JPS61141584A - Filler for ink jet recording paper and its recording paper - Google Patents

Abstract

PURPOSE:To obtain an ink jet recording paper showing little rise in the viscosity of a coating material, little deformation and little spreading of ink dots and rapid ink absorption, by providing a coated layer comprising a filler consisting of specified amorphous silica and a water-soluble high molecular weight binder, in which the silica content is specified. CONSTITUTION:The amorphous silica used as the filler has an average particle diameter of 2.5-3.5mum, such a particle size distribution that particles with a particle diameter of not smaller than 10mum constitute not more than 0.5% of the whole while particles with a diameter of not larger than 0.9mum constitute not more than 10% of the whole, pores with a size of 60-130Angstrom in an amount of not more than 20% of the total amount of pores, and a specific surface area of 240-400m<2>/g. The pore diameter distribution of the silica is controlled mainly by the Na2O concentration and Sio2 concentration of a reaction liquid, the degree of neutralization and the reaction temperature, while the specific surface area is controlled by the reaction temperature, the SiO2 concentration and the degree of neutralization. The concentration of the filler in the coating material is 10-25wt%, and the weight ratio of the filler to the water-soluble high molecular weight binder is about 0.8-10. The coated layer provided on a paper is so provided that the amorphous silica as the filler is present in an amount of 2-14g/m<2>.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a novel additive used in the recording layer of inkjet recording paper and recording paper using the same. [Prior Art] The characteristics required of recording paper used for printing using the inkjet recording method are: ■ fast absorption speed of ink deposited on the paper surface, ■ small spread of ink dots, and ■ ink dots that do not deform. There are things you don't do. The characteristic (1) above is mainly necessary to speed up the drying of the ink dots, and the characteristics (2) and (3) are necessary to improve the clarity of the recorded image. Conventionally, as a method of imparting such characteristics to inkjet recording paper, a method of forming a recording layer by coating the paper surface with a paint obtained by mixing a liquid-absorbing additive and a binder has been generally known. There is. For example, as an additive 0.
Amorphous silica with a particle size of l to lOμ, average particle size 0.
Amorphous silica and the like having an average particle size of 0.05 μm or less have been proposed. [Problems to be solved by the invention] However, amorphous silica used as an additive,
If the particle size is too small, the viscosity increases when mixed with the binder, making it difficult to apply the resulting paint to the paper surface, and also making it impossible to increase the concentration of amorphous silica in the binder, resulting in insufficient properties. If an attempt is made to form a recording layer having such a thickness, there is a problem in that the thickness of the layer becomes thick. Furthermore, if the particle size of the amorphous silica is increased, the above problem can be solved, but among the characteristics required of the recording paper described above, in particular, there is the problem that deformation of the ink dots easily occurs and the recorded image becomes unclear. occurs. [Means for Solving the Problems] The present inventors have developed an ink dot that has an appropriate particle size that causes little increase in viscosity when mixed with a binder, has little deformation of ink dots, and satisfies other characteristics. Intensive research was conducted to develop a filler for forming the recording layer of the inkjet recording paper obtained. As a result, the inventors discovered that amorphous silica having a specific particle size distribution and pore size distribution can satisfy all of these objectives, and completed the present invention. The present invention has an average particle size of 2.5 to 3.5μ, and a particle size of 1
60-130A, with a particle size distribution of 0.5% or less of particles with a size of 08 or more and 10% or less of particles with a particle size of 0.9μ or less,
A filler for inkjet recording paper made of amorphous silica having pores within the range of 20% or more of the total pores, and such amorphous silica and a water-soluble polymer binder, wherein the amorphous silica is 2 to 20% of the total pores. Provided is an inkjet recording paper characterized by having a coating layer present at a rate of 14 g/m2. In addition, in the present invention, the particle size is determined by Coulter counter (
COUl, made by TERELECTRONIC5INC)
The specific surface area and pore diameter refer to the values measured by the nitrogen adsorption method using the TA-11 type. In the present invention, the amorphous silica is 2.5 to 3°5μ,
Preferably, it is necessary to have an average particle size of 2.8 to 3.5 microns. If the average particle size is smaller than the above range, the viscosity of the paint will increase significantly when mixed with a binder and applied.
It becomes difficult to form a uniform recording layer. Furthermore, if the average particle size is larger than the above range, the surface smoothness of the resulting recording layer will decrease, leading to deformation of the ink dots. It has a particle size distribution such that the proportion of the above particles is 0.5% or less, preferably 0.2% or less, and the particle size of 0.9μ or less is 10% or less, preferably 8% or less. is necessary. If the number of particles having a particle size of 10) or more exceeds the above range, the surface smoothness of the resulting recording layer will decrease, leading to increased deformation of ink dots. Furthermore, if the number of particles having a particle size of 0.9 μm or less exceeds the above range, deformation of ink dots in the resulting recording layer tends to increase. Further, in the present invention, the amorphous silica is 60 to 1 aoi
20% or more of the total pores, preferably 30% or more of the total pores. That is, as a result of numerous experiments on the properties of amorphous silica used as a filler for inkjet recording paper, the present inventors found that the properties of the recording layer formed by the filler, especially the deformability of ink dots, are simply due to the particle size distribution. They also found that it is not determined by the specific surface area, which will be described later, but is greatly influenced by the proportion of 60 to 130A pores. Therefore,
If the proportion of 60 to 130A pores is less than the above range, there is a problem that the ink dots in the resulting recording layer often deform.In this case, if the distribution deviates to pores smaller than BOA, the ink dots in the recording layer will deform. If the distribution deviates to pores larger than 130A, the problem of increased spread of ink dots in the recording layer also occurs. Moreover, the above pore distribution is 60
It is more preferable to have the highest peak of the distribution at ~130A. In the present invention, other properties of the amorphous silica used as a filler for inkjet recording paper are not particularly limited, but for example, oil absorption is 250 m1/100 g or more,
Preferably, it is 270 all/100 g or more in order to further increase the absorption speed of ink in the resulting recording layer. Also, 240 to 400 m1/g,
Preferably, it is preferable to have a specific surface area of 260 to 360 mZ/g in order to reduce deformation of ink dots in the resulting recording layer in combination with the above-mentioned particle size distribution and pore size distribution. stomach. The method for producing amorphous silica of the present invention is not particularly limited.
While maintaining a sodium silicate aqueous solution with a molar ratio of 2.95 to 3.10-5iO2 concentration of 4.6 to 5.0% by weight containing 0.46 to 0.5% by weight as ago at 35 to 40°C,
Sulfuric acid with a concentration of 22 to 24% by weight was added to the aqueous solution within 10 minutes in an amount that would make the first stage neutralization rate in the sodium silicate 48 to 55%, and then 93% by weight was added in 25 to 30 minutes. ~9
The temperature was raised to 5°C, and when the viscosity reached the maximum while stirring, the sulfuric acid was added until the pH of the reaction solution became 3.0 to 3.5, and the obtained amorphous silica was filtered and washed with water. and a method of air-flow pulverization after drying. In the above method, the pore size distribution can be adjusted mainly by the Na20 concentration in the reaction solution, the SiOJ degree, the neutralization rate, and the reaction temperature, and the specific surface area can be adjusted mainly by the reaction temperature, SiO concentration , can be adjusted by the neutralization rate. In addition, the particle size distribution is mostly determined by the hardness of the amorphous silica, which affects the ease with which it is divided during air-flow milling, and the hardness is determined by the molar ratio of sodium silicate in the amorphous silica production reaction, S + O, 11 degrees, The concentration of Glauber's salt is adjusted by adjusting the amount of sulfuric acid added in the first stage within the above range. A known pneumatic pulverizer is used for such pneumatic pulverization, but it is desirable to use air or other inert gas as the fluid and avoid using water vapor to prevent the formation of fine particles. The amorphous silica, which is the additive of the present invention, can be used to form a coating layer on the paper surface by a known method to obtain inkjet recording paper.For example, the binder may be polyvinyl alcohol, starch, or water-soluble cellulose derivative. Known water-soluble polymeric binders such as the like are generally used. Further, the appropriate concentration of the additive in the paint is 10 to 25% by weight. Furthermore,
The t-electro ratio of the additive/water-soluble polymer binder is generally 0.8.
The coating layer formed on the paper surface with such a paint, which is preferably about 10 to 10%, contains 2 to 14% amorphous silica as an additive.
By coating the additive at a ratio of 1 g/m', preferably 4 to 10 g/m', the effect of the additive of the present invention can be fully exhibited. [Effect] As understood from the explanation below, according to the present invention,
There is little increase in the viscosity of the paint obtained by mixing with the binder, which improves coating work, and reduces the deformation and spreading of ink dots.

[Also, it is possible to obtain an inkjet recording paper having a recording layer that absorbs ink quickly. [Examples] Examples are shown below to further specifically explain the present invention, but the present invention is not limited to these examples.
In addition, various tests in Examples and Comparative Examples were conducted by the following methods. (1) Particle size distribution measurement Add a small amount of sample to a methanol solution and disperse for 3 minutes using an ultrasonic disperser. This solution was measured using a Coulter counter method particle size distribution analyzer (cout, TEREl, ECTR).
0NIC5INs! i1T A-TI type) diameter 5
Measurements were made using an aperture of 0μ. (2) Specific surface area measurement Measurement was performed using a Bet type specific surface area meter using simple N2 adsorption. (3) Pore size distribution I and pore volume C were measured using a pore size distribution measuring device SORPTOMAT I C (trade name) manufactured by ARLOERBA using the N-adsorption method. (4) Evaluation of recorded images Recorded images formed using the Roku Konishi inkjet printer R-180 were evaluated on the following three items. a) Measure the dot area using the dot diameter recorded image using a particle analyzer (Viewback 75■ Nippon Regulator!),
The average dot diameter of the image quality per dot was determined. b) Observe the dots in the dot shape recording image under magnification using a louver, and score 8 if the percentage of shapes close to a perfect circle is 95% or more, and 95 if the percentage is 70% or more.
Less than % was evaluated as B, and less than 70% was evaluated as C. C) Absorption time of ink 0.05 cc of ink (BX-204) manufactured by Large H Honyo Paint (1) was dropped onto the paper surface from a height of 1 CI 11 using a microsyringe, and the time until it was completely absorbed was measured. (2) Preparation of recording paper Add 1 100 100 O of a 15% aqueous solution of polyvinyl alcohol (PVA PC-100 manufactured by Denki Kagaku) to 1 1 of hydrated silicic acid powder.
50g was added and thoroughly mixed using a lab mixer to prepare a paint. Recording paper was obtained by applying this paint to a high-quality paper with a basis weight of 80 g/m'' at a coating weight of 13 g/m2.The viscosity of the paint was also measured. Example 1 Commercially available sodium silicate ( S j 02/N ago molar ratio 3
゜04, S 102 26.48%) 8.16 Garden and N
a2S 04 (N a, 02, 15%) 10.47
m, water 2B, and 37■3 were placed in a 60113 internally heated reaction tank with stirring blades, and while stirring, sulfuric acid (22g/100n) was added.
+l) 2.531 was added over about 10 minutes to perform the first stage of acid addition. After the addition was completed, water vapor was blown into the solution while stirring, and the temperature was raised to 95° C. over 30 minutes. After raising the temperature, aging was performed at the same temperature for 7 minutes. After that, neutralization was resumed, and the sulfuric acid 2.63% was added to neutralize the remaining alkali.
m+3 was added over a period of 90 minutes, and the pH of the solution was adjusted to 3.0~
The reaction was completed so that the value was within the range of 3.5. This solution was then filtered, washed with water, and dried with a spray dryer. Thereafter, this dried material was crushed using a jet-o-mizer at a feed rate of 30 kg/Hr and a crushing pressure of 5°5 kg/c.
The additives shown in Table 1 were obtained by grinding with a+. Table 1 also shows the results of measuring powder physical properties and image characteristics of inkjet paper using this additive. Example 2 The dried product obtained in the same manner as in Example 1 was crushed using a jet-o-mizer at a feed rate of 40 kg/Hr and a crushing pressure of 5.
An additive was obtained by grinding at 5 kg/cn+. Example 1
The results measured in the same manner as above are also shown in Table 1. Example 3 A dried product was obtained in the same manner as in Example 1 except that the aging temperature after heating was changed to 90°C. This dried material is supplied with a jet-o-mizer at a feed rate of 30 kg/Hr and a crushing pressure of 5.5 k.
