JP2012206298A - Thermal head, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain power consumption while improving print quality in a thermal head.SOLUTION: A heating element plate 20 comprises: a heat insulation layer 22b formed on the surface of an insulation plate 22a so as to form a hollow extending in a main scanning direction; a heat generation part 23b formed on the surface of the heat insulation layer which generates heat due to a flow of an electric current in the upper part of the hollow A; and a thermal conductor provided in the hollow A and forming a gap between the heat generating part and the insulation plate at a normal temperature state. Heat is hardly dissipated at a normal temperature state, thus improving a heat accumulation function.

Description

  The present invention relates to a thermal head and a manufacturing method thereof.

  The thermal head generates heat on the heating portions of a plurality of heating resistors arranged in a direction (main scanning direction) orthogonal to the direction in which the printing medium such as thermal recording paper is conveyed, and the heat causes characters on the printing medium. This is an output device for forming images such as images and figures. This thermal head is widely used in recording devices such as a barcode printer, a digital plate making machine, a video printer, an imager, and a seal printer.

  A general thermal head includes a heat radiating plate, a heat generating plate attached to the heat radiating plate, and a circuit board attached to the heat radiating plate on the same side as the heat generating plate. Heat generating resistors are linearly arranged at predetermined intervals in a heat generating region extending in a band shape on the surface opposite to the surface of the heat generating plate opposite to the heat radiating plate. Also, a driver IC (Integrated Circuit) that is a part of a drive circuit that drives the heating resistor is mounted on, for example, a heating plate.

  A conventional thermal head heating plate will be described with reference to FIG.

  The support substrate 122 includes an insulating plate 122a and a heat insulating layer 122b formed in a layered manner on the upper surface of the insulating plate 122a. A heating resistor layer 23 constituting a plurality of heating resistors is provided on the upper surface of the support substrate 122, and a plurality of electrodes 28 are provided on the upper surface of the heating resistor layer 23. The electrode 28 includes an individual electrode 28a and a common electrode 28b. A gap having a predetermined length is formed between the individual electrode 28a and the common electrode 28b, and the current flowing through the common electrode 28b flows to the individual electrode 28a through the heating resistor layer 23 at the gap portion. The heating resistor layer 23 functions as the heating portion 23b. A protective layer 29 made of an insulating material that protects the heat generating portion 23b is formed on the upper surface of the heat generating portion 23b (see, for example, Patent Document 1).

  In such a configuration, when printing on the printing medium, the thermal printer moves the printing medium in the sub-scanning direction orthogonal to the main scanning direction along the heat generation area 24. At the same time, the thermal head generates heat by supplying a current to the heat generating portion 23b, and prints on the printing medium with the heat.

JP 2008-132635 A

  As described above, the thermal head has a structure in which the heat generating portion 23b generates heat and prints on the printing medium. Therefore, the heat generation state of the heat generating portion 23b, for example, the heat history of the heat generating portion 23b, etc., affects the printing on the printing medium.

  For example, the heat insulating layer 122b provided on the support substrate 122 has a heat storage function for the heat generating portion 23b. When the heat storage function of the heat insulating layer 122b is high, the power for heating the heat generating portion 23b is small when the next line is printed, so that energy efficiency is good and power consumption can be suppressed.

  However, when the heat storage function becomes high, the temperature drop from the peak temperature during heat generation becomes insufficient. For this reason, blurring or tailing occurs during printing, cutting of the printing becomes worse, and the printing quality may be deteriorated.

  Therefore, the heat retaining layer 122b is also required to have a certain heat dissipation function. For example, when the heat insulating layer 122b is formed thin to reduce the heat storage function, the heat dissipation function is increased, and thus the thermal response is improved. However, in this case, when printing the next line, it is necessary to input high power, and the power consumption increases.

  Thus, the heat retaining layer 122b is required to have a contradictory function of a heat storage function and a heat dissipation function. By maintaining such a function in a well-balanced manner, it is possible to suppress power consumption while improving the print quality of the thermal head. desirable.

  Accordingly, an object of the present invention is to suppress power consumption while improving the printing quality of a thermal head.

