JPH05268A - Method for manufacturing resin-coated substrate - Google Patents

Abstract

(57) [Summary] [Structure] Apply polyamic acid varnish to the supporting substrate,
After removing the solvent in the polyamic acid varnish coating film applied to the supporting substrate by heating at a temperature that does not imidize polyamic acid, the polyamic acid varnish coating film from which the solvent has been removed is directly or through a peeling member. A heating roller was used to heat and pressurize the surface for smoothing, and then the smoothed coating film of polyamic acid varnish was heat-treated to imidize to form a polyimide resin coating layer. Further, after the polyamic acid varnish coating film from which the solvent has been removed is heat-treated to form a polyimide resin coating layer, the surface of this polyimide resin coating layer is polished or alkali-treated. [Effect] A resin-coated substrate having a uniform surface state and a uniform film thickness can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin-coated substrate used as a high resistance substrate of a thermal head or a circuit board for hybrid IC.

[0002]

2. Description of the Related Art In recent years, a polyimide resin has been used as an insulating layer on various substrates as a supporting substrate for various electronic components such as high resistance substrates for thermal heads and multilayer circuit substrates for hybrid ICs that require high reliability against heat. Resin-coated substrates coated as heat-resistant layers have been widely used.

For example, in the case of a thermal head, a high-resistivity substrate formed by using a conventional ceramic substrate with a glaze glass layer as a heat-retaining layer for controlling heat dissipation and heat storage is replaced with a polyimide resin layer on a ceramic substrate or a metal substrate. Attention has been paid to a heat-resistant insulating substrate formed as a layer (Japanese Unexamined Patent Publication No. 52-100245, Japanese Unexamined Patent Publication No. 56-164876, Japanese Unexamined Patent Publication No. 62-21431, and Japanese Unexamined Patent Publication No. 62-21432). Etc.).

In a thermal head using such a heat-resistant insulating substrate, a polyimide resin layer is formed as a heat retaining layer so that the polyimide resin has a thermal diffusivity of 1/3 to 1 / compared with a conventional glaze glass layer. Since it becomes as small as 6, the thermal efficiency is excellent. Further, when a flexible substrate such as a metal substrate is used, it is possible to perform a bending process, and a small-sized and inexpensive high-performance thermal head can be manufactured.

By the way, in the above thermal head, since it is necessary to form an inorganic thin film or a metal thin film for forming a heating resistor, an electrode, etc. on the polyimide resin layer as a heat retaining layer, defects such as voids and protrusions are formed. , And surface irregularities must be suppressed to a minimum. For example, if there are many defects such as voids and protrusions and surface irregularities in the polyimide resin layer, disconnection of resistors and electrodes, abnormal resistance values, and even damage due to overheating of the resistor during operation will improve reliability. It will be greatly reduced. Moreover, such a problem becomes more remarkable as the recording density of the thermal head becomes higher. Further, such a problem occurs not only in the thermal head but also in the hybrid IC circuit board and the like. In the case of a thermal head,
When the film thickness of the polyimide resin layer varies, there is a problem that the color density is sensitively affected as compared with the conventional glaze glass layer.

However, the heat insulating layer of the thermal head has a thickness of 10 to 50 μm, preferably 20 to 30 μm from the viewpoint of thermal efficiency.
Since a film thickness of about m 2 is required, it is difficult to solve the above problems with good reproducibility simply by forming a polyimide resin layer.

In a circuit board for a hybrid IC including a thermal head, the adhesion of the polyimide resin layer to the support substrate and the adhesion of the inorganic thin film or the metal thin film formed on the polyimide resin layer to the polyimide resin layer. Adhesion is an important factor in maintaining the reliability of electronic components that use it. Therefore, recently, when polyamic acid was synthesized, a part of the aromatic diamine, for example, 0.05 to 10 was used.
A siloxane-modified polyimide resin having an improved adhesive force is widely used by using a polyamic acid obtained by substituting a diamine having an Si group in a range of about mol% and performing a ring-opening polyaddition reaction.

However, the diamine-substituted siloxane bond portion having the Si group of the siloxane-modified polyimide resin is preferentially arranged at the interface with or on the surface of the supporting substrate to improve the adhesion to the supporting substrate and on the polyimide resin layer. Although it contributes to the improvement of adhesion with the formed inorganic thin film and metal thin film, on the other hand, the siloxane preferentially arranged on the surface causes thermal decomposition during the operation of the thermal head, causing problems such as swelling of the heat generating part. It has been pointed out that it causes the above phenomenon, and it is desired to appropriately remove this layer in consideration of the adhesion.

[0009]

As mentioned above, in recent years,
A resin obtained by coating a polyimide resin as an insulating layer or a heat-resistant layer on various substrates as a supporting substrate for various electronic components that require high reliability against heat, such as a high-resistance substrate of a thermal head or a multilayer circuit substrate for hybrid ICs. Coated substrates are becoming more popular.

