JP2521360B2 - Thermal recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a thermal recording apparatus used in a facsimile, a printer or the like.

<Prior Art> A conventional thermal recording apparatus will be described with reference to FIG.

2. Description of the Related Art Conventionally, various recording devices such as a printer for a facsimile or a word processor have a recording device using a printing method such as a wire dot method, a laser printer method, a thermal recording method, or a thermal transfer method, which are mainly used as office equipment. However, as demand for household appliances has increased in recent years, downsizing, price reduction, and noise reduction have been required. Under such circumstances, in the conventional thermal print recorder, as shown in FIG. 7, Al ₂ O having a purity of 90% or more is used.
A glaze layer for heat storage on a ceramic substrate 101 composed of ₃
Using a glazed ceramic substrate on which 102 is formed, a plurality of heating resistors 103 are arranged in a line in the scanning direction, and one end of each heating resistor 103 and the control element 104 are electrically connected. In the case where the individual electrode 105 and the common electrode 106 having the other end electrically connected in common are formed, and further the heating resistor 103, the individual electrode 105 and the common electrode 106 (hereinafter, the individual electrode 105 and the common electrode 106 are collectively referred to as , Wiring electrode 107
Called. ) Is provided with a protective film 108 for preventing the deterioration due to wear and the like.

Further, the control element 104 is connected to the ceramic substrate 101 by a face-down bonding method between the individual electrode 105 and the electrode of the control element 104 via solder bumps, and the control element 104 is provided with a resin mold 109.

Furthermore, the double-sided flexible circuit board 110 to which a thermistor, a connector, a condenser, etc. are soldered is used as a backing board 111.
The head cover 112 and the heat sink 113 sandwich a part of the double-sided flexible circuit board 110 and the backing board 111 between the head cover 112 and the heat sink 113.
Are fixed with screws. In addition, 114 is an external connection connector, and 115 is a pressing rubber for pressing down the electrical contacts of the double-sided flexible circuit board 110.

<Problems to be Solved by the Invention> In the structure of the conventional thermal recording apparatus as shown in FIG. 7, in order to supply electric power to the heating resistor 103 and color the thermal paper, a certain amount of applied power is applied. Is required. For example, the ceramic substrate 101 has a thickness of 0.8 mm, the glaze layer 102 has a thickness of 75 μm, and the heating resistor 103 has a thickness of 0.2 mm.
μm, the thickness of the wiring electrode 107 is 0.8 μm, the thickness of the protective film 108 is 3 μm, the width of the heating resistor 103 is 110 μm, and the length is 170 μm.
m, resistance value set to 1700Ω, thermal recording device applied voltage
0.34 per element when driven at 24 V and pulse application period of 5 ms
Applied energy of mJ or more is required.

In order to reduce the energy applied to such a thermal recording apparatus, the glaze layer 102, which is a heat storage layer, must be formed thicker. However, the glaze layer 102
When the thickness is increased, the applied energy can be suppressed to be low, but the amount of heat stored in the glaze layer 102 becomes large, so that the thermal paper is colored even if the applied pulse is stopped, a so-called tailing phenomenon occurs. . Also, the glaze layer 10
In order to increase the thickness of 2, reduce the applied energy, and eliminate the tailing phenomenon, the period of the applied pulse is made sufficiently long and the heat accumulated in the glaze layer 102 is radiated to the ceramic substrate 101 with a time margin. Can be improved,
There is a problem that the demand for higher speed cannot be satisfied.

On the other hand, from the viewpoint of manufacturing the ceramic substrate 101, a step of removing the alkaline component from the raw material powder, a step of correcting the sled generated during high temperature firing by polishing,
Heating resistor 103 and wiring electrode 1 that require high dimensional accuracy
An edge polishing process is required to obtain the flatness of the end face of the substrate that is required when 07 is formed on the glaze by photolithography, etc. In addition, during the ceramic firing, the warp of the substrate and the pinhole of the glaze layer 102 However, there is a problem in that the yield is reduced due to problems such as waviness and protrusions, and the manufacturing cost is increased.

