JPH01258772A - Coating method - Google Patents

Abstract

PURPOSE:To execute the rapid transfer to a stable state with a reduced pressure system slide bead coating system by electrifying a material to be coated to a specified electrostatic charge potential and maintaining the degree of pressure reduction under a normal degree of pressure reduction or below prior to coating and increasing the degree of pressure reduction to the above-mentioned degree or above after the coating. CONSTITUTION:A reduced pressure slide hopper forms a bead 8 at front end of a slide surface 5, i.e., the point proximate to a base 7 by allowing a coating liquid 6 to flow in the order of a liquid feed pump 2, a manihold 3, a slot 4, and the slide surface 5 and is provided with a reduced pressure chamber 10 in proximity to the advance side of the base 7 supported by a back up roller 9. A voltage is impressed to an electrode 11 of an electrifying part 13 to electrify the base 7 to the specified electrostatic charge potential and the degree of the pressure reduction in the reduced pressure chamber 10 is maintained at the normal degree of pressure reduction or below prior to the coating. The degree of pressure reduction is maintained under the normal degree of pressure reduction or above for a prescribed period of time and is then transferred to the normal degree of pressure reduction after the coating. As a result, the troubles such as thick coating and line coating trouble near the coating part are minimized and the rapid transfer to the stable normal state is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of applying a coating liquid to a running web. Furthermore, the present invention relates to a coating method in a reduced pressure slide bead coating method. In particular, when coating photographic light-sensitive materials, magnetic recording materials, information recording paper, etc., it is extremely important from the standpoint of quality assurance and economic cost to prevent failures that tend to occur near the coating area of the support to be coated. In the vacuum slide bead application process when it is important,
This invention relates to a coating method that minimizes thick coating, streak failure, etc. during coating, and allows a rapid transition to a stable steady state.

(Prior art and problems, α) The reduced pressure slide bead coating method is described in US Pat. No. 2,681.
No. 294, L76L419, and No. 2,761,791. The method disclosed here is
This method maintains the bead stably in a steady state, but in transient conditions such as during coating, in addition to problems such as thick coating and streaks, phenomena such as air entrainment occur as the coating speed increases, resulting in 10 serious problems with the product. It had the drawback of causing loss.

Methods for achieving stabilization and uniformity during coating are described, for example, in U.S. Pat.
No. 1 discloses a method of maintaining an intermediate degree of vacuum for a certain period of time while lowering the pressure from a high degree of vacuum to a steady level of vacuum.

The inventors investigated the optimal conditions while closely observing the transient phenomena during the initial application, and found that the optimal value for the degree of decompression differs between the moment the bead is formed and the time after the bead is formed. U.S. Patent No. 3,122,01877'f
Akira m 7, Aruiha special 11rl Showa f32-12145
It has been found that the method described in Publication No. 1, which starts from a high degree of vacuum at the moment of application, may cause liquid scattering or air entrainment, which may have the opposite effect.

On the other hand, as a method for stabilizing coating during steady state, a method is known that utilizes the charge on the surface of the support. The method of
No. 69 describes a method of charging a support having an uneven surface by applying a DC electric field.

In addition to the optimal control conditions for the degree of reduced pressure mentioned above, the inventors also conducted research on applying the stabilization method by charging to stabilization at the start, and found that the ff method by charging supports the coating liquid at the start. Although it is effective in improving wettability on the body, it alone may not be a condition for quickly transitioning to a stable steady state. I found out.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art, minimize failures such as thick coating and streak failures in the vicinity of the coating area in the reduced pressure slide bead coating method, and provide stable coating. It is an object of the present invention to provide a coating method that allows rapid transition to a steady state.

(Means for resolving the problem) This purpose is to charge the support to be coated to a constant charging potential before coating in the reduced pressure slide bead coating method, and to lower the degree of vacuum to a constant level of vacuum or less. After applying, keep the degree of decompression above the steady decompression degree for a certain period of time,
This is achieved by a coating method characterized in that the pressure is then shifted to a steady state of reduced pressure.

Figure rjS1 shows the configuration of the vacuum slide bead coating device used in the present invention.

The vacuum slide hopper 1 flows the coating 'or, 6 in the order of the liquid supply pump 2, the manifold 3, the slot 4, and the slide surface 5, and forms a bead 8 at the tip of the slide surface 5, that is, at a point close to the support 7. The decompression chamber 10 is tilted close to the entry side of the support 7 supported by the bank up roller 9. Moreover, the decompression chamber 10
A charging section 13 comprising an electrode 11 and a grounding roller 12 is disposed further upstream of the charging section 13 . Furthermore, in order to execute the smearing sequence of the present invention, the charging section 1 is activated by a program.
3 and the degree of pressure reduction in the vacuum chamber 10 are provided.

