JP2010240560A - Method and apparatus of manufacturing recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve ink absorbency and glossiness of an ink absorbing layer by preventing the concentration and uneven distribution of the concentration distribution of a water-soluble resin on the surface of the ink absorbing layer when drying the ink absorbing layer. <P>SOLUTION: In the method of manufacturing a recording sheet for applying and forming the ink absorbing layer including inorganic fine particles and the water-soluble resin on a continuously running belt-like support 12, then applying a film-hardening coating liquid for hardening the ink absorbing layer onto the ink absorbing layer dried into a half-dry state and drying it; as a drying apparatus for drying the ink absorbing layer into the half-dry state, a hot air drying means 46 is used together with a microwave drying means 48 for heating and drying the ink absorbing layer from the inside. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing a recording sheet, and in particular, an ink absorbing layer which is dried in a freshly dried state after coating and forming an ink absorbing layer containing inorganic fine particles and a water-soluble resin on a continuously running belt-like support. The present invention relates to a technique for drying an ink absorbing layer in the production of a recording sheet in which a hardened coating liquid for hardening the ink absorbing layer is applied onto the layer and dried.

  Currently, various ink jet methods have been developed, and various ink jet recording sheets have been developed accordingly. Among these recording sheets for inkjet, a recording sheet provided with an ink absorbing layer containing fine inorganic particles and a water-soluble resin is a high-quality inkjet recording sheet (hereinafter referred to as “high quality”). Used as a recording sheet). Other recording sheets provided with an ink absorbing layer containing inorganic fine particles and a water-soluble resin include thermal transfer recording sheets and electrophotographic recording sheets.

  As a method for producing this high-quality recording sheet, the present applicant has proposed the method for producing an inkjet recording sheet of Patent Document 1. In this method, an ink absorption layer containing inorganic fine particles and a water-soluble resin is applied and formed on a support, and then the ink absorption layer is dried by a hot-air drying method to dry it to a dry state. Then, a hardened coating solution for hardening the ink absorbing layer is applied onto the ink absorbing layer in a dry state.

JP 2004-275998 A

  The method of Patent Document 1 can be rapidly dried using a general hot air dryer as compared with the conventional method in which the ink absorbing layer is applied and then cooled once and then dried at a temperature of 50 ° C. or lower. .

  However, in order to further increase the drying speed, increasing the drying temperature or drying air speed until the ink absorbing layer is dried to the dry state causes the surface of the coating layer to shrink, thereby causing deterioration of the surface state or the ink absorbing layer. There is a problem that the water-soluble resin as a constituent component of the ink concentrates on the surface of the layer and the absorbability of the ink deteriorates.

  The surface shrinkage of the coating layer and the deterioration of the ink absorbency are caused by setting the hot air temperature to 80 ° C. or higher in order to dry the ink absorbing layer quickly, and drying the ink absorbing layer at a temperature of 40 ° C. or higher. Become prominent.

  The present invention has been made in view of such circumstances, and suppresses shrinkage and cracking of the coating layer surface and concentration of the water-soluble resin layer surface during drying of the ink absorption layer. An object of the present invention is to provide a recording sheet manufacturing method and apparatus capable of improving the deterioration of the absorbability of the recording sheet.

  According to a first aspect of the present invention, in order to achieve the above-mentioned object, the ink absorbing layer which is dried in a freshly dried state after coating and forming an ink absorbing layer containing inorganic fine particles and a water-soluble resin on a continuously running belt-like support. In the method for producing a recording sheet, wherein the ink absorbing layer is cured by applying a film-forming coating liquid for hardening the ink absorbing layer on the layer, and drying the ink absorbing layer in a dry state. There is provided a method for producing a recording sheet, characterized by using at least microwave drying that heats and dries from the inside.

  Here, using at least microwave drying means that a drying method other than microwave drying such as hot air drying may be used in combination. The raw dry state of the ink absorbing layer refers to a state where the drying has been progressed halfway after application, and the moisture content (indicated by water / mass% of solid content) is in the range of 200 to 600%. More preferably, it is in the range of 500%, particularly preferably in the range of 250-450%.

  Inventors of the present invention apply various drying methods in the production of a recording sheet in which a hardened coating liquid for hardening the ink absorbing layer is applied onto an ink absorbing layer dried in a dry state. Among them, the present inventors have found that there is a good relationship between the microwave drying method and the prevention of uneven distribution during drying of the water-soluble resin constituting the ink absorption layer, and the present invention has been made based on such knowledge. .

