JP2005193229A - Coating apparatus and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating apparatus and a coating method for spraying a coating liquid as liquid drops, excellent in spraying uniformity with reduced unevenness such as streak and coating failure. <P>SOLUTION: The coating apparatus comprises a slot nozzle spray device having a coating liquid nozzle for feeding the coating liquid over the application width in the direction crossing the conveyance direction of an object to be coated and a gas nozzle for jetting gas to the vicinity of an open end of the coating liquid nozzle, and coats the coating liquid on the object to be coated by forming the liquid drops by causing the gas to collide against the coating liquid. The slot nozzle sprayer has a pair of inner die blocks and outer die blocks placed outside of the inner die blocks. The coating liquid nozzle is formed between the two inner die blocks, and the gas nozzle is formed between the inner die blocks and the outer die blocks. The angle β formed between the coating liquid outlet of the coating liquid nozzle and the gas outlet of the gas nozzle is 15 degrees or more and 60 degrees or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating apparatus and a coating method for coating by spraying a coating liquid as droplets.

  Conventionally, there is a demand for a coating method in which a thin film is provided with high accuracy in coating film thickness, low drying load, and high productivity.

  There are various coating products that require a thin film having a uniform coating thickness with high accuracy to be provided on the structure, and examples thereof include a void-type inkjet recording medium for inkjet as described below.

  The void-type ink jet recording medium is preferably used for an output that requires a high quality texture such as a silver salt photograph such as glossiness, glossiness, and depth in an ink jet recording method, and is non-water-absorbing like a resin-coated paper or a polyester film. A porous ink absorbing layer that forms a fine void structure mainly with a hydrophilic binder and fine particles as an ink absorbing layer is formed on the porous substrate, and the ink is absorbed into the void portion. As the fine particles, inorganic or organic fine particles are known, but in general, inorganic fine particles that can obtain higher gloss with fine particles are used.

  For the porous ink absorbing layer, 1) stable fine particles of about 0.1 μm or less that form a porous layer for achieving high color developability and gloss, 2) high retention of fine particles, and Low swellable hydrophilic binder to prevent ink absorption rate from decreasing, 3) Hydrophilic binder cross-linking agent to improve ink absorption rate and water resistance of the coating, 4) To achieve optimum dot diameter on the surface Distributed surfactants and hydrophilic polymers, 5) Cationic fixing agents to improve dye image bleeding and water resistance, polyvalent metal compounds, 6) Color fading due to light and oxidizing gas of dye images Anti-fading agent for improvement, 7) fluorescent whitening agent and color tone adjusting agent (redness agent, bluing agent, etc.) for improving white background, 8) matting agent and slip agent for improving surface slipperiness, 9) Flexibility of the porous ink absorbing layer 10) Various inorganic salts (polyvalent metal salts) for improving bleeding of dye images, water resistance or weather resistance, 11) Porous ink absorption The use of various additives such as acids and alkalis for adjusting the film surface pH of the layer has been proposed.

  However, when each of the above additives is added to the coating liquid for forming the porous ink absorbing layer, the selection and use of materials are used in many additives from the viewpoint of the stability of the manufacturing process such as avoiding aggregation of fine particles. There are many cases that are subject to various restrictions such as quantity.

  Therefore, the coating solution for forming the porous ink absorption layer does not contain the additive subject to the above-mentioned restriction, but the coating solution is first applied as a constituent layer on the substrate, and the additive is contained before the rate-decreasing drying. A method of overcoating the coating liquid on the upper part of the constituent layer and a method of overcoating the additive-containing solution online after the moisture content of the constituent layer coating film becomes less than the void volume of the porous layer after drying. Proposed. The additive contained in the coating liquid for the overcoat layer is expected to act as a functional compound that appropriately permeates into a constituent layer provided in advance and imparts a preferable function. Originally, the purpose is to impregnate the porous ink absorption layer with the functional compound, so the overcoat layer itself may be very thin. Moreover, it is preferable that it is a very thin layer.

  As a method for coating such an overcoat layer with a uniform thin film, the present applicant uses a slot nozzle spray device to spray the coating liquid on the coated body as droplets and the manufacturing conditions of the inkjet recording paper. Details were proposed (for example, see Patent Documents 1 to 4).

However, as a result of further investigation, spraying the coating liquid onto the coated body as droplets is effective for extremely reducing the coating film thickness. It was found that streaking along the surface, point-like failure defects, and spotted coating unevenness occurred.
Japanese Patent Laid-Open No. 2004-906 JP 2004-90330 A JP 2004-106378 A JP 2004-106379 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a coating apparatus and a coating method for spraying and coating a coating liquid having excellent coating uniformity with reduced unevenness and coating failure. It is to be.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
The coating apparatus, wherein an angle β formed by the coating liquid discharge port of the coating liquid nozzle and the gas discharge port of the gas nozzle is 15 degrees or more and 60 degrees or less.

(Claim 2)
A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
The coating apparatus, wherein an angle α formed by the bottom surfaces of the pair of external die blocks at positions facing the coated body is 170 degrees or more and 240 degrees or less.

(Claim 3)
A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
A pair of external dies having a width L1 and a width L2 of 1 mm or less of each of the bottom surfaces of the pair of internal die blocks at positions facing the object to be coated, and at positions facing the object to be coated Each of the widths L3 and L4 of the bottom surface of the block is 0.1 to 50 mm.

(Claim 4)
The absolute value of the difference ΔL between the distance L5 between the bottom surface of the outer die block and the surface of the object to be coated and the distance L6 between the bottom surface of the inner die block and the surface of the object to be coated is 2 mm or less. The coating apparatus of any one of 1-3.

(Claim 5)
5. The ink jet recording sheet according to claim 1, wherein the substrate is an ink jet recording sheet having an ink absorbing layer on a substrate, and the coating liquid contains a function-imparting compound for the ink absorbing layer. The coating apparatus of any one of Claims.

(Claim 6)
6. The function-imparting compound is at least one selected from a pH adjuster, a surfactant, a hydrophilic binder crosslinking agent, an image stabilizer, and a water-soluble polyvalent metal compound. Coating device.

(Claim 7)
The coating method characterized by performing application | coating on a to-be-coated body using the coating device of any one of Claims 1-6.

  ADVANTAGE OF THE INVENTION According to this invention, a coating apparatus and the coating method which spray and apply | coat the coating liquid excellent in the uniformity of application | coating with the smoothing and the coating failure reduced as a droplet can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The present inventor believes that the streak-like, spot-like failure defect, and spot-like coating unevenness depend on the change in the landing rate and the state of micronization due to the application liquid adhering to the slot nozzle spray part, and this As a result of a detailed study of the coater constituting the slot nozzle spray device in order to realize stable coating in the method, it was found that the shape of the coater part constituting the slot nozzle spray device has a great influence.

  That is, the present inventor, regarding the shape of the coater part constituting the slot nozzle spray device, the angle between the coating liquid discharge port and the gas discharge port, the angle of the external die block constituting the gas discharge port, the coating liquid discharge port and the gas By designing the distance to the discharge port, the width of the external die block, etc. under the optimum conditions, it is possible to prevent the coating liquid from adhering and insufficient fine particles, and to stably spray coating droplets. As soon as it has been found that uneven coating is reduced, the present invention has been achieved.

  Details of the present invention will be described below.

  First, the details of the slot nozzle spray device which is the coating device of the present invention will be described with reference to the drawings. However, the coating apparatus of this invention is not limited only to the structure shown with the figure illustrated here.

  The coating method of the present invention includes a coating liquid nozzle that transports an object to be coated and supplies a coating liquid over a coating width in a direction that intersects the transport direction of the body to be coated, and an opening end of the coating liquid nozzle. Then, using a slot nozzle spray device having a gas nozzle for jetting gas, the coating liquid is applied onto the object to be coated by spraying the gas by colliding with the coating liquid to form droplets.

