JPH01174573A - Electrically conductive ink composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition useful for ink sheet of electrical heat transfer type, printable at high speed, containing a saturated polyester resin, carbon black, polyisocyanate, a specific epoxy resin, silicone resin and solvent in a specific ratio. CONSTITUTION:The aimed composition consisting of (A) 100pts.wt. saturated polyester resin (saturated polyester resin of modified ether type having preferably 15,000-25,000mol.wt.), (B) 20-50pts.wt., preferably 25-35pts.wt. carbon black (carbon black having preferably 20-100mum average particle diameter), (C) 10-40pts.wt., preferably 20-30pts.wt. polyisocyanate (e.g., tolylene diisocyanate), (D) 10-40pts.wt., preferably 15-30pts.wt. epoxy resin of bisphenol A type, (E) 1-10pts.wt. silicone resin and (F) 200-500pts., preferably 250-350 pts.wt. solvent (e.g., toluene).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a conductive ink composition, particularly a conductive ink composition useful for use in electrical thermal transfer type ink sheets.

(Prior Art) In recent years, the spread of information devices has been remarkable. In particular, with the spread of personal computers, office computers, and word processors, the number of printers installed and connected to these devices is rapidly increasing.

Against this background, thermal transfer printers use a method that prints by applying a predetermined amount of heat to an ink sheet and transferring the ink to recording paper.
It is characterized by low price and high reliability.

There are several methods for thermal transfer, but one that has recently attracted attention is one that uses an ultra-thin film made of synthetic resin as a base material and applies conductive ink through an aluminum vapor-deposited layer. There is a method called electrical thermal transfer that uses a sheet on which a transfer layer made of transfer ink is provided via a release layer. Transfer ink is made by adding carbon black to thermoplastic resin such as polyester resin or polycarbonate resin and dispersing it in an organic solvent such as toluene or methyl ethyl ketone (hereinafter abbreviated as MEK), or polyurethane resin, epoxy resin, etc. There is a composition in which carbon black is added to a curable resin and dispersed in an organic solvent, and the present inventors also developed a conductive ink composition for thermal transfer using a) 100 parts by weight of a saturated polyester resin, b) Carbon black 20-50 parts by weight, C) Polyisocyanate 10-40 parts
Parts by weight, d) Bisphenol A epoxy resin 10-4
0 parts by weight, e) 200 to 500 parts by weight of solvent, and showed that it could be used for electrical thermal transfer ribbons (see Japanese Patent Application No. 61-246894).
.

(Problems to be Solved by the Invention) However, in recent years, there has been a demand for higher printing speeds of printers, and this has resulted in several problems as described below.

First, the problems mainly caused by the conductive ink layer are l) print head wear due to friction between the print head and the ink ribbon, 2) heat resistance deterioration of the conductive ink layer due to rise in temperature at the application section, 3) 2) Sticking between the conductive ink layer and the print head occurs due to 4) 2) Adhesion of the conductive ink layer to the print head due to 3) and leakage between the print head and the print head due to this.

In addition, a material with a relatively low melting point is used for the J transfer ink layer, and the main problems caused by this are: 5) The ink sheet is not in a roll or laminated form for convenience of installation in the printer. Blocking between the transfer ink layer and the conductive ink layer due to the winding pressure generated by the transfer or its own weight, and 6) migration and peeling of the transfer ink to the conductive ink layer due to 5).

(Means for Solving the Problems) The present invention relates to a conductive ink composition that solves the above-mentioned problems, and comprises a) 100 parts by weight of a saturated polyester resin, and b) 20 to 50 parts by weight of carbon black.
Parts by weight, C) 10 to 40 parts by weight of polyisocyanate, d
) 10 to 40 parts by weight of bisphenol A epoxy resin,
e) 1 to 10 parts by weight of silicone resin, f) 200 to 200 parts of solvent
500 parts by weight.

That is, as a result of various studies conducted by the present inventors in order to solve the above-mentioned problems, the problems caused by both of the above-mentioned problems can be solved by improving heat resistance, lubricity, and mold releasability of the conductive ink layer. For this purpose, a conductive ink composition as shown above, which is obtained by adding a silicone resin to the conductive ink composition previously proposed by the present inventors, is used as a conductive ink composition. The present invention was completed by discovering that it is effective to use this method as a layer.

