JP2005193406A - Recording medium for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium wherein an ink receiving layer having high ink absorption speed, having a large pore capacity and not impairing glossiness is formed and which has excellent characteristics. <P>SOLUTION: In regard to the recording medium wherein the ink receiving layer containing inorganic pigment particles is formed on a base, the inorganic pigment particles in the present recording medium for inkjet are those of alumina hydrate, γ-alumina and an intermediate thereof which are manufactured by a process wherein an aqueous dispersion containing the alumina hydrate particles is injected by spraying into a flame. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an alumina hydrate, an alumina hydrate-γ alumina intermediate, and an inkjet recording medium using γ alumina.

  The ink jet recording method is a method in which fine droplets of ink are ejected by various operating principles and adhered to a recording medium such as paper to record images, characters, etc. It has features such as easy, large recording pattern flexibility and no need for development. It has been developed to printers and other information equipment such as copiers, word processors, fax machines, and plotters, and is rapidly spreading.

  In recent years, high-performance digital cameras, digital videos, and scanners are being provided at low cost, and along with the widespread use of personal computers, there are increasing opportunities to output image information obtained from these by an inkjet recording method. For this reason, it is required to output an image comparable to silver salt photography or plate-making multicolor printing by an ink jet recording method.

  For this reason, recording devices and recording methods such as high-speed recording, high definition, and full color have been improved, but advanced characteristics have also been demanded for recording media.

  Various types of recording media have been proposed for recording media used for ink jet recording and the like. For example, a proposal for an ink jet paper in which a surface processing paint is infiltrated into a low-size base paper (see, for example, Patent Document 1), or an ink jet paper in which a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. (For example, see Patent Document 2) and proposals for ink jet recording paper having an ink-absorbing coating layer on the support surface (for example, see Patent Document 3). Further, examples using amorphous silica as a pigment in the coating layer provided on the recording medium (for example, see Patent Document 4) and examples using a water-soluble polymer coating layer (for example, see Patent Document 5). There is also a disclosure.

  Under such circumstances, recording media using alumina hydrate or γ-alumina have been attracting attention in recent years. Since alumina hydrate and γ-alumina have a positive charge, the fixing property of the dye in the ink is good, and high color development and high gloss images can be obtained. This is because it has advantages. Examples of such a recording medium include a recording medium having a layer containing an alumina hydrate having a pseudo boehmite structure as an ink-receiving layer (see, for example, Patent Documents 6 to 10), and aluminum oxide in a γ alumina type crystal form There is a disclosure (for example, see Patent Documents 11 and 12) of a recording medium having an ink receiving layer as a containing layer.

Here, the alumina hydrate is represented by the following general formula.
Al ₂ O _3-n (OH) _2n · mH ₂ O
In the formula, n represents an integer of 1, 2 or 3, and m represents a value of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. Since mH ₂ O often represents a detachable aqueous phase that does not participate in the formation of the mH ₂ O crystal lattice, m can take an integer or non-integer value. Also, when this type of material is heated, m can reach a value of zero.

  A general alumina hydrate can be produced by a known method such as hydrolysis of aluminum alkoxide or hydrolysis of sodium aluminate. Here, it has been reported that the porous structure of alumina hydrate is affected by the precipitation temperature, dissolution pH, aging time, and surfactant during production (see, for example, Non-Patent Document 1). In addition, it is generally known that pseudoboehmite in alumina hydrate has cilia and other shapes (see, for example, Non-Patent Document 2).

  On the other hand, the alumina hydrate-γ alumina intermediate is obtained by using boehmite or pseudoboehmite produced by a known method such as hydrolysis of aluminum alkoxide, hydrolysis of sodium aluminate, for example, at 400 to 425 ° C. in a high temperature oven or the like. It is obtained by heating and baking at a temperature of The alumina hydrate-γ alumina intermediate thus formed usually has a particle size on the order of μm.

  In addition, γ-alumina is obtained by heating and baking boehmite or pseudoboehmite produced by a known method such as hydrolysis of aluminum alkoxide or sodium aluminate at a temperature of 425 to 600 ° C. in a high-temperature oven or the like. Can be obtained. The γ-alumina thus formed usually has a particle size on the order of μm.

JP 52-53012 A JP-A-53-49113 Japanese Patent Laid-Open No. 55-5830 JP-A-55-51583 JP 55-146786 A US Pat. No. 4,879,166 US Pat. No. 5,104,730 JP-A-2-276670 JP-A-4-37576 Japanese Patent Laid-Open No. 5-32037 JP-A-10-129112 JP 2001-10841 A Rocek et al., Collectczech Chem Commum, 56, 1253-1262, 1991 Rocek J., et.al. Applied catalysis, 74, 29-36, 1991

  However, the particle size distribution in the alumina hydrate produced by the method described above generally has a broad distribution. Normally, when an alumina hydrate having such a wide particle size distribution is formed on a support by adding a binder if necessary, an alumina component having a small particle size on the surface of the coating layer. Happens to be distributed. Then, these small particles enter the gaps between the pores formed by the large particles near the surface, and the small particles are closely packed together, so the pore size of the porous alumina layer near the surface is reduced. There was a case.

  For this reason, in a recording medium having a layer containing alumina hydrate as an ink receiving layer, the small pores formed near the surface as described above cause the ink absorption to be hindered and the absorption speed to be slowed. Become.

  On the other hand, a proposal for a method for producing alumina having a sharp pore distribution by controlling the pore structure formed by porous alumina having a wide particle size distribution is disclosed in, for example, JP-A-55-27830. No. 1, JP-A-56-120508, JP-A-58-213632, JP-B-4-15170, JP-B-1-16773, and the like.

  However, these methods all aim at obtaining a sharp pore distribution by removing not only small components but also large components. In this way, removing large components also results in a reduction in the pore volume of the pores formed between the particles, and when these porous aluminas are used for recording medium production In some cases, ink absorbability was insufficient. In order to obtain a large pore volume for the purpose of obtaining sufficient ink absorbability, it is necessary to perform a plurality of operations for shifting from a low pH region to a high pH region. However, it takes a lot of effort to perform this operation.

  On the other hand, for example, the alumina hydrate-γ alumina intermediate and γ alumina produced by heating and baking in a high-temperature oven or the like, the sintering of the particles proceeds and the average particle size becomes too large on the order of several μm. When a recording medium is formed by adding a binder on a support to form a recording medium, if necessary, the ink absorbency is sufficiently exhibited, but only an image with low glossiness is obtained. Couldn't get.

  An object of the present invention is to solve the above-mentioned problems. When an alumina hydrate is used as a raw material and a binder is added onto a support, if necessary, a fast ink is formed. A small pore size in the pore distribution of alumina hydrate, which can provide a recording medium having an ink-receiving layer having an absorption rate and a large pore volume and without impairing gloss. It is an object of the present invention to provide a recording medium using alumina hydrate, γ-alumina, and an intermediate thereof, which is substantially removed by adsorbing the particle component that forms the particles to the particle component that forms a large pore diameter.

  The above object is achieved by the present invention described below. That is, the ink jet recording medium according to the present invention is a recording medium in which an ink receiving layer containing inorganic pigment particles is formed on a substrate, and the aqueous dispersion in which the inorganic pigment particles contain alumina hydrate particles. It is characterized by being an alumina hydrate, γ-alumina and an intermediate thereof produced by a step of spraying into a flame.

  According to the present invention, the ink absorption speed is fast, the printed dot shape can be formed cleanly with good reproducibility, and an ink receiving layer having high gloss can be obtained.

  Hereinafter, the recording medium according to the present invention in which an ink receiving layer containing alumina hydrate, γ-alumina and an intermediate thereof is formed will be described in detail. In the present invention, the above-mentioned alumina hydrate, γ-alumina and intermediates thereof (hereinafter also referred to as “alumina fine particles”) produced through a specific production process are used. That is, alumina fine particles produced by a step of spraying an aqueous dispersion containing alumina hydrate particles into a flame using an aqueous dispersion containing alumina hydrate particles as a starting material are used.

  The method for producing the alumina hydrate that can be used for the above starting materials is not particularly limited, but specifically, those that are commercially available or processed from those raw materials. , Etc. can be used. Furthermore, it is more preferable if the alumina hydrate is characterized by high transparency, glossiness, and dye fixing property, as well as good coating properties without cracks and the like during film formation. As what is marketed industrially, AS-2, AS-3 by a catalyst chemical company, 520 by Nissan Chemical Co., Ltd., etc. can be used, for example.

  These alumina hydrates usually have a fine particle size of 1 μm or less and have excellent dispersibility. Therefore, when used for forming the ink receiving layer of a recording medium, the alumina hydrate has a very good smoothness. And glossiness. Hereinafter, a specific manufacturing procedure for manufacturing alumina fine particles used as a material for forming an ink receiving layer in the present invention will be described.

  Alumina hydrate suitable as a starting material as described above is charged into a tank equipped with a stirrer while stirring. At this time, it is preferable to put a predetermined amount of pure water into the tank in advance. At this time, one or more acids selected from acetic acid, nitric acid, hydrochloric acid and formic acid may be added. However, when the pH of the aqueous dispersion is 2 or less, there is a possibility that problems such as corrosion resistance with respect to the equipment to be used may occur. Therefore, it is preferable that the pH after acid addition is higher than 2.

  The alumina fine particles used as the ink-receiving layer forming material in the present invention are produced through a step of spraying the alumina hydrate aqueous dispersion obtained in this manner into a flame. However, this step will be described next. In this step, the aqueous dispersion of alumina hydrate obtained as described above is introduced into the flame of the burner using a pump or the like. In the present invention, the fuel for generating the flame is preferably at least one fuel selected from hydrogen and oxygen, and the alumina hydrate aqueous dispersion is added to the flame obtained from these fuels. Spray injection is recommended. At this time, if the temperature of the flame is too high, the alumina hydrate may undergo a crystal transition, and α alumina may be generated by passing through γ alumina, and the sintering of alumina particles proceeds excessively. Therefore, the particle size of the obtained alumina hydrate, γ-alumina and its intermediate may be too large. For this reason, it is preferable to adjust the temperature within an appropriate range by adjusting the flame fuel charging speed, the concentration of the alumina hydrate aqueous dispersion and the charging speed. The flame temperature at the time of adding the alumina hydrate aqueous dispersion is preferably 200 ° C. or higher and 1000 ° C. or lower, more preferably 250 ° C. or higher and 700 ° C. or lower.

  Next, the alumina hydrate, γ-alumina and its intermediate produced by spraying the aqueous dispersion of alumina hydrate, which is the starting material, into the flame in the above-described process are introduced into the agglomerator and captured here. After agglomerating to a size that can be collected, it is collected by a cyclone or a bag filter.

  The thus obtained alumina hydrate, γ-alumina and intermediates thereof are components having a smaller particle size compared to the raw material alumina hydrate in the particle size distribution determined by light scattering diffraction particle size distribution measurement. In addition, since the average particle diameter is 1 μm or less, high ink absorbability and glossiness can be obtained when applied to a recording medium.

  Next, a case where a recording medium according to the present invention is produced using the produced alumina hydrate, γ-alumina and an intermediate thereof (alumina fine particles) will be described. Examples of the substrate used in the recording medium of the present invention include various types of paper such as high quality paper, medium quality paper, art paper, bond paper, recycled paper, baryta paper, cast coated paper, and resin coated paper. Among these, when a mirror finish such as cast processing can be performed, a high-grade silver salt photographic texture can be obtained, so that wood pulp and mainly sized paper, non-size paper, etc. A fibrous substrate made of a filler can be mentioned as a preferable one.

  In forming the ink receiving layer in the recording medium according to the present invention, a binder can be used as necessary. As a suitable binder, the following water-soluble polymers are used. Examples of the water-soluble polymer include cellulose derivatives such as polyvinyl alcohol or a modified product thereof, starch or a modified product thereof, gelatin or a modified product thereof, casein or a modified product thereof, gum arabic, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose. , SBR latex, NBR latex, conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer, functional group modified polymer latex, vinyl copolymer latex such as ethylene vinyl acetate copolymer, polyvinyl pyrrolidone, anhydrous Mention may be made, for example, of copolymers of maleic acid with other monomers, acrylic ester copolymers and the like. These binders can be used alone or in combination.

  The mixing ratio of the alumina fine particles and the binder is a mass ratio, and can be arbitrarily selected from a range of preferably 5: 1 to 15: 1. By setting the amount of the binder within the above range, the mechanical strength of the ink receiving layer can be further increased, cracking and powder falling off during the formation of the ink receiving layer can be prevented, and a more suitable pore volume can be maintained. It becomes possible.

  On the other hand, the coating liquid for forming the ink receiving layer may further include a dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, an antifoaming agent, water resistance, if necessary. It is also possible to add an agent, a release agent, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant and the like within a range not impairing the effects of the present invention.

  In the recording medium of the present invention, as a method for forming the ink receiving layer, a method in which the dispersion solution containing alumina fine particles produced as described above is applied onto a substrate using a coating apparatus and dried is used. it can. The coating method is not particularly limited, and commonly used coating techniques such as blade coater, air knife coater, roll coater, curtain coater, bar coater, gravure coater, die coater, spray device, etc. can be used. .

As the coating amount of the coating liquid at the time of forming the ink receiving layer, in order to improve the fixability of the colorant component in the recording liquid such as dye and the smoothness of the ink receiving layer, it is converted to dry solid Is preferably 40 g / m ² or less, more preferably 20 to 40 g / m ² . If necessary, after the ink receiving layer is formed, a baking treatment can be performed. When the dry solid content is 20 g / m ² or more, the ink absorbability does not decrease. Further, the dye fixing effect is sufficient, and the dye is fixed to the ink receiving layer, so that sufficient color development can be obtained.

  Furthermore, it is preferable to perform a smoothing process such as a cast process after forming the ink receiving layer. As a method for casting, there are a direct method, a gelation method, and a rewet method. Among these methods, the direct method is one in which the surface of the layer is pressed against a heated mirror drum and dried while the coating layer applied on the substrate at the time of forming the coating layer is still wet. In the gelation method, the layer is brought into contact with a gelling agent bath while the coating layer on the substrate is still wet when the coating layer is formed. The heated mirror drum is pressed and dried. Further, in the rewetting method, after forming a coating layer, it is again treated with hot water to return it to a wet state, and the surface of this coating layer is pressed against a heated mirror drum and dried. By these methods, high gloss can be obtained on the surface of the coating layer. However, when a dense substrate is used for the purpose of obtaining a recording medium comparable to the texture of the silver salt photograph provided in the present invention, the rewetting method can be preferably used as the gloss treatment. This is because when a wet coating layer is dried by pressure bonding to a mirror drum, the evaporation of moisture from the back surface is extremely limited in the case of a dense substrate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

<Production Example 1 of Alumina Fine Particle>
First, aluminum octaoxide was synthesized by the method described in US Pat. Nos. 4,242,271 and 4,202,870, and then hydrolyzed to produce an alumina slurry. Water was added until the solid content of the alumina hydrate was 5%. Next, after raising the temperature to 80 ° C. and carrying out an aging reaction for 10 hours, the colloidal sol was spray-dried to obtain alumina hydrate 1. This alumina hydrate 1 was mixed and dispersed in pure water to obtain an alumina hydrate particle aqueous dispersion in which the solid content of alumina hydrate was 0.5%. The dispersion was introduced into the burner at a rate of 15 L (liter) per hour by a pump, sprayed into a flame using oxygen as fuel, and the produced alumina particles 1 were collected by a bag filter.

  The alumina hydrate 1 as the starting material obtained above and the alumina fine particle 1 as the product were measured by X-ray diffraction, respectively. As a result, the alumina hydrate 1 was pseudo boehmite, and the alumina fine particle 1 was And alumina hydrate-γ alumina intermediate.

<Production Example 2 of Alumina Fine Particle>
First, an alumina hydrate particle aqueous dispersion in which alumina hydrate 1 as a starting material prepared in Production Example 1 was mixed and dispersed in pure water to make the solid content of alumina hydrate 0.5%. Obtained. The dispersion was introduced into a burner at a rate of 10 L (liter) per hour by a pump, sprayed into a flame using oxygen as fuel, and the produced alumina fine particles 2 were collected by a bag filter. The obtained alumina fine particles 2 were measured by an X-ray diffraction method and found to be γ-alumina.

<Production Example 3 of Alumina Fine Particle>
The alumina hydrate 1 prepared in Production Example 1 was placed in an alumina crucible and baked in a high temperature oven at 425 ° C. for 1 hour to obtain alumina fine particles 3. The obtained alumina fine particles 3 were measured by an X-ray diffraction method and found to be alumina hydrate-γ alumina intermediate.

<Production Example 4 of Alumina Fine Particle>
The alumina hydrate 1 prepared in Production Example 1 was placed in an alumina crucible and baked in a high temperature oven at 500 ° C. for 1 hour to obtain alumina fine particles 4. The obtained alumina fine particles 4 were measured by an X-ray diffraction method and found to be γ-alumina.

[Example 1]
An ink receiving layer was formed as follows on a fibrous substrate having a basis weight of 150 g / m ² and a Steecht size of 200 seconds. The alumina fine particles 1 obtained in Production Example 1 were dispersed in pure water using acetic acid as a dispersant to obtain a 20 mass% dispersion. Next, polyvinyl alcohol PVA117 (trade name: manufactured by Kuraray Co., Ltd.) was dissolved in pure water as a binder to obtain a 9% by mass solution. The dispersion of the alumina fine particles 1 obtained above and the polyvinyl alcohol solution were mixed and stirred so that the solid content of the dispersion of the alumina fine particles 1 and the solid content of the polyvinyl alcohol solution were 100: 10 in mass ratio. Thus, a coating solution for forming a solvent absorption layer was obtained. This coating solution was applied onto the above fibrous substrate so that the dry weight was 30 g / m ² , thereby forming an ink receiving layer. The surface of the coated ink receiving layer was subjected to a rewet cast treatment using hot water (80 ° C.) using a rewet cast coater to obtain a recording medium 1 of this example.

[Example 2]
A recording medium 2 was obtained in the same manner as in Example 1 except that the alumina fine particles 2 were used instead of the alumina fine particles 1.

[Comparative Example 1]
A recording medium 3 was obtained in the same manner as in Example 1 except that the alumina fine particles 3 were used instead of the alumina fine particles 1.

[Comparative Example 2]
A recording medium 4 was obtained in the same manner as in Example 1 except that the alumina fine particles 4 were used instead of the alumina fine particles 1.

<Evaluation>
According to the following methods and evaluation criteria, the recording media 1 to 4 of Examples and Comparative Examples obtained as described above were evaluated, and the obtained results are shown in Table 1. Images were formed using a photo printer (trade name: BJ F870 manufactured by Canon Inc.) using an ink jet method, and evaluated for two points, ink absorbency and glossiness. For the images, several types of photographic images were prepared, printed using the highest image quality mode of the above-mentioned apparatus, and comprehensively evaluated from the obtained images. The evaluation was made by paying attention to the composite black portion, leaf green color, and sky blue portion in the image. The evaluation method and evaluation criteria for each evaluation item are shown below.

(Ink absorption)
The presence or absence of beading was judged visually and evaluated according to the following criteria.
A: Composite black with the largest amount of ink does not generate.
B: Recognized in composite black, but not observed in leaf green or sky blue.
C: Other than A and B above.

(Glossiness)
Using a digital variable gloss meter (manufactured by Suga Test Instruments Co., Ltd.), the 20 ° glossiness of the ink receiving layer was measured based on JIS-Z-8741. The glossiness obtained was evaluated according to the following criteria.
A: A gloss value of 20% or more.
B: Glossiness of 10% or more and less than 20%.
C: Glossiness less than 10%.

As an application example of the present invention, when an alumina hydrate is used as a raw material, and a coating is formed on a support by adding a binder if necessary, it has a high ink absorption rate and a large pore volume. And a recording medium on which an ink receiving layer containing alumina fine particles is formed without impairing gloss. The alumina fine particles used in the recording medium are produced by a specific production process, whereby the particle component that forms a small pore size in the pore distribution of alumina hydrate is adsorbed to the particle component that forms a large pore size. Thus, the above-described excellent recording medium can be provided because of the alumina hydrate, γ-alumina, and intermediates thereof substantially removed.

Claims (3)

  In a recording medium in which an ink receiving layer containing inorganic pigment particles is formed on a substrate, the inorganic pigment particles are produced by spraying an aqueous dispersion containing alumina hydrate particles into a flame. An inkjet recording medium, characterized by being alumina hydrate, γ-alumina and intermediates thereof.   The inkjet recording medium according to claim 1, wherein the aqueous dispersion contains at least one acid selected from acetic acid, nitric acid, hydrochloric acid, and formic acid. The inkjet recording medium according to claim 1, wherein at least one fuel selected from hydrogen and oxygen is used as a fuel for generating the flame.