JPH0852890A - Thermal printing head - Google Patents

Abstract

PURPOSE:To embody a lightweight inexpensive thermal printing head high in the degree of freedom from the aspect of the planning of the dimension of a common electrode (and reinforcing electrode), imparting high recording image quality and proper in the thickness of its substrate. CONSTITUTION:A slope 102 is formed to at least one side of a heat conductive substrate 101 and a connection pad 108 is formed on the slope 102 and a driver IC 203 is arranged on a driver circuit substrate 200 separate from the heat conductive substrate 101. Therefore, in a thermal printing head, the driver IC 203 to which the bonding wire 202 for taking the connection with the connection pad 108 is connected is mounted on the driver circuit substrate 200 and the main surface of the flat substrate 201 on which the driver IC 203 of the driver circuit substrate 200 is mounted and the slope 102 of the heat conductive substrate 101 are almost parallelly arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head, and in particular, in an image recording system using the thermal print head, when the recording medium such as a card or a film is thick or hard, the recording medium is of high quality without being deformed. The present invention relates to a thermal print head that can obtain image quality.

[0002]

2. Description of the Related Art In an office automation equipment such as a personal computer, an information communication equipment such as a facsimile, and an output printing equipment such as a measuring machine, a hard copy device using a thermal print head has a low running cost and maintenance. It is used in various ways because of its advantages such as easy points and quiet image recording.

[0003]

However, in the conventional thermal print head, the driver IC is formed on the surface parallel to the surface on which the heating element array is formed (that is, on a uniform plane). Since the heating element array and the driver IC are formed), the recording medium (printing medium) on which an image is recorded by the thermal print head is placed on the cover while avoiding the protrusion corresponding to the thickness of the circuit element such as the driver IC. Since it is necessary to move it, it is deformed by bending it. Therefore, there is a problem that it is difficult to record an image on a hard or thick recording medium.

As one solution to this problem, a thermal print head called a real edge type has been developed in which a heating element array is formed on the edge portion of the substrate.

However, it is extremely difficult in practice to form a pattern on two surfaces having an angle of 90 degrees and electrically connect it, and the resolution is about 8 dots per 1 mm at most, and the reliability of the connection portion is high. Only low quality and low quality were obtained.

Therefore, a thermal print head having a structure as shown in FIG. 4 has been proposed and put into practical use for recording on a hard or thick recording medium.

This is because a slope 503 is provided on one side in the longitudinal direction of the substrate 502 on which the heating element array 501 is formed, the heating element array 501 is formed on the slope 503, and this slope 503 is the recording medium 504. The recording medium 504 is installed so as to face the flat main surface in parallel, and as shown in FIG. It is designed so that recording can be performed on a flat plate. A heat radiating plate 506 is lined with the substrate 502.

Further detailed structures of the substrate used in FIG. 4 are shown in FIGS. By forming an obtuse angled slope on one side of the substrate 502 and forming a continuous pattern on the two surfaces, the slope and the main surface, it is possible to perform image recording even on a recording medium that cannot be deformed like the real edge type described above. Is intended.

However, in the conventional thermal print head having the above structure, the desired high resolution,
There are various problems in obtaining high-quality recording characteristics. Alumina ceramics is generally used as the substrate 502 having a good thermal conductivity, which is preferably used for the thermal print head. This is because when forming a high-definition pattern using a thin film formed by sputtering or a thick film formed by printing as the heating element 501 of the thermal print head, there are restrictions on the roughness, flatness, and heat resistance of the substrate surface. Is. A glaze film 507 is used as a heat insulating layer formed on the surface of the substrate. This is because the heating element 501 generates heat of about several hundreds of degrees, and the insulating layer made of resin has many reliability problems.

A substrate 50 made of the above alumina ceramics.
2 is generally 0.5 to 2 mm thick. If the thickness is 0.5 mm or less, there is a problem of cracking or flatness, and if the thickness is 2 mm or more, there is a problem that the thermal print head is heavy and costly. Have difficulty.

Therefore, the thickness of the substrate 502 cannot be made too thick, and the width of the slope 503 cannot be made too large in order to make the thermal print head small.

Further, since the wiring pattern 508 which is continuous to the main surface of the substrate must be formed on the inclined surface 503, it is not preferable in terms of quality to arrange the main surface 509 of the substrate and the inclined surface 503 at a large angle.