FIG. 2 shows the smearing sequence, which is a feature of the present invention.
That is, it shows control patterns for the charging potential of the charging unit 13 and the degree of pressure reduction in the reduced pressure chamber 10 before and after painting.

The horizontal axis in FIG. 2 represents the moment when the decompression slide hopper 1, which had been separated before coating, starts to move to approach the support 7 supported by the backup roller 9, and α is lff1. It is the axis.

At the same time as starting the decompression slide ho 7 pa 1 transfer, the obi?
Apply a voltage to the electrode 11 of 1J13 to bring the support 7 to a constant band 7ji potential? l? Make it electric.

The value of the degree of decompression in the decompression chamber 10 is the second
The value of the degree of vacuum is changed from 8 to B after the tip of the slide surface 5 approaches the support 7 and a bead 8 is formed, which is set to the value shown by 8 in the figure. When the bead 8 reaches a stable state after passing through a transient state during coating, the pressure changes to a steady state of decompression C, and the coating is completed.

The charging may be stopped when changing the degree of reduced pressure to Δ or B after being smeared, or may be continued as it is.

(Function) Hereinafter, embodiments based on the above device configuration and smearing sequence and their functions will be described.

The value C of the degree of reduced pressure in the steady state is determined by the composition of the coating liquid to be applied,
Although it is well known that it varies depending on conditions such as coating amount and physical properties, a case where a range of -15 to -851**H20 is preferable will be explained.

The charging potential before application is preferably such that it increases the adhesion of the coating liquid 6 to the support 7 and prevents thick coating at the tip, and for example, a range of 0.1 to IK'//cm is effective. . By setting the degree of vacuum during application to a lower value A, it is possible to prevent the coating liquid from scattering at the moment of application, and to ensure uniform application in the width direction.
mmt120, preferably -20 to -601a111
1□0 is good.

Setting the degree of reduced pressure after application to a higher value B has the effect of stabilizing the bead in a short time, and a range of -50 to -100 x 11□0 is good.

The timing of switching from the degree of reduced pressure A to the degree of reduced pressure B does not have to be immediately after application, but is preferably within 10 seconds in order to speed up subsequent stabilization. Also, the time to maintain the degree of reduced pressure B is 0.
．． A range of 5 to 10 minutes is good. Further, the degree of pressure reduction may be changed instantaneously or gradually.

These sequences can be easily and reliably executed by a preset program depending on the composition and conditions of the coating liquid to be applied.

The coating materials used in the present invention include those with various liquid compositions depending on the application, such as coatings of light-sensitive emulsion layers, undercoat layers, protective layers, back layers, etc. in photographic materials. liquid, magnetic layer such as in magnetic recording materials, undercoat JM,
Lubricant, maintenance: J! This includes coating liquids for layers, back layers, etc., scraps containing microcapsules as a main component such as in information recording paper, and coating liquids for layers containing color development uniformity as a main component.

Further, the web used in the present invention includes paper, plastic film, Lennon coated paper, synthetic paper, and the like. The material of the plastic film is, for example, polyolefin such as polyethylene and polypropylene, vinyl m+ such as polyvinyl acetate, polyvinyl chloride, and polystyrene.
polyamide such as body, a, a-nylon, 6-nylon,
Polyethylene terephthalate, polyethylene-2,6-
Polyesters such as 7-talate, polycarbonates, cellulose acetates such as cellulose triacetate, and cellulose guaacetate are used. Further, the resin used for resin-coated paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto.

(Example) In order to clarify the effects of the present invention, examples will be shown below.

The method according to the smearing sequence according to the present invention and the special features described in 1986 can be carried out using the M-configured apparatus shown in FIG. 1.
The method described in JP-A No. 1221451, that is, the method of maintaining an intermediate degree of decompression for a certain period of time while lowering from a high degree of decompression to a steady degree of decompression without charging, and JP-A No. 61-146369
Comparative coating was carried out with the method described in the publication, ie, the method in which charging is performed but the degree of vacuum is controlled under conventional conditions.

(1) Example 1 As Example 1 of the method of the present invention, the charging potential of the support was set to 0.
, 5KV/cm, and the degree of vacuum A before painting is -35m.
mH2Q, degree of vacuum B after painting is -80IIlzO1
The degree of steady pressure reduction C was set at -50 mm 1 lzO.

Further, the time to maintain the degree of vacuum A was set to 3 seconds, and the time to maintain the degree of vacuum B to 40 seconds IM.

