JPS62270378A - Recording paper - Google Patents

Abstract

PURPOSE:To obtain sharp high image quality having no blur, by providing a particle layer wherein a particle itself absorbs no ink but the ink is held between particles and a porous particle layer absorbing ink to the surface of paper. CONSTITUTION:Particles directly contacted with paper have an average particle size of 0.05-200mum and hold ink in the gaps of 0.01-100mum therebetween and the apparent thickness of the layer formed by said particles is set to 5-300mum. A porous particle layer has function absorbing the ink held between the particles of the lower layer to form a color and the porous particles thereof have an average pore size of 10-5,000Angstrom , a pore volume of 0.05-30cc/g and an average particle size of 0.1-50mum and the apparent thickness of said layer is 1-75mum. Both layers are formed on the surface of the paper by a method wherein a non-porous particle layer is preliminarily formed and, after drying, particles having pores are applied to said layer using PVA as a binder and pressure post-treatment is further applied to both layers.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to recording paper, particularly recording paper for high-quality inkjet printers having a multi-layer or semi-continuous layer structure as a coating or coating layer. It is related to paper.

[Prior Art] Recording paper that uses ink for recording, particularly ink-aired printer paper, has a paper surface coated with porous silica-based fine powder using a water-soluble polymer such as polyvinyl alcohol as a binder. porous'! je powder absorbs ink and develops color.

[Problems to be Solved by Mei 92] However, in conventional recording paper of this type, porous fine powder that absorbs ink is simply coated on the paper surface with a binder, and furthermore, such fine powder is When it comes into contact with ink, it can absorb the entire amount instantly, but it takes some time.

For this reason, the ink droplets spread over a fairly wide range between the fine powder particles, and the closer they spread to the edges, the lighter the color becomes. There were disadvantages in that the clarity was low and color unevenness and blurring were likely to occur.

[Means for Solving the Problems] The present inventor has conducted various research and studies with the aim of eliminating the drawbacks of such conventional methods and obtaining a recording paper that can provide clear, blur-free, and high-quality images. It has been found that all of the objectives listed in (iii) can be achieved by suppressing unnecessary spread of ink droplets as much as possible and also ensuring that the necessary amount of ink droplets are absorbed into the porous particles.

Thus, the present invention provides a layer of particles on the paper surface that does not substantially absorb ink but retains ink between the particles;
The object of the present invention is to provide a recording paper having a porous particle layer for absorbing ink provided on the layer.

In the present invention, the particles that come into direct contact with the paper are particles that do not substantially absorb ink, and such particles are arranged at appropriate intervals and have an apparent thickness so that the ink can be filled into the gaps between the particles. The holding part becomes the turning part.

It is appropriate that the average particle size of such particles is about 0.05 to 200 l, preferably about 0.1 to 100 l, and if the average particle size is less than the above range, the gaps between the particles are small. If the ink droplet retention force becomes too high, the movement of the ink to the porous particles described below becomes slow, or the ink tends to be insufficiently mixed in this gap to obtain a mixed color. On the other hand, if the average particle size exceeds the above range, the holding power of the ink droplets in the gaps between the particles is weak, and there is a risk that undesirable movement of the droplets within the particle layer may occur due to paper vibration or gravity. Therefore, I don't like either of them.

Among these ranges, it is particularly preferable to adopt an average particle diameter of 1 to 30 mm because the above-mentioned fear can be avoided and the desired state can be stably obtained.

Also, the gap between particles caused by these particles is 0.01
It is appropriate to adopt ~100 loci. If the range of the gap is less than the above range or exceeds the above range, the disadvantages mentioned above regarding the particle size may occur, so both are not preferred.

And within these ranges, the gap between particles is 0.1 to 30
It is particularly preferable to employ this method because the above-mentioned fear does not occur and the desired state can be stably obtained.

Examples of means for actually creating such particle gaps include a method of coating using an organic binder such as PVA, a metal oxide sol such as silica sol, alumina sol, titania sol, and zirconia sol, or a method of using a combination thereof, and coating. The following method of controlling the thickness and the size of the interparticle gaps by applying pressure with a rear calendar roll or the like can be adopted.