  In order to solve the above-described problems, the present invention provides an insulating plate, a heat insulating layer provided on the surface of the insulating plate, and a heat generating portion that is formed on the surface of the heat insulating layer and generates heat when current flows. In the thermal head provided, a cavity is formed between the heat generating part and the insulating plate, and the room is disposed in the cavity so as to form a gap between the heat generating part and the insulating plate in a room temperature state. It comprises a heat conductor.

  According to the present invention, in the method for manufacturing a thermal head, a first step of attaching a heat conductor extending in a strip shape in a main scanning direction orthogonal to a direction in which a printing medium is conveyed to the surface of an insulating plate; and the first step A second step of attaching a heat insulating layer made of a material having a softening point higher than the melting point of the heat conductor to the surfaces of the insulating plate and the heat conductor; and after the second step, the heat insulating layer. A third step of heating the insulating plate and the thermal conductor so as to exceed a softening point, and a fourth step of cooling the insulating plate and the thermal conductor so as to fall below the melting point of the insulating plate after the third step. And a process.

  According to the present invention, it is possible to suppress power consumption while improving print quality in a thermal head.

It is a fragmentary sectional view of the heat generating body board in one embodiment of the thermal head concerning the present invention. It is a partially cutaway top view in an embodiment of a thermal head according to the present invention. 1 is a cross-sectional view of a part of a thermal printer using an embodiment of a thermal head according to the present invention. It is a fragmentary sectional view in the high temperature state of the heat generating body board in one embodiment of the thermal head concerning the present invention. It is a flowchart of the manufacturing method in one Embodiment of the thermal head which concerns on this invention. It is a fragmentary sectional view of the heat generating body plate of the conventional thermal head.

  An embodiment of a thermal head according to the present invention will be described with reference to the drawings. This embodiment is merely an example, and the present invention is not limited to this.

  As shown in FIGS. 1, 2, and 3, the thermal head 10 according to the present embodiment includes, for example, a heating plate 20, a circuit board 40, and a heat radiating plate 30. The heat generating plate 20 is formed with a heat generating region 24 extending in a strip shape. The heating plate 20 is placed on the heat sink 30. The heat sink 30 is a plate formed of a metal such as aluminum. A control signal and driving power for forming a predetermined heat generation pattern in the heat generation region 24 are input to the circuit board 40 and further input to the heating element plate 20 electrically connected to the circuit board 40.

  A thermal printer using the thermal head 10 has a platen roller 50 formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller 50 has a shaft 52 on a straight line parallel to the main scanning direction dm. Further, the side surface of the platen roller 50 is disposed so as to be in contact with the heat generating region 24, and is provided to be rotatable about the shaft 52.

  As the platen roller 50 rotates, the thermal recording medium 60 inserted between the platen roller 50 and the heat generating area 24 moves in the sub-scanning direction ds. The heat-sensitive recording medium 60 is, for example, heat-sensitive recording paper that develops color when heated to a color development temperature or higher.

  The thermal printer presses the thermal head 10 against the platen roller 50 by a head pressing portion (not shown) constituted by a drive motor, thereby pressing the heat generating area 24 against the thermal recording medium 60 and applying a nip pressure.

  At the same time, the thermal printer moves the thermal recording medium 60 in the sub-scanning direction ds and changes the heat generation pattern of the heat generating area 24 with the movement of the thermal recording medium 60, thereby forming a desired image on the thermal recording medium 60. To do.

  The heating element plate 20 includes a support substrate 22, a heating resistor layer 23, an electrode 28, and a protective layer 29.

The support substrate 22 has, for example, a ceramic insulating plate 22a such as alumina (Al ₂ O ₃ ), and a heat insulating layer 22b called a glaze layer formed in a layer shape with a thickness of 25 μm on the upper surface of the insulating plate 22a. is doing. The heat insulating layer 22b is formed of, for example, silicon oxide (SiO ₂ ). Further, a protrusion 21 having a width of 2 mm and extending in the main scanning direction dm is formed on the heat retaining layer 22b.

