JPH0584223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glazed ceramic substrate, and more particularly to a glazed ceramic substrate used for thermal print heads and the like on which thin film circuits are mainly formed.

[Prior Art] Conventionally, thermal print heads have been made by forming heat generating resistors and other circuits on a glazed ceramic substrate with a glass layer on an alumina substrate with high heat dissipation, and also by forming heat generating resistors and other circuits on a glazed ceramic substrate with a glass layer on an alumina substrate with high heat dissipation. It is manufactured by coating it with a protective film.

The structure of a conventional glazed ceramic substrate for a thermal print head will be explained with reference to FIGS. 12 to 14.

The thermal print head shown in FIG. 12 is mainly used for facsimiles, and has a heating resistor 5 and a lead portion 6 provided on a flat glass layer 2b formed on a substrate 1. 1st
The thermal print head shown in Figure 3 is used in a so-called thermal print head for serial printers that has multiple rows of heating resistors 5 for high-speed printing, and has a convex glass layer only in the area where the heating resistors 5 are formed. 3b, a so-called partial glaze layer is formed. The glaze layer serves as a heat storage layer to control the heat generation state of the resistance heating element 5.

By the way, in the thermal print head shown in FIG. 12, the heating resistor 5 does not adhere sufficiently to the thermal paper (not shown), so the heating resistor 5 is formed as shown in FIGS. 13 and 14. The glaze layer is formed in a convex shape.
As shown in FIG. 13, if a partial glaze layer is provided only on the area where the heating resistor 5 is formed, and the other leads 6 etc. are wired on a non-glazed substrate, the adhesion of the heating resistor 5 to the thermal paper can be improved. At the same time,
Since the lead portion 6 is directly wired to the substrate, heat dissipation is improved and high-speed printing can be supported.

[Problems to be Solved by the Invention] However, in the thermal print head shown in FIG. 13, the lead portion 6 that connects the heating resistor 5 at both ends is formed directly on the substrate 1, for example, an alumina substrate. In addition, it is susceptible to adverse effects caused by alumina substrates. In other words, the surface roughness of the alumina substrate is generally rougher than that of the glaze layer, and since there are usually pinholes in the alumina substrate,
If the lead portions are formed directly on the alumina substrate, short circuits between the lead portions are likely to occur due to breakage of the lead portions or defective etching during the pattern forming process.

In addition, in the thermal print head shown in FIG. 14, a flat glass layer 2 which is a glaze layer
b and the convex glass layer 3b are made of the same glass material, but when the glaze is fired, the glass in the part that should be convex flows and the convex part collapses and the whole becomes flat, and the desired convexity is not achieved. It is difficult to obtain a glazed ceramic substrate with a large area. This was demonstrated through experiments conducted by the inventors.

Furthermore, in JP-A No. 60-42069, glass paste is coated in a planar manner as a first layer over the entire surface of a ceramic substrate, and then glass paste is coated in a convex shape as a second layer on top of the glass paste, and the glaze is fired. As shown in FIG. 15, the planar glass layer 2
A method for obtaining a glazed ceramic substrate having a convex glass layer 3b and a convex glass layer 3b is disclosed. Glass with a high softening point may have a higher coefficient of thermal expansion than glass with a relatively low softening point, but in general, glass with a low softening point tends to have a higher coefficient of thermal expansion. be. Therefore, the planar glass layer 2b
Assuming that the convex glass layer 3b has a high softening point and the convex glass layer 3b has a low softening point, the convex glass layer 3b that is subjected to glaze firing generally has a larger coefficient of thermal expansion than the planar glass layer 2b, so the convex glass layer 3b has a higher softening point. There is a possibility that tensile stress acts on the shaped glass layer 3b and cracks occur in the convex shaped glass layer 3b. In particular, this portion forms a heating resistor and is not preferred because thermal stress is constantly generated. In the figure, on the other hand, if the planar glass layer 2b is made of glass with a low softening point, the problem of stress caused by the coefficient of thermal expansion as described above can be solved. However, since the planar glass layer 2b is thin, it is fired excessively during glaze baking, and the reaction (or mutual diffusion) between the planar glass layer 2b and the alumina substrate becomes large, resulting in a large warpage of the resulting substrate, or A bubbling phenomenon may occur due to a small amount of gas contained in the planar glass layer 2b.

