JP2008100374A - Method of manufacturing mixed liquid under decompression environment, method of manufacturing coating liquid, and method of manufacturing medium to be recorded for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid in to which foams are not mixed even in high solid concentration and even in high viscosity, and to provide media to be recorded for inkjet printing having ink receiving layers generating no coating defects such as cracks. <P>SOLUTION: The method of manufacturing the coating liquid removing foams by a mixing process carrying out turning and revolving under the decompression environment is characterized by having (a) the step of bringing the surface of silica contact with a catalyst, (b) the step of moving the foams to the liquid face by flowing the mixture from a liquid bottom portion to the liquid face by vertical convection, and (c) the step of expanding the foams in the mixture to release the same from the mixture to the decompression environment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a mixed liquid under a reduced pressure environment, and more particularly, to a method for producing a coating solution containing inorganic fine particles such as silica and a water-soluble polymer as main components and having no mixing of bubbles. The present invention also relates to a method for producing a coating liquid for forming an ink receiving layer for a recording medium for ink jet recording, which has a good surface state without defects such as cracks and has excellent ink absorbability. The present invention also relates to a method for producing a recording medium for ink jet recording in which an ink receiving layer is formed on a support using this coating solution.

  A recording apparatus to which the ink jet recording system is applied has characteristics such as high speed and low noise, easy multi-coloring, large recording pattern flexibility, and no development and fixing. For this reason, it is rapidly spreading in various applications including information equipment as various image recording apparatuses. In addition, an image formed by the multicolor ink jet recording method can obtain a recording that is comparable to multicolor printing by a plate making method or printing by a color photographic method. Furthermore, the multi-color ink jet recording system is being widely applied to the field of full-color image recording because it is cheaper than ordinary multi-color printing and printing when the number of created copies is small.

With the expansion of the use of the ink jet recording method, further improvement in recording characteristics such as high-speed recording, high definition, and full color has been required, and the recording apparatus and recording method have been improved. However, in recent years, the following advanced characteristics have been required for recording media for ink jet recording.
-When an image is formed, the print dot density is high and the color tone is bright and vivid.
-The ink is absorbed quickly and the amount of ink absorbed is large so that the ink does not run out or bleed even when the printed dots overlap.
・ Diffusion of printed dots in the horizontal direction should not be larger than necessary.
• The printed dot shape is close to a perfect circle, and the periphery is smooth and not blurred.
-The whiteness of the recording medium is high and the glossiness is high.

  The ink jet recording system has been expanded from the conventional home print to the commercial field, and its application is also expanded from photography to printing. In order to meet the demand for high gloss in photographic applications, the surface of a recording medium for inkjet recording is highly smoothed. In order to obtain such a highly smooth surface, silica having an extremely small particle diameter is used as the porous pigment used in the ink receiving layer. However, since such ultrafine pigments have a large surface energy and often form aggregates in the coating liquid used to form the ink receiving layer, strong stirring is required to disperse them in the solvent. Necessary. On the other hand, bubbles adhering to silica in the coating solution have a strong adhesive force and it is difficult to remove. If a strong agitation is applied to the coating solution for the purpose of obtaining excellent dispersibility, the bubbles in the coating solution are reversed. It becomes easy to mix.

  When bubbles are present in the coating solution as described above, the ink receiving layer formed by coating and drying the coating solution on the support may crack, streak, tail, Such coating defects occur. If the solid content in the coating liquid is low, the foam can be separated or removed by standing or by a simple method, but if the solid content concentration in the coating liquid is increased to a practical range, the foam is removed. It becomes difficult to do. Furthermore, when a binder resin such as a polyvinyl alcohol resin is added to the coating liquid, the coating liquid becomes highly viscous, which makes it difficult to stir and degas the coating liquid.

So far, there have been proposals for the following methods for uniformly dispersing the pigment in the coating liquid and for defoaming the coating liquid.
(1) Patent Document 1 discloses a coating liquid in which an aggregate pigment is pulverized and dispersed in a cationic resin-containing liquid, and the average particle diameter of the aggregate pigment is 500 nm or less.
In the method disclosed in Patent Document 2, first, a cationic resin is added to a coating liquid in which fine pigments having an average particle size of 300 nm or less are dispersed to increase the viscosity and agglomerate. Thereafter, a recording layer is provided on the support by applying a coating liquid containing a pigment pulverized and dispersed so that the average agglomerated particle size is 1 μm or less, and finally an inkjet recording body is manufactured. Yes.

  (2) Patent Document 3 discloses an ink jet recording material in which a support is provided with a layer obtained by applying and drying a coating liquid containing fine particles having an average particle diameter of 10 nm to 300 nm pulverized using a pressure homogenizer. ing.

  Patent Document 4 discloses an ink jet recording paper in which a color material receiving layer is provided on a support. This color material receiving layer is manufactured by the following steps. First, inorganic fine particles and a cationic resin are mixed with water to form a slurry. Next, using a ceramic sand grinder filled with ceramic beads, this slurry is finely dispersed until the average particle size becomes 30 to 200 nm. Thereafter, a coating material obtained by adding a water-soluble polymer to this slurry is applied onto a support and dried to form a color material receiving layer, and finally an inkjet recording paper is manufactured.

  Patent Document 5 discloses a method for producing an inkjet recording material in which at least two coating layers are formed by coating a coating liquid containing inorganic fine particles on a support. In this production method, the inorganic fine particle-containing coating liquid is dispersed using a sand mill type disperser. Further, the dispersion energy (peripheral speed (m / s) 2 x residence time (min)) at the time of dispersion is set to be different for each coating layer.

  (3) Patent Document 6 discloses an ink jet recording material in which a coating composition containing an aqueous dispersion of inorganic fine particles is coated on a support. This ink jet recording material is composed of at least two steps of a primary dispersion step of kneading inorganic fine particles and water to obtain a coarse dispersion and a secondary dispersion step of finely dispersing the coarse dispersion to adjust the particle size distribution. Is manufacturing.

  In Patent Document 7, a primary dispersion step for obtaining a coarse dispersion of amorphous silica, a secondary dispersion step for finely dispersing the coarse dispersion to adjust the particle size distribution, and between the primary dispersion step and the secondary dispersion step, And / or the manufacturing method of the amorphous silica containing coating liquid which has the process of performing filtration in a secondary dispersion | distribution process is disclosed.

  (4) Patent Document 8 discloses two steps of a primary dispersion step for obtaining a coarse dispersion of vapor-phase process silica and a secondary dispersion step for finely dispersing the coarse dispersion obtained in the primary dispersion step to adjust the particle size distribution. A method for preparing a coating liquid for an ink jet recording medium is disclosed. In this primary dispersion step, a flow-type suction dispersion stirrer that continuously supplies and disperses gas phase method silica to a mixture of a dispersion aid and an aqueous dispersion medium, and a batch-type dispersion tank equipped with a rotary blade stirrer are used in combination. Has been. Moreover, in this primary dispersion | distribution process, the dispersion process is performed under the reduced pressure of 0.02 MPa or more and 0.07 MPa or less.