The apparent thickness of the layer formed by such particles is preferably 5 to 300 tiles, preferably 10 to 100 tiles.If the apparent thickness of the three layers is less than the above range, This is undesirable because the ink retention capacity of the layer is small and the penetration of the ink into the paper increases.On the other hand, if it exceeds the above range, unnecessary coating layers increase,
Either method is undesirable since the adhesion between the paper and the coating material may be reduced and the coating layer may fall off.

When adopting a diameter of 20 to 50μ within these ranges, it is possible to accommodate various ink dot densities in terms of ink holding capacity, and by appropriately using PVA, metal oxide sol, etc., good adhesion to paper can be achieved. This is particularly preferred since a coating layer can be obtained.

Thus, such a layer is formed on the paper surface, and then a layer of porous particles that absorbs the ink is provided on top of this layer.

Such a porous particle layer develops color by absorbing the ink held in the gaps between the aforementioned lower layer particles by capillary action. Therefore, such porous particles have an average pore diameter of 10 to 5000 Å and a pore volume of 0.05 Å.
~3.0cc/g, average particle size 0.1~50, preferably average pore size 10~2000Å, pore volume 0.2~2.
It is appropriate to use 5 cc/g and an average particle diameter of 0.5 to 30 μm.

If these physical properties deviate from the above range, the ink absorption rate may be low, clear dots may not be obtained, particles may fall off after multi-layer coating, or ink dots may rapidly penetrate into the non-porous layer. This is not preferable because there is a risk that it will not work.

Among these physical properties, the average pore diameter is 100 to 500 Å.
, pore volume 1.0-2. Qcc/g, average particle size 1-1
It is particularly preferable to use 0g because there is no possibility that the above-mentioned drawbacks will occur.

The apparent thickness of the layer formed by such porous particles is preferably 1 to 75 mm, preferably 5 to 50 mm. If the apparent thickness of the layer is less than the above range, the color density of the ink dots will be low due to the lack of a coloring layer, or the ink will remain in the ink retaining layer, whereas if it exceeds the above range, the ink will Either of these is undesirable because there is a risk that a layer of particles that cannot absorb ink will be formed on the layer that absorbs the ink and develops color, or that the ink concentration will decrease because the ink spreads thinly over the entire layer. .

Among these ranges, when the range is 10 to 30, the above-mentioned drawbacks do not occur at all and it is particularly preferable.

In fact, as a means of forming both of these layers on the paper surface, for example, a pore-free particle layer is created in advance by the method described above, and after drying or semi-drying, particles having pores are coated with PVA or the metal oxide layer. It is possible to employ a method such as applying a compound sol or the like as a binder by the method described above, or further performing a pressure treatment. The average size of interparticle gaps in the non-porous layer is smaller than the average pore size in the porous layer, and preferably the former two
/3 to 1/100, particularly preferably 1/2 to 1150. If it deviates from this range, there is a risk that the absorption of ink into the coloring layer may be delayed or may not be absorbed sufficiently.

Thus, in the recording paper according to the present invention, the ink droplets ejected from the printer nozzle onto the paper surface are first held in the gaps between the particles formed in the lower layer, and the ink does not cause unnecessary flow stiffness. It is retained and then rapidly absorbed by capillary action into the porous particles forming the upper layer, making it possible to obtain sufficient color development and high image quality without color unevenness or blurring.

Furthermore, if a neutral color is required, for example, by dropping two types of ink at the same location, they will be mixed in a liquid state in the gaps between the particles forming the lower layer, and then absorbed by the upper layer particles, resulting in a mixed color. The color development has an extremely advantageous advantage.

As the material of the particles that do not substantially absorb ink and the porous particles that absorb ink used in the present invention, for example, silica, silica alumina, alumina, silica boria, silica magnesia, etc. can be used as appropriate.

