JP2006056053A - Spray coating method, spray coating device and inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spray coating method, which can prevent a coating failure due to the falling of droplets during coating and the smudging of a spray coating device from developing and can perform a long-term coating in feeling at rest at the manufacturing of an inkjet recording paper with a surface layer formed by coating a coating liquid on an ink absorbing layer with a spray coating device, the spray coating device and recording paper. <P>SOLUTION: In the spray coating method of the surface layer for producing the inkjet recording paper by a method wherein the surface layer is formed on the ink absorbing layer of a support with the spray coating device arranged at a position intersecting with the conveying direction of the support, a spray coater is covered with a decompressing means, a coating liquid recovering means and a casing having its inside separated by a porous material into two chambers so as to sprayingly coat a coating liquid for forming the surface layer on the ink absorbing layer under the state that the degree of decompression of a first chamber is kept to be -50 to -3,000 Pa and that of a second chamber -60 to -5,000 Pa during coating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a spray for forming an ink jet recording paper (hereinafter also simply referred to as recording paper) by forming a surface layer on the ink absorbing layer by spraying a coating liquid on the ink absorbing layer formed on the support. The present invention relates to a coating method, a spray coating apparatus, and a recording sheet.

  Inkjet recording is a method in which micro droplets of ink are ejected by various operating principles and deposited on recording paper to record images, characters, etc., but they are relatively high speed, low noise, and easy to multicolor. It has some advantages. In particular, since the image quality of printers has recently improved and has reached photographic image quality, the recording paper also realizes photographic image quality and reproduces the texture (glossiness, smoothness, stiffness, etc.) of silver halide photographs. Is required.

  As one method for reproducing the texture of a silver salt photograph, a so-called swelling type recording paper is known in which a hydrophilic binder such as gelatin or polyvinyl alcohol is coated on a support. However, the recording paper produced by this method has drawbacks such as a slow ink absorption speed, a sticky surface after printing, and an image that tends to bleed due to humidity during storage. In particular, since the ink absorption speed is slow, ink droplets mix before being absorbed, and it is easy to cause bleeding between different colors (bleeding) and uneven color within the same color (beading). It is very difficult to obtain a degree of image quality.

  The so-called void type is becoming the mainstream instead of the above swelling type, and the ink absorption layer has porous inorganic fine particles, and the ink is absorbed by the porous inorganic fine particles, so the absorption speed is fast. Is a feature. Examples of such void-type recording paper include JP-A-10-119423, JP-A-10-119424, JP-A-10-175364, JP-A-10-193976, JP-A-10-19376, and JP-A-10-217601. 11-20300, 11-106694, 11-321079, 11-348410, 10-178126, 11-348409, JP-A-2000-27093, 2000-94830, 2000- 158807, 2000-211121, etc.

  On the other hand, in addition to image quality and texture, demands for durability and image storage stability have become higher, and many attempts have been made to reach the silver salt photography level in terms of light resistance, moisture resistance, water resistance, and the like. Examples of the improvement in light resistance include JP-A-57-74192, JP-A-57-87989, JP-A-57-74193, JP-A-58-152072, JP-A-1-95091, JP-A-1-95091 and JP-A-1-95091. 115677, 3-13376, 4-7189, 7-195824, 8-25796, 11-321090, 11-277893, JP-A-2000-37951, and the like. A number of techniques have been disclosed.

  In the case of a void type recording paper, there is not only light resistance but also a problem that it easily causes discoloration due to a trace amount of active harmful gas in the air such as ozone, oxidant, SOx, NOx due to the void structure. In particular, discoloration tends to occur with phthalocyanine-based aqueous dyes used in general color ink jet printers.

  As described above, a method of providing a surface layer on the ink absorbing layer has been studied as one of countermeasures against the problems caused by the void structure of the ink absorbing layer. Providing a surface layer is effective because it does not allow a very small amount of active harmful gas in the air, such as ozone, oxidant, SOx, and NOx, to enter the void structure, and is described in JP-A-7-237348. As shown, a technique of providing a transparent polymer film having a thickness of 0.5 to 30 μm is known.

  As a method for providing the surface layer, the coating liquid is applied on the ink absorbing layer by block coating, gravure roll coating, extrusion coating, or the like.

  1) Since it is difficult to make the coating speed 50 m / min or more, the operation rate is low.

  2) Interference unevenness is likely to occur on the coated surface, resulting in a low commercial value.

  3) The film thickness distribution is unstable and it is difficult to obtain a uniform film thickness layer, which is disadvantageous for preventing invasion of harmful gases.

  4) Since it is difficult to apply a thin film having a film thickness of 5 to 20 μm, the recording paper is colored due to the influence of the film thickness. In addition, the load in the drying process increases.

  For these reasons, coating for forming a surface layer by spray coating using a spray coater is performed as a thin and uniform coating method on the surface layer that prevents intrusion of harmful gases. For example, in order to prevent the sprayed coating liquid from scattering when the coating liquid is sprayed by a spray device over a coating width in a direction intersecting the substrate transport direction to form a coating liquid layer (surface layer) on the base. In addition, there is known a spray coating method and a spray coating apparatus using a spray device disposed in a casing in which a spray coater is held at a reduced pressure (see, for example, Patent Document 1).

  In the case of the spray coating apparatus described in Patent Document 1, it is effective in preventing scattering of the coating liquid sprayed over the entire coating process, however, it has the following problems.

  1) Since the spray coating device is disposed in the sealed casing, the coating liquid that has not been used for coating adheres to the inner wall of the casing and forms droplets on the coating film surface. It is difficult to apply for a long time because there is a risk of dropping and causing application failure.

  2) In order to avoid a failure due to the drop of droplets adhering to the inner wall of the housing, the application is temporarily stopped every short time, and the inside of the housing is wiped before application. ing.

  3) There is a danger that the dried coating film of the coating solution adhering to the inside of the casing and the spray coater may fall on the coating film surface and cause a foreign matter adhesion failure.

From such a situation, the coating liquid is applied on the at least one ink absorbing layer formed on the support by a spray coating device to form a surface layer, and during the production of inkjet recording paper, Spray coating method and spray that can be applied safely for a long time by preventing coating failure due to dropping of liquid droplets, preventing contamination of the spray coating device, and preventing foreign matter adhesion due to coating film dropping in the process It is desired to develop a recording sheet manufactured by a coating apparatus and a recording sheet manufacturing method using this spray coating apparatus.
JP 2004-90330 A

  The present invention has been made in view of the above-described situation, and an object of the present invention is to coat a coating liquid on a at least one ink absorbing layer formed on a support with a spray coating apparatus, and to form a surface layer. When manufacturing and forming inkjet recording paper, long-time coating is performed by preventing coating failure due to dropping of liquid droplets during coating, preventing contamination of the spray coating device, and preventing foreign matter from adhering to the coating liquid falling in the process. It is an object to provide a spray coating method, a spray coating apparatus, and a recording paper manufactured by the spray coating method, which can be performed with confidence.

  The above object of the present invention has been achieved by the following constitution.

(Claim 1)
On the at least one ink absorbing layer formed on the support that is continuously conveyed, a spray coating device disposed at a position that intersects the conveying direction of the support is used to increase the entire width of the ink absorbing layer. In the spray coating method of the surface layer for spray coating the coating liquid, forming the surface layer, and producing the inkjet recording paper,
The spray coating apparatus has a spray coater and a housing,
The housing includes a box-shaped main body having an opening, a decompression unit connected to the main body, and a coating liquid recovery unit.
The opening is disposed close to the ink absorbing layer;
The inside of the housing is divided into a first chamber and a second chamber by a partition wall made of a porous material facing the ink absorption layer,
The spray coater is disposed in the housing so that the vicinity of the spray port is placed in the first chamber, crosses the ink absorbing layer, and faces the ink absorbing layer.
The degree of vacuum in the first chamber is maintained at −50 to −3000 Pa, the degree of vacuum in the second chamber is maintained at −60 to −5000 Pa,
A spray coating method comprising spray-coating a coating solution for forming the surface layer on the ink absorbing layer.

