JPH067816Y2 - Coating device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to photographic light-sensitive materials such as photographic film and photographic paper, photoengraving materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive recording paper, and heat-sensitive recording paper. The present invention relates to an improvement of an apparatus for applying a liquid coating composition (hereinafter referred to as a coating liquid) to a continuous flexible support (hereinafter referred to as a "web") which continuously runs in the production of a recording material, and the like. And a bar coating device.

[Conventional technology]

Conventionally, various devices have been proposed as devices for applying a coating liquid to a web that is continuously running. Generally, the coating device is a part that transfers the coating liquid to the web (hereinafter,
It is called "application system". ) And a portion for measuring the coating liquid transferred to the web to a desired coating amount (hereinafter referred to as “measuring system”), the coating devices are classified according to the difference between the application system and the measuring system. It was

A roller coating device, a dip coating device, a fountain coating device, etc. have been known based on the difference in the application system, and an air knife coating device, a blade coating device, a bar coating device, etc. have been known based on the difference in the measuring system. In addition, as an application and weighing are equivalent in the same part, an extrusion coating device, a blade coating device,
Bar applicators and the like were known.

Among these coating devices, the bar coating device or the roller coating device transfers excess coating liquid and the web to the coating liquid, and then the bar coating device or the roller coating device rotating at a slower peripheral speed in the opposite direction to the web or the web causes excessive coating liquid. Scrape off the coating liquid,
It has been widely used because it has a desired coating amount and has a feature that a thin device can be coated at high speed with a simple device and operation.

For example, FIG. 3 is a schematic view showing an example of a bar coating device using a coating rod for a conventional coating device disclosed in Japanese Patent Publication No. 58-4589, which is a web 1 which is continuously run. A coating rod (hereinafter referred to as a bar) 2 is rotated in the same direction or the opposite direction. A bar supporting member 3 is provided over the entire length of the bar 2, and has a function as a liquid feeder that prevents the bar 2 from being bent and supplies the coating liquid 4 to the bar 2. That is, the coating liquid 4 is supplied from the liquid supply port 5 provided in the bar support member 3 into the liquid supply guide groove 7 formed between the bar support member 3 and the dam member 6, and is picked up by the rotating bar 2 and applied to the web 1. However, at this time, the coating liquid 4 is weighed at the contact portion between the web 1 and the bar 2 so that only a desired coating amount is applied to the web 1 and the other flows down and the newly supplied coating liquid 4 is applied. At the same time, a liquid pool 8 is formed. Therefore, in a steady state, the coating liquid 4 is applied to the webb 1 via the liquid pool 8.

[Problems to be solved by the device]

However, when applying a coating solution with high color density,
Even when the method proposed in JP-B-58-4589 is used, the turbulence of the liquid flow generated in the liquid pool 8 which is the application part is directly manifested as uneven measurement, that is, a streak failure on the coating surface. was there.

On the other hand, according to the coating apparatus disclosed in JP-A-59-123568, which is characterized in that the flow straightening plate is provided in the liquid pool, the streak failure on the coating surface can be prevented to some extent. I found out, however,
When the coating liquid contains a large amount of low-boiling components, or when a coating liquid having low fluidity is applied, streak failure occurs as the coating speed increases.

The present invention solves the above problems, and when there are many low-boiling components in the coating liquid or when a coating liquid with low fluidity is applied,
An object of the present invention is to provide a coating device that does not cause streak failure on the coating surface even if the speed increases.

[Means and Actions for Solving Problems]

The object of the present invention is to (1) supply a coating liquid so that a liquid pool is formed immediately before a contact portion between a rotating bar and a continuously running web, and apply the coating liquid to the web. In the apparatus described above, the tip of the dam member forming the liquid pool is a flat surface having a length of 0.1 to 1 mm.

(2) The tip of the dam member forming the liquid pool has a radius of 0.
A curved surface of 1 to 2 mm.
(1) The coating device according to the above.

Can be achieved by

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

FIG. 1 is a side sectional view of one embodiment of the coating apparatus of the present invention (a)
And a partially enlarged view (b).