However, for example, when a resin coated substrate coated with this polyimide resin layer as a heat retaining layer is used for a thermal head, if the polyimide resin layer has many defects such as voids and projections and surface irregularities, the polyimide resin The resistance and electrode formed on the layer are broken, the resistance value is abnormal, and the resistor is damaged due to overheating during operation. Moreover, such a problem becomes more remarkable as the recording density of the thermal head becomes higher. Further, such a problem occurs not only in the thermal head but also in the hybrid IC circuit board and the like. Further, in the case of the thermal head, if the thickness of the polyimide resin layer varies, there is a problem that the color density is sensitively affected as compared with the conventional glaze glass layer. However, the heat insulation layer of the thermal head is 10 to 50 μm, preferably 20 to 30 μm from the viewpoint of thermal efficiency.
Since a thickness of about m 3 is required, it is difficult to solve the above problems with good reproducibility simply by forming a polyimide resin layer.

In addition, in a thermal IC, a circuit board for hybrid IC, etc., the adhesion of the polyimide resin layer to the supporting substrate and the adhesion of the inorganic thin film or the metal thin film formed on this polyimide resin layer to the polyimide resin layer. Adhesion is an important factor for maintaining the reliability of electronic parts using the same, and therefore, recently, a part of aromatic diamine, for example, 0.05 to 1 was used during polyamic acid synthesis.
By using a polyamic acid obtained by substituting a diamine having an Si group in the range of about 0 mol% and subjecting it to a ring-opening polyaddition reaction, a siloxane-modified polyimide resin having an improved adhesive force is often used. But,
The diamine-substituted siloxane bond portion having the Si group of the siloxane-modified polyimide resin is preferentially arranged at the interface with or on the surface of the supporting substrate to improve the adhesion to the supporting substrate and to form an inorganic thin film formed on the polyimide resin layer. Although it contributes to the improvement of the adhesiveness with the metal thin film, on the other hand, the siloxane that is preferentially arranged on the surface causes thermal decomposition during the operation of the thermal head, causing problems such as swelling of the heat generating part. It is desirable to appropriately remove this layer in consideration of the property.

The present invention has been made in order to solve the above problems, and has a uniform film thickness on a supporting substrate such as a high resistance substrate of a thermal head or a multi-layer circuit substrate for a hybrid IC, and voids and protrusions. A first object of the present invention is to obtain a method for producing a resin-coated substrate capable of forming a smooth polyimide resin layer having few defects and surface irregularities with good reproducibility.

A second object of the present invention is to obtain a method for producing a resin-coated substrate capable of removing siloxane arranged on the surface of a polyimide resin layer formed on a supporting substrate with appropriate and reproducible properties.

[0014]

In a method for producing a resin-coated substrate in which a polyimide resin coating layer is coated on a supporting substrate,
A polyamic acid varnish is applied to the supporting substrate, and the solvent in the polyamic acid varnish coating film applied to the supporting substrate is heated at a temperature that does not imidize the polyamic acid constituting the polyamic acid varnish and then removed. The removed polyamic acid varnish coating film is smoothed by heating and pressing with a heating roller directly or through a peeling member, and then the smoothed polyamic acid varnish coating film is heat-treated to imidize the polyamic acid to form a polyimide resin. A coating layer was formed.

Further, a polyamic acid varnish is applied to the supporting substrate, and the solvent in the polyamic acid varnish coating film applied to the supporting substrate is removed by heating at a temperature that does not imidize the polyamic acid forming the polyamic acid varnish. ,
The polyamic acid varnish coating film from which the solvent had been removed was heat-treated to imidize the polyamic acid to form a polyimide resin coating layer, and then the surface of the polyimide resin coating layer was polished.

Further, a polyamic acid varnish is applied to the supporting substrate, and the solvent in the polyamic acid varnish coating film applied to the supporting substrate is removed by heating at a temperature at which the polyamic acid forming the polyamic acid varnish is not imidized. The polyamic acid varnish coating film from which the solvent had been removed was heat-treated to imidize the polyamic acid to form a polyimide resin coating layer, and then the surface of the polyimide resin coating layer was treated with alkali.

[0017]

As described above, when the polyamic acid varnish is applied to the supporting substrate, the solvent in the coating film is removed, and then the film is heated and pressed to be smoothed, the polyamic acid varnish coating film before imidization is compared. Since it is in a soft state and is smoothed in a state where the viscosity is reduced by heating, it is possible to easily eliminate the voids, surface protrusions and surface irregularities formed inside the coating film, resulting in a uniform and sound state. As the internal state and surface state, a desired polyimide resin coating layer can be obtained by the subsequent imidization.

