JPH02279377A - Electrothermal transfer ink ribbon - Google Patents

Abstract

PURPOSE:To obtain the good adhesiveness to a conductive layer in spite of a sufficiently low electric resistance value without using a crosslinking agent by forming an electric resistance heating layer from a composition wherein specific conductive carbon is dispersed in and mixed with the resin having the compatibility with the conductive layer. CONSTITUTION:An electric resistance heating layer is formed in such a state that conductive carbon is dispersed in and mixed with a resin having the compatibility with a conductive layer and, as the conductive carbon, one having DBP oil absorbancy (ml/100g)A of 11X10 < A < 18X10 is used and this carbon is contained in the heating layer in an amount of 5 - 8pts.wt. per 10pts.wt. of the total amount of said layer and the thickness of the heating layer is set to 10g/m<2> or less. By this method, the adhesiveness to the conductivity is enhanced in spite of a low resistance value and the diffusion of a current in a surface direction can be suppressed to the min. and the unstability of heat value caused by the adhesion of the component of the heating layer to an electrifying head is eliminated and a fine and sharp image can be stably obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an ink ribbon for electrical thermal transfer used in electrical select printers, and more specifically, the present invention relates to an ink ribbon for electrical thermal transfer used in electrical select printers, and more specifically, an ink ribbon for electrical thermal transfer in which a thermal transferable image forming layer is provided on one side of a film base material. The present invention relates to an ink ribbon for electrical thermal transfer, the other surface of which is provided with a conductive layer made of a thin metal layer, and the surface of the conductive layer is provided with an electrical resistance heating layer.

[Prior Art/Problems to be Solved by the Invention] This type of ink ribbon uses Joule heat generated by energizing the heat-generating layer through the recording needle of the current-carrying head of the printer to remove the heat-sensitive transferable image forming layer. partially heated,
An image is formed on a receptor such as recording paper.

Therefore, the electrical resistance value of this heat generating layer greatly affects its heat generation amount. If the electrical resistance value is too high, the heat generation amount will be too large, and the heat generation layer will be destroyed by electricity, forming a good printed image. There was a problem that it was not done. Moreover, an excessive electrical resistance value also causes a problem in terms of energy consumption, in that a large amount of electrical energy is required to pass current through the heat generating layer.

Therefore, in the past, it was considered best to set the electric resistance value of the heat generating layer as low as possible, and conductive carbon black with a large oil absorption amount, such as Ketchen black with good conductivity, was dispersed in the resin.

However, this type of highly conductive carbon black inhibits the adhesion of the binder resin to the conductive layer, and is used in large amounts (II! % or more), a part of the heating layer peels off and adheres to the current-carrying head.

In order to prevent such drawbacks, the present inventors attempted to crosslink the resin by mixing a crosslinking agent such as isocyanate into the heat generating layer, but in this case, the crosslinking reaction was unstable. This method has the disadvantage that defective products are likely to be produced and productivity is significantly reduced.

In view of these circumstances, it is an object of the present invention to provide a heat generating layer that has a sufficiently low electrical resistance value and good adhesion to a conductive layer without using a crosslinking agent such as the above-mentioned isocyanate.

[Means to solve the problem]

In order to achieve this object, in the present invention, the electric resistance heating layer is formed by dispersing and mixing conductive carbon in a resin having an affinity for the conductive layer, and the DBP is used as the conductive carbon. Oil absorption amount (ml / 100
g) as A, 11X 10<A<1
8x10 is used, and the total amount of the heat generating layer is 1
When 0 parts by weight, the content is 5 to 8 parts by weight, and the thickness of the heat generating layer is 1.0 i/d or less.

[Function/Example]

The oil absorption of the conventionally used Ketchen Black is 30
It is on the order of 0 or more and has an extremely high value, but it was conventionally thought that carbon black with such a high oil absorption value is good for lowering the electrical resistance value.

However, in the present invention, contrary to such common technical knowledge, the resistance value of the heat generating layer is made sufficiently low by using conductive carbon with an oil absorption of less than 180, which is extremely lower than that conventionally used. Even if it is contained in a large amount, the adhesive strength of the binder resin to the conductive layer does not decrease at all.

Furthermore, by setting the thickness of the heat generating layer to 1Og/rf or less, it is possible to minimize the diffusion of current in the plane direction while maintaining a low resistance value, making it possible to obtain delicate impressions. Ta.

In the present invention, due to such an effect, instability in the amount of heat generated due to adhesion of the heat generating layer to the energizing head is eliminated, and while a stable amount of heat is obtained in accordance with the amount of energization,
You can make delicate and clear impressions.

In addition, since it does not use cross-linking agents such as isocyanates, it is chemically stable and does not cause a decrease in manufacturing yield, or may change over time during storage after manufacturing and may no longer function as intended. I was able to eliminate the problem.

