JP7023541B2 - Substrate for thermal head and manufacturing method for substrate for thermal head - Google Patents

Description

The present invention relates to a substrate for a thermal head and a method for manufacturing a substrate for a thermal head. More specifically, the present invention relates to a substrate for a thermal head used in a facsimile, a color printer, a bar code printer, etc., and a method for manufacturing the substrate for the thermal head.

Patent Document 1 discloses a thermal head that performs heat-sensitive recording by selective heat generation of a heat-generating resistor with respect to a heat-sensitive recording paper. In Patent Document 1, the substrate on which the heat-generating resistor and the drive circuit are formed is turned over to make the substrate uniformly thin to function as a wear-resistant layer, or tilted and ground to use the thin tip portion as the wear-resistant layer. A functional thermal head is described.

Patent Document 2 discloses a thermal head using a thin film transistor as a drive circuit. In Patent Document 2, the thickness of the substrate on which the heat-generating resistor and the drive circuit are formed is changed to 10 to 800 μm and adhered to the heat-dissipating plate, and the thermal resistance of the substrate is changed to control the amount of heat-dissipated and store heat. It is described that the print quality is improved by.

Patent Document 3 discloses a thermal printer head such as a facsimile or a word processor. In Patent Document 3, a thin film film is used as a drive circuit, and in order to improve the temperature rise of the drive circuit and heat storage in the heat generation resistor forming region, the drive circuit and the heat generation resistor forming region composed of the vicinity of the heat generation resistor and the thin film film are formed. It is described that the heat transfer from the above can be improved by interposing a metal pattern.

Japanese Unexamined Patent Publication No. 63-222866 Japanese Patent Application Laid-Open No. 62-242552 Japanese Unexamined Patent Publication No. 4-140152

Since the thermal head described in Patent Document 1 has no protrusions that affect the diameter of the platen roller (hereinafter referred to as platen) and the running of the heat-sensitive medium, it is easy to reduce the depth dimension of the thermal head. However, it is difficult to control heat dissipation for high-speed and low-speed printing applications, and improving print quality is an issue.

Patent Document 2 discloses a thermal head using a thin film transistor as a drive circuit. In Patent Document 2, the thickness of the substrate on which the heat generation resistor and the drive circuit are formed is uniformly changed to 10 to 800 μm and adhered to the heat sink, and the heat dissipation amount is controlled by changing the thermal resistance of the substrate. , It has been proposed to improve the print quality by heat storage. However, in the case of high-speed printing applications where heat dissipation is required, it is necessary to reduce the thickness of the substrate, and in this case, the strength of the substrate is weak and handling and manufacturing become difficult.

Further, when heat dissipation is relatively not required for low-speed printing applications, the thickness of the substrate can be increased, so that the strength of the substrate becomes relatively strong. However, the temperature propagation from the heating element to the drive circuit formation region increases, and in order to keep the drive circuit region equal to the heat dissipation plate temperature, the drive circuit should be separated from the heating element to a distance equal to or greater than the thickness of the substrate. Since it must be formed, it becomes difficult to miniaturize it.

Patent Document 3 proposes to improve heat storage by arranging a metal pattern for heat dissipation between a heating element and a drive circuit. However, the interposition of the metal pattern for heat dissipation increases the distance between the heating element and the drive circuit, making it difficult to reduce the size.

That is, in the thermal head, since the region where the heating element is formed and the heat storage layer formed under the region where the drive circuit is formed have a uniform thickness, it is difficult to individually control the thermal time constants in those regions. Therefore, it is difficult to reduce the size by minimizing the distance between the two regions.

The substrate for a thermal head according to the present invention has a main surface, a substrate having a heating element forming region and a driving circuit forming region, and each region of the heating element forming region and the driving circuit forming region on the main surface. Includes a heating element and drive circuit integrally formed in, a wiring formed on the main surface for connecting the heating element and the drive circuit, and an inorganic layer formed on the heating element forming region. It includes a heat storage layer and a heat dissipation plate provided on the heat storage layer. Further, the back surface of the substrate facing the main surface has a recess in a region corresponding to the heat storage layer, and the recess functions as a wear-resistant layer.

The substrate for a thermal head according to the present invention is a back surface of a substrate in which a heating element and a drive circuit are integrally formed on a main surface, and has a recess in a region corresponding to the heating element. As described above, since the substrate of the thermal head substrate is not a uniformly thin substrate but has recesses locally, the strength of the substrate can be increased and cracking or breakage of the substrate can be prevented.

As a result, the life and reliability of the thermal head substrate can be improved. In addition, it is equipped with a heat storage layer including an inorganic layer formed on the heating element forming region, and by changing the thickness of this inorganic layer, heat dissipation to the heat sink is controlled, and for thermal heads for high-speed and low-speed printing applications. A substrate can be provided.

Further, the thermal head substrate according to the present invention may be characterized in that the heat storage layer is formed by covering the heating element. In addition, the thermal time constant is made constant by making the cross-sectional area (width * thickness) of the heat storage layer constant. For example, the thermal time constant can be made constant by reducing the width and increasing the thickness. By reducing this width, the size of the thermal head substrate can be reduced. On the other hand, the thermal time constant of the drive circuit formation region is controlled by changing the thickness if the formation area is constant.
Further, it may be characterized in that a groove is provided on the adhesive surface of the heat radiating plate so as to be aligned with the inorganic layer formed on the thermal head substrate. Further, it may be characterized in that an opening or a through hole is provided in a part of the heat radiating plate. Further, the outer shape of the heat radiating plate may be made larger than the outer shape of the thermal head substrate.

In the substrate for a thermal head according to the present invention, since the heat storage layer is formed by covering the heating element, the thickness of the heat storage layer can be changed to change the thermal time constant of the heating element forming region. Therefore, it is possible to provide a substrate for a thermal head for high-speed and low-speed printing.
Further, it may be formed by covering a part or all of the drive circuit forming region. Since the thermal time constant in the drive circuit forming region can be changed, a substrate for a thermal head for high-speed and low-speed printing can be provided. Further, the inorganic layer formed by covering the heating element and the drive circuit region with the inorganic layer may be characterized in that it functions as a reinforcing material for a thin portion of the recessed substrate.

Further, the thermal head substrate according to the present invention may be characterized in that the thickness of the substrate in the recess is 2 μm or more and 100 μm or less. If the thickness of the substrate is less than 2 μm, it is difficult to maintain the quality due to the manufacturing variation of the product, and if the thickness of the substrate is more than 100 μm, the printing will be blurred when printing. , Print quality deteriorates.

On the other hand, since the thickness of the substrate in the recess can be 10 μm or more, the wear-resistant layer of a relatively thick film of 10 μm or more, which was difficult by the vapor deposition method or the sputtering method using a conventional vacuum device, can be obtained. It is possible to provide a substrate for a thermal head that can be formed and has a long life.

Further, the thermal head substrate according to the present invention may be characterized in that a recessed groove is provided in a region corresponding to the heat storage layer on the back surface of the substrate. By providing the groove structure in the shape of a recess, the strength of the substrate is increased, and the durability against external stress during processing and printing is improved.
In addition, the sliding surface of the heat-sensitive medium becomes flat, uneven wear due to the influence of the electrode step can be reduced, and the life of the thermal head substrate can be extended.