As the saturated polyester resin as component a) constituting the conductive ink composition of the present invention, for example, a modified ether type resin having a molecular weight of 15,000 to 25,000 represented by the following formula: Stafix P -LC (Fuji Photo Film Co., Ltd. mounting product name), Byron 2,000 (
Toyobo Co., Ltd. mounting product name], Elythyl L E-3,2
00 (Unitika Co., Ltd. equipment product name), etc.
Stafix P-LC is preferred from the viewpoint of fluidity and hardness.

Further, carbon black as component b) constituting the composition of the present invention is used to impart conductivity and heat generation properties to the target ink composition, and this carbon black is a carbon black that is used to impart conductivity and heat generation properties to the target ink composition. , Ketchen Black, etc. Although the particle size of this material is arbitrary, in order to make this ink composition have good carbon black dispersibility and fluidity, it is preferable that the average particle size is 20 to 100 μm. Note that the amount of carbon black added is preferably such that the target ink composition has an electrical conductivity of 0.5 to 10 Ω·cm, so 100 parts by weight of the saturated polyester resin as component a) described above. The preferred range is 25 to 35 parts by weight.

Next, the polyisocyanate as component C) constituting this composition is for converting the saturated polyester resin as component a) into a modified polyurethane resin, and includes tolylene diisocyanate (TDI) represented by the formula ) as 2.4-TDI, 2.8-TDI, 4,
Aromatic diisocyanates such as 4°-diphenylmethane diisocyanate (MDI), 1,6-hexamethylene diisocyanate (
Examples include aliphatic diisocyanates such as MDI, but they may also be mixtures of these, and commercially available products include Coronate L (Nippon Polyurethane Industries Co., Ltd.).
Examples include product name and part name. Note that if the amount of this polyisocyanate added is less than 10 parts by weight per 100 parts by weight of the saturated polyester resin as component a), the intended tensile strength of the ink will not improve and it will become brittle; If it is, the effect will be lost and the tensile strength of the ink will be reduced, so 10~
A range of 40 parts by weight is required, with the preferred range being 20-30 parts by weight.

In addition, the bisphenol A type epoxy resin as component d) constituting this composition is used to make the target ink composition excellent in heat resistance and give it stiffness. This includes commercially available products with a molecular weight of 500 to 4, such as Epicoat 1004 (product name manufactured by Yuka Shell Co., Ltd., molecular weight 1,600) and Epicoat 1001 (product name manufactured by Yuka Shell Co., Ltd., molecular weight 900).
000 and a solid type is preferred. In addition, the amount of this bisphenol A epoxy resin added is the same as above-mentioned a.
) If the amount is less than 10 parts by weight per 100 parts by weight of the saturated polyester resin as a component, the heat resistance and stiffness of the ink composition will not be improved sufficiently; If the amount is more than i part, the target ink will become hard and brittle, which will cause cracking and peeling phenomena during winding.
The preferred range is 15 to 30 parts by weight.

Next, the solvent as component f) constituting this composition dissolves or suspends the above-mentioned components a) to d) to form a liquid ink composition, so it dissolves the components a) to d). Alternatively, it may be suspended, and examples thereof include toluene, MEK, ethyl acetate, carbinol acetate, and cellosolve acetate, but it may also be a mixture thereof. The amount of component f) used is 25 to 35% by weight of the components a) to d) described above as a solid content, and a viscosity of 100 to 1.0 OO at 25°C.
cps, preferably 350 to 500 cps, 200 cps per 10 weight parts of the saturated polyester resin as component a).
500 parts by weight, but this preferred range is 250 to 3 parts by weight.
The amount is 50 parts by weight.

The conductive ink composition of the present invention is made by adding a silicone resin as component e) to a composition consisting of the above-mentioned components a) to d) and component f). Powdered resin is said to be suitable for improving the heat resistance, lubricity, and mold releasability of the conductive ink layer, and commercially available Tospearl 120. 240 [part name manufactured by Toshin Silicone Co., Ltd.] is exemplified. The amount of this silicone resin added is 100% of the saturated polyester resin which is component a).
If it is less than 1 part by weight, the heat resistance, lubricity, and mold releasability imparted to the conductive ink composition will be insufficient;
When the amount exceeds 0 parts by weight, the conductive ink composition becomes brittle.
When the ink sheet is in the form of a roll or a laminate, a peeling phenomenon occurs between the ink sheet and the aluminum layer deposited, so the amount is required to be in the range of 1 to 10 parts by weight.

