JPH01154770A - Thermal head - Google Patents

Abstract

PURPOSE:To enhance reliability and thermal efficiency, by improving the heat resistance and the adhesion to a ceramic substrate of a polyimide resin layer provided on the ceramic substrate as a heat insulating layer controlling a heat dissipation and heat accumulation. CONSTITUTION:A heat resistant resin layer 2 is obtained by the ring opening polyaddition reaction of, for example, an equimolar mixture of a biphenyl tetracarboxylic acid dianhydride and an aromatic diamine. A varnish obtained by dissolving a polyamic acid serving as a precursor of a polyimide resin in an appropriate organic solvent is used so as to be applied on a ceramic substrate, thereafter being calcined, dehydrated, and cyclized to form an aromatic polyimide resin having a biphenyl structure in a main chain. Especially, an aromatic polyimide resin obtained by using a p-phenylenediamine minimizes the difference in thermal expansion coefficient from the ceramic substrate 1, thus more effectively preventing a peeling.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention involves forming a polyimide resin layer as a heat insulating layer on a highly thermally conductive ceramic support, and forming a polyimide resin layer on the polyimide resin layer. The present invention relates to a highly efficient thermal head formed with a large number of heating resistors.

(Prior Art) In recent years, thermal heads have come to be widely used in various recording devices such as printers for facsimiles and word processors, taking advantage of advantages such as low commission rates, low maintenance, and low running costs. On the other hand, these devices are required to be smaller, lower in price, and lower in power consumption, and therefore thermal heads are also desired to be small, inexpensive, and highly efficient.

For such a thermal head, a glazed glass layer with a thickness of about 50 to 150 μm is formed on a ceramic substrate with a thickness of about 0.5 to 1.0 mm with an Al103 purity of 90% or more, and a large number of A heating resistor and a conductor connected to the heating resistor are often used. Here, the glazed glass layer serves as a heat-retaining layer that controls heat dissipation and heat accumulation.

By the way, in a thermal head that uses this glazed glass layer as a heat insulating layer, there is a limit to its thermal resistance as a heat insulating layer, so in order to increase the efficiency of the thermal head such as increasing printing speed while satisfying printing performance. For example, JP-A-52-100245 and JP-A-56-164876
As described in the above publication, it is known that a resin having a low thermal conductivity, such as an aromatic polyimide or an epoxy resin, may be used as the heat insulating layer.

However, the method of using such a heat-resistant resin as a heat insulating layer has not yet reached the level of practical use. This is instantaneous 400℃~500℃, regular use 250℃~350℃
It has high heat resistance that can withstand the operating conditions of thermal heads that operate at ℃, has excellent adhesion to ceramic supports, and is highly reliable as it does not deteriorate or peel off even with repeated application of heat. This was due to the lack of heat-resistant resin.

According to the experiments of the present inventors, for example, JP-A-56-16
Product name: Trainice #2, described in Publication No. 4876
A polyimide resin layer formed on an Al2O3 substrate using a polyimide varnish (polyamic acid) of was not obtained. In addition, when we measured the thermal decomposition initiation temperature using a polyimide film obtained from this polyimide varnish by thermal gravity measurement, it was as low as about 410°C, which was not enough to withstand the operation of the thermal head as described above. .

(Problems to be Solved by the Invention) As described above, in a thermal head formed by forming a polyimide resin layer on a ceramic support and forming a large number of heating resistors on this polyimide resin layer, Although it has the advantage of excellent thermal efficiency due to its thermal diffusivity, the heat resistance of the polyimide resin itself is not sufficient to withstand the harsh operating temperature conditions of the thermal head, and it also lacks reliability, such as lacking adhesive strength with the ceramic support. The problem was that it was low.

The present invention was made in order to solve these problems, and it improves the heat resistance of a polyimide resin layer provided on a ceramic support as a heat insulation layer that controls heat dissipation and heat storage, and improves the ceramic support. The objective is to provide a high-performance thermal head that improves adhesive strength with the body, is highly reliable, and is steeped in thermal efficiency.

