JP2519340B2 - Thermal recording device - Google Patents

Description

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

<Prior Art> A thermal recording apparatus according to a conventional example 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 the circumstances, in a conventional thermal printing apparatus, a glazed ceramic substrate having a glaze layer 102 for heat storage formed on a ceramic substrate 101 made of Al ₂ O ₃ having a purity of 90% or more as shown in FIG. It is used, a plurality of heating resistors 103 are arranged in the scanning direction as an example, and one end of each heating resistor 103 and the individual electrode 105 electrically connecting the control element 104, and the other end A common electrode 106 that is electrically connected in common is formed, and the heating resistor 103 and the individual electrode are further formed.
The structure is provided with a protective film 108 for preventing the 105 and the common electrode 106 (hereinafter, the individual electrode 105 and the common electrode 106 are collectively referred to as the wiring electrode 107) from wear deterioration 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> By the way, in the structure of the conventional thermal recording apparatus as shown in FIG. 7, power is supplied to the heating resistor 103,
A certain amount of applied power is required to color the thermal paper. For example, the thickness of the ceramic substrate 101 is 0.8 m
m, the glaze layer 102 has a thickness of 75 μm, the heating resistor 103 has a thickness of 0.2 μm, the wiring electrode 107 has a thickness of 0.8 μm, the protective film 108 has a thickness of 3 μm, and the heating resistor 103 has a width of 110 μm. Sa 17
One element when a thermosensitive recording device with 0 μm and resistance value set to 1700Ω is driven with an applied voltage of 24 V and a pulse application period of 5 ms.
Applied energy of 0.34 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 substrate end face that is required when 07 is formed on the glaze by photolithography, etc., and when the ceramic is fired, the warp of the substrate and the pins of the glaze layer 102 are required. There is a problem in that the yield is reduced due to problems such as holes, undulations, 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, uses a low thermal conductivity material, for example, a heat-resistant heat storage layer material, and By arranging a heat dissipation layer in an appropriate place by using a copper foil, 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 object, the present invention provides a plurality of heating resistors arranged side by side in the scanning direction on an insulating substrate, and one end of each heating resistor is a control element. In a thermal recording device comprising an electrically connected individual electrode and a common electrode electrically connected in common to the other end of each heating resistor, the insulating substrate is a copper-clad printed wiring board made of heat-resistant resin. A heat dissipation layer formed of copper foil of the insulating substrate, a heat storage layer made of a polyimide resin, and a heat generating resistor, so that the heat generating resistor is located on the tip of the convex portion on the insulating substrate. It is characterized in that inorganic material layers such as SiO ₂ having an equivalent area and a thermal diffusivity larger than that of the heating resistor are sequentially laminated, and the heating resistor is formed on the inorganic material layer. .

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

Copper having a thermal diffusivity (sufficiently high thermal diffusivity) about 9 times higher than that of alumina ceramic, which is a material of the thermal radiation layer and the insulating substrate of the thermal recording device using the ceramic substrate as the thermal radiation layer, is formed under the polyimide thermal storage layer. Since it is arranged by pattern etching, the heat dissipation after printing is good. For example, the trailing phenomenon during printing that occurs when a conventional glass glaze layer is formed thickly increases the speed of heat moving to the heat dissipation layer. It will not occur.

In addition to improving the thermal efficiency by setting the difference in the thermal diffusivity of the polyimide heat storage layer and the heat dissipation layer of the copper to be sufficiently large, the insulating substrate disposed thereunder is provided with a conventional alumina ceramic. A heat-resistant resin having a thermal diffusivity sufficiently lower than that of the substrate (or having a thermal diffusivity somewhat lower than that of the substrate) and having an appropriate thickness allows the insulating substrate to have a certain amount of heat (direct The amount of heat that does not contribute to printing can be retained, and energy can be saved.

Furthermore, when printing is performed in a thermal recording device that is composed only of a polyimide heat storage layer and a heat dissipation layer, print fading may occur immediately after printing is started. By forming an inorganic material layer with an insulating material having a diffusivity (for example, SiO ₂ having a thermal diffusivity about 1.53 times larger than that of TaSiO ₂ ), the heat concentrated in the central portion of the heating resistor is generated through this inorganic material layer. Diffuses throughout the resistor. Since the inorganic material layer is an insulator, only heat is diffused without affecting the electrical characteristics of the heating resistor, so that the temperature distribution characteristic of the heating resistor is flattened and print blurring is prevented.

