JPS60150865A - Coating method - Google Patents

Abstract

PURPOSE:To coat uniformly a thin film at high speed by opposing the extruding port of a coater head to the lower surface of a base body to be coated, keeping the head apart from the base body when the body is coated, and bringing the head into contact with the body when the body is not coated. CONSTITUTION:The extruding port 6 of a coater head 1 is opposed to the lower surface of a base body 2 to be coated. The extruding port 6 of the coater head 1 is abutted on the surface of the base body 2 to be coated which is stretched by a supporting body 3, when a low-viscosity liquid material 4 is not extruded. And the extruding port 6 is kept slightly apart from the surface of the stretched base body 2, when the low-viscosity liquid material 4 is extruded. Moreover, the viscosity of the low-viscosity liquid material is regulated to <1 poise (at 1sec<-1> shear rate). A thin film can be uniformly coated at high speed in this way and besides the loss of the coating liquid is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for applying a low-viscosity liquid substance, and more particularly to a high-speed method for applying a low-viscosity liquid substance with improved coating unevenness and loss of coating liquid. .

(Prior art) As a method for applying a viscous liquid substance, for example, IJ
/<- Thrall coating method, gravure coating method, doctor knife coating method, air doctor coating method, extrusion coating method, etc. are widely known and have been put into practical use.

However, the conventionally known coating methods are not always satisfactory in uniformly applying a thin film of a low-viscosity liquid material having a viscosity of 1 poise at high speed. For example, in the case of reverse roll coating, during high-speed coating of a low-viscosity liquid substance, the coating liquid may scatter from the roll or cause uneven coating. Furthermore, when performing thin film coating, it is often necessary to adjust the gap between the applicator roll and metering roll to less than approximately 1 μm (although it is actually difficult to adjust the gap uniformly in this way). Furthermore, it is difficult to uniformly form the wafers, kua, and brolls that support the substrate to be coated, and the nonuniform pattern directly causes uneven coating of the coating layer.Furthermore, when dust, etc. adheres to the wafers, kua, and burols, Similar transfer unevenness occurs.

Depending on the type and pressure of the coating liquid, streaks may occur and completely uniform coating may not be obtained. The coating film thickness is significantly influenced by the viscosity of the coating solution and the chicken tropism.

Therefore, extremely high precision is required when manufacturing or installing backup rolls, metering rolls, ablator rolls, etc., and even if they are manufactured or installed with high precision, fluctuations in the coating film thickness of several microns are unavoidable. Ino is the current situation.

On the other hand, in the case of gravure coating, the transfer of the coating liquid to the gravure roll, transfer roll, or substrate to be coated varies greatly depending on the viscosity of the coating liquid, and this effect is particularly noticeable in the case of thin film coating. Furthermore, in gravure coating, the gravure roll must be replaced each time the coating amount is changed. In many cases, there is no gravure mesh until the end of the drying process (and even coating becomes impossible).In the case of extrusion coating, it is easier to control the film thickness by controlling the flow rate alone than in the above coating methods. In addition to this, the coating surface properties are also good.

However, for example, Japanese Patent Publication No. 46-27158 and No. 4
In the case of the extrusion coater described in No. 6-16330, there is a gap between the liquid extrusion port of the coater and the substrate to be coated.

It must be set to several tens of microns or less by brawling,
When coating by extruding the dispersion liquid in such a narrow gear, the substrate to be coated may be damaged by dirt or aggregates in the coating liquid, or by slight distortion of the coater. In severe cases, it may be amputated. Furthermore, it is difficult to apply a thin film using extrusion coating. Japanese Unexamined Patent Publication No. 5+1-138036 describes a device that performs coating by discharging a coating liquid from a liquid injector onto a strip without restricting the traveling position of the strip.

The coating apparatus disclosed above can perform coating relatively conveniently, but if the coating speed is increased to 90 m/7 minutes or more and the coating is applied under conditions such that the thickness of the coated film after drying is 6 μm or less, streaks suddenly occur. This causes uneven coating to occur, making it impossible to apply uniformly.