When the area of the ceramic substrate is further increased, the yield decrease due to the warpage of the ceramic substrate 101 and the pinholes of the glaze layer 102 becomes more significant, and moreover the equipment cost is increased because the diameter of the firing furnace is increased. There was also the problem that the price would rise.

In view of the above problems, the present invention uses a copper-clad printed wiring board made of a heat-resistant resin as an insulating substrate, and uses a low thermal conductivity material, for example, a heat-resistant resin as an insulating substrate or a heat storage layer material, In addition, by disposing a heat dissipation layer in a required place by using copper on the insulating substrate, it is intended to improve thermal characteristics and solve all of low power consumption, high speed, and low price. .

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention arranges a plurality of heating resistors on an insulating substrate side by side in the scanning direction, and one end of each heating resistor is connected to a control element and an electric element. In a thermal recording device having a common electrode that is electrically connected and a common electrode that is electrically connected in common with the other end of the heating resistor, the insulating substrate is a copper-clad printed wiring board made of heat-resistant resin. A heat dissipation layer formed by using a copper foil on the insulating substrate and a heat storage layer made of a polyimide resin covering the heat dissipation layer are laminated under the heat generating resistor. .

<Operation> In the above structure, the heat storage layer according to the present invention is a polyimide having a thermal diffusivity (heat diffusivity is sufficiently low) of about 1/4 that of the conventional glass glaze heat storage layer, as is apparent from the table below. Since it uses a resin, it has better heat insulation performance than the conventional thermal recording device, and when power is applied, it reduces the amount of heat transferred to the heat dissipation layer of the copper foil underneath the polyimide and moves to the thermal paper side. Since it has the effect of increasing the amount of heat to be applied, the applied voltage can be used efficiently and energy saving can be facilitated.

Under the polyimide heat storage layer, copper having a thermal diffusivity about 9 times (the thermal diffusivity is sufficiently high) which is about 9 times as high as that of the alumina ceramic which is the material of the conventional heat radiation layer and insulating substrate is arranged as a heat radiation layer by pattern etching. Since the heat dissipation after printing is good, for example, the tailing phenomenon during printing that occurred when a conventional glass glaze layer was formed thickly is because the speed of heat moving to the heat dissipation layer becomes faster, It disappears in manufacturing.

Further, the present invention aims to improve the thermal efficiency by setting the difference in height of the thermal diffusivity of the polyimide heat storage layer and the copper heat dissipation layer to a sufficiently large value, and in addition to the conventional insulating substrate placed below them. The insulating substrate is made of a heat-resistant resin having a thermal diffusivity sufficiently lower than that of the alumina ceramic substrate (or having a thermal diffusivity somewhat lower than that of the alumina ceramic substrate) and has a proper thickness. (The amount of heat that does not directly contribute to printing) can be held, and energy can be saved.

In addition, since the insulating substrate according to the present invention uses a copper-clad printed wiring board (for example, a heat-resistant glass epoxy substrate) formed of a heat-resistant resin, unlike conventional ceramic substrates, removal of alkali components, high-temperature baking, and substrate Since it is easy to increase the size of the substrate without requiring a step such as polishing, productivity can be improved and cost can be reduced.

<Example> An example of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view of a main part of a thermal recording apparatus according to the present invention, FIG. 2 is a sectional view of a thermal recording apparatus according to an embodiment of the present invention, and FIG. FIG. 3 (b) is a thermal response characteristic diagram when a printed wiring board is used, FIG. 3 (b) is a thermal response characteristic diagram when a printed wiring board having a heat dissipation layer and a back metal layer is used, and FIG. FIG. 4 is a diagram showing a thermal response characteristic when a printed wiring board having only layers is used, FIG. 4 is a diagram showing a relationship between print power and print density in one embodiment of the present invention and a conventional example, and FIG. Diagram showing the heat distribution characteristics of the body,
FIGS. 6A to 6I are manufacturing process diagrams of a thermal recording apparatus according to an embodiment of the present invention.

The following table is a table showing the thermal diffusivity of each constituent material of the thermal recording apparatus.

