JP2003191617A - Inkjet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet having high print density and gloss and suitable for photographic printing. SOLUTION: In an ink jet recording sheet provided with at least two coating layers on a support, at least one of the coating layers has a silica aggregate particle diameter of 1 μm or less produced by condensing active silicic acid. An ink jet recording sheet characterized in that it contains cation-modified fine particles of silica aggregate particles having a pore volume of 0.4 to 2.0 ml / g having a pore diameter of 100 nm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet which is suitable for photographic printing because it provides high print density and gloss.

[0002]

2. Description of the Related Art In recent years, the performance and cost of personal computers have rapidly increased, and an environment has been established in which individuals can easily handle full-color images. In addition, the high performance of digital cameras and the increase in the number of shipments are remarkable, and it has become possible to easily capture high-definition images equivalent to silver halide photography. Images taken with a digital camera can be used with various printers from personal computers.
For example, it is possible to output and record to a printer such as a heat sensitive color recording system, a fusion thermal transfer recording system, a sublimation recording system, an electrophotographic system, an inkjet recording system. Among these recording methods, the inkjet recording method is a recording method suitable for personal use because plain paper can be used as a recording sheet, running cost is low, and hardware is compact and inexpensive. Further, due to the achievement of full color and high resolution, it has attracted attention as an easy output means of color images, and is considered to be one of the most effective methods as a substitute for silver halide photography.

Although plain paper can be used for the ink jet printer, it is necessary to use a special ink jet recording sheet for high quality recording of photographs. The quality required for this ink jet recording sheet includes quick absorption of ink containing water, dyes, organic solvents, additives, etc., drying in a short time, reproduction of fine images or characters, and color density of images. It is required as a basic performance that the color tone is high and there is no bias in color tone. Further, water resistance is also important so that water will not adhere and images or characters printed in a high humidity environment will not be blurred. In addition, high gloss equivalent to that of silver salt photographic paper is also necessary to improve the quality of recorded matter. In order to meet these requirements, a high performance inkjet recording sheet is provided with a dedicated ink receiving layer on a substrate.

Previously, a large number of products were manufactured by coating a base sheet with an aqueous solution of a water-soluble resin such as polyvinyl alcohol, polyvinylpyrrolidone, a water-soluble cellulose derivative and gelatin, and drying the base sheet. With these recording sheets, a high-gloss inkjet recording sheet can be easily manufactured at low cost. However, a recording sheet provided with an ink-receiving layer containing a water-soluble resin as a main component on a support has a low ink drying speed, cannot support high-speed printers, and has poor water resistance. Inkjet recording sheets having a porous ink-receiving layer obtained by hardening a resin with a small amount of a binder resin have become mainstream. In order to have high gloss equivalent to that of silver salt printing paper using a pigment, it is necessary to make the particle size of the pigment less than or equal to the wavelength of light, that is, on the order of submicrons, and the choice of pigment is extremely high. is important.

As a pigment having a particle size of submicron, silica called colloidal silica is commercially available. A typical colloidal silica is one in which spherical silica particles having a particle size of 5 to 50 nm are dispersed in water in a stable colloidal state without secondary aggregation, and many manufacturing methods are known. As a typical production method, for example, in US Pat. No. 2,577,484, a dilute aqueous solution of sodium silicate is treated with a cation exchange resin to prepare an acidic active silicic acid aqueous solution. By adding an alkali to the polymer to stabilize and polymerize it, a liquid in which silica fine particles called seed particles are monodispersed (seed liquid) is made, and the rest of the active silicic acid aqueous solution (feed liquid) is maintained while keeping the system alkaline. Is gradually added thereto to polymerize silicic acid, and seed particles are grown to produce colloidal silica.

When producing monodisperse colloidal silica,
The most industrially used manufacturing method is the above-mentioned ion exchange resin method. By this method, it is possible to produce colloidal silica having a sharp particle size distribution while freely controlling the particle size using an alkali metal silicate, such as water glass, which is an inexpensive industrial product, as a raw material. Has become. The colloidal silica obtained by these methods is generally sold as a product having a particle size of 7 to 20 nm and is a very fine particle. Therefore, a very transparent and highly glossy coating film can be obtained by drying. Paying attention to this point,
A number of patents using colloidal silica for the ink receiving layer have been filed. For example, JP-A-5-338348, JP-A-6-183131, and JP-A-6-183.
No. 134, No. 6-297830, No. 7-81213, No. 7-117335, No. 9-86033, No. 9-1235.
88, JP-A-9-150571, JP-A-9-157571.
No. 183267, Japanese Unexamined Patent Publication No. 9-263040, Japanese Unexamined Patent Publication No. 10-217599. However, most of the colloidal silica are spherical particles, and each primary particle is monodispersed without agglomeration, so that the particles are densely packed in the dry state of the coating layer, and there are very few voids between particles. Take structure. Therefore, the pore volume of colloidal silica is generally less than 0.4 ml / g, the ink absorption amount is very small when used in the ink absorption layer, and the ink absorption rate is small because the pore size is small. It was slow and had the drawback of causing ink overflow and uneven density.

In order to avoid such drawbacks of colloidal silica, recently, amorphous synthetic silica produced by a wet method or a dry method has been finely pulverized by a wet method and used for an ink jet recording sheet. . Amorphous synthetic silica by the wet method is classified into silica by the precipitation method and silica by the gel method. In the precipitation method, mineral acid is added stepwise to an alkali silicate aqueous solution, and the precipitated silica is manufactured by filtration. The gel method is obtained by mixing an alkaline silicate solution with a mineral acid to cause gelation, followed by washing and crushing. For example, in JP-A-55-116613, an acid is added to an alkali silicate aqueous solution in two stages, and the solution after the reaction is filtered to obtain a wet cake of hydrated silicic acid. A method of obtaining amorphous synthetic silica having a relatively large pore volume by applying shearing force or vibration to a cake to form a slurry and then spray-drying is disclosed. In the silica obtained by such a wet method, primary particles aggregate to form secondary particles, and generally have a large pore volume due to voids between primary particles or between secondary particles. However, it is only used for agricultural chemical carriers and rubber fillers. Moreover, the particle diameter is 1 to 20 μm.
Since it is m, the degree of light scattering is high, and even when it is used in the ink receiving layer, it has no gloss and the printing density is not satisfactory.

A method of subjecting the above-mentioned amorphous synthetic silica to wet pulverization by a mechanical means is known as a method of obtaining a dispersion liquid of silica aggregate particles. For example, Japanese Patent Laid-Open No. 9-28616
Japanese Patent Publication No. 5 discloses a method of producing colloidal silica aggregate particles having a submicron particle size by applying a strong force to amorphous synthetic silica by mechanical means.
The silica aggregate particles produced by this method have a large pore volume and a high ink absorption amount. However, even if the average particle size is in the submicron range, it has a wide particle size distribution because it is pulverized by pulverization, and since it contains coarse particles of the micron unit, it has a drawback that the gloss is inferior to that of colloidal silica.

Further, it was examined that the synthetic silica produced by the dry method is mechanically dispersed in water and used for the ink jet receiving layer. The synthetic silica produced by the dry method is produced by a method of decomposing a volatile silicon compound at a high temperature in a flame as disclosed in, for example, Japanese Patent Publication No. 59-169922, and has a dispersibility and transparency. Excellent silica. The dry method synthetic silica is a bulky powder, and is easier to mechanically form an aqueous dispersion than the wet method silica. When this aqueous dispersion is applied, a coating film having high gloss and good ink absorbency can be formed. For this reason, many examples have been filed in which dry method synthetic silica is used for an ink jet recording sheet. For example, JP-A-7-27678
7, JP-A-11-20306, JP-A-11-20306
No. 48602, Japanese Patent Laid-Open No. 11-321079, and Japanese Patent Laid-Open No. 2000-43401 are disclosed. However, because the bond between the agglomerated primary particles is relatively weak, the strong capillary force acting between the voids, which is brought about by the drying of water when creating the coating film, tends to cause the destruction of the agglomerated state, and the coating film However, there is a big defect that cracks of several mm which are visible to the naked eye are easily formed.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording sheet which has higher print density and gloss than the ink jet recording sheet according to the prior art and is suitable for photographic printing.