On the other hand, there is a tendency for the glass for glazing glazed ceramic substrates to have a high softening point overall, and the types of glass that can be used are extremely limited if chemical resistance, weather resistance, etc. are taken into account. It becomes even more difficult to meet the various properties required when glasses selected in this way are used for thermal print heads. Therefore, the conventional method has the disadvantage that the selection range of glass is extremely narrow.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and it is possible to reliably form a convex glaze (glass) layer on which a heating resistor is formed, and to form an aluminium oxide layer in a portion where a lead portion is to be formed. An object of the present invention is to provide a glazed ceramic substrate which is not affected by the adverse effects of the substrate surface.

[Means and effects for solving the problem] The above object is to provide a glazed ceramic substrate in which a glass layer is formed on a ceramic substrate,
A glass comprising a convex glass layer having a low softening point and a planar glass layer having a high softening point formed around the convex glass layer, the glass forming the convex glass layer and the planar glass. This is achieved by using a glazed ceramic substrate, which has a softening point difference of 30 to 100° C. with the glass forming the layer, and is formed by simultaneous firing.

Hereinafter, the present invention will be explained in detail based on the drawings.

In the present invention, as shown in FIG. 2, for example, a glass paste containing glass powder having a low softening point is applied to a convex portion 3a of a desired height on an alumina substrate 1.
The coating is applied in a convex shape so that the convex portion 3
A thin layer of glass paste containing glass powder having a high softening point is coated around a to form a flat portion 2a. In the present invention, a glass with a low softening point and a glass with a high softening point mean that one glass has a higher softening point than the other glass formed on the same glazed ceramic substrate. It is not meant to have a range of softening points. As a method for coating the glass paste, a method of screen printing the glass paste through a patterned screen, a spray method using a mask, etc. are appropriately used. Next, the glass paste is fired at a temperature equal to or higher than the softening point of the glass powder contained therein to form a planar glass layer 2b as shown in FIG.
A glazed ceramic substrate having a convex glass layer 3b is obtained.

In the present invention, the planar glass layer 2b needs to have a high softening point, and the convex glass layer 3b needs to have a low softening point. Generally, in the case of the same type of glass, the thicker the glass, the higher the glaze firing temperature and the longer the firing time, otherwise pinholes etc. are likely to remain on the glaze surface.
It is not desirable to use glass with a high softening point as the thick convex glass layer 3b. Furthermore, by using a glass having a high softening point as the thin planar glass layer 2b, the required shape of the convex portions can be easily obtained even by simultaneous firing, and the smoothness of the flat portions can also be obtained.

The difference in softening point between the glass forming the planar glass layer 2b and the glass forming the convex glass layer 3b varies depending on the temperature conditions of glaze firing, etc.
Preferably the temperature is ~100°C. Within this range, the planar glass layer 2b and the convex glass layer 3b can be formed by simultaneous firing, thereby simplifying the manufacturing process and reducing manufacturing costs. Moreover, if the difference in softening point is less than 30° C., mutual diffusion between the convex glass layer 3b and the planar glass layer 2b will increase, making it difficult to obtain the necessary convex shape. If the difference in softening points exceeds 100°C, the planar glass layer 2b with a high softening point will not be sufficiently smoothed during simultaneous firing, leaving pinholes etc. on the surface, or the convex glass layer with a low softening point will become flat. 3b flows too much, and mutual diffusion between the planar glass layer 2b, which has a high softening point, and its boundary increases, making it difficult to obtain the necessary convex shape.

Temperature difference exceeding 100℃, e.g. 200℃
℃ or higher, as shown in Fig. 2, only the flat part 2a is coated in advance and glaze firing is performed at a high temperature, and then the convex part 3a is further coated and fired to match the convex part 3a. By baking the glaze at a high temperature, the planar glass layer 2b shown in FIG. 1 can be made sufficiently smooth, and the occurrence of pinholes on the surface of the planar glass layer 2b due to insufficient baking can be suppressed. However, since simultaneous firing is not possible, manufacturing costs are high, and the flat part 2a must be fired at a higher temperature than necessary, which reduces the reaction (mutual diffusion) between the glass and alumina substrate. As a result, the substrate warps to a large extent, making it difficult to use it as a thermal print head.

In the present invention, the thickness of the thin planar glass layer 2b is preferably 2 to 50 μm. If the thickness is less than 2 μm, parts with no glass are likely to be formed, and if it exceeds 50 μm, the glass portion with a high softening point may be insufficiently fired, although it depends on the difference in softening point with the glass layer with a low softening point. Alternatively, the glass portion with a low softening point may be fired excessively, resulting in intense flow, making it difficult to form convex portions of the required shape. Further, the height of the convex glass layer 3b is preferably 20 to 100 μm. The reason is that if the thickness is less than 20 μm, heat storage becomes too small.
This is because if the thickness exceeds 100 μm, heat storage becomes too large.

