JP2010240955A - Recording sheet and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording sheet which shows a remarkable improvement in ink color development properties, bleeding resistance in high humidity, water resistance, and ink absorption, since the concentration distribution of a water-soluble aluminum chemical compound contained in an ink absorption layer is uneven with a specified concentration distribution on a support side. <P>SOLUTION: This recording sheet has the ink absorption layer 3, which is formed on a support 12 and contains inorganic microparticles, a water-soluble resin, and a water-soluble aluminum chemical compound, and shows that the concentration distribution of the water-soluble aluminum chemical compound is uneven on the support 12 side. In the sheet, the content of the water-soluble aluminum chemical compound in the surface side layer, from the surface side to the depth upto 30% of the total layer 3 thickness, is ≤60% of the content of the water-soluble aluminum chemical compound in the support side layer from the support side to the depth upto 30% of the ink absorption layer 3 thickness. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a recording sheet and a method for producing the same, and in particular, an ink absorbing layer containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound is provided on a support, and the concentration distribution of the water-soluble aluminum compound is The present invention relates to a recording sheet that is unevenly distributed on the support side and a method for manufacturing the recording sheet.

  2. Description of the Related Art Inkjet recording apparatuses are widely used because they are excellent in low noise, have low running costs, and can record high-quality images on a wide variety of recording sheets.

  As a recording sheet (recording paper) for an ink jet recording apparatus, a sheet having a porous ink absorbing layer containing inorganic fine particles such as silica and a hydrophilic binder such as polyvinyl alcohol on a support is preferably used. . In such a recording sheet, it is known that a water-soluble aluminum compound is contained in the ink absorbing layer for the purpose of improving the quality of the recording sheet.

  Patent Document 1 is an example of a recording sheet in which a water-soluble aluminum compound is contained in an ink absorption layer. In Patent Document 1, at least two ink absorption layers mainly containing fine particle silica are formed on a support, water-soluble zirconium is contained in the ink absorption layer away from the support, and the water-solubility of the entire ink absorption layer is increased. The concentration distribution of the aluminum compound is more unevenly distributed in a portion near the support. Thereby, it is said that quality improvement can be performed in the color development, high-humidity bleeding, water resistance, and ink absorbability of the manufactured recording sheet.

  In Patent Document 1, in order to make the concentration distribution of the water-soluble aluminum compound unevenly distributed on the support side, the ink absorption layer is cooled at 10 ° C. for 20 seconds before being dried, and then heated air at a low temperature of 30 to 55 ° C. is sprayed. And dry. That is, in Patent Document 1, the ink absorbing layer is cooled and thickened and dried while maintaining a low temperature state, thereby suppressing the diffusion of the water-soluble aluminum compound and unevenly distributed on the support side. It is considered.

JP 2006-110771 A

  However, even the method of slowly drying the ink absorbing layer at a low temperature of 30 to 55 ° C. disclosed in Patent Document 1 cannot sufficiently suppress the diffusion of the water-soluble aluminum compound in the ink absorbing layer, There is a drawback that the aluminum compound cannot be effectively unevenly distributed on the support side. As a result, the quality improvement of the manufactured recording sheet cannot be sufficiently achieved.

  In addition, Patent Document 1 has a drawback in that it requires a large amount of energy because the ink absorption layer must be cooled and then heated and dried, and it takes a longer time to dry.

  The present invention has been made in view of such circumstances, and the concentration distribution of the water-soluble aluminum compound contained in the ink absorption layer is unevenly distributed with a predetermined concentration distribution on the support side. An object of the present invention is to provide a recording sheet excellent in color developability, high-humidity bleeding, water resistance, and ink absorbability, and capable of reducing drying energy during production, and a method for producing the same.

  According to a first aspect of the present invention, in order to achieve the above object, an ink absorbing layer containing inorganic fine particles, a water-soluble resin and a water-soluble aluminum compound is provided on a support, and the water-absorbing layer in the ink absorbing layer is provided. In the recording sheet in which the concentration distribution of the water-soluble aluminum compound is unevenly distributed on the support side, the content of the water-soluble aluminum compound in the surface side layer from the surface side of the ink absorbing layer to the layer thickness of 30% is Provided is a recording sheet, wherein the content is 60% or less of the content of the water-soluble aluminum compound in the support side layer from the support side to the layer thickness of 30%.

  According to the recording sheet of claim 1 of the present invention, the content of the water-soluble aluminum compound in the surface side layer from the surface side of the ink absorbing layer to the layer thickness of 30% is from the support side of the ink absorbing layer to the layer side. Since the content of the water-soluble aluminum compound in the support-side layer up to 30% in thickness is not more than 60%, the color development of the ink, high-humidity bleeding, and ink absorbability can be remarkably improved as compared with the prior art.