(Claim 2)
The spray coating method according to claim 1, wherein the air permeability of the porous material used for the partition wall is 0.05 to 1000 seconds.

(Claim 3)
The spray coating method according to claim 1 or 2, wherein the coating liquid recovery means is disposed in the first chamber and the second chamber.

(Claim 4)
The spray coating method according to any one of claims 1 to 3, wherein the decompression means is disposed in the first chamber.

(Claim 5)
The spray coater is composed of a block that forms at least one coating liquid supply nozzle and air supply nozzles on both sides of the coating liquid supply nozzle.
The block forming the coating liquid supply nozzle has a coating liquid supply pipe connected to the coating liquid supply nozzle,
The block forming the air supply nozzle has an air supply pipe connected to the air supply nozzle,
When the gap width of the coating liquid supply nozzle is d1, the coating liquid supplied to the coating liquid supply nozzle supplies the coating liquid filtered through a filter having a diameter of 1 / 100d1 to 1 / 1d1.
When the gap width of the air supply nozzle is d2, the air supplied to the air supply nozzle is supplied by the air filtered through a filter having a diameter of 1 / 100d1 to 1 / 1d1. The spray application method according to any one of claims 1 to 4.

(Claim 6)
The spray coating method according to any one of claims 1 to 5, wherein the spray coater is a curtain spray coater.

(Claim 7)
The spray coating method according to claim 1, wherein the ink absorption layer is composed of a porous layer containing at least one inorganic fine particle and a binder.

(Claim 8)
In a surface layer spray coating apparatus for spray-coating a coating liquid on at least one ink absorbing layer formed on a support that is continuously conveyed, forming a surface layer, and producing an inkjet recording paper,
Having a spray coater and a housing, disposed at a position intersecting the transport direction of the support,
The housing includes a box-shaped main body having an opening, a decompression unit connected to the main body, and a coating liquid recovery unit.
The opening is disposed close to the ink absorbing layer;
The inside of the housing is divided into a first chamber and a second chamber by a partition wall made of a porous material facing the ink absorption layer,
The spray coater is disposed in the casing so as to face the ink absorption layer, in the vicinity of the spray port in the first chamber.
The degree of vacuum in the first chamber is maintained at −50 to −3000 Pa, the degree of vacuum in the second chamber is maintained at −60 to −5000 Pa,
A spray coating apparatus, wherein a coating liquid for forming the surface layer is spray coated on the ink absorbing layer.

(Claim 9)
The spray coating apparatus according to claim 8, wherein the air permeability of the porous material used for the partition wall is 0.05 to 1000 seconds.

(Claim 10)
The spray coating apparatus according to claim 8 or 9, wherein the coating liquid recovery means is disposed in the first chamber and the second chamber.

(Claim 11)
The spray coating apparatus according to any one of claims 8 to 10, wherein the decompression means is disposed in the first chamber.

(Claim 12)
The spray coater is composed of a block that forms at least one coating liquid supply nozzle and air supply nozzles on both sides of the coating liquid supply nozzle.
The block forming the coating liquid supply nozzle has a coating liquid supply pipe connected to the coating liquid supply nozzle,
The block forming the air supply nozzle has an air supply pipe connected to the air supply nozzle,
When the diameter of the coating liquid supply nozzle is d1, the coating liquid supplied to the coating liquid supply nozzle supplies the coating liquid filtered through a filter having a diameter of 1 / 1d1 to 1 / 100d1,
The diameter of the air supply nozzle is d2, and the air supplied to the air supply nozzle supplies the air filtered by a filter having a diameter of 1 / 1d1 to 1 / 100d1. The spray coating apparatus according to any one of 8 to 11.

(Claim 13)
The spray coating apparatus according to claim 8, wherein the spray coater is a curtain spray coater.

(Claim 14)
The spray coating apparatus according to any one of claims 8 to 13, wherein the ink absorbing layer is composed of a porous layer containing at least one inorganic fine particle and a binder.

(Claim 15)
An ink jet recording paper produced by the spray coating method according to claim 1.

  When an ink jet recording sheet is produced by coating a coating liquid on the at least one ink absorbing layer formed on the support with a spray coating apparatus to form a surface layer, it is caused by dropping of droplets during coating. Spray coating method, spray coating apparatus, and spray coating capable of performing long-time coating with peace of mind by preventing coating failure, preventing contamination of the spray coating device, and preventing foreign matter adhesion due to coating film dropping in the process. The recording paper manufactured by the method can be provided, and the production efficiency and quality can be improved.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 7, but the present invention is not limited thereto.

  FIG. 1 is a schematic diagram showing an example of a recording paper coating production line in which a spray coating device is used for coating a surface layer. In the drawing, the supply system for the coating liquid to the first coating part and the supply system for the coating liquid and air to the second coating part are omitted.

  In the figure, 1 indicates a coating production line. The coating production line 1 includes a support feeding portion 2, a first coating portion 3 of a coating liquid that forms an ink absorption layer, a cooling portion 4, a first drying portion 5, and a surface on the ink absorption layer. It has the 2nd coating part 6, the 2nd drying part 7, and the winding-up part 8 of the coating liquid which forms a layer.

  Reference numeral 202 denotes an original roll of the support 201. The support 201 fed out from the feed-out unit 2 is coated with the coater 302 to form at least one ink absorbing layer on the support 201 wound around the backup roll 301 in the first coating unit 3. . The coater 302 is preferably a flow-rate type slide bead coating apparatus because it can simultaneously apply a plurality of coating liquids.

  The support having a coating liquid layer for forming a porous ink absorption layer on the support 201 is fixed by the cooling device 401 in the cooling unit 4 because the coating liquid for the porous ink absorption layer contains a hydrophilic binder. In this state, the ink is transported to the first drying unit 5 where the solvent is removed and the ink absorbing layer 203 is formed. Reference numeral 501 denotes a drying box, 502 denotes a conveyance roll, and 503 denotes a reverser that reversely conveys the gas for floating and conveying the support in a non-contact manner with the surface of the coating film in order to avoid contact with the coating surface. . Thereby, it is possible to dry by avoiding contact of the coated surface.

  At the stage where the solvent in the coating liquid layer is removed and the ink absorbing layer 203 is formed in the first drying unit 5 (preferably after the rate-decreasing drying in the first drying unit 5), the first drying unit 5 is disposed outside the first drying unit 5. In the applied second coating unit 6, a coating solution for the surface layer is spray-coated by the spray coating device 601 on the ink absorbing layer 203 of the support wound around the backup roll 602.

  In the second coating unit 6, the support on which the surface layer coating liquid is coated on the ink absorbing layer 203 enters the second drying unit 7, and the solvent of the surface layer coating liquid is removed to form the surface layer. 204 is formed. Reference numeral 701 denotes a drying box, reference numeral 702 denotes a conveyance roll, and reference numeral 703 denotes a reverser that reversely conveys a gas for floating and conveying the support in a non-contact manner with the surface of the coating film in order to avoid contact with the coating surface. . Thereby, it is possible to dry by avoiding contact of the coated surface.

  The solvent of the coating liquid for the surface layer is removed in the second drying unit 7 to form the surface layer 204, and an ink jet recording sheet is completed. The belt-like ink jet recording paper that has come out of the drying box is wound around the winding core 801 by the winding unit 8 to produce a roll-shaped recording paper 802.

  In addition, the drying in the 1st drying part 5 and the 2nd drying part 7 has a preferable method which blows and dries warm air (a warm air blowing means is not shown).