The heating resistor layer 23 is formed in a layer on a part of the upper surface of the heat insulating layer 22b, for example, with a cermet such as TaSiO ₂ . In the heating resistor layer 23, a plurality of heating resistors 23a are arranged at intervals in the main scanning direction dm. The heating resistors 23a extend in the sub-scanning direction ds across the ridges 21, respectively.

  The electrode 28a and the electrode 28b are formed on the upper surface of the heating resistor layer 23 in layers, for example, aluminum (Al). The electrode 28a and the electrode 28b are disposed to face each other so as to sandwich a gap having a predetermined length from the sub-scanning direction ds.

  The electrode 28 a is connected to the driver IC 42 on the circuit board 40 via the bonding wire 44. A predetermined voltage is applied to the electrode 28 b via the bonding wire 44. The driver IC 42 and the bonding wire 44 are sealed with a resin 48.

  Since the current flowing through the electrode 28b passes through the heating resistor 23a in the gap portion located between the electrodes 28a and 28b, the heating resistor 23a in the gap portion functions as the heating portion 23b. The heat generating portions 23b are arranged at intervals in the main scanning direction dm and form heat generating regions 24 extending in the sub scanning direction ds.

  The electrode 28 and the heating resistor layer 23 are covered with a protective layer 29. Protective layer 29 is made of, for example, silicon oxynitride (SiON).

  In the heat insulating layer 22b, a cavity A having a predetermined volume is formed in a portion of the ridge 21 immediately below the heat generating region 24, except that a portion in contact with the insulating plate 22a extends in the main scanning direction dm. The cavity A is surrounded by the inner wall of the heat insulating layer 22b and the upper surface of the insulating plate 22a.

  Inside the cavity A, a heat conductor 25 made of aluminum having a higher thermal expansion coefficient and a higher heat conduction coefficient than the heat insulating layer 22b and having a melting point lower than the softening point of the glass forming the heat insulating layer 22b is 1 mm wide. The thickness is 15 μm so as to extend in the main scanning direction dm.

  The heat conductor 25 is in contact with the upper surface of the insulating plate 22a, and the heat generating portion 23b is not controlled to generate heat, and in a normal temperature state where the temperature is not high, the volume is formed smaller than the volume of the cavity A. The upper surface is not in contact with the inner wall of the heat insulating layer 22b. Thus, the heat conductor 25 forms a gap between the heat generating portion 23b and the insulating plate 22a in the normal temperature state.

  The space between the heat conductor 25 and the inner wall of the heat insulating layer 22b is filled with a gas having a lower thermal conductivity than the heat insulating layer 22b, for example, air.

  Here, in the normal temperature state, the heat conductor 25 is not in direct contact with the inner wall of the heat insulating layer 22b. For this reason, out of the plurality of heat generating portions 23b arranged in the main scanning direction dm, the heat of the heat generating portion 23b in the normal temperature state is difficult to conduct from the heat insulating layer 22b directly below to the heat conductor 25.

  That is, the thermal impedance from the heat insulation layer 22b to the air in the cavity A is high, and much heat is stored in the heat insulation layer 22b as in the case where the heat insulation layer 22b is thickened. For this reason, in the normal temperature state, the heat storage function in the heat insulating layer 22b is enhanced, and the energy efficiency (concentration efficiency) is increased.

  On the other hand, when the heat generating portion 23b is controlled to generate heat and becomes a high temperature state, the heat conductor 25 located immediately below the heat generating portion 23b is heated to high temperature through the heat insulating layer 22b, the insulating plate 22a, and the like. For this reason, the heat conductor 25 expands, and the cavity A located immediately below the heat generating portion 23b generating heat is filled with the heat conductor 25 as shown in FIG. That is, the heat conductor 25 is in contact with the heat insulating layer 22b and the insulating plate 22a. At this time, the air filled in the gap between the inner wall of the heat retaining layer 22b and the heat conductor 25 moves to a hole or the like formed inside the insulating plate 22a. The high temperature state refers to a state at a temperature equal to or higher than the temperature at which the heat generating portion 23b prints a density of 70% of the maximum density, for example.

