JP2007160199A - Coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method capable of stably forming a coating film having uniform thickness by preventing a web edge (selvedge) from being thickened, and preventing the occurrence of winding misalignment in a winding and the adhesion of a previously wound material to the back surface of a supporting body. <P>SOLUTION: The coating method has a process for drying the coating film by supporting a non-coated surface of a web after coated with a driving roller 12 arranged with 0.5 m path roll pitch until the viscosity of the coating film in 10<SP>-2</SP>[s<SP>-1</SP>] shear rate reaches ≥10<SP>4</SP>mPa s. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating method, and more particularly, to a coating suitable for coating on a water-absorbed and curled web such as resin-coated paper.

  Conventionally, as a method for preventing thick coating of the coating film end (ear part) formed by coating and processing the thick film ear at the end, a method of optimizing the shape of the guide plate in the case of slide coating, In the case of curtain coating or slide coating, a method for optimizing the physical properties of the coating solution or a method for removing the thick coating portion with a roller or air after coating is known.

  Although it is possible to remove the thick coating part formed on the web by these methods, when the phenomenon that the coating liquid on the web drips at the edge of the web after application in the process is caused by the dripping of the coating liquid Thus, an effect that can avoid the formation of the thick coating portion of the web end portion (ear portion) cannot be expected.

Also, in the field of photographic material coating, a coating solution using gelatin as a binder is used to obtain a precise multilayer coating surface shape. Immediately after coating, the coating film is passed through a low temperature zone of about 15 ° C. for 10 to 20 seconds. Is gelled (so-called low temperature setting), and then dried (set drying) with a high air volume in a low temperature and low humidity environment (see, for example, Patent Document 1). Therefore, during the drying, the flow of the coating film is suppressed, and the occurrence of thick coating of the web end portion (ear portion) caused by dripping of the coating liquid can be avoided.
However, when using an aqueous coating solution that does not contain gelatin or the like and cannot be set and dried as described above, the above effect cannot be expected.

In particular, in the case of inkjet photographic paper, generally an aqueous coating solution containing no gelatin is often used. Further, from the viewpoint of printer transportability, there is a strong tendency for inkjet photographic paper to have a structure in which a minus-curl in the width direction is strongly applied. Therefore, as one of the means, the curling of the supporting substrate is made larger. It tends to keep. For this reason, in the process from application to drying, thick coating of the web end portion (ear portion) caused by dripping of the coating liquid tends to occur.
JP 2005-290309 A

  For this reason, when using a support base (web) with a larger curl than the conventional one and running it while supporting it with a pass roll, the support base runs between the pass roll and the pass roll after application. Both ends in the direction are greatly curled (see FIG. 6), and dripping of the coating film edge occurs due to gravity from the curled part, and the coating film edge (ear part) becomes thick and a uniform thickness cannot be obtained. In addition, there is a problem in that winding is caused when winding after drying, and as a result, the thick film portion of the ear portion adheres and subsequent processing cannot be performed.

  The present invention has been made in view of the above, and is a so-called low-temperature setting (for example, gelatin-free) aqueous coating liquid (for example, containing fine particles for forming an ink receiving layer) on a non-porous web such as resin-coated paper. In the step of drying while supporting the non-coated surface of the web that is opposite to the coated surface after coating with a pass roll, the coating is applied at the web end (ear part) between the pass rolls that support the web. It aims at providing the coating method which can prevent the dripping of a liquid and thickening of a coating film easily, and makes it a subject to achieve this objective.

Specific means for achieving the above object are as follows.
<1> After applying the coating liquid on a non-porous web, the coating method includes a step of drying the coating film while supporting the non-coated surface of the web after coating with a pass roll. The coating film is dried by setting the pitch between the pass rolls to 0.3 to 0.6 m until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. It is the coating method characterized by performing.

<2> After applying the coating liquid on the non-porous web, the coating method includes a step of drying the coating film while supporting the non-coated surface of the web after coating with a pass roll. The drying pitch of the coating film is such that the support pitch for supporting the web is 0.3 to 3 until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. The coating method is performed by supporting at least both ends of the web in the axial direction of the pass roll with support members so as to be 0.6 m.

<3> After applying the coating liquid on the non-porous web, the coating method includes a step of drying the coating film while supporting the non-coated surface of the web after coating with a pass roll. While drying the coating film, the web is run by the pass roll, and the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. The coating method is characterized in that at least both ends of the web in the axial direction of the pass roll are supported by an endless belt that rotates in conjunction with the pass roll.

  <4> Used for coating the ink receiving layer of an ink jet recording medium having an ink receiving layer that receives the applied ink and records an image, and the coating liquid is at least for coating the ink receiving layer. The coating method according to any one of <1> to <3>, which is a coating liquid containing fine particles.

According to the present invention, when applying a so-called low-temperature setting (for example, gelatin-free) aqueous coating liquid (for example, a fine particle-containing liquid for forming an ink receiving layer) on a non-porous web such as resin-coated paper. In the step of drying while supporting the non-coated surface of the web opposite to the coated surface with a pass roll after coating, the dripping of the coating liquid and the coating film at the web end (ear part) between the pass rolls supporting the web It is possible to provide a coating method that can easily prevent thickening.
As a result, it is possible to prevent the web end (ear part) from becoming a thick film and stably form a uniform coating film. It is effective for preventing adhesion to the back surface of the support.

Hereinafter, the coating method of the present invention will be described in detail.
The coating method of the present invention is a process of applying a coating liquid onto a non-porous web (after the coating process), and then drying the coating film while supporting the non-coated surface of the web after coating with a pass roll (hereinafter referred to as “the coating film”). (It is referred to as a “drying step”.) Until the viscosity of the coating film at a shear rate of 10 ⁻² [s ⁻¹ ] is 10 ⁴ mPa · s or more (1) The pitch between the pass rolls is narrowed to 0.3 to 0.6 m, or (2) at least both ends of the web in the axial direction of the pass roll are supported by support members, or (3) at least the web in the axial direction of the pass roll Both ends are supported by an endless belt that rotates in conjunction with a pass roll.

Specific embodiments of the coating method of the present invention are as follows.
The coating method according to the first aspect of the present invention includes a coating step, a coating liquid is applied on a non-porous web in the coating step, and then the coating is performed while supporting the non-coated surface of the web with a pass roll. A drying step for drying the film, and this drying step is performed until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. 0.3 to 0.6 m, and the coating film is dried.

<Application process>
In the coating process according to the present invention, coating that cannot be performed on a non-porous web by so-called set drying, that is, set drying in which low-temperature treatment is performed after coating to reduce fluidity (low-temperature set). Apply the liquid.

  The coating liquid here is a coating liquid that does not substantially gel at a low temperature (for example, 15 ° C. or lower), and thus does not substantially decrease the fluidity of the coating film and easily flows along an inclination. As an example, a coating solution substantially free of gelatin, particularly a coating solution for forming an ink receiving layer containing at least fine particles and receiving an externally applied ink to record an image (application for forming an ink receiving layer) Liquid).

Here, “the fluidity does not substantially decrease” means that when the temperature after application is lowered, the web is moved so that the normal direction is substantially parallel to the direction of gravity (such as curling). ) It means that the coating liquid flows to the inclined part and the coating liquid concentrates on the inclined part in the drying process, or still maintains the fluidity so that the coating liquid hangs down from the inclined part. Specifically, it means that the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] is less than 10 ⁴ mPa · s.
Further, “substantially free of gelatin” means that gelatin is not contained to such an extent that the viscosity can be obtained at 15 ° C.

The viscosity at a shear rate of 10 ⁻² [s ⁻¹ ] is measured using a Rheo Stress 600 (manufactured by HAAKE (Germany)) under the temperature after adjusting the coating solution to 30 ° C. is there.

  The coating method is not particularly limited, and for example, a known coating method using an extrusion die coater, air doctor coater, bread coater, rod coater, knife coater, squeeze coater, reverse roll coater, bar coater or the like is used. be able to.

  The non-porous web (hereinafter also referred to as a support) is not particularly limited as long as it is a web in which the coating liquid remains in a film shape for a predetermined time or longer after coating. There is an effect. Here, “non-porous” means that the surface is covered with a resin or the like and there are no pores exceeding several nm on the surface.