[Example] 1 sulfuric acid with a concentration of 16% was added to a stainless steel beaker with a capacity of 5 liters.
After stirring well, a separately prepared diluted solution (S 10?E of about 7%) of 3-water glass was added dropwise to adjust the pH of the mixture to 3.0. Stirring was continued, and even after gelation, the mixture was stirred for about 30 minutes, and then 6N ammonia water was added dropwise to adjust the pH to 7.5. This slurry was granulated using a spray dryer to obtain approximately spherical particles with particle sizes ranging from 30 to 120 μm. This was washed with a 1% ammonium carbonate solution on a Buchner funnel to remove Na' and 5
O4-2 was removed and then calcined at 350°C for 2 hours.
Next, this was pulverized for 1 hour using a vibrating ball mill to obtain silica powder with a particle size distribution of 0.5 to 25 l, and from this a silica powder containing 35% of 1 to 12 l. The average particle size was 4.5 tiles. The pore size is distributed from 80 to 210, the average pore size is 110, and the pore volume is 1.
．． It was 1 cc/g. Next, a portion of this was placed in a crucible and fired at +ioo°C for 5 hours.

As a result, silica particles with substantially no pores were obtained, with a particle size of 0.7 to 9, with a particle size of 35% or more, and an average particle size of 3.
It was 3μ. Grind this again with a vibrating ball mill,
Silica particles were obtained in which 95% or more of the particles had a particle size of 0.2 to 5 μm and an average particle size of 2.1 μm. These two types of powder were mixed separately at silica/PVA=4/l with a solid content concentration of 17%.
A slurry was prepared.

First, a viscous slurry made from solid silica was applied onto a base paper. Once dried, a viscous slurry obtained from porous silica was coated and then pressed with a calender roll under a pressure of 20 kg/cm2. After sufficiently drying in a dryer, the thickness of both layers was examined using an electron microscope, and the thickness was approximately 20 mm and approximately 10 mm, which was approximately the same as the designed value, and the interparticle gap in the lower layer was 0.2 to 1.4 mm. .

Use this recording paper for Canon's inkjet printer project.
30QS was used to print ink dots using ink IJ20C magenta manufactured by Canon. It was observed that the color density was low at the moment when the ink dots were implanted, and that the density became high after a while. When the cross section of the dot was observed using an electron microscope, it was found that most of the ink was concentrated in the upper layer of porous silica. In addition, a small amount of ink remained or traces were observed in the lower layer. These results revealed that the ink droplets were once held between particles in the lower layer, and then migrated inside the porous silica particles in the upper layer, which had excellent coloring properties. Color density of printed ink dots was measured using Sakura Microdensitometer PDM-5 1
．． 56, and the dots were approximately circular.

Comparative Example Instead of the solid silica of the example, the porous silica used for the upper layer coating in the example was partially ground with a vibrating pole mill, and the particle size was 95% or more in ~0.2 mm, and the average particle size was Diameter is 2.1
The lower layer was coated using silica particles in the same manner as in the examples.

The upper layer was coated with the same porous silica used for coating the upper layer in the examples.

When ink dot printing was carried out using this recording paper in the same manner as in the example, the ink stayed mostly in the lower layer, and the ink color density was only 1.15.

Claims (11)

[Claims] (1) Recording paper that has a particle layer on the paper surface that holds ink between the particles without substantially absorbing ink, and a porous particle layer that absorbs ink on top of the layer. . (2) The average particle size of particles that do not substantially absorb ink is 0.
．． The recording paper according to claim (1), which has a particle size of 05 to 200μ. (3) The average particle size of particles that do not substantially absorb ink is 0
．． The recording paper according to claim (2), which has a particle size of 1 to 100μ. (4) The gap between particles that hold ink is 0.01 to 10
The recording paper according to claim (1), which has a particle diameter of 0μ. (5) The gap between particles that hold ink is 0.1 to 30μ
The recording paper according to claim (4). (6) The apparent thickness of the particle layer that holds ink is 5 to 3
00μ recording paper according to claim (1). (7) The apparent thickness of the particle layer that holds the ink is 10~
The recording paper according to claim (6), which has a thickness of 100μ. (8) Porous particles that absorb ink have an average pore diameter of 10
5000 Å, pore volume 0.05 to 3.0 cc/g, and average particle diameter 0.1 to 50 μm. (9) Porous particles that absorb ink have an average pore diameter of 10
The recording paper according to claim (8), which has a pore volume of 0.2 to 2.5 cc/g and an average particle diameter of 0.5 to 30 μm. (10) The recording paper according to claim (1), wherein the apparent thickness of the porous particle layer that absorbs ink is 1 to 75 μm. (11) The recording paper according to claim (10), wherein the apparent thickness of the porous particle layer that absorbs ink is 5 to 50 μm.