[Structure of the Invention] (Means for Solving the Problems) The thermal head of the present invention includes a highly thermally conductive ceramic support, a heat-resistant resin layer formed on the ceramic support, and a heat-resistant resin layer formed on the heat-resistant resin layer. In the thermal head comprising a plurality of heat generating resistors formed in the heat generating resistor and a 7!3 power rest connected to each heat generating resistor, the heat resistant resin layer is made of biphenyltetracarboxylic dianhydride and aromatic diamine. It is characterized by being made of an aromatic polyimide resin having a biphenyl structure in the main chain formed by a dehydration cyclization reaction of a polyamic acid through a ring-opening polyaddition reaction with a polyamic acid.

That is, the heat-resistant resin layer in the present invention is made by using a suitable polyamic acid, which is a precursor of a polyimide resin, obtained by ring-opening polyaddition reaction of, for example, an equimolar mixture of biphenyltetracarboxylic dianhydride and aromatic diamine. Consists of an aromatic polyimide resin with a bis-1-nyl structure in the main chain formed by applying a varnish dissolved in an organic solvent onto a ceramic support, followed by firing and cyclodehydration reaction. It is something.

Examples of the aromatic diamine include diaminodiphenyl ether, diaminodiphenylsulfone, p-phenylenediamine, and tophenylenediamine, but p-phenylenediamine is the most thermally superior when used, and also works well with ceramic supports. The difference in coefficient of thermal expansion, which causes peeling, is also reduced, so its use is desirable.

In addition, in the thermal head of the present invention, the following
By applying either of the above, it is possible to further improve the adhesion between the heat-resistant resin layer and the ceramic support, which is preferable.

■ Introducing 81 groups into the molecular structure of a polyimide resin that has a biphenyl structure in its main chain. This SiM-introduced polyimide resin can be used, for example, during the synthesis of the above-mentioned polyamic acid, by adding a portion of the aromatic diamine to an arbitrary ratio of
Desirably about 0.05 to 10 of the aromatic diamine component
It can be formed by using a polyamic acid obtained by substituting a diamine having a Si group and carrying out a ring-opening polyaddition reaction within a range of mol %.

The Si group-containing diamine used for this Si group introduction may be, for example, a general formula (wherein R is a divalent organic group, R' is a monovalent organic group,
n indicates a positive number. ) Bisaminosiloxane represented by:

(2) At least one of a silane compound having an amine bond and a silane compound having a urea bond is contained as a silane coupling agent component in a polyimide resin having a biphenyl structure in the main chain.

This silane coupling agent can be used, for example, in a varnish containing the above-mentioned polyamic acid as a main component, with a solid content of approximately 0.05 to 0.05.
It can be contained by adding and using it in a range of 10% by weight.

Examples of the silane compound having an amino bond added as the silane coupling agent component include γ-aminopropyltriethoxysilane and N-7enyl-γ-aminopropyltrimethoxysilane, and examples of the silane compound having a urea bond include , for example γ-ureidopropyltrimethoxysilane.

■ Approximately
An active metal layer made of Cr, Ti, etc. having a thickness of 00 Å to 10,000 Å is interposed.

In addition, SiX into the molecular structure of the polyimide resin mentioned above
The introduction of and the addition of a silane coupling agent into the polyimide resin described in (1) above can further improve the adhesion between the heat-resistant resin layer and the thin film formed on the heat-resistant resin layer.

Highly thermally conductive ceramic supports used in the present invention include aluminum oxide (Al10a), aluminum nitride (^IN), silicon nitride (Si3N4), silicon carbide (SiC), sialon (SiAION),
An example is a ceramic sintered body whose main component is beryllium oxide (Bed) or the like.

