JP3170315B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head suitably used for a facsimile communication apparatus, a printing apparatus of a word processor, a copying apparatus for copying an original image, and the like.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view of a conventional thermal head 1. As shown in FIG. Insulating substrate 2 made of a material having electrical insulation
Above, a plurality of heating elements 3 are arranged in a straight line to form a heating element line 4. One common side of each heating element 3 is commonly connected to a common electrode line 5, and the other side of each heating element 3 is an individual electrode 6 formed for each heating element 3.
Are connected to a plurality of drive circuit elements 7. The common electrode line 5 and the individual electrode 6 are formed by patterning a metal thin film such as aluminum by photolithography.

The common electrode line 5 is connected to the insulating substrate 2
Is formed along the outer periphery of Each drive circuit element 7 is connected to a signal line 8 for selectively energizing the heating element 3 to generate heat, and each signal line 8 is connected to an external wiring board 9.
Connected to. The insulating substrate 2 having such a configuration is
Heat sink 1 made of a metal material such as aluminum
0 is attached.

[0004]

In such a thermal head 1 of the prior art, as shown in FIG. 5, for example, the heating elements 3 are arranged at the same density as the recording density of the thermosensitive recording paper.
Since the terminals of each drive circuit element 7 correspond one-to-one with the individual electrodes 6, a large number of drive circuit elements 7 are required. Therefore, for example, when the recording density becomes 16 dots / mm or more, extremely high positioning accuracy is required in manufacturing the heating elements 3 and the individual electrodes 6, and there is a problem that the manufacturing yield is reduced. Further, there is a problem that a large number of drive circuit elements 7 are required, the number of parts is increased, the cost is increased, and the configuration is enlarged.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems, to prevent a reduction in manufacturing yield even when a high recording density is required, and to reduce the number of parts. An object of the present invention is to provide a thermal head that can be downsized.

[0006]

According to the present invention, a transparent electrode layer, a photosensitive layer made of a material whose specific resistance decreases upon exposure to light, a heating resistor layer, and a ground potential are provided on an electrically insulating transparent substrate. A heat generating means having a ground electrode layer and a protective layer sequentially provided, and a thermal recording medium is slidably contacted with the protective layer,
The photosensitive layer is selectively irradiated with light through a transparent substrate and a transparent electrode layer to partially lower the specific resistance of the photosensitive layer, and to energize the heating resistor layer between the transparent electrode layer and the ground electrode layer. A thermal head is characterized in that a heat-generating printing is performed by causing a heat-generating resistor layer to partially generate heat and transmitting the heat to a heat-sensitive recording medium.

[0007]

In the thermal head according to the present invention, a transparent electrode layer is provided on a transparent substrate having electrical insulation, and a photosensitive layer made of a material whose specific resistance decreases upon exposure to light is provided on the transparent electrode layer.
A heat generating means is provided in which a heating resistor layer and a ground electrode layer are sequentially provided on the photosensitive layer, and a protective layer is further provided. The transparent insulating substrate is selectively irradiated with light to partially lower the specific resistance of the photosensitive layer, and is selectively energized between the transparent electrode layer and the ground electrode layer to perform thermal printing.

Therefore, the necessity of forming the heating elements separated from each other having the arrangement density corresponding to the recording density and the individual electrodes defining the heating elements with high precision is eliminated, and the production yield is remarkably improved. Can be. Further, a drive circuit element to which a predetermined number of mutually separated heat generating elements are connected is not required, so that the number of components can be significantly reduced and the configuration can be downsized.

[0009]

FIG. 1 shows a thermal head 1 according to an embodiment of the present invention.
FIG. 2 is a system diagram showing a configuration of a thermal head 1.
1 is a sectional view of FIG. The thermal head 11 of the present embodiment
For example, a transparent substrate 1 made of glass and having electrical insulation properties
2, a transparent electrode layer 13 made of a transparent conductive material such as ITO (indium tin oxide) is formed on the entire surface of the transparent substrate 12.

On the transparent electrode layer 13, when a predetermined amount of light is received, the specific resistance of the light receiving portion decreases, for example, a semiconductor such as aluminum semiconductor, a selenium-based inorganic semiconductor material, or an organic semiconductor material such as lophthalocyanine. A photosensitive layer 14 made of a material is formed on the entire surface. A heating resistor layer 15 made of, for example, tantalum nitride Ta ₃ N ₄ is formed on the entire surface of the photosensitive layer 14, and a common electrode layer made of a metal material such as aluminum, copper, or gold is formed on the heating resistor layer 15. 16 are formed on the entire surface. The common electrode layer 16 is coated by forming a protective layer 17 made of an electrically insulating material such as SiN by a vacuum film forming method such as sputtering. The thermal paper 19 is pressed against the protective layer 17 by the platen roller 18 to perform thermal printing as described later.

Such a transparent substrate 12 or a protective layer 17
In order to form an optical image which is thermally printed on the transparent substrate 12 of the heating means 20 composed of a laminate of
1 and a reflecting mirror 22 that reflects the laser beam 30 from the laser beam generator 21 and scans the transparent substrate 12 in the direction of arrow A1. The reflection mirror 22 is rotationally driven by the driving device 23 in synchronization with the oscillation operation of the laser light generation device 21, and scans the transparent substrate 12, specifically, the photosensitive layer 14. At this time, a light spot 24 by the laser light on the photosensitive layer 14 is formed.
Can be adjusted according to a desired recording density by an optical system including the reflection mirror 22 and the like.
For example, the diameter d1 is selected to be about 100 μm. A power supply 25 is connected to the transparent electrode layer 13, and a common electrode layer 16 is connected to the power supply 25.
Is connected to the ground potential.