  The position where the second coating unit 6 is disposed is not particularly limited as long as the ink absorption layer 203 is preferably dried at the first drying unit 5 after the rate of drying, and drying can be performed again after coating. For example, the first drying unit 5 and the second drying unit 7 shown in the figure are combined, and the ink absorption layer 203 is provided from the drying unit after the rate-decreasing drying and provided on the upper part of the drying box. It may be inserted or may be disposed between the first drying unit 5 and the second drying unit 7 as shown in the figure. It is possible to select appropriately according to the environment where the coating production line 1 is arranged.

  The spray coating device 601 of the second coating unit 6 is disposed so as to face the coating surface of the support, which is a direction orthogonal to the transport direction. Details of the second coating unit 6 will be described with reference to FIG.

  In the present invention, as shown in the drawing, a coating liquid is spray-coated on the entire width in the width direction of the ink absorbing layer on at least one ink absorbing layer formed on a support that is continuously conveyed, and the surface layer And the second coating unit 6 for producing an ink jet recording paper.

  FIG. 2 is an enlarged schematic plan view of a portion indicated by X in FIG. In this figure, the casing, the coating liquid supply pipe, the air supply pipe, and the like are omitted to show the positional relationship between the curtain spray coater and the support having the ink absorbing layer.

  In the figure, reference numeral 603 denotes a curtain constituting a spray coating apparatus 601 (see FIG. 1) for spray coating a surface layer coating liquid on the ink absorbing layer 203 of the support 201 wound around a backup roll 602. Shows spray coater. A coating liquid layer 204a forms a surface layer coated by the curtain spray coater 603. The spray port of the curtain spray coater 603 corresponds to at least the application width of the belt-like support 201 (refers to the length of the portion to be coated of the belt-like support in the direction intersecting the transport direction of the belt-like support). It preferably has a length. By arranging in this way, the belt-shaped support is transported to the curtain spray coater, and the coating liquid is sprayed as droplets over the coating width on the belt-shaped support, so that the drying load is small and the film thickness is uniform. It is possible to apply a thin coating film. The curtain spray coater 603 is disposed on a frame (not shown) of the casing of the spray application device 601 (see FIG. 1) at a position that intersects the conveying direction of the support (the arrow direction in the figure). In the present invention, “crossing” means an angle at which a line forming a spray port of the curtain spray coater is parallel to the support and intersects the traveling direction of the support. θ1 represents an angle at which the curtain spray coater 603 and the support intersect, and the angle θ1 is preferably 75 to 105 °. In the case of this figure, the case where the angle at which the curtain spray coater 603 and the support intersect is 90 ° is shown. When the angle θ1 is less than 75 °, the application range is widened, so that it is difficult to stably spray the application liquid, and the uniformity of application may be inferior. May be inferior. In addition, since it is necessary to increase the width of the curtain spray coater, maintenance and management of the curtain spray coater may be complicated. The case where the angle θ1 exceeds 105 ° is the same as the case where the angle θ1 is less than 75 °.

  FIG. 3 is an enlarged schematic view of a portion indicated by X in FIG.

  The spray coating device 601 includes a curtain spray coater 603 that is preferable for coating the surface layer of the recording paper of the present invention, and a housing 604 of the curtain spray coater 603 among the spray coaters.

  In the drawing, reference numeral 603a denotes a coating liquid supplied from a coating liquid supply system (not shown) to the curtain spray coater 603. 603b (603c) is a pair for spray-coating the surface layer coating solution supplied to the curtain spray coater 603 on the ink receiving layer 203 on the belt-like support 201 that is continuously conveyed (in the direction of the arrow in the figure). 1 shows a pressurized air supply pipe. Reference numeral 204 a denotes a surface layer coating liquid layer that forms a surface layer formed on the ink absorbing layer 203 on the belt-like support 201. The belt-like support 201 having the ink receiving layer 203 on the surface is moved (conveyed) by the backup roller 602 relative to the spray port of the curtain spray coater 603, and is continuously applied and manufactured. It is possible.

Reference numerals 603d to 603g denote blocks constituting the curtain spray coater 603. Reference numeral 603b1 denotes a pressurized air pocket including a block 603g and a block 603f, and reference numeral 603b2 denotes an air nozzle formed in a gap between the block 603g and the block 603f. Reference numeral 603b3 denotes an air outlet at the end of the air nozzle 603b2. Reference numeral 603c1 denotes a pressurized air pocket including a block 603e and a block 603d, and reference numeral 603c2 denotes an air nozzle formed in a gap between the block 603e and the block 603d. Reference numeral 603c3 denotes an air outlet at the end of the air nozzle 603c2.
Pressurized air supplied from a pressurized air supply source (not shown) through a pressurized air supply pipe 603b (603c) is temporarily stored in a pressurized air pocket 603b1 (603c1), and then air nozzle 603b2. It is ejected from the air outlet 603b3 (603c3) at the end via (603c2).

  Reference numeral 603a1 denotes a coating liquid pocket that is composed of a block 603f and a block 603e, and temporarily stores the coating liquid supplied from the coating liquid supply pipe 603a. Reference numeral 603a2 denotes a coating liquid nozzle formed by a comb-shaped member 603a3 sandwiched in a gap between the block 603f and the block 603e. The comb-shaped member 603a3 will be described with reference to FIG. Reference numeral 603a4 denotes a coating liquid ejection port at the end of the coating liquid nozzle 603a2. The coating liquid stored in the coating liquid pocket 603a1 is ejected from the coating liquid outlet 603a4 at the end of the coating liquid nozzle 603a2, and at the same time, the air outlet 603b3 (603c3) at the end of the air nozzle 603b2 (603c2). It is sprayed in the form of a spray by pressurized air that is more ejected and applied onto the ink receiving layer 203 on the belt-like support 201.

  Reference numeral 603h denotes a spray port of the curtain spray coater 603, which includes an air outlet 603b3 (603c3) and a coating liquid outlet 603a4.

  The housing 604 has a box-shaped main body 604b having an opening 604a on the ink receiving layer 203 side on the support wound around the backup roll 602, and a partition wall 604c dividing the inside of the main body 604b. . 604b1 indicates the upper wall of the main body 604b, 604b2 indicates the side wall, and 604b3 indicates the lower wall. Reference numeral 604c1 denotes an upper partition of the partition 604c, and 604c2 denotes a side partition of the partition 604c. The inside of the main body 604b is divided into a first chamber 604d and a second chamber 604e by a partition wall 604c made of a porous material. The partition wall 604c is provided inside the main body 604b so as to be replaceable. The upper partition wall of the partition wall 604c may be parallel to the upper wall 604b1 of the main body 604b, or may be inclined as shown in the figure, and is inclined to accelerate the recovery of the coating liquid adhering to the partition wall 604c. More preferably.

  The air permeability of the porous material used for the partition wall 604c is preferably 0.05 to 1000 seconds. If the air permeability is less than 0.05 seconds, the sprayed coating solution that has not been used for coating is removed by the partition wall and reattached to the outer wall of the curtain coater, forming droplets and falling onto the coating surface. , Application failure may occur. If the air permeability exceeds 1000 seconds, it takes time to pass through the partition wall, and the sprayed coating liquid that has not been used for coating is removed by the partition wall and reattached to the outer wall of the curtain coater to form droplets. It may fall on the coating surface and cause a coating failure. The air permeability is a value measured according to the air permeability test method defined in JIS P8117.

  The position where the partition wall 604c is disposed is not particularly limited as long as the vicinity of the spray port 603h of the curtain spray coater 603 is in the first chamber 604d. Details will be described with reference to FIG. The second chamber 604e includes suction pipes 604f to 604i which are suction means for reducing the pressure of the first chamber 604d and the second chamber 604e, and recovery of the coating liquid collected in the second chamber 604e that is not used for coating. A coating liquid recovery pipe 604j (604k) as means is provided. The first chamber 604d is provided with a coating liquid recovery pipe 604l (604m) which is a means for collecting the coating liquid not used for coating and collected in the first chamber 604d. The suction pipes 604f to 604i are connected to a decompression means (for example, a vacuum pump, a blower, etc.) (not shown), and the partition 604c is made of a porous material by reducing the pressure in the second chamber 604e. One chamber 604d can also be decompressed. The coating liquid recovery tubes 604j to 604m are connected to a recovery container (not shown).