  In the present invention, the content of the water-soluble aluminum compound in the surface side layer from the surface side of the ink absorption layer to the layer thickness of 30% is within the support side layer from the support side of the ink absorption layer to the layer thickness of 30%. When the content of the water-soluble aluminum compound is 50% or less, the printing density is further improved, which is more preferable.

In order to achieve the above object, according to a second aspect of the present invention, an ink absorbing layer containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound is provided on a support, and the water-absorbing layer in the ink absorbing layer is provided. In the method for producing a recording sheet in which the concentration distribution of the functional aluminum compound is unevenly distributed on the support side, a first coating step of coating the ink-absorbing layer coating liquid on the continuous belt-like support, A drying step of rapidly drying the ink absorbing layer at an average drying rate of 1 to 3 g / m ² · sec until the moisture content of the ink absorbing layer coated and formed on the support is dried to a range of 18 to 30% by mass. And a second coating step of applying a hardened coating solution for hardening the ink absorbing layer on the freshly dried ink absorbing layer within 10 seconds after the rapid drying. Records characterized by The manufacturing method of the sheet | seat is provided.

According to the second aspect of the present invention, the ink absorbing layer is dried at an average drying speed of 1 to 3 g / m until the moisture content of the ink absorbing layer formed on the support is dried in the range of 18 to 30% by mass. Rapid drying was performed in ² seconds. By this rapid drying, the concentration distribution of the water-soluble aluminum compound in the ink absorption layer can be effectively unevenly distributed on the support side. Then, within 10 seconds after the rapid drying, a hardening coating solution for hardening the ink absorbing layer was applied onto the ink absorbing layer in a dry state.

  Thereby, since the ink absorption layer is cured while the water-soluble aluminum compound of the ink absorption layer is unevenly distributed, the uneven distribution state can be fixed. As a result, it is possible to produce the recording sheet according to claim 1 in which the concentration distribution of the water-soluble aluminum compound is preferably unevenly distributed on the support side in the ink absorbing layer.

  In addition, in order to make the water-soluble aluminum compound unevenly distributed on the support side, it is not necessary to cool and heat and dry the ink absorption layer as in the prior art, and it can be dried in a relatively short time. Energy can be reduced.

  In the production method of the present invention, a preferable uneven distribution state of the water-soluble aluminum compound in the ink absorption layer is that the content of the water-soluble aluminum compound in the layer from the surface side of the ink absorption layer to a layer thickness of 30% is the ink absorption. It is preferably 60% or less of the water-soluble aluminum compound content in the layer from the support side of the layer to the layer thickness of 30%.

  This is because the color developability, high-humidity bleeding, and ink absorbability of the recording sheet can be further improved.

  In the production method of the present invention, the drying step is preferably a hot air drying method in which hot air having a hot air average temperature of 50 to 120 ° C. is blown onto the ink absorption layer.

Any drying method can be used as long as the ink absorbing layer can be dried at an average drying speed of 1 to 3 g / m ² · sec. However, even if high-temperature hot air drying, which is a normal drying method, is performed, The concentration distribution of the water-soluble aluminum compound can be unevenly distributed in a preferable state. Therefore, since the present invention can be carried out only by changing the conditions of the existing hot air drying apparatus, it is not necessary to provide a special drying apparatus or to modify the drying apparatus.

  The production method of the present invention can also be applied when the ink absorption layer is formed of a plurality of layers. For example, when the ink absorbing layer is formed of two layers, the concentration distribution of the water-soluble aluminum compound can be increased in the lower layer close to the support by applying the present invention.

  According to the recording sheet of the present invention and the method for producing the same, the concentration distribution of the water-soluble aluminum compound contained in the ink absorbing layer is unevenly distributed with a predetermined concentration distribution on the support side. It is excellent in high humidity bleeding, water resistance, and ink absorption. Further, the energy for manufacturing the recording sheet can be reduced.

Sectional drawing explaining the preferable uneven distribution state of the water-soluble aluminum compound in the ink absorption layer of the recording sheet of this invention Schematic diagram showing the overall configuration of a manufacturing apparatus for carrying out the method for manufacturing a recording sheet of the present invention The conceptual diagram explaining an example of the drying apparatus in this invention Table for explaining an embodiment of the present invention

  Hereinafter, preferred embodiments of a recording sheet and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

  In the recording sheet 1 of the present invention, an ink absorption layer 3 containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound is provided on a support 12, and the water-soluble aluminum compound in the ink absorption layer 3 is provided. The concentration distribution is unevenly distributed on the support 12 side.

