JP2009051019A - Method for manufacturing recording medium - Google Patents

Abstract

Provided is a method for producing a recording medium in which a porous ink receiving layer has high ink absorptivity and transparency, and prevents generation of cracks and peeling of the porous ink receiving layer.
A surface treatment step of applying a borate aqueous solution on an undercoat layer, a coating containing a pigment and polyvinyl alcohol on the undercoat layer while the surface of the undercoat layer coated with the borate aqueous solution is in a wet state A step of forming a porous ink receiving layer by coating and drying the liquid, and the coating amount after drying of the borate aqueous solution is based on the borate based on the total mass of the porous ink receiving layer. The content of polyvinyl alcohol in the porous ink receiving layer is from 7 parts by weight to 13 parts by weight with respect to 100 parts by weight of the pigment in the porous ink receiving layer. It is.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a recording medium suitable for inkjet recording.

  In recent years, ink jet recording methods have greatly improved ink droplet size and improvement as recording characteristics such as higher recording speed and higher definition have improved, and image quality has been further improved. For this reason, as represented by a high-quality inkjet printer called a photo printer, an image comparable to that of a silver salt photograph can be obtained. An increasing number of users print full-color images taken with a digital camera or the like with an inkjet printer.

  Therefore, in order to cope with such a situation, a high glossy recording medium can be obtained by using a casting method for a recording medium having an ink receiving layer using alumina hydrate and polyvinyl alcohol as a binder. It has been known. Patent Document 1 discloses an invention using a rewet cast method as a technique for improving a cast method capable of obtaining a higher gloss.

In addition to the gloss, studies are being made to satisfy the characteristics required for the recording medium. Patent Document 2 discloses an invention that solves the problem of preventing the occurrence of microcracks that occur when the coating liquid for the ink receiving layer is dried. That is, Patent Document 2 proposes a resin film in which an alumina sol coating liquid containing alumina hydrate, polyvinyl alcohol, and a predetermined amount of boric acid or boron compound is used, and these are applied.
In Patent Document 3, the order and state of the coating process of the boric acid or borate solution and the coating liquid for the ink receiving layer are made special so that the occurrence of microcracks and the coating liquid over time It solves the problem of increasing viscosity.

Patent Document 4 discloses a method of gelling a coating liquid for an ink receiving layer by applying an aqueous alkali metal salt solution on a substrate.
Conventionally, as shown in Patent Document 5, neutral paper has been preferably used from the viewpoint of long-term storage as a substrate for a recording medium.
JP 2001-138628 A JP-A-7-76161 International Publication No. 2003/101746 Pamphlet JP 2002-0667474 A JP 2004-230777 A

In recent years, with the increase in recording speed on a recording medium, the recording medium has been required to have high ink absorbability. As such a recording medium having high ink absorbability, a recording medium having a porous ink receiving layer containing pigment particles and a polyvinyl alcohol-based binder is effective. However, a coating liquid for a porous ink receiving layer comprising pigment particles and a polyvinyl alcohol-based binder has a problem that the viscosity of the coating liquid increases with time. Further, when an attempt is made to form a porous ink-receiving layer having a good ink absorbability of 25 g / m ² or more using this coating solution, there is a problem that minute cracks are generated during drying.

  The method described in Patent Document 2 is intended to prevent an increase in the viscosity of the coating liquid and the generation of minute cracks, but the solution to these problems has not been sufficient.

  On the other hand, in the recording medium of Patent Document 3, it is possible to prevent the viscosity of the coating liquid from increasing with time and the occurrence of microcracks. However, when the method of the cited document 3 is applied to neutral paper provided with an undercoat layer such as calcium carbonate, there is a case where a new problem that the ink receiving layer peels off after ink jet recording may occur.

  Further, the recording medium described in Patent Document 4 also has a problem that the formed ink receiving layer is peeled off depending on the amount and type of alkali metal salt applied. Furthermore, in patent document 4, the coating liquid for ink receiving layers was apply | coated after drying of the alkali metal salt aqueous solution provided on the base material. For this reason, once dried and solidified, the alkali metal salt is difficult to redissolve or penetrate into the coating liquid for the ink receiving layer, and the gelation of the ink receiving layer is uneven and the speed is slow.

  The present invention has been made in view of the above situation, and using a neutral paper excellent in long-term storage stability, the porous ink receiving layer has high ink absorptivity and transparency, and has cracks. It is an object of the present invention to provide a method for producing a recording medium that prevents generation and peeling of a porous ink receiving layer.