Further, in the substrate for a thermal head according to the present invention, the inorganic layer constituting the heat storage layer may be characterized by containing granular alumina or silica having a particle size of 1 μm or more and 100 μm or less. By adjusting the particle size of alumina or silica contained in the inorganic layer constituting the heat storage layer to a range of 1 μm or more and 100 μm or less, the thermal resistance can be adjusted so that the heat storage layer has a desired thermal resistance according to the particle size. You can control the value. On the other hand, when the particle size is smaller than 1 μmm, it becomes too dense after curing, and the thermal resistance of the heat storage layer becomes small, and it is difficult to control the thermal resistance. Further, when the particle size is larger than 100 μm, the surface roughness after curing deteriorates and it becomes difficult to obtain a uniform thickness.

Further, in the substrate for a thermal head according to the present invention, the heating element has a plurality of heat generating portions, one end of the plurality of heat generating portions is connected to a common electrode, and the other end of the plurality of heat generating portions. Each of the above is connected to a corresponding branch electrode, and may be characterized in that the thickness of the common electrode and the branch electrode is 1 μm or more and 50 μm or less. In the substrate for a thermal head according to the present invention, the thickness of the common electrode and the branch electrode can be a relatively thick thickness of 1 μm or more, so that the wiring resistance of the electrodes can be reduced even when the electrode width is reduced. ..

Further, the method for manufacturing a substrate for a thermal head according to the present invention includes a step of forming a heating element, a drive circuit, and wiring for connecting the heating element and the integrated circuit on the main surface of the substrate.
After the step of forming the heat storage layer including the inorganic layer covering the heating element, the step of adhering the heat radiation plate to the surface of the heat storage layer, and the step of adhering the heat radiation plate, the process faces the main surface of the substrate. It is characterized by comprising a step of forming a recess in a region corresponding to the heat storage layer on the back surface.

The method for manufacturing a substrate for a thermal head according to the present invention includes a step of adhering and integrating a heat radiating plate and a thick substrate before grooving a recess, so that the radiating plate has the effect of a backing reinforcing plate and the substrate. It is possible to withstand the external force when the local area is recessed and the external stress applied to the end face of the substrate after completion of the thermal head substrate. Further, in the process of forming the heat storage layer, heat generation during printing and sliding or printing of the heat-sensitive medium are performed by covering a part or all of the heating element or the drive circuit forming region with a hard inorganic layer having high heat resistance. It can withstand the pressure of time and maintain good print quality without deformation.

In the thermal head substrate according to the present invention, the thermal resistance of the region where the heating element is formed and the region where the drive circuit is formed can be individually controlled, so that even if the distance between the two regions is reduced, both regions can be controlled individually. The effect of heat between them can be minimized. As a result, it is possible to reduce the size of the thermal head substrate.

The recess of the thermal head substrate also functions as a wear-resistant layer. Since this recess is formed on the back surface of the substrate facing the main surface on which the heat generation resistor and the drive circuit are formed, the strength of the substrate is strong and the thickness can be increased, so that a substrate for a thermal head having a long life can be provided. Is.

1A and 1B are a plan view and a cross-sectional view schematically showing the configuration of a thermal head substrate according to the present embodiment. 2 (a) and 2 (b) are a plan view and a cross-sectional view schematically showing a thermal head substrate and a heat sink according to the present embodiment. FIG. 3 is a diagram schematically showing a substrate for a thermal head according to the present embodiment. FIG. 3A is a diagram showing the arrangement of the heat generation resistor, the drive circuit, the common electrode, the branch electrode, and the terminal electrode on the substrate for the thermal head. 3 (b) is a plan view of FIG. 3 (a), and FIG. 3 (c) is a diagram showing a cross-sectional view taken along the line X3a-X3a of FIG. 3 (a). FIG. 4 is a diagram schematically showing the circuit wiring of the thermal head substrate according to the present embodiment. FIG. 5 is a diagram for explaining a hybrid type thermal head. FIG. 6 is a diagram for explaining the structure of the thermal head and heat propagation in the heat storage layer. FIG. 7 is a diagram for schematically explaining the manufacturing process of the thermal head substrate according to the present embodiment. FIG. 8 is a diagram showing an embodiment of a thermal head substrate according to the present embodiment. FIG. 9 is a diagram showing an example of the shape and arrangement of the inorganic layer of the thermal head substrate according to the present embodiment. FIG. 10 is a diagram schematically showing another embodiment of the thermal head substrate according to the present embodiment, and is a plan view and a cross section showing a step of dividing the multi-faceted thermal head substrate into individual pieces. It is a plan view and a cross-sectional view of a figure and a heat sink. FIG. 11 is a diagram schematically showing another embodiment of the heat sink for a thermal head according to the present embodiment. FIG. 12 is a diagram schematically showing an embodiment of the concave shape and arrangement of the thermal head substrate according to the present embodiment. FIG. 13 is a diagram schematically showing another embodiment of the heat sink for a thermal head according to the present embodiment. FIG. 14 is a diagram illustrating heat propagation of the thermal head substrate according to the present embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description is omitted.

(Problems with thermal head boards)
First, the problems of the thermal head substrate will be described. FIG. 5 is a diagram for explaining a hybrid type thermal head. As shown in FIG. 5, in the hybrid type thermal head, a heating element formed on a glass layer (board 101) on an alumina substrate, a drive IC chip 104 including a drive circuit mounted on the glass layer, and a drive IC chip 104 are used. It is composed of wiring for connecting the heating element and the drive IC chip.

FIG. 5 shows the positional relationship between the thermal head substrate 101 on which the drive IC chip 104 is mounted, the platen 105, the heat sensitive medium P, the heating element, and the drive IC chip. In FIG. 5, a protrusion is formed in the region where the drive IC chip is mounted.

As shown in FIG. 5, the drive IC chip 101 projects convexly from the surface on the glass layer by the height (“t” in FIG. 5). When the heating element and the driving IC chip are brought close to each other, the platen and the driving IC chip come into contact with each other, so that it is difficult to bring them closer than a predetermined distance. The distance W1 between the heating element and the driving IC chip is the diameter of the platen. Although it is determined by the height of the silicon chip region 101, the distance W1 between the heating element and the drive IC chip is generally designed to be 2 mm or more when the platen diameter is 16 mm. In this case, the influence of heat from the heating element on the drive IC chip can be almost ignored.

On the other hand, in the thermal head substrate (hereinafter referred to as an all-thin film thermal head substrate) according to the present invention in which a drive circuit using a thin film transistor and a heating element are integrally formed, the drive IC chip in the hybrid thermal head is used. No protrusions are formed, and the thermal head substrate can have a substantially flat surface. In this case, the distance between the heating element and the drive circuit can be reduced, so that the size can be reduced. However, if the distance between the heating element and the drive circuit is reduced and brought closer, it has become clear that heat propagation from the heating element causes a problem that the operation guaranteed temperature range of the drive circuit is exceeded in a short time and malfunction occurs. rice field.