(Function) By using the above means, the aromatic polyimide resin having a biphenyl structure in the main chain used as the heat-resistant resin layer in the thermal head of the present invention has a heat shrinkage rate even when subjected to cold and hot cycles. Since it is small and the difference in thermal coefficient of coefficient with respect to the ceramic support is small, it is possible to effectively prevent peeling, which is thought to be caused by interfacial stress caused by the difference in coefficient of thermal expansion. In addition, the aromatic polyimide resin obtained by particularly using p-phenylene diamine as the aromatic diamine component, which is one of the components in polyamic acid synthesis,
The difference in coefficient of thermal expansion with the ceramic support becomes the smallest, and peeling can be more effectively prevented. Furthermore, by using a polyamic acid synthesized by replacing a part of the aromatic diamine with a diamine having a Si group during the synthesis of polyamic acid, or by adding a silane coupling agent component to the polyamic acid and using it, Si
The base acid component further strengthens the adhesion.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the main parts of a thermal head according to an embodiment of the present invention. In the figure, 1 is a ceramic support having high thermal conductivity;
On top, a polyamic acid represented by the following formula (I-1) obtained by ring-opening polyaddition reaction of an equimolar mixture of biphenyltetracarboxylic dianhydride and p-phenylenediamine was dissolved in an organic solvent. or the following polyamic acid varnish synthesized by replacing p-phenylenediamine with bisaminodisiloxane represented by the following formula (I) in a range of approximately 0.05 to 10 mol% during the synthesis of this polyamic acid. A polyamic acid varnish prepared by dissolving a polyamic acid having a Si group introduced into the molecular structure represented by the formula (I[l-1) in an organic solvent, or the above-mentioned (I-1
) 0.0.
05~10f! By coating and baking a polyamic acid varnish added and dispersed in a range of ffi%, a thickness of approximately 5μ11 to 5 μm made of an aromatic polyimide resin represented by the following formula (I-2) or (II-2) is obtained. 50μm1
The heat-resistant resin layer 2 preferably has a thickness of 10 to 30 μm. And this heat-resistant resin 1! 5i02 on top of ff2
, β-3iAION, etc., and Ta-3
A heat generating resistor 4 made of i02, Ti-3i02, etc. is formed in order, and individual electrodes 6 made of ^11At-3i-Cu etc. A common electrode 7 is formed, and an anti-oxidation film/wear-resistant film 8 made of a 5i-0-N compound or the like is formed so as to cover at least this heat generating part 5.

(Left below) If N -C-Nil (C112) 35i
(OClh) 3 -- (IV) In the formula, c, m, and n represent positive numbers (the same applies below).

In this thermal head, by applying a pulse voltage between the individual electrodes 6 and the common electrode 7 at predetermined time intervals, the heat generating resistor 4 of the heat generating section 5 generates heat, thereby performing print recording.

This thermal head is manufactured, for example, as follows.

First, a ceramic support 1 of a predetermined shape and a thickness of about 0.85 Im, made of a ^1203 sintered body with a purity of 96%, for example, is washed and dried, and then the above-mentioned polyamic acid is mixed with tomethyl-2-bi0ridone. The viscosity was adjusted to a predetermined value using a solvent such as, and coated on the ceramic support 1 to a predetermined thickness using a roll coater, spin-on coater, etc., and then heated at 50"CX for 1 hour using a firing furnace at 80℃×30
minutes, then 120°C x 30 minutes, 250°C x 1 hour, 45
Heating was performed at 0°C for 1 hour to remove the solvent, and
The heat-resistant resin layer 2 is formed by proceeding with the dehydration cyclization reaction. At this time, if a polyamic acid is used without containing a silane coupling agent component or without introducing a Si group into its molecular structure, the surface of the ceramic support 1 has a thickness of approximately 500 Å to 10,000 Å. It is desirable to form a polyimide resin layer after forming an active metal layer such as C' or 1 by a method such as vapor deposition.

Next, a base layer 3 made of 5i02, β-3iAION, etc. with a thickness of about 500 Å to 10,000 and Ta-8i is deposited on this heat-resistant resin layer 2 by sputtering or other methods.
The heating resistor 4 is made of 02, Ti-3io2, etc., and the individual electrode 6 and the common electrode 7 are made of A1 or Al-3i-.
A conductive layer made of Cu or the like is formed. Next, after masking so that an opening that will become the heat generating part 5 is formed, a predetermined pattern is formed by wet etching, chemical dry etching, or the like. Thereafter, the masking group is removed, and an anti-oxidation film/wear-resistant film 8 made of a 5i-0-N compound or the like is formed by sputtering, for example, so as to at least cover the heat generating portion 5.