Moreover, since the insulating substrate 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 alkaline components, high-temperature baking, polishing of the substrate, etc. Since no steps are required and the size of the substrate can be increased easily, productivity can be improved and cost can be reduced.

<Example> An example of the present invention will be described below in detail 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. 3 is a temperature distribution characteristic of a heating resistor according to the present invention structure. FIG. 4 (a) is a thermal response characteristic diagram when a printed wiring board having no heat dissipation structure is used, and FIG. 4 (b) is a printed wiring board having a heat dissipation layer and a back surface metal layer. FIG. 4 (c) is a thermal response characteristic diagram when using a printed wiring board having only a heat dissipation layer, and FIG. 5 is a print of an embodiment of the present invention and a conventional example. FIG. 6 is a diagram showing the relationship between power and print density, and 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, FIGS. 1 and 2 will be described. The same functional parts as those of the conventional example shown in FIG. 7 are designated by the same reference numerals.

As shown in FIGS. 1 and 2, a thermal recording apparatus according to an embodiment of the present invention has a plurality of heating resistors 2 arranged side by side in the scanning direction on an insulating substrate 1 and one end of each heating resistor 2 is disposed. Is provided with an individual electrode 4 electrically connected to the control element 3 and a common electrode 5 electrically connected to the other end of each heating resistor 2, and the insulating substrate 1 is made of a heat-resistant resin made of copper. An insulating material having a thermal diffusivity larger than that of the heating resistor 2 and formed on the printed wiring board under the heating resistor 2.
For example, an inorganic layer 8 of SiO ₂ film, a heat storage layer 7 made of a polyimide resin, and a heat dissipation layer 6 made of a copper foil of the insulating substrate are laminated.

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, the copper oxidizes on the surface of the u layer, so a diffusion barrier (NiP ) Oxidation is prevented by using a three-layer structure with layers.

Insulating substrate 1 having metal wire layers on both sides
Is used to form the heat dissipation layer 6 and the face-down bonding portion 11 by etching the front side metal layer, and the back side metal layer is used as the back side metal layer 10 without etching.

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 the thermal diffusivity of the glass glaze used conventionally is 0.
It is equivalent to about 1/4 of 45 (mm ² / sec), so the heat lost to the insulating substrate side is reduced compared to the conventional case, and the ratio of the thermal energy transmitted to the thermal paper is increased, which corresponds to energy saving. it can. 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 made of SiO ₂ formed thinner than the heat storage layer 7. This SiO ₂ is an insulating material and has a thermal diffusivity about 1.53 times larger than that of TaSiO ₂ , and has the effect of quickly diffusing heat in a two-dimensional direction in order to make the heat distribution in 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.

Next, the inorganic layer 8 will be described in detail. An insulating material having a thermal diffusivity larger than that of the heating resistor 2 is provided under the heating resistor 2 (for example, a thermal diffusivity about 1.53 times larger than that of TaSiO ₂ ).
The inorganic layer 8 is formed of a SiO ₂ film. This diffuses the heat concentrated in the central portion of the heating resistor 2 to the entire heating resistor through the inorganic layer 8 having a larger thermal diffusivity than the heating resistor 2, and the inorganic layer 8 is made of an insulating material. Therefore, the temperature distribution characteristics of the heating resistor 2 can be flattened without affecting the electrical characteristics of the heating resistor 2.

In addition to SiO ₂ , insulating materials such as sialon, SiN, and Al ₂ O ₃ can be used. By the way, the thermal diffusivity of Sialon is 9.96.
(Mm ² / sec), thermal diffusivity of Al ₂ O ₃ is 12.1 (mm ² / sec), SiN
Has a thermal diffusivity equal to or higher than that of Sialon. SiO ₂
The film is useful because it has advantages such as easy etching, low cost (target, etc.), and good adhesion to the polyimide resin of the heat storage layer.

The above-mentioned thermal diffusion will be described with reference to FIGS. 3, 8 and 9 by comparing the case with the inorganic layer 8 and the case without the inorganic layer 8.

FIGS. 8 (a) and 8 (b) are views showing the printing states with and without print blur, respectively. As shown in FIG. 8 (b), the print faint 81 is generated when only a part of the print dot size of the heating resistor does not develop, and a colored part 82 corresponds to the print dot size.
When the ratio of is small, the print density is perceived by the human eye as being light.