  As described above, as the non-porous web, a transparent support made of a transparent material such as plastic, a resin in which a base paper and a thermoplastic resin layer are provided on the surface of at least one side (preferably both sides) of the base paper Examples thereof include an opaque support such as a coating support or an opaque version of the transparent support, and a resin-coated support is particularly preferable. In this case, when an image recording layer capable of image recording (for example, an ink receiving layer for receiving ink and recording an image) is provided on the thermoplastic resin layer, a photographic-like high-quality image can be formed. .

  Specific examples of the transparent support include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, diacetate resins, triacetate resins, acrylic resins, polycarbonate resins, polyvinyl chloride, polyimide resins, cellophane, and celluloid resins. A film, a glass plate, etc. are mentioned.

  As the resin-coated support, art paper, coated paper, cast-coated paper, a paper substrate such as baryta paper used for a silver salt photographic support, and the like provided with a thermoplastic resin layer on both sides, silver salt Preferred examples include resin-coated paper used for photographic paper. In addition, polyesters such as polyethylene terephthalate (PET), cellulose esters such as nitrocellulose, cellulose acetate, and cellulose acetate butyrate, polysulfone, polyphenylene oxide, polyimide, polycarbonate, polyamide, and other plastic films may contain white pigments. Highly glossy film made opaque (may be surface calendered); or a white pigment on the surface of the paper substrate or the high gloss film containing the transparent support or white pigment And a support provided with a polyolefin coating layer containing or not containing.

The surface of the web may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment or the like in order to improve wettability and adhesion.
The thickness of the web is not particularly limited, but is preferably 50 to 300 μm from the viewpoint of handleability.

  Examples of the resin of the resin-coated support include polyolefin resins and resins that are cured with an electron beam. Examples of the polyolefin resin include homopolymers of olefins such as low density polyethylene, high density polyethylene, polypropylene, polybutene, and polypentene, copolymers of two or more olefins such as ethylene-propylene copolymers, or mixtures thereof. Examples of various density and melt viscosity index (melt index) can be used singly or in combination of two or more. In the resin of the resin-coated support, white pigments such as titanium oxide, zinc oxide, talc and calcium carbonate, fatty acid amides such as stearic acid amide and arachidic acid amide, zinc stearate, calcium stearate, aluminum stearate, stearic acid Fatty acid metal salts such as magnesium, antioxidants such as Irganox 1010 and Irganox 1076, blue pigments and dyes such as cobalt blue, ultramarine blue, cecilian blue and phthalocyanine blue, magenta such as cobalt violet, fast violet and manganese purple It is preferable to add various additives such as pigments, dyes, fluorescent brighteners and ultraviolet absorbers in appropriate combinations.

The resin-coated support is manufactured by a so-called extrusion coating method in which a heated and melted resin is cast on a traveling base paper in the case of a polyolefin resin, and both surfaces thereof are coated with the resin. In the case of a resin that is cured by an electron beam, the resin is applied by a commonly used coater such as a gravure coater, a blade coater, etc., and then irradiated with an electron beam to cure and coat the resin.
The web may be coated with various backcoat layers for antistatic properties, transportability, curl adjustment, and the like.

In the case of resin-coated paper, wood pulp is used as a base paper, and paper is made using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp as necessary. As the wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, and it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a large amount of short fibers. However, the ratio of LBSP and / or LDP is preferably 10% by mass or more and 70% by mass or less.
In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium may be added as appropriate.

The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is the 24 mesh residual mass% and 42 mesh residual defined by JIS P-8207. It is preferable that the sum with the mass% is 30 to 70%. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less. The basis weight of the base paper is preferably 30 to 250 g, and particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm. The density of the base paper is generally 0.7 to 1.2 g / m ² (JIS P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS P-8143. A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, the same sizing agent as that which can be added to the base paper can be used. The pH of the base paper is preferably 5 to 9 when measured by a hot water extraction method defined in JIS P-8113.

  The surfaces on both sides of the base paper can generally be coated with polyethylene. The polyethylene is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but other LLDPE, polypropylene and the like can also be used in part.

<Drying process>
In the drying step in the first aspect, after the coating liquid is applied on the non-porous web in the coating step, the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ^The coated film is dried while supporting the non-coated surface of the coated web with a pass roll arranged at a pitch of 0.3 to 0.6 m (pass roll pitch) until the pressure becomes ⁴ mPa · s or more. The viscosity of the coating film is measured by the method described above.

  The pass roll is a roll installed from the beginning of construction of the equipment in order to construct a basic web pass line of the equipment, and it does not matter whether or not it is driven.

In this step, the drying section until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or higher is supported (preferably while the web is running). By setting the pass roll arrangement interval (pass roll pitch) within the range of 0.3 to 0.6 m, the coating liquid at the end of the web (ear part) after application of the coating liquid that cannot be set dry. Since dripping and thickening of the coating film can be easily prevented, uniform coating film formation can be stably performed. As a result, winding is disengaged during winding, and the material that has been previously wound on the back surface of the support Adhesion can be effectively prevented.

In this embodiment, if the pass roll pitch is less than 0.3 m, excessive equipment is required and the installation is expensive, and maintenance is troublesome. Conversely, if the pass roll pitch exceeds 0.6 m, the pitch is too long and the web is too long. Insufficient suppression of curling or the like prevents the coating liquid from dripping at the web edge (ear part) and thickening the coating film effectively.
Among the above, the pass roll pitch is more preferably in the range of 0.3 to 0.4 m in that the effect of the present invention is more effectively achieved.
The pass roll pitch is the distance between the axis of the target roll and the axis.

An example in which the roll pitch of the pass roll is 0.5 m (0.3 to 0.6 m) and the non-coated surface of the web is supported is shown in FIG.
As shown in FIG. 1, the back surface (non-application surface) opposite to the front surface (application surface) of the long-axis-shaped support 11 is a pass roll 12 arranged in the drying zone with a pass roll pitch A of 0.5 m. It can be carried while being supported.

  As the pass roll 12, a diameter that can take the pass roll pitch in the above range regardless of the internal form, and a roll that rotates around the roll axis itself is appropriately selected from the known ones. You can choose.

The coating method according to the second aspect of the present invention comprises: a coating step; a coating liquid is coated on a non-porous web in the coating step, and then the coating is performed while supporting the non-coated surface of the coated web with a pass roll. A drying step of drying the film, and the drying step is performed by drying the coating film, and the viscosity (30 ° C.) of the coating film at a shear rate of 10 ⁻² [s ⁻¹ ] is 10 ⁴ mPa · s or more. Until it becomes, it is set as the structure performed by supporting at least both ends of the web in the axial center direction of a pass roll with a supporting member so that the support pitch which supports a web may be 0.3-0.6 m.

In this embodiment, the drying section until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more is supported (preferably while running the web). Further, a support member for supporting at least both ends of the web (both ends of the web in the axial direction of the pass roll) is provided between the pass rolls, and the support pitch (support interval) for supporting the web is within a range of 0.3 to 0.6 m. As in the case of the first aspect, dripping of the coating liquid at the web edge (ear part) and thickening of the coating film after application of the coating liquid incapable of set drying. Since it can be easily prevented, uniform thickness coating can be stably formed, and as a result, it is possible to effectively prevent winding slippage and adhesion of the previously wound material to the back of the support. it can.

  In addition, about the application | coating process in this aspect, and the detail regarding a non-porous web, a viscosity measurement, etc., and a preferable aspect are the same as that of the case in the above-mentioned 1st aspect.

In this embodiment, if the support pitch is less than 0.3 m, it becomes excessive equipment and the installation is expensive, and the maintenance takes time. On the other hand, if it exceeds 0.6 m, the pitch is too long and the web curls, etc. Insufficient suppression prevents the dripping of the coating liquid at the web edge (ear part) and the thickening of the coating film cannot be effectively prevented.
Among the above, the support pitch is more preferably in the range of 0.3 to 0.4 m in that the effect of the present invention is more effectively achieved.
The support pitch is a distance between the axis of the pass roll and the contact point or tangent line between the support member and the web.

As the support member, a member that can support at least both ends of the web in the axial direction of the pass roll that is substantially orthogonal to the running direction of the web can be appropriately selected, for example, a free roll that is passively driven by an external force that does not have a drive, Circular rotating bodies such as wheels, members that support non-contact with the web (air bearings), members with high slidability (Teflon (registered trademark), Delrin, DLC (diamond like carbon), etc.) From the viewpoint of avoiding damage such as scratches on the web, those capable of rotating at the same speed as the web are preferred.
For example, as shown in FIG. 2, members a), b), and c) that float the web with air jetted from holes on the surface of the member can be arranged and supported, for example, at the end of the web. In addition, the same shape as the members a), b) and c) is made of a material having excellent slidability (Teflon (registered trademark), Delrin, DLC (Diamond Like Carbon), etc.), for example, arranged at the end of the web The same effect can be expected by supporting it.

