JP2009226340A - Coating device and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slide bead coating device capable of preventing a process trouble caused by thick coating at both ends, increasing the effect of suppressing thick coating and thin coating at both ends further, and making an efficient coating operation with a high yield, and a coating method. <P>SOLUTION: In the slide bead coating device, the slide surface outflow width of the slit of at least one layer is narrower than the inner surface width of the coating width regulation member on a slide surface, and the slit of the narrow width is in an inclined shape in which the slit width is reduced toward a slit exit inside a coating die. The coating method uses the coating device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a slide bead coating apparatus characterized by an internal shape of a coating die. The present invention also relates to a coating method using the coating apparatus.

  Conventionally, as a device for applying a coating solution on a web, various roll coating devices, gravure coating devices, blade coating devices, slide bead coating devices, slot coating devices, extrusion coating devices, curtain coating devices, slide curtain coating devices. The above-mentioned various coating apparatuses are properly used depending on the required accuracy and surface quality of the coating film, the type of coating liquid used, the restrictions on the operating conditions in the coating operation, and the like.

  In the above coating apparatus, in a roll coating apparatus, a gravure coating apparatus, a blade coating apparatus, etc., an excessive amount of coating liquid is supplied more than the coating film finally formed on the web, and an excessive amount of roll or blade is used. Since the thickness of the coating film finally formed on the web is measured at the stage of scraping the coating solution, it is called a post-metering coating device. On the other hand, in slide bead coating devices, slot coating devices, extrusion coating devices, curtain coating devices, slide curtain coating devices, etc., the amount of coating liquid corresponding to the coating film finally formed on the web is measured in advance. Since all of the coating liquid supplied and applied onto the web finally becomes a coating film formed on the web, it is called a pre-metering coating device.

  In this way, the pre-metering application device does not require an operation to scrape off the excessive coating liquid, so that a good coating surface quality is obtained and it is not necessary to recirculate the excessively supplied coating liquid. The liquid composition does not change with time, and a stable coating operation can be performed over a long period of time.

  In particular, a slide bead coating apparatus belonging to the above-mentioned pre-measuring coating apparatus supplies a plurality of coating liquids having different compositions to a coating die (hereinafter referred to as a die), and performs a multi-layer flow on the inclined slide surface of the die. Is a coating apparatus that realizes multi-layer simultaneous coating.

  As described above, since the slide bead coating apparatus can simultaneously apply multiple layers, it is suitable for efficient production of products having a multi-layered structure such as photographic photosensitive materials, printing plate making materials, and inkjet recording materials. It is a coating device.

  Each of the products described above requires a very uniform coating film thickness distribution in the width direction and the flow direction, but non-uniformity tends to occur particularly at the end in the width direction. The reason is described below.

  In a general slide bead coating device, the coating solution supplied from the inlet to the inside of the die is spread in the width direction by a cavity provided inside the die, and passes through a thin slit to make it uniform in the width direction. A thin laminar flow is formed and flows out on the inclined slide surface of the die surface. After that, a gravitational effect flows down the slide surface to form a multi-layer flow, and a so-called coating bead is formed by colliding with a high-speed running web while maintaining a certain distance (referred to as a bead gap) from the tip of the die. Is applied.

  Further, in order to keep the width of the multilayer flow flowing down the slide surface stable, an application width regulating member is often provided on the slide surface to support both ends of the multilayer flow. If this application width regulating member is not provided, there is a problem that the desired application width cannot be obtained or the application width is not stable due to contraction on the slide surface. Is essential, but the presence of the application width regulating member may deteriorate the uniformity in the width direction of the multilayer flow flowing down the slide surface.

  As a trouble caused by the deterioration of the uniformity in the width direction as described above, in some cases, the coating thickness is about twice as thick as the normal thickness in the extreme vicinity of the end portion (hereinafter referred to as edge thickness coating). May occur). In the dryer following the coating process, this edge thick coating part is very slow in drying, but when the edge thick coating part is undried, the undried part of the wound product adheres and winds up. Will not unravel and will cause serious process trouble. Therefore, although the edge thick coating portion may be set as a dryer that can be sufficiently dried to prevent non-drying, it is clearly wasteful use of drying energy.