Next, the present invention will be specifically explained.

The film base material may be a resin film with a thickness of 2 to 20μ such as a polyester film, a polycarbonate film, a polypropylene film, a polyamide film, a polyimide film, a cellulose triacetate, a polyvinyl alcohol film, a polyvinyl chloride film, or a thickness such as a condenser vapor. High-density paper with a thickness of 5 to 40 μm can be suitably used.

The heat-sensitive transferable image forming layer formed on one side of the film base material is a sublimation transferable image forming layer containing a sublimable coloring agent in a binder that is sublimated and transferred to a receptor to form a printed image; Alternatively, it may be a melting/softening image forming layer that forms an image by transferring to a receptor by heating and melting or softening, and any conventionally known image forming layer may be used. It is.

Among the melting/softening inks, those having a melting point or softening point of the transfer ink of about 60 to 90° C. can be used satisfactorily.

The conductive layer is provided on the opposite side of the film base material to the side on which the heat-sensitive transferable image forming layer is provided, and a metal material having extremely good electrical conductivity such as aluminum, zinc, copper, or silver is deposited. Alternatively, it may be bonded using a method such as foil stamping, and the appropriate thickness is about 300 to 1,000 layers.

The electrical resistance heating layer is made by dispersing and mixing conductive carbon in a resin that has an affinity for the conductive layer, and the conductive carbon has a DBP oil absorption amount (ml/1) of the conductive carbon.
00 g) as A, 11X 10<A<
18X 10 (more preferably 125<A<180
), and when the total amount of the heat generating layer is 10 parts by weight, the content is 5 to 8 parts by weight, and the thickness is 10 g/rrf or less.

Regarding the relationship between the content of the conductive carbon and the thickness of the heat generating layer, when using the same carbon, the electric resistance value can be kept below a certain value by increasing the content as the thickness decreases. However, due to the electrical properties of carbon, the relationship between content and thickness is not necessarily constant.

If the coating thickness of the heat generating layer exceeds the above range, the heat generating area in the heat generating layer will expand abnormally, and the size of the dots that form the impression will be significantly larger than the intended size. This makes it difficult to make delicate impressions.

Moreover, when the content of carbon exceeds the upper limit, the adhesion with the conductive layer decreases. On the other hand, if the carbon content is less than the lower limit, the electric resistance value increases significantly and the amount of heat generated becomes excessive.

Furthermore, when using carbon whose oil absorption ff1A exceeds the upper limit, the adhesion with the conductive layer is significantly reduced,
On the other hand, if it is below the lower limit, sufficient conductivity cannot be obtained and an abnormally high amount of heat is generated.

As the resin material as the binder, those having affinity for the conductive layer can be used, such as amino resin, polyester resin, epoxy resin, urethane resin, vinyl chloride-vinyl acetate copolymer resin, acrylic resin. , amide resin, cellulose resin, phenoxy resin, etc. can be used alone or as a mixture or copolymer of two or more.

The formation of the resistance heating layer is carried out by dispersing a dispersion prepared by uniformly dispersing and mixing conductive carbon into a solution in which the binder resin is dissolved in an appropriate solvent on the conductive layer of the film base material provided with the conductive layer. This can be done by coating and drying to the desired coating thickness. The ink ribbon for electrical thermal transfer of the present invention can be changed by forming the heat-sensitive transferable image forming layer on the film substrate opposite to the resistance heating layer.

Next, the present invention will be explained by giving experimental examples.

Experimental Examples 1 to 6 In this experimental example, the presence of an image forming layer is an inhibiting factor in evaluating the performance of the heat generating layer in the following points, so experiments were conducted using one without an image forming layer. .

[Inhibiting factors in evaluating the heat generating layer by the image forming layer] (1) Inhibiting factors in evaluating adhesion to the head When the ink ribbon is stored rolled into a pancake shape,
If even a portion of the image forming layer is transferred to the surface of the heat generating layer, the components of the image forming layer will normally adhere to the head, making it impossible to determine whether the heat generating layer is young or not.

(2) Inhibiting Factors in Evaluation of Heat-Generating Layer Destruction Evaluation of heat-generating layer destruction is based on the light transmitted through the ribbon, so a change in the image forming layer causes a change in the transmitted light, making it impossible to determine whether the heat-generating layer is destroyed.

(3) Inhibiting factors in evaluation of print clarity Since the image produced by the image forming layer is influenced by the function of the ink of the image forming layer, the function of the receiving paper, and the combined function of both,
This makes it impossible to correctly evaluate the print clarity due to the heat generating layer itself.

