JP2009298662A - Porous spherical particle, method for producing the same, and coating liquid for forming ink receiving layer containing the porous spherical particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid for forming an ink receiving layer which allows printing without a blur, printing with uniform density, and clear printing, and to provide porous spherical particles to be blended with the coating liquid. <P>SOLUTION: The porous spherical particles comprise 100 parts by mass of aluminum hydroxide particles having an average particle size in the range of 10-300 nm and 0.1 to 20 parts by mass of bio cellulose and have an average particle size in the range of 1-100 μm and a pore volume in the range of 0.5-3.0 ml/g. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a coating solution for forming an ink-receiving layer on a resin film sheet such as PET or vinyl chloride, paper, steel plate, cloth, and the like. And a coating liquid for forming an ink-receiving layer capable of obtaining a printed matter that can be printed vividly and is excellent in water resistance, weather resistance, and color fading, and having sufficient strength. .
The present invention also relates to porous spherical particles blended in the ink receiving layer forming coating solution and a method for producing the same.

  Inkjet printing enables printing with the same image quality as conventional multicolor printing and color photographic printing, and is easy to increase in speed and multicoloring. Because of its low cost, it is becoming widespread in various applications.

  Conventionally, when printing by an ink jet method, a recording sheet in which a water-soluble polymer such as polyvinyl alcohol is coated on a sheet to form a receiving layer has been used, and printing with water-based ink has been performed. Since it uses water, it has no water resistance, and there is a problem that the image quality deteriorates in a high humidity environment or when wet. Further, the ink absorbability is not sufficient, and there is a problem that a clear and highly accurate image cannot be obtained.

In order to solve these problems, a recording sheet has been proposed in which an ink receiving layer containing a water-soluble polymer and fine particles such as silica and alumina is formed on the surface of a substrate. For example, Japanese Patent Application Laid-Open No. 62-149475 [Patent Document 1] describes that the use of spherical particles having an average particle diameter of 1 to 50 μm can improve the ink absorbency without impairing the image quality. .
Japanese Patent Publication No. 3-24906 [Patent Document 2] describes that a recording medium having a receiving layer containing a porous cationic hydrated aluminum oxide is suitable for printing with a water-soluble dye ink. Has been.
Japanese Patent Publication No. 4-19037 [Patent Document 3] describes that a recording medium having a receiving layer containing cationic colloidal silica is suitable for printing with a water-soluble dye ink.
Japanese Patent Publication No. 4-115984 [Patent Document 4] describes a recording sheet in which a layer made of porous silica is provided on a layer made of pseudoboehmite alumina.
JP-A-6-55829 [Patent Document 5] discloses porous silica particles having an average particle diameter of 2 to 50 μm, an average pore diameter of 8 to 50 nm, and a pore volume of 0.8 to 2.5 cc / g. A recording sheet having a porous layer containing alumina or alumina hydrate on the upper layer is formed.

Further, the ink receiving layer has been required to be further improved in terms of color developability and bleeding prevention.
In Japanese Patent Application Laid-Open No. 2003-11494 [Patent Document 6], an inkjet image-receiving body provided with an ink image-receiving layer on at least one surface of a support layer was pulverized by freeze-pulverized bacterial cellulose I and a high-pressure emulsifier. An invention relating to a method for providing an ink image-receiving layer containing at least one selected from the group consisting of bacterial cellulose II and a water-soluble soybean polysaccharide is described, and such an image receptor for inkjet printing has color development and bleeding prevention. It is described that is effective.
However, with the increase in the speed of inkjet printing and the like, further improvements are required in terms of color development and prevention of bleeding.

Japanese Patent Laid-Open No. Sho 62-149475 Japanese Patent Publication No. 3-24906 Japanese Patent Publication No. 4-19037 Japanese Examined Patent Publication No. 4-115984 JP-A-6-55829 JP 2003-11494 A

The present invention has been made to solve the above-described problems of the prior art, and is capable of being printed with no blurring, uniform density, and clearness during printing, and An object of the present invention is to provide a coating liquid for forming an ink-receiving layer that is excellent in water resistance and can obtain a printed material having sufficient strength.
Another object of the present invention is to provide a porous spherical particle to be blended in the ink receiving layer forming coating solution and a method for producing the same.

