JPH022893A - Production of resin coated substrate - Google Patents

Abstract

PURPOSE:To form a coating film having high quality in spite of the large thickness on a substrate by coating the substrate with a thick film of resin varnish having high heat resistance by means of a rotating roll having grooves, spinning the substrate to smoothen the coated surface and baking the substrate. CONSTITUTION:A substrate 17 is coated with a thick film of resin varnish having high heat resistance by means of a rotating roll 13 having grooves. The coated surface is smoothened by spinning the substrate 17 by means of a conventional spin coater and then the substrate 17 is baked. A coating film free from streaks and having high quality in spite of the large thickness is formed on the substrate with no waste of the liq. resin and a resin coated substrate can be obtd.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method of coating a thick film of liquid resin on the surface of a resin-coated substrate, such as a thermal head substrate or a hybrid IC substrate. .

(Prior Art) Generally, as shown in FIG. 4, a thermal head includes a substrate (20), a heat-resistant resin layer (21) formed on the substrate (20), and a heat-resistant resin layer (21) formed on the substrate (20). A large number of heating resistors (22) formed above and these heating resistors (22)
) and a conductor (23) connected to the conductor (23).

Incidentally, a roll coater or a spin coater is generally used to coat a substrate with a highly heat-resistant resin (liquid resin).

Fig. 5 schematically shows an example of this roll coater. First, the pressurized liquid resin is sent to the liquid resin pump (1) and passes through the filter (2), which is installed on the side of the doctor (2). It is sent into the doctor (3) through the slit or pore. Then, the liquid resin is supplied to the surface of the rotating roll 0) by this doctor (2) that comes into contact with the rotating roll 0). The doctor (2) also works to level the liquid resin supplied to the one-rotation roll (A).

The rotating roll Ω) of this roll coater shown in FIG. 0 is formed.

In the conventional roll coating method, as shown in FIG. , for example, several to several dozen lines.This streak (2) is generated from the edge (5A) of the board (2), and has a shape such that the surface of the board (0) is exposed. It is a side view seen from the end (5A) direction of the substrate ■, and shows the resin film (
This is an enlarged view of the streaks ■ that occurred in ( ).

By the way, FIG. 7 is a diagram schematically explaining the mechanism by which the streaks (2) occur. The rotating roll 0) has a valley depth of, for example, 0.5 mm and a pitch interval of, for example, 0.7.
A pitch of +nm is carved around the roll. Here, if the liquid resin (R) is attached to, for example, the valley (4a) of the rotating roll 0) from the starting end where the resin film 0 begins to be formed, that is, the end (5Δ) of the substrate 0, the substrate Since the liquid resin is pulled by the surface tension on the valley (4a) side compared to the side, the liquid resin does not adhere to the substrate (2), and the above-mentioned streaks (2) occur. This streak (■) is related to the viscosity and thickness of the coating film, and the surface tension of the coating film, and is also a function of time. Therefore, if the viscosity is low, the film thickness is thin, and it is a Newtonian liquid,
The coating film is smoothed, ie, leveled, and streaks disappear.

However, a thick coating film using a liquid resin with high viscosity exhibits pseudoplastic flow, and requires a lot of time for leveling, and the leveling stops at a certain point.

On the other hand, in the spin coating method, the liquid resin to be applied is dropped onto the center of a rotating substrate, and the centrifugal force acting on the substrate spreads the liquid resin toward the periphery of the substrate, thereby coating the entire surface of the substrate. form.

The above-mentioned coating method is carried out using a rotary coating device as shown in FIG. In FIG. 2, ``■'' is a rotating support equipped with a vacuum chuck, ``■'' is a liquid resin dripping nozzle, and (10) is an outlet for excess material.

When performing one-turn coating with such an apparatus, the substrate (17) on which the coating film is to be formed is mounted on the rotating support (2), and the rotating support (2) is rotated. And drip nozzle 0
Then, drop the liquid resin onto the center of the substrate. In this case 1
The liquid resin that was dropped.

It is expanded from the top of the substrate (17) toward the periphery due to centrifugal force,
A coating film is formed on the entire surface of the substrate.