Using a commercially available polyester film with a thickness of 4.5μ,
Aluminum was deposited on one side to a thickness of 550 mm, and a heat generating layer having the structure shown in Table 1 was formed on the surface of this aluminum deposited layer. The heat generating layer was formed by dissolving polyester resin [with a glass transition point of 10°C (value measured by DSC)] in an appropriate solvent, adding conductive carbon to this, and dispersing and mixing with an attritor for 10 hours. The dispersion was applied and dried, and then aged at 45 to 60°C for 60 hours. In Table 1, the percentage in parentheses indicates the percentage (% by weight) of each component relative to the total amount of the heat generating layer.

The resistance value of the heating layer was measured using a resistivity meter (Uresta PP manufactured by Mitsubishi Yuka Corporation).
, 4-needle (As) type) was used to determine n1. The term "low resistance value" used in the present invention means that the value measured by this measurement method is smaller than 10Ω.

“DBP” in Table 1 refers to DBP oil absorption (unit: 2ml)
/ 100g). DBP oil absorption is JIS
It was measured according to the regulations of K6221.

Thermal paper (TP manufactured by Jujo Paper Co., Ltd.) was used instead of the image forming layer and receiving paper.
50 KS-A (color development temperature: 70°C), and an energized select printer, Quiet Lighter (manufactured by CIBM), was used to form a printed image in color on the thermal paper.
A printing experiment was carried out by adjusting the amount of current supplied to the printer (Writer) to a constant value. In this case, the printing pattern used alphabets and numbers, and was evaluated by printing two lines of 95 characters per line on the A4 size thermal paper as one unit.

Adhesion of the heat generating layer to the current-carrying head, destruction of the heat generating layer, and print freshness dust were evaluated. The evaluation method and criteria are as follows.

(1) Evaluation of adhesion to the head When one unit of printing was completed, the surface of the electrode part of the head was visually observed and graded according to the condition of the dirt and the ease of removing the dirt as shown below. .

5: No deposits were observed.

4: Although deposits were observed on less than about 30% of the area of the electrode portion, any deposits could be easily removed by wiping with methanol.

3: Deposits were observed on more than 30% of the electrode area, but
Both were easily removed by wiping with methanol.

The heat generating layer component adhering to the two poles could not be removed by wiping with methanol.

Not only the heating layer but also the conductive layer and base film adhered to the ribbon, making it impossible for the head to slide with the ribbon.

(For the sample after using the evaluation criteria for two-layer destruction, visual observation was performed from the heat generating layer side using transmitted light from the surface where the image forming layer should originally be formed, and observation using reflected light from the heat generating layer side. and go
The evaluation was graded as follows.

6: No damage to the heat generating layer was observed by either light, or only minute damage was observed to the extent that the characters could not be read.

5: Damage was observed to the extent that the letters were legible under transmitted light, but no damage was observed under reflected light, or only minute damage was observed to the extent that the letters were unreadable.

4: Damage to the extent that letters were legible was observed under both lights.

3: The entire contact portion of the head was damaged to the extent that characters could not be written.

2: There were holes in the base film.

1: The sample broke during the test.

(3) Evaluation of print clarity Visually observe the thermal paper on which the impression has been formed, and check whether there is a shading pattern (unevenness) in the impression or jaggedness (sharpness) at the border of the printed image. They were observed and graded as follows.

4: Neither sharpness nor unevenness was observed.

3; Unevenness was observed, but no sharpness was observed.

2: Both sharpness and unevenness were observed, but the characters were legible.

It was impossible to read the text.

The experimental results are shown in Table 1.

[Left below] As is clear from the above experimental results, the D of conductive carbon
If the BP oil absorption is within the range of the present invention, all evaluation items should be satisfied and the overall evaluation is high, but if the DBP oil absorption of the conductive carbon is too large or too small,
The overall evaluation indicates that it is not suitable for use.

〔Effect of the invention〕

By using conductive carbon with oil absorption in a specific range for the heat generating layer, it has low resistance and excellent adhesion to the conductive layer, and the thickness of the heat generating layer can be reduced to 10 g/rrr.
By doing the following, it is possible to minimize the diffusion of current in the plane direction while maintaining a low resistance value. This eliminates instability in the amount of heat generated due to the bone canal of the heat generating layer component relative to the current-carrying head, making it possible to stably print delicate and clear images.

Claims (1)

[Scope of Claims] 1. A heat-sensitive transferable image forming layer is provided on one side of a film base material, a conductive layer made of a thin metal layer is provided on the other side, and an electrical resistance heating layer is provided on the surface of the conductive layer. In the ink ribbon for electrical thermal transfer, the electrical resistance heating layer is formed by dispersing and mixing conductive carbon in a resin that has an affinity for the conductive layer, and the conductive carbon is a DBP oil-absorbing layer. When the amount (ml/100g) is A, 11 × 10 < A < 18 × 10 is used, and when the total amount of the heat generating layer is 10 parts by weight, it is contained in 5 to 8 parts by weight, and An ink ribbon for electrical thermal transfer in which the thickness of the heat generating layer is 10 g/m^2 or less.