Next, in the manufacturing process of this thermal head, the adhesive strength, heat resistance, and other characteristics of the polyimide resin were evaluated.

First, using the polyamic acid obtained by the ring-opening polyaddition reaction of cyphthalic acid and p-phenylenediamine in the above-mentioned example, a polyimide resin layer (implemented Example 1) was formed into a film, and repeated thermal stress tests were conducted under the conditions of room temperature x 1 hour and 450°C x 1 hour in N2 gas, and the presence or absence of peeling of the polyimide resin layer at that time was investigated. The thermal decomposition onset temperature was measured by gravimetry, the amount of thermal shrinkage was measured, and the coefficient of thermal expansion was also measured.The results are shown in Table 1.

In addition, instead of p-phenylene diamine in the above example, m-phenylene diamine (Example 2) and diaminogenyl ether (Example 3) were used as aromatic diamine components, respectively, and polyamic acids were synthesized in the same manner. Then, a polyimide resin layer was formed under the same conditions. The characteristics of these were evaluated in the same way,
The results are shown in the numerical table.

In addition, in the comparative examples in the table, p-phenylenediamine used in the example was used as the aromatic diamine component, and pyromellitic dianhydride (comparative example 1) and benzophenonetetracarboxylic acid M were used as the tetracarboxylic acid component.
(Comparative Example 2) to synthesize each polyamic acid,
These are the results of forming a polyimide resin layer under the same conditions and conditions as in the example and performing the same evaluation as in the example.

(Left below) As is clear from the previous author, polyimide resins synthesized using biphenyltetracarboxylic dianhydride as the tetracarboxylic acid component have a higher heat shrinkage than polyimide resins using other tetracarboxylic acid components. Since the thermal expansion coefficient is small and is close to that of the ceramic support, peeling from the ceramic support when thermal stress is applied is reduced. In addition, the polyimide resin using p-phenylene diamine as the aromatic diamine component according to Example 1 has particularly excellent heat resistance, and also has the smallest difference in coefficient of thermal expansion with the ceramic support. It can be seen that peeling, which is thought to be caused by the difference, could be effectively prevented. In addition, in the polyimide resin according to other examples, 5il is present in the molecular structure.
By introducing J or adding the above-mentioned silane coupling component, adhesion strength that can be used practically as a thermal head can be obtained.

Next, the adhesion strength and heat resistance of the polyimide resin of Example 1, which had a Si group introduced into its molecular structure, and the polyimide resin of Example 1, which contained a silane coupling agent component, were evaluated.

FIG. 2 is a diagram showing the relationship between the ratio of the above-mentioned saminosiloxane in the p-phenylenediamine component, adhesion strength, and thermal decomposition initiation temperature, and FIG. FIG. 2 is a diagram showing the relationship between the amount of the agent added (% by weight based on the solid content in the polyamic acid varnish), adhesion strength, and thermal decomposition initiation temperature. In both cases, it can be seen that the adhesion strength is greatly improved.

In addition, the heating resistor of the thermal head can instantaneously heat up to 400℃~
It operates at a temperature of 500°C and a sustained temperature of 250°C to 350°C, but the results shown in Figure 2 indicate that the substitution ratio of bisaminosiloxane is preferably in the range of approximately 0.05 to 10 mol%. The results show that the addition ω of the silane coupling agent is preferably in the range of 0.05 to 10% by weight. Furthermore, addition of a silane coupling agent improves heat resistance, albeit slightly.

In addition, as the silane coupling agent component, the above-mentioned γ-
In addition to ureidopropyltrimethoxysilane, the following (
Similar effects were obtained when γ-aminopropyltrimethoxysilane represented by formula V) and N-phenyl-γ-aminopropyltrimethoxysilane represented by formula (Vl) were used.

112N-C3Hs-3i(OCzHs)3...=(
V) ◎-Nll-C3H6-8f (OCt13)
3 (VI) Next, the efficiency of the thermal head was evaluated.