The coating method using this apparatus was developed for the purpose of coating a photographic emulsion in which silver halide is dispersed in water, as described on page 3, line 9 of the above specification.

Also, in special public issue No. 84-7306, it was sent to the coater.

There is no web supporting roll in the part where the door runs and comes into contact with the L-tube. The device is described.The coating method using this device provides relatively good coating, but
Increase the coating speed to 90 rnZ or more, and apply a thin film to 5 to make the thickness of the film after drying 1.5μ or less.
In the case of fx c, streaks and coating unevenness rapidly increase, making uniform coating extremely difficult. Furthermore, because the edge of the coater has an acute angle, the coater can be scratched or scraped during cleaning or other handling, making it difficult to maintain smoothness. occurs, making it extremely difficult to use it practically.

Also, JP-A-58-189070 and JP-A No. 58-189
A coating method is also described in Publication No. 069, but in this coating method, the viscosity of the coating liquid is 1' poise (Shearley F 1
High viscosity magnetic powder dispersion K with a viscosity of
r! This is applicable to coated materials having a film thickness of 1 μm or more, preferably around 6 μm, after drying and before calendering. When such a coating method is applied to a coating material having a film thickness of 1.5 microns or less, particularly 1 micron to 0.1 micron, coating streaks occur frequently, making practical coating impossible.

(Objective of the Invention) Therefore, an object of the present invention is to provide a method for applying a low-viscosity liquid substance, which can uniformly apply a thin film at high speed, and further reduces the loss of the coating liquid.

(Structure of the Invention) The object of the present invention is to provide a method for coating a low-viscosity liquid substance onto a continuously moving substrate by an extrusion method, in which an extrusion port of a door is connected to a coater of a coating device. The low viscosity liquid substance is in contact with the lower surface side of the coated substrate at a position where there is no support supporting the coated substrate, is substantially perpendicular to the coated substrate, and the low viscosity liquid substance flows out in a direction opposite to the direction of gravity. (It is installed and sent to the coater of the coating device.)

The tip of the extrusion port of the dome and the substrate to be coated are in contact with each other when no coating is being performed, and when coating is being performed, they are separated and the coating is performed, and the low viscosity liquid substance is applied. This can be achieved by a coating method in which the viscosity is less than 1 poise (15 ec=).

Hereinafter, the present invention will be explained in more detail with reference to embodiments of the drawings.

FIG. 1 is a schematic side view of a coating device used in the coating method of the present invention. In FIG. 1, 1 is a coater of a coating device, 2 is a substrate to be coated, and 3 is a rotatable pair of supports that support the Fi substrate 2. In addition, θ represents the angle between the blade side surface of the blade 1 (described later) and the substrate 2, and is thicker than 30'. , 90' is necessary to obtain a good coating film.

A low-viscosity liquid substance stored in the 4-layer coater head 1 is guided to the outflow path 5 and extruded from the extrusion port 6.
It is applied to the substrate 2 being transported.

The extrusion port 6 of the coater head 1 in the coating apparatus according to the present invention is arranged at a position where the rotatable support 3 supporting the substrate 2 does not exist, and is installed at a position substantially perpendicular to the substrate 2. One of the characteristics of the coating method of the present invention is that the low-viscosity liquid substance 4 flows out in a direction opposite to the direction of gravity to perform coating.

In other words, in the case of a coating method other than the present invention, in which the door to the coater is arranged horizontally and the substrate to be coated is moved in the vertical direction, the action of gravity causes the door to the coater to move in the vertical direction. Coating liquid and dry solids tend to adhere to the lower end of the contact area with the substrate to be coated, and this phenomenon is particularly noticeable in the case of coating liquids containing volatile organic solvents, which often results in the formation of coating streaks. It could be the cause.

Furthermore, the coating method of the present invention is characterized in that when the low-viscosity liquid substance 4 is not extruded, that is, when coating is not performed, the extrusion port 6 of the dome
The extrusion port 6 is in contact with the surface of the coated substrate 20 which is stretched by the support 3, but when the low-viscosity liquid substance 4 is being extruded, that is, when the coating is being applied, the extrusion port 6 is stretched. There is a distance K that is slightly spaced apart from the surface of the substrate 2 to be coated.