(Problems to be Solved by the Invention) As described above, in the conventional roll coating method, when a high viscosity liquid resin is used, a uniform coating film is not formed on the substrate, and multiple streaks occur. It has the disadvantage of being Further, the amount of liquid resin dropped here is influenced by the shape of the grooves on the coating roll, the pressure of the doctor, and the distance between the backup roll and the coating roll. Furthermore, the dropped liquid resin is then
A curing process is performed, and the film thickness after curing is determined by the viscosity and solid content at the time of coating. Therefore, if the viscosity is high and the solid content is high, the coating film can be made thick. However, as mentioned above, since streaks occur, in order to obtain a thick film, it is necessary to use a liquid resin with low viscosity and solid content and repeat the roll coating process and the curing process.

In particular, in the case of strip-shaped substrates such as insulating substrates for thermal heads, most of the liquid resin is discarded by centrifugal force.
Unfavorable from an economic point of view. Furthermore, coating with highly viscous liquid resin is difficult.

Productivity is also bad. Therefore, the present invention solves such problems and prevents the occurrence of streaks in thick coating films.

It is an object of the present invention to provide a method for manufacturing a resin-coated substrate that enables smoothing of the surface of the coating film.

[Structure of the invention]

(Means for Solving the Problems) The method for manufacturing a resin-coated substrate of the present invention includes the steps of roll-coating a thick film of high heat-resistant resin varnish on a substrate using a rotating roll having grooves, and rotating the substrate. The method is characterized by comprising the steps of smoothing the coating surface and firing the substrate. Further, between the roll coating step and the smoothing step, a step of heating and curing the high heat resistant resin at 40° C. to 200° C. is performed.

(Function) A thick film coated on a substrate has streaks formed on its surface during roll coating, but by rotating the substrate afterwards.

The surface is smoothed by centrifugal force.

Particularly when forming a coating film with a thickness of 15 tlra or more, peeling of the coating film can be prevented by performing a heat curing step.

The temperature in this heat curing step is preferably 50°C.
~150°C, which is a low temperature at which no chemical reaction of the varnish occurs, that is, a temperature at which the solvent evaporates and the surface solidifies.

(Example) An example of the coating method of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view for explaining the coating method of the present invention, and the rotary roll (13) rotating in the direction of arrow (C') is equipped with a doctor roll (13), for example, with regard to the generation of dust. (14) is preferred, and using this, liquid resin is supplied from the nozzle (15) to the roll surface. The liquid resin had a solid content of 18% and a viscosity of 50 poise, and was a highly heat-resistant polyimide resin varnish. Moreover, the shape of the rotating roll (13) is an inverted trapezoid, and the upper side is 1.0
mm, bottom side 0.2m, height 0.6m, groove spacing 1. It is On*. According to these conditions, arrow (C)
By moving the substrate (17) in the direction of arrow (D) by the substrate transport roller (16) rotating in the direction of arrow (C), the substrate (17) is moved in the direction of arrow (D).
The substrate (
17) The liquid resin is shaped.

However, streaks (18) occur on this coating surface.

Next, this coated substrate is applied using a conventional spin coating apparatus as shown in FIG. The substrate (17) is held on a rotating support (8) with a small number of screws in order to smooth the coating surface, and is rotated at a low speed of 500 rpm.
for 20 seconds, followed by 30 seconds at a rotation speed of 1100 Orp. Furthermore, as shown in Figure 3, the substrate can be arranged so that the centrifugal force E acts perpendicularly to the streaks (18).This eliminates the streaks and at the same time A coating film with a uniform thickness and a smooth film surface was obtained.

Next, the substrate (17) is subjected to a firing process to evaporate the solvent and perform an imidization reaction, although this varies depending on the material, to form a resin-coated substrate.

Next, a manufacturing method in case the thickness of the high heat resistant resin coating layer is 15 mm or more will be explained.

Initially, liquid resin is formed on the substrate (17) by the rotating roll (13) as described above. Next, in order to evaporate the solvent contained in the resin varnish, the resin varnish is placed in a drying oven for 1 hour in a nitrogen atmosphere at 50° C. to be heated and cured. and,
A liquid resin prepared by diluting varnish and solvent at a volume ratio of 1:1 is used, and a conventional spin coating apparatus shown in FIG. 2 is used. The implementation conditions were the same as in the method described above. As a result, a coating film was obtained in which streaks were eliminated, the film thickness was made uniform, and the film surface was smoothed.

Next, the substrate (17) is subjected to a firing process to evaporate the solvent and perform an imidization reaction, although this differs depending on the material, to form a resin substrate.

In this way, when going through the heat curing process, 15μ
It is suitable for forming a coating film of s, and can prevent peeling of the coating film between layers. Furthermore, since it is cured to a certain degree, handling becomes easier.