[0011]

The present invention includes the following aspects. (1) In an inkjet recording sheet in which at least two coating layers are provided on a support, at least one of the coating layers has a silica aggregate particle size of 1 μm or less produced by condensing activated silicic acid, An inkjet recording sheet comprising cation-modified fine particles of silica aggregate particles having a pore size of 100 nm or less and a pore volume of 0.4 to 2.0 ml / g.

(2) In an ink jet recording sheet in which at least two coating layers are provided on a support, at least one of the coating layers has an active silicic acid aqueous solution added dropwise to hot water or activated silicic acid. The aqueous solution is heated to generate silica seed aggregate particles, and an alkali is added to stabilize the silica seed aggregate particles before the dispersion liquid precipitates or gels, and then the silica seed aggregate particles are activated while maintaining the stable state. Silica acid aqueous solution was added little by little to grow silica seed aggregate particles, and the aggregate particle size was 1 μm or less, and the pore size was 1
An ink jet recording sheet comprising cation-modified fine particles of silica aggregate particles having a pore volume of 00 nm or less of 0.4 to 2.0 ml / g.

[0013] (3) in terms of SiO ₂ with respect to SiO ₂ 1 mole of the rate of addition of active silicic acid solution while maintaining the stable state is included in the silica seed aggregate particles 0.00
The inkjet recording sheet according to (2), which is added at a rate of 1 to 0.2 mol / min.

(4) The specific surface area by nitrogen adsorption method is 300
In m ² / g~1000m ² / g, volume of pores pore diameter 100nm is 0.4ml / g~2.0ml / g, silica aggregates preferably 0.5ml / g~2.0ml / g A liquid in which particles were dispersed in a colloidal form was used as a seed liquid, an alkali was added to the seed liquid, and then a feed liquid containing an active silicic acid aqueous solution was added little by little to the seed liquid to grow silica aggregate particles. The specific surface area according to the nitrogen adsorption method is preferably 50 to 500 m ² / g, more preferably 1
00m ² / g~400m ² / g, more preferably 150m
² / g to 350 m ² / g, average secondary particle diameter of 20 nm to 1
A coating solution containing cation-modified fine particles of silica aggregate particles having a pore volume of 000 nm and a pore diameter of 100 nm or less of 0.4 ml / g to 2.0 ml / g was applied (1) to (3).
The inkjet recording sheet according to any one of 1.

(5) The specific surface area by the nitrogen adsorption method is 300.
In m ² / g~1000m ² / g, volume of pores pore diameter 100nm is 0.4ml / g~2.0ml / g, silica aggregates preferably 0.5ml / g~2.0ml / g A liquid in which particles are colloidally dispersed is used as a seed liquid, and a mixture of an active silicic acid aqueous solution and an alkali is added little by little to the seed liquid, or the feed liquid and the alkali are simultaneously added little by little. It was grown silica aggregate particles, specific surface area measured by the nitrogen adsorption method of preferably 50m ² / g~500m ² / g, more preferably 10
0m ² / g~400m ² / g, more preferably 150 meters ²
/ G to 350 m ² / g, average secondary particle diameter of 20 nm to 1
A coating liquid containing cation-modified fine particles of silica aggregate particles having a pore volume of 000 nm and a pore diameter of 100 nm or less and 0.4 ml / g to 2.0 ml / g was applied (1) to (4).
The inkjet recording sheet according to any one of 1.

(6) The ink jet recording sheet according to any one of (2) to (5), wherein the seed liquid is produced by adding an active silicic acid aqueous solution little by little to hot water.

(7) The ink jet recording sheet according to any one of (2) to (5), wherein the seed liquid is produced by heating an active silicic acid aqueous solution.

[0018] (8) The specific surface area by preferably nitrogen adsorption method 50m ² / g~500m ² / g, more preferably 100
m ² / g~400m ² / g, more preferably 150 meters ² /
g-350 m ² / g, pore volume 0.4 ml / g- ² .
0 ml / g of silica aggregate particles, the main peak of the weight-converted particle size distribution of the dispersion liquid measured by a laser particle size meter by the dynamic light scattering method is in the range of 10 nm to 70 nm, and its standard A coating liquid containing fine particles obtained by cationically modifying silica aggregate particles having a deviation of 10 nm or less and a cumulative weight of main peaks of 80% or more of the cumulative total weight including peaks other than the main peaks was applied to a support. (1)
The inkjet recording sheet according to any one of to (7).

(9) The specific surface area by the nitrogen adsorption method is 100 m ²
/ G~400m ² / g, preferably 150m ² / g~40
0 m ² / g, pore volume of 100 nm or less is 0.4
ml / g to 2.0 ml / g of silica aggregate particles, the dispersion has an absorbance at a wavelength of 560 nm of 0.3 or less at a solid content concentration of 1.0% by mass, and a solid content concentration of 10. The ink jet recording according to any one of (1) to (8), which comprises coating a support with a coating liquid containing fine particles obtained by cationically modifying silica aggregate particles having an absorbance at 0 mass% of 0.3 or less. Sheet.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized by using cation-modified fine particles of silica aggregate particles produced by a specific method. First, the silica aggregate particles before cation modification will be described below. The silica aggregate particles are produced by condensing activated silicic acid, and have an aggregate particle diameter (average secondary particle diameter) of 1 μm or less and a pore volume of 100 nm or less and a pore volume of 0.4 to 2.0 ml / g. Is. The aggregate particle size is 1 μm or less, preferably 20 nm to 800 nm,
More preferably, it is 30 nm to 500 nm. Particle size is 1
When it is more than μm, light scattering increases, and when it is used for the ink receiving layer, high printing density may not be obtained. The silica aggregate particles have a secondary particle structure in which primary silica particles are irregularly bonded, and have a different form from silica having a chain shape, an elongated shape, or a necklace shape. A laser granulometer utilizing the principle of the dynamic light scattering method was used to measure the aggregate particle size. The suspension solution and the fine particles dispersed in the solution perform Brownian motion. The movement is slow for large particles and fast for small particles. When this solution is irradiated with laser light (He-Ne laser), the light is scattered by Rayleigh scattering and a Doppler shift occurs. The particle size and particle size distribution can be obtained by observing and analyzing this frequency shift using a photon detection method. In the present invention, the particle size was measured while the sample was sufficiently diluted in water.

The pore volume of the silica aggregate particles is 1
The pore volume of 00 nm or less is 0.4 to 2.0 ml / g, preferably 0.6 to 1.5 ml / g, and most preferably 0.7 to 1.3 ml / g. When the pore volume is less than 0.4 ml / g, the amount of ink absorbed is small, and therefore it is necessary to increase the coating amount when manufacturing an inkjet recording sheet, which is disadvantageous in terms of cost. On the other hand, when the pore volume exceeds 2.0 ml / g, the density of the coating film is too small and the mechanical strength is poor, and there are problems such as large cracks during coating and scratches on the coating film. There is a fear. A nitrogen adsorption method was used to measure the pore volume and the pore diameter.