First, in the case of a substrate for an all-thin film type thermal head, we will consider what the problem will be. FIG. 6 is a diagram showing a configuration example showing heat propagation from a heating element in a substrate for an all-thin film type thermal head. FIG. 6A shows a cross-sectional structure. This is an all-thin film type thermal head substrate in which the heat storage layer is formed to have a uniform thickness. The uppermost layer is a wear resistant layer 104, and the lower layer thereof is a laminated structure of an oxide resistant film 103, an electrode (not shown), and a heating element 29 in this order. A drive circuit made of a thin film is formed at a distance of W1 from the heating element 29. The drive circuit formation area is displayed as 3B. The substrate 3 is called a heat storage layer, is made of glass and has a thickness of t, and is adhered to the heat radiating plate 4. Further, the meaning of 3A (29) indicates that the forming region of the heating element 29 is indicated as 3A.

Next, the heat transfer from the heating element to the heat storage layer in the printed state will be considered.
The broken lines T1, T2, and T3 in the figure are isothermal curves schematically depicting the state of heat propagation when a single pulse is applied. The temperature changes as T1>T2> T3. Since the X and Y directions of the glass substrate 3 are uniform substances, it is assumed that they propagate isotropically. Further, it is assumed that the heat sink 4 is maintained at room temperature. Then, it is assumed that the X direction has fallen to room temperature (T2) at a distance t. Since it is isotropically propagated, it is considered that the Y direction also drops to room temperature at a distance t.

That is, in the thermal head composed of the heat storage layer having a uniform thickness, the distance W1 must be arranged at a distance of the glass layer thickness t or more in order to keep the temperature rise of the drive circuit at about the heat sink temperature. The thickness of this heat storage layer is generally about 20 to 500 μm.

That is, the distance W1 needs to be arranged at a distance of about 20 to 500 μm or more. By the way, the reason why the thickness of the heat storage layer changes is that it changes depending on the application for high-speed printing (small thermal time constant) and low-speed printing (large thermal time constant). This requires a substrate for an all-thin film type thermal head having a pattern with a different distance W1 depending on the application, which causes a problem that the number of types increases and management becomes difficult.

For example, the heat storage layer (glass layer) having the configuration shown in FIG. 6 is empirically set to a thickness of about 20 to 40 μm for high-speed printing and about 100 to 500 μm for low-speed printing.
Further, FIG. 6 (b) is a plan view showing the heat propagation on the plane in the Y direction of FIG. 6 (a) as a schematic temperature curve.

For ease of explanation, the placement position of each layer is shown in a transparent form. The broken lines T0, T1, T2, and T3 in the figure are isotemperature curves schematically depicting the state of heat propagation when a single pulse is applied. The temperature changes as T0> T1> T3. The distance W1 between one end of the drive circuit and the end of the heating element needs to be arranged with a distance equal to or larger than the thickness of the heat storage layer, and it is difficult to reduce the size of the thermal head substrate.

(Embodiment 1)
1 (a) and 1 (b) are a plan view and a cross-sectional view for explaining the structure of the thermal head substrate 1 of the present embodiment.
FIG. 1 (b) is a cross-sectional view taken along the line X1-X1 of FIG. 1 (a). The substrate 1 for a thermal head is composed of a substrate 8a portion that functions as a wear-resistant layer, an inorganic layer 9M provided between the substrate 8a, a heating element 29, and a heat radiating plate 4, and an adhesive layer 5. A heating element forming region 3A and a drive circuit forming region 3B are provided on the main surface of the substrate 3. A heating element 29 is formed in the heating element forming region 3A, and a driving circuit for controlling a current supplied to the heating element is formed in the driving circuit forming region 3B. An inorganic layer 9M is formed to cover the heating element provided on the main surface of the substrate 3.

At least, the inorganic layer 9M arranged so as to cover the heating element forming region 3A functions as a heat storage layer. Further, the drive circuit forming region is adhered to the heat radiating plate with the adhesive 5 having high thermal conductivity to dissipate heat. However, an inorganic layer can be formed in that region as well, and the amount of heat storage can be changed by changing the thickness and width (volume) of the inorganic layer to change the thermal resistance.

Here, in the drive circuit forming region 3B, the adhesive 5 that adheres the drive circuit to the heat radiating plate has the function of a heat storage layer. In other words, the inorganic layer 9M in the heating element forming region can be configured as the first heat storage layer, and the adhesive 5 in the drive circuit region can be configured as the second heat storage layer. In this case, the size can be reduced by reducing the width W1 of the first heat storage layer and increasing the thickness t. On the other hand, the second heat storage layer can block heat propagation from the first heat storage layer and dissipate heat generated by the driving element.

Further, a groove 11 having a shape that matches the cross section of the inorganic layer 9M is formed on the adhesive surface of the heat radiating plate 4 with the substrate. At least the adhesive layer 5 is formed on the inorganic layer 9M and the drive circuit forming region 3B surface on the main surface of the substrate 3.
Further, the major roles of the heat sink 4 are to control heat dissipation of the inorganic layer and heat propagation to the drive circuit forming region 3B, and to dissipate heat in the drive circuit forming region.

Here, the structure of the thermal head substrate 1 of the present embodiment will be described in more detail. FIG. 14 is a block diagram of the peripheral portion of the heating element of FIG. FIG. 14A shows a cross-sectional structure. A recess 8 is formed in a part of the substrate, and the bottom of the recess has a thin thickness of 8a. A drive circuit and a heating element 29 are formed on the main surface of the opposite surface of the substrate on which the recess is formed. The heat radiating plate 4 and the main surface of the substrate are adhered to each other with an adhesive 5.

The heating element is covered with an inorganic layer 9M. The heat radiating plate is formed with a groove 11 having a cross-sectional shape that matches the cross-sectional shape of the inorganic layer. Considering the heat propagation here, the broken line Tn in the inorganic layer shows an isotropic curve in the inorganic layer, indicating that it is propagating isotropically from the heating element. Incidentally, the positional relationship between the platen 105, the heat-sensitive medium P, and the heating element is also shown for reference.

Next, in order to explain the cross-sectional configuration of FIG. 1B in more detail, FIG. 14 is a supplementary view schematically showing the state of heat propagation from the heating element of the thermal head substrate 1.
FIG. 14A is a diagram for explaining the cross-sectional structure and temperature propagation. FIG. 14 is a diagram for explaining that the platen 105 and the thermal paper P slide in pressure contact with the recess 8 of the glass substrate 3 and the thinned substrate 8a portion as the printer mechanism.

A heating element 29 (region 3A) of the substrate 3 is located directly below the center of the platen diameter, and an inorganic layer 9M) is formed so as to cover the heating element 29 (region 3A). A drive circuit forms a region 3B on the same main surface. Further, the heat radiating plate 4 having the groove 11 that fits into the protrusion of the inorganic layer 9M is adhered with the adhesive 5. The broken line Tn shown in the inorganic layer shows an isotropic curve and propagates isotropically in the inorganic layer 9M. With this configuration, since the three surfaces of the inorganic layer are surrounded by the heat sink 4, it is shown that the region other than the inorganic layer forming region is maintained at the heat sink temperature. By adjusting the width, thickness and position of the inorganic layer covering the heating element, the drive circuit forming region 3B can be brought closer to the inorganic layer 9 than originally requiring the same distance as the thickness of the inorganic layer.