FIG. 9 shows the case where the inorganic layer 8 is not provided, (a) is a plan view of the heating resistor 2, and (b) and (c) are the temperatures in the XX ′ and YY ′ directions of FIG. The distribution is shown. still,
This temperature is measured by an infrared thermometer.

As shown in FIGS. 9B and 9C, the current density is concentrated in the central portion of the heating resistor 2, so that the amount of heat generated in the central portion is increased and the heating resistor 2 is used as a material. Ta
The fact that the temperature coefficient of resistance of SiO ₂ exhibits a negative characteristic also interacts, and the current is further concentrated in the center of the heating resistor.
Print fading occurs as described with reference to FIG.

This phenomenon does not occur in the thermal recording apparatus using the conventional glaze ceramic substrate shown in FIG. 7. This is because the thermal diffusion coefficient of the polyimide heat storage layer 7 disposed below the heating resistor 2 is This is because the amount of heat diffused through this portion to the entire heating resistor 2 is very small because it is very low.

It should be noted that this print fading occurs only at the start of printing,
When printing is performed for a certain period of time, the temperature of the insulating substrate 1 and the like rises and the printing does not occur.

On the other hand, FIG. 3 shows the case in which the inorganic layer 8 is provided as in the embodiment of the present invention. Like FIG. 9, (a) is a plan view of the heating resistor 2, (b) and (c). ) Are (a)
The temperature distributions in the directions X-X 'and Y-Y' in the figure are shown.
This temperature is also measured by an infrared thermometer.

As shown in FIG. 3 (b), XX ′ of the heating resistor 2
The temperature distribution in the direction is almost the same as that in the case where the inorganic layer 8 in FIG. 9B is not provided (this is because aluminum wiring electrodes having a large thermal diffusivity are formed at both ends of the heating resistor). However, as clearly shown in FIG.
By providing the inorganic material layer 8 in the Y'direction, the averaged value can be quickly averaged to prevent print blur.

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 polyimide heat storage layer 7 is 0.11 (mm ² / sec), and the film thickness is 6 to 10 μm in the polyimide heat storage layer 7 as compared with 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 copper 6
Thickness of 9μm, thermal diffusivity of 112.8 (mm ² / sec), heat-resistant glass epoxy substrate (insulating substrate 1) thickness of 0.8mm, thermal diffusivity of 0.
Due to the relationship of 25 (mm ² / sec), the relationship of Q ₂ > Q ₃ is established.

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
Greater than Q _1, the result, switching the applied voltage ON of energy transferred to the thermal paper side, Q ₁ at the time of OFF> Q ₂ (applied voltage
ON time) Q ₁ <Q ₂ (when the applied voltage OFF), and the it is possible to switch quickly energy.

This is established without affecting the formation of the inorganic layer 8. That is, the heat transferred from the TaSiO ₂ layer (heating resistor 2) to the lower layer is blocked by the polyimide heat storage layer 7 having a thermal diffusivity, so that the heat quantities of Q ₁ and Q ₂ are not influenced by the inorganic layer 8. The heat transferred to the upper layer is TaSiO ₂ due to the inorganic layer 8.
Although diffused in (heat-generating resistor 2), the total amount of heat transferred to the thermal paper remains unchanged. Therefore, the formulas of Q ₁ > Q ₂ > Q ₃ when ON, Q ₂ > Q ₁ and Q ₂ > Q ₃ when OFF are always satisfied.

In view of the above points, in the thermal recording device using the conventional glaze ceramic substrate, the thermal diffusivity is 9.96 (mm ² / sec) for sialon (protective film) and 1 for the alumina ceramic substrate.
2.1 (mm ² / sec), 0.45 (mm ² / sec) in glass glaze, which are closer to each other compared to the structure of the present invention. Therefore, Q ₁ > Q ₂ (when applied voltage is ON), Q ₁ < Q ₂ (when the applied voltage is OFF)
Although the condition of is satisfied, the printing efficiency is poor because the difference between Q ₁ and Q ₂ in the ON and OFF states is not large. However, the present invention structure because it uses a sufficiently high copper low enough polyimide resin and the thermal diffusivity of the thermal diffusivity, and above for Q ₁ in
The difference from 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 backside metal layer 10 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 10, and then the back surface metal layer.
The heat dissipation is further improved by transmitting heat to the heat sink 113 bonded to the lower surface of 10.