The porous spherical particles of the present invention include 100 parts by weight of aluminum hydroxide particles having an average particle diameter in the range of 10 to 300 nm and 0.1 to 20 parts by weight of biocellulose, and the average particle diameter is in the range of 1 to 100 μm. The pore volume is in the range of 0.5 to 3.0 ml / g.
In the method for producing porous spherical particles of the present invention, a dispersion of aluminum hydroxide particles having an average particle diameter in the range of 10 to 300 nm (in terms of solid content) and a biocellulose dispersion of 0.1 to 20 mass are used. Part (solid content conversion) is mixed to prepare a mixed solution, and the mixed solution is spray-dried.

The coating liquid for forming an ink receiving layer of the present invention comprises 100 parts by mass of the porous spherical particles (in terms of solid content), 5-60 parts by mass of the binder (in terms of solid content), and 150-1500 parts by mass of the solvent. To do.
The recording sheet with an ink-receiving layer of the present invention is characterized by having an ink-receiving layer formed on the base material using the ink-receiving layer-forming coating solution.

The ink receiving layer to which the coating liquid for forming an ink receiving layer according to the present invention is applied has an excellent ink absorption rate and suppresses the occurrence of bleeding. The ink receiving layer is also excellent in strength and water resistance.
For this reason, according to the coating liquid for forming an ink receiving layer according to the present invention, the ink receiving layer with an ink receiving layer that is excellent in printing characteristics even when printing is performed using various inks regardless of the printing method. A recording sheet is obtained. In particular, a recording sheet with an ink-receiving layer suitable as a recording sheet for white PET, art paper, etc. for large color printers can be obtained. In addition, a recording sheet with an ink receiving layer that can be printed at high speed by a printer is obtained.

1. Porous spherical particles The porous spherical particles according to the present invention include 100 parts by mass of aluminum hydroxide particles having an average particle diameter in the range of 10 to 300 nm and 0.1 to 20 parts by mass of biocellulose, and the average particle diameter is 1. It is characterized by being in the range of -100 μm and the pore volume in the range of 0.5-3.0 ml / g.

The porous spherical particles according to the present invention are mainly intended to be used mainly as a component of the ink receiving layer. Aluminum hydroxide particles and biocellulose have been selected as suitable raw materials to achieve this purpose.
Aluminum hydroxide particles are fine particles of aluminum hydroxide (also referred to as alumina hydrate), have high transparency, and can impart excellent color developability when used as a component of an ink receiving layer. Therefore, it is preferably used.

If the average particle diameter of the aluminum hydroxide particles is less than 10 nm, it is not preferable because the aluminum hydroxide particles do not have a pore volume that can exhibit sufficient ink absorbability. Moreover, when the average particle diameter exceeds 300 nm, the transparency fall of aluminum hydroxide particle itself becomes remarkable. For this reason, when it is applied to the porous spherical particles of the present invention and used as a component of the ink receiving layer, the color developability of the ink on the substrate with the ink receiving layer is lowered, which is not desirable.
The aluminum hydroxide particles may be crystalline particles or amorphous particles. In the case of crystalline particles, it is desirable that the crystal water is 1 mol or more per 1 mol of Al ₂ O ₃ .

  Biocellulose is highly crystalline, has an ultrafine structure with a uniform width, and has a high degree of weight average polymerization compared to conventional vegetable cellulose. Therefore, when dispersed in water, it is highly viscous and excellent in suspension stability. Hereinafter, biocellulose will be described in detail.

Biocellulose is also called bacterial cellulose, and means, for example, cellulose produced by culturing microorganisms such as acetic acid bacteria. The majority of plant cellulose is produced by higher plants, but cellulose produced by microorganisms other than plants is called biocellulose (or bacterial cellulose). As for biocellulose, for example, one type of acetic acid bacteria produces a gel-like cellulose film on the surface of the medium when cultured. Such biocellulose has different properties from plant cellulose.
The difference between biocellulose and plant cellulose is in its microstructure. Plant cellulose is known to have many cellulose molecular chains converged to form fine fibers called microfibrils, and these microfibrils converge to form higher-order structures step by step from the fibrils. .