  In this case, the heat generated in the heat generating portion 23b is directly conducted from the heat insulating layer 22b to the heat conductor 25 and then conducted to the insulating plate 22a.

  Here, since the heat conductor 25 made of aluminum has a higher thermal conductivity coefficient than the heat insulating layer 22b made of silicon oxide, heat is easily conducted from the heat insulating layer 22b to the heat conductor 25. That is, the thermal impedance from the heat insulating layer 22b to the heat conductor 25 is low, and heat is conducted through the heat insulating layer 22b, the heat conductor 25, and the insulating plate 22a and quickly radiated by the heat radiating plate 30. For this reason, the heat generating body plate 20 shows high thermal responsiveness similarly to the case where the heat insulating layer 22b is thinned, and the heat dissipation function is enhanced.

  Further, when the temperature of the heat generating portion 23b is lowered thereafter, the heat conductor 25 located immediately below the heat generating portion 23b contracts and returns to the cross-sectional area in the room temperature state. There is a state in which there is a gap between 25 and the heat insulating layer 22b.

  At this time, as described above, much heat is stored in the heat insulating layer 22b as in the case where the heat insulating layer 22b is thickened, and the heat storage function is enhanced.

  Here, the manufacturing method of the thermal head in the present embodiment will be described with reference to FIG.

In the method of manufacturing the thermal head in the present embodiment, first, an insulating plate 22a such as alumina (Al ₂ O ₃ ) is formed (S1).

  Next, on the upper surface of the insulating plate 22a formed in S1, the heat conductor 25 made of aluminum (Al) is placed in the main scanning direction so that the width in the sub-scanning direction ds is 1 mm at a position immediately below the heat generating region 24. Printing is performed in a strip shape extending to dm with a film thickness of 15 μm (S2).

Next, a glass paste made of silicon oxide (SiO ₂ ) is printed on the upper surfaces of the insulating plate 22a and the heat conductor 25 with a film thickness of 25 μm (S3).

  Next, the insulating plate 22a on which the glass paste is printed is baked to a temperature higher than the softening point of the glass. (S4). At this time, the heat conductor 25 composed of aluminum having a melting point lower than the softening point of the glass is melted, and the volume thereof is increased by thermal expansion in the heated glass paste with increased fluidity.

  Here, the softening point of glass is higher than the melting point of aluminum. For this reason, when the temperature is lowered after cooling after firing, the glass paste is first solidified to form a cavity A having a predetermined volume.

  Thereafter, when the temperature further decreases, the heat conductor 25 made of aluminum contracts, and when the temperature falls below the melting point of aluminum, it becomes solid and the volume is greatly reduced. The volume of the heat conductor 25 solidified at this time is smaller than the volume of the cavity A in the glass paste.

  In addition, the space between the heat conductor 25 and the heat insulating layer 22b is filled with air flowing in through the insulating plate 22a when the heat conductor 26 contracts after the glass paste is solidified.

  As a result, the printed glass paste is melted and fixed to the insulating plate 22a as the heat insulating layer 22b to form the support substrate 22, and the gap A is formed inside the heat insulating layer 22b. In addition, in the cavity A, a heat conductor 25 is formed which is in contact with the insulating plate 22a and is not in contact with the inner wall of the heat insulating layer 22b, thereby providing a gap between the heat generating portion 23b and the insulating plate 22a. .

  Thereafter, the heating resistor layer 23 and the electrode 28 are formed on the surface of the heat insulating layer 22b (S5). More specifically, first, a resistance material such as cermet is fixed to the surface of the heat insulating layer 22b by sputtering or the like. Thereafter, the heating resistor layer 23 is patterned by etching so as to form the heating resistors 23a arranged at intervals in the main scanning direction dm.

  Further, a conductive material such as aluminum is fixed to the plate on which the heating resistor 23a is formed by sputtering or the like. Thereafter, the electrode 28 is patterned by etching so as to extend along the heating resistor 23a with a gap corresponding to the heating portion 23b interposed therebetween.

  After step S5, a protective layer 29 covering the heat insulating layer 22b, the heating resistor layer 23, and the electrode 28 is formed (S6).