Further, a polyamic acid varnish is applied to the supporting substrate, the solvent in the coating film is removed, and further heat treatment is performed to imidize the polyamic acid to form a polyimide resin coating layer, and then this polyimide resin coating layer is formed. Polishing the surface of the not only makes it possible to eliminate the protrusions and irregularities on the surface to obtain a uniform and sound surface state of the polyimide resin coating layer, but also to improve the uniformity of the film thickness, and to make the surface of the surface rough Then, it becomes possible to improve the adhesive force with the film formed on the polyimide resin coating layer.

Further, a polyamic acid varnish is applied to the supporting substrate, the solvent in the applied film is removed, and further heat treatment is performed to imidize the polyamic acid to form a polyimide resin coating layer. When the surface is treated with an alkali, particularly in the case of a siloxane-modified polyimide resin, the siloxane preferentially arranged on the surface can be removed with appropriate reproducibility and uniformly. Further, not only the siloxane-modified polyimide resin, but also the surface of the polyimide resin coating layer can be made to have an appropriate roughness to improve the adhesion to the film formed on this polyimide resin coating layer.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

Example 1 FIG. 1 is a flow chart showing a method for manufacturing a resin-coated substrate according to the first example.

First, the surface of the support substrate is activated (step (a)). For example, an example of a thermal head will be described. As a supporting substrate, a metal substrate made of Fe alloy containing Cr in an amount of 16 to 18% by weight and having a plate thickness of about 0.5 mm is used. The metal substrate was cut to size, deburred, and then the metal substrate was heated to 40 to 60 ° C. with diluted sulfuric acid (96% H ₂
The oxide layer on the surface of the metal substrate is removed by immersing it in SO ₄ 5 to 20% by volume) for about 1 to 2 minutes to activate the surface and form fine irregularities on the surface. When a ceramic substrate such as Al ₂ O ₃ or Al N is used as a supporting substrate, a film thickness of about 0.05 to 1 μm can be obtained by using a known thin film forming method such as sputtering or metallizing method on the ceramic substrate. An active metal layer made of Cr, Ti, Cr-Ti alloy or the like is formed.

Next, polyamic acid, which is a precursor of polyimide, was diluted with an organic solvent such as N-methyl-2pyrrolidone or N, N dimethylformamide on the activated surface of the supporting substrate or on the active metal layer. The polyamic acid varnish is applied by a method such as a roll coater or a spin-on coater ((b) step).

In this case, for example, the surface of the coating film of polyamic acid varnish formed by roll coating is
Irregularities corresponding to the grooves on the roll surface are formed, and the coating film of the polyamic acid varnish formed by spin-on coating has a thicker peripheral portion than the central portion.

The application of this polyamic acid varnish is controlled so that the film thickness of the polyimide resin layer is 15 μm or less, preferably 10 μm per time. When the thickness exceeds this value, the removal of the solvent thereafter becomes non-uniform, and the internal defects cannot be completely removed even when the smoothing treatment described later is performed.

The polyamic acid used is appropriately selected according to the purpose and application. For example, when the formed polyimide resin coating layer is used as a heat retaining layer for a thermal head, biphenyltetracarboxylic dianhydride and an aromatic diamine such as p-phenylenediamine, m-phenylenediamine, diaminodiphenylsulfone and diaminodiphenylmethane are used. A polyamic acid obtained by a cyclopolyaddition reaction is preferable. Particularly, when p-phenylenediamine is used, a polyimide resin coating layer having a high thermal decomposition temperature and a small thermal expansion coefficient can be formed.

Further, a polyamic acid obtained by substituting a part of the aromatic diamine with a diamine having a Si group in the range of, for example, about 0.05 to 10 mol% during the synthesis of the polyamic acid and carrying out a ring-opening polyaddition reaction. Is used, a siloxane-modified polyimide resin capable of improving the adhesive force is obtained.

Then, the supporting substrate on which the coating film of the polyamic acid varnish is formed is put in, for example, a drying oven, and 6
The solvent in the coating film is removed by heating at a temperature of 0 to 120 ° C. at which imidization does not occur (step (c)).

Since the removal of the solvent occurs rapidly in the initial stage of heating and thereafter decreases only to a certain value determined by the temperature, it is preferable to dry the solvent for an appropriate time period corresponding to the set temperature, for example, 60 ° C. × 60 minutes. 90 after drying
Dry on a schedule such as drying at 30 ° C. for 30 minutes.

In this case, the removal amount of the solvent is 6 of the added solvent.
It is 0%, preferably 80% or more. The amount of solvent removed is 6
If it is less than 0%, a foaming phenomenon will occur at the time of smoothing, which will be described later, which will cause generation of voids in the polyimide resin layer.