  The decompression degree of the second chamber 604e is −60 to −5000 Pa, and the decompression degree of the first chamber 604d is −50 to −3000 Pa.

  When the degree of decompression in the second chamber 604e is less than −60 Pa, droplets that are scattered without being used for coating remain in the casing without being discharged from the casing, and are reattached on the support, and the foreign matter. It may also cause adhesion and uneven application. In some cases, droplets of the coating liquid may be scattered outside from the gap between the casing and the support on the backup roll. When the degree of decompression in the second chamber 604e exceeds −5000 Pa, since the suction force is strong, there is a high probability that the droplet of the coating liquid sprayed from the spray port is sucked before landing on the support. Unevenness may occur and the coating yield may be reduced.

  When the degree of decompression in the first chamber 604d is less than −50 Pa, the droplets that are scattered without being used for coating remain in the casing without being discharged from the casing, and are reattached on the support. It may also cause adhesion and uneven application. In some cases, droplets of the coating liquid may be scattered outside from the gap between the casing and the support on the backup roll. When the degree of decompression in the first chamber 604d exceeds −3000 Pa, since the suction force is strong, there is a high probability that the droplet of the coating liquid sprayed from the spray port is sucked before landing on the support. Unevenness may occur and the coating yield may be reduced.

  The sprayed application liquid sprayed from the curtain spray coater 603 and not involved in the application by suction from the suction pipes 604f to 604i moves from the first chamber 604d to the second chamber 604e via the partition wall 604c without scattering. At this time, the liquid adheres to the partition wall 604c and becomes a droplet, and is recovered into a recovery container (not shown) via the coating liquid recovery tubes 604j to 604m. Also, the sprayed coating liquid that has passed through the partition wall 604c adheres to the wall of the second chamber 604e to form liquid droplets, and is collected into a collection container (not shown) via the coating liquid collection pipe 604j (604k).

  The porous material used for the partition wall 604c is not particularly limited as long as it has air permeability. Examples thereof include a wire net, a sponge, a fibrous material, a filter, and a polymer absorbent (Superabsorbent Polymer: SAP). Examples of the polymer absorbent include starch-based graft polymers, carboxyl methylated products, cellulose-based graft polymers, carboxyl methylated products, polyacrylic acid-based, polyacrylate-based, and polyvinyl alcohol-based synthetic polymers. , Polyacrylamide-based, polyoxyethylene-based, isobutylene maleate-based, or the like, or a composite of each, or starch-based, cellulose-based, and synthetic polymer-based mixtures. As an example, when sodium polyacrylate resin is used, when water is absorbed, sodium ions are discharged from the polymer network, and water flows into the gaps in the polymer network that are enlarged due to electron repulsion between carboxylate ions in the polymer side chain. Absorption effect. In addition, as other water-absorbing carriers, for example, sanitary products such as paper diapers and sanitary products as described in the magazine “Surface, Vol. 33, No. 4, 52-59, (1995)”, soil water retention materials It is also possible to use various superabsorbent polymers used for agricultural and horticultural supplies.

  As shown in the figure, the inner side of the main body 604b of the housing 604 is divided into a first chamber 604d and a second chamber 604e by a partition wall 604c made of a porous material, and is sucked from the second chamber 604e and decompressed. By doing so, the following effects can be obtained.

  1) When the sprayed coating liquid remaining without being used for coating moves from the first chamber to the second chamber through the partition by sucking the second chamber, it is collected on the partition as droplets. Therefore, it is possible to prevent a failure due to the drop of the coating liquid droplets adhering to the inside of the casing (including the curtain spray coater) due to scattering onto the ink absorption layer.

  2) It becomes possible to prevent a failure of foreign matter adhesion due to peeling of the coating film of the coating solution adhering to the inside of the casing (including the curtain spray coater).

  3) It is possible to improve the production efficiency by applying for a long time, stabilizing the product performance, and reducing the loss due to failure.

4 is an enlarged schematic view of a portion indicated by Y in FIG.
In the figure, H represents the distance between the spray port 603h and the surface of the ink absorbing layer 203 facing the center of the spray port 603h, and the distance H is preferably in the range of approximately 2 to 50 mm. The type of coating liquid and the thickness of the surface layer It is possible to select appropriately according to the degree. A shows the droplet sprayed in the spray form from the spray port 603h. L indicates the coating width in the transport direction.

  The area range of the coating liquid spray applied onto the ink absorbing layer 203 is preferably always uniform, but in particular, the droplet diameter distribution is uniform and the length L in the transport direction is uniform over the coating width. It is preferable. Further, it is preferable that the spread angle θ2 of the sprayed droplet group is uniform over the coating width with respect to the belt-like support with the spray port 603h as a base point, and the collision speed falling on the ink absorbing layer 203 is uniform. . By these, it becomes possible to ensure the uniformity of the 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.

  S1 (S2) indicates the distance of the gap between the lower wall 604b3 of the main body 604b (see FIG. 3) of the housing 604 (see FIG. 3) and the support on the backup roll 602. The distance S1 (S2) is preferably 1 to 20 mm. When the distance S1 (S2) is less than 1 mm, there is a high possibility of contact with the lower wall 604b3 of the main body 604b (see FIG. 3) of the housing 604 (see FIG. 3) during transport of the support. Scratches may cause a malfunction. When the distance S1 (S2) exceeds 20 mm, droplets of the coating liquid are likely to be scattered and at the same time, a large amount of energy may be required for suction.

T1 (T2) indicates the distance from the center of the air outlet 603b3 (603c3) to the inside of the side partition 604c2 of the partition 604c (see FIG. 3). The distance T1 (T2) is preferably 5 cm or more. The upper limit is not particularly limited, but can be appropriately selected based on the size of the device and the power of the decompression device for maintaining the degree of decompression in the housing.
When the distance T1 (T2) is less than 5 cm, the coating liquid sprayed from the spray port may collide with the partition wall and bounce off, making it impossible to perform stable coating, resulting in coating unevenness, and coating properties may deteriorate. is there.

  FIG. 5 is a schematic diagram showing the relationship among the coating liquid supply system, the pressurized air supply system, and the curtain spray coater.

  In the figure, reference numeral 9 denotes a supply system, which has a coating liquid supply system 901 and a pressurized air supply system 902. In the coating liquid supply system 901, the coating liquid prepared in the coating liquid tank 901a is supplied to the coating liquid supply pipe 603a of the curtain spray coater 603 via the flowmeter 901c and the filter 901d by the liquid feeding pump 901b. It has become. The supplied coating liquid is once stored in the coating liquid pocket, and then ejected from the coating liquid ejection port 603a4 at the end of the coating liquid nozzle 603a2 provided in the width direction of the curtain spray coater 603.

  In the pressurized air supply system 902, the air is pressurized by the pressure pump 902a, and the pressurized air is supplied to the pressurized air supply pipe 603c (603b) of the curtain spray coater 603 via the flow meter 902b and the filter 902c. It has become. The supplied pressurized air is once stored in the pressurized air pocket 603c1 (603b1) and then ejected from the air outlet 603c3 (603b3) at the end via the air nozzle 603c2 (603b2).

  In the spray port 603h, the coating liquid ejected from the coating liquid ejection port 603a4 is sprayed in the form of droplets by the air ejected from the air ejection port 603b3 (603c3).