  The heating plate 20 thus formed is placed on the heat sink 30 together with the circuit board 40 (S7). Further, the thermal head 10 is manufactured by connecting the heating element plate 20 and the circuit board 40 with the bonding wire 44 (S8), and further sealing the connection portion with the bonding wire 44 with the resin 48 (S9). .

  As described above, in the heat generating plate 20 of the present embodiment, when the heat generating portion 23b generates heat and becomes a high temperature state, the heat conductor 25 made of a material having a higher thermal expansion coefficient than the heat retaining layer 22b It expand | swells so that the clearance gap between the body 25 and the inner wall of the heat retention layer 22b may be filled. Thereby, the heat conductor 25 having a higher heat conduction coefficient than the heat insulating layer 22b comes into contact with both the heat insulating layer 22b and the insulating plate 22a.

  For this reason, the heat generating plate 20 can conduct the heat from the heat generating portion 23b to the heat radiating plate 30 through the heat retaining layer 22b, the heat conductor 25 and the insulating plate 22a, and can quickly dissipate heat.

  As a result, the heat generating plate 20 can improve the thermal response and obtain a good heat dissipation function as in the case where the heat insulating layer 22b is thinned, and can improve the printing quality.

  Further, the heat generating plate 20 has a high thermal conductivity when the heat generating portion 23b is at a high temperature and quickly dissipates heat. However, in this state, since the entire thermal head 10 is already warmed, the concentration efficiency does not deteriorate. .

  Further, when the temperature of the heat generating portion 23b decreases and approaches a normal temperature state, the heat conductor 25 contracts away from the inner wall of the heat insulating layer 22b, and is not in contact with the heat insulating layer 22b. For this reason, the heat generating body plate 20 can make it difficult to conduct the heat of the heat generating portion 23b to the insulating plate 22a. As a result, the heat generating plate 20 has an improved heat storage function as when the heat retaining layer 22b is thickened, and can suppress power consumption.

  As described above, the heating element plate 20 of the present embodiment utilizes the difference in thermal expansion coefficient and thermal conductivity coefficient between the heat insulating layer 22b formed of silicon oxide and the thermal conductor 25 formed of aluminum. When the heat generating part 23b is at a high temperature, the heat dissipation function can be enhanced, and when the heat generating part 23b is at a normal temperature, the heat storage function can be enhanced. Thereby, the thermal head 10 can suppress power consumption while improving printing quality.

  By the way, if the heat insulating layer 22b is made thinner, the thermal responsiveness is improved. In this case, since the height of the protrusion 21 is lower than that of the thick heat insulating layer 22b, the height of the heat generating region 24 is also reduced.

  For this reason, the thermal recording medium 60 and the platen roller 50 are in contact with areas other than the heat generation area 24, and the head pressure applied to the thermal head 10 by the head pressing portion is dispersed to areas other than the heat generation area 24. It may not be converted to a sufficient nip pressure.

  In order to cope with such a state, it is necessary to increase the nip pressure by increasing the head pressure, but in that case, the torque of the drive motor in the head pressing portion must be increased, which increases power consumption. End up.

  In addition, it is necessary to stabilize the power supply of the thermal printer itself to stabilize the conveyance of the thermal recording medium 60, which increases the cost of the thermal printer.

  On the other hand, since the heat generating plate 20 of the present embodiment can improve the thermal responsiveness without thinning the heat insulating layer 22b, it is possible to suppress the increase in power consumption and the cost of the thermal printer.

  Here, in the thermal printer, since the operating temperature range of the heat generating portion 23b differs depending on the printing speed and the type of the printing medium, the ratio between the optimal cross-sectional area of the cavity A and the cross-sectional area of the heat conductor 25 is respectively used. Exists.

  For this reason, the thermal expansion coefficient, the softening point and the material of the heat conductor 25 and the heat insulating layer 22b, the cavity A and the thermal conductor 25 so as to balance the heat storage function and the heat radiation function according to the operating temperature range of the heat generating part 23b. It is desirable to set the size of the heat conductor 25.