Further, this solvent removal treatment is preferably carried out in an atmosphere of an inert gas such as nitrogen gas, which prevents the generation of an oxidizing gas when removing the solvent and attaches it to the supporting substrate during imidization. The force of attachment can be increased.

Next, a polyamic acid varnish of the same type or a different type as the polyamic acid varnish used in the step (b) is applied again to the coating film of the polyamic acid varnish from which the solvent has been removed (step (d)).

The application of the second layer of polyamic acid varnish is carried out after the temperature of the supporting substrate heated in the above step (c) reaches room temperature. In this case, if the polyamic acid varnish is applied while the temperature of the supporting substrate is high, the reaction rapidly proceeds and defects are likely to occur. The film thickness and the like are the same as those in the above step (c).

Then, under the same conditions as in the above step (c), 2 of the polyamic acid varnish obtained in the step (d) is obtained.
The solvent in the layer coating film is removed by heating ((e) step).

In this case, the removal amount of the solvent is also 6
It is 0%, preferably 80% or more.

Generally, by applying this second layer of polyamic acid varnish, a polyimide resin layer having a substantially desired film thickness can be obtained. However, when the film thickness is further increased,
The coating and drying of the above polyamic acid varnish are repeated to obtain a desired film thickness.

Next, the two-layer coating film of the polyamic acid varnish from which the above solvent has been removed is subjected to a smoothing treatment ((f) step).

This smoothing process is performed by the device shown in FIG. This apparatus comprises a conveyor 3 for horizontally conveying the support substrate 2 having the polyamic acid varnish two-layer coating film 1 formed thereon, a pair of upper and lower heating rollers 4 arranged in the middle of the conveyor 3, and a heating roller The heating device 5 for preheating the two-layer coating film 1 of the polyamic acid varnish formed on the supporting substrate 2 before reaching the roller 4 and the two-layer coating film 1 of the polyamic acid varnish after passing the heating roller 4 are formed. When the two-layer coating film 1 is smoothed by the cooling fan 6 for cooling the support base 2 and the pair of heating rollers 4,
The polyamic acid varnish two-layer coating film 1 is composed of a release sheet supply / winding mechanism 8 for supplying a release sheet 7 between the heating roller 4 and one of the heating rollers 4 pressed against the coating film 1. The release sheet 7 is for preventing the surface state of the heating roller 4 from being transferred to the polyamic acid varnish two-layer coating film 1 as much as possible, and has a thickness of 10 to 50 μm, preferably about 25 μm PET (polyethylene). A terephthalate resin) film or the like is used, and a silicon-based release agent is applied to the contact surface with the polyamic acid varnish two-layer coating film 1 in order to improve peeling.

In the smoothing treatment, first, the polyamic acid varnish two-layer coating film 1 formed on the supporting substrate 2 by the heating device 5 is used.
Is pre-heated, and then the supporting substrate 2 on which the polyamic acid varnish two-layer coating film 1 is formed is conveyed to the heating roller 4 by the conveyor 3. Then, the release sheet 7 is supplied from the release sheet supply / winding mechanism 8 and heated and pressed by the pair of heating rollers 4 through the release sheet 7.
The polyamic acid varnish two-layer coating film 1 is smoothed. After passing through the heating roller 4, the release sheet 7 is cooled by the cooling fan 6 and then adhered to the polyamic acid varnish two-layer coating film 1 smoothed by heating and pressurizing the heating roller 4.
Is peeled off and is wound up on the release sheet feeding and winding mechanism 8.

The temperature of the heating roller 4 during the smoothing process,
The pressure, the gap between the heating rollers 4, and the feed rate (conveyance rate) need to be selected as appropriate values according to the components and the film thickness of the polyamic acid varnish two-layer coating film 1. Regarding the polyamic acid varnish two-layer coating film 1 of this example, the temperature of the heating roller 4 is set to 60 to 120 ° C., the pressure, the gap between the heating rollers 4 and the feed rate are set to 2 respectively.
-5 kg / cm, 3-0.45 mm, 3-15 mm / sec.
In particular, the temperature of the heating roller 4 at the time of the smoothing treatment is set to the maximum heating when removing the solvent of the coating film of the polyamic acid varnish in order to avoid inclusion of bubbles due to rapid evaporation of the residual solvent in the coating film. It is desired to lower the temperature by about 10 ° C.

In this example, the heating roller 4 is made of heat resistant silicone rubber and has a surface roughness Ra of 0.1 μm.
Hereinafter, the one having a hardness of 50 degrees was used. This heating roller 4
The surface hardness depends on the hardness of the coating film of the polyamic acid varnish, but is preferably 40 degrees or more and 90 degrees or less. When the hardness is lower than 40 degrees, it becomes difficult to smooth the projections and surface irregularities, and it becomes difficult to set the surface roughness Ra to 0.1 μm or less. If the hardness is higher than 90 degrees, the ceramic support substrate 2 may be damaged.