In FIG. 1, when the tip 11 of the weir member 6 is a flat surface and the length of the flat surface is longer than 1 mm, the coating liquid 4 does not overflow on the inclined surface 12 of the weir at all. Alternatively, even if the overflow occurs, a part of the overflow does not occur in the width direction, and the coating unevenness due to the overflow remains.

On the contrary, there is almost no flat surface of the tip 11,
If it is a knife-shaped surface, that is, if it is 0.1 mm or less, it becomes difficult to guarantee a uniform overflow in the width direction when the knife-shaped surface is scratched during use, resulting in uneven coating. . Therefore, the length d of the minute flat surface is within a usable range from 0.1 mm to 1 mm.

Next, FIG. 2 is a side sectional view (a) and a partially enlarged view (b) of a coating apparatus showing another embodiment of the present invention.

In FIG. 2, when the tip portion 11 is a circular arc, if the radius r of the circular arc is too large than 2.0 mm, it becomes easier for the liquid to overflow rather than the previous example. The amount is insufficient, a liquid pool cannot be formed, and the coating liquid 4 cannot be applied to the web 1.

Further, when the radius r of the arc of the tip portion 11 is smaller than 0.1 mm and becomes a knife-like surface, the distance between the flat surfaces in the previous example is small, and when the knife-like surface is scratched, it is spread across the width direction. It is difficult to guarantee a uniform overflow, which causes uneven coating.

At this time, the rotation direction of the rod can be either forward or reverse,
There are no restrictions on the number of rotations.

The coating liquid in the present invention is not particularly limited, and includes water or organic solvent liquid of a polymer compound, pigment water dispersion liquid, colloidal solution and the like. Also, the physical properties of the coating liquid are not particularly limited, but the lower viscosity is suitable for the condition of the liquid coated on the web.
In particular, a state of 50 cp or less is suitable. The surface tension is not particularly limited, but preferable results can be obtained at 50 dyne / cm or less.

The web in the present invention means paper, plastic film,
Includes resin coated paper, aluminum web, synthetic paper and the like. The material of the plastic film is, for example, polyolefin such as polyethylene or polypropylene, vinyl polymer such as polyvinyl acetate, polyvinyl chloride or polystyrene, polyamide such as 6,6-nylon or 6-nylon, polyethylene terephthalate, polyethylene-2, Polyester such as 6-naphthalate, polycarbonate, cellulose triacetate, cellulose acetate such as cellulose diacetate and the like are used.
Polyolefin such as polyethylene is typical as the resin used for the resin coated paper, but the resin is not necessarily limited to this.

The thickness of the web is not particularly limited, either, 0.01 mm to 1.
It is advantageous that it can handle about 0 mm and has versatility.

The bars used in the present invention include wire bars and grooving bars.

If a wire bar is used in the present invention, a suitable bar diameter is 6 mm to 25 mm, preferably 6 mm to 15 mm. If the diameter is larger than this, vertical streaks are likely to occur in the coating film, which is not preferable. Also, if the diameter is smaller than this, difficulty will occur in production. The wire diameter is 0.
07-1.0 mm, preferably 0.07-0.8 mm is suitable. When it is larger than this, the coating amount becomes too large,
It is not suitable as a method of using a bar coating method effective for high-speed thin layer coating, and if it is smaller than this, it becomes difficult to wind a wire to produce a wire bar, and strength problems arise. Although metal is used as the material of the wire, stainless steel is most suitable from the viewpoint of corrosion resistance, wear resistance, strength and the like. The wire may be plated on the surface to further improve wear resistance. Hard chrome plating is especially suitable.

Further, when the groove cutting bar is used in the present invention, the groove pitch is preferably 0.1 to 1.0 mm, preferably 0.2 to 0.8 mm, and the cross-sectional shape which is approximate to a sine curve is particularly preferable. Are suitable. However, the sectional shape is not necessarily limited to such a sectional shape, and another sectional shape can be used. Generally, there is a certain correspondence between the groove bar and the wire bar, and when the area per unit length of the space below the line connecting the peaks of the protrusions in each section is the same, the same application under the same conditions It is said that it is suitable for application of a quantity. Therefore, based on such correspondence, it is possible to select an appropriate groove cutting bar based on the knowledge of the wire bar.