First, FIG. 2 will be described. Incidentally, it is shown in FIG. The same functional parts as those in the conventional example are designated by the same symbols.

As shown in FIG. 2, in a thermal recording apparatus according to an embodiment of the present invention, a plurality of heating resistors 2 are arranged side by side in the scanning direction on an insulating substrate 1, and one end of each heating resistor 2 is connected to a control element 3. And a common electrode 5 that is electrically connected in common with the other end of each of the heating resistors 2, and the insulating substrate 1 is copper-clad made of heat-resistant resin. A heat dissipation layer 6 formed of a printed wiring board and formed below the heat generating resistor 2 by using a copper foil on the insulating substrate 1, and a heat storage layer 7 made of a polyimide resin covering the heat dissipation layer 6. Are stacked.

As shown in the thermal diffusivity table above, the heat storage layer 7 according to this example uses a polyimide resin having a thermal diffusivity about 1/4 of that of the conventional glass glaze heat storage layer. Copper, which has a thermal diffusivity about 9 times that of alumina ceramics, which is the material of the layer / insulating substrate, and which is about three orders of magnitude higher than the thermal diffusivity of the polyimide resin is used. Further, the insulating substrate 1 also uses a heat-resistant copper-clad printed wiring board having a low thermal diffusivity (in this example, a glass epoxy resin substrate having a thermal diffusivity about twice that of polyimide and about half the glass glaze is used). The above-mentioned heat dissipation layer 6 is formed on the front surface side of the substrate, and the lower heat dissipation metal layer 10 is formed of copper on the back surface side.

Further details will be described with reference to FIG. The insulating substrate 1 is a heat-resistant printed wiring board having a thermal decomposition starting temperature of 350 ° C., a thickness of 0.8 mm, a length of 232 mm and a width of 80 mm, and is composed of a glass epoxy substrate formed by impregnating glass fiber with epoxy resin. . Although this insulating substrate 1 can be produced at a lower cost than the conventional thermal recording device made of a ceramic substrate, it cannot be heated at a temperature higher than the thermal decomposition temperature (350 in this embodiment).
℃), there is a problem that warp and swell easily occur.
Therefore, in the production process, the production process is performed under the condition that the temperature of the insulating substrate 1 does not exceed the thermal decomposition temperature, and a layer for preventing thermal deformation of the insulating substrate 1 during the production of the thermal recording apparatus, warp of the substrate, As a layer for preventing swelling, production is performed with the metal layers (heat dissipation layer 6, back surface metal layer 10) on both sides of the insulating substrate 1 stuck.

The heat dissipation layer 6 and the back surface metal layer 10 are obtained by laminating a copper foil on the insulating substrate 1 (so-called copper-clad printed wiring board) and then stacking an Au layer via a NiP layer (or Ni layer) by electroless plating. It has a three-layer structure. The reason for having a three-layer structure is as follows. That is, it is easy to oxidize with only copper,
Solder bumps cannot be connected at the time of forming bumps in the face-down bonding portion described later. When Au is directly laminated on the copper layer, diffusion occurs between both layers in the heat treatment process during the production process, and as a result, copper oxidizes on the surface of the Au layer, resulting in a diffusion prevention barrier (NiP) between the copper layer and the Au layer. Oxidation is prevented by using a three-layer structure with layers.

In this way, the insulating substrate 1 having the metal layers on both sides is
The heat-dissipating layer 6 and the face-down bonding portion 11 are patterned by etching the front-side metal layer, and the back-side metal layer is not etched and the back-side metal layer is left as it is.
Used as 10.

The heat storage layer 7 is formed of a polyimide resin, and the solder dam 12 forming the face-down bonding portion 11 is also formed at the same time. This heat storage layer 7 has a thermal diffusivity of 0.11 (mm ² / se
The polyimide resin containing the siloxane bond of c) is used. This is about 1/4 of the thermal diffusivity of 0.45 (mm ² / sec) of the glass glaze used in the past, so the heat lost to the insulating substrate side is reduced compared to the conventional one, making it a thermal paper. The ratio of heat energy transmitted is high, and energy saving can be achieved. Further, the polyimide resin containing a siloxane bond is also excellent in adhesion to a metal.