Next, in order to more specifically understand the structure of the coater according to the present invention, a more detailed explanation will be given with reference to a partially enlarged view of FIG.

Figure 2 shows the droplet to the coater when no coating is being performed.
FIG. 3 is a partially enlarged view showing the state of FIG.

In the figure, 1m and lb are the upper blade and lower blade of the door 1, respectively, to the coater forming the extrusion port 6 for the low-viscosity liquid material 4.

In the coater according to the present invention, in Do I, the tip of the blade Ia located on the carry-out side with respect to the conveying direction (arrow) K of the substrate 2 to be coated protrudes (main) from the tip of the blade lb located on the carry-in side. In the invention, preferably about 1111), and as clarified above, the blade la
The angle between the side surface 1c and the substrate 2 to be coated is 300 to 90.
It is characterized in that it is set to °. That is, when the amount exceeds 0 and when it becomes less than 0, significant coating streaks occur.

In the present invention, the angle formed between the side surface 1d of the blade lb and the substrate 2 to be coated may be arbitrary and does not need to be specifically defined. Preferably, it is at an acute angle with respect to the coated substrate.

The low-viscosity liquid substance 4 used in the present invention includes:
For example, polyurethane including modified polyurethane, vinyl chloride-vinyl acetate copolymer, nitrocellulose, phenoxy, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyester, butyl acrylate-acrylonitrile copolymer, epoxy, etc. dispersion in which lubricants such as surfactants such as polymers and lecithin, fatty acid esters, fatty acids, silicon compounds, and fluorine-containing compounds are dissolved in organic solvents such as cyclohexanone, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, and toluene. Alumina, carbon black, titanium dioxide, calcium carbonate, graphite, tungsten disulfide, molybdenum disulfide, boron nitride, silicon dioxide, α- and γ-iron oxides, cobalt-based iron oxide, chromium dioxide, Examples include those in which powder of ferroalloy containing metals such as Kel and cobalt is dispersed.

The weight i% of the above powder is 0.5% to 20%, preferably 2
It is around %.

Alternatively, add 0.01-1% of a low-molecular compound in the above solvent.
It may be possible to dissolve only about %.

In the present invention, as described above (when the low-viscosity liquid substance 4 is not being extruded), the tip of the coater head 1 is in contact with the stretched substrate to be coated.

The tension of the coated substrate 2 at this time needs to be increased as the coating speed is faster, the viscosity of the coating liquid is higher, and the flow rate of the coating liquid is lower, but it is usually 10 to 100.
It is preferably in the range of 0 g/. Tension is 1097
If the coating speed is less than cm, the coating speed is 90 m, and when coating a liquid with a viscosity of 1 poise or less at Anxr or higher, +/C causes liquid shortage or coating streaks. Furthermore, if the thickness is greater than 1000 g/m, streaks will occur.

The pressure of the low-viscosity liquid substance 4 flowing out into the coater depends on the coating film thickness and coating speed, but in practice it is preferably on the order of 0.1 to 9 kg/771'. If the pressure is less than 0.1 ky/m', when a liquid with a viscosity of 1 poise or less is applied at a coating speed of 90 mA or more, liquid shortages or coating streaks occur. Moreover, if it is thicker than 9 kg/m, the film thickness will be uneven and the center portion will be thick.

In practice, the viscosity of the low-viscosity liquid substance 4 used for coating in the present invention is 1 poise (shear rate 15 ec-'
(Ic) or less.

Regarding the coating temperature, if it is too high, the solvent will evaporate during the coating process, which is undesirable (but if it is too low, the viscosity will become too high, which is also undesirable. Therefore, the coating temperature in the present invention is set at around 10°C before and after heating. It is preferable that there be.

Next, regarding the coating speed, the effects of the present invention are most exhibited when the coating speed is 90 m 7 minutes or more.