  According to claim 1 of the present invention, when the ink absorbing layer is dried in a raw dry state, at least microwave drying of an internal heating system in which moisture is dried by heating from the inside of the ink absorbing layer is used. This makes it possible to perform uniform heating in the thickness direction of the ink absorbing layer, unlike an external heating method in which the ink absorbing layer is heated from the outside, such as conventional hot air drying. Moreover, the temperature of the ink absorption layer surface can be made lower than that of the outside heating method.

  Thereby, when drying an ink absorption layer, the shrinkage | contraction of the surface of an application layer and the layer surface concentration of the water-soluble resin which is a structural component of an ink absorption layer can be suppressed. As a result, the surface shape and ink absorbability can be improved as compared with the case of drying by the conventional external heating method.

  In the production method of the present invention, it is preferable to use hot air drying in combination with the microwave drying. Thereby, drying time can be shortened, suppressing the shrinkage | contraction and crack of the surface of an application layer, and the layer surface concentration of water-soluble resin.

  The production method of the present invention is extremely effective when the support is resin-coated paper. For example, as in the case of microwaves, when a far-infrared drying apparatus capable of heating from the inside is used, the resin is softened with resin-coated paper, and a large amount of energy cannot be applied to the coating layer. However, when microwaves are used, it is possible to give a larger energy to the coating layer as compared with the far-infrared dryer without softening the support resin, and the drying speed can be increased.

  According to a fourth aspect of the present invention, in order to achieve the above object, the ink absorption layer which is dried in a freshly dried state after coating and forming an ink absorbing layer containing inorganic fine particles and a water-soluble resin on a continuously running belt-like support. In a recording sheet manufacturing apparatus for applying a film-forming coating liquid for hardening the ink absorbing layer on the layer and drying the recording sheet, the ink absorbing layer is used as a drying apparatus for drying the ink absorbing layer in a dry state. There is provided a recording sheet manufacturing apparatus provided with at least microwave drying means for drying by heating from the inside.

  Claim 6 constitutes the present invention as an apparatus.

  In the manufacturing apparatus of the present invention, the microwave drying means is disposed on the side of the support opposite to the ink absorbing layer, and the hot air drying means is disposed on the ink absorbing layer side of the support, and the microwave drying means includes the It is preferable to dry using hot air drying means in combination.

  In the manufacturing apparatus of the present invention, a temperature distribution measuring means for measuring the temperature distribution in the width direction of the support is provided, and a plurality of the microwave drying means are arranged in the width direction of the support, and the temperature distribution measurement is performed. It is preferable to provide control means for controlling the microwave irradiation amount of the plurality of microwave drying means so that the temperature distribution is eliminated based on the temperature distribution measured by the means.

  In the production of the recording sheet of the present invention, a hardened coating solution for hardening the ink absorbing layer is applied on the ink absorbing layer in the dry state, but the dried state in the width direction of the support is uniform. is important. This is because if the raw dry state in the width direction of the support is not uniform, the progress of the hardening reaction will not match, and the degree of hardening will vary, making it impossible to produce a product of uniform quality.

  However, in the present invention, the microwave irradiation amount irradiated in the width direction of the support is controlled to eliminate the temperature distribution in the width direction of the support, so that the dry state in the width direction of the support becomes uniform. In this case, the microwave drying has an advantage that it is easy to control a plurality of drying means with higher accuracy than other drying means such as hot air drying.

  According to the recording sheet manufacturing method and apparatus of the present invention, at least microwave drying is used for drying the ink absorbing layer, so that shrinkage and cracking of the surface of the coating layer and layer concentration of the water-soluble resin can be suppressed. . Thereby, since the surface of the ink absorption layer is not formed into a film by the water-soluble resin, the surface shape and the ink absorbability can be improved as compared with the case of drying by an external heating method such as conventional hot air drying.

The conceptual diagram which shows the whole structure of the manufacturing apparatus of the recording sheet of this invention Schematic diagram when using hot air drying means in combination with microwave drying means as a drying device Conceptual diagram with a control mechanism that equalizes the temperature distribution in the width direction of the support in the microwave drying means Explanatory drawing of an Example

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

  FIG. 1 is a conceptual diagram showing an example of the entire configuration of a recording sheet manufacturing apparatus according to the present invention.

[Application of coating liquid for ink absorbing layer]
As shown in FIG. 1, the support 12 delivered from the delivery device 10 is first coated with an ink absorption layer coating solution containing inorganic fine particles and a water-soluble resin by an ink absorption layer coating device 14.