Further to be described, FIG. 14B is a diagram for explaining the temperature propagation in a plane by looking at FIG. 14A from the upper side (platen 105 side). In order to explain the positional relationship of each element or region, it is a figure which shows the positional relationship which see through them. The dimension W1 indicates the distance from the end of the heating element 29 to the end of the drive circuit forming region 3B. Since the three surfaces of the inorganic layer are surrounded by a heat sink, this W1 originally requires dimensions equal to or greater than the thickness of the inorganic layer, but in this structure, W1 can be made almost zero in principle. However, in reality, the value is set to a constant value because the alignment error with the screen mask is taken into consideration for the formation of the inorganic layer.

Further, heat propagation from the heating element 29 on the surface of the substrate 3 for an arbitrary time during operation of the substrate for a thermal head will be described. The broken lines T0, T1, T2, T3 are isotemperature curves. The temperature becomes as low as T0>T1>T2> T3. It propagates isotropically in the transparent inorganic layer 9M region, but in the region without the inorganic layer 9, the temperature drops sharply to almost the same temperature as the heat sink 4. That is, the temperature of the drive circuit region 3B can be lowered and malfunction can be prevented. Further, it is a figure explaining that it is possible to miniaturize the depth W of the thermal head substrate with the distance W1 from the drive circuit forming region 3B being almost zero.
That is, until now, a distance of W1 equal to or greater than the thickness of the heat storage layer was required, but the drive element 28 can be brought closer to the inorganic layer forming region to reduce the size of the thermal head substrate. The thickness of the inorganic layer can be increased to a thickness having a heat capacity corresponding to the reduced W1.

Further, when the thickness of the inorganic layer is thin, the heat propagation distance in the creeping direction of the main surface of the substrate 3 is short, so that heat propagation is performed to the heat radiating plate without intentionally surrounding the periphery with the heat radiating plate. In this case, it can be configured with a flat heat sink.
Of course, the temperature of the drive circuit can also be controlled by forming the inorganic layer 9M thinly in the region corresponding to the drive circuit formation region 3B. Here, the region C represents a common electrode, and the region where the branch electrode 109 is formed is represented by D. The element that switches the heating element is represented by 28. The forming region of the heating element 29 is represented by 3A. The drive circuit forming region including the switching element is represented by 3B.

The substrate can be made of, for example, non-alkali glass, quartz (SiO2), silicon (Si), crystallized glass or the like. The thickness of the substrate can be, for example, 0.1 mm to 1.0 mm. The heat sink 4 can be made of aluminum, iron, SUS, amber material, or 42 alloy. As the heat sink, a metal having a thermal expansion rate almost equal to that of the substrate can be selected. The thickness of the heat sink 4 can be about 1 to 10 mm. This is because the heat capacity is changed according to the amount of heat generated. Further, the adhesive layer 5 can be made of an epoxy type. Particles such as alumina and silica may be mixed in order to enhance thermal conductivity. The thickness of the adhesive layer 5 can be, for example, about 5 μm to 100 μm.

In addition, the inorganic adhesive forming the inorganic layer is a fine powder of silica with a particle size of 2 to 10 μm, a viscosity of 10,000 CP, a 90th mesh for screen printing, and 150 degrees for one printing. It was formed by curing for 30 minutes. The thickness after curing was 50 μm, and immediately after application, it was about doubled to 100 μm. The thickness is adjusted by adjusting the viscosity of the inorganic adhesive, the mesh count of the screen plate, and the number of applications.
The thermal conductivity of the inorganic adhesive used in this example is 0.5w / m2k. The glass is 1,1w / m2k. The thickness of the inorganic layer that functions as a heat storage layer can be designed to be about half that of glass. Therefore, the thickness can be set to about 10 to 20 μm for high-speed printing and about 50 to 250 μm for low-speed printing.

Further, the bottom portion 8a of the recess 8 can also function as a wear-resistant layer for preventing the substrate from being worn when the heat-sensitive medium to be printed slides. Therefore, the bottom thickness 8a of the recess 8 is preferably thin in order to improve print quality, but preferably has a thickness of 2 μm or more in order to maintain mechanical strength. On the other hand, if the thickness of the bottom 8a of the recess 8 is too thick, the heat conduction from the heating element may deteriorate and the print quality may deteriorate. Therefore, the thickness of the bottom 8a of the recess 8 may be 100 μm or less. can.

FIG. 2 is a drawing showing the thermal head substrate 1 of FIG. 1 disassembled on the adhesive layer surface. 2A and 2B show a plan view and a cross-sectional view of the thermal head substrate 1. In the plan view and the cross-sectional view taken along the line X2a-X2a of FIG. It is a perspective view which shows that the formation region 9M is formed.

FIG. 2B illustrates a plan view of the heat sink 4 and a cross-sectional view taken along the line X2b-X2b. A groove 11 having a shape that matches the inorganic layer 9 is formed on the surface to be adhered to the main surface of the substrate 3, and the portion of the original thickness 3 of the substrate is exposed in the adhesive surface region other than the recess 8 and the formed portion. It has an opening 10 to be used. This is to withstand pressurization at the time of joining the cable 7 and the power supply and signal terminal of the board 3, and to secure the strength of the board after joining. Of course, the opening 10 may have a through-hole shape.

Further, the depth of the groove 11 is about 0.1 to 0.5 mm, and is secondarily determined by the thickness of the inorganic layer changing depending on the printing density and the application. The width is about 0.1 to 0.5 mm, which is the length that covers the heating element 29. Further, the cross-sectional shape can be made equal to the cross-sectional shape of the inorganic layer 9M, and can be made into a shape such as a square, a trapezoid, or a semicircle depending on the manufacturing method. For example, when screen printing is used, a semicircle is likely to be formed when a trapezoid is used for the trapezoid. Further, as a processing method, in the case of aluminum, grinding, pressing, extrusion molding and the like can be used. Further, when the thickness of the inorganic layer is thin, it can be composed of a flat heat sink.
Further, the outer shape of the heat radiating plate 4 can be made larger by about 0.1 to 1.0 mm than the outer shape of the substrate 3, and the end portion thereof after the glass substrate 3 is bonded can be made a size to prevent cracking or chipping from an external force.

FIG. 3 is a diagram schematically showing a substrate for a thermal head according to the present embodiment. FIG. 3A is a diagram showing the arrangement of the entire circuit pattern including the heat generating resistor 29, the drive circuit, the common electrode 106, the branch electrode 109, the terminal electrode 108, etc. on the substrate 3 of the all-thin film type thermal head substrate. Is. FIG. 3 (c) is a diagram showing an enlarged cross-sectional view of the line X3a-X3a of FIG. 3 (a). In FIG. 3B, glass, quartz, or the like can be used for the substrate 3 in the enlarged drawing of the peripheral portion of the heating element and the drive circuit. It is shown that the heating element 29 is formed of the active layer polysilicon 10a and is simultaneously formed in the manufacturing process of the thin film transistor constituting the drive circuit (in the figure, the joint portion of the electrode layer is "X". (Indicated by).

FIG. 4 can be a circuit diagram of the thermal head substrate used in the embodiment. A large number of heating elements can be connected between the power supply VH, (region C), and the ground electrode GH, (region D), through which a current flows through the heating element 29. One end of each heating element 29 can be connected to the common electrode C. The other end can pass through the branch electrode (its formation region E) and be connected to the individual switching elements 28. Then, the switching element 28 can be connected to a drive circuit that controls the on / off of the current and its time. The drive circuit can be composed of a serial-in and parallel-out shift registers-22, a gate circuit 27 for split printing, a data holding latch circuit 25, and a drive circuit power supply (not shown).