The conductive ink composition of the present invention can be obtained by uniformly mixing predetermined amounts of the above-mentioned components a) to f), and in this mixing, the saturated polyester resin as the component a) and the saturated polyester resin as the component f) Mixed with a solvent as a component,
d) bisphenol A type epoxy resin as a component and f
It is preferable to mix a mixture of component () with a solvent, then mix carbon black as component (b) and silicone resin as component (e), and then mix in the isocyanate as component (C). The ink composition of the present invention thus obtained has an electrical conductivity of 0.5 to 10 cm by adding component b), and it becomes a heating element when an electric current is passed through it, so it is energized. It can be used for thermal transfer type ink ribbons, but since it contains silicone resin as component e), it has excellent heat resistance, lubricity, and mold releasability, and as a result, print head wear is reduced. This provides the advantage that there is no sticking between the print head and the conductive ink layer, no blocking between the transfer ink layer and the conductive ink layer, and no eight lines of transfer ink into the conductive ink layer. .

Next, examples of the present invention will be given, where parts in the examples indicate parts by weight.

(Example) 160 parts of a mixed solvent of toluene/MEK 1/1 was added to 100 parts of Stafix P-LC (mentioned above), a modified ether type polyester resin with a molecular weight of 20.000,
The mixture was uniformly kneaded using a kneader at 25°C for 1 hour, and bisphenol A epoxy resin Epicoat 100 was added.
4 Add 160 parts of a mixed solution of toluene/MEK-1/1 to 25 parts of (above) and knead at 25°C for 1 hour using a kneader. 4.5 parts of powdered resin Tosvar 120 (mentioned above) and 30 parts of acetylene black are added and kneaded for 1 hour at 25°C using a kneader. Finally, add polyisocyanate,
A conductive ink composition was prepared by adding 18 parts of Coronate (described above) and kneading the mixture at 25° C. for 1 hour.

Next, a commercially available polyethylene terephthalate film with a thickness of 6 μm on which aluminum was vapor-deposited to a thickness of 3,000 mm was prepared, and the above conductive ink composition was applied onto the aluminum vapor-deposited layer using a #110 (90 μm depth) application roll. Then, perform direct gravure printing so that the dry coating wrinkles are 8 μm, roll it up on a paper tube, and heat it at 60℃.
Aging for 3 days.

On the back side of the film obtained in this way, ketone resin and ME
A pressure-sensitive adhesive consisting of K was applied to a thickness of 2 μm, and an ethylene-vinyl acetate copolymer (with a ring and ball softening temperature of 7 μm) was applied on top of the adhesive.
2° C.), ester wax (melting point 60), pigment, and tornige is applied to a 4 μm thick sheet to produce a thermal transfer ink sheet.

The thermal transfer ink sheet obtained in the above manner was
Slit it into a ribbon shape with a length of 400 m and use an English typewriter Quletwriter lllPr1.
5202 (product name manufactured by IBM Corporation in the United States) to print in Draft Mode (high-speed printing mode).
When 100,000 characters were printed at a printing speed of 160 cps) and a performance test was conducted, the following evaluations were obtained.

1) No wear on the print head. 2) No deterioration in heat resistance of the conductive ink layer, causing no ribbon burning or sticking between the print head and the conductive ink layer. 3) Electric conductivity to the print head. 4) Blocking between the transfer ink layer and the conductive ink layer does not occur, and the transfer ink does not spread to the conductive ink layer or peel off.

For comparison, a conductive ink composition was prepared by removing the silicone fine powder resin and Tosvar 120 (mentioned above) from the conductive ink composition of the present invention, and a thermal transfer ink sheet and a thermal transfer ink ribbon were prepared in the same manner as above. When it was manufactured and subjected to the same performance test as described above, the following results were obtained.

1) Burning occurred due to deterioration of heat resistance of the conductive ink layer at approximately the 1000th character. 2) As a result, sticking occurred between the print head and the conductive ink layer, and damage occurred between the print head pins due to adhesion of the conductive ink composition. Leakage occurred and the print quality deteriorated. 3) When the deposit was removed from the print head and the head surface was observed, significant wear was observed. 4) The difference between the conductive ink layer and the transfer ink layer Blocking between the conductive ink layers often occurred, and peeling or migration of the transfer ink to the conductive ink layer was observed in some places.

From the above, it has become clear that the present invention provides much higher reliability than conventional products at high printing speeds.

Claims (1)

[Claims] 1. a) 100 parts by weight of saturated polyester resin, b) 20 to 50 parts by weight of carbon black, c) 10 to 40 parts by weight of polyisocyanate, d) 10 to 40 parts by weight of bisphenol A epoxy resin, A conductive ink composition comprising: e) 1 to 10 parts by weight of a silicone resin; and f) 200 to 500 parts by weight of a solvent.