On the other hand, biocellulose is a cellulose-like microfibril that is secreted from fungal cells and forms a net-like structure as it is, and is generally ribbon-like with a thickness of 1 to 20 nm and a width of 10 nm to 1 μm. It has a microfibril structure. Usually, it is gel-like and the water content is 95% (w / v) or more.
The structure of biocellulose includes cellulose and a heteropolysaccharide having cellulose as a main chain, or includes glucan. Components other than cellulose in the case of containing a heteropolysaccharide are hexoses such as mannose, fructose, galactose, xylose, arabinose, rhamnose or glucuronic acid, pentoses or organic acids. In addition, about these polysaccharides, a single substance may be sufficient and 2 or more types of polysaccharides may be mixed by the hydrogen bond etc. Any biocellulose can be used as long as it is as described above.

  In addition to a purified product separated from a culture of microorganisms, biocellulose may contain impurities to some extent depending on the application. For example, residual saccharide, yeast extract, etc. in the culture solution may remain microbial cellulose. Moreover, the microbial cell may be contained to some extent.

  The microorganism that produces such biocellulose is not particularly limited. For example, Acetobacteraceti subsp / xylinum ATCC 10821 or A. pasteurianus, A. rancens, Sarcina ventriculi, Bacterium xyloides), Pseudomonas bacteria, Agrobacterium bacteria and the like.

  Regarding the biocellulose to be applied to the present invention, commercially available products may be applied as they are, or the biospherical fibers are prevented from sticking so that the porous spherical particles can be uniformly dispersed in the coating liquid for forming the ink receiving layer. In addition, the gel-like biocellulose may be finely pulverized into a slurry, or may be dried to a powder form and then applied to the production method according to the present invention. Here, the pulverization method of biocellulose is not particularly limited. For example, a method of shearing by rotating at high speed in water with a homogenizer or a method of mechanical shearing after acid hydrolysis treatment is used. be able to.

  In the base material or printing paper provided with the ink receiving layer containing the porous spherical particles according to the present invention, excellent coating strength is obtained, and the ink tends to be well absorbed and fixed. From this, it is presumed that the porous spherical particles according to the present invention are formed by dispersing aluminum hydroxide particles on the surface and inside of a network structure in which biocellulose is intertwined.

When the average particle diameter of the porous spherical particles of the present invention is less than 1 μm, the average pore diameter of the particles is small and the ink absorbability is lowered. On the other hand, when the average particle size of the porous spherical particles exceeds 100 μm, the transparency is lowered and the coating strength is lowered, which is not desirable. In addition, the preferable range of a porous spherical particle is the range of 2-15 micrometers.
When the pore volume of the porous spherical particles is less than 0.5 ml / g, the ink absorbability is low when applied to the ink receiving layer, which causes a practical problem. On the other hand, when the pore volume exceeds 3.0 ml / g, the structure of the porous spherical particles becomes brittle, so that the strength of the coating film composed of the ink receiving layer is lowered. The pore volume of the porous spherical particles is more preferably in the range of 0.7 to 2.0 ml / g.

2. Method for Producing Porous Spherical Particles The method for producing porous spherical particles according to the present invention comprises 100 parts by mass (in terms of solid content) of a dispersion of aluminum hydroxide particles having an average particle size in the range of 10 to 300 nm, and biocellulose. A mixed liquid is prepared by mixing 0.1 to 20 parts by mass (in terms of solid content) of the dispersion, and the mixed liquid is spray-dried.

A mixture of an aluminum hydroxide dispersion and a biocellulose dispersion is sprayed into an air stream to prepare porous spherical particles. As the solvent of the mixed solution, water or an organic solvent is used. As the organic solvent, monohydric alcohols such as ethanol, propanol and butanol, polyhydric alcohols such as ethylene glycol, and the like can be used.
About the density | concentration of the said spraying liquid, it is preferable to exist in the range of 5-60 weight% in conversion of solid content, especially 10-50 weight%. When the solid content concentration of the spray liquid is less than 5% by weight, it is difficult to obtain an aggregate of aluminum hydroxide particles and biocellulose. When the concentration of the spray solution exceeds 60% by weight, the spray solution becomes unstable and it becomes difficult to obtain a spherical aggregate. Moreover, the spray-drying mentioned later cannot be performed continuously, and the yield of an assembly falls.