  As shown in the sectional view of the ink absorbing layer 3 in FIG. 1, it is important that the uneven distribution state of the water-soluble aluminum compound is as follows.

  That is, when the layer thickness of the ink absorbing layer 3 is A, the content of the water-soluble aluminum compound in the surface side layer B from the surface side 3A (opposite side of the support) of the ink absorbing layer 3 to the layer thickness of 30%. However, it is 60% or less of the content of the water-soluble aluminum compound in the support side layer C from the support 12 side of the ink absorption layer 3 to the layer thickness of 30%.

  Here, the average content of the water-soluble aluminum compound in the ink absorbing layer is preferably in the range of 0.5 to 15% by mass, more preferably in the range of 1 to 10% by mass with respect to the fine particle silica.

  The recording sheet provided with the ink absorption layer 3 having the concentration distribution of the water-soluble aluminum compound can remarkably improve the ink color development, high-humidity bleeding, and ink absorption.

  The concentration distribution of the water-soluble aluminum compound in the ink absorption layer 3 is, for example, by using EMPA (Electron Probe Micro Analyzer) or the like for the cross-section sample of the ink absorption layer 3 manufactured by a microtome or the like in the thickness direction of the ink absorption layer. It can be evaluated by measuring.

  The method for producing the recording sheet of the present invention having the characteristics as described above will be described below.

  FIG. 2 is a conceptual diagram showing the overall configuration of a manufacturing apparatus for carrying out the recording sheet manufacturing method of the present invention.

[Application of coating material for colorant receiving layer]
As shown in FIG. 2, the support 12 delivered from the delivery device 10 is first coated with an ink absorption layer coating solution containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound by an ink absorption layer coating device 14. Is applied.

FIG. 2 shows a case where a slide coating device is used as the ink absorbing layer coating device 14, and the coating liquid is supplied to the manifold 18 formed in the coating head 16 of the slide coating device and extends in the width direction of the support 12. After being spread, it is pushed out to the slide surface 22 through the slit 20 and flows down the slide surface 22. The coating liquid flowing down the slide surface 22 forms a coating liquid bead in a gap portion between the slide surface tip and the support body 12 engaged and supported by the coating roll 24, and the support body 12 is interposed via the coating liquid bead. It is applied on top. Thereby, the ink absorption layer 3 having a coating amount of, for example, about 100 to 300 g / m ² is formed on the support 12 by coating.

  In FIG. 1, a slide coating device is used as the ink absorbing layer coating device 14, but various coating devices such as an extrusion coating device, a curtain coating device, and a bar coating device can also be used.

  Examples of inorganic fine particles used in the present invention include silica fine particles, colloidal silica, calcium silicate, zeolite, kaolinite, halloysite, muscovite, talc, calcium carbonate, calcium sulfate, boehmite, pseudoboehmite and the like. Can do. From the viewpoint of not reducing transparency, the refractive index is preferably in the range of 1.40 to 1.60. Among these, silica fine particles are particularly preferable. The average primary particle diameter of the inorganic fine particles is 20 nm or less, preferably 10 nm or less, particularly preferably 3 nm or less, and the refractive index is preferably around 1.45.

  Examples of water-soluble resins used in the present invention include, as hydrophilic structural units, resins having hydroxyl groups, such as polyvinyl alcohol (PVA), cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), Hydroxyethylcellulose (HEC), carboxymethylcellulose (CMC), etc.], chitins, and starch; resins having an ether bond, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), and polyvinylids Mention may be made of ether (PVE); and polyacrylamide (PAAM) and polyvinylpyrrolidone (PVP), which are resins having amide groups or amide bonds. In addition, as a dissociable group, polyacrylate, maleate, alginate and gelatin having a carboxyl group; polystyrenesulfonate having a sulfonic acid group, amino group, imino group, tertiary amine and fourth group Mention may be made of polyallylamine (PAA), polyethylenimine (PEI), epoxidized polyamide (EPA), polyvinylpyridine and gelatins having a quaternary ammonium salt.

  In addition, as the support 12 used in the present invention, a resin film such as WP paper or PET can be suitably used, but other high quality paper or the like may be used. A support having a width of 500 mm to 2000 mm can be suitably used.

[Quick drying of ink absorbing layer]
Next, the support 12 on which the ink absorbing layer 3 is formed is dried by the drying device 26 until the moisture content of the ink absorbing layer 3 is dried in the range of 18 to 30% by mass. Rapid drying at 1 to 3 g / m ² · sec.