As the material of the bar, metal is preferable from the viewpoint of corrosion resistance and strength, and stainless steel is particularly suitable.

Further, as the material of the groove cutting bar, metal, particularly stainless steel, is suitable from the viewpoint of corrosion resistance, strength and wear resistance.

Since the bar rotates at a high speed, the bar supporting member must be made of a material having a small resistance to friction with the bar (wire in the case of a wire bar). Examples of the material of the bar supporting member and the dam member preferably used in the present invention include fluororesin, polyacetal resin, polyethylene resin, polystyrene resin, and the like, and among these, the name of Teflon (product name of DuPont, USA) The polyacetal resin known by the name of polytetrafluoroethylene, Delrin (trade name of DuPont, USA) is particularly preferable in terms of friction coefficient and strength. Furthermore,
A material obtained by adding a filler such as glass fiber, graphite or molybdenum disulfide to these plastic materials can also be used. Further, after the bar supporting member is made of a metal material, the surface of the bar supporting member may be coated or adhered with the above-mentioned plastic material to reduce the coefficient of friction with the bar. Alternatively, various metal materials impregnated with the above-mentioned plastic materials, for example, aluminum polytetrafluoroethylene impregnated materials can be used as the bar supporting member.

(Example) An example will be given to further clarify the effect of the present invention.

Example 1 A coating solution having a composition and physical properties shown in Table 1 was applied to the surface of a polyethylene terephthalate film having a thickness of 200 μm and a width of 1000 mm by using a coating apparatus shown in FIG.
The coating amount was changed to 0, 70 and 100 m / min and the coating amount was 50 cc / m ² .

The liquid feed amount at this time was 3, 5, 7 / min, respectively. Further, d of the weir block of the coater is 0.3 mm.

The wire diameter of the wire bar used here is 0.7 mm
And the diameter is 12 mm.

When the coating surface coated by such a coating method was inspected, no coating stripe was generated on the wet surface immediately after coating at any speed, and no coating stripe was generated on the dried coating surface.

Comparative Example-1 The coating solution shown in FIG. 1 was applied using the coating apparatus shown in FIG. 3 and the same rod as shown in Example-1. The liquid transfer rate at this time was 4.5, 6.7, 9 / min.

At 40 m / min, several streaks are generated in the width direction, and at 70 m / min, strong streaks are generated on the entire surface.
Even stronger streaks occurred at 100 m / min.

[Effect of device]

As is apparent from the above, when the coating liquid of the present invention contains a large amount of low boiling point components or when a coating liquid having low fluidity is applied, the coating surface is streaked even if the coating speed is increased. No troubles occurred, high-speed coating was possible, and productivity and product quality could be improved.

[Brief description of drawings]

1 and 2 are a side sectional view (a) and a partially enlarged view (b) of one embodiment for explaining the bar coating apparatus of the present invention, and FIG. 3 is an example of a conventional bar coating apparatus. It is a side sectional view explaining. 1 ... Web, 2 ... Bar 3 ... Bar support member 4 ... Coating liquid, 5 ... Liquid supply port 6 ... Dam member, 7 ... Liquid supply guide groove 8 ... Liquid pool, 9 ... Pass roll 10 ... Coating layer 11 ... Tip of dam member d ... Length of tip r ... Radius of tip

Claims (2)

[Scope of utility model registration request] 1. An apparatus for supplying a coating liquid so as to form a liquid pool immediately before a contact portion between a rotating bar and a continuously running web, and coating the coating liquid on the web, The tip of the dam member forming the liquid pool has a length of 0.
An applicator characterized by having a flat surface of 1 to 1 mm. 2. The coating apparatus according to claim 1, wherein the tip of the dam member forming the liquid pool has an arcuate surface with a radius of 0.1 to 2 mm.