JPH01262152A - End surface type thermal head - Google Patents

Abstract

PURPOSE:To enhance printing quality by reducing the accumulation quantity of heat and to enhance the reliability of a resistor element part, by extending electrode films at least to the vicinity of the recording surface of a head and making the direction of a current flowing to the membrane resistor elements positioned between the electrode films almost parallel to the recording surface of the head. CONSTITUTION:Electrode films 12 are extended up to a recording surface A and the shape of the resistor element parts 11 at the parts having no electrode films 12 laminated thereto in resistor films 2 is made rectangular. By this method, since the direction of the current flowing through the resistor element parts 11 become almost parallel to the recording surface a, and the temp. distribution of the surface containing the resistor element parts becomes highest in the vicinity of the recording surface A. Therefore, the ratio of generated heat contributing to printing becomes much and heat can be effectively utilized. As a result, the heat accumulated in a head is reduced and difference is eliminated between the size of a dot at the beginning in continuous printing and that of a dot after the elapse of a certain time and printing free from irregularity is obtained. Further, since there is no corner parts in the resistor element parts, the concn. of a current is not generated and, as a result, there is no possibility of pulse breakdown.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an edge type thermal head having a layered structure in which a thin film resistive element is sandwiched between upper and lower substrates, and in which one end face facing a cross section of the thin film resistive element serves as a recording surface. It is something.

(Conventional technology) Conventionally, the structure of a thermal head for boat fishing is as follows.

Substrate (usually a glaze layer formed on ceramic)
A plurality of thin film resistance elements as heating elements were arranged in a row on top of the heat generating element, an extraction electrode was provided on the element, and a thin film protective layer was further provided on the element. Therefore.

The recording surface becomes the surface of the protective layer. In a head having such a configuration, the width of the entire head increases due to the diameter of the platen roller that contacts the head, and there is a limit to miniaturization.

At the same time, since it is not possible to reduce the size of the substrate, productivity during thin film formation is low (many thermal heads cannot be made at the same time), and the cost has reached its limit.

There is also an end-face type thermal head by forming each of the above-mentioned thin film layers on a five-arc shaped end face, but there are only two end faces on one substrate, and if you want to form a thin film layer on those parts, you will need only one end face. Only two thermal heads can be made from this board,
Therefore, productivity was low.

In response to this, an end face type thermal head having a layered structure as shown in FIGS. 6 and 7 has been proposed. First, the 6th
The figure shows the cross-sectional structure of the head. 1 is the lower substrate, which is made of glass. Reference numeral 2 denotes a resistor film formed in a desired pattern, and the material used is Ta2N or Ta205. Reference numeral 3 denotes an electrode film, which is laminated on the resistor film 2 except for a part thereof. The resistor film 2 and the electrode film 3 are formed by a thin film process, and the film thickness of the resistor film 2 is about 0.1 to 1 μm, and the thickness of the electrode film is about 0.5 to 1 μm.
It is approximately 1μ. A protective layer 4 is applied thereon to protect the resistor film 2 and the electrode film 3. This protective layer 4 is currently made of polyimide resin. Furthermore, an upper substrate 6 is bonded thereon with an adhesive 5. As with the lower substrate 1, the upper substrate 6 is made of glass, and the adhesive 5 is made of epoxy or polyimide resin.

FIG. 7 shows the pattern of the resistor film 2, in which the electrode film 3 is not laminated in a portion 2 a + 2 b + 2
c, . . . are resistance element portions serving as heating elements corresponding to recording dots. Resistance element portions 2a, 2b.

The cross-sections of the tips of the resistive elements 2a, 2b, 2c, .

Recording is performed using the heat generated by passing a drive current through.

The resistance element portions 2a, 2b, 2c, . . . have such a shape because both the drive side electrode and the common side electrode must be drawn out in the same direction.

However, in the thermal head configured in this way, the resistive element portions 2a, 2b, 2c, . . .

Since the pattern is formed in a substantially U-shape, the temperature distribution on the surface including the resistance element portion is as shown in FIG. In particular, current concentration occurs at the bends of the resistance pattern, resulting in high temperature areas.

In other words, heat generation is significant at positions far from the recording surface.

This means that the heat generated is not effectively used for printing.
This means that more heat is accumulated inside the head, causing variations in the size of printed dots, and that pulse breakdown is more likely to occur in areas where current is concentrated.

(Objective of the Invention) The present invention solves the above-mentioned problems of the prior art all at once. It effectively utilizes heat by bringing the high-temperature part closer to the recording surface, reduces heat accumulation, improves printing quality, and improves printing quality. It is an object of the present invention to provide a tooth surface type thermal head that improves the reliability of the element section.