  The spray drying method of the spray liquid is not particularly limited as long as the above-described aggregate can be obtained, and conventionally known methods such as a rotating disk method, a pressure nozzle method, and a two-fluid nozzle method can be employed. In particular, the two-fluid nozzle method disclosed in Japanese Examined Patent Publication No. 2-61406 is preferable because it can obtain spherical fine particle aggregates having a uniform particle size distribution and can easily control the average particle size. .

The drying temperature at this time varies depending on the concentration of the spray liquid, the processing speed, etc., but when using a spray dryer, for example, the inlet temperature of the spray dryer is 100 to 400 ° C., and the spray speed is 0.5 to 3 L / min. The conditions such as the outlet temperature of 40 to 200 ° C. are preferable.
When the inlet temperature is less than 100 ° C., the drying is insufficient and the spherical shape is not obtained, the irregular shaped particles increase, and the problem of dispersibility tends to occur. When the temperature exceeds 400 ° C., the network structure is decomposed due to the oxidation of biocellulose, so that the ink absorption function including the porous spherical particles obtained may not reach a practical level. . On the other hand, when the outlet temperature is less than 40 ° C., the drying is insufficient and the spherical shape is not obtained, and irregular shaped particles are increased, which tends to cause a problem of dispersibility. When the temperature exceeds 200 ° C., acetic acid that may be blended as a stabilizer of the aluminum hydroxide dispersion volatilizes, so that the dispersibility of the aluminum hydroxide dispersion may deteriorate.

  When the amount of biocellulose (based on solid content) used relative to 100 parts by mass of aluminum hydroxide particles is less than 0.1 parts by mass, the shrinkage after spray drying is large, and the pore volume of the resulting porous spherical particles decreases. When applied to the ink receiving layer, the ink absorbability is unlikely to reach a practical level. Similarly, when the amount of biocellulose (in terms of solid content) exceeds 20 parts by mass, the shape retention of the particles decreases, although the shrinkage after spray drying is small. The range of 1-10 mass parts can be mentioned as a more suitable usage-amount range of the biocellulose (solid content conversion) with respect to 100 mass parts of aluminum hydroxide particles.

3. Ink-receiving layer-forming coating solution containing porous spherical particles The ink-receiving layer-forming coating solution of the present invention comprises 100 parts by mass of the porous spherical particles of the present invention (in terms of solid content) and 5 to 60 parts by mass of a binder (solid). And the solvent is 150 to 1500 parts by mass.

As the binder used here, hydrophilic polymers such as polyvinyl alcohol, modified polyvinyl alcohol, and polyvinylpyrrolidone can be used. Further, they can be used after being modified.
Although the usage-amount of a binder changes also with the kind of binder, it is 5-60 mass parts with respect to 100 mass parts of porous spherical particles, Preferably it is 10-40 mass parts. When the amount of the binder is less than 5 parts by mass, the adhesive force between the ink receiving layer and the base sheet is insufficient, the ink receiving layer is easily peeled off, and the strength of the ink receiving layer may be insufficient. In the case of exceeding the range, the amount of ink received may be lowered, and the water resistance may be lowered.
Although the density | concentration of the porous spherical particle in a coating liquid is suitably selected by the coating method, Preferably it is 2-40 mass%, Especially preferably, it is desirable to exist in the range of 5-30 mass%.

  As the solvent, water and / or an organic solvent can be used. Examples of the organic solvent include isopropyl alcohol, ethanol, butanol and the like.

  The ink receiving layer forming coating solution can be prepared by mixing the above-mentioned components. Further, in the coating liquid for forming an ink receiving layer according to the present invention, the adhesion between the ink receiving layer and the substrate sheet is improved, the strength and weather resistance of the ink receiving layer are improved, and the ink receiving layer For the purpose of adjusting the pore structure, an antioxidant, organic polymers such as celluloses, biofibers, inorganic polymers, inorganic fine particles and the like may be contained.