A plurality of heating resistors 2 arranged in the scanning direction are laminated on the polyimide heat storage layer 7 with an inorganic layer 8 interposed therebetween. Of these, the inorganic layer 8 is formed of a SiO ₂ film formed to be thinner than the heat storage layer 7. This SiO ₂ is an insulating material and has a thermal diffusivity that is about eight times larger than that of polyimide, and has the effect of quickly diffusing heat in a two-dimensional direction in order to make the heat distribution of the heating resistor part uniform.

The heating resistor 2 is formed of, for example, a TaSiO ₂ film, and has an individual wiring electrode 4 electrically connected to the control element 3 at one end,
A common wiring electrode 5 for electrical connection is arranged in common with the other end of each heating resistor 2, and electric power is selectively supplied by the control of the control element 3 to generate heat.

When the common wiring electrode 5 and the heat dissipation layer are electrically connected, thermal efficiency is improved, and at the same time, a sufficient current capacity can be obtained for the current flowing through the common electrode, so that the thermal recording apparatus can be downsized. .

The protective film 9 is formed on the heat-generating resistor 2, the common wiring electrode 5, the individual electrode 4, and the polyimide heat storage layer 7, excluding the solder dam portion 12 that constitutes face-down bonding. Functions as a preventive film.

The control element 3 is attached to the face-down bonding portion 11 and molded with the epoxy resin 13.

A heat sink 113 is adhered to the back surface of the insulating substrate 1 via a back surface metal layer 10. The heat sink 113 is made of a metal having a high thermal diffusion coefficient (aluminum plate in this embodiment), and performs thermal diffusion of the thermal recording apparatus.

The thermal characteristics of the heat dissipation layer 6, the heat storage layer 7, and the insulating substrate 1 will be described more specifically below.

The Joule heat generated in the heating resistor 2 is generated by the individual wiring electrode.
4. Except for the amount of heat radiated through the common wiring electrode 5, the heat is dispersed in the vertical direction of the cross section of the thermal recording apparatus. Now, the energy transferred to the thermal paper via the protective film 9 is Q ₁ , the energy transferred to the insulating substrate 1 via the heat storage layer 7 through the heat dissipation layer 6 is Q ₂ , and the insulating substrate 1 via the heat storage layer 7. If the energy transferred to is tentatively defined as Q ₃ , the following conditions hold when the applied voltage is ON and OFF, respectively.

When applied voltage is ON Q ₁ ＞ Q ₂ ＞ Q _{3 When} applied voltage is OFF Q ₂ ＞ Q ₁ , Q ₂ ＞ Q _{3 When} the applied voltage is ON, the thermal diffusivity is 9.96 (when sialon is used as the protective film 9). mm ² / sec), the thickness of the polyimide heat storage layer 7 is 0.11 (mm ² / sec), and the film thickness is 6 to 10 μm for the polyimide heat storage layer 7 compared to 3 μm for sialon. Therefore, the isothermal line drawn with the center line of the heating resistor 2 as the origin becomes dense on the protective film side, and the condition of Q ₁ > Q ₂ + Q ₃ always holds. On the other hand, similarly, the thickness of copper 6 is 9 μm, thermal diffusivity is 112.8 (mm ² / sec), and the thickness of heat-resistant glass epoxy substrate (insulating substrate 1) is 0.8 mm, thermal diffusivity.
Due to the relationship of 0.25 (mm ² / sec), the relationship of Q ₂ > Q ₃ holds.

When the applied voltage is OFF, the amount of heat stored in the polyimide heat storage layer 7 having a low thermal diffusivity is radiated, so that TaSiO ₂ (heating resistor 2) and copper (heat dissipation layer 6) sandwiching the heat storage layer 7 the ratio of the thermal diffusivity, 0.58 TaSiO ^₂ (mm ₂ / se
c) is 112.8 (mm ² / sec) for copper, and its ratio is 194.5
Energy Q ₂ through the double large copper heat dissipation layer, energy
It becomes larger than Q ₁ and Q ₃ , and as a result, the energy transferred to the thermal paper is switched when the applied voltage is ON and OFF. Q ₁ > Q ₂ (when the applied voltage is ON) Q ₁ <Q ₂ (when the applied voltage is OFF ), It becomes possible to switch the energy quickly.