(Structure) In order to achieve the above object, the present invention includes a lower substrate, a plurality of thin film resistive elements disposed on the lower substrate so that a cross section thereof faces a recording surface of a head, and a thin film resistive element. In an end-face type thermal head comprising electrode films connected to both ends of the head, and an upper substrate bonded to cover the thin film resistive element and the electrode film, the electrode film extends at least to the vicinity of the recording surface of the head, The direction of current flowing through the thin film resistive element located between the electrode films is approximately parallel to the recording surface of the head.

According to this configuration, the temperature near the recording surface of the head is highest, so that heat is effectively used for printing. Furthermore, since heat accumulation is reduced accordingly, variations in the size of dots are eliminated, and a printed state of constant quality can always be obtained. Also, since there are no weak points in thin film resistive elements,
The reliability of the head can be improved.

(Embodiment) Hereinafter, embodiments will be described in detail with reference to the drawings.6 Figure 1 shows an embodiment of the present invention, in which a resistive element section 11
And the electrode film 12 is shaped like this.

In other words, the electrode film 12 is extended to the recording surface A, and the resistor element portion 1 of the portion of the resistor film where the electrode film 12 is not laminated.
The shape of 1 is made to be a rectangle. Note that, as in the conventional example, a resistor film, an electrode film, and a protective layer are laminated on the lower substrate, and the upper substrate is further bonded with an adhesive so as to cover them.

In this embodiment configured in this manner, the direction of the current flowing through the resistive element section 11 is approximately parallel to the recording surface A, and as a result, the temperature distribution on the surface including the resistive element section is as follows.
As shown in the figure, the temperature near the recording surface A is highest. Therefore, the proportion of the generated heat that contributes to printing increases, and the heat can be used effectively. In addition, less heat is accumulated inside the head, and there is no difference between the initial dot size during continuous printing and the dot size after a certain period of time, resulting in consistent printing. Become. Furthermore, since the resistor element part does not have a corner unlike the conventional one, current concentration does not occur, and therefore there is no fear of pulse breakdown.

FIG. 3 shows another embodiment of the invention.

The resistive element portion 1 is heated so that the temperature near the recording surface A becomes higher.
A notch is provided on the side opposite to the recording surface of No. 3.

FIG. 4 shows an example in which the resistive element parts 11 are driven individually using electrode films 14 connected to both ends of the resistive element parts 11, without using a method in which a common electrode is provided for a large number of resistive element parts. .

FIG. 5 shows still another embodiment of the present invention,
The electrode film 15 does not extend to the recording surface A, but is stopped near it. This is to prevent a short circuit between the electrode films due to dew condensation or the like when the cross section of the electrode film 15 is exposed to the recording surface A.

Also in each of the above embodiments, the direction of the current flowing through the resistive element section is generally parallel to the recording surface.

The same effects as the embodiment shown in FIG. 1 can be obtained.

(Effects of the Invention) As explained above, according to the present invention, problems that occur with conventional U-shaped pattern resistance elements, namely, low thermal efficiency (heat utilization), large amount of heat storage, and pulse breakdown occur. It is possible to solve the first problem at once and realize a highly efficient, high quality, and highly reliable end-face type thermal head.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a pattern of a resistive element portion and an electrode film according to an embodiment of the present invention, FIG. 2 is a temperature distribution diagram obtained by the same pattern, and FIGS. 3 to 5 are respectively in accordance with the present invention. FIG. 6 is a sectional view of the conventional example; FIG. FIG. 8 is a temperature distribution diagram generated by the pattern of the conventional example. DESCRIPTION OF SYMBOLS 1... Lower substrate, 2... Resistor film, 3... Electrode film, 4... Protective layer, 5... Adhesive. 6... Upper substrate, 11, 13... Resistance element section, 12.
14.15... Electrode film. Patent applicant: Ricoh Co., Ltd. Figure 1 Figure 3 Figure 4 Cause Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] a lower substrate, a plurality of thin film resistive elements disposed on the lower substrate so that their cross sections face the recording surface of the head, electrode films respectively connected to both ends of the thin film resistive elements, and the thin film resistive elements. and an upper substrate bonded to cover an electrode film, wherein the electrode film extends at least to the vicinity of the recording surface of the head, and the current flows to a thin film resistive element located between the electrode films. An edge-type thermal head characterized in that the direction of current is approximately parallel to the recording surface of the head.