The angle of the air nozzle with respect to the coating solution nozzle is preferably in the range of 5 to 50 deg. 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 substrate is generally 1 to 50 g / m ^2. The range of is preferable. If it is less than 1 g / m ² , it may be difficult to form a stable and uniform coating film. Conversely, if it exceeds 50 g / m ² , it is necessary to increase the drying load, lengthen the drying process, or increase the temperature. May occur and useless costs may be incurred. 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 air nozzle is not particularly limited as long as it is suitable for coating. Generally, air is used, but the air supply condition is generally 1 to 50 CMM / m (flow rate per coating width). The internal pressure at the air nozzle at that time is preferably 10 kPa or more from the viewpoint of coating uniformity.

  The linear velocity v of air is preferably 126 to 400 m / s from the viewpoint of coating drying property and coating yield. The air linear velocity is the linear velocity of air immediately after the outlet of the air nozzle, and can be determined by measuring with a laser Doppler anemometer, for example, 1D FLV system 8851 manufactured by KANOMAX. The coating yield is the amount of coating solution applied on the ink absorbing layer / the total amount of coating solution supplied × 100 (%), and is calculated by a mass method. That is, the amount of coating liquid applied on the ink absorption layer is calculated from the change in mass before and after application on the ink absorption layer, and the total amount of coating liquid supplied is supplied to the curtain spray coater, that is, the supplied mass, It can be determined from the liquid feed flow rate x the coating time.

  FIG. 6 is a schematic plan view of the spray port of the curtain spray coater. FIG. 6A is a schematic plan view of the spray port of the curtain spray coater shown in FIG. FIG. 6B is a schematic plan view of the spray port when the curtain spray coater comb-shaped member shown in FIG. 5 is removed.

  In the figure, reference numeral 603i (603j) denotes a side plate for assembling the blocks 603d to 603g constituting the curtain spray coater 603. d2 indicates the width of the gap of the air jet 603b3 (603c3) at the end of the air nozzle 603b2 (603c2), and d1 indicates the width of the gap of the coating liquid jet 603a4 at the end of the coating liquid nozzle 603a2. The gap width d2 of the air jet 603b3 (603c3) and the gap width d1 of the coating liquid jet 603a4 are preferably used in the range of 50 to 300 μm. The type of coating liquid and the droplets required when spraying are used. It is possible to select appropriately from the particle size and the like.

The coating liquid sent to the coating liquid outlet 603a4 uses 1 / 1d1 to 1 / 100d1 as the aperture of the filter 901d of the coating liquid supply system 901 when the gap width of the coating liquid outlet 603a4 is d1. It is preferable to be filtered.
When the aperture of the filter 901d is less than 1 / 100d1, the pressure loss increases, the load increases, and the pump may break down. When the diameter of the filter 901d exceeds 1 / 1d1, there is a risk that foreign matter is clogged at the coating liquid ejection port and the occurrence of coating failure increases.

The pressurized air sent to the air outlet 603b3 (603c3) has a diameter of the filter 902c of the pressurized air supply system 902 of 1 / 1d2 when the gap width of the air outlet 603b3 (603c3) is d2. Preferably it is filtered using 1 / 100d2.
When the diameter of the filter 902c is less than 1 / 100d2, the pressure loss increases, the variation in the amount of air supplied increases, and coating unevenness may occur. When the aperture of the filter 902c exceeds 1 / 1d2, there is a risk that foreign matter is clogged at the air outlet, the air amount becomes unstable, the spray becomes unstable, and coating unevenness occurs.

  In the curtain spray coater used in the present invention, the shape of the coating liquid ejection port 603a4 of the coating liquid nozzle can be changed by inserting a comb-shaped member, and can be, for example, rectangular or circular. W indicates the pitch of the comb blade 603a1 (see FIG. 7) of the comb-shaped member.

  As shown in the figure, in the case of a rectangle, it is possible to change the pitch of the coating liquid ejection port 603a4 by maintaining the width of the gap between the coating liquid nozzles and changing the interval between the comb blades of the comb-shaped member 603a3. . Similarly, in the case of a circular shape, the pitch of the coating liquid ejection port 603a4 can be changed by changing the shape of the comb blade and the interval between the comb blades. When the shape of the coating liquid ejection port is changed by inserting the comb-shaped member 603a, the interval between the comb blades is preferably 100 to 3000 μm.

  On the other hand, the shape of the air outlet 603b3 (603c3) of the air outlet 603b3 (603c3) may be a circle or a slit extending to the coating width. In the case of a circle, the interval is preferably about 50 to 500 μm. Other reference numerals are the same as those in FIG.

  FIG. 7 is a schematic exploded perspective view of the curtain spray coater shown in FIGS.

  In the figure, reference numeral 603i (603j) denotes a side plate for assembling the blocks 603d to 603g. 603g and 603f are blocks for forming a pressurized air supply pipe 603b, a pressurized air pocket 603b1, and an air nozzle 603b2 (see FIG. 3) having a predetermined distance. The formed pressurized air pocket 603b1 and the air nozzle 603b2 (see FIG. 3) are provided in the width direction of the blocks 603g and 603f.

  Reference numerals 603f and 603e are blocks for forming a coating liquid pocket 603a1 and a coating liquid nozzle 603a2 (see FIG. 3). The block 603f is provided with a coating liquid supply pipe 603a that receives the coating liquid supplied from the coating liquid tank 901a (see FIG. 5) and communicates with the coating liquid pocket 603a1. The coating solution nozzle 603a2 (see FIG. 3) includes a comb-shaped member 603a3 that divides the coating solution nozzle 603a2 (see FIG. 3) in the vertical direction to form a plurality of coating solution nozzles in the coating width direction. It is pinched. The coating liquid staying in the coating liquid pocket 603a1 flows down through the coating liquid nozzle 603a2 (see FIG. 3) divided by the comb-shaped member 603a3. Reference numeral 603a31 denotes a comb blade of the comb-shaped member 603a3, and an interval between the comb blades 603a31 serves as a coating liquid nozzle. In the case of this figure, 11 nozzles are formed.

  The block 603e and the block 603d are blocks for forming a pressurized air supply pipe 603c, a pressurized air pocket 603c1, and an air nozzle 603c2 (see FIG. 3) having a predetermined distance. The formed pressurized air pocket 603c1 and the air nozzle 603c2 (see FIG. 3) are provided in the width direction of the blocks 603g and 603f.

  The pressurized air supplied from the air supply source (not shown) through the pressurized air supply pipe 603b (603c) stays in the pressurized air pocket 603b1 (603c1), and then the air nozzle 603b2 (603c2). Flow down with pressure.

  The coating liquid flowing down the coating liquid nozzle 603a2 (see FIG. 3) divided by the comb-shaped member 603a3 and the pressurized air flowing down the two air nozzles 603b2 (603c2) are spray ports 603h ( In FIG. 3), they collide to form droplets and fly onto the ink absorbing layer on the support that is the object to be coated.

As the coating solution for forming the surface layer according to the present invention, it is preferable to use coating solutions described in JP-A Nos. 2004-906 and 2004-122705.
The ink absorbing layer in the present invention will be described. The ink absorbing layer being porous means having a large number of voids having a pore diameter of about 5 to 200 nm. It is preferable that the gaps are not isolated independently but are continuously connected to each other. As the definition of the void diameter in this case, for example, a measured value by a mercury intrusion method can be used. Hereinafter, a preferable porous layer will be described.

  The porous layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Conventionally, various methods for forming voids in a film are known. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support, and these polymers are phase-separated from each other in the drying process. A method of forming voids by applying a coating liquid containing solid fine particles and a hydrophilic or hydrophobic resin on a support, and after drying, the inkjet recording paper is immersed in water or a liquid containing an appropriate organic solvent. , A method of creating voids by dissolving solid fine particles, a method of forming voids in a film by applying a coating liquid containing a compound having a property of foaming during film formation, and then foaming this compound in the drying process, porous A coating solution containing a porous solid fine particle and a hydrophilic binder on a support to form voids in the porous fine particles or between the fine particles, and having a volume approximately equal to or larger than the hydrophilic binder Solid particles and or a coating solution containing a particulate oil and a hydrophilic binder is coated on a support, and a method of forming an air gap between the solid particles are known. In the present invention, it is particularly preferable that the porous layer is formed by containing various inorganic solid fine particles having an average droplet diameter of 100 nm or less.