The primary particle diameter is not particularly limited, but the diameter is preferably 5 nm to 60 nm. However,
Since primary particles of the silica aggregate particles are chemically bonded to form secondary particles, it is difficult to accurately determine the diameter of the primary particles. Therefore, in the present invention, the specific surface area by the nitrogen adsorption method is adopted as a measure of the average particle diameter of the primary particles. Preferred specific surface area of 50m ² / g~500m ² / g. When the specific surface area is smaller than this range, the light scattering becomes strong and the transparency of the dry coating film decreases. As a result, the print density decreases. On the other hand, when the specific surface area is larger than the above range, the coating liquid easily gels,
Workability may be impaired. Further, when mixed with a binder to form a dry coating film, cracking is likely to occur, and it may be difficult to obtain a good coating film. More preferably 100m ² / g~400m ² / g, more preferably from 150m ² / g~350m ² / g.

The inventors of the present invention have filed Japanese Patent Application Nos. 2000-336356 and 2000-336357 as a method for producing a dispersion liquid containing the silica aggregate particles, which will be described below. The activated silicic acid aqueous solution refers to, for example, a silicic acid aqueous solution having a pH of 4 or less obtained by subjecting an alkali metal silicate aqueous solution to an ion exchange treatment with a hydrogen type cation exchange resin. The active silicic acid aqueous solution preferably has a SiO ₂ concentration of 1 to 6 mass%, more preferably 2 to 5 mass%, and a pH of 2 to 4.
An activated aqueous solution of silicic acid is desirable. The alkali metal silicate may be one that can be obtained as a commercially available industrial product, and more preferably a sodium water glass having a SiO ₂ / M ₂ O (where M represents an alkali metal atom) molar ratio of about 2 to 4. Is preferably used.

Alkali metal case at the time of ion exchange treatment
SiO in aqueous citrate solution₂A concentration of 1-6% by mass is desired
Good SiO₂If the concentration exceeds 6% by mass, ions
The solution becomes thicker in the exchange resin column tower, making it difficult to process.
There is a risk of becoming. On the other hand, SiO ₂When the concentration is less than 1% by mass
In this case, the amount of water in the reaction solution will increase and production efficiency will decrease.
There is

The silica aggregate particles are prepared by preparing a seed solution as a precursor, stabilizing the silica aggregate particles in the seed solution with an alkali, and then adding an active silicic acid aqueous solution little by little while maintaining the stable state. It can be produced by condensing activated silicic acid on the surface of silica aggregate particles to grow primary particles. Seed solution, the specific surface area by a nitrogen adsorption method at 300m ² / g~1000m ² / g, pore size 1
Pore volume of 00 nm or less is 0.4 ml / g to 2.0 ml
/ G, preferably 0.5 ml / g to 2.0 ml / g, is a liquid in which porous silica aggregate particles (referred to as seed aggregate particles) are colloidally dispersed. The average secondary particle diameter of the seed aggregate particles is not particularly limited, but is preferably 5 nm to 2000 nm, more preferably 1
It is 0 nm to 600 nm. Even if the average secondary particle diameter of the seed aggregate particles is 1000 nm or more, the secondary particle diameter may be reduced due to the mechanical force of the alkali added in the growth step or stirring, and the average of the seed aggregate particles is not necessarily the same. It is not necessary to make the secondary particle diameter 1000 nm or less.

The concentration of seed aggregate particles is preferably 0.05 to 10.0 mass% in terms of silica.
When the silica-equivalent concentration of the seed agglomerate particles is less than 0.05% by mass, new seed agglomerate particles may be generated in the subsequent process of growing the seed agglomerate particles, and the particle size distribution of the obtained particles May become broad. on the other hand,
If the silica-equivalent concentration of the seed agglomerate particles exceeds 10% by mass, excessive agglomeration of the particles may proceed, possibly resulting in gelation.

In order to prevent the aggregation of the seed aggregate particles in the seed solution, a necessary amount of alkali is added. This alkali also acts as a condensation catalyst for the active silicic acid added to the seed solution. The alkali to be used is not particularly limited, but hydroxides of alkali metal elements such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides, alkali metal silicates, ammonia, quaternary Examples thereof include nitrogen compounds such as ammonium hydroxide and amines, and these alkalis are used alone or in a mixture. Among these, ammonia is more preferable because it is easy to control the pH of the solution and can be easily volatilized when forming a dry coating film. In addition, with ammonia,
When a dry coating film of silica and a binder is prepared, the transparency of the coating film is good.

The amount of alkali added is not particularly limited, but the pH of the solution is 6.5 or more, more preferably pH.
The amount of alkali necessary to achieve 8 or more, more specifically 1 × 10 ^{−3 to} 1.0 mol, and more preferably 1 mol of silica component (SiO ₂ ) in the seed aggregate particles.
It is desirable that the amount of alkali is 0.01 to 0.1 mol. Also, as the alkali amount is increased, that is, as the pH of the solution is increased, the surface charge amount of the silica seed agglomerate particles is increased and the repulsive force between the particles is increased. And the average secondary particle diameter tends to decrease when grown under the same conditions.

The alkali is added to the seed solution before the growth step at a time, or it is added little by little with the active silicic acid aqueous solution that is added to the seed solution during the growth step, or It is possible to employ a method in which it is mixed with an active silicic acid aqueous solution and added little by little.
When an active silicic acid aqueous solution is mixed with an alkali and added to the seed solution, it is desirable to mix an alkali amount such that the pH of the active silicic acid aqueous solution is 7 or more. When the pH of the active silicic acid aqueous solution is 7 or more, the active silicic acid aqueous solution does not gel within a short time.

In the step of growing the seed solution, the seed solution was added to 60
It is desirable to heat the solution to a temperature of not less than 0 ° C, more preferably 80 to 100 ° C. To the heated seed solution, an active silicic acid aqueous solution is added little by little in order to grow particles. In this growth step, activated silicic acid condenses on the surface of the seed agglomerated particles and the primary particle diameter increases, that is, growth occurs. As a result of the seed particles growing in an aggregated state with each other, the primary particles are chemically bound to each other, and a very strong aggregated state of the primary particles, which cannot be obtained by the dry method, can be formed.

The method of adding the active silicic acid aqueous solution is not particularly limited, but it is preferable to continuously add it at a constant rate. The rate of addition of the seed solution of active silicic acid aqueous solution, as active silicic acid excess to produce a new seed aggregate particles are not present in the seed solution, SiO ₂ contained in the seed aggregate particles in the seed solution It is added dropwise at a rate of preferably 0.001 to 0.2 mol / min, more preferably 0.001 to 0.05 mol / min in terms of SiO ₂ per mol. During the addition of the active silicic acid aqueous solution, a necessary amount of alkali may be added at any time in order to prevent excessive aggregation / precipitation of silica aggregate particles due to a decrease in the pH of the solution.

The amount of the active silicic acid aqueous solution added is determined by the specific surface area (primary particle diameter) of the seed aggregate particles in the seed solution used.
The amount of SiO ₂ required to grow the primary particle size to a desired specific surface area is added using an activated silicic acid aqueous solution. The active silicic acid aqueous solution to be added is preferably added at a temperature of 60 ° C. or lower, preferably 40 ° C. or lower so that condensation does not proceed before addition to the seed liquid.

After the addition of the active silicic acid aqueous solution, it is sufficiently stable even if it is cooled as it is, but in order to complete the condensation of the silicic acid, it is preferably further heated for 1 to 24 hours at a temperature of 70 ° C. or higher. This is preferable because the particle size distribution of the silica aggregate particles becomes narrower. The silica aggregate particle dispersion liquid thus obtained preferably removes excess water to concentrate the silica aggregate, and an evaporator, an ultrafiltration membrane or the like can be used.

On the other hand, the seed liquid used in the above method, that is, the dispersion liquid of the seed aggregate particles can be produced by the following method. The first method of producing the seed solution is a method of dropping the above active silicic acid aqueous solution little by little into heated water. This method is most preferable because it has a larger pore volume than the second and third methods to be described later, seed aggregate particles having a small secondary particle diameter can be obtained, and the particle diameter of the silica aggregate particles after growth is also small. The heating temperature of the water to which the activated silicic acid is added is preferably 50 ° C or higher, more preferably 70 ° C or higher. There is no particular upper limit, but it may be 100 ° C. When the temperature is low, the condensation rate of silicic acid is low, which lowers the production efficiency of the seed solution. The pH of water is preferably 8 or less, more preferably 7 or less. If the pH exceeds 8, the aggregation of seed particles caused by the condensation of silicic acid does not proceed sufficiently, and when used as a seed solution, silica aggregate particles having a sufficient pore volume may not be obtained. is there. Further, the activated silicic acid added may be used more frequently for growth of existing seed agglomerate particles without generating new seed agglomerate particles, which may reduce the efficiency of producing the seed solution.

Further, the progress of aggregation of the seed aggregate particles largely depends on the concentration of SiO ₂ solid content in the solution and the heating time. That is, as the amount of active silicic acid added to the hot water increases and the pH of the solution decreases toward the isoelectric point of silica (about pH 2.2), the addition start time of the active silicic acid aqueous solution also increases. Aggregation of the seed particles progresses as the heating time from 1) increases. Therefore, the charging ratio of the aqueous solution of active silicic acid and water and the rate of addition of the aqueous solution of active silicic acid to hot water are set to optimum values in consideration of these tendencies. Also,
When the seed particles are grown under the same conditions as they are used as the seed solution, the average secondary particle diameter becomes large and the pore volume tends to increase. However, if the coagulation of the seed particles progresses excessively, it causes gelation of the solution and precipitation of the coagulated seed particles, which may make it difficult to stabilize the colloid as a colloid even if an alkali is added.

The second method of producing the seed solution is a method of heating the above active silicic acid aqueous solution. The active silicic acid aqueous solution preferably has a SiO ₂ concentration of 1 to 6 mass%, more preferably 2 to 5 mass% and a pH of 2 to 4. The heating temperature of the active silicic acid aqueous solution is preferably 40 ° C. or higher. If the temperature is lower than 40 ° C, the condensation rate of silicic acid is low, and the production efficiency of the seed solution is reduced.

The progress of aggregation of seed particles largely depends on the concentration of SiO ₂ in the active silicic acid aqueous solution and the heating time. That is, the higher the concentration of the active silicic acid aqueous solution and the longer the heating time, the faster the aggregation of seed particles proceeds. When the seed liquid is used as a seed solution so that the aggregation of the seed particles progresses, when grown under the same conditions, the average secondary particle diameter becomes large and the pore volume tends to increase.
However, if the coagulation of the seed particles progresses excessively, it causes gelation of the solution, and it may be difficult to stabilize it as a colloid even if an alkali is added.

In the first method or the second method for producing the above-mentioned seed solution, the progress of the agglomeration of the seed particles is not linear with respect to the reaction time but tends to proceed exponentially, and the progress of the short time is short. Aggregation of seed particles progressed excessively,
This may cause gelation or precipitation of the solution. This phenomenon can be mitigated by adding an anti-gelling agent during the production of the seed solution. Although a water-soluble organic solvent can be used as an anti-gelling agent, alcohol is the most convenient and preferred. As the type of alcohol, it can be used if it is highly water-soluble, such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, n-butanol, isobutanol,
Tert-butanol, ethylene glycol, propylene glycol, glycerin and the like can be exemplified, but methanol, ethanol, isopropyl alcohol, n-, which has a low boiling point, is easily removed from the silica aggregate particle dispersion liquid, and is low in cost. Propyl alcohol is preferred.

As the method for adding alcohol, in the first method for producing the seed solution, it may be added in hot water in advance, or may be added before the step of growing the seed solution. However, in order to produce a silica aggregate particle dispersion liquid having a large pore volume, it is necessary to promote the aggregation of seed particles, and therefore it is preferable to add the seed particles immediately before shifting to the growth step. The same applies to the second method for producing a seed solution, which may be added in advance to activated silicic acid, or may be added before shifting to the growth step, but a silica aggregate having a large pore volume is used. In order to produce a particle dispersion, it is preferable to add it just before shifting to the growth step. The addition rate of alcohol is preferably 10 to 300 parts by mass with respect to the silica solid content in the solution.

In the above first and second seed liquid production steps, when an alkyl ammonium salt is added,
There is an advantage that the aggregation of seed particles is promoted and the production time of the seed solution is shortened. Furthermore, the effect of increasing the stability of the silica aggregate particle dispersion liquid can be obtained by adding the alkyl ammonium salt. When the alkylammonium salt is not added, the viscosity rapidly increases as the concentration of the finally obtained silica aggregate particle dispersion increases, and in some cases gels in a short time. However, when an alkylammonium salt is added to prepare a silica aggregate particle dispersion liquid, such a phenomenon can be significantly reduced.

The alkylammonium salt to be added is not particularly limited, but monoalkylammonium salts such as methylammonium salt, ethylammonium salt, propylammonium salt, butylammonium salt, laurylammonium salt, stearylammonium salt, dimethylammonium salt and diethyl salt. Dialkyl ammonium salts such as ammonium salts, trimethyl ammonium salts, trialkyl ammonium salts such as triethyl ammonium salts, tetramethyl ammonium salts, tetraethyl ammonium salts, lauryl trimethyl ammonium salts, stearyl trimethyl ammonium salts, distearyl dimethyl ammonium salts, alkylbenzyl dimethyls Examples include ammonium salts, and tetraalkylammonium salts. Among these alkylammonium salts, the tetraalkylammonium salt is preferable because of its high effect, and the tetramethylammonium salt is particularly preferable. When a tetramethylammonium salt is used, addition of a trace amount of the tetramethylammonium salt not only has the effect of promoting seed particle aggregation, but also has the effect of enhancing the stability of the final silica aggregate particle dispersion.

The alkyl ammonium salt is preferably added in an amount of 0.05 to 1 mass% with respect to the mass converted to SiO ₂ contained in the active silicic acid aqueous solution used in the production of the seed solution. As the method for adding the alkylammonium salt, in the first method for producing the seed solution, it is added in advance in hot water, and in the second method for producing the seed solution, it is added in advance in the active silicic acid aqueous solution. The method of setting is desirable.

The third method for producing the seed solution is a method of crushing either wet-process silica, dry-process silica, or a mixture thereof by mechanical means. Specific surface area measured by the nitrogen adsorption method 300m ² / g~1000m ² / g, and volume of pores pore diameter 100nm is 0.4 ml / g to
2.0 ml / g, preferably 0.5 ml / g to 2.0 m
Either 1 / g of wet process silica, dry process silica, or a mixture thereof can be pulverized by some mechanical means to produce a seed solution. As silica, dry method silica is preferable because it is easier to grind.

As mechanical means, an ultrasonic homogenizer, a pressure homogenizer, a nanomizer, a high speed rotation mill, a roller mill, a container driving medium mill, a medium stirring mill,
A mechanical method such as a jet mill or a sand grinder may be used, and these means may be combined. The pulverization is preferably wet pulverization of silica dispersed in water, and in this case, it can be immediately used as a seed solution in the present invention. In the case of dry pulverization, the pulverized silica is dispersed in water, and if necessary, wet pulverization is performed to obtain a seed liquid.

By using the above-mentioned method for producing the seed solution and the method for producing the silica aggregate particle dispersion by growing the seed solution, the particle diameter is 1 μm or less and the pore diameter is 100 n.
Silica aggregate particles having a pore volume of m or less and 0.4 to 2.0 ml / g can be produced. The most preferable silica aggregate particle dispersion has a specific surface area of 50 by the nitrogen adsorption method.
m ² / g~500m ² / g, a silica aggregate particle dispersion silica aggregate particles are dispersed in colloidal volume of pores pore diameter 100nm is 0.4ml / g~2.0ml / g And the main peak of the mass-equivalent particle size distribution measured by using a laser particle sizer by the dynamic light scattering method is 10 nm to 7
Dispersion of silica aggregate particles having a sharp particle size distribution in the range of 0 nm, the standard deviation of which is 10 nm or less, and the cumulative weight of the main peak is 80% or more of the cumulative total weight including peaks other than the main peak. It is a liquid.

Furthermore, the specific surface area by the nitrogen adsorption method is 50.
m ² / g~500m ² / g, a silica aggregate particle dispersion silica aggregate particles are dispersed in colloidal volume of pores pore diameter 100nm is 0.4ml / g~2.0ml / g Highly transparent silica aggregate particle dispersion liquid having an absorbance at a wavelength of 560 nm of 0.3 or less at a solid content concentration of 1.0 mass% and an absorbance at a solid content concentration of 10.0 mass% of 0.3 or less. Is preferred.

Next, a method for cation modification of silica aggregate particles will be described. The isoelectric point of silica is around pH 2,
At higher pH, the silica surface exhibits anionic character.
The cation modification may be any method as long as it makes the surface cationic, and the most preferable method is mixing of a cation resin, and the mixing method is not particularly limited.
The methods disclosed in JP-A-190, JP-A-10-181191 and JP-A-2000-94830 may be used. The cationic resin is adsorbed on the surface of silica by electrostatic attraction, and as a result, the surface of silica is modified to be cationic.

Examples of the cationic resin include N, N-dimethylaminoethyl acrylate hydrochloride, N, N-dimethylaminoethyl acrylate quaternized product, N, N-dimethylaminoethyl methacrylate hydrochloride and N, N-dimethyl. Aminoethyl methacrylate quaternized product, N, N-dimethylaminopropylacrylamide hydrochloride, N, N-
Dimethylaminopropylacrylamide quaternized product, vinylimidazolium metochloride, diallyldimethylammonium chloride, diallylmethylamine hydrochloride,
Examples thereof include polymers or copolymers of monoallylamine hydrochloride, diallylamine hydrochloride and the like. Others, dicyandiamide / polyalkylenepolyamine condensate, secondary amine /
Epichlorohydrin addition polymer, polyepoxy amine,
Examples of the polymer include a polymer having a structure having a cationic property such as polyvinylamine, but are not limited thereto.

In general, the silica aggregate particles show an electric minus due to the silanol groups present on the surface, and may be thickened or aggregated when mixed with a cationic resin. The aggregate particle size tends to increase with the increase in viscosity or aggregation. In that case, it is preferable to adjust the aggregate particle size to 1 μm or less by applying mechanical pulverization force to reduce the viscosity of the dispersion liquid.

For mechanical pulverization, a homomixer, an ultrasonic homogenizer, a pressure homogenizer, a nanomizer, a high speed rotation mill, a roller mill, a container driving medium mill, a medium stirring mill, a jet mill, a sand grinder, etc. are used, but more effective. In order to disperse or pulverize, it is preferable to use pressure pulverization. The pressure pulverization of the present invention is preferably a pressure homogenizer or a nanomizer, and is generated by passing the slurry mixture through an orifice at high pressure and colliding it with a collision plate or by colliding high-speed liquid streams with each other. It is a method of crushing by cavitation, impact force, shearing force, processing pressure is 200 ~ 3500k
gf / cm ^2, more preferably 500~3500kgf / cm ^2, more preferably from 1000~3500kgf / cm ^2. Good dispersion or pulverization can be carried out by treating with the above pressure pulverization.

Further, a technique of cation-modifying the surface of the silica by coating the surface of the silica with a metal oxide or a metal hydroxide may be used. For example, US Pat. No. 3,007,878, and Japanese Patent Publication No. 2677646 are publicly known. Sho 62-2867
Japanese Unexamined Patent Publication No. 87 discloses a method in which colloidal silica is treated with an aluminum compound to modify the cation, and can be preferably used. Furthermore, a method of treating with a cationic silane coupling agent to modify the cation is also known.
For example, Japanese Patent Publication No. 2668379 and Japanese Patent Application Laid-Open No. 1-22
JP-A-58980 discloses treatment with a silane coupling agent having a primary to tertiary amine or a quaternized ammonium salt group in its molecular structure.

In the present invention, in order to obtain an image having excellent printing quality, at least two coating layers are provided on the support, and at least one layer contains the above-mentioned cation-modified fine particles of silica aggregate particles. The cation-modified fine particles may be contained in all layers, in which case an ink jet recording sheet having high water resistance can be obtained. When the cation-modified fine particles are contained in only one layer, it is preferably contained in the uppermost layer. Since the dye for inkjet is anionic, it is adsorbed by the cation-modified fine particles in the uppermost layer, and there is an advantage that an inkjet recording sheet with high printing density can be obtained. Further, the constitution in which at least two coating layers are provided is useful for preventing cracks in the coating layers. When applying a coating material containing fine particles, cracking easily occurs due to capillary force during drying. This phenomenon is remarkable as the coating amount is large, and can be solved by providing two or more coating layers and reducing the coating amount per time.

It is possible to mix a pigment other than the cation-modified fine particles in the coating layer. For example, fumed silica, amorphous silica (including cation-modified silica such as alumina), kaolin, clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, aluminum oxide, aluminum hydroxide, pseudoboehmite, calcium carbonate, Sachin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, styrene plastic pigment, urea resin plastic pigment, benzoguanamine plastic pigment, etc. A pigment is used as appropriate. In the present invention, amorphous silica (including cation-modified silica such as alumina), aluminosilicate, and calcium carbonate are preferably selected, and amorphous silica is particularly preferable.

In the present invention, the support is an absorbent support,
Any non-absorbent support may be used. Examples of the absorbent support include high-quality paper, art paper, coated paper, cast coated paper, kraft paper, and impregnated paper. From the viewpoints of high smoothness and silver salt photographic-like texture (especially whiteness and touch), photographic paper base paper is more preferable. As the non-water-absorbing support, for example, transparent or opaque support may be used, cellophane, polyethylene, polypropylene, soft polyvinyl chloride, polyester, polycarbonate,
Examples thereof include plastic films such as polystyrene, and resin-coated paper. Preventing cockling after printing,
A non-absorbent support is preferable in order to give an ink jet recording sheet a texture similar to silver salt photographic paper.

Since plastic films are expensive and it is difficult to obtain a silver salt photograph-like texture (especially whiteness and touch), high-quality paper, photographic paper base paper, art paper, whose main component is pulp, has high smoothness. A resin-coated paper obtained by coating a paper, a coated paper, or a cast-coated paper with a resin is preferable. A resin-coated paper obtained by coating a base paper for printing paper with a polyethylene resin or a polyolefin resin so as to have high smoothness is particularly preferable. Further, it is preferable that the surface opposite to the recording surface (rear surface) is also coated with a resin for the purpose of obtaining a silver salt photographic texture (especially touch) or controlling curl of the recording sheet. As the coating resin, polyethylene-based resin, polypropylene-based resin, polyester-based resin, polyolefin-based resin, polycarbonate-based resin, or the like, or those containing a mixture thereof as a main component can be used. Examples of the polyethylene-based resin include low-density polyethylene resin, high-density polyethylene resin, and linear low-density polyethylene resin. Examples of the polyester resin include polyethylene terephthalate resin, polybutylene terephthalate resin, and polyester biodegradable resin.

The thickness of the coating is not particularly limited, but is 4 to 1
It is preferably in the range of 00 μm. Preferably 5
It is 50 μm, more preferably 7 to 35 μm. If the amount is too small, the effect of coating is insufficient, and if it is too large, the texture is poor.
It is also possible to adjust the coating thickness of the recording surface and the back surface or select the coating resin in consideration of the curl of the recording medium. The coating resin is a white pigment, preferably titanium oxide, calcium carbonate,
It is also possible to contain synthetic silica or a combination of these. Most preferred is titanium oxide.

A white pigment, preferably a titanium oxide pigment, is added to a support, particularly plastic films, resin-coated paper base paper,
It is also possible to contain calcium carbonate, synthetic silica, or a combination of these. Most preferred are titanium oxide pigments. As the white pigment, synthetic silica,
Pigments such as zinc oxide, talc and kaolin can be used.

When a non-absorbent support is used as the support, it may be subjected to an adhesion treatment or an adhesion treatment in advance for the purpose of imparting or improving the adhesion between the support and the coating layer on the recording surface side. It is possible. Particularly when resin-coated paper is used, it is preferable to perform corona discharge treatment and to provide an undercoat layer of gelatin, polyvinyl alcohol, or the like. It is also possible to treat the back surface of the support for the purpose of transportability, antistatic, blocking prevention, and the like. For the back surface treatment, other constitutions such as chemical treatment or provision of a coat layer can be appropriately added.

The smoothness is not particularly limited, but 300 seconds (Oken type, J.TAPPI N
o.5) or more is preferable. Further, the opacity is not particularly limited, but in order to obtain a silver salt photograph-like texture (especially the whiteness of the visual sense), the opacity (JIS
P8138) 85 or more, more preferably 93 or more.

Usually, a pigment binder is added to the coating layer. Water-soluble resins (for example, polyvinyl alcohols such as polyvinyl alcohol, cationic polyvinyl alcohol, modified polyvinyl alcohol such as silyl polyvinyl alcohol, casein, soybean protein, synthetic proteins, starch, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose), styrene -Butadiene copolymer, methyl methacrylate-butadiene copolymer conjugated diene-based polymer latex, acrylic polymer latex, styrene-water-dispersible resin such as vinyl-based copolymer latex such as vinyl acetate copolymer, Generally, various adhesives used in the coated paper field are used alone or in combination. In the present invention, a water-soluble resin such as polyvinyl alcohol is preferably used for imparting ink absorbency and water resistance to the coating film.

The solid content mass ratio of the pigment and the binder in each coating layer is not particularly limited, but is preferably 100/5 to 100.
/ 200, more preferably 100/10 to 100/10
It is adjusted in the range of 0. If the amount of the adhesive (binder) is large, the pores between the pigments may be small and it may be difficult to obtain the ink absorption rate. If the amount is small, the coating layer is likely to be cracked. The coating amount of the ink receiving layer is not particularly limited, but is 1 to 100 g / m ² , preferably ² to 50 g.
/ M ² is adjusted. If it is less than 1 g / m ^2, it is difficult to obtain a uniform and highly smooth coating film, and the ink absorption amount is insufficient, and the ink may overflow. On the contrary, if it exceeds 100 g / m ² , the coating film tends to be cracked.

As a secondary material, an antifoaming agent is mixed and applied.
To improve workability during work and improve the wettability of the base material.
It is also possible to add a surfactant to obtain a uniform coating layer.
It is possible to prevent sticking of the coated sheet and improve paper passing.
Therefore, starch particles or synthetic resin particles may be mixed. Well
UV absorbers and light
A light resistance improver such as a stabilizer may be added.
Oxidant, SO _X, NO_XImage from the influence of
It is also possible to add a chemical that protects the.

Examples of the coating coater include various known coating devices such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a rod blade coater, a lip coater, a die coater and a curtain coater.

[0064]

[Examples] The present invention will be described in more detail below with reference to Examples. The measuring methods of the test items described in Examples and Comparative Examples are as follows. Incidentally,% representing the concentration is% by mass, and parts is parts by mass.

[Pore volume, pore diameter of silica aggregate particles,
Specific surface area measurement method] The silica aggregate particle dispersion liquid was dried at 105 ° C, and the specific surface area, pore volume, and pore size distribution of the obtained powder sample were measured by a gas adsorption method specific surface area / pore distribution measurement device [ SA3100plus type manufactured by Coulter Inc.] was used as a pretreatment, and the measurement was performed after vacuum deaeration at 200 ° C. for 2 hours. Nitrogen was used as the adsorption gas. Specific surface area is B
Using the value obtained by the ET method, the pore volume is 10
The value of the total pore volume of pores of 0 nm or less was used. The pore diameter was defined as the maximum volume fraction pore diameter in the pore distribution curve obtained from the analysis of the desorption isotherm by the BJH method.

[Measurement Method of Average Secondary Particle Diameter of Silica Aggregate Particles] A silica aggregate particle dispersion liquid is sufficiently used by using a laser particle size distribution meter (trade name LPA3000 / 3100 manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method. It was measured in a state diluted with distilled water. As the average secondary particle diameter, the value calculated from the analysis using the cumulant method was used. The weight-converted particle size distribution and its peak position particle size were determined from the particle size distribution calculated by the histogram method.

[Absorptivity Measurement Method for Silica Aggregate Particle Dispersion] Each absorbance at 560 nm of a silica aggregate particle dispersion liquid diluted with distilled water to a solid content concentration of 1% by mass and 10% by mass or concentrated by an evaporator was measured by spectrophotometric measurement. Total [Co., Ltd.
Hitachi, U-2000 type double beam spectrophotometer].

[75 ° Gloss Measurement Method for Inkjet Recording Sheet] It was measured according to JIS standard P8142.

[Method for measuring print density of ink jet recording sheet] Ink jet printer (PSON, P
100% in PM photo paper print mode of M-900C)
Black, 100% yellow, 100% cyan, 100
Solid printing was performed for the four colors of% magenta, and measurement was performed using a Macbeth reflection densitometer (Macbeth, RD-920), and the average value of the four colors was used.

[Criteria for judging cracks in coating layer] 5 points: No cracks or cracks at all. 4 points: Part of the coating layer has cracks. 3 points: Cracks are formed on the entire surface of the coating layer. 2 points: Cracks are generated on the entire surface, and when the surface is touched, the fragments are peeled off. 1 point: Cracks were generated on the entire surface, and fragments were spontaneously peeled off during drying.

[Preparation of silica aggregate particle dispersion A] (Preparation of active silicic acid aqueous solution) SiO ₂ concentration 30%, Si
Sodium silicate solution having an O ₂ / Na ₂ O molar ratio of 3.1 [(Ltd.)
Tokuyama, No. 3 sodium silicate] mixed with distilled water, Si
A dilute aqueous solution of sodium silicate having an O ₂ concentration of 4.0% was prepared.
This aqueous solution was passed through a column packed with a hydrogen type cation exchange resin [manufactured by Mitsubishi Chemical Corporation, Diaion SK-1BH] to prepare an active silicic acid aqueous solution. The obtained active silicic acid aqueous solution had a SiO ₂ concentration of 4.0% and a pH of 2.9.

(Preparation of seed solution) In a 5 liter glass reaction vessel equipped with a reflux condenser, a stirrer and a thermometer, 500
g of distilled water was heated to 100 ° C. This hot water is 100 ℃
While maintaining the above, a total of 450 g of the above active silicic acid aqueous solution was added at a rate of 1.5 g / min to prepare a seed solution. The physical properties of the seed aggregate particles in this seed solution were an average secondary particle diameter of 184 nm, a specific surface area of 832 m ² / g, a pore volume of 0.60 ml / g, and a pore diameter of 4 nm.

(Preparation of Silica Aggregate Particle Dispersion) In the above glass reaction vessel, 0.015 mol of ammonia was added to 950 g of the above seed solution to stabilize, and 100
Warmed to ° C. A total of 550 g of the above active silicic acid aqueous solution was added to this seed liquid at a rate of 1.5 g / min. After the addition of activated silicic acid, the solution is kept at 100 ° C.
The mixture was heated to reflux for 9 hours to obtain a silica aggregate particle dispersion liquid. The dispersion is a bluish transparent solution with a pH
Was 7.2. The properties of this silica aggregate particle dispersion have an average secondary particle diameter of 130 nm and a specific surface area of 257 m ² /
g, pore volume 1.01 ml / g, pore diameter 16 nm; weight-converted particle size distribution (particle size at main peak position 31 nm, cumulative weight of main peak 90%, standard deviation 3 nm); absorbance at 560 nm (0 at solid content concentration 1% .10, and a solid content concentration of 10% was 0.
16). As shown in FIG. 1, a transmission electron micrograph of the obtained silica aggregate particles shows that primary particles of silica are irregularly bonded to form secondary particles, forming a large amount of voids. It could be confirmed. The dispersion was concentrated with an evaporator to a silica concentration of 10% and used for manufacturing an inkjet recording sheet.

[Preparation of Silica Aggregate Particle Dispersion B] (Preparation of Seed Liquid) In the same reaction vessel used for the production of silica aggregate particles A, the same active silicic acid aqueous solution as silica aggregate particles A was used. 400g at 100C at a rate of 2C / min
The temperature was raised to 100 ° C., and the temperature was maintained at 100 ° C. for 40 minutes to prepare a seed solution. The physical properties of the seed aggregate particles in this seed solution are as follows: average secondary particle size 113 nm, specific surface area 480 m ^2.
/ G, the pore volume was 0.91 ml / g, and the pore diameter was 7 nm. (Preparation of Silica Aggregate Particle Dispersion) Subsequently, 0.1 mol of ammonia was added to 400 g of the above seed liquid to stabilize the mixture, and the mixture was heated to 100 ° C. For this seed solution,
The above active silicic acid aqueous solution was added at a rate of 1.5 g / min for a total of 6
00g was added. After the addition of the activated silicic acid was completed, the solution was kept at 100 ° C. and refluxed for 9 hours to obtain a silica aggregate particle dispersion liquid. The dispersion was a bluish transparent solution and had a pH of 6.7. The properties of this silica aggregate particle dispersion are as follows: average secondary particle diameter 106 nm, specific surface area 268 m ² / g, pore volume 0.76 ml / g, pore diameter 1
2 nm; particle size distribution by weight (main peak position particle size: 17 n
m, main peak cumulative weight 97%, standard deviation 2 nm); 56
The absorbance was 0 nm (0.07 at a solid content of 1% and 0.13 at a solid content of 10%). This dispersion was concentrated with an evaporator to a silica concentration of 14% and used for the production of an inkjet recording sheet.

[Manufacturing Method of Silica Aggregate Particle Dispersion C] Synthetic amorphous silica having an average aggregate particle size of 13.1 μm manufactured by the gel method (manufactured by Grace Devison, trade name: Silojet P612, specific surface area 290 m ² / g) was dispersed in water at a concentration of 20%, and a slurry of which pH was adjusted to 9.0 by adding ammonia water was used as a horizontal bead mill (manufactured by Shinmaru Enterprises Co., Ltd., Dyno Mill KDL-).
Pilot) was repeatedly pulverized and dispersed to prepare a 20% aqueous dispersion of silica aggregate particles having an average secondary particle diameter of 300 nm. The pore volume of this silica fine pigment is 0.7 ml /
It was g.

[Manufacturing Method of Silica Aggregate Particle Dispersion D] Silica having an average primary particle size of 7 nm manufactured by a vapor phase method (manufactured by Nippon Aerosil Co., Ltd., trade name: AEROSIL3)
00) was dispersed in water at a concentration of 10%, and the pH was adjusted to 2.5 with hydrochloric acid.
After adjusting to, hydraulic ultra-high pressure homogenizer (manufactured by Mizuho Industry Co., Ltd., Microfluitizer M110-E /
H) was dispersed 3 times to prepare a 20% aqueous dispersion of silica-silica aggregate particles having an average secondary particle diameter of 250 nm. The pore volume of the silica aggregate particles was 1.2 ml / g.

[Method of cation modification] A 20% aqueous solution of diallyldimethylammonium chloride / acrylamide copolymer (manufactured by Nitto Boseki Co., Ltd., trade name: PAS-J-81) was used as a cationic resin in the silica aggregate particle dispersion liquid. Was added. The mixing ratio was such that the solid content of the cationic resin was 10 parts with respect to the solid content of 100 parts of silica. The thickened mixture is 1500k with a hydraulic ultra-high pressure homogenizer (Mizuho Kogyo, Microfluidizer M110-E / H).
Cation modification was carried out by treating twice at a pressure of g / cm ² .

[Manufacture of support base paper] CSF (JIS P
-8121) beaten conifer bleached kraft pulp (NBKP) up to 250 ml, and CSF beaten up to 280 ml hardwood bleached kraft pulp (LBKP) were mixed at a weight ratio of 2: 8 to obtain a concentration of 0.5%. A pulp slurry was prepared. In this pulp slurry, cationized starch 2.0%, alkyl ketene dimer 0.4%, anionized polyacrylamide resin 0.1 to absolute dry weight of pulp.
%, Polyamide polyamine epichlorohydrin resin 0.
7% was added and thoroughly stirred to disperse. Paper making with a Fourdrinier machine pulp pulp of the above composition, a dryer,
180 g of basis weight through size press and machine calendar
/ M ² and a tenacity of 1.0 g / cm ³ were produced. The size press liquid used in the size press step was prepared by mixing carboxyl-modified polyvinyl alcohol and sodium chloride in a weight ratio of 2: 1 and adding the mixture to water to dissolve by heating to a concentration of 5%. A total of 25 ml of this was applied on both sides of the paper to obtain a base paper.

[Manufacture of support] After the support base paper was subjected to corona discharge treatment on both sides, the following polyolefin resin composition 1 mixed and dispersed by a Banbury mixer was coated on the felt side of the base paper at a coating amount of 25 g / m 2. ² and the coating amount of the polyolefin resin composition 2 (resin composition for back surface) on the wire surface side to 20 g / m ² ,
It is applied by a melt extruder having a die (melting temperature 320 ° C.), and is cooled and solidified by a cooling roll having a mirror surface on the felt side and a rough surface on the wire side to obtain a smoothness (Oken type, J.TA.
PPI No. 5) is 6000 seconds, opacity (JIS P
8138) produced a 93% resin coated support. (Polyolefin resin composition 1) 35 parts by mass of long-chain low-density polyethylene resin (density 0.926 g / cm ³ , melt index 20 g / 10 minutes), low-density polyethylene resin (density 0.919 g / cm ³ , melt index 2 g) / 10 minutes) 50 parts by mass, anatase type titanium dioxide (A-220; made by Ishihara Sangyo) 15 parts by mass, zinc stearate 0.1 parts by mass, antioxidant (Irganox101).
0: Ciba Geigy) 0.03 parts by mass, ultramarine blue (Blue mouth ultramarine No. 2000; manufactured by Daiichi Kasei) 0.09 parts by mass, optical brightener (UVITEX OB; Ciba Geigy) 0.3 parts by mass (polyolefin resin) Composition 2) 65 parts by mass of high-density polyethylene resin (density 0.954 g / cm ³ , melt index 20 g / 10 min), low-density polyethylene resin (density 0.924 g / cm ³ , melt index 4 g / 10 min) 35 mass Department

[Preparation of Binder Aqueous Solution] Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA-140) in water
H, degree of polymerization: 4000, degree of saponification: 99% or more) were mixed and heated at 90 ° C. for 2 hours with stirring to prepare an aqueous solution having a concentration of 7%.