As the signal type, each signal terminal of the strobe 26 used for split printing, the latch 24 for holding data, the data 21, and the clock 23 can be derived. Generally, the circuit portion of the region 38 can be called a drive circuit. 3A indicates a region where the heat generation resistors 29 are arranged in a row, and 3B indicates a region where the drive circuit is arranged. The terminals of the above signals and the power supply are integrated at the terminal electrodes 108 and 108a in FIG. 3A. ing.

Further, heat propagation from the heating element 29 on the surface of the substrate 3 for an arbitrary time during operation of the substrate for a thermal head will be described. The broken lines T0, T1, T2, T3 are isotemperature curves. The temperature becomes as low as T0> T1> T2> T3. It propagates isotropically in the transparent inorganic layer 9M region, but in the region without the inorganic layer 9, the temperature drops sharply to almost the same temperature as the heat sink 4. That is, the temperature of the drive circuit region 3B can be lowered and malfunction can be prevented. Further, it is a figure explaining that it is possible to miniaturize the depth W of the thermal head substrate with the distance W1 from the drive circuit forming region 3B being almost zero.

7 (a) to 7 (e) show schematic views (plan view and cross-sectional view) for explaining a manufacturing process of a substrate for a thermal head. FIG. 7A is a diagram for explaining a thin film forming step for forming a heating element and a drive circuit on a substrate. FIG. 7B is a diagram for explaining an inorganic layer forming step for forming the inorganic layer. FIG. 7C is a diagram for explaining a heat sink bonding process for bonding and fixing the heat sink. FIG. 7D is a diagram for explaining a recess forming step for forming a recess on the substrate.

Further, FIG. 7E is a diagram for explaining an FPC forming process for forming a terminal cable made of an FPC (flexible printed circuit board) on a thermal head substrate. Further, in FIGS. 7 (c) to 7 (e), the heating element forming region 3A and the drive circuit forming region 3B show the positions where the heat radiating plate is seen through in order to show the positional relationship. Hereinafter, the manufacturing process of the substrate for the thermal head will be described in detail.
[Thin film forming process]

First, in FIG. 7A, a heating element 29 is formed in the heating element forming region 3A on the main surface of the substrate 3. Further, an electrode of a drive circuit and a signal terminal 108 for controlling a current flowing through the heating element 29 is formed in the drive circuit formation region 3B. After that, a protective film is formed on the surface of the uppermost layer.

3 (b) and 3 (c) are views showing the device configuration and arrangement formed on the glass substrate 3 in the thin film process. First, the polysilicon layer 29 was deposited on the glass substrate 3 by using the LPCVD method (low-pressure chemical-vapor deposition method). The thickness of the polysilicon layer 29 is about 1000 Å. Next, a photoresist is applied on the polysilicon layer 29, and the active region 10a of the heating element 29 and the thin film transistor (TFT) is applied to the region to be the heating element forming region 3A and the drive circuit forming region 3B by using photolithography technology. Formed a pattern for the drive circuit including.

Next, after forming the gate insulating film 206 (thickness of about 750 Å), the polysilicon layer (thickness of about 3000 Å) was deposited again. Next, the portion 205 to be the gate electrode of the thin film transistor was etched by using a photolithography technique to form a gate electrode 205 pattern.

Then, by sequentially ion-implanting phosphorus (P) and boron (B) into the polysilicon layer using an ion implantation method, the source region 203a of the C-MOS thin film transistor (TFT) constituting the drive circuit, and A drain region 207a was formed. At the same time, a heating element region 29 was formed. In the ion implantation step, impurities (phosphorus (P) or phosphorus (P) or The dose amount of boron (B) and the depth of ion implantation (ion acceleration energy, etc.) were controlled and adjusted.

Next, the interlayer insulating film 204 is formed by using the LPCVD method. The interlayer insulating film 204 is made of, for example, silicon dioxide (SiO ₂ ) and has a thickness of about 500 nm. Next, the interlayer insulating film 204 in the electrode forming region is etched by using a photolithography technique, a contact hole is opened, a multilayer electrode metal (Ti / Al / Ti) is formed by a sputter method, and then a lift-off method is used. The wires 106 and 109 were formed. The thickness of each metal layer of the multilayer electrode metal (Ti / Al / Ti) can be, for example, (Ti film 100 nm / Al film 800 nm / Ti film 100 nm).

Finally, the protective layer 209 was formed on the uppermost layer of the glass substrate 3. As the protective layer 209 (displayed only in FIG. 3C), for example, a silicon-based inorganic insulating film such as silicon nitride (SiN _x ) can be used, and the thickness can be about 1000 Å. Through the above steps, a heating element (resistor) and a drive circuit were formed on the glass substrate 3. In the present embodiment, the heating element (resistor) and the drive circuit are composed of the polysilicon layer 10a and are formed at the same time.

Further, since the manufacturing process of the array substrate of the liquid crystal display element can be applied, the mass production effect is large. Further, as the resistor material constituting the heating element, a Ti metal layer can be used in addition to the polysilicon layer.
Of course, it is also possible to form a film of another material such as TaSiO2, NiCr, TaN as a heating element, form a pattern, and then form the thin film in the above-mentioned thin film forming step.

An example of the specifications of the thermal head substrate and the structure of the heating element formed in the thin film forming step shown in FIG. 7A is shown below.
-Print width: 3 inch
・ Total number of heating elements per line: 304 dots / line
・ Heating element density: 4dot / mm
・ Pitch of heating element: 125 μm
・ Size of heating element ((width W * length L): 100 μm) * 130 μm
-External size of the board: L = 80mm, W = 10mm
Further, as an example of the dimensions of each part shown in FIG. 3A, the following numerical values were used.
・ L1 = 76mm, W1 = 0.1mm (constant), W2 = 2mm, W3 = 2mm
Further, the glass substrate 3 is, for example, a so-called glass substrate for a liquid crystal substrate, which is made of non-alkali glass and has a thickness of 0.5 mm. The above process is known as an array process of LTPS TFT at the time of manufacturing a liquid crystal display element.

Further, by increasing the thickness of the common electrode and the branch electrode on the substrate after the completion of the thin film forming process by using electroless or electroplating, the electrode width can be narrowed without changing the wiring resistance, so that the area occupied by the electrode is occupied. Can be reduced and the size of the thermal head substrate can be reduced. This is because, in the thermal head substrate 1, the wear-resistant layer is not formed by laminating on the electrodes, so that the uneven wear of the wear-resistant layer caused by the electrode thickness is not a concern, and the electrode thickness is arbitrary. This is because the thickness is possible.

Now, in the specifications of the thermal head substrate shown above, it will be described that the substrate depth dimension W can be further reduced from 10 mm to 7 mm. The method is to make the wiring resistance equal by increasing the thickness of the electrode layer by 4 times or more. As a result, W2 and W3 of the specified dimensions can be reduced to 0.5 mm, which is about a quarter of each.