  Examples of the inorganic fine particles used for the above purpose include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide. , Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. A white inorganic pigment etc. can be mentioned.

  The average droplet diameter of the inorganic fine particles is determined by observing the particles themselves or particles appearing on the cross section or surface of the porous layer with an electron microscope, measuring the particle size of 1,000 arbitrary particles, and calculating a simple average value ( (Number average). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.

  As the inorganic fine particles, it is preferable to use silica and solid fine particles selected from alumina or alumina hydrate.

  As the silica that can be used in the present invention, silica synthesized by a usual wet method, colloidal silica, silica synthesized by a gas phase method, or the like is preferably used. Colloidal silica or fine particle silica synthesized by a gas phase method is preferable, and fine particle silica synthesized by a gas phase method is particularly preferable because a high porosity can be obtained. Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as amorphous particles, spherical particles, and acicular particles can be used.

  The inorganic fine particles preferably have a particle size of 100 nm or less. For example, in the case of the gas phase method fine particle silica, the average droplet diameter of the primary particles of the inorganic fine particles dispersed in the primary particle state (particle size in the dispersion state before coating) is preferably 100 nm or less. More preferably, it is 4-50 nm, Most preferably, it is 4-20 nm.

  For example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available as the silica synthesized by the vapor phase method in which the average droplet diameter of primary particles is 4 to 20 nm. The vapor phase fine particle silica can be dispersed to primary particles relatively easily by being sucked and dispersed in water, for example, by a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd.

  In the present invention, a water-soluble binder can be used for the ink absorbing layer. Examples of the water-soluble binder that can be used in the present invention include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginnan (κ, ι, λ, etc.), agar , Pullulan, water-soluble polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like. These water-soluble binders can be used in combination of two or more.

  The water-soluble binder preferably used in the present invention is polyvinyl alcohol.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

  In the present invention, it is preferable to use a polyvalent metal compound as a dye-fixing agent, and so long as the objective effect of the present invention is achieved, it does not preclude the use of a cationic polymer together with these compounds.

Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride Polymer, diallyldimethylammonium chloride / SO ₂ copolymer, polyvinyl imidazole, vinyl pyrrolidone / vinyl imidazole copolymer, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinyl benzyl trimethyl ammonium chloride polymer, (2-methacryloyl) Oxyethyl) trimethylammonium chloride polymer, dimethylaminoethyl methacrylate DOO polymer, and the like.

  Examples include the cationic polymers described in Chemical Industry Times, August 15 and 25, 1998, and polymer dye fixing agents described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd.

The amount of inorganic fine particles used in the ink absorption layer depends largely on the required ink absorption capacity, the porosity of the porous layer, the type of inorganic pigment, and the type of water-soluble binder, but generally 1 m ^{2 of} recording paper. Usually, it is 5-30 g, preferably 10-25 g.

  The ratio of the inorganic fine particles and the water-soluble binder used in the ink absorbing layer is usually 2: 1 to 20: 1 by mass ratio, and particularly preferably 3: 1 to 10: 1.

Further, it may contain a cationic water-soluble polymer having a quaternary ammonium base in the molecule, and is usually used in the range of 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m ^{2 of} the ink jet recording paper. .

In the porous layer, the total amount of voids (void volume) is preferably 20 ml or more per 1 m ² of recording paper. When the void volume is less than 20 ml / m ² , the ink absorbency is good when the amount of ink at the time of printing is small, but when the amount of ink increases, the ink is not completely absorbed and the image quality deteriorates, Problems such as delay in drying are likely to occur.

  In the porous layer having ink holding ability, the void volume relative to the solid content volume is referred to as a void ratio. In the present invention, it is preferable to set the porosity to 50% or more because the voids can be efficiently formed without unnecessarily increasing the film thickness.

  As another type of void type, in addition to forming an ink absorbing layer using inorganic fine particles, a polyurethane resin emulsion, a water-soluble epoxy compound and / or an acetoacetylated polyvinyl alcohol, and an epichlorohydrin polyamide resin are used in combination. The ink absorbing layer may be formed using the applied coating liquid. The polyurethane resin emulsion in this case is preferably a polyurethane resin emulsion having a polycarbonate chain, a polycarbonate chain and a polyester chain and a particle diameter of 3.0 μm, and the polyurethane resin of the polyurethane resin emulsion is a polyol having a polycarbonate polyol, a polycarbonate polyol and a polyester polyol. And the polyurethane resin obtained by reacting the aliphatic isocyanate compound with a sulfonic acid group in the molecule, and further having an epichlorohydrin polyamide resin, a water-soluble epoxy compound and / or an acetoacetylated vinyl alcohol. preferable. In the ink absorption layer using the polyurethane resin, it is estimated that a weak aggregation of a cation and an anion is formed, and accordingly, a void having an ink solvent absorption ability is formed, so that an image can be formed.

  In the present invention, it is preferable to use a curing agent. The curing agent can be added at any time during the preparation of the inkjet recording paper. For example, it may be added to the coating liquid for forming the ink absorbing layer.

  In the present invention, a method of supplying a water-soluble binder curing agent after forming the ink absorbing layer may be used alone, but preferably, the above-described curing agent is added to the coating liquid for forming the ink absorbing layer. It is to be used in combination with the method.

  The curing agent that can be used in the present invention is not particularly limited as long as it causes a curing reaction with a water-soluble binder, but boric acid and its salts are preferable, but other known ones can be used. Specifically, it is a compound having a group capable of reacting with a water-soluble binder or a compound that promotes the reaction between different groups of the water-soluble binder, and is appropriately selected according to the type of the water-soluble binder. Specific examples of the curing agent include, for example, epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl- 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1,3,5) -S-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum and the like.

  Boric acid or a salt thereof refers to an oxygen acid having a boron atom as a central atom and a salt thereof, specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaboron. Examples include acids and their salts.

  Boric acid having a boron atom and a salt thereof as a curing agent may be used alone or in combination of two or more. Particularly preferred is a mixed aqueous solution of boric acid and borax.

  The aqueous solutions of boric acid and borax can be added only in relatively dilute aqueous solutions, respectively, but by mixing them both can be made into a concentrated aqueous solution and the coating solution can be concentrated. Further, there is an advantage that the pH of the aqueous solution to be added can be controlled relatively freely. The total amount of the curing agent used is preferably 1 to 600 mg per 1 g of the water-soluble binder.

  Various additives other than those described above can be used for the ink absorbing layer of the recording paper according to the present invention and other layers provided as necessary. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic, betaine type surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192 No. 57-87989, No. 60-72785, No. 61-146591, No. 1-95091 and No. 3-13376, etc., JP-A No. 59-42993, 59-52689, 62-280069, 61-242871 and JP-A-4 209266, etc., optical brighteners, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and other pH adjusters, antifoaming agents, preservatives, thickeners, antistatic agents Various known additives such as an agent and a matting agent can also be contained.

  The ink absorbing layer may be composed of two or more layers. In this case, the structures of the ink absorbing layers may be the same or different from each other.

The porous layer as described above is particularly preferably used in the ink jet recording method. The void volume of the porous layer preferable for the ink jet recording method is 10 to 30 ml / m ² .