Patent Document 9 discloses an inkjet recording medium coating liquid, wherein an inkjet coating liquid is fed to a mixing kettle in which a defoaming apparatus is installed or a mixing kettle in which the defoaming apparatus is operating. The preparation method of is disclosed.
Patent Document 10 discloses a pigment characterized by holding a mixture of at least a pigment, a liquid medium, and a dispersant in a reduced pressure environment, then holding the mixture in a pressure environment equal to or higher than normal pressure, and thereafter performing a dispersion treatment. A method for producing a dispersion is disclosed.
Patent Document 11 discloses a method for producing a pigment dispersion in which a high-structure pigment powder is subjected to surface modification, followed by water dispersion treatment and further defoaming treatment.
JP-A-10-181190 JP-A-10-181191 JP-A-10-272833 JP 2003-094796 A JP 2004-330731 A JP 2002-178626 A Japanese Patent Application Laid-Open No. 2004-299943 JP 2004-267991 A JP 2005-001299 A JP 2002-069325 A JP 2006-008865 A

  The inventor has examined various dispersion methods and defoaming methods that have been proposed in advance as listed above. As a result, it was found that the following problems existed in any form.

  (1) Patent Documents 1 and 2 disclose a method in which a cationic resin is added as a dispersion aid, and silica as a pigment is pulverized together with the cationic resin. This pulverization process can make the pigment finer, but a strong force is required for pulverization, and bubbles may be mixed in the coating liquid. Moreover, since the viscosity of the silica-containing coating solution is reduced when the cationic resin is added, the binder resin is added to the coating solution, which may increase the viscosity of the silica-containing coating solution. For this reason, after addition of binder resin, it became difficult to remove the foam in a silica containing coating liquid. As described above, it has been found that it is difficult to obtain a silica-containing coating solution free from bubbles by the conventional method. Further, when silica and a cationic resin are used, the silica surface is wrapped with the cationic resin, which may adversely affect the image characteristics of the recording medium formed using the silica-containing coating liquid in ink jet printing.

  (2) In the method disclosed in Patent Documents 3, 4, and 5 in which inorganic fine particles are dispersed with a pressure homogenizer or a sand grinder, a coating liquid in which inorganic fine particles are finely dispersed is obtained. However, since this method is a high-pressure dispersion or a dispersion method using media, not only the pigment but also the bubbles become fine and stabilized, and may be dispersed in the coating liquid. It was extremely difficult to remove the bubbles that were reduced in size as described above from the coating solution. In addition, when the media is used, there is a possibility that foreign matter is mixed in the coating liquid.

  (3) In the method of dispersing in two dispersion steps of the primary dispersion step and the secondary dispersion step disclosed in Patent Documents 6 and 7, coarse particles of silica are dispersed in the primary dispersion step, and in the secondary dispersion step, This silica is further dispersed to fine particles. Since it is necessary to apply a strong force to the dispersion of silica in each step, bubbles may be mixed in the coating liquid. In particular, in the secondary dispersion step, since a high-pressure homogenizer or a bead mill is used, it is difficult to remove bubbles.

  (4) In the methods disclosed in Patent Documents 8, 9, and 10, the coating liquid is defoamed by placing the silica-containing coating liquid under reduced pressure. However, any of the methods described in the literature requires a dispersion aid such as a cationic resin to disperse silica, and the preparation of a coating solution in which silica without foam is dispersed without using a dispersion aid. Was difficult. In addition, in the configuration of the ink receiving layer described in these documents, if alcohols are added to the coating liquid, the alcohols remain in the ink receiving layer, and the alcohol content in the printed portion is volatilized. There was a problem. Further, each of the above methods merely reduces the pressure at the time of defoaming, and it was difficult to remove bubbles from a high-viscosity coating solution or to remove small bubbles of several μmφ.

  (5) In the methods disclosed in Patent Documents 10 and 11, the pigment dispersion is subjected to defoaming treatment such as reduced pressure, heating, and ultrasonic waves, but fine bubbles adhering to the pigment are completely removed only by these treatments. It was difficult to remove.

  As described above, with the methods described in Patent Documents 1 to 11, it has been difficult to sufficiently degas the pigment dispersion. Furthermore, even if the present inventor is a method other than those described in Patent Documents 1 to 11, in the conventional method in which a dispersion treatment is performed by applying a strong force when the silica fine particles are dispersed, Was found to change and the pore volume decreased. In addition, the ink receiving layer formed using the dispersion-treated coating liquid may have insufficient ink absorption capacity, resulting in ink overflow and bleeding, which may result in poor image quality. I found it.

The main object of the present invention is to solve a new problem based on such new knowledge.
That is, the first object of the present invention is to provide a method for producing a silica coating solution free from bubbles. In particular, it is to remove bubbles in the coating liquid without using a dispersion aid such as a cationic resin that affects printing characteristics. A second object of the present invention is to provide a method for producing a recording medium for ink jet recording having an ink receiving layer in which a crack, which is a coating defect caused by bubbles during coating, does not occur.

  The third object of the present invention is to provide a method for producing a mixed liquid that can improve the efficiency of the dispersion treatment process and provide dispersion stability in the dispersion treatment of the pigment dispersion containing the pigment and at least one of its dispersant and solvent. It is to provide.

The above object is achieved by the present invention described below.
1. In a method for producing a coating liquid for coating on a support to form an ink-receiving layer, a coating containing silica and a solvent is removed by a kneading process that performs both rotation and revolution in a reduced pressure environment. A method for producing a liquid, comprising:
a) kneading and bringing the surface of the silica into contact with the solvent;
b) The step of causing the mixture to flow from the liquid bottom to the liquid level by up-down convection to move the bubbles to the liquid level,
c) expanding the bubbles in the mixture and releasing them from the mixture in a reduced pressure environment;
The manufacturing method of the coating liquid characterized by having.

2. 2. The method for producing a coating liquid according to 1 above, wherein the mixture contains a binder resin.
3. 3. The method for producing a coating liquid according to 1 or 2 above, wherein the kneading treatment for performing both rotation and revolution is such that the rotation axis of rotation and the rotation axis of revolution are not parallel.

4). 4. The method for producing a coating liquid as described in any one of 1 to 3 above, wherein the pressure under the reduced pressure environment is 13.3 KPa or less.
5. 5. The method for producing a coating liquid as described in 4 above, wherein the pressure under the reduced pressure environment is 6.7 KPa or less.
6). 6. An ink-jet recording material, wherein an ink receiving layer is formed by applying and drying a coating liquid obtained by the method for producing a coating liquid according to any one of 1 to 5 above on a support. A method for manufacturing a recording medium.

7). A method for producing a mixed liquid that includes a step of removing bubbles generated when mixing the pigment and at least one of the dispersant and the solvent, and performs both rotation and revolution in a reduced pressure environment,
d) a step of causing a mixture of the pigment and at least one of the dispersant and the solvent to flow from the liquid bottom to the liquid surface by vertical convection to move the bubbles to the liquid surface;
e) expanding the bubbles in the mixture;
A method for producing a mixed liquid under a reduced pressure environment.

8). 8. The method for producing a mixed liquid under a reduced pressure environment as described in 7 above, wherein the rotation and revolution are not parallel to each other.
9. 9. The method for producing a mixed liquid under a reduced pressure environment as described in 8 above, wherein the pressure under the reduced pressure environment is 13.3 KPa or less.
10. 9. The method for producing a mixed liquid under a reduced pressure environment according to 8 above, wherein the pressure under the reduced pressure environment is 6.7 KPa or less.