  On the other hand, in contrast to the above-described edge thick coating, a thin coating (hereinafter referred to as edge thin coating) may occur in a wide range of 10 to 20 mm from the endmost portion as compared with the normal portion. The edge thick coating part and the edge thin coating part generated in this way are not the desired coating film thickness, and thus often fail to fully exhibit the performance as a product, and are cut off during product cutting, which causes a deterioration in yield. It was. In addition, when a wide application product obtained by the application operation is slit into a plurality of pieces and divided into a predetermined width, particularly when the edge thin coating occurs over a wide range as described above, the desired number of divisions or The clearance may not be obtained, and a very serious yield loss may be caused.

  Therefore, conventionally, various coating apparatuses and coating methods have been proposed in order to prevent process troubles and yield deterioration due to edge thick coating and edge thin coating. For example, a method of sucking the edge thick coating portion with a suction pipe (Japanese Patent Laid-Open No. Sho 56-73579), a spraying method (Japanese Patent Publication No. Sho 57-37388), an air flow diffusion method at both ends (Japanese Patent Laid-Open No. Sho 54-142248). No. 2), a method for separating both ends before final drying (Japanese Patent Laid-Open No. 54-159552), and the like. However, each of these methods uses a separately provided apparatus to prevent thick coating at both ends, which requires apparatus installation costs and requires maintenance.

  In Japanese Patent Application Laid-Open No. 59-206079, a method of applying a wider than predetermined coating width on the slide surface, and in Japanese Patent Application Laid-Open No. 63-144348, a liquid having a lower surface tension than the coating solution at both ends of the slide surface. There has been proposed a method of applying a low coating amount. In these methods, coating is performed with a width wider than a desired width, and the yield of raw materials is deteriorated by using a web, a coating solution, and the like.

  In JP-A-5-96223, there is a method of preventing edge thick coating and edge thin coating by using a die internal shape characterized by a cavity extending on an arc and an inclined slit. In contrast to the above-described methods, it is a good method that does not require a separate device and does not deteriorate the raw material yield. However, in the high flow rate range accompanying the recent high-speed application, it has become particularly difficult to suppress the thin edge coating. Further, due to the recent pursuit of resource saving and the pursuit of quality improvement, the allowable range of thin edge coating has become more severe, and the allowable range may not be satisfied.

  Further, in Japanese Patent Application Laid-Open No. 2002-254006, the slide surface outflow width of the slit of at least one layer is narrower than the inner surface width of the application width regulating member on the slide surface, and the narrow width. The slit has an inclined shape in which the slit width increases toward the slit exit inside the coating die, and an effect of preventing edge thick coating and edge thin coating by a coating apparatus is disclosed.

  The slide bead coating apparatus is generally used in a wide viscosity range from a low viscosity range of several mPa · s to a high viscosity range of several hundred mPa · s. However, the coating apparatus disclosed in JP-A-2002-254006 As disclosed in the examples, it is particularly effective in a relatively low viscosity liquid of 10 mPa · s or less. Therefore, when a high-viscosity coating solution having a coating solution viscosity of 20 mPa · s or more, more preferably 50 mPa · s or more, is applied, a sufficient edge thick coating suppression effect and edge thin coating suppression effect cannot be obtained.

On the other hand, in Japanese Patent Laid-Open No. 2001-212488, the slit width inside the coating die decreases toward the slit exit in an extrusion type curtain coating apparatus for the purpose of stabilizing liquid film curtain film formation at an ultra-low flow rate. And the coating device characterized by the slit width being wider than the curtain formation width is disclosed.
JP 2002-254006 A JP 2001-212488 A

  In view of the above-described problems, an object of the present invention is to provide a simple coating apparatus and coating method that exhibit a sufficient edge thickness coating suppression effect and edge thin coating suppression effect.