  The object to be coated here refers to an object to be coated by applying a coating liquid in the form of droplets using the coating method of the present invention, and the form is not limited. It is preferable that the ink-jet recording sheet has a long band-shaped support or a constituent layer such as an ink absorbing layer on the band-shaped support because the effect of the present invention can be sufficiently obtained, but is not limited thereto. It is not a thing. The coated body may be a plate-like support or a three-dimensional shape as long as the coated portion has an area.

  Moreover, in this invention, a to-be-coated body is moved (conveyed) relatively with respect to the coating liquid nozzle of a coating device, and performs coating manufacture continuously. The coating liquid nozzle of the coating device has a length corresponding to at least the coating width of the coated body (refers to the length of the coated portion of the coated body in a direction intersecting the transport direction of the coated body). And by arrange | positioning so that it may cross | intersect the conveyance direction of a to-be-coated body, a coating liquid is apply | coated on a to-be-coated body only by conveying a to-be-coated body with respect to a coating device. When the object to be coated is a long belt-like support, the belt-like support itself is transported in the longitudinal direction of the belt-like support, and the coating liquid nozzle of the coating device is placed in the width direction of the belt-like support (perpendicular to the longitudinal direction). Preferably in the direction of An extremely thin coating film can be applied with high film thickness uniformity without a drying load by conveying the object to be coated in one direction to the coating apparatus and spraying the coating liquid as droplets over the coating width.

In addition, the droplets sprayed from the coating liquid nozzle of the coating device, in the coating width direction,
1: the droplet size distribution is uniform,
2: The area range in which the droplets fall on the substrate is uniform in the transport direction drop length (L7 in FIG. 3).
3: The spread angle falling on the coated body is uniform,
4: The collision speed falling on the coated body is uniform,
Thus, it is possible to ensure more uniform coating film thickness.

  That the droplet diameter distribution is uniform in the coating width direction specifically means that the variation of the average droplet diameter is ± 20% or less in the coating width direction. More preferably, it is ± 10% or less.

  The variation of the average droplet diameter can be measured and calculated using a laser diffraction particle size distribution measuring apparatus. Specifically, the following measurement method is used.

  First, the coating liquid is sprayed from a spray device such as a slot nozzle spray device that sprays the coating liquid as droplets, and the spray state is stabilized. Immediately after the start of spraying, the discharge amount of the coating liquid and the gas pressure are not constant, and the spray state is not stable. Therefore, it can be stabilized by continuing spraying for a predetermined time.

  Next, spray droplet RTS5123 (manufactured by Malvern Co., Ltd.) is used as a laser diffraction particle size distribution measuring device for the droplet group in which the spray state is stable, and the average droplet diameter is measured at five locations at equal intervals in the coating width direction. . At both ends (application ends) of the droplet width falling on the substrate to be coated, the spray concentration is usually extremely low, so that the effective coating width is not counted. Therefore, the both ends of the effective coating width are the two ends of the measurement point. Specifically, two points at both ends of the measurement point are 1 cm inside from the coating end, and three points at equal intervals inside are added to obtain a total of five points, which are used as measurement points. The variation rate is calculated from the average droplet diameter measured at these five locations.

  The average droplet diameter can be easily measured by using a spray tech RTS5123. However, when each droplet diameter of the droplet group at the measurement location is measured and the droplet diameter is plotted on the horizontal axis, This refers to the droplet diameter at 50%.

  In addition, that the length in the transport direction of the area range in which the droplets fall on the coated body is uniform means that the variation in the length in the coating width direction is ± 10% or less. More preferably, it is ± 5% or less.

  Further, the spread angle of the liquid droplets falling on the coated body is uniform, the fluctuation of the falling angle of the liquid droplets falling on the coated body in the coating width direction with the coating liquid nozzle of the coating device as a base point, It means ± 10% or less. More preferably, it is ± 5% or less.

  Moreover, in order for the collision speed falling on a to-be-coated body to be uniform, the spray speed of the atomized coating liquid should just be uniform.

  In order to achieve uniform spraying as described above, the present invention is characterized by the use of a slot nozzle spray device. The slot nozzle spray device has a plurality of coating liquid nozzle holes for discharging the coating liquid in the coating width direction. The coating solution nozzle holes may be arranged in a line in the coating width direction or in a staggered manner. And a gas nozzle hole for ejecting gas in the vicinity of the coating liquid nozzle hole, and a mechanism for colliding the gas ejected from the nozzle with the coating liquid ejected from the coating liquid nozzle hole to form a droplet. Have.

  As a slot nozzle spray device that can be preferably used in the present invention, for example, a device described in JP-A-6-170308 can be applied. Japanese Patent Laid-Open No. 6-170308 discloses an example in which an adhesive for disposable diapers is applied onto a fiber using this slot nozzle spray device. However, an extremely high viscosity coating liquid (adhesive) is applied to the slot nozzle. It is dropped in a fiber form from a coating liquid nozzle (coating liquid discharge portion) of the spray device, and the coating apparatus and the object to be coated (fiber) are connected by the fiber-shaped coating liquid. That is, unlike the coating method of the present invention, it is not applied as a discontinuous droplet on the object to be coated. The fiber-like coating liquid falling in parallel from each of the plurality of coating liquid nozzles provided over the coating width is disturbed by the gas ejected from the gas nozzle provided in the vicinity of the coating liquid nozzle, preventing vertical drop. And only land randomly within a certain area on the coated body. Without the gas nozzle, the fiber-like coating liquid falls vertically as it is, but by spraying the gas from the gas nozzle, it is possible to disperse and land the coating liquid over a wider range, The coating layer is simply spread and placed, and is not a coating that requires strictly uniform coating film thickness over the entire surface of the coated body as described in the example of the ink jet recording paper. Further, since the adhesive is applied, the formed coating film is extremely thick.

  Further, a slot nozzle spray coating apparatus disclosed in JP-A-5-309310 can also be preferably used in the present invention. In the example disclosed in Japanese Patent Laid-Open No. 5-309310, a hot melt type adhesive is applied onto an object to be coated, as in the above-mentioned Japanese Patent Laid-Open No. 6-170308. Since this is also a very high viscosity coating liquid (adhesive), it is a method of continuously discharging the coating liquid to the surface of the coated body in the form of fibers, and there is no strict film thickness uniformity. The coating film to be formed is also very thick.

  As described above, using such a slot nozzle spray device to increase the uniformity of the spray state over the coating width, the viscosity of the coating solution is relatively low, and the gas pressure ejected from the gas nozzle is increased. Is possible. Further, the uniformity of spraying can be enhanced by reducing the area of the opening end of the coating liquid nozzle of the slot nozzle spray device, or by reducing the pitch of the opening end.

  The viscosity of the coating solution is preferably 0.1 to 250 mPa · s, more preferably 0.1 to 50 mPa · s, and still more preferably 0.1 to 20 mPa · s. By applying to a slot nozzle spray device, it is possible to spray droplets uniformly over the coating width.

  In order to spray droplets uniformly over the coating width, the surface tension of the coating solution is adjusted to 20 to 70 mN / m, preferably 20 to 50 mN / m, more preferably 20 to 30 mN / m. That is.

  Further, when the gas internal pressure is 10 kPa or more, preferably 20 kPa or more, and more preferably 50 kPa or more when a gas is collided with the coating liquid to form a droplet using a slot nozzle spray device or the like, uniform spraying is performed. easy. The gas flow rate is 3.5 CMM / m or more, preferably 7 CMM / m or more, and more preferably 10 CMM / m or more.

  By using the above-mentioned means, the coating liquid can be uniformly supplied onto the object to be coated even if the amount of the coating liquid is small by scattering in the form of discontinuous droplets instead of continuous fibers over the coating width. . As a result, the coating film thickness can be made uniform. In addition, since discontinuous droplets are supplied onto the object to be coated and the amount of the coating liquid is reduced, no drying load is applied.