As the photosensitive layer 14, for example, a material having a characteristic that the specific resistance rapidly decreases when the radiant energy level such as the amount of light exceeds the threshold value E0 as shown by the line L1 in FIG. The degree of the decrease in the specific resistance is preferably as steep as possible, and the threshold value E0 is preferably as small as possible in terms of energy efficiency.

The operation of this embodiment will be described below.
The laser light from the laser light generator 21 is reflected by the reflecting mirror 22 which is rotated and driven by the driving device 23, and forms a light spot 24 on the photosensitive layer 14 via the transparent substrate 12 and the transparent electrode layer 13. At this time, as described above, the photosensitive layer 14
The specific resistance of the light-receiving portion 26 of the light-receiving portion 26 decreases, and passes through the photosensitive layer 14 and the heating resistor layer 15 corresponding to the light-receiving portion 26,
A current 31 flows between the transparent electrode layer 13 and the common electrode layer 16. As a result, the heating resistor layer 15 generates heat, and the heat generating portion 32 performs thermal printing on the thermal paper 19.

In this embodiment, the heating elements 3 which are separated and independent from each other and the individual electrodes 6 which define the heating elements 3 as described in the conventional example are formed by high-precision photolithographic technology. The need is eliminated and the manufacturing yield is greatly improved. Further, in the conventional example, the necessity of using the drive circuit elements 7 to which the predetermined number of individual electrodes 6 are connected is eliminated, the number of parts can be reduced, the cost can be reduced, and the drive circuit elements 7 need to be used. Therefore, the configuration of the thermal head 11 can be significantly reduced in size. Moreover, in this embodiment, the heating means 20 uses the common electrode layer 16 maintained at the ground potential.
Is disposed on the side of the protective layer 17 that comes into contact with the thermal paper 19, so that during printing operation, contaminants such as chlorine ions contained in the thermal paper 19 cause film formation defects (pinholes) in the protective layer 17 due to Coulomb force. ) Is not attracted to the common electrode layer 16, so that the corrosion of the common electrode layer 16 due to contact of contaminants can be effectively prevented.

FIG. 4 is a system diagram showing the configuration of another embodiment of the present invention. This embodiment is similar to the previous embodiment, and corresponding parts are denoted by the same reference numerals. A point to be noted in this embodiment is that the fluorescent layer 27 is formed on the light receiving side of the heating means 20 and the fluorescent layer 27 is scanned with an electron beam 29 from an electron gun 28 used in a television receiver. As a result, the fluorescent layer 27 emits light in a state corresponding to the electron beam 29, and the fluorescent light causes the heating means 20 to perform the above-described thermal printing operation. Also in this embodiment, similarly to the above-described embodiment, in the heating means 20, the common electrode layer kept at the ground potential is disposed on the side of the protective layer in contact with the heat-sensitive paper, so that the heat-sensitive means can be used during the printing operation. Contaminants such as chlorine ions contained in the paper are not attracted to the common electrode layer through film formation defects (pinholes and the like) in the protective layer due to Coulomb force, and therefore, the common electrode layer is corroded by contact of the contaminants. Can be effectively prevented.

In this embodiment, the same effects as those described in the above embodiment can be obtained.

As another modification of the present invention, the means for supplying an optical image to the heat generating means 20 shown in FIG. 1 is not limited to the above-described embodiment. Alternatively, a planar image may be directly formed on the photosensitive layer 14 in FIG. 1 by an optical image projection device. Further, a light emitting diode array may be used.

[0018]

As described above, in the thermal head according to the present invention, a transparent electrode layer is provided on a transparent insulating substrate, and a photosensitive layer made of a material whose specific resistance decreases upon exposure to light is provided on the transparent electrode layer. A heating means is provided in which a heating resistor layer and a ground electrode layer are sequentially provided thereon, and further a protection layer is provided. Therefore, the necessity of forming the heating elements separated from each other with the arrangement density corresponding to the recording density and the individual electrodes defining the heating elements with high precision is eliminated, and the production yield can be remarkably improved. In addition, a drive circuit element to which a predetermined number of mutually separated heating elements are connected is not required, so that the number of components can be significantly reduced and the configuration can be downsized. In particular, in the present invention, since the ground electrode layer is disposed on the protective layer side, during printing operation, contaminants such as chlorine ions contained in the thermosensitive recording medium cause film formation defects (pinholes and the like) in the protective layer due to Coulomb force. ) Is not attracted to the ground electrode layer, and therefore, corrosion of the ground electrode layer due to contact of contaminants can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a system diagram of a thermal head 11 according to an embodiment of the present invention.

FIG. 2 is a sectional view of the thermal head 11;

FIG. 3 is a graph illustrating characteristics of a photosensitive layer 14.

FIG. 4 is a system diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a perspective view of a thermal head 1 of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Thermal head 12 Transparent substrate 13 Transparent electrode layer 14 Photosensitive layer 15 Heating resistor layer 16 Common electrode layer 20 Heating means 21 Laser light generator 22 Reflector 25 Power supply 27 Fluorescent layer 28 Electron gun

Claims (1)

(57) [Claims] 1. A transparent electrode layer, a photosensitive layer made of a material whose specific resistance decreases upon exposure to light, a heating resistor layer, a ground electrode layer held at a ground potential, and a protective layer are sequentially formed on an electrically insulating transparent substrate. A heat generating means provided, and selectively irradiating light to the photosensitive layer through a transparent substrate and a transparent electrode layer while sliding a heat-sensitive recording medium on the protective layer to partially reduce the specific resistance of the photosensitive layer. And
The heat-generating resistor layer between the transparent electrode layer and the ground electrode layer is energized to partially generate heat in the heat-generating resistor layer, and the heat is transferred to the heat-sensitive recording medium to perform thermal printing. Thermal head.