As Comparative Example 1 and Comparative Example 2, under the condition that the support was not charged, the degree of vacuum was 1120 ml I□O (Comparative Example 1) or -9011611120 (Comparative Example 2), B
was set to -801111H20, and C was set to -50 mmHtO, and the time for maintaining each degree of reduced pressure was the same as in Example 1.

The coating speed was 180 m/win.

The results are as shown in the f51 table, Example 1 of the method of the present invention
In Comparative Example 1 and Comparative Example 2, a stable start was possible without the occurrence of thick coating in the applied area or streak failure, whereas in Comparative Examples 1 and 2, thick coating in the applied area or streak failure due to liquid scattering was possible. Occurrence was observed.

(2) Example 2 Next, what about the support? In order to compare the pattern of reduced pressure in the case of I7 electric current, as Comparative Example 3, a method of starting from a higher reduced pressure during application was compared with Example 2 of the method of the present invention.

As shown in the tlS2 table, Example 2 of the method of the present invention was under the same conditions as Example 1, and Comparative Example 3 was under the same conditions as the mT1 of the support.
The potential is 0.5KV/e, and the degree of pressure reduction is Δ-9.
0+5ml□0, B 80m So H20, C-5
0m1120, and the time for maintaining each degree of vacuum was the same as in Example 2.

As a result, in Comparative Example 3, there was no thick coating in the coated area, but there was a streak failure that appeared to be caused by air entrainment, whereas in Example 2 of the method of the present invention, a streak failure occurred. We were able to get off to a stable start.

! Table n2 (3) Example 3 Furthermore, regarding Comparative Example 4, under the conditions for charging the support, the degree of vacuum A started from a low value and was directly transferred to the degree of vacuum C without going through the step of the degree of vacuum B. , compared with Example 3 of the method of the present invention.

Example 3 of the method of the invention has a coating speed of 150+a/s.
The conditions were the same as in Example 1 except that the coating speed was 150 m/sin, the charging potential of the support was 0.5 KV/cm, and the degree of vacuum A was -35.
The degree of decompression of C is -5 without passing the degree of decompression of mm1I□O1B.
0 mackerel-1120.

Table 3 As a result, as shown in m3B, in Comparative Example 4, although there was no thick coating in the applied area, it took time to stabilize the bead, and uneven failure remained until 100m after the start. In Example 3 of the method of the present invention, stable coating was achieved from the start.

(Effects of the Invention) According to the present invention, it is possible to prevent delays in drying due to thick coating at the tip of the coating, contamination of the process due to liquid scattering, and occurrence of streak failures due to air entrainment. Stabilization of the bead occurs quickly. This effect is particularly important for quality assurance, as it prevents failures that tend to occur near the coating area of the support, such as when coating photographic light-sensitive materials, magnetic recording materials, Q-information recording paper, etc. It is extremely effective in cases where economic costs are important.

[Brief explanation of the drawing]

Figure Pt51 shows the configuration of the vacuum slide bead coating apparatus used in the present invention, and Figure 2 shows the coating sequence of the present invention. 1... Decompression slide hopper 2... Liquid supply pump 3 fists, φ manifold 4... Slot, 5... Slide 6... Coating liquid, 7... Support body 8... Bead 9 ... Patsukua Nofu a-ra 10... Decompression chamber, 11... Electric image 12... Earth roller 13... Charging part, 14... Exhaust bong 7° 15.
...Control Department Patent Applicant: Fuji Photo Film Co., Ltd. Figure 1, Figure 2, Figure 2, 1, Indication of the case: Application No. 17026 of 1972, 2, Title of the invention: Coating method 3, Person making the amendment Relationship Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name (520) Fuji Photo Film Co., Ltd. Contact address 2 Nishi-Azabu, Minato-ku, Tokyo 106
T Entrance 26, No. 30 Date of amendment order: 141, 1964 (shipment date) i Subject of amendment Drawing (I 11z2 & Contents of amendment as shown in attached sheet)

Claims (2)

[Claims] (1) Decompression method In the slide bead coating method, before coating, the support to be coated is charged to a constant charging potential and the degree of vacuum is kept below the steady vacuum degree, and after coating, the degree of vacuum is set to the steady vacuum degree. A coating method characterized by maintaining the above pressure for a certain period of time and then shifting to a steady degree of reduced pressure. (2) The coating method according to claim 1, wherein the constant charging potential is in the range of 0.1 to 1 KV/cm, and the degree of reduced pressure after coating is in the range of -50 to -100 mmH_2O.