  The coating layer in the recording paper of the present invention can be applied by a conventionally known coating method, for example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method. A slide bead coating method, a curtain coating method, a slot nozzle spray coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

  Various additives can be used for each layer of the recording paper according to the present invention. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic, betaine type surfactants, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192 No. 57-87989, No. 60-72785, No. 61-146591, No. 1-95091 and No. 3-13376, etc., JP-A No. 59-42993, 59-52689, 62-280069, 61-242871 and JP-A-4 209266, etc., optical brighteners, sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and other pH adjusters, antifoaming agents, preservatives, thickeners, antistatic agents Various known additives such as an agent and a matting agent can also be contained.

  As the support that can be used in the present invention, those conventionally known for inkjet recording paper can be used as appropriate, and may be a water-absorbing support, but is preferably a non-water-absorbing support. That is, in the case of the non-water-absorbing support, a larger amount of the water-soluble organic solvent in the pigment ink remains in the recording paper than in the case of the water-absorbing support, and acts more effectively on the dissolution of organic fine particles. Therefore, it is estimated that the effect of the present invention can be remarkably exhibited. To be precise, it is preferable to use “a support that does not absorb the water-soluble organic solvent in the ink”, but here, even if a non-water-absorbing support is used, the effect of the present invention is remarkably exhibited. I think we can.

  Examples of the water-absorbing support that can be used in the present invention include sheets and plates having general paper, cloth, wood, and the like. In particular, paper is excellent in water absorption of the substrate itself and It is most preferable because of its excellent cost. The paper support can be made from chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, CGP, RMP, TMP, CTMP, CMP and PGW, and wood pulp such as waste paper pulp such as DIP. It is. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as a raw material as necessary.

  If necessary, various conventionally known additives such as sizing agents, pigments, paper strength enhancers, fixing agents, fluorescent whitening agents, wet paper strength agents, cationizing agents and the like are added to the paper support. be able to.

  The paper support can be produced with various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine by mixing the above-mentioned fibrous material such as wood pulp and various additives. Further, if necessary, the paper can be subjected to size press treatment with starch, polyvinyl alcohol or the like, various coating treatments, or calendar treatment on a paper making stage or a paper machine.

  Non-water-absorbing supports that can be preferably used in the present invention include transparent supports and opaque supports. Examples of the transparent support include films having materials such as polyester resins, diacetate resins, triatesate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, and celluloid. Among them, those having a property of resisting radiant heat when used for overhead projectors (OHP) are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably 50 to 200 μm.

  Further, as the opaque support, for example, resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which white pigment or the like is added to at least one of the base paper, white pigment such as barium sulfate is added to polyethylene terephthalate. A so-called white pet is preferable.

  For the purpose of increasing the adhesive strength between the various supports and the ink absorbing layer, the support is preferably subjected to corona discharge treatment, subbing treatment or the like prior to application of the ink absorbing layer. Further, the recording paper according to the present invention is not necessarily colorless, and may be a colored recording sheet.

  In the recording paper according to the present invention, it is possible to use a paper support obtained by laminating both sides of a base paper support described in Japanese Patent Application Laid-Open No. 2004-122705 with polyethylene. This is particularly preferable because an image of

  As the coating method, for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferable. Used. The ink absorbing layer is preferably composed of a porous layer described in JP-A-2004-122705.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples. In Examples, “%” indicates mass% unless otherwise specified.

Example 1
Recording paper was produced using the coating production line shown in FIG.

<Preparation of a belt-like support coated with a porous ink absorbing layer>
(Preparation of dispersion)
To 100 g of a 15% aqueous solution of the cationic polymer (P1), 500 g of a 25% aqueous dispersion of fine particle silica (manufactured by Tokuyama, QS-20) having an average primary particle size of 12 μm, then 3.0 g of boric acid, 0. 7 g was added and dispersed with a high-speed homogenizer to obtain a clear blue-white dispersion.

(Preparation of coating solution)
The prepared dispersion was heated to 45 ° C., and a 10% aqueous solution of polyvinyl alcohol (manufactured by Kuraray, PVA203) and a 6% aqueous solution of polyvinyl alcohol (manufactured by Kuraray, PVA245) were each heated to 45 ° C. and then added. Subsequently, 45 degreeC pure water was added and the liquid quantity was adjusted, and the translucent coating liquid was obtained.

(Application)
On a paper support (width 1500 mm, thickness 230 μm) coated on both sides with polyethylene, the above coating solution was applied and dried using a slide bead type coating machine, and a belt-like support coated with a porous ink absorbing layer was coated at 10000 m. Produced. The coating speed was 200 m / min. The amount of each component in the lower layer of the belt-like support coated with the porous ink absorbing layer is as follows, and the dry film thickness is 35 μm.

Fine silica 15g / m ²
Cationic polymer (P1) 2.2 g / m ²
Polyvinyl alcohol 2.3 g / m ²
After applying the ink absorbing layer coating liquid, the film surface temperature is lowered to 10 ° C. or lower by passing through a cooling zone maintained at 10 ° C. for 15 seconds, and then the air at the following temperature is sequentially applied to the surface of the ink absorbing layer. While being sprayed, each zone of the drying process was passed through and dried.

  Note that the total drying process in the first drying section was 360 seconds, of which the average relative humidity of the blowing air was 30% or less for the first 270 seconds. After 270 seconds, the humidity was adjusted to a relative humidity of 40 to 60%.

[Preparation of spray application equipment]
A spray coating apparatus shown in FIG. 3 was prepared. The curtain spray coater had a coating width of 1550 mm, a gap width of the coating solution nozzle of 60 μm, and a gap width of the air nozzle of 200 μm. The angle of the air nozzle with respect to the coating solution nozzle was 40 deg. A porous material (a sponge having a PVA material) having an air permeability of 1.0 seconds was used for the partition walls in the housing. The distance from the inside of the partition wall of the housing to the air jet port was 30 cm.

[Application of surface layer]
When the reduction drying of the dry ink absorbing layer in the first drying section shown in FIG. 1 is completed, the spray coating device shown in FIGS. 2 to 6 is used, and the spray port of the curtain spray coater as shown in FIG. Is arranged so that an angle of 90 ° is parallel to the support and intersects the traveling direction of the support. The degree of reduced pressure in the first and second chambers of the case where the curtain spray coater is installed is changed as shown in Table 1, and the coating solution for the surface layer is sprayed to a wet film thickness of 15 μm. And it dried in the 2nd drying part and produced the recording material which has a surface layer, and was set as the samples 101-112.

  In addition, the whole drying process in a 2nd drying part was made into 100 second, and the wind with relative humidity of 40 to 60% was sprayed.

  The coating solution was filtered using a filter having a caliber of 1/20 with respect to a width of 60 μm between the coating solution nozzles. The air used was filtered using a filter having a 1/50 aperture for the air nozzle gap width of 200 μm.

  The supply condition of air ejected from the air nozzle was 18 CMM / m (flow rate per coating width), and the internal pressure at the air nozzle at that time was 8 kPa. The linear velocity v of air was 150 m / s. The gap between the spray port of the curtain spray coater and the ink absorbing layer was 20 mm, and the coating speed was 200 m / sec. The distance between the lower wall of the main body of the housing and the support on the backup roll was 4 mm.

<Preparation of coating solution for surface layer>
A coating solution having the following composition was prepared.

160 ml of polyaluminum chloride
(Taki Chemical Co., Ltd. PAC250A, solid content 23.5%)
840 ml of water
The viscosity at 25 ° C. was 0.9 mPa as a result of measurement with a B-type viscometer. The surface tension was adjusted with a surfactant so as to be 40 mN / m.

(Evaluation)
Table 1 shows the results of visual evaluation for each of the produced samples 101 to 112 and visual inspection for coating unevenness caused by adhesion of foreign matter and dropping of liquid droplets, and evaluation according to the following evaluation rank.

Evaluation rank of foreign matter adhesion ○: No foreign matter adhesion is observed on the coated surface △: Foreign matter adhesion that is practically acceptable is recognized on the coated surface ×: Many foreign matter adherence is impossible to commercialize Evaluation rank ○: No coating unevenness is observed on the coated surface. Δ: Coating unevenness that is practically acceptable is recognized on the coated surface.

  The effectiveness of the present invention was confirmed.

Example 2
When the sample 106 of Example 1 was prepared, the recording material was used under the same conditions except that the air permeability of the partition and the distance from the center of the air outlet to the inside of the side partition of the partition were changed as shown in Table 2. Were made 201-213. It adjusted suitably by changing the hole diameter / porosity of the air permeability of a partition. As the porous material used for the partition walls, a sponge made of PVA was used.

(Evaluation)
Table 2 shows the results of the visual evaluation for each of the produced samples 201 to 213, which are visually judged according to the coating unevenness accompanying the adhesion of foreign matter and the drop of the liquid droplets, and evaluated according to the same evaluation rank as in Example 1.

  The effectiveness of the present invention was confirmed.

Example 3
When the sample 108 of Example 1 was prepared, the recording material was prepared under the same conditions as shown in Table 3, except that the diameter of the filter used for filtration of the coating liquid and pressurized air supplied to the curtain spray coater was changed. 301 to 318. The width of the gap of the coating liquid jet outlet of the curtain spray coater used was 60 μm, and the width of the gap of the air jet outlet was 200 μm.

(Evaluation)
Table 3 shows the results of visual evaluation on the manufactured samples 301 to 318 and visual inspection for coating unevenness due to adhesion of foreign matter and dropping of liquid droplets, and evaluation according to the same evaluation rank as in Example 1. In the table, the diameter of the filter for the coating liquid indicates a ratio with respect to the width of the gap of the coating liquid jet outlet, and the diameter of the filter for air indicates a ratio with respect to the width of the gap of the air jet outlet.

  The effectiveness of the present invention was confirmed.

It is a schematic diagram which shows an example of the application | coating production line of the recording paper which used the spray coating apparatus for coating of the surface layer. It is an expansion schematic plan view of the part shown by X of FIG. FIG. 2 is an enlarged schematic view of a portion indicated by X in FIG. 1. FIG. 4 is an enlarged schematic view of a portion indicated by Y in FIG. 3. It is a schematic diagram which shows the relationship between a coating liquid supply system, a pressurized air supply system, and a curtain spray coater. It is a schematic plan view of the spray port of a curtain spray coater. FIG. 6 is a schematic exploded perspective view of the curtain spray coater shown in FIGS. 3 to 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coating production line 201 Support body 203 Ink absorption layer 204 Surface layer 204a Coating liquid layer 3 1st coating part 5 1st drying part 6 2nd coating part 601 Spray coating apparatus 602 Backup roll 603 Curtain spray coater 603b3, 603c3 Air Spout 603a4 Coating liquid spout 604 Housing 604c Partition wall 604d First chamber 604e Second chamber 604f to 604i Suction tube 604j to 604m Coating liquid recovery tube 7 Second drying unit 9 Supply system 901d, 902c Filter A Droplet H, S1 , S2, T1, T2 Distance L Coating width d1, d2 Gap width

Claims (15)

On the at least one ink absorbing layer formed on the support that is continuously conveyed, a spray coating device disposed at a position that intersects the conveying direction of the support is used to increase the entire width of the ink absorbing layer. In the spray coating method of the surface layer for spray coating the coating liquid, forming the surface layer, and producing the inkjet recording paper,
The spray coating apparatus has a spray coater and a housing,
The housing includes a box-shaped main body having an opening, a decompression unit connected to the main body, and a coating liquid recovery unit.
The opening is disposed close to the ink absorbing layer;
The inside of the housing is divided into a first chamber and a second chamber by a partition wall made of a porous material facing the ink absorption layer,
The spray coater is disposed in the housing so that the vicinity of the spray port is placed in the first chamber, crosses the ink absorbing layer, and faces the ink absorbing layer.
The degree of vacuum in the first chamber is maintained at −50 to −3000 Pa, the degree of vacuum in the second chamber is maintained at −60 to −5000 Pa,
A spray coating method comprising spray-coating a coating solution for forming the surface layer on the ink absorbing layer. The spray coating method according to claim 1, wherein the air permeability of the porous material used for the partition wall is 0.05 to 1000 seconds. The spray coating method according to claim 1 or 2, wherein the coating liquid recovery means is disposed in the first chamber and the second chamber. The spray coating method according to any one of claims 1 to 3, wherein the decompression means is disposed in the first chamber. The spray coater is composed of a block that forms at least one coating liquid supply nozzle and air supply nozzles on both sides of the coating liquid supply nozzle.
The block forming the coating liquid supply nozzle has a coating liquid supply pipe connected to the coating liquid supply nozzle,
The block forming the air supply nozzle has an air supply pipe connected to the air supply nozzle,
When the gap width of the coating liquid supply nozzle is d1, the coating liquid supplied to the coating liquid supply nozzle supplies the coating liquid filtered through a filter having a diameter of 1 / 100d1 to 1 / 1d1.
When the gap width of the air supply nozzle is d2, the air supplied to the air supply nozzle is supplied by the air filtered through a filter having a diameter of 1 / 100d1 to 1 / 1d1. The spray application method according to any one of claims 1 to 4. The spray coating method according to any one of claims 1 to 5, wherein the spray coater is a curtain spray coater. The spray coating method according to claim 1, wherein the ink absorption layer is composed of a porous layer containing at least one inorganic fine particle and a binder. In a surface layer spray coating apparatus for spray-coating a coating liquid on at least one ink absorbing layer formed on a support that is continuously conveyed, forming a surface layer, and producing an inkjet recording paper,
Having a spray coater and a housing, disposed at a position intersecting the transport direction of the support,
The housing includes a box-shaped main body having an opening, a decompression unit connected to the main body, and a coating liquid recovery unit.
The opening is disposed so as to be close to the ink absorbing layer,
The inside of the housing is divided into a first chamber and a second chamber by a partition wall made of a porous material facing the ink absorption layer,
The spray coater is placed in the casing so as to face the ink absorbing layer, in the vicinity of the spray port in the first chamber.
The degree of vacuum in the first chamber is maintained at −50 to −3000 Pa, the degree of vacuum in the second chamber is maintained at −60 to −5000 Pa,
A spray coating apparatus, wherein a coating liquid for forming the surface layer is spray coated on the ink absorbing layer. The spray coating apparatus according to claim 8, wherein the air permeability of the porous material used for the partition wall is 0.05 to 1000 seconds. The spray coating apparatus according to claim 8 or 9, wherein the coating liquid recovery means is disposed in the first chamber and the second chamber. The spray coating apparatus according to any one of claims 8 to 10, wherein the decompression means is disposed in the first chamber. The spray coater is composed of a block that forms at least one coating liquid supply nozzle and air supply nozzles on both sides of the coating liquid supply nozzle.
The block forming the coating liquid supply nozzle has a coating liquid supply pipe connected to the coating liquid supply nozzle,
The block forming the air supply nozzle has an air supply pipe connected to the air supply nozzle,
When the diameter of the coating liquid supply nozzle is d1, the coating liquid supplied to the coating liquid supply nozzle supplies the coating liquid filtered through a filter having a diameter of 1 / 1d1 to 1 / 100d1,
The diameter of the air supply nozzle is d2, and the air supplied to the air supply nozzle supplies the air filtered by a filter having a diameter of 1 / 1d1 to 1 / 100d1. The spray coating apparatus according to any one of 8 to 11. The spray coating apparatus according to claim 8, wherein the spray coater is a curtain spray coater. The spray coating apparatus according to any one of claims 8 to 13, wherein the ink absorption layer is composed of a porous layer containing at least one inorganic fine particle and a binder. An ink jet recording paper produced by the spray coating method according to claim 1.

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