In the present invention, the planar glass layer 2b and the convex glass layer 3b may be formed so as to partially overlap as shown in FIGS. 3 and 4.

In FIG. 3, since the lower layer is generally a glass layer with a low coefficient of thermal expansion and a high softening point, the stress caused by the difference in thermal expansion causes the convex glass layer 3 to
This is disadvantageous because tensile stress tends to act on b. However, in this case, if the overlap portion is within 0.2 mm, no practical inconvenience will occur. To create the glazed ceramic substrate shown in Fig. 3, glass paste is coated and glazed fired as shown in Fig. 5.
As shown in the figure, valleys A tend to occur near the boundary between the planar glass layer 2b and the convex glass layer 3b. Tanibe A
The depth varies depending on the thickness of the glass paste that formed the convex and flat parts, the firing temperature, etc., but the maximum depth is 20 μm.
It will be about. To create the glazed ceramic substrate shown in Figure 4, glass paste is coated and glazed fired as shown in Figure 6.
In this case, since the upper layer is a glass layer having a low coefficient of thermal expansion and a high softening point, not only is there no disadvantageous stress caused by the difference in expansion, but there is also the advantage that the valley A shown in FIG. 7 can be made smaller.

Next, other embodiments of the present invention will be described based on FIGS. 8 to 10.

As shown in Figure 8, the glass paste is placed between the flat part 2a and the convex part 3a so as to provide a gap B of 0.5 mm or less.
A glass powder or vehicle-only solution 4 is applied to the gap B as shown in FIG. After the glass powder in the flat part 2a and the convex part 3a has moved into the solution 4 as much as necessary to make the glass surface on the substrate continuous after firing, it is immediately transferred to a drying process to prevent excessive movement. After solidifying the whole
Bake the glaze. Then, as shown in FIG. 10, the flat glass layer 2b and the convex glass layer 3b form a continuous glass surface, the valleys A become shallow, and the glass layer 3b is formed into a desired shape. Obtainable.

The solution applied to the above gap B varies depending on the coating method of the glass paste, but in the case of coating by screen printing, for example, the solution applied to the gap B is compatible with the glass paste prepared for printing. A solution prepared by dissolving it in a highly volatile solvent such as acetone or toluene is used. If necessary, a suitable surfactant is added to this solution to lower the viscosity, and the solution is prepared so that even if a small amount is applied, it is sufficiently spread over the entire gap B. Further, it is necessary to adjust the amount of volatile solvents such as acetone and toluene in order to prevent excessive movement of glass powder. In addition, when coating with a solution that does not contain glass powder,
A solution in which only the vehicle is dissolved in acetone or the like can be used.

The advantage of this method is that when the thickness of the protrusion 3a is relatively thick and the difference between the thickness of the protrusion 3a and the thickness of the flat part 2a is small as shown in FIG. It is possible to prevent the shape of the resulting glass layer from being unnecessarily distorted due to the glass layer flowing in the opposite direction. That is, if the above method is not adopted, the entire glass surface tends to be flat as shown in FIG. 11, but if the above method is adopted, the convex glass layer is not formed as shown in FIG. The portion corresponding to 3b can maintain a fairly clear convex shape.

Although the same effect can be obtained even if the above-mentioned interval is 0.5 mm or more, the shape of the convex glass layer 3b is easily distorted, and there is no special advantage in manufacturing.

[Examples] Hereinafter, the present invention will be specifically described based on Examples.

Example 1 A glass paste containing glass powder with a softening point of 920°C and a glass paste containing glass powder with a softening point of 850°C were coated to form the flat portions 2a and convex portions 3a shown in FIG. 2, respectively. The coating method uses a screen printing method to mix and stir each glass powder through a 325 mesh (JIS) sieve and a commercially available vehicle B-70 (product name: Goo Kagaku) to form a paste. Depending on the glaze firing, the flat glass layer will be approximately 20μ
m, printed so that the convex glass layer was about 50 μm.

Next, the thus coated flat portions 2a and convex portions 3a were simultaneously fired at 1200° C. for 1 hour.

The obtained glazed ceramic substrate has a cross-sectional shape as shown in FIG.
The thickness of b is 22 μm, and the thickness of convex glass layer 3b is
The glass surface was 48 μm, and the thickness near the valley A was 10 μm, and the entire glass surface was sufficiently smooth.

Example 2 Using the same glass and printing paste as in Example 1, glass coating was performed as shown in FIG. 6 to obtain a glazed ceramic substrate as shown in FIG. 4.