In this example, a polyimide resin varnish was used as a highly heat-resistant resin varnish, but the polyimide resin varnish may be an uncyclized type of aromatic polyimide having a biphenyl structure or a polyimide having a biphenyl structure with Si groups in its skeleton. An uncyclized polyimide resin or a cyclized polyimide resin may be used.

Furthermore, a polyamide amide resin can also be used as the high heat resistant resin varnish.The solid content of the high heat resistant resin varnish used in the present invention is 10% to 25%.

Preferably 18% or more and a viscosity range of 30 poise to
As long as the thickness is 120 poise, preferably 50 poise to 90 poise, it is possible to smooth even a film having a thickness of 10 or more using the manufacturing method of the present invention without being limited to the above-mentioned materials.

Further, the groove shape of the roll (13) in FIG. 7 may be a figure 7 shape in addition to the inverted trapezoid shown in this embodiment.

The dimensions of the inverted trapezoid are 0.8 m to 1.5 m on the upper side and 0.0 m on the lower side.
, 1 mm ~ 0.3 mm, height 0.4 m
m ” 0, 8 m, groove spacing is 0.8111 m to 1.
5 mm is preferred. On the other hand, if it is a figure 7 shape, the depth of the valley is 0,3 rm to 0,7 m, and the groove spacing is 0,5
Dimensions from tm to 1,0 mm are preferred.

The surface smoothing conditions for the spin coating device shown in Fig. 2 include a low rotation speed of 40 Orpm to 600 rpm and a
0 seconds to 60 seconds, high speed rotation speed 90Orpm to 1500
20 seconds to 60 seconds at rpm is preferred.

In addition, the dilution ratio of the varnish and the solvent should be from the varnish stock solution itself to 1=1O, more preferably 1:1. To use the varnish stock solution, the high speed rotation speed should be 200° rpm to 3000 rpm.
It is necessary to set it to rp+m. Of course, if a stock solution is used, the film thickness will be 1.1 to 1.5 times the conventional film thickness, so it is necessary to control the film thickness on the roll coater side in advance.

When the substrate obtained according to the present invention is used as a substrate for a thermal head, it serves as an electrical insulating layer and a heat storage layer. For this purpose, the high heat-resistant resin coating layer needs to have a thickness of at least 10 μm, and as a heat storage layer,
If the thickness is not 15 μs or more, the effect will be small.

In addition, in order to obtain the same coating layer only by the spin cord method, it must be performed at high speed rotation with a viscosity of 50 voise or less, and it is necessary to repeat coating and curing treatment to obtain the same thickness, which is not preferable.

Furthermore, when increasing the thickness of the coating film, 1) repeat the manufacturing method of the present invention, or repeat coating from a semi-baked state using the roll coating method, and then perform spin code at the top layer thickness. You may do so. Thereby, the quality of the outermost surface can be kept good.

〔Effect of the invention〕

As is clear from the above description, according to the invention of claim 1, a substrate can be obtained on which a good coating film is formed even in thickness 2, without waste of liquid resin and without generation of streaks.

Moreover, according to the invention of claim 2, the above effects can be obtained and even a coating film with a thickness of 15 um or more can be reliably formed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view for explaining a roll coating method according to an embodiment of the present invention, FIG. 2 is a vertical sectional view showing a spin coating apparatus according to the present invention, and FIG. Figure 4 is a front view showing the method of arranging the substrates, Figure 4 is a perspective view of the main parts showing the thermal head, Figure 5 is a schematic diagram for explaining the conventional coating method, Figure 6 is the conventional roll coating method. FIG. 7 is a side view showing an enlarged view of the streaks generated when liquid resin is coated on the substrate, and FIG. 7 is a schematic diagram for explaining the reason why the streaks shown in FIG. 6 occur. (13)...Rotating roll (17), (20)...Substrate s/4- Fig. 1 Fig. 2 q) N, ON

Claims (2)

[Claims] (1) A step of roll coating a thick film of high heat resistant resin varnish on a substrate using a rotating roll having grooves, a step of smoothing the coating surface by rotating the substrate, and a step of baking the substrate. A method for manufacturing a resin-coated substrate, comprising: (2) Roll-coating a thick film of high heat resistant resin varnish on the substrate using a rotating roll having grooves, heating and curing the high heat resistant resin at 40°C to 200°C, and rotating the substrate. A method for manufacturing a resin-coated substrate, comprising the steps of: smoothing the coating surface by smoothing the coating surface; and firing the substrate.