Next, the smoothed polyamic acid varnish two-layer coating film is heat-treated at a temperature at which imidization proceeds, for example, at a temperature of about 120 to 480 ° C. to promote a dehydration cyclization reaction of the polyamic acid. It is imidized to form a polyimide resin coating layer ((g) step).

In this heat treatment for imidization, the solvent has already been removed, but it is preferable to gradually expose it to high temperature, for example, 130 ° C. × 30 minutes → 250 ° C. × 60 minutes → 4.
It is preferable to increase the temperature sequentially at 50 ° C. for 60 minutes. The heat treatment for imidization is preferably performed in an atmosphere of an inert gas such as nitrogen gas.

Next, a specific example of the method for manufacturing the polyimide resin coating layer substrate according to this embodiment will be described. The processing conditions in each step are as follows.

Step (a): Treatment liquid concentration = 10% by volume, temperature = 50 ° C., treatment time = 60 seconds Step (b): coating method = roll coater, coating film thickness = 1
0 μm (converted to polyimide resin coating layer) Step (c): Heating condition = 60 ° C. × 60 minutes → 100 ° C. × 3
0 minutes (in nitrogen gas) Step (d): coating method = roll coater, coating thickness = 1
0 μm (converted to polyimide resin coating layer) Step (e): Heating condition = 60 ° C. × 60 minutes → 100 ° C. × 3
0 minutes (in nitrogen gas) Step (f): Heating temperature = 90 ° C., pressure = 3 kg / cm, feed rate = 5 mm / sec Step (g): Heating condition = 130 ° C. × 30 minutes → 250 ° C. ×
60 minutes → 450 ° C. × 60 minutes In Table 1, the internal defects, surface roughness (waviness and surface roughness Ra), and adhesive force of the polyimide resin coating layer formed under the above respective process treatment conditions are shown in Table 1 below. It is shown in comparison with the polyimide resin coating layer (comparative example) formed in the same process except that the smoothing treatment is not performed.

[0046]

[Table 1]

The internal defects shown in Table 1 were observed with an Olympus ultrasonic microscope, and the waviness was measured with a Tokyo Seimitsu surface profiler (WAC 0.8 to 8 mm cycle). Is the result of measurement by a three-dimensional roughness meter manufactured by Kosaka Seisakusho, and the adhesive force is the result of measuring the number of peeled pieces by dipping in boiling water for 3 hours and then by a cross-cut test according to JIS-5400.

As is clear from Table 1, the resin-coated substrate obtained by the manufacturing method of this embodiment has no voids inside the resin-coated layer, surface protrusions, and surface irregularities, and has a uniform and sound internal state. A surface condition is obtained and the film thickness is uniform. Even at the interface between the supporting substrate and the polyamic acid varnish coating film, the polyamic acid varnish coating film completely enters the gaps of the fine unevenness of the supporting substrate, and the strong adhesion of the polyimide resin coating layer to the supporting substrate is stably obtained. Is shown.

A thermal head using a resin-coated metal substrate is manufactured by the following method.

A polyimide resin coating layer as a heat retaining layer is formed on the metal substrate by the above manufacturing method, and p-CVD (Plasma-Chemical Vapor Depo) is formed on the polyimide resin coating layer.
by known thin film forming method such as Sition) or sputtering, sequentially _{Si O x, SiC x, Si} -Zr -Y-O
-N, etc. base film, and Ta-SiO ₂ , Nb
-A heating resistance film made of SiO ₂ or the like is formed. Further, a conductor film such as Al or Al alloy to be an individual electrode and a common electrode is formed thereon by the same method. Then, the heat generating resistor film and the conductor film are patterned by a photolithography method to form a large number of heat generating resistors, individual electrodes and common electrodes having predetermined intervals and shapes. After that, by a sputtering method or the like so as to cover at least the heat generating portion, Si-Zr-Y-O-N or Si-
A thermal head is obtained by forming an anti-oxidation film and a wear resistant film made of ON or the like.

In the thermal head thus obtained, the polyimide resin coating layer formed as a heat retaining layer on the metal substrate does not have internal voids, surface protrusions or surface irregularities as described above, and has a uniform film thickness. Also, even at the interface with the metal substrate, the polyamic acid varnish coating film completely fills the gaps of the fine irregularities of the supporting substrate, and the adhesive force to the supporting substrate is excellent, so that it is highly reliable and long-lasting. A stable printing operation can be obtained over time.

Further, the resin-coated substrate obtained according to the manufacturing method of this embodiment is not limited to a thermal head, but can be used for other purposes such as an insulating substrate for hybrid IC, and great effects can be obtained.