Typical effects obtained by the present invention described above are as follows.
(1) In the present invention, since the bubbles are removed while kneading a mixture containing silica and a solvent, it is possible to prepare a coating liquid free from bubbles even at high solids concentration and high viscosity.
(2) In the present invention, silica can be dispersed and bubbles can be removed without using a dispersion aid such as a cationic resin. For this reason, the silica coating liquid which does not contain the dispersion aid which has a bad influence on printing characteristics can be created.
(3) In the present invention, a silica coating solution free from bubbles can be produced. For this reason, there is no occurrence of coating defects such as cracks in the ink receiving layer formed using this coating liquid.
(4) In the present invention, it is possible to make a dispersion from which fine bubbles are removed from a pigment, a dispersant, a solvent and the like. For this reason, it is possible to produce a mixed liquid with improved dispersion processing efficiency and good dispersion stability.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
The present inventor has made various studies on coating defects such as cracks in the ink receiving layer with respect to a recording medium for inkjet recording having an ink receiving layer provided on a support. As a result, it was found that bubbles mixed in the coating liquid containing silica fine particles were the cause of coating defects, but in the coating liquid containing silica fine particles, Removal was very difficult. Furthermore, the coating liquid containing silica fine particles and a binder resin has a high viscosity, and a strong dispersion treatment is necessary to obtain good dispersibility of the silica fine particles. As a result, bubbles were mixed during the dispersion treatment.

Therefore, the present inventor has found that a silica-containing coating liquid free of bubbles can be obtained by performing the following series of steps by kneading treatment that simultaneously performs rotation and revolution in a reduced pressure environment.
a) A step of bringing the surface into contact with a solvent while dispersing the silica fine particles in the coating liquid to separate bubbles present in the particles from the particles and releasing them into the solvent.
b) The step of causing the mixture to flow from the liquid bottom to the liquid level by up-down convection to move the bubbles to the liquid level.
c) releasing air bubbles in the mixture from the mixture in a reduced pressure environment;

  Furthermore, an ink receiving layer free from coating defects can be obtained by forming the ink receiving layer by coating and drying the foam-free coating liquid obtained in the above step on the support. By using the above coating solution, it is possible to prevent the occurrence of coating defects on the surface of the ink receiving layer and to obtain good ink absorbability.

That is, the present invention relates to a method for producing a coating liquid for coating on a support to form an ink receiving layer. This coating liquid is obtained by performing the following series of steps by a kneading process in which a mixture containing at least silica and a solvent simultaneously rotates and revolves in a reduced pressure environment.
a) A step of kneading and bringing the surface of the silica into contact with the solvent.
b) The step of causing the mixture to flow from the liquid bottom to the liquid level by up-down convection to move the bubbles to the liquid level.
c) A step of expanding the bubbles in the mixture and releasing them from the mixture in a reduced pressure environment.

Hereinafter, the process in which bubbles are removed from the coating liquid by the above-described process will be described in detail.
1A to 1E are cross-sectional views showing an example of a process in which bubbles are removed from a coating liquid by the production method of the present invention. FIG. 1A shows a state in which a mixture containing silica particles, binder resin particles and a solvent component is filled in a container and placed under reduced pressure. As shown in FIG. 1A, silica particles or silica particles and binder resin particles form secondary particles in the mixture. And the bubble is taken in inside this secondary particle.

  Next, this mixture is subjected to a kneading process including both rotation and revolution in a reduced pressure environment. At this time, as shown in FIG.1 (b), the solvent in a coating liquid osmose | permeates in these secondary particles (silica particle, binder resin particle), and the surface of a silica will be in the state which contacts a solvent. As a result, the foams present in the secondary particles are separated from the silica particles and the binder resin particles and separated into the solvent (step a)).

  Here, the mixture is further subjected to a kneading process consisting of a rotational motion and a revolving motion in a reduced pressure environment. As a result, as shown in FIG. 1C, a solvent flow (upper and lower convection of the mixture) from the container bottom (liquid bottom) to the liquid surface is created in the container, and the bubbles separated from the silica particles and the like are removed from the liquid. Move to the surface (step b)). That is, bubbles are moved to the liquid level by causing the mixture to flow from the liquid bottom (mixture bottom) to the liquid level of the mixture by vertical convection.

  At this time, as shown in FIG. 1 (d), the bubbles that have moved to the liquid surface expand and become larger because of the reduced pressure. The enlarged bubbles are released (removed) to the reduced pressure environment when reaching the liquid surface (step c)). As a result, as shown in FIG. 1 (e), a coating liquid containing uniform silica free of bubbles and a binder resin is obtained.

  Thus, in this invention, the silica containing coating liquid which does not have a foam can be obtained by repeating the series of process of Fig.1 (a) to FIG.1 (e). In addition, it is not necessary to perform a series of processes of this invention in order, for example, it is also possible to advance each process simultaneously. For example, it is also possible to discharge the bubbles from the liquid surface under reduced pressure by kneading silica and a solvent, wetting the silica surface with the solvent and separating the bubbles into the solvent, and performing convection of the mixture.

  FIG. 2 is a cross-sectional view showing the flow of the coating liquid in step b) of the manufacturing method of the coating liquid of the present invention. In this invention, as shown to Fig.2 (a), the bubble in a solvent is moved to the liquid level using the flow of the mixture which goes to the liquid level of a mixture from a container bottom part.

(Function)
Here, although it is presumed about the effect | action by the structure of the said invention, a functional description is given.

1. Step a)
In this step, first, silica particles and binder resin particles are mixed with a solvent and then kneaded. By this kneading, the surface of silica is brought into contact with the solvent (step a)). Here, “kneading” is a process of performing rotation and revolution of the container, as will be described later. “Rotation” of a container refers to a movement of rotating a container containing a coating liquid around the rotation axis of the container. The rotation axis of the container is a line perpendicular to the bottom surface of the container and passing through the center of gravity of the bottom surface. As a specific autorotation method, there can be mentioned a method in which a force is applied from the outside of the container to rotate the entire container around the rotation axis of the container.
The “revolution” of the container is a movement of rotating the container containing the coating liquid around a rotation axis outside the container. As a specific method for the rotation and revolution of the container, the container 4 containing the mixture is placed inside a sealed container so that the rotation axes of the rotation and revolution are not parallel to each other. It can be implemented by doing it simultaneously.

  As shown in FIG. 1A, silica particles or silica particles and binder resin particles form secondary particles in the mixture. Further, the surface of the secondary particles is in contact with the solvent and wetted with the solvent, but there is a portion not in contact with the solvent inside the secondary particles, and bubbles are taken into this portion. When the mixture containing the secondary particles is kneaded in a reduced pressure environment, the secondary particles are gradually destroyed, and the silica particles and the binder resin particle surfaces constituting the secondary particles are all part. Comes into contact with the solvent and gets wet with the solvent. In this process, it is considered that the air inside the secondary particles is separated from the silica particles and the binder resin particles.

  On the other hand, the bubbles in the secondary particles cannot be separated only by kneading at atmospheric pressure or simply placing them in a reduced pressure environment. When kneading is performed at atmospheric pressure, bubbles separated from silica particles and the like become small and cannot be removed from the solvent. Further, even if the mixture is not in a reduced pressure environment, convection does not occur in the mixture unless the kneading process is performed, and thus bubbles cannot be removed efficiently.

  Furthermore, further kneading and re-aggregation of these particles can be prevented by further kneading the silica particles and the binder resin particles with the solvent wet. And as shown in FIG.1 (b), the foam which existed in the secondary particle | grains is isolate | separated in the solvent which comprises a mixture as the state in which the silica particle and the binder resin particle got wet with the solvent progressed.

2. Step b)
Next, by continuously performing a kneading process in which rotation and revolution are performed simultaneously in a reduced pressure environment, vertical convection of the mixture is generated in the container as shown in FIG. This vertical convection consists of an upward flow from the bottom of the container toward the liquid level of the mixture at the center of the container and a downward flow from the liquid level of the mixture toward the bottom of the container near the side of the container. By this up-and-down convection, the solvent present at the bottom of the container is first collected at the center of the container, and the bubbles present in the solvent are also collected at the center of the container. In this state, the bubbles move to the liquid level by the upward flow.