By this drying, the concentration distribution of the water-soluble aluminum compound in the ink absorption layer 3 can be effectively unevenly distributed on the support 12 side. In this case, when the average drying rate is less than 1 g / m ² · sec, the water-soluble aluminum compound in the ink absorbing layer 3 is less likely to be unevenly distributed on the support 12 side. In addition, if the water-soluble aluminum compound is concentrated unevenly on the support 12 side exceeding the average drying speed of 3 g / m ² · sec, the coating strength of the ink absorbing layer 3 is lowered and the coating surface is cracked or peeled off. Or a surface failure. In addition, a binder film may be formed on the surface of the ink absorbing layer 3 and the ink absorbing ability may be reduced.

The drying device 26 may be any device that can dry at an average drying rate of 1 to 3 g / m ² · sec. For example, the hot air drying device 26 shown in the conceptual diagram of FIG. 3 is used. Can do.

  In the hot air type drying device 26 of FIG. 3, the support 12 travels from the inlet 26B side to the outlet 26C side of the drying zone 26A. The air outlets 26D and the exhaust ports 26E are alternately provided in multiple stages. A supply line for supplying hot air to the outlet 26D and an exhaust line for hot air exhausted from the exhaust port 26E are omitted.

In the case of the drying apparatus 26 as shown in FIG. 3, the average drying speed of 1 to 3 g / m ² · sec can be easily achieved by adjusting the drying conditions in the range of the hot air temperature of 50 to 120 ° C. and the drying air speed of 4 to 20 m / sec. Can be realized. In this case, it is preferable to set the drying temperature and the wind speed higher in the initial drying stage where the coating liquid is fluid, and lower in the latter half of the drying. Furthermore, by using a back surface heating method such as hot air blowing from the back surface of the support and a heat roll, the formation of the binder film can be suppressed and drying can be performed more quickly.

[Application of hardening coating solution]
Next, as shown in FIG. 2, the coating device 28 is applied onto the ink-absorbing layer 3 in the dry state within 10 seconds after the rapid drying by the coating device 28 of the hardened coating solution provided in the subsequent stage of the drying device 26. Accordingly, a hardening coating liquid for hardening the ink absorbing layer 3 is applied.

  The term “raw dry state” as used herein refers to a state in which the ink absorbing layer is applied and then dried to some extent with a hot air dryer or the like, and the fluidity of the coating film still remains.

  The term “hardening” as used herein refers to stopping the fluidity of the coating film by causing phenomena such as thickening, aggregation and hardening in the coating solution in a dry state.

Further, the technical meaning of within 10 seconds after the rapid drying is that the drying speed is set to once after leaving the drying device before the hardening coating liquid is applied to the support 12 coated with the ink absorbing layer 3. That is, it is within 10 seconds after 0.2 g / m ² · sec or less. In other words, it means that the hardening coating liquid is applied within 10 seconds after the drying is substantially stopped (drying stop time).

  Since the distribution of the water-soluble aluminum compound formed during drying is maintained as the drying stop time is shorter, the uneven distribution ratio can be increased. Therefore, it is more preferably within 5 seconds after rapid drying.

  The hardening coating liquid for hardening the ink absorbing layer 3 is not only a coating liquid containing a component that hardens by reacting with the components of the ink absorbing layer, but also changes the pH of the ink absorbing layer, for example. Thus, a coating liquid having a function of starting the hardening of the ink absorbing layer is also included.

  A typical hardening coating solution used in the present invention is a coating solution containing ammonia. Since the ink absorbing layer coating liquid mainly composed of silica fine particles and polyvinyl alcohol shows acidity, the hardening does not proceed even if it contains boric acid as a hardening agent. When a hardened coating solution containing ammonia is applied onto the ink absorbing layer while the ink absorbing layer is in a dry state, the ink absorbing layer becomes neutral, and the hardening proceeds rapidly. Of course, the hardening agent may be contained in the hardening coating solution.

Examples of the hardening agent contained in the ink absorbing layer coating solution or the hardening coating solution include boric acid and borates [for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ ], diborate [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], pentaborate [eg KB ₅ O ₈ .4H ₂ O, Ca ₂ B ₆ O ₁₁ .7H ₂ O, CsB ₅ O ₅ ], glyoxal, miramine formaldehyde [eg, methylol melamine, alkylated methylol melamine], methylol urea, resol resin, polyisocyanate, and the like. Of these, boric acid or borates are particularly preferred.