This is because the thermal diffusivity of a conventional thermal recording device using a glazed ceramic substrate is 9.96 for a sialon (protective film).
(Mm ² / sec), with alumina ceramic substrate 12.1 (mm ² / se
c), the glass glaze is 0.45 (mm ² / sec), which are closer to each other compared to the structure of the present invention, and Q ₁ > Q ₂ (when the applied voltage is ON) and Q ₁ <Q ₂ (the applied voltage is OFF). However, the printing efficiency is poor because the difference between Q ₁ and Q ₂ in the ON and OFF states is not large, but the structure of the present invention has a polyimide resin with a sufficiently low thermal diffusivity and thermal diffusion. Since copper having a sufficiently high rate is used, the difference between Q ₁ and Q ₂ becomes large, and therefore the thermal efficiency can be significantly improved.

By electrically connecting the heat dissipation layer 6 to the common wiring electrode 5, the electric and thermal capacities of the heat dissipation layer 6 can be increased. Therefore, the difference between Q ₁ and Q ₂ described above is further increased. The thermal characteristics can be improved. At the same time, a sufficient current capacity can be obtained with respect to the current, which is also effective for downsizing the thermal recording apparatus.

The insulating substrate 1 is made of a heat-resistant glass epoxy material having a thermal diffusivity about twice that of the polyimide heat storage layer 7 and about 1/50 times that of the conventional alumina ceramic substrate. As a result, heat is stored in the polyimide heat storage layer 7. Most of the heat is radiated to the insulating substrate 1 through the copper heat dissipation layer 6. At this time, since the insulating substrate 1 has a low thermal diffusivity to some extent, the insulating substrate itself can have a function of accumulating heat to some extent, and energy saving drive can be supported.

The back metal layer 21 functions as follows. Driving pulse OFF
At times, the heat from the heating resistor 2 is quickly diffused through the insulating substrate 1 to the back surface metal layer 21, and then the back surface metal layer 21.
The heat dissipation is further improved by transmitting heat to the heat sink 14 adhered to the lower surface of 10.

Next, FIG. 3 shows the time change of the substrate surface temperature during continuous pulse driving. In the structure in which the heat dissipation layer 6 and the back surface metal layer 10 are not provided, as shown in FIG. 3 (a), the Joule heat generated in the heating resistor portion continues to be accumulated in the substrate as the number of applied pulses increases, and thereafter, If the amount of heat that exceeds the coloring temperature of the thermal paper continues to be accumulated, a tailing phenomenon will occur. On the other hand, as shown in FIG. 3 (b), in the structure in which the heat dissipation layer 6 and the back surface metal layer 10 are provided, a heat dissipation effect is added in a proper place to prevent heat from being accumulated in the head. The thermal characteristics can be improved. Even when only the heat dissipation layer 6 is not provided with the back surface metal layer 10, as shown in FIG. 3C, a time difference in temperature rise and a temperature rise of the heating resistor (when the applied voltage is OFF) are recognized. However, the suppression of the temperature rise is more remarkably recognized than the one without the heat dissipation structure (3rd
As a result, the thermal characteristics can be improved to some extent.

Next, the energy consumption of the thermal recording apparatus according to the embodiment of the present invention and the conventional example will be described with reference to FIG.

In FIG. 4, (a) and (b) show the characteristics between the applied power and the print density in one embodiment of the present invention and the conventional example, respectively. As is apparent from the figure, the print power required for the same print density is much smaller in the embodiment of the present invention shown in (a) than in the embodiment shown in (b). This is because the heat storage layer 7 is made of a polyimide resin having a sufficiently low thermal diffusivity, and heat is cut off by the heat storage layer 7 during the application of electric power, so that the loss of the amount of heat generated is smaller than in the conventional case. Therefore, the same level of printing can be guaranteed with less energy. Further, since the insulating substrate 1 is made of a heat-resistant glass epoxy material having a low thermal diffusivity to some extent, this insulating substrate also retains a certain amount of heat, and as a result, the thermal recording device can be driven with less energy compared with the conventional one. .

In the conventional structure shown in FIG. 7, the heating resistor 103
As shown in FIG. 5, the surface temperature distribution of No. 3 has a temperature difference of 30 ° C. or more between the heat generating central portion m and the peripheral portions m ₁ and m ₂ . this is,
This is because the heat diffusion from the heating resistor 103 to the ceramic substrate 101 through the glaze layer 102 in the downward direction and the heat diffusion in the lateral direction through the wiring electrode 107 cannot be ignored. For this reason, when printing on a thermal paper with a conventional thermal recording device, the printed dots have a lower print density in the surrounding area than the central area, which makes it difficult to obtain clear dots.

In this embodiment, an inorganic material layer 8 such as a SiO ₂ film thinner than the heat storage layer 7 is laminated on the polyimide heat storage layer 7, and SiO ₂ is an insulating material and has a thermal diffusivity about 8 times larger than that of polyimide. As in the heating resistor portion, it has the effect of quickly diffusing only the Joule heat component in the two-dimensional direction without changing the current density distribution due to heat generation. As shown in FIG. The surface temperature distribution can be controlled so that there is no temperature difference from the central portion m of heat generation to the peripheral portions m ₁ and m ₂ .

Next, a method of manufacturing the thermal recording apparatus according to the present invention will be described with reference to FIG.

Metal foils are attached to both front and back surfaces of a heat-resistant printed circuit board 1 formed by impregnating glass fibers with a heat-resistant epoxy resin and having a thermal decomposition starting temperature of 350 ° C. by a hot pressing method.
This metal foil consists of a copper foil 6A on an aluminum foil 14 with a thickness of 40 μm.
5 to 12 μm, preferably 9 μm, and the aluminum foil 14 is laminated on the insulating substrate 1 so as to be exposed on the outer surface. The aluminum foil 14 is used as a carrier material for laminating the thin-film copper foil 6A, and is used for the reason of the manufacturing method of the metal foil.After laminating the metal foil, the aluminum foil portion 14 is used. Remove by etching.

The surface of the copper layer 6A on the insulating substrate 1 (copper-clad printed wiring board) thus completed is subjected to a surface treatment with a non-woven cloth abrasive to remove the residual aluminum and the oxide film on the copper foil 6A.

Then, the insulating substrate 1 is placed in an oven at 300 ° C. in order to stabilize its dimensions, and then the surface of the copper layer 6A is subjected to a surface treatment again in order to remove the oxide film on the copper foil 6A.

The insulating substrate 1 shown in FIG. 6 (b) is obtained as described above.

Next, as shown in FIG. 4 (c), in order to form the copper layer 6A on the surface of the insulating substrate 1 in a predetermined pattern, resist formation by electro deposition, copper etching, and resist stripping are sequentially performed. . The heat dissipation layer copper layer 6A and the face-down bonding portion copper layer 11A are simultaneously formed by this patterning process. The copper layer 10A on the back surface of the insulating substrate 1 improves the thermal characteristics of the substrate and also improves the warpage of the substrate due to heat. From the intention of doing so, patterning is not performed and the entire area is left.

Next, on the heat dissipation layer copper layer 6A patterned, the face-down bonding portion copper layer 11A and the back surface metal portion copper layer 10A,
NiP layers (6B, 11B, 10B) and Au layers (6C, 11C, 10C) are sequentially laminated by electroless plating. This is to prevent the copper surface from being oxidized in the manufacturing process. When Au is directly laminated on copper, diffusion by both metals occurs and copper oxidizes on the Au surface. Therefore, to prevent this diffusion, a NiP layer of 1 to 2 μm is provided as a diffusion prevention barrier between the copper layer and the Au layer.
Anti-oxidation measures are taken by forming a 3-layer structure.

Thereafter, as shown in FIG. 6 (d), a polyimide precursor 15 is applied to the entire surface of the insulating substrate 1 by a roll coating method or a spin coating method as shown in FIG. 6 (d). As shown in the figure, the metal layer (11A, 11A
B, 11C) and the common electrode part metal layer (6A, 6B, 6C: generically referred to as the heat dissipation layer 6 hereinafter), a polyimide resin is formed in a fixed pattern while leaving a part of the upper surface, and heat treatment is performed to remove the polyimide precursor. The polyimide heat storage layer 7 and the solder dam 12 of the face-down bonding portion are formed by imidization and curing. There are a positive resist method and a negative resist method as a method for forming the pattern of the polyimide precursor 15, but the former has a characteristic that the pattern accuracy is deteriorated while the resist development and the polyimide etching can be performed at the same time. .

First, a method for forming the polyimide heat storage layer 5 by the positive resist method will be described. Polyimide precursor for positive resist method
After application of 15, heat curing is performed in a semi-cured state in an oven at 100 to 150 ° C., and then resist formation, exposure, development, and resist stripping steps are sequentially performed. Incidentally, the developing solution used in this developing step is a tetramethyl hydroxide 5% solution, which allows development and etching to be carried out at the same time, and the number of steps can be reduced. After photo-etching, the polyimide precursor 15 is imidized and cured by heating. To prevent cracks, heat treatment is performed in an oven at 200 ° C. and 300 ° C., and then the back surface of the insulating substrate 1 is contacted with a heat dissipation plate. Surface polyimide precursor while cooling
15 is heat-treated by infrared irradiation at a temperature of 300 ° C. or higher to form a polyimide heat storage layer. The reason for performing this infrared ray irradiation step is that the insulation substrate 1 cannot be directly heated in the oven because the polyimide resin curing temperature is close to 300 ° C while the thermal decomposition temperature is up to 350 ° C. is there.

Next, a method for forming the polyimide heat storage layer 7 by the negative resist method which is the other manufacturing method will be described.

First, after applying the polyimide precursor 15, 150 in the oven
The temperature is gradually increased to 200 ° C. and the precursor precursor 15 is semi-cured. This semi-cured state has a characteristic that the etching accuracy is improved because the imidization is further advanced than the cured state by the positive resist method described above. afterwards,
The steps of forming resist, exposing, developing, and etching polyimide are sequentially performed.

A mixed solution of hydrazine and ethylenediamine is used as the etching solution at this time. 300 after photo etching
After heat treatment in an oven at ℃, by irradiating the polyimide precursor 15 on the surface with infrared rays while cooling by contacting a heat radiating plate with the back surface of the insulating substrate 1 as in the positive resist method described above,
Heat treatment is applied at a temperature of 300 ° C or higher, and polyimide heat storage layer 7
To form. Here, as the material of the polyimide heat storage layer 7, a non-photosensitive polyimide resin containing a siloxane bond is used for the adhesion between the metal and the resin.

Next, as shown in FIG. 6 (f), the polyimide heat storage layer 7
The inorganic layer 8 is formed on top. Here by sputtering
After forming the SiO ₂ layer, photoetching is performed to finish into a fixed pattern.

Further, after forming the heating resistor layer by the sputtering method, pattern etching is performed so that the plurality of heating resistors 2 are arranged in a line in the scanning direction.

Then, as shown in FIG. 4 (g), after the wiring electrode layer 16 is formed by the sputtering method, the individual electrodes 4 for electrically connecting each heating resistor 2 and the control element 3 and other heating resistors are formed. Body 2
The common wiring electrode 5 for electrically connecting with is formed by etching. Here, TaSiO is used as the resistance material.
₂ and Al-Si is used as the wiring electrode material.

Finally, as shown in Fig. 4 (i), SiO is formed by plasma CVD method.
The protective film 9 is formed by stacking N. (Alternatively, the protective film 9 may be formed by stacking sialon by a sputtering method.) In the above manufacturing method, a plurality of substrates are simultaneously formed on one substrate in consideration of productivity, and then individually formed. I am trying to divide it into. Then, after dividing the substrate into a predetermined size by the dicing method, the divided substrate is reflowed by the infrared furnace by the face down bonding method and connected to the face down bonding section 11 as shown in FIG. To do. Further, the control element 3 is molded with the epoxy resin 13, and the thermistor, the connector, the capacitor and the like are soldered, and then the double-sided flexible circuit board 11 is formed.
By sandwiching 0 between the head cover 112 and the heat sink 113 and fixing it with screws, the head portion of the thermal recording apparatus and the flexible circuit board 110 for inputting / outputting signals are connected.

The thermal recording apparatus having the structure of one embodiment of the present invention is completed through the above steps.

Although a non-photosensitive polyimide resin containing a siloxane bond is used as the material of the heat storage layer 7 used in the present embodiment, the material is not limited to this and, for example, another non-photosensitive polyimide resin. Alternatively, a photosensitive polyimide resin may be used.

<Effects of the Invention> As described above, according to the present invention, a printed wiring board made of a heat-resistant resin is used as an insulating substrate, and a polyimide heat storage layer having a low thermal diffusivity is provided under the heating resistor. The heat is insulated and the amount of heat transmitted to the thermal paper can be increased, so that energy saving can be realized. In addition, since there is a heat dissipation layer below the polyimide heat storage layer that includes a copper layer having a thermal diffusivity higher than that of the polyimide heat storage layer by about three orders of magnitude, the heat cut off by the polyimide heat storage layer is promptly output after printing. In the present invention, the tailing phenomenon which has been diffused by the heat dissipation layer and which has occurred conventionally does not occur.

Also, since a printed wiring board made of heat-resistant resin is used as the insulating substrate, unlike conventional ceramics, this substrate itself retains heat, and steps such as removal of alkaline components and polishing of high-temperature baked substrates are not required. In addition, cost reduction can be achieved, and because it is a resin substrate, it has good workability. For example, a heating resistor, wiring electrodes, through-hole wiring, control element, and external connection connector are formed on the same substrate. You can also do it.

As described above, the present invention can provide a thermal recording apparatus which has good printing quality, low applied energy, high speed driving, and can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts of a thermal recording apparatus according to the present invention, and FIG.
The present invention is a sectional view of a thermal recording apparatus according to an embodiment of the present invention, FIG. 3 (a) is a thermal response characteristic diagram when a printed wiring board having no heat dissipation structure is used, and FIG. FIG. 3B is a thermal response characteristic diagram when a printed wiring board having a heat dissipation layer and a back electrode layer is used, and FIG. 3C is a thermal response characteristic when a printed wiring board having only a heat dissipation layer is used. FIG. 4 is a diagram showing the relationship between the printing power and the printing density of one embodiment of the present invention and the conventional example, and FIG. 5 is a diagram showing the heat distribution characteristics of the heating resistor.
6 (a) to 6 (i) are manufacturing process diagrams of a thermal recording apparatus according to an embodiment of the present invention, and FIG. 7 is a sectional view of a thermal recording apparatus according to a conventional example. 1 ... Insulating board (printed wiring board) 2 ... Heating resistor 3 ... Control element 4 ... Individual electrode 5 ... Common electrode 6 ... Heat dissipation layer 7 ... Heat storage layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masato Kawanishi 22-22 Nagaike-cho, Naganocho, Abeno-ku, Osaka, Osaka Prefecture Sharp Corporation (72) Mitsuhiko Yoshikawa 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Sharp Corporation (56) References JP-A-62-278060 (JP, A) JP-A-57-185173 (JP, A) JP-A-2-38060 (JP, A)

Claims (1)

(57) [Claims] 1. A plurality of heating resistors are arranged side by side in the scanning direction on an insulating substrate, and an individual electrode electrically connecting one end of each heating resistor to a control element, and each heating resistor. In a thermal recording device having a common electrode whose other end is commonly electrically connected, the insulating substrate is a copper-clad printed wiring board made of heat-resistant resin, and the insulating substrate is provided under the heating resistor. 2. A heat-sensitive recording apparatus comprising: a heat-dissipating layer formed of the copper foil and a heat-accumulating layer formed of a polyimide resin covering the heat-dissipating layer.