  Here, if there is no flow in the mixture, a part of the foam is reattached to the silica because the mixture containing the silica fine particles has a high viscosity and the foam has a strong force to adhere to the silica. There was a case. However, in the present invention, by creating a solvent flow from the bottom of the container to the liquid surface in the container by the kneading process, it is possible to effectively prevent the foam from reattaching to the silica.

Hereinafter, a process in which the convection of the mixture occurs in the container by the kneading process will be described.
FIG. 3 (b) is a diagram showing an example of a state in which rotation is performed around the rotation axis of the container containing the mixture, and FIG. 3 (a) shows the container containing the mixture with the rotation axis existing outside the container. It is a figure showing an example of the state which performed the revolution exercise | movement as the center.

  As shown in FIG. 3 (a), in the revolving motion, the entire mixture in the container receives a centrifugal force from the rotation axis of revolution toward the outside in the radial direction (the direction of the arrow in FIG. 3 (a)). That is, all the mixtures in the container are subjected to centrifugal force in the same direction. For this reason, the mixture at the bottom of the container stays in a predetermined portion without causing convection movement, and the entire mixture cannot be convected.

  On the other hand, as shown in FIG. 3 (b), the mixture in the container is subjected to centrifugal force in the lateral direction of the container (in the direction of the arrow in FIG. 3 (b)) in the rotational motion. That is, the mixture in the container is subjected to centrifugal force in different directions depending on the location. For this reason, the mixture in the vicinity of the side surface of the container stays without causing convection motion, and the entire mixture cannot be convected.

  As described above, in the rotation and revolution alone, a staying portion of the mixture is generated in a predetermined portion in the container, and effective convection of the mixture cannot be generated in the container. Therefore, in the present invention, a force in a direction that causes vertical convection can be exerted on the entire mixture in the container by combining the rotation motion and the revolution motion. As a result, the mixture in the container can be evenly convected and no stagnation of the mixture occurs in the container.

  That is, in the revolving motion, all the mixtures are subjected to centrifugal force in the same direction. On the other hand, in the rotation motion, the mixture receives centrifugal force in different directions depending on the location in the container. Further, the direction of the centrifugal force based on the rotation motion and the revolution motion changes with time with rotation. In addition, for example, by making the rotation axis of rotation and the rotation axis of revolution not parallel, the direction of centrifugal force generated in each part of the mixture in the container by rotation and revolution is made different, and this direction is changed over time. Can be changed. Therefore, by combining this rotational motion and revolution motion, it is possible to generate vertical convection that causes a flow in which the mixture in the central portion of the container is raised and the mixture in the side portion of the container is lowered in the container.

  The direction and speed of the convection flow are the size of the container (size and height of the cross section of the container), rotation speed, rotation speed, ratio of rotation speed to rotation speed, rotation axis (rotation axis of rotation) and The angle can be adjusted as appropriate by controlling the angle formed by the revolution axis (revolution axis), the volume, viscosity, surface tension, etc. of the mixture. By adjusting the conditions of the rotational motion and the revolving motion in this way, the magnitude and direction of the force obtained by synthesizing the centrifugal force due to the rotational motion and the revolving motion are different in each part in the container. Therefore, by the combined force, the mixture in the container generates a flow rising from the bottom of the container to the liquid level and a flow falling to the side of the container at the center of the container, and the mixture in the container can be convected.

  In the present invention, when the rotation motion and the revolution motion are used in combination by the kneading process, it is preferable that the rotation axis of the rotation motion and the rotation axis of the revolution motion are not parallel. By making the rotational axes of both motions not parallel, the directions of the forces applied to the mixture with both motions can be made different from each other, and vertical convection from the bottom of the container to the liquid surface can be effectively generated. . In order to effectively generate vertical convection, it is preferable that the rotation axis of rotation with respect to the rotation axis of revolution be 45 degrees. At this time, it is preferable that the rotation axis of revolution is in the vertical direction.

  As described above, in the present invention, agitation in the direction from the bottom of the container toward the liquid level of the mixture occurs in the mixture as shown in FIG. On the other hand, a solvent flow that does not reach the liquid surface from the center of the container as shown in FIG. Therefore, in the present invention, the flow in the depth direction (height direction) and the flow in the peripheral direction (radial direction) of the container can be adjusted by changing the ratio of the rotational speed of the rotation motion and the revolution motion. That is, when the rotation speed is small with respect to the revolution speed, a large solvent flow occurs in the depth direction as shown in FIG. 2A, and when the rotation speed increases, the container as shown in FIG. 2B. The flow in the depth direction becomes smaller and the flow in the depth direction becomes smaller. For this reason, the preferable range of (revolving speed) / (revolving speed), which is the ratio between the revolution speed and the revolution speed, is 1/3 or less. When (rotational speed) / (revolving speed) is larger than 1/3, the foam does not reach the liquid level of the mixture, or the force toward the periphery becomes strong and the foam becomes small and cannot be separated from the solvent. There is a case.

  In the present invention, the number of revolutions and rotations during kneading varies depending on the scale of the apparatus and the container. For example, when a commercially available 300-500 ml cylindrical container is used, the revolution speed is preferably in the range of 1000 revolutions / minute or more. If it is less than 1000 revolutions / minute, the force which creates the flow of the depth direction in a container may be insufficient, and a bubble may not be able to move to the liquid level of a mixture. The revolution speed is preferably 2000 revolutions / minute or less. By setting it to 2000 rpm or less, the temperature rise of the mixture due to kneading can be suppressed.

  In the present invention, a kneading process can be performed in a reduced pressure environment by preparing a sealed container in which the container 4 containing the mixture is installed and depressurizing the sealed container. In addition, the reduced pressure environment in which the kneading treatment of the present invention is performed is preferably 13.3 KPa or less. The release of bubbles and the evaporation of solvent components occur simultaneously from the solvent, but at 13.3 KPa or less, the bubbles can be effectively expanded and released while suppressing the evaporation of the solvent. Thus, the kneading treatment is preferably performed after the silica particles, the binder resin particles, and the solvent, which are components of the coating liquid, are placed in a reduced pressure environment. When kneading is carried out in such a reduced pressure environment, bubbles separated from silica particles or the like may be crushed and become small and cannot be removed from the solvent.

  The pressure in the container under a reduced pressure environment is more preferably 6.7 KPa or less. By setting the pressure within this range, the temperature rise of the solvent and coating liquid due to kneading can be suppressed. Further, the pressure in the container under a reduced pressure environment is preferably 2.3 KPa or more. When the pressure is less than 2.3 KPa, the solvent may suddenly boil as the temperature of the kneading process is increased.

In the present invention, for example, the following two methods can be used as a kneading method when the mixture contains a binder resin.
(1) A method in which silica, binder resin, and solvent are put in a container and kneaded in a reduced pressure environment.
(2) A method in which silica and a solvent are placed in a container and kneaded in a reduced pressure environment to preliminarily disperse the silica, and a binder resin is further added and kneaded again in a reduced pressure environment.
Among these, a more preferable kneading method is the latter method (2). By predispersing silica and a solvent, it is possible to minimize the thickening of the liquid when the binder resin is added.

  In the present invention, as a more preferable method, vibration can be applied to a mixture of silica and a solvent. By applying vibration to the mixture, the separation of bubbles from the silica is improved and the bubbles can be removed in a short time. As a method for applying vibration, a known method can be used as long as it does not disturb the vertical convection due to rotation and revolution. For example, mechanical vibration such as ultrasonic waves can be used. It is also possible to adjust the period of rotation and revolution by the method of the present invention to give a natural vibration to give the mixture a vibration.