In the above example, when the coating film of polyamic acid varnish was smoothed, the release sheet was interposed between the coating film of polyamic acid varnish and the heating roller for smoothing the coating film. The smoothing of the coating film of this polyamic acid varnish is performed by directly heating and applying the heating roller without using a release sheet by forming the heating roller with a material excellent in releasing or by applying a releasing agent on the surface of the heating roller. It is also possible to press and smooth.

Example 2 FIG. 3 is a flow chart showing a method of manufacturing a resin-coated substrate which is a second example.

In this Example 2, as in Example 1, the activation treatment of the surface of the supporting substrate ((a) step) → the application of polyamic acid varnish ((b) step) → the solvent in the polyamic acid varnish coating film Removal ((c) step) → reapplication of polyamic acid varnish ((d) step) → removal of the solvent in the two-layer coating film of polyamic acid varnish ((e) step), and then the polyamic acid varnish The two-layer coating film of varnish is subjected to imidization of polyamic acid by a dehydration cyclization reaction in the same manner as in step (g) of Example 1 (step (f)). Further in this Example 2, after that, a wrapping film or a particle size of 0.06 to 1 μm, preferably 0.0
The surface is polished with an abrasive in which fine particles of alumina or the like of about 6 to 0.03 μm are dispersed in water ((g))
Process).

Next, a specific example of the polyimide resin coating layer according to this embodiment will be shown. The processing conditions in each step are
It is as follows.

Step (a): Treatment liquid concentration = 10% by volume, temperature = 50 ° C., treatment time = 60 seconds Step (b): coating method = roll coater, coating film thickness = 1
0 μm (converted to polyimide resin coating layer) Step (c): Heating condition = 60 ° C. × 60 minutes → 100 ° C. × 3
0 minutes (in nitrogen gas) Step (d): coating method = roll coater, coating thickness = 1
0 μm (converted to polyimide resin coating layer) Step (e): Heating condition = 60 ° C. × 60 minutes → 100 ° C. × 3
0 minutes (in nitrogen gas) Step (f): Heating condition = 130 ° C. × 30 minutes → 250 ° C. ×
60 minutes → 450 ° C. × 60 minutes Step (g): Abrasive particles = alumina, particle size = 0.08 μm The surface roughness (waviness and surface roughness Ra) of the polyimide resin coating layer formed in Table 2 under the above-mentioned processing conditions. To
It is shown in comparison with a polyimide resin coating layer (comparative example) formed in the same step except that polishing in the step (g) is performed.

[0058]

[Table 2]

The waviness in Table 2 was measured by a surface shape measuring instrument manufactured by Tokyo Seimitsu Co., Ltd. as in Table 1 (WAC 0.8 to 8 mm).
As a result, the surface roughness Ra is a result measured by a three-dimensional roughness meter manufactured by Kosaka Seisakusho.

As is clear from Table 2, the resin-coated substrate obtained by the manufacturing method of this example has a sound surface condition with uniform and fine irregularities without surface protrusions or abnormal irregularities on the surface. And the film thickness is uniform.

Further, in the production method of Example 2, a polyimide resin such as a polyamic acid obtained by ring-opening polyaddition reaction by substituting a diamine having a Si group for a part of an aromatic diamine during synthesis of a polyamic acid is used. For those in which a siloxane derived from a diamine having an Si group is formed on the surface of the coating layer, the removal of the siloxane that enhances the adhesion of the film to the polyimide resin coating layer reduces the adhesion of the film, Proper removal by polishing in the process (g) and fine irregularities on the surface work together and do not reduce the adhesive force of the film formed on it, which has been conventionally caused by the siloxane on the surface. It is possible to effectively prevent the generated heat-generating portion of the thermal head from being swollen.

Example 3 FIG. 4 is a flow chart showing a method of manufacturing a resin-coated substrate which is a third example.

In Example 3, as in Example 1, the activation treatment of the surface of the supporting substrate ((a) step) → the application of polyamic acid varnish ((b) step) → the solvent in the polyamic acid varnish coating film Removal ((c) step)-> Reapplication of polyamic acid varnish ((d) step)-> Removal of solvent in the two-layer coating film of polyamic acid varnish ((e) step)-> Two-layer coating film of polyamic acid varnish Smoothing process ((f) step)
→ After the imidization of the polyamic acid ((g) step) is sequentially performed, the surface of the polyimide resin coating layer is polished in the same manner as the (g) step of Example 2 ((g) step).