Coating with the glass paste was carried out so that the planar glass layer 2b had a thickness of about 10 .mu.m and the convex glass layer 3b had a thickness of about 50 .mu.m after the glaze was fired. At this time, the width d of the overlapped portion in FIG. 6 was set to 0.1 mm, and the thickness e was set to be the same as the thickness of the flat portion 2a. The conditions for firing the glaze were the same as in Example 1.

The obtained glazed ceramic substrate has a cross-sectional shape as shown in FIG.
b and the thickness of the convex glass layer 3b are each 12μ.
m and 50 μm, and the thickness near the valley portion A was not as thin as the substrate obtained in Example 1.

Example 3 A glass paste containing glass powder with a softening point of 850°C and a glass paste containing glass powder with a softening point of 800°C were printed by a printing method so as to form the flat portions 2a and convex portions 3a shown in FIG. 8, respectively. It was coated. Gap B was coated with a paste containing a small amount of glass powder having a softening point of 850° C., that is, a paste prepared at a ratio of 1 part by weight of glass powder to 3 parts by weight of vehicle by screen printing. The glass content in this paste was 1/10 to 1/8 of that of the glass paste in which the flat portions 2a and convex portions 3a were formed.

The coating thickness is set so that the planar glass layer and convex glass layer after glaze firing are about 15 μm and about 30 μm, respectively, and regarding the above gap B, assuming that only gap B is coated (flat part 2a and convex part 2a) (assuming that the glass component does not flow in from part 3a), the coating was applied so that the thickness of that part would be approximately 2 μm after firing.

The thus coated substrates were then co-fired at 1130° C. for 1 hour.

The obtained glazed ceramic substrate was
It had the cross-sectional shape shown in the figure, and the thicknesses of the planar glass layer 2b and the convex glass layer 3b were 15 μm and 28 μm, respectively, and the thickness near the valley A was 8 μm. Further, the shape of the convex glass layer 3b could be reliably formed, and the glass surface was continuous.

[Effects of the Invention] As explained above, according to the present invention, the convex glaze layer on which the heating resistor is formed is reliably formed, and the portion where the lead portion is formed is not adversely affected by the surface of the alumina substrate. A glazed ceramic substrate can be provided. When the glazed ceramic substrate of the present invention thus obtained is used for a thermal print head, the heat is transferred well to the thermal paper, and at the same time, the accumulated heat is well dissipated, thereby increasing the printing speed. can be achieved.

In addition, since high softening point glass and low softening point glass are used, the range of selection of glass types to obtain the required properties and the range of selection in the development of glass compositions are expanded, and there are limitations on materials compared to conventional methods. becomes less.

Furthermore, if the glass layer is formed by co-firing using glass pastes whose softening points differ within 30 to 100°C, the manufacturing process of the substrate can be simplified and the manufacturing cost can be reduced.

[Brief explanation of drawings]

Figures 1, 3, 4, 7 and 10
The figures are each a cross-sectional view of one embodiment of the glazed ceramic substrate of the present invention, FIG. 2 is a cross-sectional view showing the state of the glazed ceramic substrate shown in FIG. 1 before firing, and FIG. Cross-sectional view showing the state before firing of the glazed ceramic substrate shown in FIG.
The figure is a cross-sectional view showing the state of the glazed ceramic substrate shown in FIG. 4 before firing, FIGS. 8 and 9 are cross-sectional views explaining the method for producing the glazed ceramic substrate shown in FIG. 10, and FIG. Cross-sectional view showing a reference example of a glazed ceramic substrate, No. 12
14 are cross-sectional views of a conventional thermal print head, and FIG. 15 is a cross-sectional view of a conventional glazed ceramic substrate. DESCRIPTION OF SYMBOLS 1... Substrate, 2a... Flat part, 2b... Planar glass layer, 3a... Convex part, 3b... Convex glass layer, 4... Solution, 5... Heat generating resistor, 6... Lead part , A... valley, B... gap.

Claims (1)

[Scope of Claims] 1. A glazed ceramic substrate formed by forming a glass layer on a ceramic substrate, comprising a convex glass layer having a low softening point and a high softening point formed around the convex glass layer. a planar glass layer, the difference in softening point between the glass forming the convex glass layer and the glass forming the planar glass layer is
A glazed ceramic substrate characterized in that it is formed by simultaneous firing at a temperature of 30 to 100°C. 2. The glazed ceramic substrate according to claim 1, wherein the convex glass layer and the planar glass layer are formed so as to partially overlap. 3 The convex glass layer and the planar glass layer are coated with glass paste in a convex and planar manner so as to provide a gap of 0.5 mm or less, and the gap contains glass powder and a vehicle, or only a vehicle. The glazed ceramic substrate according to claim 1, which is formed to have a continuous glass surface by applying a solution and firing the glaze.