3. Step c)
Next, the bubbles are raised to the liquid level of the mixture by vertical convection. At this time, at the liquid level, the foam is expanded because the pressure of the foam becomes small. In this way, the enlarged bubbles are released under a reduced pressure environment and removed.

In the present invention, the above process may be applied to a method for producing a mixed liquid in which bubbles generated when the pigment is mixed with at least one of the dispersant and the solvent undergo both rotation and revolution in a reduced pressure environment. it can. As a method for producing a mixed liquid containing a pigment and at least one of a dispersant and a solvent, for example, the following two methods can be used.
(1) A method in which a pigment and at least one of a dispersant and a solvent are placed in a container and kneaded in a reduced pressure environment.
(2) A method in which a dispersion in which at least one of a pigment, a dispersant, and a solvent is predispersed is placed in a container and kneaded in a reduced pressure environment.
Hereinafter, each constituent material used when manufacturing the recording medium for inkjet recording in the present invention will be described in more detail. In addition, the effect | action and basic principle of invention in the manufacturing method of the liquid mixture of this invention are the same as the above-mentioned (action | action) and the effect | action and basic principle of FIGS. In this case, in the above (action) and FIGS. 1 to 3, the “solvent” can be replaced with “at least one of a solvent and a dispersant” to consider the action and basic principle of the invention.

(Constituent material of support)
As a support for a recording medium for inkjet recording, paper such as appropriately sized paper, non-size paper, resin-coated paper using polyethylene, etc., sheet-like substances such as thermoplastic films, and fabrics are used. Yes, but there are no particular restrictions. In the case of a thermoplastic film, a transparent film such as polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene, and polycarbonate, or a sheet made opaque by filling with inorganic particles or fine foaming can also be used.

  It is preferable to use paper formed from a fibrous material for the support of the recording medium for inkjet recording. Cellulose pulp can be used as the fibrous material. Specific examples include, for example, chemical pulps such as sulfite pulp (SP), alkali pulp (AP), and kraft pulp (KP) obtained from hardwood and softwood, semi-chemical pulp, and semi-mechanical pulp. In addition, mechanical pulp, etc., and waste paper pulp which is a deinked secondary fiber can be used. Further, the pulp can be used without distinction between unbleached pulp and bleached pulp, and beating and unbeaten. As described above, beating or cellulose pulp is a non-wood pulp fiber such as grass, leaf, bast, seed hair, such as straw, bamboo, hemp, bagasse, esparto, kenaf, straw, three bases, Pulp such as cotton linter can also be used. These materials can be used alone or in combination.

  In the present invention, in addition to the cellulose pulp, at least one selected from bulky cellulose fibers, mercerized cellulose, fluffed cellulose, and mechanical pulp such as thermomechanical pulp can be added and used. By adding these pulps, it is possible to improve the ink absorption speed and the ink absorption amount of the resulting recording medium for ink jet recording.

In the present invention, a filler can be added to the fibrous material constituting the support as necessary. For example, as the filler, white pigments such as light calcium carbonate and heavy calcium carbonate, silica-based materials such as silica or silicate, and silicate compounds can be used. In the present invention, in order to increase the ink absorption speed of the recording medium for ink jet recording, it is possible to adopt a structure without a filler. Various shapes such as a spherical shape, a lump shape, and a needle shape can be used for the filler. In order to reduce the interaction with the fiber, a porous filler can also be used. A preferred filler has a specific surface area of 50 m ² / g or more. The amount of filler added is preferably 5% by mass or more and 20% by mass or less of the entire support in terms of ash. If it is less than 5% by mass, the effect of suppressing the deformation of the fiber is small, and if it exceeds 20% by mass, the amount of paper dust generated may increase. In addition, content of the porous filler was shown in ash conversion. Ash content can be measured according to JIS P8128.

(Manufacturing method of support)
In the present invention, the support is produced by paper making a mixture of the above support material and, if necessary, a porous filler. The basis weight of the support is not particularly limited as long as the basis weight is small and the substrate is not extremely thin. For example, if the basis weight is in the range of 40 g / m ² or more and 300 g / m ² or less, it is preferable in terms of transportability when printing with a printer or the like. A more preferable range is that having a basis weight of 45 g / m ² or more and 200 g / m ² or less. Within this range, the opacity can be increased without increasing the bending strength of the paper. Furthermore, sticking does not easily occur when a large number of print samples are stacked.

  As a method for producing a support for a recording medium for ink jet recording according to the present invention, a generally used paper production method can be applied. Further, a long paper machine, a round paper machine, a circular cylinder, a twin wire, or the like conventionally used as a paper machine can be selected and used. In the size press step, it is also possible to apply a porous material. A general coating method can be selected and used for this coating. For example, a coating technique using a gate roll coater, size press, bar coater, blade coater, air knife coater, roll coater, brush coater, curtain coater, gravure coater, spray device or the like can be used.

In the present invention, the formed support can be subjected to calendaring, thermal calendaring or supercalendering to smooth the surface. The density of the support after the smoothing treatment is preferably 0.5 g / cm ³ or more and 0.7 g / cm ³ or less. If the density is less than 0.5 g / cm ³ , cracks may occur when forming the ink receiving layer, and if the density exceeds 0.7 g / cm ³ , cockling may occur in the ink receiving layer when printed. There is sex. In addition, the density of a support body can be measured by the method described in Unexamined-Japanese-Patent No. 2004-66492.

(Constituent material of ink receiving layer)
The main material constituting the ink receiving layer of the recording medium for ink jet recording of the present invention is silica (porous silica) or silica (porous silica) and a binder resin. Preferably, the main materials are silica (porous silica) and a binder resin.

  When forming this ink receiving layer, (1) a coating liquid containing porous silica and a solvent, or (2) a coating liquid containing porous silica, a binder resin and a solvent is used. As the solvent, it is preferable to use water, alcohol or the like.

As the porous silica, both gas phase method silica and wet silica can be preferably used. The specific surface area of the porous silica is preferably 100 m ² / g or more because the ink absorptivity and color density can be increased. Within this range, the surface smoothness can be easily obtained when the ink receiving layer is formed, and cracks are hardly generated. The porous silica preferably has pores in the radius range of 10-20 nm. By having such pores, ink absorptivity and dot shape can be improved.

The pore volume of the ink receiving layer having a radius of 20 nm or less is preferably 0.3 ml / m ² or more. Within this range, the surface gloss can be increased without reducing the ink absorption rate.

  When a binder resin is used for the ink receiving layer, the binder resin can be freely selected from the following water-soluble polymers. For example, polyvinyl alcohol or modified products thereof (cationic modification, anion modification, silanol modification), starch or modified products thereof (oxidation, etherification), gelatin or modified products thereof, casein or modified products thereof, carboxymethylcellulose, gum arabic, hydroxy Cellulose derivatives such as ethyl cellulose and hydroxypropylmethyl cellulose, conjugated diene copolymer latex such as SBR latex, NBR latex, methyl methacrylate-butadiene copolymer, vinyl group such as functional group-modified polymer latex, ethylene vinyl acetate copolymer It is preferable to use a copolymer latex, polyvinylpyrrolidone, maleic anhydride or a copolymer thereof, an acrylate ester copolymer, or the like. These binder resins can be used alone or in combination of two or more.

  The mixing ratio of the porous silica and the binder resin is preferably 5 to 70 parts by mass of the binder resin with respect to 100 parts by mass of the porous silica. When the amount of the binder resin is less than the above range, the ink receiving layer has insufficient mechanical strength, and there is a possibility that cracks or powder fall may occur. Further, when the amount of the binder resin is larger than the above range, the ink absorbability of the ink receiving layer may be lowered.

  In the present invention, in addition to the constituent materials of the ink receiving layer and the surface layer, a dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, a water resistant agent, Antifoaming agents, mold release agents, foaming agents, penetrating agents, coloring dyes, fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, etc. can be added as necessary. .

(Method for forming ink receiving layer)
An ink receiving layer is formed on the support using the coating liquid produced by the production method of the present invention. This coating solution contains at least silica (porous silica) and a solvent. As this coating method, a method of applying and drying a coating solution on a support with a coating machine can be used.

As a coating method, generally used coating techniques such as a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a bar coater, a gravure coater, and a spray device can be employed. If the application amount of the coating liquid is 5 g / m ² or more and 30 g / m ² or less in terms of dry solid content, ink absorption and suppression of cockling can be satisfied. A more preferable range of the coating amount is 7 g / m ² or more and 20 g / m ² or less. Within this range, the surface strength of the ink receiving layer can be increased. If necessary, after the ink receiving layer is formed, the surface smoothness of the ink receiving layer can be improved by using a calender roll or the like.

  Hereinafter, in the method for producing a mixed liquid of the present invention, each constituent material used when producing the mixed liquid will be described in more detail. In the production method of the present invention, this mixed liquid can be produced, for example, as an ink for inkjet recording.

(Pigment)
The pigment used in the pigment dispersion of the present invention and the method for producing the dispersion (mixed liquid) is not particularly limited, but is exemplified as follows. Examples of the black color include carbon blacks such as furnace black, lamp black, acetylene black and channel black, metals such as copper, iron and titanium oxide, and organic pigments such as altonitroaniline black.

  Further, for colors, Pigment Yellow 138, Pigment Red 122, Pigment Blue 15: 3, Toluidine Red, Permanent Carmine FB, Fast Aero AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmine 6B, Phthalocyanine Blue, Quinacridone Red, Dioxane Violet, Victoria Pure Blue, Alkaline Blue Toner, Furnace Yellow 10G, Disazo Yellow AAMX, Disazo Yellow AAOT, Disazo Yellow AAOA, Yellow Iron Oxide, Disazo Yellow HR, Orthonitriloaniline Orange, Dinitroaniline Orange, Vulcan Orange, Toluidine Red, Chlorinated Parared, Brillian First Scarlet, Naphthol Red 23, Pirazone Red, Barium 2B, Calcium Red 2B, Strontium Red 2B, Manganese Red 2B, Barium Resome Red, Pigment Scar Red 3B Lake, Lake Bordeaux 10B, Anthocine 3B Lake, Anthosine 5B Lake, Rhodamine 6G Lake, Eosin Lake, Bengala, Fattor Red FGR, Rhodamine B Lake, Methyl Bio Red Lake, Dioxazine Bio Red, Basic Blue 5B Lake, Basic Blue 6G Lake, Fast Sky Blue, Alkaline Blue R Toner, Peacock Blue Lake, Bituminous Blue, Ultraviolet, Reflex Blue 2G, Red Flex Blue R, Brilliant Green Lake, Diamond Green Thioflavin Lake, Phthalocyanine Green G, Green Gold, Phthalocyanine Y, iron oxide powder, rust, zinc white, titanium oxide, calcium carbonate, clay, barium sulfate, alumina, alumina white, aluminum powder, bronze powder, daylight fluorescent pigment, pearl pigment, naphthol carmine FB, naphthol red M Permanent Carmine FB, Fastero G, Disazo Yellow AAA, Dioxane Bio Red, Alkali Blue G toner, and the like, and other processed pigments such as graft carbon whose surface is treated with a resin or the like can be used.

  These pigments can be used singly or in some cases as a mixture of two or more. In addition, as a liquid mixture of this invention, the liquid mixture containing a pigment and at least one of a dispersing agent and a solvent can be manufactured. As the mixed liquid, for example, a mixed liquid containing a pigment and a dispersant, a mixed liquid containing a pigment and a solvent, or a mixed liquid containing a pigment, a dispersant and a solvent can be produced.

(Dispersant)
In the present invention, the dispersant used by mixing with the pigment is not particularly limited, but the following dispersants can be used as an example. Styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, From at least two monomers (of which at least one is a hydrophilic monomer) selected from fumaric acid, fumaric acid derivatives, vinyl acetate, vinylpyrrolidone, acrylic, amide, acrylamide, and derivatives thereof Or a random copolymer, a graft copolymer, or a salt thereof.

(solvent)
In the present invention, the solvent used by mixing with the pigment is not particularly limited, but the following water-soluble organic solvents can be used as an example. Alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, amides such as dimethylformamide, ketones or ketone alcohols such as acetone, ethers such as tetrahydrofuran, polyalkylene glycols such as polyethylene glycol, ethylene glycol Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms, and lower alkyl ethers of polyhydric alcohols such as glycerin and ethylene glycol methyl ether. As a solvent, 1 type selected from these, or 2 or more types can be selected and used in combination.

  Of these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferably used. Among these, polyhydric alcohols are particularly preferably used because they have a great effect as a lubricant for preventing clogging of nozzles due to evaporation of water in the ink and precipitation of water-soluble dyes.

  When the mixed liquid of the present invention is produced as an ink using a pigment, it is preferable to use a mixture of water and various water-soluble organic solvents as the solvent. In this case, it is preferable to adjust so that the water content in the ink (mixed liquid) is in the range of 20% by mass to 90% by mass.

  A solubilizer can also be added to the ink. Typical solubilizers include nitrogen-containing heterocyclic ketones, and the intended action is to dramatically improve the solubility in solvents such as water-soluble dyes and pigments. As the solubilizer, for example, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used. Furthermore, in order to improve ink characteristics, additives such as a viscosity modifier, a surfactant, a surface tension modifier, a pH adjuster, a specific resistance adjuster and the like can be added.

(Distribution method)
In the present invention, distributed processing can be performed before or after performing both rotation and revolution processing. As a dispersion method in this case, any known disperser that is generally used can be used. Examples of such a disperser include a stirrer such as a homomixer, a ball mill, a roll mill, a sand mill, an attritor, a pearl mill, a dyno mill, a high-pressure homogenizer, an ultrasonic disperser, an agitator mill, a glen mill, and a cobol mill.

(Printing method)
A recording medium for inkjet recording can be produced using the coating liquid produced by the method for producing a coating liquid of the present invention. The mixed liquid can be manufactured as an ink by using the mixed liquid manufacturing method of the present invention. As a method for forming an image on the recording medium for ink jet recording and a method for forming an image using this ink, an ink jet recording method is suitable. As the ink jet recording method, any method may be used as long as the ink can be effectively detached from the fine holes (nozzles) and the ink can be applied to the recording medium for ink jet recording. Among these, the method described in JP-A No. 54-59936 is particularly preferable. In this method, an ink jet recording system in which ink undergoing the action of thermal energy undergoes a sudden volume change, and the ink is ejected from the nozzle by the action force due to this state change can be used particularly effectively.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the contents of the present invention are not limited by the examples. First, the evaluation method of the coating liquid (silica coating liquid) manufactured with the manufacturing method of this invention is as follows.