  Here, as a method for applying the film coating liquid, a method that can be applied without touching the ink absorbing layer 3 with an apparatus is appropriate. For example, an extrusion type coating apparatus, a curtain coating apparatus, etc. can be used suitably. Even a bar coater or a roll coater can be used as long as a liquid film can be formed between the ink absorption layer and substantially non-contact.

Thereby, since the ink absorption layer 3 hardens while the water-soluble aluminum compound in the ink absorption layer 3 is unevenly distributed on the support side, it can be fixed while being unevenly distributed. The required coating amount of the hardened coating solution finally applied onto the ink absorbing layer 3 is preferably in the range of 5 to 50 cc / m ² .

  In this case, if the time from the drying of the ink absorbing layer 3 to the application of the hardened coating liquid exceeds 10 seconds, the ink absorbing layer 3 is still dry and still has fluidity in the layer, so that it is water-soluble. The aluminum compound diffuses, and the uneven distribution on the support 12 side becomes insufficient.

[Smoothing / Metalling]
As shown in FIG. 2, it is preferable to adjust the coating amount by applying a smoothing / metalling treatment within 30 seconds after excessively applying the hardened coating solution onto the ink absorbing layer 3.

  Here, the smoothing and metering process will be described in detail.

  As shown in FIG. 2, immediately after application of the hardened coating solution, smoothing / metaling processing is performed by a smoothing / metaling apparatus 30 (FIG. 1 shows a bar system). In this case, it is preferable to perform the smoothing / metalling treatment with the bar 30A immediately after the application of the hardening coating solution, preferably within 30 seconds.

  Since the hardening reaction of the ink absorbing layer coating liquid generally proceeds quickly, the applied hardening coating liquid becomes unnecessary after the film has sufficiently hardened. Since unnecessary coating liquid increases the drying load in the subsequent drying apparatus 33, it is preferable to remove the coating liquid by smoothing and metalling before drying.

  As a smoothing and metering apparatus for performing the smoothing and metering process, there are a bar type and an air knife type.

  The bar method is a method in which the bar 12 is arranged in the width direction of the support 12 that travels in the axial direction of the bar of the round bar and is brought into contact with the application surface formed on the support 12. A round bar shape of 200 mm, preferably 5 to 50 mm is preferable. In addition, the bar is rotated in the same direction as the support 12 or in the opposite direction at a peripheral speed within 50% of the speed at which the support 12 travels. The wrap angle (θ) of the support 12 to the bar at this time is suitably within 0 to 30 degrees. Also, when the bar and the coating surface come into contact with each other by forming a groove between the wound wires by winding the wire etc. according to the required coating amount, or by engraving the groove in the bar itself, surplus The coating liquid is metallized by being taken into the groove.

In the air knife method, the longitudinal direction of the slot-like air nozzle that blows knife-like air is arranged in the width direction of the traveling support 12, and the knife-like air from the air nozzle is applied to the coating surface. In this method, the coated surface layer is scraped off while leveling the coated surface. The speed of air blown from the air nozzle is in the range of 10 to 150 m / sec, and the air pressure is preferably in the range of 0.01 to 10 kg / cm ² , particularly preferably in the range of 0.5 to ⁵ kg / cm ² . Further, it is preferable that the distance from the tip of the air nozzle to the uppermost application surface is set in the range of 1 to 30 mm, and the angle formed by the air nozzle and the application surface is set in the range of 1 to 50 degrees.

  However, the above conditions in the bar method and the air knife method are as follows: a) required coating amount, b) how the ink absorbing layer (lower layer) is cured by the hardened coating liquid layer (upper layer), c) ink absorbing layer coating liquid, It is further preferable to adjust within the range of the above conditions according to the composition and physical properties of the hardened coating solution, and d) the time from applying and forming the hardened coating solution to the smoothing / metalling treatment.

[Drying and winding after smoothing and metalling]
Next, the ink absorbing layer that has been subjected to the smoothing and metalling treatment (the ink absorbing layer after the application of the hardened coating solution) is dried with hot air with a wind of about 100 ° C. by the drying device 33 and dried to the product moisture of the recording sheet. Is done. Then, the support 12 dried by the drying device 33 is taken up by the winding device 34. Thereby, a recording sheet is manufactured. Reference numeral 36 denotes a guide roller that forms a travel path of the support 12.

As described above, according to the method for producing a recording sheet of the present invention, the ink is dried until the moisture content of the ink absorbing layer 3 applied and formed on the support 12 is dried in the range of 18 to 30% by mass. The absorbent layer 3 is rapidly dried at an average drying rate of 1 to 3 g / m ² · sec, and within 10 seconds after the drying, the hardened layer for hardening the ink absorbent layer 3 on the freshly dried ink absorbent layer 3 is obtained. A film-forming coating solution was applied.

  Thereby, the content of the water-soluble aluminum compound in the layer from the surface side of the ink absorbing layer 3 to the layer thickness of 30% is such that the water-soluble aluminum compound in the layer from the support side of the ink absorbing layer 3 to the layer thickness of 30%. A recording sheet that satisfies the condition of 60% or less of the content can be produced.

  In the present embodiment, the example in which the ink absorption layer is one layer has been described. However, the ink absorption layer may be formed of a plurality of layers. For example, the production method of the present invention can also be applied to a case where the ink absorption layer is composed of two layers and the concentration distribution of the water-soluble aluminum compound is increased in the lower layer close to the support side. In this embodiment, drying and winding after the smoothing / metaling process are performed. However, the smoothing / metaling process may be omitted.

  Next, examples of the present invention will be described.

[Production of support]
Wood pulp consisting of 100 parts of LBKP is beaten to 300 ml Canadian freeness with a double disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, 0.5 part of cationic polyacrylamide All the parts were added at an absolutely dry mass ratio to the pulp, and weighed with a long paper machine to make a base paper of 170 g / m ² .

In order to adjust the surface size of the base paper, 0.04% of a fluorescent whitening agent (“WhitetexBB” manufactured by Sumitomo Chemical Co., Ltd.) was added to a 4% aqueous solution of polyvinyl alcohol, and this was adjusted to a dry dry weight conversion of 0.04%. The base paper was impregnated so as to be 5 g / m ² , dried, and then subjected to calendar treatment to obtain a base paper adjusted to a density of 1.05. After the corona discharge treatment was performed on the wire surface (back surface) side of the obtained base paper, high-density polyethylene was coated to a thickness of 19 μm using a melt extruder to form a resin layer composed of a mat surface. (Hereinafter, this resin layer surface is referred to as a “back surface.” After the corona discharge treatment is further applied to the resin layer on the back surface side, aluminum oxide (“Alumina Sol 100” manufactured by Nissan Chemical Industries, Ltd.) is used as an antistatic agent. ) And silicon dioxide (“Snowtex O” manufactured by Nissan Chemical Industries, Ltd.) were dispersed in water at a mass ratio of 1: 2 so that the dry weight was 0.2 g / m ² .

  Furthermore, after the corona discharge treatment is applied to the felt surface (surface) side where the resin layer is not provided, anatase-type titanium dioxide 10%, a trace amount of ultramarine blue, and a fluorescent whitening agent 0.01% (vs. polyethylene) Low-density polyethylene containing MFR (melt flow rate) 3.8, melt-extruded to a thickness of 29 μm using a melt extruder to form a high-gloss thermoplastic resin layer on the surface side of the base paper (Hereinafter, this high-gloss surface is referred to as a “front side”), which is used as a support for this example.

[Preparation of coating liquid for ink absorbing layer]
In accordance with the composition of “silica dispersion A” below, silica fine particles, ion-exchanged water, dimethyldiallylammonium chloride polymer (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Charol DC902P) and zirconyl acetate are mixed, and liquid-liquid collision type dispersion After being dispersed by a machine (manufactured by Sugino Machine, Optimizer), the dispersion was heated to 45 ° C. and held for 20 hours to prepare silica dispersion A.

  Next, 31 parts of polyvinyl alcohol (water-soluble resin) solution A having the following composition, 0.4 part of boric acid and cation-modified polyurethane (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Superflex 650 (25% solution)) ) 2.2 parts and SC-505 (manufactured by Hymo Co., Ltd.) 0.23 parts were added at 30 ° C. to prepare a coating solution for an ink absorbing layer.

"Silica dispersion A"
(1) Silica fine particles 8.9 parts (Nippon Aerosil Co., Ltd., AEROSIL300SF75, primary particle size 7 nm)
(2) Ion-exchanged water 50 parts (3) “Charol DC-902P” (51.5% solution) 0.78 parts (Daiichi Kogyo Seiyaku Co., Ltd.)
(4) Zirconyl acetate (50% solution) 0.48 parts (Zircosol ZA-30, manufactured by Daiichi Elemental Chemical Co., Ltd.)
"Polyvinyl alcohol (water-soluble resin) solution A"
(1) Polyvinyl alcohol 2.2 parts (manufactured by Kuraray Co., Ltd., “PVA235”, saponification degree 88 mol%, polymerization degree 3500)
(2) Ion-exchanged water 28 parts (3) Diethylene glycol monobutyl ether 0.7 part (Kyowa Hakko Chemical Co., Ltd., Butisenol 20P)
(4) 0.1 part of polyoxyethylene lauryl ether (manufactured by Kao Corporation, Emulgen 109P)
[Preparation of recording sheet]
On the surface of the support 12, a coating solution obtained by in-line mixing an in-line solution containing the following water-soluble aluminum compound at a rate of 12 g / m ^{2 with} the coating solution 200 g / m ² for the ink absorbing layer obtained from the above. It applied using the coating apparatus 14 for ink absorption layers. And the moisture content of a coating layer (ink absorption layer) will be 24 mass% on the drying conditions which become the average drying speed of Examples 1-3 and Comparative Examples 1-4 which are shown in the table | surface of FIG. Until dried. Dried hardened coating solution having the following 50 g / m ² was coated with an upper layer coating device 28 into the drying downtime of Examples 1-3 and Comparative Examples 1-4 are shown in the table of FIG. 4 immediately, then 40 g / m ^{2 was} scraped off and further dried with a drying device 33 to prepare a recording sheet.

  The “drying stop time” in the table of FIG. 4 refers to the time from drying the ink absorbing layer to applying the hardened coating solution. Further, the “A” column in the “drying temperature” in the table of FIG. 4 indicates the drying temperature for drying the ink absorbing layer, and the B column indicates the drying temperature of the coating layer in which the hardened coating liquid is applied to the ink absorbing layer.

"Composition of inline liquid"
(1) Polyaluminum chloride aqueous solution 2.0 parts (Daimei Chemical Co., Ltd., Alpha-In 83)
(2) 7.8 parts of ion-exchanged water (3) SC-505 (manufactured by Haimo Co., Ltd.) 0.2 parts
"Composition of hardening coating liquid"
(1) Boric acid 1.3 parts (2) Ammonium carbonate (Kanto Chemical Co., Ltd. Grade 1) 5.0 parts (3) Zirconium ammonium carbonate (28% aqueous solution) 2.5 parts (First rare element chemical industry ( Co., Ltd., Zircosol AC-7)
(4) 90.6 parts of ion-exchanged water (5) 0.6 parts of polyoxyethylene lauryl ether (Emulgen 109P manufactured by Kao Corporation)
[Drying conditions of ink absorbing layer]
In Example 1, the ink absorption layer is dried to an undried state with a moisture content of 24% by mass at an average drying rate of 1.7 g / m ² · sec, and a hardened coating solution is applied in 5.9 seconds after drying. I did it.

In Example 2, the ink absorption layer is dried to an immediate dry state with a moisture content of 24% by mass at an average drying rate of 1.3 g / m ² · sec, and the hardened coating solution is applied in 7.7 seconds after drying. I did it.

In Example 3, the ink absorbing layer was dried to an immediate dry state having a moisture content of 24% by mass at an average drying rate of 1.0 g / m ² · sec, and the hardened coating solution was applied 10 seconds after drying. did.

In Example 4, the ink absorption layer was dried to an immediate dry state with a moisture content of 24% by mass at an average drying rate of 3.0 g / m ² · sec, and the hardened coating solution was applied 10 seconds after drying. did.

In Comparative Example 1, the ink absorbing layer is dried to an immediate dry state having a moisture content of 24% by mass at an average drying rate of 1.0 g / m ² · sec, and the film-hardening coating solution is applied 15 seconds after drying. did.

In Comparative Example 2, the ink absorbing layer was dried to an immediate dry state with a moisture content of 24% by mass at an average drying rate of 0.5 g / m ² · sec, and the hardened coating solution was applied 10 seconds after drying. did.

In Comparative Example 3, the ink absorbing layer was dried to an immediate dry state having a moisture content of 24% by mass at an average drying rate of 1.7 g / m ² · sec, and the hardened coating solution was applied 30 seconds after drying. did.

In Comparative Example 4, the ink absorbing layer was dried to an immediate dry state with a moisture content of 24% by mass at an average drying rate of 2.1 g / m ² · sec, and the hardened coating solution was applied 30 seconds after drying. did.

[Evaluation method of produced recording sheet]
About the recording sheet produced on the conditions of the said Examples 1-4 and Comparative Examples 1-4, the distribution state of the water-soluble aluminum compound, high-humidity bleeding, ink absorptivity, and black Dm were evaluated.

  The evaluation results are shown in the table of FIG.