First, as a conventional example, 5i02-BaO-CaO-Al1
03-8203-A glazed glass layer made of ZnO with a thickness of approximately 70 μm was formed on an Al2O3 substrate,
A thermal head was constructed by forming a base layer, a heating resistor, an electrode, and a protective film in the same manner as in this example. Then, printing is performed using a thermal head using this glazed glass layer, and a certain color is produced WJr! Based on the input power at which a value of 1 was obtained, the input power required to obtain the same degree of color development with the thermal head using the polyimide resin layer (Example 1) in this example was determined as a ratio.

The results are shown in FIG. 4 as a graph of the relationship between the input power ratio (ratio where the input power by the thermal head using the glazed glass layer is 1) and the film thickness of the polyimide resin layer.

As is clear from Figure 4, when the polyimide resin of the present invention is used as a heat insulating layer, low input power is sufficient to obtain the same color density as when using glazed glass, that is, thermal efficiency is improved. It turns out that it is excellent.

Also, from the results shown in Figure 4, the thickness of the polyimide resin layer is
It can also be seen that a range of approximately 5 μm to 50 μm is preferred.

Further, FIG. 5 shows the thermal diffusivity in the thickness direction measured using a laser flash method in order to obtain basic knowledge related to improvement in efficiency. The aromatic polyimide resin having a biphenyl structure in the main chain according to the present invention has a thermal diffusivity as low as approximately 1/10 of that of conventional glaze glass, making it possible to construct a highly efficient thermal head. it is obvious. Furthermore, it can be seen that when 81 groups are introduced into the molecular structure, the thermal diffusivity decreases slightly but roughly, and further improvement in efficiency can be expected.

In this example, an equimolar mixture of biphenyltetracarboxylic dianhydride and aromatic diamine was used, but the present invention is not limited to this, and the heat resistance and viscosity during synthesis are The mixing ratio may be changed within the allowable range of use. Further, in this example, an Al103W plate was used as the ceramic support, but the present invention is not limited to this, and ^IN, S
Similar effects can be obtained even when using other ceramic sintered bodies having high thermal conductivity such as i3N, SiC, 5iAION, BeO, etc.

[Effects of the Invention] As is clear from the above examples, the thermal head of the present invention uses a ring-opening polymer of phenyltetracarboxylic dianhydride and aromatic diamine as a heat insulating layer on a ceramic support. Since it uses a heat-resistant resin layer made of aromatic polyimide resin formed by cyclodehydration reaction of polyamic acid through addition reaction, it has sufficient heat resistance, so it can be used even under harsh thermal head operating conditions. It does not cause thermal breakdown or deterioration, and by using p-phenylenediamine as the aromatic diamine component, the difference in coefficient of thermal expansion with the ceramic support becomes small, and this difference in thermal expansion causes interfacial stress. This can effectively prevent peeling. Furthermore, during the synthesis of polyamic acid, a part of p-phenylenediamine was
By using a polyamic acid synthesized by replacing it with a diamine having il, or by adding a silane coupling agent component to this polyamic acid,
Adhesion is further strengthened. Therefore, it is possible to provide an inexpensive and highly efficient thermal head that has excellent reliability and fully takes advantage of the characteristics of polyimide resin.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of a thermal head according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the ratio of diaminosiloxane in aromatic diamine, adhesion strength, and thermal decomposition initiation temperature. Figure 3 is a graph showing the relationship between the amount of silane coupling agent added, adhesion strength, and thermal decomposition initiation temperature, and Figure 4 is a graph showing the relationship between the amount of silane coupling agent added, adhesion strength, and thermal decomposition initiation temperature. Figure 5 is a graph comparing the thermal diffusivity of the aromatic polyimide according to the present invention and the glaze glass used in the heat insulating layer of the conventional thermal head. 1... Ceramic support 2...
...Heat-resistant resin layer 3 ... Base layer 4 ... Heat-generating resistor 5 ... Heat-generating part 6 ...・・・・Individual electrode 7・・・・・・・Common electrode 8・・・・・・・Antioxidant film and anti-wear film Applicant
Toshiba Corporation Toshiba Chemical Co., Ltd. Representative Patent Attorney Satoshi Suyama - Figure 1 Thermal Diffusivity Ccd/sec) Procedure Nertt IE (self-motivated) June 21, Showa G3, Commissioner of the Japan Patent Office 5□15! 1. Indication of the case Japanese Patent Application No. 62-314347 2. Name of the invention Thermal Head 3. Person making the amendment Relationship to the case Patent applicant (3071 Toshiba Corporation Toshiba Chemical Corporation 4, Agent Chiyoda, Tokyo) Kanda Higashiyama Pill, 2-1 Kanda Tamachi, Ward Telephone O3 (254) + 039 (7784)
1 Patent Attorney Suyama Sa -5, Subject of amendment: Detailed explanation of the invention of Imm, Column 6, Contents of amendment: Detailed explanation of the invention is corrected as follows. ■ Delete [(estimated to be synthesized from pyromellitic dianhydride and 0-phenylenediamine)" on the 3rd to 4th lines of page 1. ■ In lines 7 to 10 of the same page, "Sufficient adhesive strength is as described above" [The thermal decomposition onset temperature was measured by thermogravimetry, and although it has a considerable heat resistance of approximately 510 °C] However, sufficient adhesion was not obtained and there were many cases where the adhesive peeled off immediately at this stage.'' ■ "Siphthalic acid" on page 18, line 11 is corrected to "biphenyltetracarboxylic acid."that's all

