JPH0755563B2 - Energizing head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-carrying head used in the field of image formation that provides high-quality images with high speed and high sensitivity.

2. Description of the Related Art In order to realize a full-color image at high speed, a conductive dye transfer technology using an ink sheet in which ink containing a sublimable dye is provided on a resistive sheet and a conductive head is suitable. The insulating support that holds the electrode array (multi-stylus) of the energizing head is generally made of ceramics such as alumina, glaze, or thermosetting resin, and is the same regardless of the inside or outside of the electrode pair. Material is used.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention When gradation recording is performed at high speed by using a sublimable dye as a color material in order to obtain a full-color high-quality image, since the recording energy is high, the conventional energizing head is as follows. Have challenges.

The thermal diffusion coefficient of the insulating support of the head has not been optimized and high speed, high sensitivity, and optimized recording dots have not been achieved. When an insulating support having a small thermal diffusion coefficient is used, the sensitivity is improved, but the recorded image suffers from color turbidity due to heat accumulation and a reduction in resolution. On the contrary, if an insulating support having a large thermal diffusion coefficient is used, the sensitivity is lowered and the characteristic of current transfer is lost. Further, the heat pulse generated as a result of applying the signal current to the electrode pair is concentrated in the vicinity of the electrodes of the resistance sheet, and uniform recording dots cannot be obtained.

The present invention aims to solve such problems of the conventional technology.

Means for Solving the Problems In a current-carrying head in which a pair of electrodes facing each other are embedded in an insulating support, the thermal diffusion coefficient of the insulating support inside the electrode pair is made smaller than that outside.

When a signal current is applied to the working electrode pair, the heat diffusion coefficient of the insulating support outside the electrode pair is large, so that concentrated heat pulses in the resistance sheet near the electrode pair diffuse along the insulating support outside the electrode pair. . As a result, the formed recording dots have a uniform rectangular shape and high color density can be obtained. At the same time, since the excess heat stored in the resistance sheet is appropriately released, it is possible to suppress color turbidity and deterioration of resolution even during high-speed recording. At this time, a decrease in sensitivity can be suppressed by the heat retention effect due to the small thermal diffusion coefficient of the insulating support inside the electrode pair.

Embodiment FIG. 1 is a sectional view showing the structure of an embodiment of the present invention.

1 is an ink sheet, 2 is an energizing head, 3 is an image receiving paper, and 4 is a platen.

The ink sheet 1 is formed by forming the color material layer 12 on the resistance sheet 11. As the resistance sheet 11, a resistance film formed by mixing conductive particles such as carbon into a heat resistant resin is used. As the heat-resistant resin, a film-forming resin such as polyimide, aramid, polycarbonate, polyester, polyphenyl sulfide, or polyether ketone is used. These resistive films have a thickness of about 4-15μ,
Surface resistance is about 1K ohm.

The color material layer 12 is formed of at least a sublimable dye and a binder resin.

The image receiving paper 3 comprises a base paper 32 and a dyeing layer 31 provided on the base paper 32.

The energizing head 2 includes an electrode pair array 23 in the insulating supports 21 and 22.
A line head is constructed by embedding a and 23b.
The electrodes are made of copper, phosphor bronze, tungsten, titanium, brass or the like. The electrode resolution is 6-16 dots / mm. The support is made of ceramics, which has a small friction coefficient and is slightly more abradable than the electrodes. At this time, it is important that the thermal diffusion coefficient A of the support inside the electrode pair be smaller than A outside. The value of A = k / dc (k: thermal conductivity, d: density, c: specific heat) is 10 ⁶ m ² / s, and the inner support 22 is 5x1.
It is 0 ⁶ or less, more preferably 1 × 10 ⁶ or less. Further, the electrode pairs outside the A at 1x10 ⁶ or more, 5x10 ⁶ or higher is more preferable. The material of such a support has various glazes inside the electrode pair,
Mica ceramics, glass ceramics, crystallized glass, and minerals such as kaolin and talc are used. On the outer side of the electrode pair, BN, ALN-based ceramics (for example, ALN-BN-based composite material), alumina, glass ceramics, or solid lubricant having high electric resistance is also used.