According to the coating method of the present invention, the ability of the apparatus according to the present invention is exhibited to the highest degree when the coating film thickness is 4μ or less after drying.
It is even more effective when it is less than μ. However, in this case, the viscosity of the coating liquid is 1 poise (shear rate 15ec
−') must be as follows. The substrate to be coated to be used next has a thickness of 200μ to 5μ,
Alternatively, a polyester paste or the like with a thickness smaller than this may be used, but in the present invention, a substrate having a thickness of 20 μm or less is particularly preferable.

FIG. 3 is a schematic side view showing another embodiment of the coating device according to the present invention.

In the figure, 7 is an endless rubber blanket stretched between supports 30. This endless rubber blanket and door are used for the purpose of supporting and moving the coated substrate 2 stably and reliably, and the coating mechanism and conditions for the low-viscosity liquid substance 4 are shown in FIG. 1 above. There is no difference from the equipment used.

According to the coating method of the present invention performed using the coating apparatus according to the present invention described in detail above, it becomes possible to uniformly apply a thin film of a low-viscosity liquid substance at high speed.

In addition, the coating process does not damage or cut the substrate, and by accurately controlling the flow rate of the coating liquid using a liquid delivery means such as a gear pump, a film thickness of 4μ or less can be maintained constant and uniform. Can be applied.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Titanium dioxide, polyurethane, nitrocellulose, lecithin, cyclohexanone and tetrahydrofuran, 3=
A dispersion (Shearley) (viscosity at 15 ec-' centipoise) was applied at a coating speed of 100 m/min so that the film thickness after drying was 0.8 μm. Coating was carried out using the coating apparatus shown in FIG.

At this time, the tension of the coated substrate was 500 g/clL.

The obtained coated substrate was not cut or damaged during the coating process, and a coated thin film having a smooth surface was obtained. Since the flow rate of the coating liquid was controlled to be constant using a gear pump, the thickness of the coating after drying could be maintained extremely accurately from the beginning to the end of the coating.

Comparative example A dispersion liquid in which magnetic iron powder was dispersed in a solution of polyurethane, vinyl chloride-vinyl acetate copolymer, and lecithin dissolved in a 3:1 mixed solvent of cyclohexanone and tetrahydrofuran (viscosity at shear rate 1111Icl increased to poise) The film thickness after drying is 0 at a coating speed of 100 m/min.
．． Coating was carried out using the apparatus shown in FIG. 1 at a tension of 500 g/cn* on the substrate so that the coating thickness was 8 μ. The obtained substrate was not cut or damaged during the coating process, but there were many streaks on the coated surface.

(Effects of the Invention) According to the coating method of the present invention, a low-viscosity liquid substance can be coated quickly and uniformly in the form of a thin film, and the coated article will not be damaged.

[Brief explanation of the drawing]

FIG. 2 is a partially enlarged view of the same device, and FIG. 3 is a side view of a coating device according to another embodiment of the present invention. be. l...to the coater, do■ & and 1b...upper and lower blades lc, l
d... Side surfaces of upper and lower blades 2... Substrate to be coated 3... Support 4... Low viscosity liquid substance 5... (Dispersion liquid) flow path 6... (Dispersion liquid) ) Extrusion exit 7... Planga, To agent, patent attorney No 1) Parent-in-law A mouth?

Claims (1)

[Claims] In a method of applying a low-viscosity liquid substance to a moving substrate by an extrusion method, the extrusion port of the coating device transfers the liquid to the coater of the coating device at a position where there is no support supporting the substrate to be coated. It is disposed so as to be in contact with the lower surface side of the substrate to be coated, to be substantially perpendicular to the substrate to be coated, and such that the low-viscosity liquid substance flows out in a direction opposite to the direction of gravity, and to prevent extrusion of the coater head of the coating device. 1" and the substrate to be coated are in contact when coating is not being performed, and are separated when coating is being performed to change the coating process, and the viscosity of the low-viscosity liquid substance is 1 poise. (at a shear rate l 5ec-').