  Next, a specific form of the slot nozzle spray coating apparatus used in the coating apparatus of the present invention will be described.

  FIG. 1 is a schematic view for explaining the coating method of the present invention. In the figure, reference numeral 1 is a slot nozzle spray portion of a slot nozzle spray device (the whole is not shown), and 9 is a long belt-like support-type coated body.

  The slot nozzle spray unit 1 includes a pair of internal die blocks 3a and 3b and external die blocks 2a and 2b on the outside of the pair of internal die blocks 3a and 3b. The coating liquid nozzle C is formed in the gas nozzle D between the internal die block 3a and the external die block 2a, and between the internal die block 3b and the external die block 2b.

  The coated body 9 is transported at a constant speed by a transport means (not shown) in the transport direction indicated by the arrow in the drawing, which is the longitudinal direction of the coated body 9. The coating liquid nozzle C of the slot nozzle spray unit 1 has a length in the width direction of the object 9 to be applied, which is a direction orthogonal to the transport direction, and is disposed so as to face the application surface of the object 9 to be applied. Yes. The coating liquid is sprayed in the form of droplets from the coating liquid nozzle C, and the coating is performed by landing the droplets on the object 9 to be transported. At this time, the length to which the coating solution in the width direction of the substrate 9 is applied corresponds to the coating width indicated by the arrow in the figure. In FIG. 1, the application width is shorter than the length in the width direction of the article 9 to be applied, but it may of course be the same.

  FIG. 2 is a schematic cross-sectional view showing an example of a slot nozzle spray device including the slot nozzle spray unit described in FIG.

  In FIG. 2, the slot nozzle spray unit 1 has a pair of gas nozzles D having a gas pocket A and a coating liquid nozzle C having a coating liquid pocket B. The coating liquid has a viscosity (preferably 0.1 to 250 mPa · s) that can form droplets without forming a fiber shape. For example, a coating liquid such as a function-imparting compound-containing solution is placed in the preparation kettle 4, and the pump 5 and the flow meter 6 is supplied to the coating liquid pocket B and guided to the coating liquid nozzle 3. On the other hand, pressurized air is supplied from the pressurized air source 7 to the gas pocket A via the valve 8 to the gas nozzle 2. At the time of application, the application liquid is supplied from the preparation kettle 4 so that the specified application amount is applied from the application liquid nozzle C, and at the same time, pressurized air is sprayed from the pair of gas nozzles D to form the application liquid in the form of droplets. It is sprayed and deposited on the body 9. In the coating method of the present invention, it is a great feature that the coating liquid can be sprayed as fine droplets instead of fibers. By supplying the coating liquid as fine droplets onto the surface of the object 9 to be coated, a highly uniform thin film can be formed at high speed without a drying load.

  Next, with reference to FIG. 3, the slot nozzle spray section and the formation and flying state of the droplets formed there will be described.

  In FIG. 3, the coating liquid E discharged from the coating liquid nozzle C is subdivided into droplets by a compressed air G supplied from a gas nozzle D provided close to both sides of the coating liquid nozzle C. Droplet particles 12 that are close to each other, fly, and land uniformly on the surface of the object 9 across the gap L5. In FIG. 3, the substrate 9 is shown as a model in which the ink absorbing layer 11 is applied as a constituent layer on the substrate 10. The area range of the droplets 12 of the coating liquid landing on the substrate 9 is preferably always uniform, but in particular, the drop length in the transport direction (denoted by the drop length L7 in the figure) is applied. Preferably it is uniform across the width. Further, it is preferable that the spread angle θ of the droplet group sprayed on the object to be coated with the opening end of the coating liquid nozzle C as a base point is uniform over the coating width.

  FIG. 4 is a schematic sectional view showing the characteristics of the configuration of the slot nozzle spray section used in the present invention.

  In FIG. 4, a coating liquid nozzle C configured between the internal die blocks 3a and 3b, a gas nozzle D configured between the internal die block 3a and the external die block 2a, and between the internal die block 3b and the external die block 2b, One of the characteristics is that the angle β formed by is 15 degrees or more and 60 degrees or less. Specifically, in many cases, the coating liquid nozzle C is often arranged perpendicular to the surface of the object to be coated. In this case, the gas nozzle D has an inclination angle of 15 degrees or more and 60 degrees or less with respect to the vertical direction. Will be arranged. In this way, by disposing the coating liquid nozzle C and the gas nozzle D at a specific angle, it is possible to stably form droplets of the coating liquid, reduce unevenness and coating failure, and achieve high coating uniformity. It is possible to realize the coating having.

  In the coating apparatus of the present invention, the angle α formed by the bottom surfaces of the pair of external die blocks at positions facing the object to be coated is 170 degrees or more and 240 degrees or less.

  In FIG. 4 described above, when the bottom surfaces of the external die blocks 2a and 2b facing the substrate 9 are 2c and 2d, the angle α formed between the bottom surface 2c and the bottom surface 2d is 170 degrees or more, 240 Less than or equal to degrees. FIG. 4 illustrates a state in which each bottom surface 2c, 2d is positioned horizontally with respect to the object 9 and the angle α is 180 degrees. However, as shown in FIG. The bottom surfaces 2c and 2d may be formed in a state where the bottom surfaces 2c and 2d are inclined with respect to the article 9 to be coated.

  In this way, by arranging the bottom surfaces of a pair of external die blocks at positions facing the substrate to be coated at a specific angle, it becomes possible to form droplets of a stable coating liquid, and to prevent unevenness and coating failure. Reduction and high application uniformity can be realized.

  In the coating apparatus of the present invention, the widths L1 and L2 of the bottom surfaces of the pair of internal die blocks at positions facing the object to be coated are 1 mm or less and positions facing the object to be coated. Each of the widths L3 and L4 of the bottom surfaces of the pair of external die blocks is 0.1 to 50 mm.

  That is, in FIG. 4, when the bottom surfaces of the internal die blocks 3a and 3b facing the coated body 9 are 3c and 3d, the widths L1 and L2 of the bottom surfaces 3c and 3d are 1 mm or less. And is preferably 0.2 to 1.0 mm.

  Further, when the bottom surfaces of the external die blocks 2a and 2b facing the coated body 9 are 2c and 2d, the widths L3 and L4 of the bottom surfaces 2c and 2d are 0.1 to 50 mm. And preferably 0.1 to 30 mm.

  The shapes of the bottom surfaces 3c and 3d of the internal die blocks 3a and 3b according to the present invention may be configured in a horizontal state with respect to the object 9 as shown in FIG. 4, or as shown in FIG. Moreover, you may have a curved form. In the case of the curved shape shown in FIG. 6, the widths L1 and L2 defined in the present invention are defined as the widths of the contact points of the inclined surfaces and the tip portions of the vertical surfaces.

  Moreover, as the shape of the bottom surfaces 2c and 2d of the external die blocks 2a and 2b according to the present invention, even if the entire bottom surface is configured to be horizontal with respect to the substrate 9 as shown in FIG. As shown in FIG. 7, a part adjacent to the coating liquid nozzle C and the gas nozzle D may be protruded, and the bottom surfaces 2 c and 2 d may be formed in that region. In this way, by arranging the width of the bottom surface of the internal block or external die block facing the object to be coated under specific conditions, it is possible to stably form droplets of the coating liquid, and to prevent unevenness and coating failure. Reduction and high application uniformity can be realized.

  In the coating apparatus of the present invention, the difference ΔL between the distance L5 between the bottom surface of the external die block and the surface of the object to be coated and the distance L6 between the bottom surface of the internal die block and the surface of the material to be coated may be 2 mm or less. Preferably, it is 0.1-2 mm.