  The evaluation item “Al distribution” is the weight ratio of the water-soluble aluminum compound to the silica having a layer thickness of 30% from the surface side of the coating layer) / (water-soluble aluminum to the silica having a layer thickness of 30% from the support side of the coating layer). Compound weight ratio).

  The evaluation item “high-humidity bleeding” was visually evaluated after 14 days of processing in an environment of 23 ° C. and 90% humidity in a sealed state after printing an image with PM-A700. The case where there was no bleeding was rated as “◯”, the case where there was a slight amount of bleeding as “Δ”, the case where there was a large amount of bleeding as “×”, and the case where “◯” or more was rated as “Pass”.

  As an evaluation item, “ink absorbability” was evaluated by printing black on an EPSON PX-5500 in an environment of a temperature of 23 ° C. and a humidity of 80% to evaluate the ink absorbency. A case where the ink absorptivity was good was evaluated as ◯, a case where the ink absorptivity was inferior was evaluated as Δ, a case where the ink absorptivity was considerably inferior was evaluated as x, and a case where the ink absorptivity was excellent was evaluated as pass.

  The evaluation item “Black Dm” was printed with EPSON PM-A700 to measure the density. And less than 2.20 was set to x, 2.20 to 2.29 was set to (triangle | delta), 2.3 or more was set to (circle), and (triangle | delta) or more was set to pass.

[Evaluation results]
As can be seen from the table in FIG. 4, the recording sheets of Examples 1 to 4 in which the method for producing a recording sheet of the present invention was carried out had high-humidity bleeding and ink absorptivity, and “black Dm”. Was over Δ.

  In the recording sheets produced by the production methods of Examples 1 to 4, the concentration distribution of the water-soluble aluminum compound was unevenly distributed on the support side. That is, the “Al distribution” was 47 to 59% and 60% or less. This is because a recording sheet having an “Al distribution” of 60% or less can be manufactured by carrying out the recording sheet manufacturing method of the present invention. This recording sheet has “high-humidity bleeding”, “ink absorbability”. "Black Dm" is superior to the conventional recording sheet.

On the other hand, “the average drying speed of the ink absorbing layer is 1 to ² g / m ² · sec” which is an essential requirement of the present invention, and “the hardened coating liquid is applied within 10 seconds after the ink absorbing layer is dried”. In Comparative Examples 1 to 4 that do not satisfy at least one of the two requirements, high-humidity bleeding and ink absorbency are Δ to ×, and “Black Dm” is all ×, and overall evaluation is poor. It was an evaluation.

  The “Al distribution” of the recording sheets produced by the production methods of Comparative Examples 1 to 4 was 65 to 78%, which exceeded 60%.

  DESCRIPTION OF SYMBOLS 10 ... Delivery apparatus, 12 ... Support body, 14 ... Coating apparatus for ink absorption layer, 24 ... Coating roll, 26 ... Drying apparatus, 28 ... Coating apparatus for upper layer, 30 ... Bar type smoothing and metering apparatus, 33 ... Drying Device 34 ... Winding device

Claims (3)

An ink absorption layer containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound is provided on the support, and the concentration distribution of the water-soluble aluminum compound in the ink absorption layer is unevenly distributed on the support side. In the recording sheet,
The content of the water-soluble aluminum compound in the surface side layer from the surface side of the ink absorption layer to the layer thickness of 30% is such that the water-soluble aluminum in the support side layer from the support side of the ink absorption layer to the layer thickness of 30%. A recording sheet having a compound content of 60% or less. An ink absorption layer containing inorganic fine particles, a water-soluble resin, and a water-soluble aluminum compound is provided on the support, and the concentration distribution of the water-soluble aluminum compound in the ink absorption layer is unevenly distributed on the support side. In the manufacturing method of the recording sheet,
A first coating step of coating a coating liquid for an ink absorbing layer on the belt-like support that runs continuously;
Rapid drying of the ink absorbing layer at an average drying rate of 1 to 3 g / m ² · sec until the moisture content of the ink absorbing layer applied and formed on the support is dried to a range of 18 to 30% by mass. A drying process;
A second coating step of coating a hardened coating solution for hardening the ink absorbing layer on the freshly dried ink absorbing layer within 10 seconds after the rapid drying. A method for producing a recording sheet.   The content of the water-soluble aluminum compound in the layer from the surface side of the ink absorption layer to a layer thickness of 30% is the content of the water-soluble aluminum compound in the layer from the support side of the ink absorption layer to a layer thickness of 30%. The method for producing a recording sheet according to claim 2, wherein the recording sheet is 60% or less.

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