Next, FIG. 4 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. 4 (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. 4 (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 the heat quantity 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. 4C, 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 remarkably recognized as compared with the one without the heat dissipation structure (4th
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. 5, (a) and (b) show the characteristics between the applied power and the print density in the 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, the insulating substrate also retains heat, and as a result, the thermal recording apparatus can be driven with less energy as compared with the conventional case.

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 copper foil 6A, and the aluminum foil portion 14 is removed by etching after the metal foil is laminated.

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. 6 (c), in order to form the copper layer 6A on the surface of the insulating substrate 1 into a predetermined pattern, electro.
Resist formation by deposition method, copper etching,
The resist is peeled off sequentially. Although the heat dissipation layer copper layer 6A and the face-down bonding portion copper layer 11A are simultaneously formed by this patterning step, the copper layer 10 on the back surface of the insulating substrate 1 is formed.
A is not patterned, and is left in the entire area from the viewpoint of improving the thermal characteristics of the substrate and improving the warp of the substrate due to heat.

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 carrying out this infrared irradiation step is that the thermal decomposition temperature of the insulating substrate 1 is up to 350 ° C. and the polyimide resin curing temperature is close to 300 ° C., so that it cannot be directly heated in an oven. .

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 polyimide precursor 15 is semi-cured by heating stepwise at ℃ and 200 ℃. 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. After that, the steps of forming a resist, exposing, developing, and etching a 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. 6 (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. 6 (i), SiO is formed by plasma CVD.
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 the substrate is divided into a predetermined size by the dicing method, the divided substrate is connected by the face-down bonding method to the face-down bonding portion 11 by the face down bonding method by the infrared furnace as shown in FIG. To do. Further, after the control element 3 is soldered to the control element 3 with the epoxy resin 13, the double-sided flexible circuit board 110
Is sandwiched between the head cover 112 and the heat sink 113 and fixed with screws to connect the head portion of the thermal recording apparatus to the flexible circuit board 110 for inputting / outputting signals.

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, the insulating substrate is formed of a heat-resistant resin having a low thermal diffusivity, so that the cost of the thermal recording apparatus can be reduced, and the thermal diffusivity is provided under the heating resistor portion. By having a sufficiently low polyimide heat storage layer and a heat dissipation layer formed of a copper foil on an insulating substrate, low power consumption and high-speed printing can be realized, and a heating resistor below the heating resistor. Since the inorganic material layer is formed of a material having a higher thermal diffusivity than that of the material, it is possible to prevent print blur at the start of printing and provide a thermal recording device having high print quality.

[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, FIGS. 3A to 3C are views for explaining the temperature distribution of a heating resistor in the present embodiment, and FIG. FIG. 4A is a thermal response characteristic diagram when a printed wiring board having no heat dissipation structure is used, and FIG. 4B is a thermal response characteristic when a printed wiring board having a heat dissipation layer and a back electrode layer is used. Figure, Figure 4 (c)
Is a thermal response characteristic diagram when a printed wiring board having only a heat dissipation layer is used, FIG. 5 is a diagram showing a relationship between print power and print density in one embodiment of the present invention and a conventional example, FIG. a) to (i) are manufacturing process diagrams of a thermal recording device according to an embodiment of the present invention, FIG. 7 is a structural diagram of a conventional thermal recording device using a ceramic substrate, and FIGS. 8 (a) and 8 (b) are printing. FIGS. 9 (a) to 9 (c) are diagrams for explaining the blurring, and FIGS. 9 (a) to 9 (c) are diagrams for explaining the temperature distribution of the heating resistor in the absence of the inorganic layer. 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, 8 ... Inorganic material layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiko Yoshikawa 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) References JP 61-181657 (JP, A) JP 61- 181658 (JP, A) JP 3-121862 (JP, A) JP 64-97665 (JP, A) JP 4-1064 (JP, A) JP 3-75157 (JP, A) JP-A-3-65356 (JP, A) JP-A-62-288060 (JP, A) Actually open 2-86740 (JP, U)

Claims (2)

(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 apparatus 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 heating resistor is convex on the insulating substrate. The heat dissipation layer formed by the copper foil of the insulating substrate, the heat storage layer made of polyimide resin, and the thermal diffusivity that is substantially the same as that of the heat generating resistor and is located so as to be located at the tip of the heat generating resistor. A heat-sensitive recording apparatus comprising: an inorganic material layer having a layered structure and a heat generating resistor formed on the inorganic material layer. 2. The thermal recording apparatus according to claim 1, wherein the inorganic material layer is formed of a SiO ₂ film.