  FIG. 8 is a schematic sectional view showing another example of the feature of the configuration of the slot nozzle spray section used in the present invention.

  In FIG. 8, the distance between the bottom surfaces 3c, 3d of the inner die blocks 3a, 3b facing the substrate 9 and the outermost surface of the substrate is L6, and the outer die blocks 2a, 2b are covered. When the distance between the bottom surface 2c, 2d at the position facing the application body 9 and the outermost surface of the application body is L5, the absolute value of the difference ΔL (L5-L6) is 2 mm or less. It means that there is. Note that the outermost surface of the coated body in the present invention means, for example, the outermost surface of the ink absorbing layer 11 in an ink jet recording sheet coated with the ink absorbing layer 11 as a constituent layer on the substrate 10. As described above, the difference ΔL between the distance between the bottom surface of the external die block and the surface of the object to be coated and the distance between the bottom surface of the internal die block and the surface of the material to be coated is set as a specific condition. It becomes possible to form, and unevenness and coating failure are reduced, and coating with high coating uniformity can be realized.

  9 and 10 are schematic views of the slot nozzle spray portion of FIG. 2 as viewed from the coating liquid nozzle C side. An opening end of a plurality of coating liquid nozzles C and an opening end of a gas nozzle D arranged in the coating width direction are shown.

  In the coating liquid nozzle shown in FIG. 9, 21 coating liquid nozzles C each having a circular opening end are arranged in the coating width direction. And it is the aspect in which the gas nozzle D is provided adjacent to both sides of the opening end of each coating liquid nozzle C. The coating liquid nozzles C are arranged at equal intervals, and similarly, the gas nozzles D are also arranged at equal intervals. Here, two gas nozzles D corresponding to one coating liquid nozzle C are arranged in a straight line in a direction perpendicular to the coating width direction. However, the coating liquid nozzle C and the gas nozzle D are staggered alternately. It may be arranged. It is preferable that the interval (pitch) between the opening end of the coating liquid nozzle C or the opening end of the gas nozzle D is constant.

  The coating liquid nozzle shown in FIG. 10 is different from the form shown in FIG. Eleven coating liquid nozzles C having rectangular opening ends are arranged in the coating width direction. A slit-like gas nozzle D is provided for each of the coating liquid nozzles C over the coating width in the vicinity of both sides of the opening end. Also in this embodiment, the openings of the plurality of rectangular coating liquid nozzles are arranged at equal intervals.

  FIG. 11 is an exploded perspective view of a slot nozzle spray unit having a coating liquid nozzle of the type shown in FIG. In the figure, reference numerals 3a and 3b are internal die blocks for forming a coating liquid slit having a predetermined distance and causing the coating liquid to flow down the slit. One die block 3 a has a coating liquid supply pipe 61 that receives a coating liquid supplied from a coating liquid supply source (not shown) and communicates with the coating liquid pocket B. The coating liquid staying in the coating liquid pocket B flows down through the coating liquid slit formed between the internal die blocks 3a and 3b. Reference numeral 1d denotes a shim (padding) sandwiched between the inner blocks 3a and 3b. The coating liquid slit formed in the gap between the two inner die blocks 3a and 3b is divided in the vertical direction to form a plurality of slits in the coating width direction. The coating liquid nozzle is formed.

  Reference numerals 2a and 2b denote gas supply external die blocks that form gas nozzles D (not shown) through which compressed gas flows in the gaps between the external die blocks 2a and 2b. The gas nozzle D in this case is a slit extending in the coating width direction. Compressed air is supplied from an air supply source (not shown) to each air supply pipe 81 of each of the external die blocks 2a and 2b and stays in the gas pocket A, and then formed in a gap between the internal die block and the external die block. The gas nozzle D (not shown) flows down with pressure.

  The coating liquid flowing down between the shims 1d and the compressed air flowing down the two gas nozzles collide with each other at the coating liquid nozzle at the bottom of the slot nozzle spray unit 1 to form droplets, and the object to be coated It flies over the object to be coated.

  In the slot nozzle spray device used in the present invention, the shape of the opening end of the coating liquid nozzle may be circular or rectangular, and the size can be used in the range of 50 to 300 μm, and the pitch (interval) thereof is 100 to 3000 μm is preferable. On the other hand, the shape of the opening end of the gas nozzle may be a circle or a slit extending to the coating width, and the diameter in this circle (d shown in FIG. 9) or the slit interval (w shown in FIG. 10) It can be used in the range of about 50 to 500 μm. The angle of the gas nozzle with respect to the coating solution nozzle is characterized by being in the range of 15 to 60 degrees, and preferably 15 to 45 degrees. Further, the distance between the coating liquid nozzle of the slot nozzle spray section and the coated body (L5 shown in FIG. 2) is preferably in the range of about 0.2 to 10 cm, more preferably 0.5 to 6.0 cm. More preferably, it is 1.0-3.5 cm.

Although the supply amount of the coating liquid from the coating liquid nozzle cannot be defined unconditionally depending on the desired coating film thickness, coating liquid concentration, coating speed, etc., the coating amount on the coated body is generally 1 to 50 g / m. A range of ² is preferred. If it is less than 1 g / m ^2, it is difficult to form a stable and uniform coating film. Conversely, if it exceeds 50 g / m ² , the drying load will be affected, making it difficult to exhibit the effects of the present invention effectively. . The wet film thickness of the coating solution is 1 to 50 μm, and preferably 5 to 30 μm.

  On the other hand, the gas ejected from the gas nozzle may be any gas suitable for application, and generally air (air) is used, but the gas supply condition is generally 1 to 50 CMM / m (flow rate per application width). The internal pressure at the gas nozzle at that time is preferably 10 kPa or more from the viewpoint of coating uniformity.

  The air linear velocity v is preferably 100 to 400 m / s from the viewpoint that the object of the present invention can be remarkably achieved. In particular, if v is 100 m / s or more, it is preferable from the viewpoint of coating dryness, and if it is 400 m / s or less, it is preferable from the viewpoint of coating yield.

  The air linear velocity referred to in the present invention is an air linear velocity immediately after the gas nozzle exit, and can be determined by measuring with a laser Doppler anemometer, for example, 1D FLV system 8851 manufactured by KANOMAX. Further, the coating yield is the amount of coating liquid applied on the substrate to be coated / the total amount of coating liquid supplied × 100 (%), and is calculated by a mass method. That is, the amount of coating liquid applied on the coated body is calculated from the change in mass before and after coating on the coated body, and the total amount of coating liquid fed is fed to the coating liquid nozzle and supplied mass, that is, It can be determined from the liquid feed flow rate x the coating time.

  In this case, the average particle diameter of the droplets of the coating liquid is preferably 10 to 70 μm from the viewpoint that the object of the present invention can be remarkably achieved. The average particle size of the droplets referred to in the present invention is the average particle size at the position of the application gap (distance L5 between the application liquid nozzle and the object to be applied), and is a laser diffraction type particle size measuring device such as manufactured by MALVAN. It can be determined by measuring with RTS114.

  FIG. 12 shows an example of a coating production line in which the slot nozzle spray device as described above is arranged. In this case, the object to be coated is one in which a constituent layer is coated on a support. A plurality of (multi-stage) slot nozzle spray devices were arranged in the step of drying after applying the constituent layers. Thus, on the same line, forming the constituent layers and applying the overcoat layer (outermost layer) according to the present invention is called online coating.