FIG. 1 shows a case where a slide coating apparatus is used as the ink absorbing layer coating apparatus 14, and the coating liquid is supplied to a manifold 18 formed in the coating head 16 of the slide coating apparatus so as to extend 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, an ink absorption layer having a coating amount of, for example, about 100 to 300 g / m ² is formed on the support 12.

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

  Further, as the support 12 used in the present invention, a resin film such as WP paper or PET, a resin-coated paper, or the like can be suitably used. However, the present invention may cause the resin to melt when dried at high temperature. This is particularly effective when certain resin-coated paper is used. A support having a width of 500 mm to 2000 mm can be suitably used.

[Drying of ink absorbing layer]
Next, the support 12 on which the ink absorbing layer is formed travels in the drying zone 26A of the drying device 26, and the ink absorbing layer is dried in a dry state. Here, the raw dry state of the ink absorbing layer means that the moisture content (indicated by water / mass% of solid content) is in the range of 200 to 600%, more preferably in the range of 200 to 500%. It is particularly preferable that it is in the range of -450%.

  In the recording sheet manufacturing apparatus of the present invention, at least an internal heating type microwave drying apparatus that heats and drys the ink absorption layer from the inside of the ink absorption layer is provided as the drying apparatus 26 that dries the ink absorption layer to a freshly dried state. I made it.

  When drying the ink absorption layer to the dry state, at least using microwave drying that heats from the inside of the ink absorption layer to dry the moisture, the shrinkage and cracking of the coating layer surface is suppressed, and the ink absorption layer It is possible to prevent the concentration distribution of the water-soluble resin as a constituent component from being concentrated on the surface of the ink absorbing layer and being unevenly distributed. As a result, the surface state and ink absorbability of the ink absorbing layer can be improved as compared with a conventional external heating type drying apparatus such as hot air drying.

  FIG. 2 is a conceptual diagram of the drying device 26 in which hot air drying means is used in combination with microwave drying means.

  As shown in FIG. 2, the drying device 26 includes a device main body 42 in which an inlet 38 and an outlet 40 of the support 12 having an ink absorbing layer applied and formed on the surface (the upper surface of the support in FIG. 2), and a support. A plurality of pass rollers 44, 44... That support the running of the body 12, a hot air drying means 46 that blows hot air on the ink absorbing layer, and a back surface side of the support 12. And microwave drying means 48 for irradiating the body 12 with microwaves.

  The hot air drying means 46 is provided with a blowing chamber 50 having a large number of outlets 46A, 46A... On the surface side of the support 12, and this blowing chamber 50 is connected to a hot air generator (not shown) via a hot air supply duct 52. Connected. As a result, the hot air supplied from the hot air supply duct 52 to the blowout chamber 50 is equalized in the blowout chamber 50 and blown out from the blowout port 46A toward the ink absorbing layer. Therefore, the surface of the ink absorption layer is mainly heated. In addition, the said structure of the hot air drying means 46 is an example, and if it is a drying means by a hot air, another structure can also be employ | adopted for it.

  Further, the microwave drying means 48 is provided with a microwave generation part 48 </ b> A between the pass rollers 44, and a microwave of 2.45 GHz is irradiated on the back surface side of the support 12. The solvent (moisture) of the ink absorption layer vibrates and generates heat due to the irradiated microwave, thereby heating from the inside of the ink absorption layer. Although not shown, it is preferable to provide a microwave stirrer between the microwave generator 48 </ b> A and the support 12 so that the microwave irradiation amount applied to the support 12 is uniform. The above-described configuration of the microwave drying means 48 is merely an example, and another configuration may be adopted as long as it is a microwave drying means.

  By using the hot air drying means 46 in combination with the microwave drying means 48 as described above, the ink absorption layer is uniformly heated from the inside by the microwave drying means 48, while moisture evaporation on the surface portion of the ink absorption layer is promoted by hot air drying. Can be made. The hot air containing the evaporated water is exhausted from the apparatus main body 42 through an exhaust duct 54 communicating with the apparatus main body 42.

  Thereby, drying time can be shortened compared with the case of only microwave drying, preventing film-forming with the water-soluble resin on the surface of an ink absorption layer.

  In the method for producing a recording sheet of the present invention, a hardened coating liquid for hardening the ink absorbing layer is applied on the ink absorbing layer in a dry state. Uniformity is important. This is because if the state of raw drying in the width direction of the support is not uniform, the progress of the hardening reaction will not match, and the degree of hardening will vary.

  As a drying means for making the raw dry state in the width direction of the support uniform, the internal heating type microwave drying means 48 is more advantageous than the external heating type hot air drying means. This is because the microwave drying means 48 can control the drying capability with high accuracy by adjusting the microwave irradiation amount in the width direction of the support.