  In the slide bead coating apparatus, the above-mentioned object of the present invention is such that the slide surface outflow width of the slit of at least one layer is narrower than the inner surface width of the coating width regulating member on the slide surface, and the narrow width A certain slit has an inclined shape in which the slit width decreases toward the exit of the slit inside the coating die, and the coating liquid is applied onto the support by the coating apparatus according to claim 1. This was achieved by a coating method characterized by coating a coating solution having a viscosity of 50 mPa · s or more.

  According to the present invention, it is possible to provide a coating apparatus and a coating method that can obtain a sufficient edge thickness coating suppression effect and edge thin coating suppression effect.

  First, a general flow of coating liquid in the slide bead coating apparatus will be described. FIG. 3 is a schematic diagram of a cross-sectional shape of the slide bead coating apparatus of the present invention cut along a plane perpendicular to the width direction, and the direction A in FIG. 3 is referred to as a coating liquid flow direction. Here, the entire die E is configured by assembling the members 11, 11a, and 11b to each other, and each of these members is generally obtained by machining a metal such as stainless steel.

  In FIG. 3, the coating liquid of the first layer flows into the die from the inlet 1a, spreads in the width direction at the cavity 2a, flows into the slit 3a from the slit inlet 3ai, and passes through the slit 3a, which is a thin channel. By passing, it is rectified into a thin laminar flow that is uniform in the width direction, and flows out from the slit outlet 3ao onto the slide surface 4, that is, outside the die.

  Similarly to the first layer, the coating liquid of the second layer also flows out onto the slide surface 4 via the inlet 1b, the cavity 2b, the slit inlet 3bi, the slit 3b, and the slit outlet 3bo. Since the slide surface 4 is installed so as to have a certain inclination with respect to the direction of gravity, each coating liquid in a thin laminar flow flows down on the slide surface 4 in the direction A, and the first layer coating liquid. A state in which the second-layer coating liquid is placed on the surface, that is, a free surface flow of a double layer.

  FIG. 4 is a schematic diagram showing the slide bead coating apparatus of the present invention in a cross section in the coating liquid flow direction A, that is, a schematic diagram of a cross-sectional shape cut at a position B in FIG. Therefore, the C direction in FIG. 4 is the width direction. In FIG. 4, the coating liquid flowing down on the slide surface is allowed to flow while supporting both ends of the flow at the oppositely facing inner surfaces of the coating width regulating members 5 installed at both ends on the slide surface 4. , Keep the flow width stable. Therefore, the so-called coating width is determined by the inner surface width L5a of the coating width regulating member 5.

  In FIG. 3, the web 6 travels while being supported by the coating roll 7 at a position having a certain gap (referred to as a coating gap) from the tip of the slide surface 4, and the thin laminar flow away from the tip of the slide surface 4 is the web 6. By cross-linking towards, a so-called coating bead is formed and applied.

  Next, features of the slide bead coating apparatus of the present invention will be described. FIG. 1 is a schematic diagram of a cross-sectional shape of the slide bead coating device of the present invention cut in a direction orthogonal to the flow direction of the coating liquid. FIGS. 1 (a) and 1 (b) are slits 3a and 3b in FIG. It is a schematic diagram of the cross-sectional shape which cut | disconnected 3b in the orthogonal direction with respect to the coating liquid flow direction.

  On the other hand, FIG. 2 is a schematic view of a cross-sectional shape of a conventional slide bead coating device cut in a direction perpendicular to the coating liquid flow direction in a portion where a slit exists, and FIGS. FIG. 4 is a schematic diagram of a cross-sectional shape in which slits 3 a and 3 b in FIG. 3 are cut in a direction orthogonal to the coating liquid flow direction.