  A porous material supplied from the flow-regulating slide bead coating device 20 in the process of passing the support roller 21 from the original winding of the support by a transport means (not shown) and further reversely transporting at the position of the backup roll 22. A coating liquid for the quality ink absorbing layer (constituting layer) is applied. Since the coating liquid for the porous ink absorbing layer contains a hydrophilic binder, it is cooled once in the cooling zone 30 and fixed. The to-be-coated body 9 having a constituent layer on the support is conveyed to a drying process. In the drying process, a reverser 23 that blows air and reversely conveys the coating film surface in a non-contact manner and a normal conveyance roller 24 that reversely conveys the reverse surface of the coated object 9 are provided alternately. Is meandering. In this drying step, hot air is blown to dry (the hot air blowing means is not shown). In the course of this drying process, preferably at the position after the reduced rate drying, application by droplet spraying as described above of the present invention is performed by the two slot nozzle spray devices 1. Of the two slot nozzle sprays, at least one is preferably placed at a position after the drying end point from the viewpoint of drying properties. In this example, two slot nozzle spray devices are used, but one or of course three or more nozzles may be used. It was found that application by droplet spraying in multiple stages reduces the drying load and at the same time increases the film thickness uniformity.

  Using the coating method of the present invention, the coating speed when forming a thin film on an object to be coated varies depending on the type, concentration, solvent content, drying ability, etc. of the coating solution to be used. Although not possible, the coating speed is preferably 50 to 500 m / min, more preferably 100 to 300 m / min.

  As a coating time when coating is performed on an object to be coated having at least one component layer on the support using the coating method of the present invention, the component layer formed on the support is subjected to reduction rate drying or later. Preferably, after the end point of drying. Moreover, it is preferable that the coating process performed by using the slide nozzle coating and the like and the coating process performed by using the slot nozzle spray device of the present invention are continuously performed on the same production line (online coating and say). Since the coating method according to the present invention can be applied even with a small amount of a coating solution, even if it is performed in a state where the constituent layer is not completely dried, the drying load is small, and there is also an adverse effect on the constituent layer. Few. It has also been found that the application of the present invention before the constituent layer is completely dried can prevent the disadvantages such as cracking of the constituent layer.

  Since the coating method of the present invention has a small drying load, it can be carried out in the drying step of the constituent layers. In the drying step, it is usually preferable to dry the coating film in a wet state by blowing dry air controlled to a specific temperature and humidity condition from the front surface or the back surface thereof while continuously conveying the coating film.

  The drying process of the wet coating film can be classified mainly as follows. In the initial stage of drying, it is called a constant rate drying section, and water and solvent, which are solvents of the coating solution, evaporate while taking away latent heat of evaporation, so that the surface temperature of the constituent layers is almost constant. This period of constant temperature is called a constant rate drying section. After the constant rate drying section, the water and the solvent that interact with the solute of the coating solution are evaporated, so that energy for solving the interaction is required in addition to the latent heat of vaporization, so that the surface temperature rises. This period is referred to as a reduced rate drying unit. Decreasing drying is a phenomenon that occurs when the evaporation of the solvent from the surface excels the moisture transfer in the coating film in the layer. Next, when the reduction rate drying is completed, a region where the temperature of the drying air coincides with the surface temperature of the inkjet recording paper is entered. This point is called the drying end point.

  The confirmation method of the constant rate drying unit, the reduction rate drying unit, and the drying end point described above is not particularly limited. For example, the surface temperature is monitored, and the region where the surface temperature is constant is defined as the constant rate drying unit, the surface The point in time when the temperature rising region becomes the same as the reduction rate drying unit and the drying temperature can be obtained as the drying end point.

  As another method, a water content meter can be installed in each region, the water content of the coating film can be monitored, and the region where the water content decrease curve becomes flat can be defined as the drying end point.

  The viscosity of the coating solution in the coating method of the present invention is preferably 0.1 to 250 mPa · s. More preferably, it is 0.1-50 mPa * s. More preferably, it is 0.1-20 mPa * s.

  The coating method of the present invention can form a thin layer uniformly and can be applied to a wide range of fields, for example, formation of an antireflection film that imparts a functional layer to the outermost surface of a general silver salt photosensitive material, Although it can be used for the application of a charge generation layer, a charge transport layer, and application on an inkjet recording paper of a photoreceptor used in electrophotography, it is particularly preferably applied to application of an overcoat layer on an inkjet recording paper. It is.

  An inkjet recording paper to which the coating method of the present invention can be preferably applied has a porous ink absorbing layer containing a hydrophilic binder and fine particles as a constituent layer on a support, and an overcoat layer formed thereon by the coating method of the present invention. Is provided.

  The porous ink absorbing layer is mainly formed from fine particles and a hydrophilic binder. As the fine particles, fine particle silica synthesized by a vapor phase method is preferably used, and as the hydrophilic binder, polyvinyl alcohol or the like is preferably used.

  As the support used for such an ink jet recording paper, a water-absorbing support (for example, paper) or a non-water-absorbing support can be used. From the viewpoint of obtaining a higher-quality print, An ionic support is preferred. As such a support, there is a paper support in which both sides of paper are laminated with a polyolefin resin.

  The coating liquid for the porous ink absorption layer (for the constituent layer) containing the polyvinyl alcohol and fine particle silica tends to be low viscosity at high temperature and high viscosity at low temperature. Therefore, after coating the water-soluble coating liquid on the support, it is preferable to cool the coating liquid and increase the viscosity significantly.

  The coating temperature of the porous ink absorbing layer is generally 30 to 60 ° C., and the cooling temperature after coating may be such that the coating film temperature is approximately 20 ° C. or less, and particularly 15 ° C. or less. It is preferable to do.

  The cooling step can be performed by passing a zone cooled to, for example, 15 ° C. or lower after the coating for a certain period of time (preferably 5 seconds or more). At the time of cooling, it is preferable not to blow too strong wind from the viewpoint of obtaining a uniform and uniform coating without causing liquid twist.

  Once cooled, even if a strong wind is blown, the coating liquid itself is thickened, so that the liquid twist is less likely to occur, and the generation of the liquid twist can be suppressed even if the strong wind is blown. Moreover, although the temperature of the strong wind to blow can blow the wind of 20 degreeC or more, it is preferable to raise the temperature of a wind gradually.

  The drying step after applying the coating liquid for the porous ink absorbing layer on the support is performed by blowing air, passing through a zone in a high temperature state, or using both in combination.

  When drying by passing through a high temperature zone, it passes through a drying zone of 50 to 150 ° C. At this time, it is preferable to select an appropriate drying temperature in consideration of the heat resistance of the support and the adverse effect on the coating film. The drying wind is usually carried out with a relative humidity of 10 to 50%, preferably 15 to 40%. Although depending on the wet film thickness, the drying time is preferably within about 10 minutes, and particularly preferably within 5 minutes.

  The coating speed depends on the wet film thickness and the drying capacity of the equipment, but is generally 10 to 1000 m per minute, preferably 20 to 500 m.

  The method for applying the coating liquid for the porous ink absorbing layer can be appropriately selected from known methods, for example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, extrusion coating. The extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

  Next, the coating liquid for the overcoat layer when the overcoat layer is provided on the porous ink absorbing layer of the inkjet recording paper using the slot nozzle spray device of the present invention will be described below.

  The coating liquid for the overcoat layer is characterized by containing a function-imparting compound for the surface of the constituent layer of the ink jet recording paper.

  Organic or inorganic acids whose pH changes depending on the use of the function-imparting compound, or various alkaline additives, water-soluble salts of water-soluble polyvalent metal ions, various anionic, cationic, amphoteric or nonionic surface activity Agents, anti-fading agents, cationic fixing agents, crosslinking agents for hydrophilic binders, and the like.

  Examples of acids that can be used for the purpose of lowering the film surface pH of the porous ink absorbing layer include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, formic acid, acetic acid, phthalic acid, succinic acid, oxalic acid, poly Mention may be made of organic acids such as acrylic acid.

  Examples of the alkali used for the purpose of increasing the film surface pH of the porous ink absorption layer include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, borax, sodium phosphate, calcium hydroxide, and organic amine. Is mentioned.

  The pH adjusting agent is particularly preferred when the pH in the coating solution for forming a porous film is different from the preferred film surface pH of the recording medium.