When the solvent in the two-layer coating film of polyamic acid varnish is removed and then the smoothing treatment is performed, fine bubbles inside the two-layer coating film of polyamic acid varnish can be removed, and the projections and the surface can be removed. It is possible to form a polyimide resin coating layer having no unevenness on the surface and smoothing, and finally eliminating internal voids, protrusions on the surface and unevenness on the surface and having a uniform film thickness. Further, the adhesion of the polyimide resin coating layer to the supporting substrate can be increased. Further, by polishing after imidizing the polyamic acid, the smoothed surface can be made into a sound surface state having uniform fine irregularities. In addition, especially when polyamic acid is synthesized, a portion of the aromatic diamine is replaced with a diamine having a Si group to form a polyamic acid obtained by a ring-opening polyaddition reaction.
For those in which a siloxane derived from a diamine having a group is formed, the siloxane can be appropriately removed. When smoothing a two-layer coating film of polyamic acid varnish,
If the silicone-based release agent adheres and remains after being converted to the polyimide resin coating layer, it reduces the adhesive force of the film formed on the polyimide resin coating layer, but effectively removes them by polishing. As a result, it is possible to prevent a decrease in the adhesive force of a film or the like formed on the polyimide resin coating layer.

Fourth Embodiment FIG. 5 is a flow chart showing a method for manufacturing a resin-coated substrate according to a fourth embodiment.

In Example 4, as in Example 2, activation treatment of the surface of the supporting substrate ((a) step) → application of polyamic acid varnish ((b) step) → solvent in polyamic acid varnish coating film Removal ((c) step) → re-application of polyamic acid varnish ((d) step) → removal of solvent in the two-layer coating film of polyamic acid varnish ((v) step) → imidization of polyamic acid ((f ) Step), the supporting substrate on which the polyimide resin coating layer is formed is heated to 40 to 70 ° C. with an aqueous solution containing 3 to 10% by weight of sodium hydroxide to obtain a solution in the sodium hydroxide solution. Immerse in a few minutes for alkali treatment.

When the support substrate having the polyimide resin coating layer thus formed is treated with an alkaline aqueous solution, not only can siloxane preferentially arranged on the surface of the polyimide resin coating layer be appropriately removed, but also the polyimide resin coating layer The surface can be roughened to form a uniform fine uneven surface.

As an example, a thermal head formed in the same manner as the thermal head described in Example 1 using the resin-coated metal substrate manufactured by this method will be described. The applied energy is 10 ⁸ with a pulse period of 10 ms and a pulse width of 2 ms.
As a result of applying the voltage twice and forcing the test (life test), the heat generation part swelled in the thermal head using the resin-coated metal substrate manufactured in the same process except that the alkali treatment in the process (g) was not performed. , The resin-coated metal substrate of this example is
No abnormalities were shown. In addition, the moderate removal of siloxane that enhances the adhesive force of the film formed on the polyimide resin coating layer, combined with the uniform fine irregularities on the surface, prevents the decrease of the adhesive force, resulting in high reliability and high reliability. The thermal head did not swell due to decomposition of siloxane during use, and a thermal head capable of performing stable printing operation for a long time could be obtained.

Example 5: FIG. 6 is a flow chart showing a method of manufacturing a resin-coated substrate according to a fifth example.

In Example 5, as in Example 3, activation treatment of the surface of the supporting substrate ((a) step) → application of polyamic acid varnish ((b) step) → solvent in the polyamic acid varnish coating film Removal ((c) step)-> Reapplication of polyamic acid varnish ((d) step)-> Removal of solvent in the two-layer coating film of polyamic acid varnish ((e) step)-> Two-layer coating film of polyamic acid varnish Smoothing process ((f) step) →
After the imidization of the polyamic acid ((to) step) is sequentially performed, the polyimide resin coating layer is subjected to alkali treatment in the same manner as in Example 4 (to) step.

As described above, when the solvent in the two-layer coating film of polyamic acid varnish is removed and the smoothing treatment is performed,
It is possible to remove fine air bubbles inside the two-layer coating film of polyamic acid varnish, and to eliminate surface protrusions and surface irregularities, and finally to obtain smooth and free film with no internal voids, surface protrusions or surface irregularities. It is possible to form a uniform polyimide resin coating layer. Further, the adhesion of the polyimide resin coating layer to the supporting substrate can be increased. Further, by imidizing the polyamic acid and then polishing, it is possible to obtain a sound surface state having uniform fine irregularities. Moreover, a part of the aromatic diamine is mixed with Si during the polyamic acid synthesis.
For a polyamic acid obtained by substituting a diamine having a group with a ring-opening polyaddition reaction, a dioxane derived from a diamine having a Si group is preferentially formed on the surface of a polyimide resin coating layer, this siloxane is used. It can be removed appropriately, and it is possible to prevent swelling of the heat generating portion of the thermal head that has been conventionally caused by the decomposition of the siloxane. In addition, when a two-layer coating film of polyamic acid varnish is smoothed, a silicon-based releasing agent adheres and remains after being converted to a polyimide resin coating layer, resulting in a film formed on the polyimide resin coating layer. Although the adhesive force is reduced, it can be effectively removed by the above-mentioned polishing to prevent the adhesive force of the film formed on the polyimide resin coating layer from being lowered.