4). Recording sheet with ink-receiving layer The recording sheet with an ink-receiving layer of the invention has an ink-receiving layer formed on a base material using the ink-receiving layer-forming coating solution.
In the present invention, the substrate sheet is not particularly limited, and a resin film sheet such as PET and PVC, various papers, steel plates, cloths, and the like are used.
As a method for forming the ink receiving layer on the substrate sheet, a known method can be adopted, and a preferred method may be adopted depending on the type of the substrate. Specifically, the coating liquid is sprayed, roll coater method, or the like. It can be formed by coating the substrate sheet by a blade coater method, a bar coater method, a curtain coater method or the like and then drying.

  The film thickness of the ink receiving layer can be arbitrarily selected depending on the thickness of the substrate, the use of the printed material, the type of printing ink, and the like, but it is usually desirably in the range of 5 to 100 μm. If the thickness of the ink receiving layer is less than 5 μm, the ink absorption capacity is insufficient and bleeding occurs, and the color may be lowered when the amount of ink used is reduced. When the thickness of the ink receiving layer is larger than 100 μm, it is difficult to obtain it by a single coating, and it is difficult to obtain a coating multiple times. When cracking, it may crack or peel off.

The ink receiving layer thus formed generally has a pore diameter in the range of 30 to 2000 nm, and the pore volume of the pore diameter in this range is 0.15 to 2.0 ml / g, preferably 0. .2 to 2.0 ml / g, more preferably 0.2 to 1.0 ml / g is recommended.
When the pore volume having a pore diameter of 30 to 2000 nm in the ink receiving layer is less than the lower limit value, the pigment-based ink cannot be sufficiently absorbed, so that the pigment particles remain on the surface of the ink receiving layer and peel off due to abrasion. However, the printed material may lose color. Also, if the pore volume of the ink receiving layer exceeds the above upper limit, the fixability of the pigment particles is reduced, or many of the pigment particles after printing are collected under the ink receiving layer (near the substrate surface). May lack clarity.

In the recording sheet with an ink receiving layer of the present invention, since the ink receiving layer contains the porous spherical particles and a binder (resin), the ink absorbability is improved due to the large pore volume of the porous spherical particles, and bleeding is caused. Is less likely to occur. Moreover, since the biocellulose which has a fine microfibril structure exists in the surface of this porous spherical particle, coating-film intensity | strength improves.
Next, the measurement methods employed in the examples and others of the present invention will be specifically described as follows.

[Measuring method of average particle size by dynamic light scattering method]
Regarding the average particle diameter of the aluminum hydroxide fine particles, the sample aluminum hydroxide dispersion was diluted with 0.58% ammonia water to adjust the solid content concentration to 1% by mass, and a particle size measuring device (manufactured by Otsuka Electronics Co., Ltd., Laser particle size analysis system: LP-510 model PAR-III).
This measuring method was applied to the measurement of the average particle diameter of aluminum hydroxide particles in the aluminum hydroxide dispersions of Examples 1 to 5 and Comparative Example 3.

[Measurement method of average particle size by centrifugal sedimentation]
Regarding the average particle diameter of the porous spherical particles, first, a dispersion of porous spherical particles (water or 40% by mass glycerin solvent, solid content concentration 0.1 to 5% by mass) is obtained from an ultrasonic generator (manufactured by Iuch, Disperse in US-2) for 5 minutes. Further, from a dispersion whose concentration has been adjusted moderately by adding water or glycerin, the dispersion is taken into a glass cell (size of 10 mm in length, 10 mm in width, and 45 cm in height), and a centrifugal sedimentation type particle size distribution analyzer (Horiba) The average particle diameter was measured using a mill manufactured by CAPA-700.
This measuring method was applied to the average particle size measurement of the aluminum hydroxide particles of Comparative Examples 1 and 2 and the porous spherical particles of Comparative Examples 3 and 4 in addition to the porous spherical particles of Examples 1 to 5.

[Measurement method of pore volume]
Regarding the pore volume of the porous oxide particles, first, 10 g of a sample was taken in a crucible, dried at 300 ° C. for 1 hour, then placed in a desiccator and cooled to room temperature. Next, a 1 g sample was taken in a well-washed cell, and nitrogen was adsorbed using a nitrogen adsorption device (manufactured in-house), and the pore volume was calculated from the following equation.
Pore volume (ml / g) = (0.001567 × (V−Vc) / w)
However, 0.001567: Ratio of density of nitrogen gas and liquid nitrogen, V: Adsorption amount in a standard state at a pressure of 735 mmHg (ml), Vc: Cell blank (ml) at a pressure of 735 mmHg, W: Sample weight (g) It is.

The pore volume of the ink receiving layer was measured by a mercury intrusion method. Specifically, about 0.2 to 0.3 g of the prepared recording sheet with an ink receiving layer was inserted into a measurement cell (volume: 0.5 cc), and mercury was measured using AUTOSCAN-60 PORPSIMETER (manufactured by QUANTA CHROME). The contact angle is 130 °, the mercury surface tension is 473 dyn / cm ² , the measurement range is set to “high pressure”, and the pore distribution is measured. Next, the pore volume in the range of 3.4 to 30 nm and 30 to 2000 nm is determined from the measured pore distribution, and the pore volume per 1 g of the receiving layer is determined from the measured weight of the receiving layer in the recording sheet.

[Measurement of film thickness]
The cross section of the recording medium provided with the ink receiving layer was cut accurately in the vertical direction, and then a photograph was taken using a scanning electron microscope and measured.

[Evaluation of printing method and printing results]
On the obtained recording sheet, a 2 cm square solid-coated pattern W was printed with an inkjet printer (manufactured by GRAPHTEC: Masterjet) using genuine pigment ink and dye ink. The colors used were magenta, black, cyan, and yellow, and printing was performed by changing the density by changing the output.

The printing density was measured with a color reflectometer (manufactured by Nippon Denshoku Industries Co., Ltd .: KRD-2200). If the concentration is 0.8 or more, it can be used without any particular problem.

Bleeding was observed the shape of each printed dot in a microscope, and evaluated according to the following criteria.
A: Completely circular with no bleeding B: Circular with slight bleeding Δ: Circular with obvious bleeding

The water-resistant printed piece was immersed in water and the elution of the pigment and the dye was observed and evaluated according to the following criteria.
◎: No bleeding is observed ○: Slight bleeding is observed Δ: Bleeding is clearly recognized ×: Elution of pigment or dye is recognized

Using a coating strength scratch testing machine (Crystal System Co., Ltd., SC-85), a cotton gauze was pushed onto the coated surface of the sheet with a load of 300 g and worn 100 times with a stroke width of 3 cm. Tests were conducted and evaluated according to the following criteria.
○: No flaws occurred Δ: Some flaws occurred in the 100th friction test, but no flaws occurred in the 20th friction test ×: Wounds occurred in the 20th friction test

(Preparation of porous spherical particles)
500 g of an aluminum hydroxide dispersion (average particle size 70 nm, solid content concentration 20% by mass) was added to 100 g of an aqueous dispersion (1% by mass) of biocellulose and mixed with stirring to obtain a spray solution.
This biocellulose has a microfibril structure having a thickness of 5 nm and a width of 130 nm (average value) produced by stationary culture. Also in the following examples and comparative examples, aqueous dispersions having different concentrations with the same biocellulose were used.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray-dried under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, an average particle diameter of 5 μm, and a pore volume. A porous spherical particle of 0.76 ml / g was obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.60 ml / g.
About the obtained recording sheet, it printed on the said conditions and measured printing density, bleeding, water resistance, and color fading (coating film strength). The measurement results are shown in Table 1 together with the measurement results of the following examples and comparative examples.

(Preparation of porous spherical particles)
500 g of an aluminum hydroxide dispersion (average particle size 80 nm, solid content concentration 20% by mass) was added to 100 g of the biocellulose dispersion (5% by mass), and stirred to obtain a spray solution.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray-dried under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, and an average particle size of 10 μm and a pore volume. 0.90 ml / g of porous spherical particles were obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.75 ml / g.

(Preparation of porous spherical particles)
500 g of an aluminum hydroxide dispersion (average particle size 80 nm, solid content concentration 20% by mass) was added to 100 g of the biocellulose dispersion (10% by mass) and mixed by stirring to obtain a spray solution.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray drying is performed under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, an average particle diameter of 7 μm, and a pore volume. 1.10 ml / g of porous spherical particles were obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.80 ml / g.