  In FIG. 1, the slide surface outflow width L1a of the slit 3a serving as the slit of the first layer is narrower by L2a per one end than the inner surface width L5 of the coating width regulating member 5. Further, the first layer slit 3a has an inclined shape with an inclination amount L3a with respect to the distance of the slit height L4 inside the die, and the slit width decreases from the slit entrance 3ai to the slit exit 3ao. It is. Moreover, the slit 3b which becomes a slit of a 2nd layer is also the same shape.

  On the other hand, in FIG. 2, although the slide surface outflow width L1a of the slit 3a serving as the slit of the first layer is narrower by L2a per one end than the inner surface width L5 of the coating width regulating member 5, the slit width is It is an inclined shape having an inclination of an inclination amount L3a with respect to the distance of the slit height L4 and increasing from the slit inlet 3ai toward the slit outlet 3ao. Further, the slit 3b serving as the second layer slit has the same shape.

  In FIG. 1, in the two-layer simultaneous coating apparatus, an example in which both the slit 3a serving as the first layer slit and the slit 3b serving as the second layer slit correspond to the present invention is shown. The use is not particularly limited, and it may be used only on one side of the first layer or the second layer.

  Further, when used for a plurality of layers, the narrow width L2a and the inclination amount L3a may be different in each layer. Further, the number of simultaneous coating layers of the coating apparatus to which the present invention is applied is not limited, and may be used for a single-layer coating apparatus having only one layer, a two-layer simultaneous coating apparatus, or a three-layer or more simultaneous coating apparatus.

  As described above, to which layer the present invention is used, and the narrow width L2a and the inclination L3a are not particularly limited, and have appropriate values according to the coating conditions, physical properties of the coating liquid, and the like. You can choose.

  However, if the dimension of the narrow width L2a is too large, the edge thin coating tends to be intense, and if it is too small, the edge thick coating tends to become intense. In addition, as a dimension of the inclination amount L3a, when a general slit height L4 is 10 mm or more and 300 mm or less, an appropriate range is 1 mm or more and 100 mm or less.

  Further, other die internal shapes are not particularly limited as long as the present invention is satisfied, and various known shapes may be combined with the inflow port, the cavity, the slit, and the like. Furthermore, the types of webs and coating solutions applicable to the present invention are not particularly limited, and various coating solutions suitable for slide bead coating can be applied.

However, the coating apparatus and the coating method of the present invention exert a remarkable effect on a coating solution having a relatively high viscosity, and are used for coating a coating solution of at least 20 mPa · s, preferably 50 mPa · s or more. Is preferred. The upper limit of the viscosity of the coating solution is not particularly limited as long as it can be applied by slide bead, but is preferably 500 mPa · s or less. Moreover, it is suitable when the coating amount of the coating solution is 60 ml / m ² or more.

  EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited to this.

Example 1
The cross-sectional shape cut in a direction perpendicular to the coating liquid flow direction is the shape shown in FIG. 1, and a slide bead coating device having dimensions shown in Table 1 is used. As a result of simultaneously coating two layers of the coating solution on the resin-coated paper web under the following coating conditions, the coating conditions shown in Table 1 were obtained. In addition, the unit of the numerical value described in Table 1 is all mm.

<Inkjet image-receiving layer coating solution>
Viscosity of first layer coating solution 70 mPa · s
Surface tension of first layer coating solution 30mN / m
Viscosity of second layer coating solution 70 mPa · s
Surface tension of second layer coating solution 30 mN / m

<Application conditions>
Application width 1600mm
Application speed 125m / min
Total application amount 165ml / m ²
First layer application amount 95ml / m ²
Second layer coating amount 70ml / m ²

Comparative Examples 1-3
The cross-sectional shape cut in the direction orthogonal to the coating liquid flow direction is the shape shown in FIG. 2, and the same application as in Example 1 was performed using a slide bead coating device having dimensions shown in Table 1. Table 1 The application status shown in FIG.