  When the thermal head prints on the thermal recording medium 60 at the highest density, the largest current flows through the heat generating portion 23b and the heat generating portion 23b generates heat at the highest temperature.

  In the present embodiment, the material and the cavity of the heat insulating layer 22b are set so that the cross-sectional area of the cavity A and the cross-sectional area of the heat conductor 25 become equal when the temperature is higher than the printing temperature of 70% of the maximum density. The size of A and the material and size of the heat conductor 25 are set.

  In the heating element plate 20 described above, the heat conductor 25 is attached to the insulating plate 22a without coming into contact with the heat retaining layer 22b at room temperature. However, the present invention is not limited thereto, and the heat conductor 25 is attached to the insulating plate 22a. You may adhere to the heat insulation layer 22b, without contacting.

  In short, the heat conductor 25 forms a gap between the heat generating part 23b and the insulating plate 22a in the normal temperature state, thereby making it difficult for the heat in the heat generating part 23b to be conducted to the insulating layer 22a and in the high temperature state. It is sufficient to make it easy to conduct heat in the heat generating portion 23b to the insulating plate 22a by contacting both the insulating plate 22a and the heat insulating layer 22b.

  In the heating plate 20 described above, when the heat conductor 25 is formed on the surface of the insulating plate 22a, aluminum is printed in a strip shape. However, the present invention is not limited to this. For example, an aluminum wire is insulated so as to extend in the main scanning direction dm. It may be adhered to the surface of the plate 22a.

  In the heating plate 20 described above, aluminum is used as the heat conductor 25. However, the present invention is not limited to this, and other materials may be used as long as they have a higher thermal conductivity coefficient and thermal expansion coefficient than the heat retaining layer 22b. good.

  Further, the heating plate 20 described above is filled with air between the heat conductor 25 and the inner wall of the heat insulating layer 22b in a normal temperature state, but is not limited thereto, and is filled with various substances such as gas. What is necessary is just to make it fill with the substance whose heat conductivity coefficient is lower than the heat retention layer 22b. A vacuum may also be used.

DESCRIPTION OF SYMBOLS 10 ... Thermal head, 20, 120 ... Heat generating body plate, 21 ... Projection, 22, 122 ... Support substrate, 22a, 122a ... Insulating plate, 22b, 122b ... Thermal insulation layer, 23 ... Heat generating resistor layer , 23a... Heat generating resistor, 23b... Heat generating portion, 24... Heat generating area, 25... Heat conductor, 28a and 28b. 42 ... Driver IC, 44 ... Bonding wire, 48 ... Resin, 50 ... Platen roller, 52 ... Shaft, 60 ... Thermal recording medium, A ... Cavity, dm ... Main scanning direction, ds ... Sub scanning direction

Claims (5)

In a thermal head comprising an insulating plate, a heat insulating layer provided on the surface of the insulating plate, and a heat generating portion that is formed on the surface of the heat insulating layer and generates heat when current flows.
A cavity is formed between the heat generating part and the insulating plate,
A thermal head comprising: a heat conductor disposed inside the cavity so as to form a gap between the heat generating portion and the insulating plate in a normal temperature state.   2. The thermal head according to claim 1, wherein the thermal conductor is in contact with both the insulating plate and the heat generating part by being expanded by heat in a high temperature state.   The thermal head according to claim 1, wherein the thermal conductor has a higher coefficient of thermal expansion than the thermal insulation layer.   The thermal head according to claim 1, wherein the thermal conductor has a thermal conductivity coefficient higher than that of the heat retaining layer. A first step of attaching a heat conductor extending in a strip shape in the main scanning direction orthogonal to the direction in which the printing medium is conveyed to the surface of the insulating plate;
After the first step, a second step of attaching a heat insulating layer made of a material having a softening point higher than the melting point of the heat conductor to the surface of the insulating plate and the heat conductor;
After the second step, a third step of heating the insulating plate and the heat conductor so as to exceed the softening point of the heat retaining layer;
After the third step, a fourth step of cooling the insulating plate and the heat conductor so as to be below the melting point of the insulating plate;
The manufacturing method of the thermal head characterized by comprising.

Images