Claims (14)

[Claims] (1) A highly thermally conductive ceramic support, a heat-resistant resin layer formed on the ceramic support, a plurality of heating resistors formed on the heat-resistant resin layer, and a structure connected to each heating resistor. In the thermal head, the heat-resistant resin layer has a main chain formed by a dehydration cyclization reaction of polyamic acid through a ring-opening polyaddition reaction between biphenyltetracarboxylic dianhydride and an aromatic diamine. A thermal head comprising an aromatic polyimide resin having a biphenyl structure. (2) The thermal head according to claim 1, wherein the aromatic diamine is p-phenylenediamine. (3) The thermal head according to claim 1 or 2, wherein the aromatic polyimide resin having a biphenyl structure in the main chain has a Si group introduced into its molecular structure. (4) The aromatic polyimide resin having a biphenyl structure in the main chain into which a Si group has been introduced into the molecular structure has the aromatic 4. The thermal head according to claim 3, wherein the thermal head is formed by a dehydration cyclization reaction of a polyamic acid obtained by replacing a portion of the group diamine with a diamine having an Si group. (5) The diamine having a Si group has the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R is a divalent organic group, R' is a monovalent organic group,
n indicates a positive number. ) The thermal head according to claim 4, wherein the thermal head is a bisaminosiloxane represented by: (6) The thermal head according to claim 4 or 5, wherein the amount of the Si group-containing diamine added is in the range of 0.05 to 10 mol% of the aromatic diamine component. . (7) The aromatic polyimide resin having a biphenyl structure in the main chain contains at least one of a silane compound having an amino bond and a silane compound having a urea bond as a silane coupling agent component. A thermal head according to claim 1 or 2. (8) The silane compound having an amino bond is γ-aminopropyltriethoxysilane or N-phenyl-
The thermal head according to claim 7, characterized in that it is γ-aminopropyltrimethoxysilane. (9) The thermal head according to claim 7, wherein the silane compound having a urea bond is γ-ureidopropyltrimethoxysilane. (10) The amount of the silane coupling agent added is in the range of 0.05 to 10% by weight of the solid content in the polyamic acid. Thermal head described in Crab. (11) An active metal layer having a thickness of approximately 500 Å to 10,000 Å is provided between the highly thermally conductive ceramic support and the heat-resistant resin layer. The thermal head according to item 1 or 2. (12) The thermal head according to claim 11, wherein the active metal is made of either Cr or Ti. (13) The thickness of the heat-resistant resin layer is 5 μm to 50 μm (
7) The thermal head according to claim 1, which is a range. (14) A patent claim characterized in that the highly thermally conductive ceramic support is made of a ceramic sintered body containing any one of aluminum oxide, aluminum nitride, silicon nitride, silicon carbide, sialon, and beryllium oxide as a main component. The thermal head according to item 1.