The additives shown in Table 1 were obtained by grinding with g/c+w. The results of measuring this additive using the same test method as in Example 1 are also shown in Table 1. Example 4 Commercially available sodium silicate (S j 02/N & molar ratio 3
02.5j0227-11%) 2.30m and water 10°7san3 were placed in a 20113 internally heated reaction tank with stirring blades, and while stirring, sulfuric acid (22g/100n+1) 0.
77-3 was added over about 10 minutes to perform the first stage of acid addition. When the addition is finished, blow in water vapor while stirring and boil for 30 minutes.
The temperature is raised to 92°C in minutes. After raising the temperature, aging was performed at the same temperature for 30 minutes. After that, neutralization was started, and in order to neutralize the remaining alkali, the above-mentioned sulfuric acid 0.76Il13 was added over 14 minutes, stirred at the same temperature for 40 minutes, and after the reaction was completed, the solution was filtered and washed with water. , and dried with a micro dryer to obtain a dried product. This dried material was crushed using a jet-o-mizer at a feed rate of 34 kg/llr and a crushing pressure of 6.0 kH/c+.
The additives shown in Table 1 were obtained by grinding with w. The results of measurements performed in the same manner as in Example 1 using this additive are also shown in Table 1. Comparative Example 1 The dried product obtained in Example 1 was supplied at a rate of 125 kg/H.
r, the first obtained by crushing at a crushing pressure of 6.0 kg/c■
The measurement results of each test method for the additive shown in the table are also shown in Table 1. Comparative Example 2 In Example 1, the amount of sulfuric acid added in the first stage was changed to 2°37-°
Table 1 shows the measurement results of each test method for the additives shown in Table 1, which were obtained in the same manner except that the number was changed to 3. Comparative Example 3 The dried product obtained in Example 1 was supplied at a rate of 150 kg/H.
r, the first obtained by crushing at a crushing pressure of 5.5 kg/c-
The measurement results of each test method for the additive shown in the table are also shown in Table 1. Comparative Example 4 60 kg of Tokusil P (manufactured by Tokuyama Soda Co., Ltd.) supplied
Table 1 also shows the measurement results of each test method for the additives shown in Table 1 obtained by grinding at a grinding pressure of 4 kg/Hr and a grinding pressure of 4 kg/Hr. Comparative Example 5 Using the dried material obtained in Example 4 as a crushing energy source,
Using 30kg/c-steam, supply rate 50kg/Hr,
Table 1 shows the measurement results of each test method for the additive shown in Table 1 obtained by crushing at a crushing pressure of 12 kg/c+s. Comparative Example 6 The dried product obtained in the same manner as in Example 3 was supplied in an amount of 35 k.
Table 1 shows the measurement results of each test method for the additives shown in Table 1 obtained by grinding at a grinding pressure of 5.0 kg/Hr and a grinding pressure of 5.0 kg/c-. Example 5 The dried product obtained in the same manner as in Example 1 was fed using a similar crusher at a feed rate of 25 kg/Hr and a crushing pressure of 5 kg/c.
- to obtain the additives shown in Table 1. Table 1 shows the measurement results of the obtained additives in each test. Comparative Example 7 The dried product obtained in the same manner as in Example was pulverized under different pulverization conditions to obtain the additives shown in Table 1. Table 1 also shows the measurement results of the obtained additives in each test.

Claims (3)

[Claims] (1) Average particle size is 2.5-3.5μ, particle size 10μ
It has a particle size distribution of 0.5% or less of the above particles and 10% or less of particles with a particle size of 0.9 μ or less, and 60 to 130 Å
A filler for inkjet recording paper comprising amorphous silica having pores within the range of 20% or more of the total pores. (2) The filler for inkjet recording paper according to claim 1, wherein the amorphous silica has an oil absorption amount of 250 ml/100 g. (3) has a particle size distribution with an average particle size of 2.5 to 3.5 μ, 0.5% or less of particles with a particle size of 10 μ or more, and 10% or less of particles with a particle size of 0.9 μ or less; ~130Å
A coating consisting of amorphous silica having pores within the range of 20% or more of the total pores and a water-soluble polymer binder, in which the amorphous silica is present at a ratio of 2 to 14 g/m^2 An inkjet recording paper characterized by having a layer.