(Preparation of porous spherical particles)
500 g of an aluminum hydroxide dispersion (average particle size 150 nm, solid content concentration 20% by mass) was added to 100 g of the biocellulose dispersion (1% by mass) and mixed by stirring to obtain a spray solution.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray-dried under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, an average particle diameter of 40 μm, and a pore volume. 1.20 ml / g of porous spherical particles were obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.90 ml / g.

(Preparation of porous spherical particles)
500 g of aluminum hydroxide dispersion (average particle size 70 nm, solid content concentration 20% by mass) was added to 100 g of biocellulose dispersion (15% by mass), and stirred and mixed to obtain a spray solution.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray drying is performed under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, an average particle diameter of 5 μm, and a pore volume. 1.20 ml / g of porous spherical particles were obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 1.00 ml / g.

Comparative Example 1

[Preparation of coating solution for forming ink receiving layer]
90 g of aluminum hydroxide particles (average particle size: 50 μm) and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed, and further diluted by adding 200 g of pure water to prepare an ink receiving layer forming coating solution.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.20 ml / g.

Comparative Example 2

[Preparation of coating solution for forming ink receiving layer]
90 g of aluminum hydroxide particles (average particle size 50 μm) and 100 g of an aqueous biocellulose solution (concentration 10% by mass) were mixed, and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.30 ml / g.

Comparative Example 3

(Preparation of porous spherical particles)
500 g of the aluminum hydroxide dispersion (average particle size 70 nm, solid content concentration 20% by mass) was added to 100 g of the biocellulose dispersion (30% by mass), and stirred and mixed to obtain a spray solution.
This spray solution is applied to a spray dryer (NIRO ATMIZER, manufactured by NIRO), spray-dried under the conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute, an average particle diameter of 5 μm, and a pore volume. 2.5 ml / g of porous spherical particles were obtained.

[Preparation of coating solution for forming ink receiving layer]
90 g of porous spherical particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink receiving layer.

[Preparation of recording sheet]
This coating solution was applied onto a PET film using a bar coater, dried, and then heat-treated at 140 ° C. to obtain a recording sheet. The ink receiving layer had a thickness of 50 μm and a pore volume of 0.10 ml / g.

Comparative Example 4

(Preparation of porous particles)
A spray liquid consisting of 100 g of biocellulose dispersion (1% by mass) is applied to a spray dryer (NIRO, manufactured by NIRO ATMIZER) and spray-dried under conditions of an inlet temperature of 280 ° C., an outlet temperature of 110 ° C., and a spray rate of 2 liters / minute. As a result, irregular shaped particles with irregular particles were produced.

[Preparation of coating solution for forming ink receiving layer]
90 g of the irregular shaped particles and 100 g of an aqueous polyvinyl alcohol solution (concentration: 10% by mass) were mixed, and further diluted by adding 200 g of pure water to prepare a coating solution for forming an ink-receiving layer. Could not be used as.

2 is a transmission electron micrograph (magnification 20000 times) of the porous spherical particles obtained in Example 1. FIG.

Claims (4)

Including 100 parts by weight of aluminum hydroxide particles having an average particle diameter in the range of 10 to 300 nm and 0.1 to 20 parts by weight of biocellulose, the average particle diameter is in the range of 1 to 100 μm, and the pore volume is 0.5 to 3 Porous spherical particles characterized by being in the range of 0.0 ml / g.
Mix and mix 100 parts by mass (solid content conversion) of dispersion of aluminum hydroxide particles having an average particle diameter of 10 to 300 nm and 0.1 to 20 parts by mass (solid content conversion) of biocellulose dispersion. A method for producing porous spherical particles, comprising preparing a liquid and spray-drying the liquid mixture.
A coating liquid for forming an ink-receiving layer, comprising 100 parts by weight (in terms of solid content) of porous spherical particles according to claim 1, 5 to 60 parts by weight (in terms of solid content) of a binder, and 150 to 1500 parts by weight of a solvent. .
  A recording sheet with an ink-receiving layer, comprising an ink-receiving layer formed on the substrate using the coating liquid for forming an ink-receiving layer according to claim 3.