Although one of the electrode pairs is an individual signal electrode and the other is a common electrode, the common electrode does not necessarily have to be divided.

Next, the driving method will be described.

The signal current path applied between the electrodes 23a and 23b flows through the resistance layer in parallel with the film. The recording condition at this time is that the pulse width applied to one dot is 1 ms, the recording cycle for one line is 4 ms, and the peak temperature of the heat generating portion reaches 300-400 ° C. Generally, the current density distribution, that is, the peak temperature distribution, is particularly large in the vicinity immediately below the stylus electrode, but in the structure of the present invention, the temperature distribution is uniform between the electrode pairs, and rectangular recording dots are obtained. Further, since the head heat storage and the heat radiation are well balanced, a high-sensitivity and high-quality image can be obtained. Such high temperature and high pressure (3Kg / 10
0 cm), the ink sheet 3 and the image receiver 4 are
Run between the heads. Relative speed recording is performed between the image receiving paper and the sheet in order to effectively utilize the sheet as necessary. It was experimentally found that the friction coefficient at this time must be 0.2 or less at room temperature to enable smooth running recording between the head and the sheet. Further, in order to promote this, the head may be configured so that the lubricant flows out from the surface of the head at a high temperature, or conversely, the lubricant may flow out from the resistance sheet.

More specific examples will be described below.

(1) Energizing head: A6 line head, resolution 8 dots /
mm (stylus electrode material is tungsten), the electrode pair inside is mica ceramics insulating support, and the electrode pair outside support material is BN-ALN composite ceramics. Applied pulse width 1ms, recording cycle 4ms / line, pressure 3Kg / 100mm for constant velocity recording and relative velocity recording. (Speed ratio n = 1-10) (2) Resistance sheet: A film formed by mixing carbon in aramid resin and having a thickness of 10 μ and a surface resistance of 1 K ohm.

(3) Color material layer: formed with a thickness of 2 μ in terms of the weight solid content ratio of the indoaniline-based cyan sublimable dye 1 and the polycarbonate resin 1.

(4) Receptor: A white PET film having a thickness of 100 μ and a thickness of 8 μ in terms of solid content ratio of polyester resin 1 and silica 0.2.

As a result of conducting the recording experiment under the above conditions, the recording cycle was 4 ms /
The line has a recording energy of ² J / cm ² and there is no fog in the image,
Smooth gradation recording characteristics were obtained by the relative velocity method. This recorded image has an image quality equivalent to that of dye transfer recording using a thermal head as a recording unit. In addition to the above dyes, magenta and yellow colors were used to obtain an A6 full-color image in about 10 seconds.

Advantages of the Invention (1) High-speed, high-sensitivity full-color recording with 1-line recording speed of 4 ms and recording energy of 2 J / cm is possible.

(2) Large and uniform recording dots can be formed.

(3) The image is sharpened with no color turbidity.

(4) The relative speed ratio n = 10 is obtained under the above recording conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a recording state using an energizing head according to an embodiment of the present invention. 2 …… energizing head, 21,22 …… insulating support, 23a, 23b ……
Electrode pair.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuji Kawakami 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Keiichi Yubaue, 1006 Kadoma, Kadoma, Osaka Matsushita Electric Industrial (56) Reference JP-A-64-90773 (JP, A)

Claims (3)

[Claims] 1. A current-carrying head in which a pair of electrodes facing each other are embedded in an insulating support, wherein a thermal diffusion coefficient of an insulating support inside the electrode pair is smaller than that outside. 2. The thermal diffusion coefficient of the insulating support inside the electrode pair is 5 ×.
The current-carrying head according to claim 1, wherein the current-carrying head is 10 ⁶ m ² s ^-1 or less. 3. The thermal diffusion coefficient of the insulating support outside the electrode pair is 1 ×.
The current-carrying head according to claim 1, wherein the current carrying head is 10 ⁶ m ² s ^-1 or less.