FIG. 3 shows an example in which the support pitch for supporting the web is 0.5 m (0.3 to 0.6 m) and the non-coated surface of the web is supported.
As shown in FIG. 3, in the drying zone, the free roll 13 has a back surface (non-coated surface) opposite to the front surface (coated surface) of the long-axis support 11 so that the support pitch is 0.5 m between the pass rollers 12. ), And the long roll support 11 is supported and supported by the pass roll 12 and the free roll 13 alternately arranged in the drying zone. it can.
Moreover, it is the same also when it replaces with a free roll and the wheel as shown in FIG. 4 is used.
Here, unlike the existing pass roll, the free roll and the wheel are added to the equipment.

  The free roll 13 is a diameter that can take the support pitch in the above range regardless of the internal form, and is a known roll as long as it is a roll that rotates freely under the force of the web. It can be selected appropriately.

The coating method according to the third aspect of the present invention comprises: a coating step; a coating liquid is coated on a non-porous web in the coating step; A drying step for drying the film, and the drying step is performed by running the web with a pass roll, and the viscosity of the coating film at a shear rate of 10 ⁻² [s ⁻¹ ] (30 ° C. ) Is 10 ⁴ mPa · s or more, and at least both ends of the web in the axial direction of the pass roll are supported by an endless belt that rotates in conjunction with the pass roll.

In this embodiment, the drying section until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more is further between pass rolls that support the web while running. In the case of the first and second embodiments, an endless belt that rotates at least both ends of the web in the axial direction of the pass roll is provided to support the web while traveling. In the same way, it is possible to easily prevent dripping of the coating liquid at the web edge (ear part) and thickening of the coating film after coating of the coating liquid that cannot be set and dried, so that a uniform thickness coating film can be formed. Therefore, it is possible to effectively prevent winding slippage during winding and adhesion of the previously wound material to the back surface of the support.

  In addition, about the application | coating process in this aspect, and the detail regarding a non-porous web, a viscosity measurement, etc., and a preferable aspect are the same as that of the case in the above-mentioned 1st aspect.

FIG. 5 shows an example in which the end portions on both sides in the direction substantially perpendicular to the running direction of the web are supported by the endless rotating belt 16 on the non-application surface.
As shown in FIG. 5, the drying zone is provided between the pass rolls 12 so as to be stretched between the rotary support rolls 14 and 15 that rotate at a constant speed in conjunction with the pass roll 12 and the rotary support rolls 14 and 15. The endless belt 16 can be arranged and configured so that the belt 16 abuts the front surface (application surface) and the back surface (non-application surface) opposite to the front surface of the long-axis support 11. The belt 16 can be used together with the disposed pass rolls 12 to support the long shaft-like support 11 and carry it.

  The two rotation support rolls 14 and 15 that stretch the belt 16 may be rotationally driven in conjunction with the pass roll 12, or only one of them is linked to the pass roll 12 and the other is the one. It may be designed to follow and rotate. In addition, the rotation support rolls 14 and 15 may be configured to receive the rotational force of the pass roll 12 by a gear, a belt, or the like, and can be rotated at the same speed as the pass roll 12 separately from the pass roll 12. In this way, the drive source connected to the rotation support roll may be controlled and interlocked.

As the rotating belt, a belt formed in an endless ring shape can be appropriately selected. As the belt, a belt having a circular shape, an elliptical shape, a rectangular shape, or the like that is optionally selected may be used, and the width of the surface of the belt that contacts the web is not particularly limited.
The material of the belt is not particularly limited, but a resinous material such as polyurethane is preferable from the viewpoint of rotating without damaging the web.

  Moreover, as a rotation support roll, it can select suitably from well-known things, if it is a roll which rotates itself centering on a roll axis center in connection with a pass roll irrespective of an internal form.

In the coating methods of the first to third aspects described above, a coating solution that cannot be set-dried (for example, a coating solution that does not contain gelatin) that is dried at a low temperature after coating to suppress fluidity (set at a low temperature) is dried. In particular, it is suitable for coating the ink receiving layer of an ink jet recording medium having an ink receiving layer for receiving an externally applied ink and recording an image.
In this case, a coating liquid for forming an ink receiving layer containing at least fine particles is used as the coating liquid for coating.

Hereinafter, as an example of a preferable coating liquid used in the coating method of the present invention, an ink-receiving layer forming coating liquid will be described in detail.
The ink receiving layer forming coating liquid is a coating liquid containing at least fine particles for coating an ink receiving layer for receiving an ink applied from outside (preferably by an ink jet method) and recording an image. When the receiving layer forming coating solution is used, an ink jet recording medium having an ink receiving layer provided on a web (support) can be produced.

  The ink receiving layer constituting the ink jet recording medium preferably contains at least a water-soluble resin and a crosslinking agent capable of crosslinking the water-soluble resin together with fine particles. That is, the ink-receiving layer-forming coating liquid contains at least fine particles, preferably contains a water-soluble resin and a cross-linking agent that cross-links the water-soluble resin, and further contains a mordant or a surfactant. It can be constructed using other components.

  The ink receiving layer is constituted to have a porous structure by containing fine particles, thereby improving the ink absorption performance. In particular, when the solid content of the fine particle ink receiving layer is 50% by mass or more, and more preferably more than 60% by mass, it is possible to obtain a more favorable porous structure, thereby further improving the ink absorbability. be able to. Here, the solid content of the fine particle ink receiving layer is a content calculated based on components other than water in the composition constituting the ink receiving layer.

  The porous ink-receiving layer is a layer having a porosity of 50 to 75%, preferably 60 to 70%. If the porosity is 50% or less, ink absorbability may be insufficient, and if it is 75% or more, a problem of powder falling due to insufficient binder may occur. Further, in view of the quality of the ink jet recording medium, the thickness of the ink receiving layer is preferably 20 to 40 μm, and the 60 ° gloss is preferably 30 to 70%.

-Fine particles-
As the fine particles, either organic fine particles or inorganic fine particles can be used. Preferred examples of the organic fine particles include polymer fine particles obtained by, for example, emulsion polymerization, microemulsion polymerization, soap-free polymerization, seed polymerization, dispersion polymerization, suspension polymerization, and the like. Specifically, polyethylene, polypropylene, Examples thereof include powders such as polystyrene, polyacrylate, polyamide, silicone resin, phenol resin, natural polymer, latex or emulsion polymer fine particles, and the like.

Examples of the inorganic fine particles include silica fine particles, colloidal silica, titanium dioxide, barium sulfate, calcium silicate, zeolite, kaolinite, halloysite, mica, talc, calcium carbonate, magnesium carbonate, calcium sulfate, pseudoboehmite, zinc oxide, Examples thereof include zinc hydroxide, alumina, aluminum silicate, calcium silicate, magnesium silicate, zirconium oxide, zirconium hydroxide, cerium oxide, lanthanum oxide, and yttrium oxide.
Among these, inorganic fine particles are preferable from the viewpoint of ink absorbability and image stability, and silica fine particles, colloidal silica, alumina fine particles, or pseudoboehmite are preferable from the viewpoint of forming a better porous structure. The fine particles may be used as primary particles or in a state where secondary particles are formed. The average primary particle size of these fine particles is preferably 2 μm or less, and more preferably 200 nm or less.

  Among these, silica fine particles are generally roughly classified into wet method particles and dry method (vapor phase method) particles according to the production method. In the wet method, a method is mainly used in which active silica is produced by acid decomposition of silicate, and this is appropriately polymerized and coagulated and precipitated to obtain hydrous silica. On the other hand, the gas phase method is a method by high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), a method in which silica sand and coke are heated and reduced by an arc in an electric furnace and oxidized with air. The method of obtaining anhydrous silica by the (arc method) is the mainstream, and the “gas phase method silica” means anhydrous silica fine particles obtained by the gas phase method. As the silica fine particles in the present invention, gas phase method silica fine particles are particularly preferable.

Vapor phase silica is different from hydrous silica in terms of the density of silanol groups on the surface, the presence or absence of vacancies, etc., and exhibits different properties, but is suitable for forming a three-dimensional structure with a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the surface of the fine particles is large at 5 to 8 / nm ² , and the silica fine particles tend to aggregate closely (aggregate). In the case of the method silica, the density of silanol groups on the surface of the fine particles is as small as ² to 3 / nm ² , so that it is sparse soft agglomeration (flocculate), resulting in a structure with a high porosity. Is done.

  Since the vapor phase silica has a particularly large specific surface area, the ink absorption and retention efficiency is high, and since the refractive index is low, transparency can be imparted to the receiving layer by dispersing it to an appropriate particle size. It is characterized by high color density and good color development. The transparency of the receiving layer is important not only for applications that require transparency, such as OHP, but also for obtaining high color density and good color development gloss even when applied to recording media such as photo glossy paper. It is.

  The average primary particle diameter of the vapor phase silica is preferably 50 nm or less, more preferably 20 nm or less, particularly preferably 10 nm or less, and most preferably 3 to 10 nm. Vapor phase silica is easy to adhere to each other due to hydrogen bonds with silanol groups, so that when the average primary particle size is 50 nm or less, it can form a structure with a large porosity, effectively improving ink absorption characteristics. Can be made.

  Silica fine particles may be used in combination with the other fine particles described above. When the other fine particles and the vapor phase silica are used in combination, the content of the vapor phase silica in all the fine particles is preferably 30% by mass or more, and more preferably 50% by mass or more.

As the inorganic fine particles, alumina fine particles, alumina hydrate, a mixture or a composite thereof are also preferable. Of these, alumina hydrate is preferable because it absorbs and fixes ink well, and pseudoboehmite (Al ₂ O ₃ .nH ₂ O) is particularly preferable. Alumina hydrates can be used in various forms, but it is preferable to use sol boehmite as a raw material because a smooth layer can be easily obtained.

  About the pore structure of pseudo boehmite, the average pore radius is preferably 1 to 25 nm, and more preferably 2 to 10 nm. The pore volume is preferably 0.3 to 2.0 ml / g, more preferably 0.5 to 1.5 ml / g. Here, the pore radius and the pore volume are measured by a nitrogen adsorption / desorption method, and can be measured using, for example, a gas adsorption / desorption analyzer (for example, trade name “Omni Soap 369” manufactured by Coulter).

  Among the alumina fine particles, vapor-phase method alumina fine particles are preferable because of their large specific surface area. The average primary particle diameter of the vapor phase alumina fine particles is preferably 50 nm or less, and more preferably 20 nm or less. Furthermore, colloidal silica having an average primary particle size of 50 nm or less is also preferable.

  The above-mentioned fine particles are, for example, JP-A-10-81064, JP-A-10-119423, JP-A-10-157277, JP-A-10-217601, JP-A-11-348409, JP-A-2001-138621, JP-A-2000-43401. 2000-212235, 2000-309157, 2001-96897, 2001-138627, JP-A-11-91242, 8-2087, 8-2090, 8-2091, The embodiments disclosed in JP-A-8-2093, JP-A-8-174992, JP-A-11-192777, JP-A-2001-301314 and the like can also be preferably used.

-Water-soluble resin-
The coating liquid for forming the ink receiving layer preferably contains a water-soluble resin.
Examples of water-soluble resins include polyvinyl alcohol resins that are resins having a hydroxy group as a hydrophilic structural unit [polyvinyl alcohol (PVA), acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl. Alcohol, polyvinyl acetal, etc.], cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.], Chitins, chitosans, starches, resins with ether bonds [polyethylene oxide (PEO), polyp Pyrene oxide (PPO), polyethylene glycol (PEG), poly ether (PVE)], and resins having carbamoyl groups [polyacrylamide (PAAM), polyvinyl pyrrolidone (PVP), polyacrylic acid hydrazide, etc.] and the like. Among these, polyvinyl alcohol resins, cellulose resins, resins having an ether bond, resins having a carbamoyl group, and resins having a carboxyl group are preferable.
Moreover, the polyacrylic acid salt which has a carboxyl group as a dissociative group, a maleic acid resin, an alginate etc. can be mentioned.

  Among these, polyvinyl alcohol resin is particularly preferable. Examples of the polyvinyl alcohol include Japanese Patent Publication No. 4-52786, Japanese Patent Publication No. 5-67432, Japanese Patent Publication No. 7-29479, Japanese Patent No. 2537827, Japanese Patent Publication No. 7-57553, Japanese Patent No. 2502998, and Japanese Patent No. 3053231. JP-A-63-176173, JP-A-2604367, JP-A-7-276787, JP-A-9-207425, JP-A-11-58941, JP-A-2000-135858, JP-A-2001-205924, JP 2001-287444, JP 62-278080, JP 9-39373, JP 2750433, JP 2000-18801, JP 2001-213045, JP 2001-328345, JP 8 -324105, JP-A-11-348417, etc. It is below.

  These water-soluble resins may be used alone or in combination of two or more. As content of the said water-soluble resin, 9-40 mass% is preferable with respect to the total solid content mass of an ink receiving layer, and 12-33 mass% is more preferable.

The water-soluble resin and the fine particles mainly constituting the ink receiving layer of the ink jet recording medium may be a single material or a mixed system of a plurality of materials.
From the viewpoint of maintaining transparency, the type of water-soluble resin combined with the fine particles, particularly silica fine particles, is important. When the gas phase method silica is used, the water-soluble resin is preferably a polyvinyl alcohol resin, more preferably a polyvinyl alcohol resin having a saponification degree of 70 to 100%, and a saponification degree of 80 to 99.5. % Of polyvinyl alcohol resin is particularly preferable.

The polyvinyl alcohol-based resin has a hydroxyl group in its structural unit, and since this hydroxyl group and the surface silanol group of the silica fine particle form a hydrogen bond, a three-dimensional network having a secondary particle of the silica fine particle as a network chain unit. It becomes easy to form a structure. By forming this three-dimensional network structure, it is considered that a porous ink receiving layer having a high porosity and sufficient strength is formed.
In ink jet recording, the porous ink receiving layer obtained as described above can absorb ink rapidly by a capillary phenomenon, and can form dots with good roundness without ink bleeding.

  In addition, the polyvinyl alcohol resin may be used in combination with the other water-soluble resin. When the other water-soluble resin and the polyvinyl alcohol resin are used in combination, the content of the polyvinyl alcohol resin in the total water-soluble resin is preferably 50% by mass or more, and more preferably 70% by mass or more.

<Content ratio of fine particles to water-soluble resin>
The mass ratio [PB ratio; = x / y] of the mass (x) of the fine particles and the mass (y) of the water-soluble resin greatly affects the film structure and film strength of the ink receiving layer. That is, as the mass ratio (PB ratio) increases, the porosity, pore volume, and surface area (per unit mass) increase, but the density and strength tend to decrease.
As the PB ratio (x / y) in the ink receiving layer, the decrease in film strength and cracking during drying caused by the PB ratio being too large are prevented, and the PB ratio is too small, From the viewpoint of preventing the ink absorbability from being lowered due to the void being easily blocked by the resin and decreasing the porosity, 1.5 to 10 is preferable.

  In addition, since stress may be applied to the ink jet recording medium when passing through the transport system of the ink jet printer, the ink receiving layer needs to have sufficient film strength, and when it is cut into a sheet shape In addition, the ink receiving layer needs to have sufficient film strength from the viewpoint of preventing the ink receiving layer from cracking or peeling. In consideration of these, the PB ratio is more preferably 5 or less, and more preferably 2 or more from the viewpoint of ensuring high-speed ink absorbability in an inkjet printer.

For example, a coating solution in which gas phase method silica fine particles having an average primary particle size of 20 nm or less and a water-soluble resin are completely dispersed in an aqueous solution at a PB ratio (x / y) of 2 to 5 is applied on a support and dried. In this case, a three-dimensional network structure in which the secondary particles of silica fine particles are network chains is formed, the average pore diameter is 25 nm or less, the porosity is 50 to 80%, the pore specific volume is 0.5 ml / g or more, A translucent porous film having a specific surface area of 100 m ² / g or more can be easily formed.

-Crosslinking agent-
The ink receiving layer is a porous layer in which a coating layer containing fine particles and a water-soluble resin further contains a crosslinking agent capable of crosslinking the water-soluble resin, and is cured by a crosslinking reaction between the crosslinking agent and the water-soluble resin. Some embodiments are preferred.

Boron compounds are preferred for crosslinking the water-soluble resin, particularly polyvinyl alcohol resin. Examples of the boron compound include borax, boric acid, borates (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ , two Borate (eg, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborate (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na _{2 B 4 O 7 · 10H 2} O), can be mentioned five borate _{(e.g., KB 5 O 8 · 4H 2} O, Ca 2 B 6 O 11 · 7H 2 O, CsB 5 O 5) or the like. Among them, Of these, borax, boric acid and borates are preferable, and boric acid is particularly preferable because a crosslinking reaction can be promptly caused.

As the crosslinking agent for the water-soluble resin, the following compounds other than the boron compound may be used.
For example, aldehyde compounds such as formaldehyde, glyoxal and glutaraldehyde; ketone compounds such as diacetyl and cyclopentanedione; bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5- Active halogen compounds such as triazine and 2,4-dichloro-6-S-triazine sodium salt; divinylsulfonic acid, 1,3-vinylsulfonyl-2-propanol, N, N′-ethylenebis (vinylsulfonylacetamide) ), Active vinyl compounds such as 1,3,5-triacryloyl-hexahydro-S-triazine; N-methylol compounds such as dimethylolurea and methyloldimethylhydantoin; melamine resins (for example, methylolmelamine, alkylated methylolmelamine) ;Epoxy resin;

Isocyanate compounds such as 1,6-hexamethylene diisocyanate; aziridine compounds described in US Pat. Nos. 3,017,280 and 2,983611; carboximide compounds described in US Pat. No. 3,100,704; glycerol triglycidyl Epoxy compounds such as ether; Ethyleneimino compounds such as 1,6-hexamethylene-N, N′-bisethyleneurea; Halogenated carboxaldehyde compounds such as mucochloric acid and mucophenoxycyclolic acid; 2,3-dihydroxy Dioxane-based compounds such as dioxane; titanium-containing aluminum sulfate, chromium alum, potassium alum, metal-containing compounds such as zirconyl acetate, chromium acetate, polyamine compounds such as tetraethylenepentamine, hydrazide compounds such as adipic acid dihydrazide, A low molecule or polymer containing two or more oxazoline groups.
The crosslinking agents may be used alone or in combination of two or more.

  In the crosslinking and curing, a coating liquid for forming an ink receiving layer (hereinafter also referred to as “first liquid”) for forming an ink receiving layer containing fine particles, a water-soluble resin, etc. and / or the following basic solution is crosslinked. And (1) at the same time when the first liquid is applied to form a coating layer, or (2) during the drying of the coating layer formed by applying the first liquid, the coating It is preferably carried out by applying a basic solution having a pH of 7.1 or higher (hereinafter also referred to as “second liquid”) to the coating layer at any time before the layer exhibits reduced drying.

The application of the cross-linking agent is preferably performed as follows when a boron compound is taken as an example. That is, when the ink receiving layer is a layer obtained by crosslinking and curing a coating layer coated with a coating solution (first solution) containing a water-soluble resin containing fine particles and polyvinyl alcohol, crosslinking curing is performed by (1) At the same time that one liquid is applied to form a coating layer, (2) any one of the coating layers formed by applying the first liquid and being dried and before the coating layer exhibits reduced-rate drying Sometimes, it is carried out by applying a basic solution (second liquid) having a pH of 7.1 or higher to the coating layer. The boron compound as the crosslinking agent may be contained in either the first liquid or the second liquid, and may be contained in both the first liquid and the second liquid.
1-50 mass% is preferable with respect to water-soluble resin, and, as for the usage-amount of a crosslinking agent, 5-40 mass% is more preferable.

-Other ingredients-
In addition to the above-mentioned components, the ink receiving layer forming coating liquid contains a mordant and various known additives such as ultraviolet absorbers, antioxidants, fluorescent brighteners, monomers, polymerization initiators, polymerization inhibitors, and bleeding. An inhibitor, an antiseptic, a viscosity stabilizer, an antifoaming agent, a surfactant, an antistatic agent, a matting agent, an anti-curling agent, a water-proofing agent, and the like can be contained. Hereinafter, other components will be abbreviated.

<mordant>
A mordant is preferably contained in order to improve the water resistance and aging resistance of the recorded image. As the mordant, any of an organic mordant such as a cationic polymer (cationic mordant) and an inorganic mordant such as a water-soluble metal compound can be used. Of these, organic mordants are preferable, and cationic mordants are particularly preferable.

  By having a mordant present at least in the upper layer of the ink receiving layer, an interaction works with a liquid ink having an anionic dye as a coloring material, and the coloring material is stabilized to further improve water resistance and aging resistance. Can be improved.

  When a mordant is used, as described later, the mordant is contained in the first liquid in addition to or not contained in the ink receiving layer forming coating liquid (first liquid) for coating the ink receiving layer. In addition, you may make it contain in a basic solution (2nd liquid). It is preferable to use by containing in a second liquid which is a different liquid from the liquid containing fine particles (particularly gas phase method silica). That is, if a mordant is added directly to a coating solution for forming an ink receiving layer, agglomeration may occur in the presence of vapor phase silica having an anionic charge. If the method of individually preparing each and applying them individually is adopted, it is not necessary to consider the aggregation of inorganic fine particles, and the effects of the present invention can be more effectively exhibited.

  As the cationic mordant, a polymer mordant having a primary to tertiary amino group or a quaternary ammonium base as a cationic functional group is preferable, and a cationic non-polymer mordant may also be used. it can. As the polymer mordant, a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base (a mordant monomer), the mordant monomer and another monomer (non-mordant polymer) And those obtained as a copolymer or a condensation polymer. These polymer mordants can be used in any form of a water-soluble polymer or water-dispersible latex particles.

<Surfactant>
The coating liquid for forming an ink receiving layer preferably contains a surfactant. As the surfactant, any of cationic, anionic, nonionic, amphoteric, fluorine and silicon surfactants can be used.
When the surfactant is contained, the content of the surfactant in the ink receiving layer forming coating solution is preferably 0.001 to 2.0%, and more preferably 0.01 to 1.0%.

  Examples of the nonionic surfactant include polyoxyalkylene alkyl ethers and polyoxyalkylene alkyl phenyl ethers (for example, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyalkylene ether) Ethylene nonylphenyl ether), oxyethylene / oxypropylene block copolymer, sorbitan fatty acid esters (for example, sorbitan monolaurate, sorbitan monooleate, sorbitan trioleate, etc.), polyoxyethylene sorbitan fatty acid esters (for example, polyoxyethylene) Sorbitan monolaurate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitant Oleate, etc.), polyoxyethylene sorbitol fatty acid esters (eg, polyoxyethylene sorbitol tetraoleate), glycerin fatty acid esters (eg, glycerol monooleate), polyoxyethylene glycerin fatty acid esters (polyoxymonostearate) Ethylene glycerol, monooleic acid polyoxyethylene glycerin, etc.), polyoxyethylene fatty acid esters (polyethylene glycol monolaurate, polyethylene glycol monooleate, etc.), polyoxyethylene alkylamine, acetylene glycols (eg, 2, 4, 7) , 9-tetramethyl-5-decyne-4,7-diol, and ethylene oxide adducts and propylene oxide adducts of the diols), and the like. Sharp emission alkyl ethers are preferable.

  Examples of the amphoteric surfactant include amino acid type, carboxyammonium betaine type, sulfoammonium betaine type, ammonium sulfate betaine type, imidazolium betaine type, and the like, for example, US Pat. No. 3,843,368, Those described in JP-A-59-49535, JP-A-63-236546, JP-A-5-303205, JP-A-8-262742, and JP-A-10-282619 can be suitably used.

  Examples of the anionic surfactant include fatty acid salts (for example, sodium stearate, potassium oleate), alkyl sulfate esters (for example, sodium lauryl sulfate, triethanolamine lauryl sulfate), and sulfonates (for example, sodium dodecylbenzenesulfonate). Alkyl sulfosuccinate (for example, sodium dioctyl sulfosuccinate), alkyl diphenyl ether disulfonate, alkyl phosphate, and the like.

  Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, pyridinium salts, imidazolium salts, and the like.

  Examples of the fluorosurfactant include compounds derived via an intermediate having a perfluoroalkyl group using a method such as electrolytic fluorination, telomerization, or oligomerization. Examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl trialkyl ammonium salts, perfluoroalkyl group-containing oligomers, and perfluoroalkyl phosphate esters.

  The silicone surfactant is preferably a silicone oil modified with an organic group, and can have a structure in which a side chain of a siloxane structure is modified with an organic group, a structure in which both ends are modified, or a structure in which one end is modified. Examples of the organic group modification include amino modification, polyether modification, epoxy modification, carboxyl modification, carbinol modification, alkyl modification, aralkyl modification, phenol modification, and fluorine modification.

  The ink receiving layer is formed by applying a coating solution for forming an ink receiving layer containing fine particles and a water-soluble resin on the surface of a web (support) to form a coating layer. Further, the ink receiving layer is added to the coating solution and / or the following basic solution. A crosslinking agent for crosslinking the water-soluble resin is added, and (1) the coating layer is formed by coating the ink receiving layer forming coating solution, or (2) the coating layer is formed by coating the ink receiving layer forming coating solution. At any time during the drying of the coating layer to be applied and before the coating layer exhibits reduced-rate drying, a basic solution having a pH of 7.1 or more is applied to the coating layer, It can be suitably formed by a method of crosslinking and curing (Wet-on-Wet method).

The ink-receiving layer-forming coating liquid (first liquid) containing fine particles (for example, vapor phase method silica) and a water-soluble resin (for example, polyvinyl alcohol) can be prepared, for example, as follows. That is,
Fine particles such as gas phase method silica and a dispersant are added to water (for example, silica fine particles in water are 10 to 20% by mass), and a high-speed rotating wet colloid mill (for example, “Clearmix” manufactured by M Technique Co., Ltd.) )), For example, under conditions of high-speed rotation of 10,000 rpm (preferably 5,000 to 20,000 rpm), for example for 20 minutes (preferably 10 to 30 minutes) After dispersion, an aqueous polyvinyl alcohol (PVA) solution (for example, PVA having a mass of about 1/3 of the vapor phase silica) is added, and dispersion is performed under the same rotational conditions as described above. Can do. In order to impart stability to the coating solution, it is preferable to adjust the pH to about 9.2 with aqueous ammonia or the like, or to use a dispersant.

  As a disperser used for dispersion, in addition to the above high-speed rotating wet colloid mill, other colloid mill dispersers other than the high-speed rotating wet colloid mill, a high-speed rotating disperser, a medium stirring disperser (ball mill, sand mill, etc.), Various conventionally known dispersers such as an ultrasonic disperser and a high pressure disperser can be used. Among these, a medium stirring type disperser, a colloid mill disperser (including a high-speed rotating wet colloid mill), or a high-pressure disperser is preferable from the viewpoint of efficiently dispersing the formed fine particles.

  Moreover, water, an organic solvent, or these mixed solvents can be used as a solvent in each process. Examples of the organic solvent that can be used for this coating include alcohols such as methanol, ethanol, n-propanol, i-propanol, and methoxypropanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, acetonitrile, ethyl acetate, and toluene. It is done.

  Furthermore, a chaotic polymer can be used as the dispersant. Examples of the chaotic polymer include the aforementioned mordants. It is also preferable to use a silane coupling agent as the dispersant. The amount of the dispersant added to the fine particles is preferably 0.1 to 30% by mass.

  In the case of the wet-on-wet method, a basic solution (second liquid) is applied to the coating layer at the same time as or after the coating of the ink-receiving layer forming coating liquid (first liquid). You may provide a 2nd liquid, before the coating layer after application | coating comes to show reduction-rate drying. That is, after the application liquid for forming the ink receiving layer (first liquid) is applied, the second liquid is introduced while the applied layer exhibits constant rate drying. This second liquid may contain a mordant.

  The term “before the coating layer comes to show reduced drying” usually refers to a process for several minutes immediately after the application of the coating liquid for forming the ink receiving layer, and during this time, the solvent in the coated coating layer is used. The phenomenon of “constant rate drying” in which the content of (dispersion medium) decreases in proportion to time. About the time which shows this "constant rate drying", it describes in chemical engineering handbook (pages 707-712, Maruzen Co., Ltd. issue, October 25, 1980), for example.

  After the application of the first liquid, it is dried by the drying step in the coating method of the present invention until the coating layer shows reduced-rate drying. This drying is generally performed at 40 to 180 ° C. for 0.5 to 10 minutes ( Preferably, 0.5 to 5 minutes).

  As a method of applying before the coating layer composed of the first liquid shows reduced rate drying, (1) a method of further applying the second liquid on the coating layer, (2) spraying by a method such as spraying And (3) a method of immersing the support on which the coating layer is formed in the second liquid.

  In the method (1), the application method for applying the second liquid is, for example, curtain flow coater, extrusion die coater, air doctor coater, bread coater, rod coater, knife coater, squeeze coater, reverse roll coater, bar A known coating method such as a coater can be used. Among these, an extrusion die coater, a curtain flow coater, a bar coater, and the like are preferable in that the coater does not directly contact an existing coating layer.

  After application of the second liquid, it is generally heated at 40 to 180 ° C. for 0.5 to 30 minutes, and dried and cured. Especially, it is preferable to heat at 40-150 degreeC for 1 to 20 minutes.

In addition, when the basic solution (second liquid) is applied simultaneously with the application of the ink-receiving layer-forming coating liquid (first liquid), the first liquid and the second liquid are the web (support). The ink-receiving layer can be formed by simultaneous application (multilayer application) on the web so as to be in contact with the ink, followed by drying and curing. Simultaneous coating (multilayer coating) can be performed by a coating method using, for example, an extrusion die coater or a curtain flow coater.
After the simultaneous coating, the coating layer formed by coating is dried. In this case, drying is generally performed by heating the coating layer at 40 to 150 ° C. for 0.5 to 10 minutes, preferably 40 to 100. It is carried out by heating at a temperature of 0.5 to 5 minutes.

  When simultaneous coating (multi-layer coating) is performed using, for example, an extrusion die coater, two types of coating liquid discharged simultaneously are formed in the vicinity of the discharge port of the extrusion die coater, that is, before moving onto the web. In this state, a multilayer coating is applied on the support. Since the two-layer coating liquid that has been layered before coating tends to cause a crosslinking reaction at the interface between the two liquids when transferred to the web, the two liquids to be ejected are mixed near the discharge port of the extrusion die coater. This may increase the viscosity and hinder the application operation. Therefore, at the time of simultaneous application, it is preferable to apply the first liquid and the second liquid together with the barrier liquid (intermediate liquid) between the two liquids, and apply the simultaneous triple layer. It is also effective in terms.

  The barrier layer solution can be selected without particular limitation. For example, an aqueous solution containing a trace amount of water-soluble resin, water, or the like can be given. Examples of the water-soluble resin include cellulose resins (for example, hydroxypropyl methylcellulose, methylcellulose, hydroxyethylmethylcellulose, etc.), polyvinylpyrrolidone, and the like.

  After the ink receiving layer is formed on the web, the ink receiving layer is subjected to, for example, a calendar process using a super calender, a gloss calendar, etc., so that the surface smoothness, glossiness, transparency and coating strength are improved. You may make it improve.

When the ink receiving layer is formed, the layer thickness is preferably about 15 μm or more, particularly when the applied ink amount is 8 nL / mm ² and the porosity is 60%. 50 μm is preferred. The pore diameter of the ink receiving layer is preferably 0.005 to 0.030 μm, more preferably 0.01 to 0.025 μm in terms of median diameter.
The porosity and pore median diameter can be measured using a mercury porosimeter (“Bore Sizer 9320-PC2” manufactured by Shimadzu Corporation).

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
<Production of support>
70 parts of maple kraft pulp (LBKP) and 30 parts of acacia kraft pulp (LBKP) were beaten to 330 ml Canadian freeness with a double disc refiner. CATO304L, manufactured by Nippon NSC Co., Ltd.) 1.3 parts, anionic polyacrylamide (DA4104, manufactured by Seiko PMC Co., Ltd.) 0.15 parts, alkyl ketene dimer (size Pine K, manufactured by Arakawa Chemical Co., Ltd.) 29 parts, 0.29 part of epoxidized hebenamide, and 0.32 part of polyamide polyamine epichlorohydrin (Arafix 100, manufactured by Arakawa Chemical Co., Ltd.) are added, and then 0.12 part of an antifoaming agent is further added. A pulp slurry was prepared.

In the process of making the pulp slurry prepared as described above with a long paper machine and pressing the felt surface of the web against the drum dryer cylinder through the dryer canvas for drying, the tensile force of the dryer canvas is 1.6 kg / After drying by setting to cm, polyvinyl alcohol (KL-118, manufactured by Kuraray Co., Ltd.) 1.5 g / m ² was applied to both sides of the base paper with a size press and dried to perform calendar treatment. . The base paper was made with a basis weight of 205 g / m ² to obtain a base paper (base paper) having a thickness of 195 μm.

After performing corona discharge treatment on the wire surface (back surface) side of the obtained base paper, MFR (melt flow rate; hereinafter the same) 16.0 g / 10 min, density 0.96 g / cm using a melt extruder. ³ high density polyethylene [hydrotalcite (trade name: DHT-4A, manufactured by Kyowa Chemical Industry Co., Ltd.) 250 ppm, secondary antioxidant (tris (2,4-di-t-butylphenyl) phosphite, Product name: Irgafos 168, Ciba Specialty Chemicals Co., Ltd., 200 ppm)], MFR 4.0 g / 10 min, low density polyethylene of density 0.93 g / cm ³ is 70/30 (mass ratio) ) Was coated so as to have a thickness of 36 g / m ² to form a thermoplastic resin layer having a mat surface (hereinafter, this thermoplastic resin layer). The surface is referred to as the “back surface”).
After the corona discharge treatment is further applied to the thermoplastic resin layer on the back surface side, aluminum oxide (“Aluminazil 100” manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (manufactured by Nissan Chemical Industries, Ltd.) are used as antistatic agents. Of “Snowtex O”) was dispersed in water at a mass ratio of 1: 2 so that the dry mass was 0.2 g / m ² .

  Further, after the corona discharge treatment is performed on the felt surface (front surface) side of the base paper where the thermoplastic resin layer is not provided, 10% anatase-type titanium dioxide, a trace amount of ultramarine blue, and a fluorescent brightening agent 0.01 % MFR (melt flow rate) 3.8 low-density polyethylene containing polyethylene (vs. polyethylene) is extruded to a thickness of 40 μm using a melt extruder, and a high gloss thermoplastic layer is formed on the surface side of the base paper. (Hereinafter, this highly glossy surface is referred to as “front side”) to obtain a long-axis support (web).

<Preparation of coating solution for forming ink receiving layer>
1) Preparation of silica fine dispersion A-1 In 553 parts of ion-exchanged water stirred at a rotational speed of 2,000 rpm by a homomixer, 25 parts of vapor phase process silica (average primary particle size 7 nm) And a specific surface area of 300 m ² / g by the BET method; hereinafter referred to as silica), followed by dimethyldiallylammonium chloride (Charol DC902P (50% aqueous solution), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.33 part of this was added, 50 parts of silica was further added to this, and 0.67 part of the total prescription amount of the said dimethyl diallyl ammonium chloride was added. Thereafter, 0.54 part of zirconyl acetate (Zircosol ZA-30 (50% aqueous solution), manufactured by Daiichi Rare Element Industries, Ltd.) was added and dissolved as a water-soluble polyvalent metal compound, and the number of revolutions was 4 with a homomixer. A silica pre-dispersion was prepared by treatment with 1,000,000 rpm for 120 minutes.
This pre-dispersion is further dispersed at 130 MPa in one pass using a liquid-liquid collision type disperser (Ultimizer, manufactured by Sugino Machine) to prepare a silica fine dispersion A-1 having a silica concentration of about 15% by mass. did.

2) Preparation of coating liquid A-1 for ink receiving layer formation -Preparation of PVA co-solution-
The following components were mixed under cooling, heated to 90 ° C. and dissolved to prepare a co-solution of polyvinyl alcohol, diethylene glycol monobutyl ether, and Emulgen 109P.
・ Ion-exchanged water: 88.6 parts ・ Emulgen 109P (manufactured by Kao Corporation): 0.23 parts ・ Butisenol 20P (manufactured by Kyowa Hakko Chemical Co., Ltd.): 2.1 parts ・ Polyvinyl alcohol 235: 7.0 parts [PVA-235 (saponification degree: 88.5%, polymerization degree: 3500), manufactured by Kuraray Co., Ltd.]

  Next, the following components (2) to (7) are added to the silica fine dispersion A-1 obtained above, and again using a homomixer at a rotational speed of 2,000 rpm for 20 minutes. Dispersion was performed to prepare a coating liquid A-1 for forming an ink receiving layer.

<Composition of coating liquid A-1 for forming ink receiving layer>
(1) Silica fine dispersion A-1 ... 58.9 parts (2) Boric acid (crosslinking agent) ... 3.9 parts (3) Ion exchange water ... 1.3 parts (4) The PVA co-solution ( 7.61% aqueous solution of water-soluble resin) 31.2 parts (5) Superflex 650 (Daiichi Kogyo Seiyaku Co., Ltd.) 2.2 parts (6) Ethanol 1.2 parts (7) Polyaluminum chloride: 1.3 parts (Alphain 83, manufactured by Daimei Chemical Co., Ltd.)

Next, each component having the following composition was mixed to prepare a mordant coating liquid B.
<Composition of mordant coating liquid B>
(1) Boric acid (crosslinking agent) 0.7 part (2) Ammonium carbonate (manufactured by Kanto Scientific Co., Ltd., reagent grade 1) 5.0 parts (3) Ammonium zirconium carbonate (13% aqueous solution) 27 parts (Zircozol AC-7, manufactured by Daiichi Rare Element Industries, Ltd.)
(4) Ion-exchanged water ... 87.08 parts (5) Emulgen 109P (10% aqueous solution) ... 6.0 parts (Kao Corporation, nonionic surfactant)

<Preparation of inkjet recording material>
After the corona discharge treatment is applied to the front surface of the support obtained above, the coating liquid A- for forming the ink receiving layer is applied to the front surface of the long-axis support that travels at a constant speed using an extrusion die coater. 1 was applied at an application amount of 175 ml / m ² (application process), and dried with a hot air dryer at 60 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the coating film reached 20% (drying) Process). The coating showed constant drying during this period. At this time, as shown in FIG. 1, the drying is performed by using a back surface (non-coated surface; hereinafter, also referred to as a back surface of the support) opposite to the front surface (application surface) of the long-axis support 11 as a drying zone. The sample was conveyed (conveyance speed 20 m / min) while being supported by a pass roll 12 arranged with a pass roll pitch of 0.5 m. The pass roll pitch is the axial distance A between the pass rolls 12.
The viscosity (30 ° C.) of the coating film immediately before entering the drying zone was measured at a shear rate of 10 ⁻² [s ⁻¹ ] using Rheo Stress 600 (manufactured by HAAKE (Germany)). 10 ³ Pa · s.

Then, the coated film after drying is immersed in the mordant coating liquid B obtained above for 3 seconds before showing reduced-rate drying, and 15 g / m ² is adhered on the coated film and further dried at 60 ° C. Then, an ink receiving layer was formed (curing step), and further conveyed and wound on a winding roll.
As described above, a long-axis inkjet recording material in which an ink receiving layer having a dry film thickness of 40 μm was provided on a support was obtained. An ink jet recording sheet can be produced by cutting the ink jet recording material into a desired size.

(Example 2)
In Example 1, the roll pitch A of the pass roll 12 was changed to 1 m, and as shown in FIG. 3, a free roll 13 was provided between the pass rolls 12 in the drying zone of 20 m immediately after coating, and the long support 11 was The support pitch to be supported was narrowed to 0.5 m, and both ends of the long-axis support (support ends in the direction perpendicular to the running direction) were supported by the free rolls 13 in the same manner as in Example 1. An ink jet recording material was obtained.
In addition, when using RheoStress 600 [manufactured by HAAKE (Germany)], the viscosity (30 ° C.) of the coating film immediately after passing 20 m was measured at a shear rate of 10 ⁻² [s ⁻¹ ]. It was 1.20 × 10 ⁴ mPa · s.

(Example 3)
In Example 1, the roll pitch A of the pass roll 12 is changed to 1 m, and as shown in FIG. 5, an endless rotating belt that rotates at a constant speed in synchronism with the pass roll between the pass rolls 12 in the drying section of 20 m immediately after coating. 16 is arranged, and an inkjet recording material is obtained in the same manner as in Example 1 except that both ends of the long-axis support (support end portions in the direction orthogonal to the running direction) are supported by the endless belt 16. It was.
In addition, when using RheoStress 600 [manufactured by HAAKE (Germany)], the viscosity (30 ° C.) of the coating film immediately after passing 20 m was measured at a shear rate of 10 ⁻² [s ⁻¹ ]. It was 1.20 × 10 ⁴ Pa · s.

Example 4
An ink jet recording material was prepared in the same manner as in Example 2 except that the support was replaced with a long-axis support (web) obtained in the following manner.

<Production of support>
25 parts of LBKP made of acacia and 75 parts of LBKP made of aspen were beaten to 330 ml of Canadian freeness by a disc refiner to prepare a pulp slurry.
Next, to the obtained pulp slurry, 1.3% cation modified starch (CAT0304L manufactured by NSC Japan), 0.15% anionic polyacrylamide (DA4104 manufactured by Seiko PMC Co.) per pulp, Alkyl ketene dimer (size pine K manufactured by Arakawa Chemical Co., Ltd.) 0.29%, epoxidized behenamide 0.29%, and polyamide polyamine epichlorohydrin (Arakawa Chemical Co., Ltd .: Arafix 100) 0.32% After adding 0.12% of the antifoaming agent.

In the process of making the pulp slurry prepared as described above with a long paper machine and pressing the felt surface of the web against the drum dryer cylinder through the dryer canvas for drying, the tensile force of the dryer canvas is 1.6 kg / After drying by setting to cm, polyvinyl alcohol (KL-118, manufactured by Kuraray Co., Ltd.) 1.5 g / m ² was applied to both sides of the base paper with a size press and dried to perform calendar treatment. . The base paper was made with a basis weight of 200 g / m ² to obtain a base paper (base paper) having a thickness of 200 μm.

After performing corona discharge treatment on the wire surface (back surface) side of the obtained base paper, MFR (melt flow rate; hereinafter the same) 16.0 g / 10 min, density 0.96 g / cm using a melt extruder. ³ high density polyethylene [hydrotalcite (trade name: DHT-4A, manufactured by Kyowa Chemical Industry Co., Ltd.) 250 ppm, secondary antioxidant (tris (2,4-di-t-butylphenyl) phosphite, Product name: Irgafos 168, Ciba Specialty Chemicals Co., Ltd. 200 ppm)], MFR 4.0 g / 10 min, low density polyethylene with a density of 0.93 g / cm ³ is 80/20 (mass ratio) ) Was coated so as to have a thickness of 25 g / m ² to form a thermoplastic resin layer having a mat surface (hereinafter, this thermoplastic resin layer). The surface is referred to as the “back surface”).
After the corona discharge treatment is further applied to the thermoplastic resin layer on the back surface side, aluminum oxide (“Aluminazil 100” manufactured by Nissan Chemical Industries, Ltd.) and silicon dioxide (manufactured by Nissan Chemical Industries, Ltd.) are used as antistatic agents. Of “Snowtex O”) was dispersed in water at a mass ratio of 1: 2 so that the dry mass was 0.2 g / m ² .

  Further, after the corona discharge treatment is performed on the felt surface (front surface) side of the base paper where the thermoplastic resin layer is not provided, 10% anatase-type titanium dioxide, a trace amount of ultramarine blue, and a fluorescent brightening agent 0.01 % Of MFR (melt flow rate) containing 3.8% (with respect to polyethylene) is extruded to a thickness of 24 μm using a melt extruder, and a high gloss thermoplastic layer is formed on the surface side of the base paper. (Hereinafter, this highly glossy surface is referred to as a “front side”) to obtain a long-axis support (web).

(Example 5)
In Example 4, the pulp composition of 25 parts of LBKP made of acacia and 75 parts of LBKP made of aspen was changed to 70 parts of LBKP made of acacia and 30 parts of LBKP made of aspen. Produced.

(Example 6)
In Example 1, except that the mass ratio of the high density polyethylene and the low density polyethylene on the back surface was changed from 70/30 to 80/20, and the thickness was changed from 36 g / m ² to 33 g / m ^2. In the same manner, an ink jet recording material was produced.

(Comparative Example 1)
An ink jet recording material was obtained in the same manner as in Example 1 except that the roll pitch A of the pass roll 12 was changed from 0.5 m to 1 m in Example 1. As in Example 1, the viscosity (30 ° C.) of the coating film immediately before entering the drying zone was 3.00 × 10 ³ Pa · s.

(Comparative Example 2)
In Example 2, the 20 m dry section was changed from 10 m immediately after application to 10 m immediately after application in which the free roll 13 was provided between the pass rolls 12 and the support pitch for supporting the long support 11 was narrowed to 0.5 m. Except that, an ink jet recording material was obtained in the same manner as in Example 2.
In addition, when the viscosity at the time of passing 10 m immediately after coating was measured by the same method as in Example 2, it was still 7.00 × 10 ³ Pa · s.

(Evaluation)
About each inkjet recording material obtained from the above, the thick coating state of the both ends (ear part; both ends in the direction orthogonal to the running direction) of the ink receiving layer was evaluated according to the following evaluation criteria. The results are shown in Table 1 below.
〔Evaluation criteria〕
○: There was no problem of winding deviation or adhesion at the ear, and there was no problem.
(Triangle | delta): The adhesion | attachment in the ear | edge part with the back surface of a support body which contacts is recognized.
X: Generation | occurrence | production of winding deviation was recognized.

As shown in Table 1, in Examples 1 and 6, even though the viscosity is low, a uniform thickness can be obtained by setting the interval between the pass rolls in the drying zone so that the support pitch interval is 0.5 m. Thus, it was possible to form an ink receiving layer free from winding deviation or adhesion during winding. In Examples 2 to 5, the support was supported and dried until the predetermined viscosity reached 10 ⁴ mPa · s or more, so that a uniform thickness was obtained and the winding slippage when wound up In addition, it was possible to form an ink receiving layer having no adhesion of the previously wound material to the back surface of the support.
On the other hand, in the comparative example, both ends of the support were curled and bent between the pass rolls, and the thick part was formed around the bent part. A phenomenon was observed in which a shift occurred or the material was previously adhered to the back surface of the support.

It is the schematic which shows the example which arrange | positions a pass roll so that a support pitch may be 0.5 m, and performs drying. It is the schematic which shows the specific example of a supporting member. It is the schematic which shows the example which arrange | positions a free roll between pass rolls so that a support pitch may be 0.5 m, and performs drying, supporting both ends of a web. It is the schematic which shows the other example of a supporting member. It is the schematic which shows the example which arrange | positions a rotating belt between pass rolls and performs drying, supporting both ends of a web. It is a schematic explanatory drawing for demonstrating the influence on the coating film during drying with the web with a large edge part curl.

Explanation of symbols

11 ... Web (long axis support)
12 ... Pass rolls 13, 14 ... Free roll 15 ... Rotating belt A ... Pitch, support pitch

Claims (4)

In a coating method having a step of drying a coating film while applying a coating liquid on a non-porous web and then supporting the non-coated surface of the web after coating with a pass roll,
In the step, the pitch between the pass rolls is set to 0.3 to 0.6 m until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. A coating method, wherein the coating film is dried. In a coating method having a step of drying a coating film while applying a coating liquid on a non-porous web and then supporting the non-coated surface of the web after coating with a pass roll,
In the step, the coating film is dried until the viscosity (30 ° C.) at a shear rate of 10 ⁻² [s ⁻¹ ] of the coating film is 10 ⁴ mPa · s or more. The coating method is performed by supporting at least both ends of the web in the axial direction of the pass roll with a support member so that the thickness becomes 0.3 to 0.6 m. In a coating method having a step of drying a coating film while applying a coating liquid on a non-porous web and then supporting the non-coated surface of the web after coating with a pass roll,
In the step, the coating film is dried by running the web by the pass roll, and the viscosity (30 ° C.) of the coating film at a shear rate of 10 ⁻² [s ⁻¹ ] is 10 ⁴ mPa · s or more. Until this time, the coating method is carried out by supporting at least both ends of the web in the axial direction of the pass roll with an endless belt that rotates in conjunction with the pass roll.   Used for coating the ink receiving layer of an ink jet recording medium having an ink receiving layer for receiving an applied ink and recording an image, and the coating liquid contains at least fine particles for coating the ink receiving layer. It is a coating liquid, The coating method of any one of Claims 1-3.

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