In order to solve the above problems, the present invention is characterized by having the following configuration.
1. A method for producing a recording medium in which a porous ink receiving layer is provided on a neutral paper substrate provided with an undercoat layer,
Preparing a neutral paper substrate provided with an undercoat layer,
A surface treatment step of coating an aqueous borate solution on the undercoat layer;
While the surface of the undercoat layer coated with the borate aqueous solution is in a wet state, a coating liquid containing a pigment and polyvinyl alcohol is applied onto the undercoat layer and dried to form a porous ink receiving layer. Process,
Have
The undercoat layer contains a pigment containing a salt of a weak acid and a strong base, and a binder, and
The coating amount after drying of the borate aqueous solution is 1% by mass or more and 2% by mass or less based on borate with respect to the mass of the entire porous ink receiving layer,
The content of polyvinyl alcohol in the porous ink receiving layer is 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the pigment in the porous ink receiving layer. Manufacturing method.

  2. 2. The method for producing a recording medium according to 1 above, wherein the pigment containing the salt of the weak acid and the strong base is at least one pigment selected from the group consisting of calcium carbonate, barium carbonate, and magnesium carbonate. .

  3. 3. The method for manufacturing a recording medium according to 1 or 2, wherein the borate aqueous solution further contains a cationic polymer.

4). 4. The recording medium according to any one of 1 to 3 above, wherein the coating amount of the porous ink receiving layer after drying is 25 g / m ² or more and 45 g / m ² or less. Method.

  In the present invention, the coating amount after drying the borate aqueous solution is set to 1% by mass or more based on the borate based on the total mass of the porous ink receiving layer, thereby forming the porous ink receiving layer. Generation of cracks can be suppressed. Moreover, the coating amount after drying of the borate aqueous solution is set to 2% by mass or less based on the borate with respect to the total mass of the porous ink receiving layer, so that the porous ink receiving layer can be peeled off. There can be no recording medium. At the same time, the porous ink receiving layer can have high ink absorbability and transparency.

The present invention provides a recording medium in which an undercoat layer containing a pigment containing a salt of a weak acid and a strong base, a binder, and a porous ink receiving layer are provided in this order on a neutral paper substrate. It relates to a method and has the following steps.
(1) A step of preparing a neutral paper base material provided with an undercoat layer.
(2) A surface treatment step of coating an aqueous borate solution on the undercoat layer.
(3) While the surface of the undercoat layer coated with the borate aqueous solution is in a wet state, a coating liquid containing a pigment and polyvinyl alcohol is applied onto the undercoat layer and dried to form a porous ink receiving layer. Process.

  In the step (2), the coating amount after drying of the borate aqueous solution is 1% by mass or more and 2% by mass or less with respect to the total mass of the porous ink receiving layer based on the borate. Characterized by the point of coating. That is, in the step (2), (mass of borate (solid content)) / (mass of the entire porous ink receiving layer) × 100 after drying is 1% by mass or more and 2% by mass or less. .

  In step (3), the content of polyvinyl alcohol in the porous ink receiving layer is 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the pigment in the porous ink receiving layer. Characterized by points.

  In the method for producing a recording medium of the present invention, first, in step (1), a neutral paper base material provided with an undercoat layer containing a pigment containing a salt of a weak acid and a strong base and a binder is prepared. The neutral paper base provided with this undercoat layer is a neutral paper base provided with a pre-manufactured undercoat layer even if it is prepared by applying a coating liquid for the undercoat layer onto the neutral paper base and drying it. A paper substrate may be prepared. When applying the coating liquid for undercoat layers on a neutral paper base material, this undercoat layer coating liquid can contain a pigment, a binder, water, and other additives as required.

  Further, the neutral paper base is neutral, and this undercoat layer contains a pigment containing a salt of a weak acid and a strong base. For this reason, the surface of the undercoat layer is alkaline, and it is possible to maintain the surface of the undercoat layer alkaline even when a borate aqueous solution is applied onto the undercoat layer in a subsequent surface treatment step. Become.

This undercoat layer is preferably provided as a coating layer having a thickness that completely covers the cellulose pulp fibers and the texture, and the dry coating amount is preferably 10 g / m ² or more, preferably 15 g / m ² or more. More preferably. When the dry coating amount is less than 10 g / m ² , it may be difficult to completely cover the cellulose pulp fibers and the texture of the neutral paper substrate with the undercoat layer. As a result, when the coating liquid for the porous ink receiving layer is applied, uneven coating (such as stripe-shaped unevenness) due to the fibers or texture of the neutral paper substrate may occur. In addition, since cellulose pulp fibers are present in the porous ink receiving layer or in the vicinity of the surface thereof, it may be difficult to make the surface of the recording medium good and have a uniform photographic tone high gloss surface. is there.

  Next, in step (2), an aqueous borate solution is applied onto the undercoat layer (surface treatment step). The borate aqueous solution preferably contains a cationic polymer as necessary. By containing the cationic polymer, the adhesion to the porous ink receiving layer is further improved.

  Next, a coating solution for a porous ink receiving layer containing a pigment and polyvinyl alcohol is applied in a wet state where the borate aqueous solution applied in step (2) is not dried by drying (step (3). )).

  In this step (3), the coating liquid for the porous ink receiving layer comes into contact with an aqueous borate solution showing alkalinity existing on the surface of the undercoat layer. Here, this borate increases the coating liquid for the porous ink receiving layer by destroying the dispersion state of the sol solution of alumina hydrate contained in the coating liquid for the porous ink receiving layer. Make it sticky.

  Further, the coating liquid for the porous ink receiving layer contains polyvinyl alcohol that can crosslink with borate. Then, the step (3) is in a wet state, and the borate easily comes into contact with the polyvinyl alcohol in the coating liquid for the porous ink receiving layer, and in the coating liquid for the porous ink receiving layer. It is easy to penetrate. Therefore, the gelation of the coating liquid for the porous ink receiving layer and the crosslinked structure of polyvinyl alcohol via borate can be easily formed.

  As described above, the coating liquid for the porous ink receiving layer needs to be applied while the borate aqueous solution is in a wet state. Here, the “wet state” represents a state in which all or part of the borate aqueous solution applied in the step (2) is not dried and is in a solution state. When the borate aqueous solution is in a dry state (when solidified), when the coating liquid for the porous ink receiving layer is applied, the borate is in a solid state. It takes a long time to dissolve and penetrate into the coating solution. Then, before the borate completely penetrates into the coating liquid for the porous ink receiving layer, the polyvinyl alcohol in the coating liquid for the porous ink receiving layer penetrates into the neutral paper substrate. Will be. As a result, uniform gelation does not occur in the porous ink receiving layer, or the degree of gelation is insufficient. Then, cracks occur in the entire recording medium.

  In the step (3), the coating amount of the borate aqueous solution is 1% by mass or more and 2% by mass or less based on the borate with respect to the mass of the entire porous ink receiving layer. For this reason, the rapid crosslinking reaction at the interface between the undercoat layer and the porous ink receiving layer can be suppressed, and the anchor effect between the undercoat layer and the porous ink receiving layer can be obtained with polyvinyl alcohol.

  That is, when the coating amount of the borate aqueous solution is less than 1% by mass with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content), Gelation is insufficient. In addition, a sufficient cross-linked structure cannot be formed, and microcracks are generated.

  On the other hand, when the coating amount of the borate aqueous solution exceeds 2% by mass with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content), the undercoat layer and the porous ink Sudden gelation of the ink receiving layer at the interface of the receiving layer occurs, so that a sufficient anchoring effect between the layers by polyvinyl alcohol cannot be obtained. As a result, the porous ink receiving layer is peeled off.

  In step (3), the content of polyvinyl alcohol in the porous ink receiving layer is 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the pigment in the porous ink receiving layer. . For this reason, it has sufficient polyvinyl alcohol to be able to crosslink with the borate and does not greatly affect the ink absorbability.

  That is, when the content of polyvinyl alcohol in the porous ink receiving layer is less than 7 parts by mass with respect to 100 parts by mass of the pigment in the porous ink receiving layer, a sufficient binding effect is obtained due to insufficient polyvinyl alcohol. It can no longer be obtained. As a result, micro cracks are generated.

  On the other hand, when the content of polyvinyl alcohol in the porous ink receiving layer exceeds 13 parts by mass with respect to 100 parts by mass of the pigment in the porous ink receiving layer, the ink absorbability is greatly affected. As a result, a porous ink receiving layer having high ink absorbability cannot be obtained.

  An example of a method for producing a recording medium of the present invention is shown in FIG. First, an undercoat layer 2 containing a pigment containing a salt of a weak acid and a strong base and a binder is provided on a neutral paper substrate 1 (step (1); FIG. 1 (a)). Then, an aqueous borate solution 4 is applied onto the support 3 composed of the undercoat layer 2 and the neutral paper substrate 1 (step (2); surface treatment step; FIG. 1 (b)). At this time, the surface pH of the neutral paper substrate 1 is neutral, and the undercoat layer 2 contains a pigment containing a salt of a weak acid and a strong base, so that the paper surface pH of the undercoat layer 2 is pH 8 to 9.5. It is about alkaline.

  Next, with the surface of the undercoat layer coated with the borate aqueous solution in a wet state, a coating liquid containing a pigment and polyvinyl alcohol is applied onto the undercoat layer and dried to form the porous ink receiving layer 5. It forms (process (3); FIG.1 (c)). The coating amount after drying of this borate aqueous solution is as small as 1% by mass or more and 2% by mass or less with respect to the mass of the entire porous ink receiving layer based on borate. Therefore, the borate present in the borate aqueous solution on the undercoat layer is easily diffused into the coating liquid for the porous ink receiving layer, and the coating liquid for the porous ink receiving layer is gelled. And crosslinking of polyvinyl alcohol in the coating solution easily occurs. As a result, it is possible to effectively prevent the occurrence of cracks and peeling during the formation of the porous ink receiving layer. At the same time, the porous ink receiving layer can have high ink absorbability and transparency.

Below, each material used by this invention is demonstrated.
1. Neutral paper substrate The neutral paper substrate used in the present invention is not particularly limited as long as it is neutral and can be surface-treated. However, when an acidic substrate (acidic paper) is used among paper substrates, yellowing occurs after long-term storage, and it becomes difficult to keep the surface of the undercoat layer alkaline in the steps (2) and (3). It is necessary to use a neutral paper substrate (neutral paper).

2. Undercoat layer (pigment)
The pigment used for the undercoat layer is a pigment containing a salt of a weak acid and a strong base. The pigment is preferably at least one pigment selected from the group consisting of calcium carbonate, barium carbonate, and magnesium carbonate. Here, when a pigment showing neutrality in an aqueous solution such as a strong acid and strong base salt is used instead of the pigment containing the weak acid and strong base salt of the present invention, the pH of the paper surface of the undercoat layer cannot be maintained alkaline. There is.

  In general, when a salt of a strong acid and a strong base or a pigment that shows neutrality in an aqueous solution is used, the viscosity is lowered and a liquid flow occurs, so that a uniform and good glossy surface may not be obtained. As a result, in order to obtain a good glossy surface, a step of coating the borate aqueous solution a plurality of times in the subsequent step may be required, or the transparency of the porous ink receiving layer may be lowered. .

As the binder for the undercoat layer, conventionally known binders can be used. Further, considering the stability of the environmental curl of the recording medium, the undercoat layer is preferably provided on both the front and back surfaces of the neutral paper substrate.
The dry coating amount of the undercoat layer is preferably 10 g / m ² or more, and more preferably 15 g / m ² or more. When the dry coating amount is less than 10 g / m ² , it becomes difficult to completely cover the cellulose pulp fibers and the texture of the neutral paper base material, which may affect the gloss.

3. Borate aqueous solution (Borate)
As borate, borate (for example, orthoborate, InBO ₃ , ScBO ₃ , YBO ₃ , LaBO ₃ , Mg ₃ (BO ₃ ) ₂ , Co ₃ (BO ₃ ) ₂ ), diborate (for example, Mg ₂ B ₂ O ₅ , Co ₂ B ₂ O ₅ ), metaborates (eg, LiBO ₂ , Ca (BO ₂ ) ₂ , NaBO ₂ , KBO ₂ ), tetraborate (eg, Na ₂ B ₄ O ₇₎・ 10H ₂ O), pentaborate (for example, KB ₅ O ₈ · 4H ₂ O, Ca ₂ B ₆ O ₁₁ · 7H ₂ O, CsB ₅ O ₅ ), etc. are used, but they cause a rapid crosslinking reaction. Sodium tetraborate (borax) is preferable from the point of being capable of forming.

(Cationic polymer)
In order to prevent peeling of the porous ink receiving layer, it is preferable to add a cationic polymer to the borate aqueous solution. It is considered that by adding a cationic polymer, it is possible to suppress a rapid crosslinking reaction of polyvinyl alcohol present in the coating liquid for the porous ink receiving layer. As a result, peeling of the porous ink receiving layer can be more effectively suppressed. As the cationic polymer, monoallylamine salts, vinylamine salts, dicyandiamide / polyethyleneamine polycondensates, and the like can be used.

(Crosslinking agent)
The borate aqueous solution may further contain a crosslinking agent. As a crosslinking agent that can be suitably used in the present invention, a crosslinking agent that can be crosslinked by causing a crosslinking reaction with polyvinyl alcohol contained in the porous ink receiving layer is preferable, and those that do not impair the effects of the present invention can be used. As the crosslinking agent, boric acid is particularly preferable.

4). Porous ink receiving layer The coating amount after drying of the coating liquid for the porous ink receiving layer is preferably 25 g / m ² or more and 45 g / m ² or less. When the coating amount is less than 25 g / m ² , it is particularly sufficient to perform printing using a printer in which a plurality of light-color inks are added in addition to black ink in addition to three colors of cyan, magenta, and yellow. Ink absorbability may not be obtained. That is, ink overflow may occur and bleeding may occur, and the ink dye may diffuse to the neutral paper base material and the print density may decrease. On the other hand, when the coating amount exceeds 45 g / m ² , the occurrence of cracks may not be completely suppressed. A coating amount of 25 g / m ² or more is preferable because a porous ink receiving layer exhibiting sufficient ink absorbency even in a high temperature and high humidity environment can be obtained. Furthermore, when the coating amount is 45 g / m ² or less, coating unevenness of the porous ink receiving layer hardly occurs and a porous ink receiving layer having a stable thickness can be produced.

The porous ink receiving layer preferably has the following physical properties in terms of pore properties in order to achieve the purpose and effect such as high ink absorbability and high ink fixability. First, the pore volume of the porous ink receiving layer is preferably in the range of 0.1 cm ³ / g to 1.0 cm ³ / g. That is, when the pore volume is less than 0.1 cm ³ / g, sufficient ink absorption performance cannot be obtained, resulting in a porous ink receiving layer with poor ink absorbability. May occur. On the other hand, when the pore volume exceeds 1.0 cm ³ / g, there is a tendency that cracks and powder fall off easily occur in the porous ink receiving layer.

The BET specific surface area of the porous ink receiving layer is preferably 20 m ² / g or more and 450 m ² / g or less. When the BET specific surface area of the porous ink receiving layer is less than 20 m ² / g, sufficient glossiness may not be obtained. Moreover, since haze increases (because transparency decreases), there is a possibility that white haze may be seen in the image itself. Furthermore, in this case, there is a risk of lowering the dye adsorbability in the ink. On the other hand, if the BET specific surface area of the porous ink receiving layer exceeds 450 m ² / g, cracks may occur in the porous ink receiving layer. The pore volume and the BET specific surface area in the porous ink receiving layer are determined by a nitrogen adsorption / desorption method.

(Pigment)
As the pigment used in the porous ink receiving layer of the present invention, silica and alumina hydrate are preferable, and examples of the alumina hydrate include those represented by the following general formula (X).
Al ₂ O _3-n (OH) _2n · mH ₂ O ... (X)
(In the above formula, n represents 0, 1, 2 or 3, and m represents a value in the range of 0 to 10, preferably 0 to 5. However, m and n cannot be 0 simultaneously. MH ₂ Since O often represents detachable water that is not involved in the formation of the crystal lattice, m can take an integer or non-integer value, and when this type of material is heated, m becomes A value of 0 can be reached).

  As for the crystal structure of alumina hydrate, it transitions from amorphous, kibsite-type, boehmite-type alumina to γ, σ, η, θ, α-type alumina oxide according to the heat treatment temperature. It is known. Any of these crystal structures can be used in the present invention.

  A preferred alumina hydrate in the present invention is an alumina hydrate that exhibits a boehmite structure or an amorphous state by analysis by an X-ray diffraction method. Examples of the alumina hydrate include alumina hydrates described in JP-A-7-232473, JP-A-8-132731, JP-A-9-66664, JP-A-9-76628, and the like. Can do.

  Alumina hydrate is adjusted in pore properties in the production process, but the pore volume is preferably 0.3 ml / g or more and 1.0 ml / g or less, more preferably 0.35 ml / g or more. 0.9 ml / g or less. The BET specific surface area of the alumina hydrate is preferably 50 ml / g or more and 350 ml / g or less, more preferably 100 ml / g or more and 250 ml / g or less.

  The BET method referred to in the present invention is one of the powder surface area measurement methods by the vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from the adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the pressure or volume change of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, called the BET equation, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  The coating liquid for the porous ink receiving layer is a coating liquid containing at least a pigment and polyvinyl alcohol. In the preparation of the coating liquid for the porous ink receiving layer, a pigment dispersion and an aqueous solution containing polyvinyl alcohol are prepared. And it is preferable to mix these liquids using a mixing apparatus etc. to make a coating liquid. By adjusting the coating liquid in this way, it is possible to reduce the time-dependent increase in the coating liquid viscosity and gelation that occur during the manufacturing process, and to improve the production efficiency.

  Moreover, when using an alumina hydrate as a pigment, it is preferable that the solid content density | concentration of the alumina hydrate in the dispersion liquid is 10 to 30 mass%. When the solid content concentration of alumina hydrate exceeds 30% by mass, the viscosity of the dispersion of alumina hydrate increases, resulting in an increase in the viscosity of the coating liquid for the porous ink receiving layer. There may be a problem with the coating properties of the liquid.

Moreover, in the undercoat layer and the porous ink receiving layer, the following can be appropriately contained as necessary as other additives.
Pigment dispersant, thickener, fluidity improver, antifoaming agent, antifoaming agent, mold release agent, penetrating agent, coloring pigment, coloring dye, fluorescent whitening agent, ultraviolet absorber, antioxidant, preservative, Antifungal agents, water resistance agents, dye fixing agents, etc.

(Polyvinyl alcohol)
In the present invention, polyvinyl alcohol having a saponification degree of 70% or more and 100% or less is preferably used among the polyvinyl alcohols. Further, the content of polyvinyl alcohol in the porous ink receiving layer needs to be 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the alumina hydrate. Moreover, it is preferable that content of polyvinyl alcohol shall be 8 to 12 mass parts.

(Crosslinking agent)
The porous ink receiving layer may contain a crosslinking agent. As the crosslinking agent suitably used in the present invention, those that can be cured by causing a crosslinking reaction with the polyvinyl alcohol are preferable, and those that do not impair the effects of the present invention can be used. As the crosslinking agent, boric acid is particularly preferable. The amount of boric acid used is in the range of 1.0 mass% or more and 15.0 mass% or less of boric acid (solid content) with respect to 100 mass parts of polyvinyl alcohol (solid content conversion) in the porous ink receiving layer. It is preferable to use it. When used in a range exceeding 15.0 mass, the temporal stability of the coating liquid for the porous ink receiving layer may be affected.

  As a coating apparatus for each coating liquid in the porous ink receiving layer, the surface treatment process, and the like, various coating apparatuses can be appropriately used so that an appropriate coating amount can be obtained. For example, various types of blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, gravure coaters, and extrusion type coaters can be used. Also, a coater using a slide hopper system, a size press, or the like can be used.

  The coating apparatus is appropriately selected and used, and is used on-machine or off-machine. In addition, the coating solution may be heated for the purpose of adjusting the viscosity of the coating solution at the time of coating, or the coater head can be heated.

  Various apparatuses can be appropriately selected and used for drying after the application of the coating liquid for the porous ink receiving layer. For example, a hot-air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, a dryer using infrared rays, a heated dryer, a microwave, or the like can be used.

  In addition, a coating liquid in which a colorant deterioration preventing material is dissolved in a solvent can be overcoated on the formed porous ink receiving layer. The solvent for dissolving the colorant deterioration preventing agent may be any solvent that can dissolve the colorant deterioration preventing agent, and various organic solvents can be used. Examples of the organic solvent include, but are not limited to, esters such as ethyl acetate and butyl acetate, ketones such as methyl isobutyl ketone, methyl ethyl ketone, and acetone, ethers such as diethyl ether and ethyl methyl ether, and isopropanol. And alcohols such as methanol and ethanol.

5. Casting Method In the present invention, after forming a porous ink receiving layer on a neutral paper substrate having an undercoat layer, a glossy surface can be formed on the surface of the porous ink receiving layer by a casting method. Below, this manufacturing method is demonstrated.

  The casting method is a method in which a porous ink receiving layer in a wet state or a plastic state is pressure-bonded to a heated mirror-like drum (cast drum) surface, dried in the pressure-bonded state, and the mirror surface is made porous. It is a method of copying on the surface of the quality ink receiving layer. There are three typical methods for this purpose: a direct method, a rewet method (indirect method), or a coagulation method. Any of these casting methods can be used, but the wet casting method is more preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. First, measurement methods of various physical property values used in the present invention will be described.

<BET specific surface area, pore volume>
The BET specific surface area and pore volume of the recording medium were measured with an apparatus (manufactured by Cantachrome, Auto Soap 1) using a nitrogen adsorption / desorption method after sufficiently degassing the alumina hydrate. The BET specific surface area was calculated using the method of Brunauer et al. (See J. Am. Chem. Soc., 60, 309, 1938). The pore volume was calculated using the method of Barrett et al. (See J. Am. Chem. Soc., 73, 373, 1951).

[Example 1]
<Production of neutral paper base>
A neutral paper base was prepared as follows.
First, 10 parts by weight of light calcium carbonate and 0.1 parts by weight of an internal sizing agent (alkyl ketene dimer) were added to 100 parts by weight of pulp having the following composition to prepare a paper stock.
Freeness 450 ml CSF (Canadian Standard Freeness), hardwood bleached kraft pulp (LBKP) 90 parts by weight Freeness 350 ml CSF, conifer bleached kraft pulp (NBKP)
10 parts by weight.

Next, this paper stock was made with a long paper machine and then dried with a multi-cylinder cylinder dryer for calendar treatment. And the neutral paper base material of basic weight 150g / m < ² > was obtained.

<Coating of undercoat layer>
An undercoat layer was formed on the surface of the neutral paper base as follows.
First, a slurry having a light calcium carbonate / kaolin / titanium oxide ratio of 70/20/10 was prepared as a coating solution used for forming the undercoat layer. Next, 20 parts by mass of a binder having a mass ratio of 15/5 of styrene-butadiene latex / starch was added to 100 parts by mass of the pigment (light calcium carbonate / kaolin / titanium oxide). Next, water was added to the mixture so as to have a solid content of 60% by mass and adjusted to obtain a coating solution for an undercoat layer.

Next, using a blade coater, this coating liquid is coated and dried on both sides of the neutral paper base so that the dry coating amount is 15 / m ^2. A support provided with an undercoat layer of m ² was obtained.

<Surface treatment process>
A surface treatment comprising the following steps was performed on the undercoat layer obtained above.
First, a borate aqueous solution having the following composition heated to 30 ° C. was prepared.
(Borate aqueous solution)
Sodium tetraborate: 5.0 g
Isopropanol: 0.15g
Ion exchange water: 94.85 g.

Next, using an air knife coater so that the wet coating amount 10.8 g / m ² (corresponding to a coating weight 0.54 g / m ² when dry), the borate solution of the support Coating was performed on one side at 30 m / min.

<Coating process of coating liquid for porous ink receiving layer>
Next, while the borate aqueous solution after application in the <surface treatment step> is in a wet state, that is, immediately after the borate aqueous solution is applied on the undercoat layer, the borate aqueous solution is applied. A porous ink receiving layer was formed on the undercoat layer as it was. Under the present circumstances, the coating liquid used for formation of a porous ink receiving layer was adjusted as follows.

  That is, first, Dispersal HP14 (manufactured by Sasol) and acetic acid as alumina hydrate were added to pure water to obtain a 20 mass% alumina hydrate dispersion. Acetic acid was added so that alumina hydrate solid content: acetic acid solid content = 100: 2.

  Separately, polyvinyl alcohol PVA117 (manufactured by Kuraray Co., Ltd.) was dissolved in ion-exchanged water to obtain a polyvinyl alcohol aqueous solution having a solid content of 9% by mass.

  Thereafter, by the static mixer, the alumina hydrate dispersion obtained above and the previously prepared polyvinyl alcohol aqueous solution have an alumina hydrate solid content: polyvinyl alcohol solid content = 100: 9 on a mass basis. Mixed.

Immediately after this, this mixed solution was applied as a coating solution for the porous ink receiving layer by a die coater at a rate of 30 m / min so that the dry coating amount was 36 g / m ² . At this time, the coating amount when the borate aqueous solution is dried is 1.5 wt% with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content). Thereafter, it was dried at 170 ° C. to form a porous ink receiving layer.

<Formation of the back surface>
Next, a back layer was formed as follows on the undercoat layer on the surface opposite to the surface on which the porous ink receiving layer was provided of the neutral paper substrate. First, Dispersal HP14 (manufactured by Sasol Co., Ltd.) as an alumina hydrate was dispersed in pure water so that the solid content was 18% by mass, and then a dispersion liquid subjected to a centrifugal separation treatment was obtained.

Next, using a static mixer, this dispersion and a polyvinyl alcohol aqueous solution similar to that used for forming the porous ink receiving layer were mixed at a mass ratio of 100: 9 alumina hydrate solid matter to polyvinyl alcohol solid matter. It mixed so that it might become, and the coating liquid for back surface layers was obtained. Thereafter, on the surface of the neutral paper substrate opposite to the surface on which the porous ink receiving layer is provided, immediately on the back surface with a die coater under the conditions of a dry coating amount of 23 g / m ² and 35 m / min. The layer coating solution was applied. And it dried at 170 degreeC and formed the back layer, and finally obtained the recording medium.