  FIG. 3 shows an example in which a plurality of temperature sensors 64 and a plurality of microwave generators 48A are arranged in the support width direction, so that the raw dry state of the ink absorption layer can be made uniform in the support width direction. It is. FIG. 3 is a top view of the support 12 as viewed from above, and a broken line indicates that the support 12 is disposed on the back side of the support 12. The signal cable is also indicated by a broken line.

  As shown in FIG. 3, a plurality (three in FIG. 3) of non-contact temperature sensors 64, 64... Are arranged in the support body width direction and connected to the control means 68 via the signal cable 66. Thereby, the surface temperature of the ink absorption layer measured by the plurality of temperature sensors 64 is sequentially input to the control means 68, and the temperature distribution in the support width direction of the ink absorption layer is monitored.

  A plurality (three in FIG. 3) of microwave generators 48 </ b> A are arranged in the support width direction and connected to the control means 68 via the signal cable 70. And the control means 68 adjusts the microwave irradiation amount of each microwave generation part 48A so that a temperature distribution may be eliminated based on the temperature distribution calculated | required by the several temperature sensor 64. FIG. Thereby, the raw dry state in the support width direction of the ink absorption layer can be made uniform with high accuracy.

[Application of hardening coating solution]
Next, as shown in FIG. 1, the coating apparatus 28 disposed on the outlet side of the drying apparatus 26 applies wet-on-wet coating liquid for hardening the ink absorbing layer. Excessive application.

  The hardening coating liquid for hardening the ink absorbing layer 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 example of the dural 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 hard film 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 hard film advances rapidly. Of course, the hardening agent may be contained in the hardening coating solution.

The required coating amount of the hardened coating solution finally applied onto the ink absorbing layer is preferably in the range of ^{2 to} 100 cc / m ² .

Examples of the hardening agent contained in the hardening coating solution used in the present invention 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, resole resin, polyisocyanate, and the like. Of these, boric acid or borates are particularly preferred.

  Various coating devices such as an extrusion coating device, a curtain coating device, and a bar coating device can be used as the coating device 28 for coating the hardening coating solution, but an extrusion type is particularly preferable.

[Smoothing / Metalling]
Next, as shown in FIG. 1, after excessively applying the hardened coating solution onto the ink absorbing layer, smoothing and metalling treatment is performed within 30 seconds to adjust the coating amount and smooth the coating film surface. It is preferable to do.

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

  As shown in FIG. 1, immediately after application of the hardened coating solution, smoothing and metering is performed by a smoothing and metering device 30 (shown in FIG. 1 in 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. As a result, the poor surface state of the lower ink absorbing layer and the deterioration of the surface state due to foam failure of the hardened coating liquid layer (coating failure such as streaks and unevenness) are repaired. A coated surface having a good and high glossiness can be formed.

  Examples of the smoothing and metering apparatus for performing the smoothing and metering process include a bar method and an air knife.

  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, as shown in FIG. 1, the smoothed and metalized coating layer (ink absorbing layer after coating with the hardened coating solution) is dried by a dryer 33 with hot air of about 180 ° C., and the product moisture of the recording sheet. And is wound on 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 recording sheet manufacturing method of the present invention, the microwave drying means 48 is used at least as the drying means for drying the ink absorption layer. It is possible to prevent the concentration distribution of a certain water-soluble resin from being concentrated on the surface of the ink absorption layer and becoming unevenly distributed. Thereby, the ink absorptivity and glossiness of the ink absorbing layer can be improved as compared with the case of drying by an external heating method such as conventional hot air drying.

  In the embodiment of the present invention, the smoothing and metering device 30 is provided. However, the smoothing and metering device 30 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]
The ink absorbing layer coating solution is applied to a support having a width of 1000 mm by a slide bead coating method, and the moisture content of the coating layer is 24% by mass under the following drying conditions (Examples 1 to 3 and Comparative Example 1). After drying, a hardened coating solution was applied at 50 g / m ² , then scraped off at 40 g / m ² and further dried to prepare a recording sheet.

[Drying conditions of ink absorbing layer]
In Example 1, the microwave drying means 48 installed on the side of the support 12 opposite to the coating surface is irradiated with microwaves and the irradiation output is adjusted. It was dried and dried so that the water content was 24% by mass. At this time, 30 ° C. dry air was sent from the outlet 46A of the hot air drying means 46 installed on the coating surface side (ink absorption layer side) of the support 12 and exhausted from the exhaust duct 54, thereby containing evaporated water. Air was ventilated. The wind speed of the dry air was 4 m / sec.

  In Example 2, the drying air temperature of the hot air drying means 46 was set to 60 ° C., and the wind speed of the drying air was set to 10 m / sec. In addition, the microwave drying means 48 installed on the side of the support 12 opposite to the coating surface is irradiated with microwaves, and the irradiation power is adjusted so that the coating layer moisture content in the center portion in the width direction of the support is 30 seconds. Of 24 mass%.

  In Example 3, the microwave drying means 48 is divided into six parts in the width direction of the support and installed, and an infrared moisture meter is installed at a position immediately before coating to apply the hardened coating solution, thereby providing ink in the width direction of the support. The moisture content of the absorption layer was measured. Then, the output was adjusted for each of the microwave drying means 48 divided into six based on the measurement results so that the moisture content of the coating layer was uniform at 24% by mass over the entire width of the support. Other conditions are the same as in the second embodiment.

  In Comparative Example 1, only the hot air drying means 46 is used, the drying air temperature is set to 100 ° C., and drying is performed for 30 seconds so that the moisture content of the coating layer in the central portion in the width direction of the support becomes 24% by mass. did.

[Surface shape evaluation of the prepared recording sheet]
About the recording sheet produced in Example 1, Example 2 and Comparative Example 1 having different drying conditions, the coated surface was visually observed to evaluate whether surface deterioration due to shrinkage or cracking occurred. . The ink absorptivity was evaluated by using a PX-5500 manufactured by EPSON and printing black ink on a recording sheet in an environment of a temperature of 23 ° C. and a humidity of 80%.

[Evaluation results]
The evaluation results of the recording sheets prepared under the drying conditions of Examples 1 to 3 and the drying condition of Comparative Example 1 are shown in the table of FIG. In the table, the evaluation item “applied surface” indicates that the coating layer has no surface shrinkage or cracks, and x indicates that the coating layer has surface shrinkage or cracks. In addition, ○ of “ink absorbability” means that the ink absorbency is good, and × means that the ink absorbability is bad.

  As can be seen from the table of FIG. 4, the recording sheet produced by the drying method of the present invention was evaluated as “good” for both “applied surface” and “ink absorbability”.

  On the other hand, Comparative Example 1 in which only the hot air drying means 46 was used was evaluated as x for both “applied surface shape” and “ink absorbability”.

  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 of hardening coating liquid, 30 ... Bar type smoothing and metering apparatus 34 ... Winding device, 46 ... Hot air drying means, 46A ... Air outlet, 48 ... Microwave drying means, 50 ... Blowing chamber, 52 ... Hot air supply duct, 54 ... Exhaust duct, 64 ... Temperature sensor, 68 ... Control means

Claims (6)

A dura film in which an ink absorption layer containing inorganic fine particles and a water-soluble resin is applied and formed on a continuous belt-like support, and then the ink absorption layer is hardened on the ink absorption layer dried to a dry state. In the manufacturing method of the recording sheet which applies and dries the coating liquid,
A method for producing a recording sheet, wherein the drying step of drying the ink absorbing layer in a dry state uses at least microwave drying that heats and dries from the inside of the ink absorbing layer.   The method for producing a recording sheet according to claim 1, wherein hot-air drying is used in combination with the microwave drying.   The method for producing a recording sheet according to claim 1, wherein the support is resin-coated paper. A dura film in which an ink absorption layer containing inorganic fine particles and a water-soluble resin is applied and formed on a continuous belt-like support, and then the ink absorption layer is hardened on the ink absorption layer dried to a dry state. In an apparatus for manufacturing a recording sheet that is coated with a coating liquid and dried,
An apparatus for producing a recording sheet, characterized in that at least microwave drying means for drying by heating from the inside of the ink absorbing layer is provided as a drying device for drying the ink absorbing layer in a raw dry state.   The microwave drying means is disposed on the side of the support opposite to the ink absorbing layer, the hot air drying means is disposed on the ink absorbing layer side of the support, and the hot air drying means is used in combination with the microwave drying means. The recording sheet manufacturing apparatus according to claim 4, wherein the recording sheet is dried. While providing temperature distribution measuring means for measuring the temperature distribution in the width direction of the support, a plurality of the microwave drying means is arranged in the width direction of the support,
5. The control means for controlling the microwave irradiation amount of the plurality of microwave drying means so as to eliminate the temperature distribution based on the temperature distribution measured by the temperature distribution measuring means. 5 recording sheet manufacturing apparatus.

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