  The film surface pH of the porous ink absorbing layer of the recording medium varies depending on the type of ink, but generally the water resistance and bleeding of the dye are improved on the acidic side, but the light resistance is improved on the higher pH side. Therefore, the optimum pH is selected in combination with the ink to be used. The membrane surface pH of the porous surface is preferably 3 to 7, and particularly preferably 3.5 to 6.5. The film surface pH referred to here is J.I. It is a value measured in accordance with the paper surface pH measurement method specified in TAPPI 49. Specifically, 50 μl of pure water (pH = 6.2 to 7.3) is dropped onto the surface of the recording medium, and is commercially available. The value measured using a plane electrode.

  The function-imparting compound may be a surfactant.

The surfactant can control the dot diameter during ink jet recording, and examples of such a surfactant include anionic, cationic, amphoteric, and nonionic surfactants. Moreover, 2 or more types of surfactant can also be used together. The addition amount of the surfactant is approximately 0.01 to 50 mg per 1 m ² of the recording medium. If it exceeds 50 mg, it tends to cause uneven spots during ink jet recording.

  The function-imparting compound may be a hydrophilic binder crosslinking agent.

  As such a cross-linking agent, known ones can be used, and preferred are the aforementioned boric acids, zirconium salts, aluminum salts or epoxy-based cross-linking agents.

The function-imparting compound may be an image stabilizer (hereinafter also referred to as an anti-fading agent). The anti-fading agent suppresses fading caused by light irradiation and fading caused by various oxidizing gases such as ozone, active oxygen, NO _x , and SO _x .

  As the function-imparting compound, a cationic polymer can be used.

In general, the cationic polymer acts as a dye fixing agent and is preferably added in advance to a coating solution for forming a porous receiving layer in order to prevent water resistance and bleeding, but is added to the coating solution. If a problem occurs, the overcoat method can be used. For example, when a cationic polymer is added to increase the viscosity of the coating solution over time or to improve the color developability by providing a distribution of the cationic polymer in the porous layer, it is supplied by an overcoat method. It is preferable. When the cationic polymer is supplied by the overcoat method, the amount is generally in the range of 0.1 to 5 g per 1 m ^{2 of} the recording medium.

  The function-imparting compound may be a water-soluble polyvalent metal compound.

  Water-soluble polyvalent metal compounds generally tend to agglomerate when present in a coating solution containing inorganic fine particles, and this tends to cause minor coating failure and loss of glossiness. preferable.

Examples of such polyvalent metal compounds include sulfates such as Mg ₂ ⁺ , Ca ₂ ⁺ , Zn ₂ ⁺ , Zr ₂ ⁺ , Ni ₂ ⁺ and Al ₃ ⁺ , chlorides, nitrates and acetates. It is done.

  Each of the above functionality-imparting compounds can be used alone or in combination of two or more. Specifically, it is also possible to use an aqueous solution containing two or more types of anti-fading agent, a solution containing an anti-fading agent and a crosslinking agent, a solution containing an anti-fading agent and a surfactant, and further a crosslinking agent, an aqueous solution. The polyvalent metal compound and anti-fading agent can also be used in combination.

  The solvent for the functional compound can be water or a mixed solution of water-miscible organic solvent and water, and it is particularly preferable to use water. A mixed solvent of water and a water-miscible low-boiling organic solvent (for example, methanol, ethanol, i-propanol, n-propanol, acetone, methyl ethyl ketone, etc.) is also a preferable solvent. When water and a water-miscible organic solvent are used in combination, the content of water is preferably 50% by mass or more by mass ratio.

  Here, the low-boiling organic solvent having water miscibility refers to an organic solvent having a solubility of 10% by mass or more with respect to water at room temperature and a boiling point of about 120 ° C. or lower.

  The surface tension of the coating solution used in the coating method of the present invention is preferably 20 to 60 mN / m at room temperature from the viewpoint of obtaining uniform coating properties.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Preparation of the object 1 to be coated >>
A substrate 1 to be coated, which was formed on a support using a four-layered porous ink absorbing layer as a constituent layer, was prepared.

(Production of support)
Low density polyethylene having a density of 0.92 was applied to the back side of a photographic base paper having a water content of 6% and a basis weight of 200 g / m ² by a thickness of 35 μm by extrusion coating. Next, a low density polyethylene containing 5.5% anatase-type titanium oxide on the surface side and having a density of 0.92 was applied by extrusion coating with a thickness of 40 μm to prepare a support having both sides coated with polyethylene. Corona discharge was performed on the front side, the undercoating layer made of polyvinyl alcohol was 0.03 g / m ² , and the corona discharge was also performed on the back side, and then the latex layer was applied at 0.12 g / m ² .

(Preparation of each dispersion)
(Preparation of silica dispersion 1)
Using a jet stream inductor mixer TDS manufactured by Mitamura Riken Kogyo Co., Ltd., 160 kg of gas phase method silica (Tokuyama: Leolosil QS-20) having an average primary particle size of about 12 nm, the pH is adjusted to 2. After suction-dispersing in 480 L of pure water (containing 10 L of ethanol) adjusted to 5 at room temperature, the entire amount was finished with 600 L with pure water to prepare silica dispersion 1.

(Preparation of silica dispersion 2)
Stir 60.0 L of the silica dispersion 1 in 15 L of an aqueous solution (pH = 2.3) containing 2.12 kg of the cationic polymer (HP-1), 2.2 L of ethanol, and 1.1 L of n-propanol. Then, 8.0 L of an aqueous solution containing 320 g of boric acid and 190 g of borax was added, and 200 ml of an aqueous solution containing 2 g of Sanbuco Co., Ltd. antifoam SN381 was added.

  This mixed liquid was dispersed with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd., and the entire amount was finished to 85 L with pure water to prepare silica dispersion 2.

(Preparation of oil dispersion)
210 kg of an aqueous gelatin solution containing 20 kg of diisodecyl phthalate and 20 kg of an antioxidant (AO-1) heated in 45 kg of ethyl acetate and containing 8 kg of acid-treated gelatin, 2.9 kg of the cationic polymer HP-1 and 5 kg of saponin; After mixing at 55 ° C. and emulsifying and dispersing with a high-pressure homogenizer, the entire amount was finished to 300 L with pure water to prepare an oil dispersion.

[Preparation of coating liquid for ink absorbing layer]
Each coating solution for an ink absorbing layer having the following constitution was prepared. In addition, the addition amount of each layer was displayed by the quantity per 1L of coating liquids. In the examples, “%” represents mass% unless otherwise specified.

<First layer coating solution: bottom layer>
Silica dispersion 2 580ml
Polyvinyl alcohol (Kuraray Co., Ltd .: PVA203) 10% aqueous solution 5 ml
6.5% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
290ml
Oil dispersion 30ml
Latex dispersion (Showa Polymer Co., Ltd .: AE803) 42ml
8.5 ml of ethanol
Finish the whole volume with pure water to 1000ml <Second layer coating solution>
Silica dispersion 2 600ml
Polyvinyl alcohol (Kuraray Co., Ltd .: PVA203) 10% aqueous solution 5 ml
6.5% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
270ml
Oil dispersion 20ml
Latex dispersion (Showa Polymer Co., Ltd .: AE803) 22ml
8 ml of ethanol
Finish the whole volume to 1000ml with pure water <Coating liquid for third layer>
Silica dispersion 2 630ml
Polyvinyl alcohol (Kuraray Co., Ltd .: PVA203) 10% aqueous solution 5 ml
6.5% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
270ml
Oil dispersion 10ml
Latex dispersion (Showa Polymer Co., Ltd .: AE803) 5ml
Ethanol 3ml
Finish the whole volume to 1000ml with pure water. <Fourth layer coating solution: top layer>
Silica dispersion 2 660ml
Polyvinyl alcohol (Kuraray Co., Ltd .: PVA203) 10% aqueous solution 5 ml
6.5% aqueous solution of polyvinyl alcohol (average polymerization degree: 3800 saponification degree 88%)
250ml
3% 4% aqueous solution of betaine surfactant
2 ml of 25% aqueous solution of saponin
Ethanol 3ml
Finish the whole volume to 1000ml with pure water.