  The results of the examples are described in detail below. Example 1 is an inclined shape in which the slide surface outflow width of the slit is narrower than the inner surface width of the coating width regulating member, and the slit width decreases from the slit entrance toward the slit exit inside the die. Therefore, this is an example in which a coating apparatus satisfying claim 1 of the present invention is used.

  On the other hand, in Comparative Example 1, the slide surface outflow width of the slit is narrower than the inner surface width of the coating width regulating member, but in an inclined shape in which the slit width increases from the slit entrance to the slit exit inside the die. Therefore, this is a comparative example when a conventional coating apparatus that does not satisfy the present invention is used.

  In Comparative Example 2, the slide surface outflow width of the slit is narrower than the inner surface width of the coating width regulating member, but the slit width does not increase or decrease from the slit entrance to the slit exit inside the die. That is, it is a comparative example in the case of using a conventional coating apparatus that does not satisfy the present invention because of the shape having no inclination.

  Further, Comparative Example 3 is a comparative example when a conventional coating apparatus that does not satisfy the present invention is used because the slide surface outflow width of the slit is not narrower than the inner surface width of the coating width regulating member.

  In all of Example 1 and Comparative Examples 1 to 3, the flow width of the coating liquid regulated by the inner surface of the coating width regulating member is the same as 1600 mm, and the uniform film thickness width finally obtained as a coating result, Has confirmed the effect of the present invention by relatively comparing the occurrence of edge thick coating.

  Next, the application | coating condition of an Example and each comparative example is demonstrated. The uniform coating film width in Table 1 indicates a width that can be secured as a uniform coated product, excluding non-uniform portions due to edge thick coating and edge thin coating at both ends.

  First, in Example 1, an edge thin coating portion having an extremely narrow width was formed at both ends, but a uniform coating film width of 1560 mm was obtained with respect to a coating width of 1600 mm. Next, in Comparative Example 1, edge thin coating was generated in a wider range than Example 1, and the uniform coating width obtained was reduced to 1520 mm. Further, in Comparative Example 2, although the edge thin coating range slightly decreased and the uniform coating width increased to 1530 mm as compared with Comparative Example 1, it did not reach 1560 mm obtained in Example 1.

  Next, in Comparative Example 3, when exactly the same drying conditions as in Example 1 and Comparative Examples 1 and 2 were used, an undried portion due to edge thick coating was generated, and a process trouble that caused unwinding occurred. The uniform coating width was not evaluated.

  As described above, the coating apparatus and the coating method of the present invention can prevent a process trouble due to edge thick coating, and further have a large effect of suppressing edge thick coating and edge thin coating at both ends, and a wider uniform film than in the past. Thick width was obtained, and it was shown that efficient coating operation with high yield became possible.

Schematic diagram of a cross-sectional shape of the slide bead coating device of the present invention cut in a direction orthogonal to the coating liquid flow direction Schematic diagram of a cross-sectional shape of a conventional slide bead coating device cut in a direction orthogonal to the coating liquid flow direction Schematic diagram of the cross-sectional shape of the slide bead coating device cut along a plane perpendicular to the width Schematic diagram of cross-sectional shape at position B in FIG.

Explanation of symbols

1a, 1b Inlet 2a, 2b Cavity 3a, 3b Slit 3ai, 3bi Slit inlet 3ao, 3bo Slit outlet 4 Slide surface 5 Coating width regulating member L1a Slide surface outflow width of first layer slit L2a First layer slit Narrow width per end L3a Slant amount of first layer slit L1b Sliding surface outflow width of second layer slit L3b Slant amount of second layer slit L4 Slit height

Claims (2)

In the slide bead coating device, the slide surface outflow width of the slit of at least one layer is narrower than the inner surface width of the coating width regulating member on the slide surface, and the slit having the narrow width is provided inside the coating die. In the coating apparatus, the slit width is an inclined shape that decreases toward the slit exit. A coating method, wherein a coating solution having a coating solution viscosity of 50 mPa · s or more is coated on a web by the coating apparatus according to claim 1.

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