butyral resin can be used as such a crosslinking agent, such as polyisocyanate.

The thickness of the resistive layer is preferably about 1 to 5 times thick from the viewpoint of generating the required heat and preventing 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, ilm, etc. with a thickness of 3 to 1 mm.
2t! A diameter of about m is used. In terms of heat resistance, strength, etc., polyester films are particularly preferred.

In the present invention, the main ingredients of the undercoat layer used to improve the adhesion of the resistance layer to the base film include polyester resins (preferably urethane-based, polyester-based, etc.), resins such as polyurethane resins, and cups such as alkoxysilanes. A ring agent or the like is used. 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 6g4 is appropriate. Typically, the resins are in a relatively thick range within this range (eg, 0.4-0.6 g'm) and the coupling agent is in a relatively thin range (eg, 0.6 g'm).
It is preferable to use 2 to 0.3 g4).

Moreover, a polyester film that has been previously subjected to an adhesion-facilitating process is also suitably 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 brimer 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 glycol, polyethylene propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1.5-pentadiol, diethylene glycol, Triethylene glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate,
Examples include trimethylolpropane, trimethylolethane, pentaerythritol, and glycerin. 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, the water-based acrylic resin preferably has a carboxylic acid group or its base, and 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. will be introduced in For example, such carboxylic acid groups include carboxylic acid-containing polymers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc., and alkyl monoester monomers such as itaconic acid, maleic acid, fumaric acid, etc. 1st type or 2F1! It is introduced by copolymerizing the above with other vinyl compounds. Further, the introduction of the carboxylic acid group can be carried out, for example, by copolymerizing a metal salt, ammonium salt, or tertiary amine group of the monomer, or by using an alkaline aqueous solution after synthesizing the resin or after synthesizing the maleic anhydride and itaconic anhydride copolymer resin. This can be done by neutralizing it. The amount of carboxylic acid group or its base to be introduced is preferably 0.1 to 15% by weight.

Other monomers copolymerizable with the above monomers include, for example, alkyl acrylates or methacrylates (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group). 2-ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); Monomer; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N,N-
Amide group-containing monomers such as dimethylolacrylamide, N-methylolmethacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-phenylacrylamide; N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate, etc. Amino group-containing monomers: Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether; Sulfonic acids such as styrene sulfonic acid, vinyl sulfonic acid or their salts (sodium salt, potassium salt, ammonium salt, etc.) Monomers containing a group or a salt thereof; other examples include vinyl isocyanate allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl tris alkoxysilane, acrylonitrile, methacrylatrile, vinylidene chloride, vinyl acetate, vinyl chloride and the like.

The ratio of the water-based polyurethane resin to the water-based acrylic resin is 10:1 to 1:10, and more preferably 10:1 to 1 by weight.
:1, especially 4:1-1. Preferably, it is in the range l:l. Then, the water-based polyurethane resin and/or
Alternatively, the amount of carboxylic acid group or basic base introduced into the aqueous acrylic resin is 0.1 to 15% by weight, or even 0.
．． Preferably, it is 1 to 5% by weight.

The carboxylic M 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, C) 12Br (on-1 to 3) (on-1 to 13) (on-1 to 13) (on-1 to 13) =1~13) CH2-011 C)13 110-CH2C112-0-C)+2-CI-CH2
\/ and water-soluble or water-dispersible epoxy compounds such as addition condensates of bisphenol A and epichlorohydrin.

As mentioned above, the aqueous primer coating liquid consisting of component 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).
07I! It is preferable that it accounts for W%.

As the thermal transfer ink layer used in the present invention, any conventional type such as a thermal melt transfer type or a thermal sublimation transfer type can be used. ,
Various pigments and dyes are used as tube coloring agents as appropriate.

The ink layer may be a single color, or several 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 may be about 0.5 to 10 gJ.

Note that a base film having a conductive layer (having extremely low resistance) such as a metal vapor deposited layer on one side may be used, and the undercoat layer and the resistance layer may be provided on the surface of this conductive layer.