[Application of ink absorbing layer]
Next, four layers of the above coating solutions are simultaneously formed on the support at 40 ° C. using a coating line comprising the steps shown in FIG. It apply | coated and the to-be-coated body 1 was produced.

<Wet film thickness>
First layer: 42 μm
Second layer: 39 μm
Third layer: 44 μm
Fourth layer: 38 μm
After applying the ink absorbing layer coating liquid, the film surface temperature is decreased to 13 ° C. by passing through a cooling zone maintained at 5 ° C. for 15 seconds, and then the following temperature winds are sequentially applied to the surface of the ink absorbing layer. While spraying, each zone of the drying step 30 was passed through and dried.

  The total drying step was 360 seconds, and the average relative humidity of the blowing wind was 30% or less for the first 270 seconds. After 270 seconds, the humidity was adjusted to a relative humidity of 40 to 60%.

《Overcoat implementation》
[Application 101]
(Preparation of overcoat solution 1)
An aqueous solution containing 1.0% by mass of the following water-soluble dye was prepared, and this was designated as overcoat solution 1.

(Overcoat)
With the application line shown in FIG. 12 (using the second half of the overcoat zone shown in FIG. 12 and one coater), using a slot nozzle spray device having the configuration shown in FIG. 2 and FIG. The prepared overcoat liquid 1 was continuously applied on the prepared substrate 1 for 5 minutes so that the coating speed was 100 m / min and the wet film thickness was 10.0 μm. The slot nozzle spray device used for coating 101 has an angle α formed by the bottom surface of the external die block of 160 degrees, an angle β formed by the coating liquid discharge port of the coating liquid nozzle and the gas discharge port of the gas nozzle, 30 degrees, The widths L1 and L2 of the bottom surface of the die block are 0.5 mm, the widths L3 and L4 of the bottom surface of the external die block are 40 mm, and the distance between the bottom surface of the external die block and the surface of the object to be coated is 2 cm. It was. The gas supplied from the gas nozzle was air, and was supplied from the gas nozzle at a wind speed of 160 m / sec.
Each nozzle shape used was configured as shown in FIG. 10, the opening end of the coating liquid nozzle was a 120 μm square, the pitch was 1000 μm, and the gas nozzle was a 200 μm wide slit.

[Coating 102 to 106]
Coatings 102 to 106 were performed in the same manner except that the angle α formed by the bottom surface of the external die block in the coating 101 was changed to 170 degrees, 180 degrees, 200 degrees, 240 degrees, and 270 degrees, respectively. The slot nozzle spray device changed to 200 degrees, 240 degrees, and 270 degrees used the apparatus shown in FIG.

<< Evaluation result of applicability >>
When the coatings 101 to 106 were performed, the state of the bottom surface portion of the slot nozzle spray device, the flying state of the coating liquid, and the coating surface quality were visually observed, and the following results were obtained.

<Application 101 (α = 160 degrees)>
Overcoat droplets adhered and grew on the bottom surfaces 2c and 2d of the external die block immediately after coating, and became large droplets after 3 minutes of coating, and the droplets flew intermittently, resulting in coating failure on the coating surface. <Application 102 (α = 170 degrees)>
There was no adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and uniform coating properties were obtained. <Coating 103 (α = 180 degrees)>
There was no adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and a uniform coating property was obtained. <Coating 104 (α = 200 degrees)>
There was no adhesion of the overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and uniform coating properties were obtained. <Coating 105 (α = 240 degrees)>
Although the landing rate of the overcoat droplet on the substrate was slightly reduced, the overcoat droplet did not adhere to the bottom surfaces 2c and 2d of the external die block, and uniform coating properties were obtained. <Coating 106 (α = 270 degrees)>
The landing rate of the overcoat droplets on the substrate to be coated has been significantly reduced and the amount of landed (coating amount) distribution in the width direction of coating has greatly deteriorated. The coating method of the present invention using the slot nozzle spray device having an angle α of 170 to 240 degrees is superior to the comparative example in that there is no liquid adhesion to the bottom surface of the external die block and the coating uniformity is excellent. I understand.

Example 2
In the coating 103 (α = 180 degrees, β = 30 degrees) described in the first embodiment, the angle β formed by the coating liquid discharge port of the coating liquid nozzle and the gas discharge port of the gas nozzle is 15 degrees, 45 degrees, and 60 degrees. In the same manner except that the angle was changed to 75 degrees, the coatings 201 to 204 were performed, and together with the coating 103 performed in Example 1, the state of the bottom surface portion of the slot nozzle spray device, the flying state of the coating liquid, and the coating surface quality were visually checked. Observations were made and the following results were obtained.

<Application 201 (β = 15 degrees)>
There was no adhesion of the overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and a uniform coating property was obtained. <Coating 103 (β = 30 degrees)>
There was no adhesion of the overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and a uniform coating property was obtained. <Coating 202 (β = 45 degrees)>
There was no adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and a uniform coating property was obtained. <Coating 203 (β = 60 degrees)>
Although the spray width of the overcoat liquid spreads in the transport direction of the coated body and the landing rate of the overcoat liquid droplets on the coated body slightly decreased, a uniform coating property was obtained.

<Application 204 (β = 75 degrees)>
The landing rate of the overcoat droplets on the substrate to be coated is remarkably lowered, and the adhesion of the overcoat droplets to the bottom surfaces 2c and 2d of the external die block is severe. The coating method of the present invention using the slot nozzle spray device having an angle β of 15 to 60 degrees with the gas discharge port of the gas nozzle has a better landing rate (coating efficiency) on the coated body than the comparative example. It can be seen that there is no liquid adhesion to the bottom surface of the external die block and the coating uniformity is excellent.

Example 3
In the coating 103 (L1, L2 = 0.5 mm) described in Example 1, the widths L1 and L2 of the bottom surface of the internal die block are set to 0.05 mm, 1.0 mm, 1.5 mm, and 2. The coatings 301 to 304 were performed in the same manner except that the thickness was changed to 0 mm, and together with the coating 103 performed in Example 1, visual observation was performed on the coated surface quality (presence of streak failure, point-like failure), and the following results were obtained. Obtained.

<Application 301 (L1, L2 = 0.05 mm)>
No occurrence of streak failure or point-like failure is observed on the obtained coating film surface <Coating 103 (L1, L2 = 0.5 mm)>
No occurrence of streak failure or point-like failure is observed on the obtained coating film surface <Coating 302 (L1, L2 = 1.0 mm)>
When the obtained coating surface is observed in detail, very weak random vertical stripe-like unevenness is observed, but there is no occurrence of point-like failure, and the quality is practically acceptable. <Coating 303 (L1, L2 = 1) .5mm)>
A strong vertical streak-like failure occurs on the obtained coating surface, which is a quality that is practically problematic <Coating 304 (L1, L2 = 2.0 mm)>
In addition to the occurrence of strong vertical streak failure on the surface of the resulting coating, a coarse overcoat droplet that does not become sprayed has landed and a strong point failure has occurred. The coating method of the present invention using the slot nozzle spray device in which each of the widths L1 and L2 is 1 mm or less is superior to the comparative example in that there is no occurrence of streak failure and point-like failure and excellent coating uniformity. I understand that

Example 4
In the coatings 301 to 304 and the coating 103 described in the third embodiment, the slot of the inner die block illustrated in FIG. 6 has a circular arc shape instead of the device illustrated in FIG. 4 as a slot nozzle spray device. As a result of overcoating in the same manner except that the nozzle spray device was used, as in the result described in Example 3, the slots where the widths L1 and L2 of the bottom surface of the internal die block are 1 mm or less, respectively. It was confirmed that the coating method of the present invention using a nozzle spray device was superior in coating uniformity with no occurrence of streak failure or point-like failure compared to the comparative example.