In the method, in FIG. 3, Cr and Cu plating can be further performed on the electrodes of the thermal head substrate after the thin film forming step, and Cr can be formed in an amount of 0.1 μm and Cu can be formed in an amount of 4 μm. As the method, electroless electroless and electroplating methods can be used. The plated portion is on the electrode 109 in which the common electrode 106, the branch electrode forming region 109a, and the individual branch electrodes are integrally connected. Therefore, a window opening pattern is applied to the SiNx film 209 of the protective film on the SiNx film 209 portion on the electrode 109 in which the common electrode 106, the branch electrode forming region 109a, and the individual branch electrodes are integrally connected by using a photosensitive resist. After removing the SiNx film by plasma etching, Cr + Cu plating treatment can be performed to form Cr of 0.1 μm and Cu of 4 μm. By the way, if the thickness of the electrode is 1 μm or less, the wiring resistance becomes large, which is not practical. Further, when the thickness is 50 μm or more, the adhesion is deteriorated and it is easy to peel off, which has a limit.
[Inorganic layer forming process]

Next, with reference to FIG. 7B, an inorganic layer forming step for forming an inorganic layer that functions as a heat storage layer will be described. As shown in FIG. 7B, the inorganic layer 9 is formed in the heating element forming region 3A on the main surface of the glass substrate 3. In the present embodiment, the inorganic layer is formed so as to cover the heating element in the heating element forming region 3A, and can form the inorganic layer 9M. Further, the inorganic layer 9 can be formed in a region other than the heating element forming region 3A.

By forming the inorganic layer 9M, it is possible to provide a substrate for a thermal head suitable for high-speed and low-speed printing applications by controlling the amount of heat storage. Further, since the heating element 29 has high heat resistance and is hard, even if the heating element 29 is instantly heated to a high temperature, deterioration or softening does not occur, and good contact sliding of the heat-sensitive medium can be maintained to maintain print quality.

Further, the inorganic layer 9M can be used, for example, an inorganic adhesive mixed with a powder of alumina or silica, and is formed by a dispenser or screen printing.
A 0.2 mm wide line is formed on the main surface of the heating element forming region 3A using an inorganic adhesive. The length RL of the heating element pattern is 130 μm, and the width is determined in consideration of the alignment error at the time of printing, and the design is such that the entire surface is covered.

The inorganic adhesive was a fine powder of silica having a particle size of 2 to 10 μm, a viscosity of about 10,000 CP, and was formed by using a No. 90 mesh for screen printing and curing at 150 ° C. for 30 minutes with a single application. The thickness after curing was 50 μm, and immediately after application, it was about double to 100 μm. The thickness can be adjusted by adjusting the viscosity of the inorganic adhesive, the mesh count of the screen plate, and the number of applications.
In addition, room temperature cured glass can also be used as the inorganic layer. It can be vitrified by applying liquid glass and drying at room temperature, eliminating the need for high-temperature treatment.
The thermal conductivity of the inorganic adhesive used in this example is 0.5w / m2k. The glass is 1,1w / m2k. The thickness of the inorganic layer that functions as a heat storage layer can be designed to be about half that of glass.
[Heat sink bonding process]

Next, the heat sink bonding process will be described with reference to FIG. 7 (c). As shown in FIG. 7 (c), the heat radiating plate 4 is adhered to the glass substrate 3 using the adhesive 5. First, the adhesive 5 is applied in advance to the adhesive surface for adhering the heat radiating plate of the glass substrate 3 using a dispenser or the like. In the present embodiment, after the inorganic layer forming step, the adhesive 5 is applied on the three glass substrates on the main surface of the glass substrate 3 with a spencer.

Next, the heat radiating plate 4 was pressed against the adhesive surface to which the adhesive 5 was applied, and in that state, it was heated at a temperature of 150 degrees for 10 minutes to cure and bond the adhesive 5. The heat sink 4 is made of, for example, aluminum, and its thickness can be, for example, about 1.0 mm. Further, as the adhesive 5, for example, an epoxy adhesive mixed with alumina particles can be used. The thickness of the adhesive material 5 after the heat radiating plate 4 is adhered is about 10 μm, and the thinner the adhesive material 5, the more preferable the thickness. Further, as the adhesive 5, for example, an epoxy adhesive having a high thermal conductivity and used as a liquid underfill material can also be used.

Further, in the present embodiment, since the heat generation resistor portion of the high temperature portion is covered with an inorganic layer 9M generally made of an inorganic substance having high heat resistance, the adhesive 5 has a relatively low heat resistant temperature. Adhesives can be used. Further, the heat radiating plate 4 is provided with an opening 10 so that the signal terminal lead-out portion 108 is exposed. Since this opening is the original thickness portion of the glass substrate 3 because the thickness of the glass substrate 3 is not reduced in the subsequent recess forming step, it has sufficient strength to withstand the thermocompression bonding of the FPC. .. Further, the structure in which the heat radiating plate 4 and the glass substrate 3 are bonded to each other increases the strength and can function as a backing reinforcing material for the bottom of the thinly processed recess when the recess is formed in the next recess forming step.
[Recess forming process]

Next, the recess forming step will be described with reference to FIG. 7 (d). The thin film portion 8a at the bottom of the recess 8 is a portion to be a wear-resistant layer. On the back surface facing the main surface of the glass substrate 3, a recess is formed in the region to be the wear-resistant layer forming region 8. The region forming the recess depends largely on the diameter of the platen. For example, when the diameter is 16 mm, it can be a region of +/- 2 mm and a width of 76 mm from the center of the heating element row A in FIG. 7 (d). In the present embodiment, the back surface of the glass substrate 3 can be etched to form a recess. By forming the concave portion by etching, it is possible to perform flat processing with high processing accuracy and no processing distortion.

The process of the recess forming step will be described below. First, in order to protect the surface on the side of the heat radiating plate 4 to which the glass substrate 3 and the heat radiating plate 4 are adhered and united from the etching solution, a resist is spray-coated on the entire surface thereof. After that, a photosensitive resist is spray-coated on the entire surface of the glass substrate 3 side, and each step of baking, exposure, development, and post-baking is performed using photolithography technology to form a pattern for the recess forming region. Form. This recess forming region corresponds to the wear resistant layer forming region 8. Next, it was immersed in a hydrofluoric acid (HF) solution for about 50 hours and etched to a depth of about 480 μm. The thickness 8a of the glass substrate 3 in the recess forming region of FIG. 7D is about 10 μm.

Further, as the resist to be applied to the surface on the glass substrate 3 side, a film resist or the like can be used in addition to the photosensitive resist. As a resist coating method, dip coating, spray coating, screen printing and the like can be used. The thickness (remaining thickness after etching) 8a of the glass substrate 3 in the recess 8 can be 210 μm or more. The recess 8 (or the recess forming region) functions as a wear resistant layer. This etching process is the same as the slimming process in the liquid crystal display element manufacturing process.

Next, a step of dividing the thermal head substrate into individual pieces (not shown) will be described.
The following two methods can be adopted for the individual piece dividing step.
First, a method of dividing the mother glass substrate 3 into individual pieces and then adhering the heat radiating plate 4 will be described. As shown in FIG. 10A, the substrate 1 after the thin film forming step is shown on the main surface of the mother glass 3a. Three patterns of the thermal head substrate 1 are impositioned. This is a method in which a scribe line S is formed around each substrate 3, divided by a scriber along the scribe line S, separated into individual pieces, and then bonded to the heat radiating plate 4. Of course, a dicer of a grinding device can be used.