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

Examples 1 to 14 An undercoat agent shown in Table 1 was applied on one side of a 3.5-thick polyethylene terephthalate film and dried to form an undercoat layer. S-Lec B 11
-3, high polymerization degree type, butyral foundation 65 ± 3 mol%, acetyl group content 3 mol% or less) 35 parts by weight, conductive carbon (Ketchen Blank EC) 35 parts by weight, antimony trioxide (Polysafe 60, Ajinomoto (manufactured by ■) 25 parts by weight and polyisocyanate (Coronet) 11L) 5
Apply a coating liquid in which the iffffi part is dissolved and dispersed in an appropriate amount of a solvent such as toluene, and after volatilizing the solvent,
After heating for 0 seconds and drying, a resistance layer having a coating weight of 2.4 g4 was formed. Then, on the opposite side of the film, a coating with a melting point of 80% containing wax, resin, and carbon black as main components is applied.
A hot-melt transfer ink layer having a thickness of 2 was formed by hot-melt coating the ink at .

Comparative Examples 1 to 2 In the above, electric transfer was performed in the same manner except that the resistance layer was formed directly on the polyethylene terephthalate film (Comparative Example 1) or directly on the film after aging at 50°C for 12 hours (Comparative Example 2). A recording medium was created for this purpose.

Resistivity of the resistive layer (KΩ4) for each recording medium obtained
and adhesion was examined. The resistivity is the resistivity needle (Mitsubishi Yuka ■
It was measured using Uresta pp (manufactured by Uresta pp).

Adhesion was examined by a peel test using adhesive tape.

(1) DI Standard Method An adhesive tape (Sco Sochimending Tape 810, manufactured by Sumitomo 3M ■) was pressure-bonded onto the anti-layer.

Adhesive area: 18mm x 50mm or more Crimp conditions: Crimp 5 times with Ito Shoji Roller N051, then hook a tension gauge to the reinforced part of the adhesive tape and pull it in the specified direction at a speed of about 2c+m/sec.
The ratio of the area of the peeled resistance layer to the area of the attached adhesive tape was investigated.

The evaluation criteria are as follows.

1 almost completely peeled off.

2 More than half of it has peeled off.

3 Less than half of the peeled off.

4 Slightly peeled off.

5 could hardly be peeled off.

6. It did not peel off at all.

In addition, if the peeled area in the above test is less than half, there is no practical problem.

The results are shown in Table 1.

Byron 50AS: Polyester resin manufactured by Toyobo ■
(Byron 29SS: Polyester resin Nispel 1520 manufactured by Toyobo ■ Polyester resin PE-307 manufactured by Hitachi Chemical ■ Polyester resin Sunbren TCM350 manufactured by Gutdeyer: Polyurethane resin 5P-2200 + silicone urethane resin S1 coat 9 manufactured by Sanyo Chemical ■
00A: Alkoxysilane jPE-5
833: Polyester resin PES Resin S-230G: Polyester resin manufactured by Takamatsu Yushi ■ CPS: Polyester film manufactured by Teijin ■ processed on one side for easy adhesion. In this case, a resistance layer was formed directly on the easily bonded surface.

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

[Effect of the invention] By using polyvinyl butyral resin as a binder for the resistance layer and interposing an undercoat layer between the resistance layer and the base film to improve the tightness between the two, the conductivity in the resistance layer is improved. The content of conductive powder such as carbon can increase the resistance value and lower the resistance value, and can perform good current transfer recording without causing problems such as peeling of the resistance layer.

Claims (1)

[Claims] 1 A recording medium for electrical transfer comprising a base film having a resistive layer on one side and a thermal transfer ink layer on the other side, the resistive layer comprising a binder containing polyvinyl butyral resin as a main component and conductive powder, A recording medium for electrical transfer, characterized in that an undercoat layer with good adhesion is interposed between the resistive layer and the base film.