FIG. 5 is a plan view of a so-called substrate portion used in the thermal print head, and FIG. 6 is a sectional view thereof. Referring to this, it is necessary to form the common electrode (and the reinforcing electrode) 510 and the portion where the heating element 501 is formed on the slope 503. However, the element size of the heating element is the required resolution. The width of the slope 503 is limited, and therefore the common electrode 51
The width forming 0 (and the reinforcing electrode) is severely limited.
In other words, there is a problem in that the degree of freedom in the dimensions of the common electrode (and the reinforcing electrode) 510 is extremely small and the design is severely limited.

The glaze layer 509, which is an insulating layer, is formed by a spray method. A single plane substrate can be formed by printing, but since the glaze layer 509 needs to be formed to have a uniform thickness on the slope 503,
In the printing method, it is practically difficult to form a uniform film. Slope 503
If the glaze layer 509 is not formed uniformly, the heat energy generated in the heating element 501 escapes to the substrate 502 side more unevenly than the surface of the heating element, resulting in uneven density during image recording. is there.

Needless to say, in a high-definition thermal print head, it is extremely important to form the shape of the heating element of the heating element 503 uniformly. If the shape of the heating element of the heating element 501 varies, the resistance value of the heating element 502 varies and the amount of heat generation also varies, so the recording image quality deteriorates. Therefore, in order to improve the quality of the recorded image, it is extremely important to form the shape of the heating element of the heating element 501 uniformly.

However, the heating element 5 is placed on the slope 503.
In the case of forming 01, it is extremely difficult to bring the glass mask used for pattern formation sufficiently close to the slope 503 of the substrate 502 because of the physical shape of the glass mask. As a result, there is a problem in that the shape of the manufactured heating element 501 varies, and the amount of heat generated varies, which deteriorates the recording image quality.

As an image recording method using a thermal print head, transfer recording using an ink film is often used for recording on plain paper. When the recording paper is hard or thick, a partial glaze substrate in which the glaze layer 507 has a convex shape is effective.

However, the partial glaze method described above cannot be realized by a spray method in which an insulating layer (glaze layer) is formed by spraying because it needs to be formed by a printing method. As one solution, a method of etching the glaze to make the glaze shape convex after firing the glaze can be considered. However, similar to the patterning of the heating element 501, the pattern formation on the inclined surface 503 causes a decrease in accuracy, and the pattern is not accurate. There is a problem that patterning is difficult.

A protective film 511 is formed on the heating element 501 in order to prevent abrasion of the recording medium during traveling. The protective film 511 is formed by sputtering in a thin film type thermal print head, and is formed by printing in a thick film type thermal print head. However, when the protective film 511 is thin, the abrasion property is deteriorated, and when the protective film 511 is thick, heat conduction is hindered and the image quality is deteriorated.
Therefore, the protective film 511 needs to be uniformly formed in an appropriate thickness range. However, the slope 50
Similar to the case of forming the glaze layer 509, the formation of No. 3 has a problem that it is extremely difficult to control the thickness.

The present invention has been made to solve such a problem, and an object thereof is to freely design the size of the common electrode (and the reinforcing electrode) in the conventional thermal print head as described above. The problem is that the image quality is extremely low, the image quality is degraded due to variations in the shape of the heating elements, it is difficult to form accurate patterns such as the glaze layer and protective film, and the thickness of the substrate. The problem that the thickness and thickness of the thermal print head become excessively large and the cost is excessive is effectively solved by a simple technique, and the degree of freedom in designing the dimensions of the common electrode (and the reinforcing electrode) is high, and recording is possible. It is intended to realize a thermal print head which has high image quality, a moderate thickness of a substrate, is lightweight, and is low in cost.

[0021]

A thermal print head according to the present invention comprises a heat conductive substrate, a heat insulating layer formed on the heat conductive substrate and electrically insulated, and a heat insulating layer formed on the heat insulating layer. A heating element array, a common electrode for supplying a current to the heating element array, a reinforcing electrode, an individual electrode connected to the heating element for selectively passing a current to the heating element, and a connection to the individual electrode In a thermal print head having a connected connection pad and a driver IC connected to the connection pad via a connection wiring, a slope is formed on at least one side of the heat conductive substrate, and the connection pad is the The driver IC is formed on an inclined surface, and the driver IC is mounted on a drive circuit board separate from the heat conductive board, and the driver I of the drive circuit board is mounted.
It is characterized in that the drive circuit board and the heat conductive board are installed such that a main surface on which C is mounted and an inclined surface of the heat conductive board are substantially parallel to each other.