Example 5
In the coating 103 (L3, L4 = 40 mm) described in Example 1, the same applies except that the widths L3 and L4 of the bottom surface of the external die block were changed to 1.0 mm, 10 mm, 50 mm, and 60 mm, respectively. Then, the coatings 501 to 504 were performed, and together with the coating 103 performed in Example 1, the bottom surface portion of the slot nozzle spray device, the flying state of the coating liquid, and the coating surface quality were visually observed, and the following results were obtained. .

<Application 501 (L3, L4 = 1.0 mm)>
Slight adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block was observed, but almost uniform coating properties were obtained. <Coating 502 (L3, L4 = 10 mm)>
There was no adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and a uniform coating property was obtained. <Coating 103 (L3, L4 = 40 mm)>
There was no adhesion of overcoat droplets to the bottom surfaces 2c and 2d of the external die block, and uniform coating properties were obtained. <Coating 503 (L3, L4 = 50 mm)>
Slight adhesion of the overcoat droplets to the bottom surfaces 2c and 2d of the external die block was observed, but a substantially uniform coating property was obtained. <Coating 504 (L3, L4 = 60 mm)>
Overcoat droplets adhere to and grow on the bottom surfaces 2c and 2d of the external die block immediately after overcoating and become large droplets after 3 minutes of coating, and the droplets fly intermittently, resulting in coating failure on the coating surface. From the above results, the coating method of the present invention using the slot nozzle spray device in which the widths L3 and L4 of each of the bottom surfaces of the external die block are in the range of 0.1 to 50 mm is compared with the comparative example. It can be seen that there is no liquid adhesion to the bottom surface of the external die block and the coating uniformity is excellent.

Example 6
In the coating 501 to 504 and the coating 103 described in Example 5 above, the slot nozzle spray device is the same except that the angle α formed by the bottom surface of the external die block is changed to 240 degrees as shown in FIG. As a result of overcoating, similar to the result described in Example 5, a slot nozzle spray device in which the widths L3 and L4 of the bottom surface of the external die block are each in the range of 0.1 to 50 mm is used. It was confirmed that the coating method according to the present invention had no liquid adhesion to the bottom surface of the external die block and was excellent in coating uniformity as compared with the comparative example.

Example 7
In the coating 203 (α = 180 degrees, β = 60 degrees) described in the second embodiment, the widths L1 and L2 of the bottom surfaces of the internal die block are 0.1 mm, and the bottom surfaces of the external die block are each. The widths L3 and L4 are set to 3.0 mm, and the distance L5 between the bottom surface of the external die block and the surface of the object to be coated and the distance L6 between the bottom surface of the internal die block and the surface of the material to be coated as shown in FIG. Except having changed as shown in Table 1, it apply | coats 701-705 similarly, visually observes about coated surface quality (the presence or absence of a spot-like failure), and the result obtained is shown in Table 1.

  As apparent from the results in Table 1, the difference ΔL between the distance L5 between the bottom surface of the external die block and the surface of the coated body and the distance L6 between the bottom surface of the internal die block and the surface of the coated body is set to 2 mm or less. It can be seen that this is a more preferable condition because the occurrence of spotted failure can be suppressed.

Example 8
In the coating methods described in Examples 1 to 7, instead of the aqueous dye solution, as a function-imparting compound, a pH adjuster, a surfactant, a hydrophilic binder cross-linking agent, an image stabilizer, and a water-soluble polyvalent metal compound. As a result of performing the same application using each overcoat liquid each containing, as in the results described in Examples 1 to 7, the present invention using the slot nozzle spray device having the configuration defined in the present invention was used. As compared with the comparative example, the coating method was able to confirm excellent coating uniformity with reduced unevenness and coating failure.

It is the schematic for demonstrating the coating method of this invention. It is a schematic sectional drawing which shows an example of the slot nozzle spray apparatus containing a slot nozzle spray part. It is a schematic diagram explaining the formation and flight state of a slot nozzle spray part and the droplet formed there. It is a schematic sectional drawing which shows an example of a structure of the slot nozzle spray part used by this invention. It is a schematic sectional drawing which shows another example of a structure of the slot nozzle spray part used by this invention. It is a schematic sectional drawing which shows another example of a structure of the slot nozzle spray part used by this invention. It is a schematic sectional drawing which shows another example of a structure of the slot nozzle spray part used by this invention. It is a schematic sectional drawing which shows another example of a structure of the slot nozzle spray part used by this invention. FIG. 3 is a schematic view showing an example of the slot nozzle spray portion of FIG. 2 viewed from the coating liquid nozzle C side. It is the schematic which shows another example which looked at the slot nozzle spray part of FIG. 2 from the coating liquid nozzle C side. It is a disassembled perspective view which shows an example of a slot nozzle spray part. It is a figure which shows an example of the coating production line which has arrange | positioned the slot nozzle spray apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slot nozzle spray part 1d Shim 2a, 2b External die block 2c, 2d Bottom surface of external die block 3a, 3b Internal die block 3c, 3d Bottom surface of internal die block 4 Adjustment pot 5 Pump 6 Flow meter 7 Pressurized air source 8 Valve DESCRIPTION OF SYMBOLS 9 To-be-coated body 10 Base material 11 Ink absorption layer 12 Droplet particle 20 Slide bead coating device 30 Cooling zone A Gas pocket B Coating liquid pocket C Coating liquid nozzle D Gas nozzle E Coating liquid G Compressed air L1, L2 Bottom surface of internal die block Width L3, L4 Bottom width of external die block

Claims (7)

A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
The coating apparatus, wherein an angle β formed by the coating liquid discharge port of the coating liquid nozzle and the gas discharge port of the gas nozzle is 15 degrees or more and 60 degrees or less. A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
The coating apparatus, wherein an angle α formed by the bottom surfaces of the pair of external die blocks at positions facing the coated body is 170 degrees or more and 240 degrees or less. A coating liquid nozzle for transporting the coated body and supplying a coating liquid over a coating width in a direction intersecting the transport direction of the coated body; and a gas nozzle for ejecting a gas in the vicinity of the opening end of the coating liquid nozzle; In a coating apparatus for applying a coating liquid on the substrate to be coated by spraying by forming a droplet by colliding the gas with the coating liquid and spraying the gas,
The slot nozzle spray device includes a pair of internal die blocks and an external die block on the outside of each of the pair of internal die blocks, and the coating liquid nozzle is formed between the pair of internal die blocks, Configuring the gas nozzle between a die block and the external die block;
A pair of external dies having a width L1 and a width L2 of 1 mm or less of each of the bottom surfaces of the pair of internal die blocks at positions facing the object to be coated, and at positions facing the object to be coated Each of the widths L3 and L4 of the bottom surface of the block is 0.1 to 50 mm. The absolute value of the difference ΔL between the distance L5 between the bottom surface of the outer die block and the surface of the object to be coated and the distance L6 between the bottom surface of the inner die block and the surface of the object to be coated is 2 mm or less. The coating apparatus of any one of 1-3. The coating object is an inkjet recording paper having an ink absorbing layer on a substrate, and the coating liquid contains a function-imparting compound for the ink absorbing layer. The coating apparatus of any one of Claims. 6. The function-imparting compound is at least one selected from a pH adjuster, a surfactant, a hydrophilic binder crosslinking agent, an image stabilizer, and a water-soluble polyvalent metal compound. Coating device. The coating method characterized by performing application | coating on a to-be-coated body using the coating device of any one of Claims 1-6.

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