Example 1 A support was coated with a coating solution prepared by mixing 100 parts of silica aggregate particle dispersion C and 57 parts of a binder aqueous solution with a Mayer bar so that the dry weight was 25 g / m ^2, and the coating was carried out at 100 ° C. It dried and provided the 1st coating layer. Subsequently, a coating solution obtained by mixing 100 parts of the cation-modified silica aggregate particle dispersion A and 28.6 parts of a binder aqueous solution was applied with a Meyer bar so that the dry weight was 5 g / m ^2, and at 100 ° C. By drying, a second coating layer was provided to produce an inkjet recording sheet of the present invention.

Example 2 A first coating layer was provided in the same manner as in Example 1. Then, 100 parts of a cation-modified silica fine particle dispersion liquid B,
A coating solution obtained by mixing 40 parts of a binder aqueous solution was applied with a Meyer bar so that the dry weight was 5 g / m ^2, and
A second coating layer was provided by drying at 0 ° C. to produce an inkjet recording sheet of the present invention.

Example 3 Cation-modified silica aggregate particle dispersion B on a support
A coating liquid obtained by mixing 100 parts and 40 parts of a binder aqueous solution was applied with a Meyer bar to a dry weight of 25 g / m ² , and dried at 100 ° C. to form a first coating layer. Subsequently, a cation-modified silica aggregate particle dispersion A100
Part, and a coating solution obtained by mixing 28.6 parts of a binder aqueous solution with a Mayer bar to a dry weight of 5 g / m ² and drying at 100 ° C. to form a second coating layer, The inkjet recording sheet of the present invention was manufactured.

Example 4 Dispersion A10 of silica aggregate particles without cation modification
A coating solution prepared by mixing 0 parts and 28.6 parts of a binder aqueous solution was coated with a die coater to a dry weight of 12.5 g / m ² and dried at 100 ° C., and the same coating solution was dried with a die coater. To be 12.5 g / m ² 10
It was dried at 0 ° C. Further cation-modified silica dispersion B
A coating liquid prepared by mixing 100 parts and 40 parts of a binder aqueous solution was applied with a die coater to a dry weight of 5.0 g / m ² and dried at 100 ° C.

Comparative Example 1 A first coating layer was provided in the same manner as in Example 1. Subsequently, a coating liquid prepared by mixing 100 parts of the silica aggregate particle dispersion liquid A and 28.6 parts of a binder aqueous solution is applied with a Meyer bar to a dry weight of 5 g / m ^2, and dried at 100 ° C. Thus, a second coating layer was provided to obtain an inkjet recording sheet of Comparative Example.

Comparative Example 2 A first coating layer was provided in the same manner as in Example 1. Subsequently, a coating solution obtained by mixing 100 parts of the silica aggregate particle dispersion liquid B and 40 parts of the binder aqueous solution is applied with a Meyer bar to a dry weight of 5 g / m ^2, and dried at 100 ° C. A second coating layer was provided to make an inkjet recording sheet of a comparative example.

Comparative Example 3 The first coating layer was provided in the same manner as in Example 1. Subsequently, a cation-modified silica aggregate particle dispersion liquid C100
Part, and a coating solution containing 57 parts of a binder aqueous solution are applied by a Mayer bar to a dry weight of 5 g / m ² ,
A second coating layer is formed by drying at 100 ° C,
The inkjet recording sheet of Comparative Example was used.

Comparative Example 4 A first coating layer was provided in the same manner as in Example 1. Subsequently, a cation-modified silica aggregate particle dispersion D100
Part of the coating solution and 28.6 parts of a binder aqueous solution are applied by a Meyer bar to a dry weight of 5 g / m ² and dried at 100 ° C. to form a second coating layer. The inkjet recording sheet of Comparative Example was used.

Comparative Example 5 An attempt was made to produce an ink jet recording sheet with one layer instead of two coating layers. A coating solution prepared by mixing 28.6 parts of a binder aqueous solution with 100 parts of the cation-modified silica fine particle dispersion A was dried on a support with a Mayer bar to give a dry weight of 3
When it was coated at 0 g / m ² and dried at 100 ° C., cracks were generated on the entire surface, and the coating layer was in a state of being easily peeled off from the base material. Therefore, print density measurement and 7
The 5 degree gloss could not be measured.

Table 1 shows the production conditions such as the layer structure of Examples and Comparative Examples, and the type of silica aggregate particle dispersion liquid used for the coating layer. In addition, Table 2 summarizes the quality of the inkjet recording sheets manufactured in Examples and Comparative Examples.

[0091]

[Table 1]

[0092]

[Table 2]

As shown in the examples, it is produced by condensing activated silicic acid and has a particle size of 1 μm or less and a pore size of 10 μm.
The ink jet recording sheet using the cation-modified fine particles of silica aggregate particles having a pore volume of 0 nm or less of 0.4 to 2.0 ml / g as a coating layer has high print density and gloss, It had a similar texture and was suitable for printing a full-color image. The silica aggregate particle dispersion liquid adopted in the present invention has a very fine particle size but a high pore volume, and further has a sharp particle size distribution or excellent transparency, so a coating layer containing this Has a high transparency. Furthermore, because it is cation-modified,
The dye in the inkjet ink can be effectively adsorbed, and a vivid full-color image with high color density can be obtained. Comparative Examples 1 and 2 are examples using silica aggregate particles that are not subjected to cation modification, but the print density was poor, probably because the dye in the ink was not fixed to the surface layer.
When the cation-modified fine particles of silica aggregate particles produced by pulverizing commercially available gel-processed silica were used, the print density and gloss were significantly inferior to those of the examples. When the cation-modified particles of the silica aggregate particles produced by crushing dry silica were used, the print density and gloss were improved, but still not as high as those of the examples.

[0094]

When a full-color photograph is printed on the ink jet paper of the present invention, a high print density is obtained and the color reproduction area is wide. Moreover, since it has high gloss, it has a texture close to that of photographic paper and is suitable as a substitute for silver halide photography.

[0095]

[Brief description of drawings]

FIG. 1 shows an electron micrograph of silica aggregate particles used in the present invention (110,000 times). Silica aggregate particles in which primary particles are irregularly bonded are observed.

Claims (3)

[Claims] 1. An inkjet recording sheet having a support provided with at least two coating layers, wherein at least one of the coating layers has a silica aggregate particle size of 1 μm produced by condensing activated silicic acid. An inkjet recording sheet characterized by comprising cation-modified fine particles of silica aggregate particles having a pore size of 100 nm or less and a pore volume of 0.4 to 2.0 ml / g. 2. In an ink jet recording sheet having a support provided with at least two coating layers, at least one of the coating layers has an active silicic acid aqueous solution added dropwise to hot water or an active silicic acid aqueous solution. To generate silica seed agglomerate particles, stabilize the silica seed agglomerate particles by adding an alkali before the dispersion causes precipitation or gelling, and then keep the active state while maintaining the stable state. A cation of silica aggregate particles having an aggregate particle size of 1 μm or less and a pore volume of 0.4 to 2.0 ml / g, in which the silica seed aggregate particles are grown by adding an aqueous acid solution little by little. An ink jet recording sheet containing modified fine particles. 3. The silica seed agglomerate particles contain S at a rate of adding an active silicic acid aqueous solution while maintaining a stable state.
0.001 converted to SiO ₂ with respect to 1 mol of iO ₂
The inkjet recording sheet according to claim 2, which is added at a rate of 0.2 mol / min.