Although each of the above-mentioned embodiments has been described mainly about the resin-coated substrate used for the thermal head, the resin-coated substrate of the present invention can be used for various applications such as an insulating substrate for hybrid IC.

[0073]

EFFECT OF THE INVENTION A polyamic acid varnish is applied to a supporting substrate, and the solvent in the coating film of the polyamic acid varnish applied to the supporting substrate is removed by heating at a temperature that does not imidize the polyamic acid forming the polyamic acid varnish. After that, the coating film of the polyamic acid varnish from which the solvent has been removed is heated or pressed by a heating roller directly or through a peeling member to be smoothed, and then the smoothed coating film of the polyamic acid varnish is heat-treated. When a resin-coated substrate is manufactured by imidizing a polyamic acid to form a polyimide resin coating layer, the polyamic acid is smoothed in a relatively flexible state before imidization, and the viscosity is lowered by heating. Therefore, it is possible to easily eliminate the voids, surface protrusions, and surface irregularities formed inside the coating film. No uniform and sound internal state and surface state, and it is possible to form a uniform polyimide coating layer thickness. Moreover, by the smoothing treatment, the coating film of the polyamic acid varnish can be completely inserted into the gaps of the fine irregularities on the surface of the supporting substrate, and the polyimide resin coating layer having a large adhesive force to the supporting substrate can be formed.

Further, after coating the supporting substrate with a polyamic acid varnish, removing the solvent in the coating film, and further heat treating to imidize the polyamic acid to form a polyimide resin coating layer, the polyimide resin coating layer is formed. When a resin-coated substrate is manufactured by polishing the surface of, not only can the projections and irregularities on the surface be eliminated and a uniform and sound surface state of the polyimide resin coating layer can be obtained, but also the uniformity of the film thickness can be improved. In addition, the surface can be made to have an appropriate roughness to improve the adhesion to the film formed on the polyimide resin coating layer.

Further, a polyamic acid varnish is applied to the supporting substrate, the solvent in the applied film is removed, and further heat treatment is performed to imidize the polyamic acid to form a polyimide resin coating layer, and then this polyimide resin coating layer is formed. When a resin-coated substrate is manufactured by subjecting the surface of the resin to an alkali treatment, the siloxane preferentially arranged on the surface can be removed with reasonable reproducibility and uniformly, and the surface can be made to have an appropriate roughness to form a polyimide resin coating layer. It is possible to improve the adhesive force with the film formed above.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method of manufacturing a resin-coated substrate according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a smoothing process in the first embodiment.

FIG. 3 is a flowchart showing a method of manufacturing a resin-coated substrate according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a method for manufacturing a resin-coated substrate according to a third embodiment of the present invention.

FIG. 5 is a flowchart showing a method of manufacturing a resin-coated substrate according to a fourth embodiment of the present invention.

FIG. 6 is a flowchart showing a method of manufacturing a resin-coated substrate according to a fifth embodiment of the present invention.

[Explanation of symbols]

1. Two-layer coating film of polyamic acid varnish 2 ... Support substrate 4 ... Heating roller 7 ... Release sheet 8 ... Release sheet supply / winding mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/44 A 8727-4E // B32B 31/26 7141-4F

Claims (3)

[Claims] 1. A step of applying a polyamic acid varnish to a supporting substrate, and a solvent in a polyamic acid varnish coating film applied to the supporting substrate by heating at a temperature that does not imidize the polyamic acid constituting the polyamic acid varnish. A step of removing the solvent, a step of heating and pressing the solvent-removed polyamic acid varnish coating film directly or through a peeling member with a heating roller to smooth the coating film of the smoothed polyamic acid varnish. And a step of forming a polyimide resin coating layer by heat treatment to imidize the polyamic acid to form a polyimide resin coating layer. 2. A step of applying a polyamic acid varnish to a supporting substrate, and a solvent in a polyamic acid varnish coating film applied to the supporting substrate by heating at a temperature at which the polyamic acid constituting the polyamic acid varnish is not imidized. And a step of heat-treating the polyamic acid varnish coating film from which the solvent has been removed, a step of forming a polyimide resin coating layer by imidizing the polyamic acid, and a step of polishing the surface of the polyimide resin coating layer. A method for producing a resin-coated substrate, comprising: 3. A step of applying a polyamic acid varnish to a supporting substrate, and a solvent in a polyamic acid varnish coating film applied to the supporting substrate by heating at a temperature at which the polyamic acid constituting the polyamic acid varnish is not imidized. And a step of heat-treating the solvent-removed polyamic acid varnish coating film to form a polyimide resin coating layer by imidizing the polyamic acid and a step of subjecting the surface of the polyimide resin coating layer to an alkali treatment. A method for producing a resin-coated substrate, comprising: