JPH0427945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head for printing on thermal paper.

A thermal printer is used to record on thermal paper.A thermal printer applies a thermal printing head, in other words a thermal head, which has dot-shaped heating resistors arranged on the thermal paper, and instantly heats any heating resistor. This allows you to record desired numbers, letters, and shapes. The performance of this thermal printer, such as printing speed and printing life, is determined mostly by the characteristics of the thermal head.

Thermal heads come in thin-film, thick-film, and semiconductor types, depending on how the heating resistor is made, and each has its advantages and disadvantages. That is, the thin film type is suitable for high resolution, high speed, and has good image quality, but it is difficult to make a large head and the manufacturing technology is not easy. The thick film type has a simple manufacturing process, is suitable for mass production, and can reduce costs, but its image quality is not good because it has poor thermal response and is difficult to create fine patterns. In addition, the semiconductor type has a fast thermal response, but it is difficult to make a long head and increases the cost. Currently, thin-film thermal heads are often used due to the demand for higher density and lower power performance.
That is, low-power color development and high-speed thermal response depend on the thermal properties of the material constituting the thermal head and its structure, including its geometry.

Thin-film thermal heads use their heating resistor.
TaN, NiCr, etc. are generally used, and these have advantages such as excellent heat resistance and temperature coefficient, and good adhesion to the underlying glass layer. As shown in FIG. 1, the structure of the head is such that a heating resistor layer 3 is provided on a ceramic substrate 1 and a glass substrate 2, and electrode metals 4 are provided with leads extending from both ends of the resistor 3. resistor protective layer (e.g.
SiO ₂ ) 5 and a wear-resistant layer (Ta ₂ O ₅ , SiC, etc.) 6 are provided in a layered manner.

Sputtering technology is generally used to form these thin films. For example, as a heating resistor material
If TaN is selected, tantalum (Ta) and nitrogen gas (N ₂ ) are fed separately to create a tantalum nitride thin film resistor (Fig. 1, 3) using so-called reactive spackling.
form. When a Ta ₂ N resistor is used as a general resistor, a Ta ₂ O ₅ film is formed on the surface to prevent deterioration of the resistor due to oxidation, but when used as a thermal head, it is exposed to high temperatures of 300 to 400°C. SiO ₂ is used as a protective film (Fig. 1, 5) to receive heat pulses.
Approximately 2 μm is deposited using RF (high frequency) spackle ring.
It blocks oxygen from outside. However, _SiO2
is not sufficiently hard, and if it is scanned by applying it to thermal paper (the pressure on the thermal paper is 200 g/cm ² ), the amount of wear will be as much as 5 μm/Km. Therefore, Ta ₂ O (Fig. 1 6) with a Pickkas hardness of 800 to 950 was placed on top of SiO ₂ .
Approximately 10 μm is formed by reaction spackle.
Further, the resolution in the thermal head is related to the density of the heat-sensitive resistor, the density of the heating resistor is determined by the density of the lead wire (electrical conductor wire), and the density of the lead wire is approximately determined by the thickness of the lead wire. In other words, a thin film type with a lead wire thickness of 2 μm is more advantageous than a thick film type in terms of resolution. This lead wire is formed on the heat-sensitive resistor by vapor deposition (FIG. 14).

In this way, especially thin film type thermal heads are constructed through the above-mentioned processes such as sputtering and vapor deposition, which makes the manufacturing process complicated and time-consuming, and the cost of the thermal head is inevitably high.

Therefore, the present invention is an improvement on the conventional thermal head. By constructing a heating wire in which a metal conductor is partially exposed and covered with a heating resistor wire through a simple process such as etching, the manufacturing process can be reduced and An object of the present invention is to provide a thermal head that can shorten the time and reduce costs.

In order to achieve such an object, the thermal head of the present invention is a thermal head in which a plurality of heating elements for printing on thermal paper are arranged in parallel on a substrate, and the heating elements are fixed by an insulating fixing layer. The heating element is composed of a wire made of a heating resistor and a metal conductor covering the wire, and a predetermined portion of the wire is exposed by etching to form a heating portion.

Preferred embodiments of the present invention will be described below with reference to the drawings.

In the thermal head of the present invention, as shown in FIG. 2, a heating element 11 is fixed on a substrate 10 by an insulating fixing layer 12 which also serves as protection. As shown in FIG. 3, the heating element 11 is made up of a heating resistance wire 13 made of a wire and a metal conductor 14 covering the wire, and a predetermined portion of the heating resistance wire 13, that is, a heating portion 15 is covered with the metal conductor. 14 is removed and exposed by etching.

The heating element 11 is made of Ni-Cr with a diameter of 40 to 100 μm, for example.
A Cu (copper) metal conductor 14 is placed on the heating resistance wire 13 of
When plating, electroplating is performed directly and continuously. The plating thickness at this time is about 20 to 50 μm. Furthermore, in order to increase the resolution, a thinner heat-sensitive resistance wire 13 is required, and the plating thickness must also be made thinner.

The heating resistance wire 13 is plated with Cu.
The heat generating portion 15 is exposed by etching.
Etching is performed after the heat generating resistance wires 13 are fixed and arranged in parallel on the substrate at locations other than the heat generating portion 15 using the insulator fixing layer (inorganic adhesive) 12 (for example, the fourth
(Fig.), a resist is applied to the parts other than the heat generating part 15, and etching is performed. After etching, in order to prevent heat dissipation between the heat generating part 15 and the substrate 10, an inorganic adhesive is further filled, and the area that is touched by the thermal paper is smoothed.

FIG. 4 shows a case where such a heating element 11 is used in, for example, a 7-dot serial printer. In FIG. 4, seven heating elements 11 are arranged in parallel on a substrate 10 with one end connected to a common terminal 16. Then, it is fixed by an insulator fixing layer (FIG. 2, 12). The other end of each fixed heating element 11 is controlled by a drive circuit (not shown) of the main body via a lead wire 17 (for example, a signal line of a flat cable). That is, each heat generating part 15 generates heat depending on each signal, but in this case, the current has a characteristic of flowing through the metal conductor 14 (FIG. 3) on the surface of the heat generating element 11, and the current flows through the heat generating part 15. Other than the heating resistance wire 14, the current flows through the metal conductor 14 to the common terminal 16 (FIG. 4).

The substrate 10 to which the heating element 11 is fixed is set on the printing surface (back side in the figure) of the wood 20 in the head of a thermal printer as shown in FIG. The carriage 20 moves on rails 21 and 22, which are driven by a timing belt 2 via rollers 24 and 25 driven by a servo motor 23.
6 with high precision. Thermal paper is fed by the printing roller 27 and the stepping motor 2
8, a predetermined amount is sent for each pulse. In other words, each horizontal row of supplied thermal paper is printed, and one character is printed by 5 horizontal rows of 7 dots, which is the number of heating elements, totaling 35.
Printed with dots. If you want to print one character more beautifully, you can increase the number of heating elements and make the horizontal movement pitch finer, but in reality, 24 x 24 dots is enough to print beautifully, and even in the minimum case, 7 x 5 dots is sufficient. There is no practical difference.

Furthermore, when the heating element 11 is used in a line printer, the circuit configuration is as shown in FIG.
At this time, a separate diode array 29 is used. In FIG. 6, one of the seven heating elements 11 is connected to the signal lines l ₁ to l ₇ through the respective diodes of the diode array 29 in opposite directions, and the other is connected to the control terminal T ₁ ( _T2 , _T3 ...)
are connected to constitute one block. A plurality of these blocks are arranged in parallel according to the paper width of the thermal paper, and one
Controlled on a block-by-block basis. For example, to make the first heating element of the _T1 block and _T3 block generate heat, it is done by grounding the terminals _T1 and _T3 and applying a voltage to the signal line _l1 . Then, one horizontal line of the supplied thermal paper is heated at one time, and this is repeated every time the thermal paper is fed, so that one character's worth of one horizontal line is printed every five pitches of paper feeding. In this case as well, more precise fonts can be printed by increasing the number of heating elements 11 in one block to 8, 12, or 16 and slowing down the paper feeding speed.

Next, although the above-mentioned heating element was originally constructed by plating a metal conductor on a thin heating resistance wire, as shown in Fig. It can also be manufactured by covering a copper pipe over a copper pipe, rolling it several times, and drawing it with a wire drawing machine to make a single-core conductor wire with a diameter of several mm and a length of 1 m. The heating resistance wire and metal conductor manufactured in this manner constitute a heating element in which a heating portion is provided by exposing the heating resistance wire at a predetermined location by etching, as shown in FIGS. 2 and 3. It is also used in serial printers or line printers.

As is clear from the above embodiments, according to the present invention, a heating element is constructed by coating a heating resistance wire with a metal conductor in a thermal head and exposing the heating resistance wire at a predetermined location by etching. The manufacturing time and steps can be shortened, and the cost of the thermal head can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a conventional thermal head, FIG. 2 is a sectional view showing the structure of the thermal head of the present invention, and FIG. 3 is a sectional view showing the structure of the heating element in the thermal head. Fig. 4 is an explanatory diagram of the thermal head of the present invention configured for a serial printer, Fig. 5 is a conceptual diagram showing the printing mechanism when the thermal head of Fig. 4 is incorporated, and Fig. 6 is an explanatory diagram of the case where the thermal head of the present invention is configured for a serial printer. FIG. 7 is a circuit diagram when the thermal head of the invention is used in a line printer, and FIG. 7 is a flowchart when the heating element of the thermal head is constructed by another method. DESCRIPTION OF SYMBOLS 11... Heating element, 12... Insulator fixed layer, 13... Heat generating resistance wire, 14... Metal conductor, 15... Heat generating part.

Claims (1)

[Claims] 1 A thermal head in which a plurality of heating elements for printing on thermal paper are arranged in parallel on a substrate, and the heating elements are fixed by an insulating fixing layer, and the heating elements are composed of a wire made of a heating resistor and a wire rod made of a heating resistor. 1. A thermal head comprising a metal conductor covering a wire, wherein a predetermined portion of the wire is exposed by etching to form a heat generating portion.