On the other hand, as shown in FIGS. 10 (b) and 10 (c), after the plurality of heat sinks 4 are bonded (FIG. 10 (b)), the mother glass substrate 3 is divided (FIG. 10 (c)). It can also be individualized. Further, FIG. 10D shows a plan view and a cross-sectional view of the heat radiating plate 4. A heat radiating plate 4 having a thin periphery and having a flanged 4a is adhered. The height h4 of the collar is set to about 0.1 mm to 0.5 mm. The width w4 is set to about 0.1 mm to 1.0 mm. The setting is such that the end portion of the thermal head substrate 1 does not protrude from the heat sink. Then, as shown in FIG. 10 (c), the main surface of the mother glass substrate 3 was scribed along a scribe line S provided in advance, and the mother glass substrate 3 was divided into individual pieces. The effect of providing this collar is that even if the adhesive sticks out at the end, it can be divided smoothly, and it goes without saying that the heat sink may have no collar.

The method of dividing the mother glass substrate 3 into individual pieces after adhering the heat radiating plate 4 is advantageous in terms of cost when more imposition is performed using a large glass substrate. FIG. 13 shows a completed outline view of the thermal head substrate when the flanged heat sink is used. It is shown that the flange 4a of the heat radiating plate 4 can protect the end portion of the glass substrate 3 from external force and prevent cracking and chipping.
[Terminal cable forming process]

Next, the terminal cable forming process will be described with reference to FIG. 7 (e). As shown in FIG. 7 (e), the FPC is thermocompression-bonded with ACF (an anisotropic conductive film) as a terminal cable. As the FPC, for example, a polyimide sheet (thickness 50 μm) formed with a flash gold-plated copper thickness of 18 μm as wiring can be used. ACF was pressure-bonded at 180 ° C. for 5 seconds at a pressure of 3 MPs and cured by heating.
The thermal head substrate 1 is completed by the above steps.
[Example 1]

FIG. 1 is a diagram schematically showing a substrate 1 for a thermal head according to the first embodiment. The substrate 3 and the heat sink 4 are adhered to join the terminal cable to the electrode terminal portion where various signals and power supply terminals are arranged. FIG. 2 is a drawing illustrating the configuration of the completed thermal head substrate 1 of FIG. 1 by disassembling it into a substrate 3 on which a heating element and a drive circuit thereof are formed and a heat sink 4. In FIG. 2A, a recess 8 is formed on the back surface of the substrate 3 of the thermal head substrate 1, and an inorganic layer is formed on the main surface of the substrate 3 so as to cover the heating element. The heating element forming region 3A, the drive circuit forming region 3B, and the inorganic layer forming region 9M show a positional relationship in which the substrate 3 is seen through. As shown in FIG. 2B, the heat radiating plate 4 has a groove that fits into the cross-sectional shape of the inorganic layer, and is positioned at a predetermined position in order to expose the terminal electrodes arranged on the main surface of the substrate 3. Has an opening.

FIG. 3 is a diagram showing the elements and pattern arrangement of the substrate which has completed the thin film forming process in which the heat generation resistor and the drive circuit of the substrate for the thermal head are formed. The drive circuit is composed of thin film transistors.
The thickness 8a at the bottom of the recess is 2 to 50 μm, and if the thickness is 2 μm or less, it becomes difficult in terms of manufacturing variation. If the thickness is 50 μm or more, the printing will be blurred and the quality will be significantly deteriorated. The adhesive layer is a thin adhesive having a high thermal conductivity of about 5 to 50 μm.

Further, FIG. 8A shows dimensional examples of each part of this embodiment of L1 to L8 parts. L1 is the width of the inorganic layer of 0.3 mm, L2 is the thickness of the adhesive layer of about 10 μm, L3 is the length of the heating element (RL) of 0.13 mm, and L4 is the distance between the end of the heating element and the end of the drive circuit forming region. 0.1 mm, L5 is the width of the recess, +/- 2.0 mm (4.0 mm) from the center of the heating element, L6 is the thickness of the bottom surface of the recess (wear resistant layer), 10 μm, and L7 is the thickness of the glass substrate. 0.5 mm and L8 are 50 μm in thickness of the inorganic layer.
[Example 2]

8 (b), (c), (d), and FIG. 9 are views schematically showing the thermal head substrate 301 of the second embodiment. This is an application example in which the thermal time constant in the drive circuit formation region is changed by the inorganic layer. An inorganic layer can also be formed in this region and the thickness can be changed to change the thermal time constant in that region. FIG. 8B shows a configuration diagram in which an inorganic layer is formed so as to cover not only the heating element portion but also the drive circuit portion. FIG. 8C shows a cross-sectional view of a thermal head substrate when the thickness of the inorganic layer covering the heating element is thin. FIG. 8D shows a cross-sectional view of a substrate for a thermal head in which inorganic layers are provided at a plurality of locations. 9 (a) to 9 (d) show a plan view of a substrate for a thermal head, and FIGS. 9 (e) to 9 (j) are views showing an outline of a cross-sectional view corresponding to each plan view. For example, the cross-sectional views taken along the line X9b-X9b in FIG. 9B are (f) and (i).

In the substrate for a thermal head, the thickness of the inorganic layer is about 10 to 40 μm for high-speed printing, about 40 to 100 μm for medium-speed printing, and about 100 to 500 μm for low-speed printing, which are designed as empirical values. When the thickness is thin for high-speed applications, the region where the inorganic layer is formed is expanded to the region where the drive circuit is formed, and the depth of the groove of the heat sink becomes shallow, so that a flat plate heat sink without a groove can be used.
In FIG. 8B, the thickness of the inorganic layer is thin in the drive circuit region 9Ma, and the heating element portion 9M is formed thick. In particular, when the thickness of the substrate 8a is as thin as several μm, it is possible to prevent the substrate 8a from being deformed by the pressure due to the platen.

Further, in the step of forming the inorganic layer, the inorganic layer can be formed by dividing it into a thin layer and a thick layer by using screen printing technology. Further, FIG. 8C shows an example of a thermal head substrate shown for high-speed printing. In FIG. 8C, since the flat plate heat sink 4 is used to form the inorganic layer 9M having a uniform thickness in the drive circuit forming region, the effect of the reinforcing material of the thinned substrate 8a is given. Can be done.

Further, when it is necessary to make the thickness of the adhesive layer uniform in order to make the thermal resistance uniform, the inorganic layers 9M are formed at a plurality of places (two places in this embodiment) as shown in FIG. 8D. You may. As the heat sink, a heat sink on a flat plate without a groove can be used, and the thickness of the inorganic layers provided at a plurality of places acts as a spacer at the time of adhesion. As a result, the thickness of the adhesive layer can be made uniform while maintaining the parallelism between the substrate 3 and the heat sink 4.

FIG. 9A is a diagram showing an example in which the inorganic layer 9M is formed at two locations. In FIG. 9A, one of the inorganic layers 9M is formed linearly so as to cover the heating element forming region 3A. On the other hand, the other inorganic layer 9Ma is formed on the drive circuit forming region 3B. The inorganic layer 9M can be formed at an arbitrary position on the substrate 3.

FIG. 9B shows an example in which the inorganic layer 9M is formed at one location. 9 (f) and 9 (i) are views showing examples of changes in the cross-sectional shape of the inorganic layer 9. FIG. 9 (f) is a cross-sectional view of a thermal head substrate formed by using screen printing technology. Further, FIG. 9 (i) shows a cross section of the thermal head substrate when formed by spencer coating. Depending on the cross-sectional shape of the inorganic layer, the shape of the groove of the heat sink that fits into it can be selected.

9 (c), 9 (g), and 9 (j) are diagrams illustrating examples in which the thickness and formation region of the inorganic layer 9M are changed. The inorganic layer 9Ma is formed thinner than 9M and its thickness controls the thermal resistance. FIG. 9 (j) shows an example in which the inorganic layer is formed in the drive circuit forming region when the thickness of the inorganic layer is thin.
9 (d) and 9 (h) are a plan view and a cross-sectional view of an example in which the drive circuit is arranged separately for each block and the inorganic layer 9Mn is formed for each block.
As described above, the thermal time constants of the heating element forming region and the drive circuit forming region can be controlled by changing the thickness of the inorganic layer and the coating area.

As described above, FIG. 11 is a diagram illustrating the shape of the heat radiating plate having a groove aligned with the cross section of the inorganic layer. FIG. 11 is a diagram showing an example of the shape of the heat radiating plate corresponding to the example of cross-sectional deformation of the inorganic layer. Further, FIG. 11A is an example in which an inorganic layer is formed in one place, and FIG. 11B is an example in which an inorganic layer is formed in a plurality of places.
In addition, although not shown, it is of course possible to implement a flat plate-shaped heat sink or other groove-shaped heat sink.
[Example 3]

FIG. 12 is a diagram schematically showing the thermal head substrate 401 of the third embodiment. When continuous printing continues on the glass substrate 3, heat storage occurs. Therefore, it is necessary to reduce the heat capacity in the area of the original thickness of the glass substrate to prevent heat storage. Next, a thermal head substrate capable of reducing the heat capacity in the region of the glass substrate other than the recess forming region will be described below.

FIG. 12 shows an embodiment of a thermal head substrate having several differently shaped recesses. 12 (a) to 12 (d) show an overall schematic plan view of a substrate for a thermal head, and are views showing the positions of a heating element forming region 3A and a drive circuit forming region 3A as seen through. 12 (e) to 12 (i) show cross-sectional views of each plan view. For example, the cross-sectional views taken along the line X12b-X12b of the plan view of FIG. 12B are FIGS. (F) and (i).
First, there are roughly two types of shapes of the recess 8 as seen from the plan view. 12 (a) to 12 (c) show a so-called counterbore-shaped recess 8, and FIG. 12 (d) shows a recess 8 having a groove shape.

A substrate for a thermal head having a counterbore-shaped recess has the advantage of increasing strength, but it is necessary to fit the platen in the recess. On the other hand, in the thermal head substrate having a groove-shaped recess, the strength of the substrate 3 is slightly inferior, but there is no limitation on the length of the platen, and there is a margin in the design of the printer mechanism.
Next, FIGS. 12 (a) and 12 (e) show a substrate for a thermal head in which a plurality of recesses are provided to increase the surface area of the substrate 3 and improve heat dissipation. In FIG. 12 (e), a plurality of counterbore 8a are formed in a region of the substrate 3 which does not cause any trouble other than the terminal electrode terminal forming region. In addition, although the case where the concave portion 8 has a spot facing shape is shown in FIG. 12 (e), it may have a groove shape.

12 (f) and 12 (i) show an example in which the recess has a thickness different from that in the case of a uniformly thin thickness. In the thermal head substrate shown in FIGS. 12 (f) and 12 (i), the area other than the terminal forming area on the main surface is thinned on the opposite surface of the area other than the heating element forming region 3A and the drive circuit forming 3B on the main surface. It can have a recess 8. In particular, in the thermal head substrate shown in FIG. 12 (i), since the protrusions are formed only on the heating element forming region 3A, the contact property due to biting into the heat sensitive medium can be improved. As a result, the print quality can be improved. The thermal head substrate shown in FIGS. 12 (c) and 12 (g) can have a spot facing recess 8n in an island shape for each drive circuit block. The thermal head substrate shown in FIGS. 12 (d) and 12 (h) has a groove-shaped recess 8. In the thermal head substrate shown in the cross-sectional view (plan view not shown) shown in FIG. 12 (j), it is possible to design a mechanism in which an L-shaped groove is formed to increase the degree of freedom of the traveling path of the heat-sensitive medium. can.

As shown in FIG. 12, recesses having various different shapes can be applied to the recesses of the thermal head substrate. In the step of forming the recess 8, for example, an etching method can be used. However, in the case of a portion or structure that cannot be formed by the etching method alone, a processing method such as grinding or sandblasting can be adopted. The important thing is to remove the processing strain by etching as the final finish. This is because if processing strain remains, chips or cracks will occur in the temperature cycle during operation of the thermal head substrate, resulting in malfunction.

1,301,401 Thermal head substrate 3 Substrate 3A Heating element formation region 3B Drive circuit formation region
4 Heat sink 5 Adhesive layer 6 ACF (anisotropic conductive film)
7 FPC (terminal cable)
8 Recess 9 9M, 9Ma Inorganic layer
11 groove

Claims (6)

A substrate having a main surface and a heating element forming region and a drive circuit forming region,
A heating element and a drive circuit integrally formed in each region of the heating element forming region and the driving circuit forming region on the main surface.
A wiring formed on the main surface for connecting the heating element and the drive circuit,
A heat storage layer containing an inorganic layer formed on the heating element forming region,
A heat sink provided on the heat storage layer is provided.
The inorganic layer constituting the heat storage layer contains granular alumina or silica having a particle size of 1 μm or more and 100 μm or less.
It is a back surface facing the main surface of the substrate and has a recess in a region corresponding to the heat storage layer.
A substrate for a thermal head, wherein the recess functions as a wear-resistant layer.
The substrate for a thermal head according to claim 1, wherein the heat storage layer is formed by covering the heating element.
The substrate for a thermal head according to claim 1 or 2, wherein the thickness of the substrate in the recess is 2 μm or more and 100 μm or less.
The substrate for a thermal head according to any one of claims 1 to 3, wherein a recessed groove is provided in a region corresponding to the heat storage layer on the back surface of the substrate.
The heating element has a plurality of heat generating parts and has a plurality of heat generating parts.
One end of the plurality of heat generating portions is connected to a common electrode.
Each of the other ends of the plurality of heat generating portions is connected to a corresponding branch electrode.
The substrate for a thermal head according to any one of claims 1 to 4 , wherein the thickness of the common electrode and the branch electrode is 1 μm or more and 50 μm or less.
A step of forming a heating element, a drive circuit, and wiring for connecting the heating element and the integrated circuit on the main surface of the substrate.
A step of forming a heat storage layer including an inorganic layer covering the heating element, and
The process of adhering the heat sink to the surface of the heat storage layer and
After the step of adhering the heat radiating plate, a step of forming a recess in a region of the back surface of the substrate facing the main surface corresponding to the heat storage layer is provided.
A method for manufacturing a substrate for a thermal head , wherein the inorganic layer constituting the heat storage layer contains granular alumina or silica having a particle size of 1 μm or more and 100 μm or less .

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