[0022]

In the case of a hard recording material or a thick recording material that cannot be easily deformed, the presence of protrusions above the surface on which the heating element array is formed is not allowed. When a desired image is recorded using the heating element array, it is necessary to connect a driver IC to each heating element, but the driver IC may be connected by wire bonding, flip chip, TAB (tape out bonded bonding), or any other connection method. The thickness including the cover for protecting the driver IC and the resin mold part is at least 0.5m even if connected and mounted by
Therefore, it cannot be mounted on a surface having the same height as the surface on which the heating element array is formed. Rather, the thickness (height) of the driver IC and the resin mold portion becomes thicker (higher) than that of the heat generating array.

Therefore, the driver IC is connected in a plane which is not parallel to the heating element forming surface with the driver IC connecting portion being an inclined surface.
By connecting with, it becomes possible to record an image on an undeformable recording medium. Moreover, by providing an inclined surface on the bonding pad portion as in the present invention, the size of the common reinforcing electrode as shown in the description of forming the conventional heating element on the inclined surface cannot be sufficiently obtained. Problem, the problem that convex glazes such as partial glazes that are effective for transfer recording cannot be formed, and resistance shapes easily vary.
It is possible to solve the problems that it is difficult to make the thickness of the glaze uniform, the image quality is deteriorated, and the thickness of the protective film is easily varied.

That is, according to the present invention, since the surface on which the heating element array is formed is flat as in a general thermal print head that does not form a slope, the patterning of the heating element array formed thereon is performed. The mask for patterning can be sufficiently close to each other and can be applied to a thermal print head having a higher resolution than that of the conventional technique in which the heating element is formed on the slope.

Further, the common reinforcing electrode can be applied with the specifications of a general thermal print head, and can also correspond to high-speed image recording. The glaze as the heat insulating layer can be formed by the conventional general printing method as in the case of the general thermal print head, and the heating element can have a uniform glaze thickness. Similarly, the protective film thickness does not have to be varied because it is not necessary to form the heating element on the slope.
On the contrary, the glaze thickness of the bonding pad portion formed on the slope portion varies, but the bonding is not affected by the variation of the glaze thickness and the surface property is the same, so that a good connection is possible.

A thermal print head having a convex glaze shape is particularly suitable for performing transfer recording with high image quality. Therefore, when the present invention is applied to a thermal print head having such a convex glaze shape, the above-mentioned advantages of the present invention are obtained as compared with a conventional thermal print head in which a heating element array is formed on a slope. The image quality can be dramatically improved while making the most of it.

Also, in terms of mounting the driver IC, since the pads on the IC and the bonding pads on the substrate can be arranged on the same parallel surface as in the conventional case, good quality can be realized.

[0028]

Embodiments of the thermal print head according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing the outline of the structure of a thermal print head according to the present invention. This thermal print head has a heating element array substrate 100, a drive circuit board 200, and a heat dissipation plate 300 as its main components.

FIG. 2 is a view showing the structure of the heating element array substrate 100 according to the present invention. The method of forming the slope 102 along one side in the longitudinal direction of the heat conductive substrate 101 made of alumina ceramics may be the same as the method of forming the slope forming the heating element array on one side of the conventional substrate. Therefore, the thermal print head of the present invention has the advantage that it is simple in terms of its manufacturing method, and that it is possible to form the heating element array at least with the size and accuracy that can be formed by the conventional manufacturing method. .

As a method of forming the heat conductive substrate 101 before firing, there are a method of shaping using a mold and a method of polishing and shaping with a grindstone after firing. The slope 102 can be formed by such a manufacturing method.

Subsequently, the glaze layer 103, which is a heat insulating layer on the heat conductive substrate 101, can be manufactured by the same process as the conventional process. In other words, the thickness of the glaze layer 103 on the inclined surface 102 does not need to be uniform unlike that of the heating element portion, and therefore can be formed by a simple printing method. Here, when it is desired to make the slope of the slope 102 a larger angle, for example, the glaze layer 103 is formed on the flat upper surface portion of the heat conductive substrate 101 by the printing method, and the slope 10
The glaze layer 103 may be formed on the second layer 2 by a spraying method.

On the glaze layer 103, structures similar to those of a general thermal print head are formed, such as the heating resistance element 104, the individual electrodes 105, the common electrode and the reinforcing electrode 106, and the protective film 107. The material film for forming the structure can also be formed by a general film deposition method, and the patterning of individual material films can be performed by a patterning method such as general etching. What is required is that the most accurate patterning is required, and the array of the heating resistance elements 104, which has been difficult to accurately pattern since it was formed on the slope in the past, is an array of the heat conductive substrate 101 in the present invention. The connection pad 108, which is formed on the flat upper surface and does not require highly precise patterning as much as the heat generating resistance element 104, is the slope 10.
This is because they are arranged on the upper side of 2. Thus, according to the present invention, it is possible to form a uniform heating resistor array with a smaller variation in shape as compared with the case where an array of heating resistor elements 104 is formed on the slope 102.

The drive circuit board 200 is formed separately from the heating element array board 100. On the flat substrate 201 of the drive circuit board 200, the connection pads 10 of the individual electrodes 105 on the heating element array board 100 are formed.
8 is connected to the driver IC 203 via a connecting wiring material such as a bonding wire 202,
Board). A protective cover 204 is provided to protect the driver IC 203, the bonding wire 202, and other mounted objects. Note that, in addition to the bonding wire 202, for example, a connection lead by a TAB mounting method can be used as the connection wiring, but generally, wire bonding is considered to be the best matching as the connection wiring.

The heating element array 100 is arranged so that the inclined surface 102 of the heating element array 100 and the flat main surface of the base 201 of the drive circuit board 200 are substantially horizontally continuous.
The drive circuit board 200 and the drive circuit board 200 are fixed on the heat dissipation plate 300.

As described above, the thermal print head according to the present invention can be realized by using the same manufacturing method as the conventional one,
Further, as described above, the same manufacturing method can be applied to the mounting of the driver IC and the protective cover, the mold, or the like of the mounting portion, so that it can be manufactured extremely easily.

Further, as described above, the heating element array 100
The heat radiating plate 300 is provided on the slope holding the drive circuit board 200 and
For example, an aluminum plate (or an aluminum rod) may be extruded for easy formation.

As for the type of thermal print head to which the present invention can be applied, in addition to the above, the present invention is applicable even if the glaze layer 103 has a convex shape as shown in FIG. it is obvious. In particular, a thermal print head having such a convex glaze shape is suitable for performing transfer recording with high image quality. Therefore, if the present invention is applied to this, a thermal element array in which a conventional heating element array is formed on a slope is used. Compared with the print head, the image quality can be further improved while taking advantage of the present invention.

[0039]

As is clear from the detailed description above, according to the present invention, the degree of freedom in designing the size of the common electrode (and the reinforcing electrode) in the conventional thermal print head as described above is extremely small. Problem, the deterioration of the recording image quality due to variations in the shape of the heating element, the problem that it is difficult to form an accurate pattern such as the glaze layer and the protective film, and the thickness of the substrate increases. The problem that the weight and cost of the thermal print head become excessive is effectively solved by a simple technique, the degree of freedom in designing the size of the common electrode (and the reinforcing electrode) is high, and the recording image quality is high. It is possible to realize a thermal printhead in which the substrate has an appropriate thickness, is lightweight, and is low in cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a thermal print head according to the present invention.

FIG. 2 is a cross-sectional view of a thermal printhead substrate according to the present invention.

FIG. 3 is another cross-sectional view of the thermal print head substrate according to the present invention.

FIG. 4 is a cross-sectional view showing a structure of a conventional thermal print head for recording on a hard or thick recording medium.

FIG. 5 is a plan view showing the structure of a conventional thermal print head for recording on a hard or thick recording medium.

FIG. 6 is a cross-sectional view showing a structure of a heating element array substrate of a conventional thermal print head for recording on a hard or thick recording medium.

[Explanation of symbols]

 Reference numeral 101: Thermal conductive substrate 102: Slope 103: Glaze layer 104: Heating resistance element 105: Individual electrode 106: Common electrode and reinforcing electrode 107: Protective film 108 Connection pad 200 Drive circuit board 300 Heat sink

Claims (1)

[Claims] 1. A heat conductive substrate, a heat insulating layer formed on the heat conductive substrate and electrically insulated, a heating element array formed on the heat insulating layer, and a current supplied to the heating element array. A common electrode and a reinforcing electrode, an individual electrode connected to the heating element for selectively passing a current to the heating element, a connection pad connected to the individual electrode, and a connection wiring to the connection pad Driver IC connected via
A thermal print head having a slope formed on at least one side of the heat conductive substrate, the connection pad formed on the slope, and the driver IC separate from the heat conductive substrate. The drive circuit board is mounted on a body drive circuit board, and the main surface of the drive circuit board on which the driver IC is mounted and the inclined surface of the heat conductive board are substantially parallel to each other. A thermal print head, wherein a thermal conductive substrate is installed.