1. Evaluation of foam in coating solution Using a bar coating method, a silica coating solution is applied to a PET film (Merinex 705 (trade name), thickness 100 μm, manufactured by Teijin DuPont Films) at a dry solid content of 10 g / m ^2. Worked. And the number of the bubbles in the coated silica coating liquid was observed visually.

  If no bubbles are observed in the silica coating solution over the entire A4 size (210 mm × 297 mm), A is B for 5 or less, C for 6-10, D for 21-20, D, 21 E or more were observed when more than one was observed.

2. Defect evaluation of coating layer (ink receiving layer) Using a bar coating method, 10 g / m ² , 20 g in terms of dry solid content on a PET film (Merinex 705 (trade name), thickness 100 μm, manufactured by Teijin DuPont Films) The silica coating solution was applied so as to be / m ² . The PET film coated with the silica coating solution was placed in a dry oven (manufactured by Yamato Kagaku Co., Ltd.) and dried by heating at 100 ° C. for 5 minutes to form a coating layer (ink receiving layer). The number of coating defects (cracks) in the coating layer was visually observed. Here, the crack determined to be a coating defect is a crack having a length of about 1 mm generated in the coating layer. In addition to the straight crack, this crack includes a crack spreading radially from the center like a bird's foot.

For A4 size (210 mm × 297 mm) over the entire surface of the coating layer was coated with ^{10g / m 2, 20g / m} 2 on a dry solid basis, unless the coating defect (crack) is observed in the coating layer A, B when the total number of coating defects is 5 or less, C when 6-10, D when 11-20, and E when 21 or more are observed.

3. Ink absorbability 10 g of silica coating liquid on dry solid content conversion on PPC paper (double-sided thick paper for CLC (trade name), basis weight 104.7 g / m ² , manufactured by Canon Inc.) using the bar coating method. / M ^{2 was} applied. Thereafter, the coating layer (ink-receiving layer) was formed by heating and drying in a dry oven (manufactured by Yamato Scientific Co., Ltd.) at 100 ° C. for 5 minutes.

Next, printing was performed on the coating layer using an inkjet printer iP4200 (trade name, manufactured by Canon Inc.) as a recording device. Printing was performed in single color and multiple colors, and the overflow immediately after printing of the single-color solid print portion and the multi-color solid print portion was visually observed.
If overflow is not observed in the two-color solid printing part A
B if no overflow is observed in the 1-color solid print section
If there is overflow even with one color solid, C
It was.

4). Dispersion time After the dispersion treatment was performed using the bead mill described in Examples 9 to 11 and Comparative Examples 5 to 7, the dispersion was taken out every hour. Next, the average particle size (D50) of the dispersion was measured using a particle size distribution meter (Microtrac UPA150 (trade name), manufactured by Nikkiso Co., Ltd.). And the time until an average particle diameter became 100 nm or less was calculated | required.

5. Storage stability The dispersion was sealed in a Teflon (registered trademark) container and stored at 5 ° C. and 60 ° C. for 2 months, and the presence or absence of sediment was visually evaluated. The evaluation was performed every week, and the period until the sediment was generated was determined.

<Example 1>
200 ml of the following material composition A was weighed and placed in a container (dedicated container for VMX-N360, manufactured by EME, capacity 400 ml, cylindrical shape, inner diameter Φ83 mm, depth 109 mm). Thereafter, both rotation and revolution are performed under a reduced pressure environment using a vacuum stirring device (VMX-N360 (trade name), manufactured by EME, the angle formed by the rotation axis and the revolution axis is 45 °) under the following processing condition 1. A kneading process was performed to obtain a coating liquid. Evaluation of bubbles in the coating liquid, defects in the coating layer, and ink absorptivity was performed by the above methods. The results are shown in Table 1.

<Material composition A>
Silica fine particles Aerosil 50 (trade name), manufactured by Nippon Aerosil Co., Ltd. 25 parts by mass Binder resin Polyvinyl alcohol (PVA117 (trade name), manufactured by Kuraray Co., Ltd.) 10% by mass aqueous solution 50 parts by mass Solvent ion-exchanged water 75 parts by mass

<Processing condition 1>
Decompression degree: 13.3 KPa
Revolution rotation speed: 1800 rotations / minute Autorotation rotation speed: 600 rotations / minute Processing time: 5 minutes.

<Example 2>
A coating solution was obtained in the same manner as in Example 1 except that the degree of vacuum was 6.7 KPa under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 3>
A coating solution was obtained in the same manner as in Example 1 except that the rotation speed was changed to 500 rpm under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 4>
A coating solution was obtained in the same manner as in Example 1 except that the revolution speed was 1200 rpm and the rotational speed was 400 rpm under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 5>
A coating solution was obtained in the same manner as in Example 1 except that the silica fine particles were changed to wet silica (BS312AM (trade name), manufactured by Degussa) in the material composition A of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 6>
Only silica fine particles of the material composition A of Example 1 and ion-exchanged water (solvent) were put in a container and kneaded by the same method as in Example 1. Next, a polyvinyl alcohol aqueous solution was added to a solution containing silica fine particles and ion-exchanged water, and kneading treatment was performed in the same manner as in Example 1 to obtain a coating solution. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 7>
A coating solution was obtained in the same manner as in Example 1 except that the rotational speed was set to 700 rpm under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Example 8>
A coating solution was obtained in the same manner as in Example 1 except that the revolution speed was 900 rpm and the rotational speed was 300 rpm under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.
In Examples 1 to 8 above, vertical convection of the mixture was generated, and it was visually observed that bubbles in the mixture were flowing from the liquid bottom to the liquid level by vertical convection.

<Comparative Example 1>
A coating solution was obtained in the same manner as in Example 1 except that the rotation speed was set to 900 rotations / minute (rotation rotation speed / revolution rotation speed = 1/2) under the processing conditions of Example 1. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.

<Comparative example 2>
Using the same material composition A as in Example 1, a coating liquid was obtained by performing the treatment under the following treatment condition 2 using a stirrer (KK-100 (trade name), manufactured by Kurabo Industries). Next, bubbles in the coating liquid, coating layer defects, and ink absorbency were evaluated in the same manner as in Example 1. The results are shown in Table 1.
<Processing condition 2>
Decompression degree: Atmospheric pressure revolution speed: 9 (set value)
Rotational speed: 1 (set value)
Processing time: 5 minutes.

<Comparative Example 3>
Using the same material composition A as in Example 1, dispersion treatment was performed under the following treatment condition 3 using a homogenizer device (HF-93, trade name, manufactured by SMT Co., Ltd.). Next, the dispersion-treated coating solution was placed in a vacuum oven (manufactured by Yamato Kagaku Co., Ltd.) and allowed to stand for 5 minutes under a reduced pressure of 13.3 KPa to obtain a coating solution. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.
<Processing condition 3>
Decompression degree: Atmospheric pressure rotation speed: 10,000 rotations / minute Processing time: 20 minutes.

<Comparative Example 4>
Using the same material composition A as in Example 1, it was put in a vacuum emulsification apparatus (TK ADD Homomixer, trade name, manufactured by Primix Co., Ltd.) and subjected to dispersion treatment under treatment condition 4 to obtain a coating solution. In the same manner as in Example 1, the bubbles in the coating liquid, the defects in the coating layer, and the ink absorptivity were evaluated. The results are shown in Table 1.
<Processing condition 4>
Decompression degree: 13.3 KPa
Rotation speed: 10000 revolutions / minute Processing time: 20 minutes

As shown in Examples 1 to 8 of Table 1, in the coating liquid produced by the production method of the present invention, the foam in the coating liquid is small as “A” or “B”, and defects in the coating layer are also “A”. "Or" B ". Further, the ink absorptivity was all “A” and good. On the other hand, in the method shown in the following comparative example, good results were not obtained in bubbles / defects in the coating liquid and ink absorbability.
As shown in Comparative Example 1, when there is no vertical convection from the liquid bottom to the liquid level in the kneading process in a vacuum environment.
-As shown in Comparative Example 2, the kneading process under atmospheric pressure.
-As shown in Comparative Example 3, the kneading process by simple high-speed rotation.
-As shown in Comparative Example 4, a kneading process by simple high-speed rotation in a vacuum environment.

<Example 9>
200 ml of the following material composition B was weighed, and a pigment dispersion was obtained using the same container, vacuum stirrer, and conditions as in Example 1. This pigment dispersion was dispersed for 8 hours under processing conditions 5 using a bead mill (Star Mill LMZ-2 (trade name), manufactured by Ashizawa) to obtain a pigment dispersion. The above pigment dispersion was evaluated by the above method. The results are shown in Table 2.

<Material composition B>
Pigment C.I. I. Pigment Blue 15: 3 (LIONOL BLUE FG-7351 (trade name), manufactured by Toyo Ink Co., Ltd.) 20 parts by mass Dispersant Styrene acrylic resin (weight average molecular weight 5000, acid value 250 mg KOH / g) 10 parts by mass solvent Ion-exchanged water 70 parts by mass <Processing condition 5>
・ Bead zirconia bead diameter 0.5mm
・ Bead filling rate 85vol% in the mill body
・ Circulating flow rate 3L / min, peripheral speed 8m / min.

<Example 10>
The pigment of material composition C and diethylene glycol (solvent) were weighed, and bubbles were removed using the same apparatus and method as in Example 9. Thereafter, the remaining components were added and bubbles were removed using the same apparatus and method to prepare a pigment dispersion. Next, a bead mill treatment was performed in the same manner as in Example 9 to obtain a pigment dispersion. Evaluation was performed by the method described above. The results are shown in Table 2.
<Material composition C>
Pigment C.I. I. Pigment Blue 15: 3 20 parts by mass / solvent Diethylene glycol 20 parts by mass / dispersant Styrene acrylic resin (weight average molecular weight 5000, acid value 250 mgKOH / g) 10 parts by mass / solvent ion-exchanged water 50 parts by mass.

<Example 11>
Using the same material composition B as in Example 9, pre-dispersion was performed under the treatment condition 6 using a homomixer (TK Robotics, trade name, manufactured by Primics). Next, after air bubbles were removed by the same apparatus and method as in Example 9, bead mill dispersion was performed in the same manner as in Example 9 to obtain a pigment dispersion. Evaluation was performed by the method described above. The results are shown in Table 2.
<Processing condition 6>
・ Rotation speed 5000rpm
・ Stirring section Disper type ・ Stirring time 30 minutes.
In Examples 9 to 11, vertical convection of the mixture occurred, and it was visually observed that bubbles in the mixture were flowing from the liquid bottom to the liquid surface by vertical convection.

<Comparative Example 5>
The material of material composition B was subjected to the same bead mill treatment as in Example 9 without performing the bubble removal step, to obtain a pigment dispersion. Evaluation was performed by the method described above. The results are shown in Table 2.

<Comparative Example 6>
The pigment of material composition C and diethylene glycol were weighed, and the same bead mill treatment as in Example 10 was performed instead of the bubble removal step in Example 10. Thereafter, the remaining components were added and a bead mill treatment was performed in the same manner as in Example 10 to obtain a pigment dispersion. Evaluation was performed by the method described above. The results are shown in Table 2.

<Comparative Example 7>
Preliminary dispersion was performed in the same manner as in Example 11 using the same material composition B as in Example 9. Next, without performing the bubble removal step, bead mill dispersion was performed in the same manner as in Example 9 to obtain a pigment dispersion. Evaluation was performed by the method described above. The results are shown in Table 2.

  From the result of Table 2, in Examples 9-11 which performed the bubble removal process of the manufacturing method of the liquid mixture of this invention, dispersion | distribution time is 2 hours and storage stability is 2 months or more, The efficiency of dispersion | distribution processing It can be seen that the improvement and the dispersion stability can be improved. On the other hand, in Comparative Examples 5 to 7 in which the bubble removal step was not performed, it was found that the dispersion time was 8 hours and the storage stability was 2 weeks, and the dispersion treatment efficiency and dispersion stability were not sufficient. .

It is a figure showing the process in which foam is removed from the mixture in the manufacturing method of this invention. It is a figure showing the process in which foam is removed from the mixture in the manufacturing method of this invention. It is a figure showing the process in which foam is removed from the mixture in the manufacturing method of this invention. It is a figure showing the process in which foam is removed from the mixture in the manufacturing method of this invention. It is a figure showing the process in which foam is removed from the mixture in the manufacturing method of this invention. It is a figure showing the flow of the mixture in a container in the manufacturing method of this invention. It is a figure showing the flow of the mixture in a container. It is a figure showing the force concerning the mixture in a container by revolution motion. It is a figure showing the force concerning the mixture in a container by autorotation.

Explanation of symbols

1: Silica 2: Bubble 3: Solvent 4: Container 5: Coating liquid 6: Flow of coating liquid 7: Rotating shaft 8: Revolving shaft 9: Revolving motion 10: Rotating motion 11: Direction of force

Claims (10)

In a method for producing a coating liquid for coating on a support to form an ink-receiving layer, a coating containing silica and a solvent is removed by a kneading process that performs both rotation and revolution in a reduced pressure environment. A method for producing a liquid, comprising:
a) kneading and bringing the surface of the silica into contact with the solvent;
b) The step of causing the mixture to flow from the liquid bottom to the liquid level by up-down convection to move the bubbles to the liquid level,
c) expanding the bubbles in the mixture and releasing them from the mixture in a reduced pressure environment;
The manufacturing method of the coating liquid characterized by having.   The method for producing a coating liquid according to claim 1, wherein the mixture contains a binder resin.   The method for producing a coating liquid according to claim 1 or 2, wherein in the kneading treatment for performing both rotation and revolution, the rotation axis of rotation and the rotation axis of revolution are not parallel.   The method for producing a coating liquid according to any one of claims 1 to 3, wherein the pressure under the reduced pressure environment is 13.3 KPa or less.   The manufacturing method of the coating liquid according to claim 4, wherein the pressure under the reduced pressure environment is 6.7 KPa or less.   An ink receiving layer is formed by applying and drying a coating liquid obtained by the method for producing a coating liquid according to any one of claims 1 to 5 on a support, and forming an ink receiving layer. A method for manufacturing a recording medium. A method for producing a mixed liquid that includes a step of removing bubbles generated when mixing the pigment and at least one of the dispersant and the solvent, and performs both rotation and revolution in a reduced pressure environment,
d) a step of causing a mixture of the pigment and at least one of the dispersant and the solvent to flow from the liquid bottom to the liquid surface by vertical convection to move the bubbles to the liquid surface;
e) expanding the bubbles in the mixture;
A method for producing a mixed liquid under a reduced pressure environment.   The method for producing a liquid mixture under reduced pressure according to claim 7, wherein the rotation axis and the rotation axis are not parallel to each other.   The method for producing a mixed liquid under a reduced pressure environment according to claim 8, wherein the pressure under the reduced pressure environment is 13.3 KPa or less.   The method for producing a mixed liquid under a reduced pressure environment according to claim 8, wherein the pressure under the reduced pressure environment is 6.7 KPa or less.

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