[Example 2]
In the coating solution for the porous ink receiving layer, the wet coating amount of the borate aqueous solution in the surface treatment step is 7.2 g / m ² , and the alumina hydrate solid content: polyvinyl alcohol solid content = 100: 7. Except for this, a recording medium was manufactured in the same manner as in Example 1. At this time, the coating amount at the time of drying is 1 wt% with respect to the mass of the entire porous ink receiving layer (solid content) as borate (solid content).

Example 3
A recording medium was prepared in the same manner as in Example 2 except that the coating liquid for the porous ink receiving layer was alumina hydrate solid content: polyvinyl alcohol solid content = 100: 13 on a mass basis. .

Example 4
Except that a 3% by mass boric acid aqueous solution was added to the alumina hydrate dispersion of Example 3 so as to be 0.5 parts by mass in terms of boric acid solid content with respect to the alumina hydrate solid content. A recording medium was produced in the same manner as in Example 3.

[Examples 5 and 6]
A recording medium was prepared in the same manner as in Example 3 except that 25 g (Example 5) and 50 g (Example 6) of 3% by weight boric acid aqueous solution were added to the borate aqueous solution in the surface treatment step. Produced.

Example 7
The wet coating amount of the borate aqueous solution in the surface treatment step is 14.4 g / m ² , and the coating liquid for the porous ink receiving layer is alumina hydrate solid content: polyvinyl alcohol solid content = by mass. 100: 7. Except for this, a recording medium was manufactured in the same manner as in Example 1. At this time, the coating amount at the time of drying is 2 wt% as borate (solid content) with respect to the mass of the entire porous ink receiving layer (solid content).

Example 8
A recording medium was prepared in the same manner as in Example 7 except that the coating liquid for the porous ink receiving layer was changed to alumina hydrate solid content: polyvinyl alcohol solid content = 100: 13 on a mass basis. .

Example 9
A recording medium was prepared in the same manner as in Example 1 except that 3.0 g of dicyandiamide / polyethyleneamine polycondensate (cationic polymer) in terms of solid content was added to the borate aqueous solution in the surface treatment step. did.

Example 10
A recording medium was prepared in the same manner as in Example 8 except that 3.0 g of dicyandiamide / polyethyleneamine polycondensate (cationic polymer) in terms of solid content was added to the borate aqueous solution in the surface treatment step. did.

Example 11
A recording medium was produced in the same manner as in Example 1 except that the light calcium carbonate in the undercoat layer was changed to barium carbonate.

Example 12
The wet coating amount of the borate aqueous solution in the surface treatment step was 7.5 g / m ^2, and the dry coating amount of the porous ink receiving layer was 25 g / m ² . At this time, the coating amount at the time of drying the borate aqueous solution is 1.5 wt% with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content). . Except for this, a recording medium was manufactured in the same manner as in Example 1.

Example 13
The wet coating amount of the borate aqueous solution in the surface treatment step was 13.5 g / m ^2, and the dry coating amount of the porous ink receiving layer was 45 g / m ² . At this time, the coating amount at the time of drying the borate aqueous solution is 1.5 wt% with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content). . Except for this, a recording medium was manufactured in the same manner as in Example 1.

Example 14
The wet coating amount of the borate aqueous solution in the surface treatment step was 6.0 g / m ^2, and the dry coating amount of the porous ink receiving layer was 20 g / m ² . At this time, the coating amount at the time of drying the borate aqueous solution is 1.5 wt% with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content). . Except for this, a recording medium was manufactured in the same manner as in Example 1.

Example 15
Instead of the alumina hydrate-containing porous ink receiving layer formed in Example 1, a silica-containing porous ink receiving layer was formed as follows. Except for this, the recording medium of this example was manufactured in the same manner as in Example 1.

That is, the composition having the following composition was used as a composition for the coating liquid for the porous ink receiving layer.
Cationic colloidal silica having an average particle size of 80 nm (trade name: Snowtex AK-ZL, manufactured by Nissan Chemical Industries, Ltd.) 100 parts by mass Commercially available nonionic acrylic emulsion 3 parts by mass The same polyvinyl as used in Example 1 7 parts by weight of alcohol.

This composition was adjusted so that the solid content concentration was 25%, and was coated on a neutral paper substrate with a roll coater so that the dry coating amount was 36 g / m ^2, and then dried. In other steps, a recording medium was produced in the same manner as in Example 1.

[Comparative Examples 1 and 2]
In the surface treatment step, the wet coating amount of the borate aqueous solution was 3.6 g / m ² and 18.0 g / m ² . At this time, the coating amount at the time of drying the borate aqueous solution is 0.5 wt% with respect to the mass of the entire porous ink receiving layer (solid content) based on the borate (solid content) (comparison). Example 1), 2.5 wt% (Comparative Example 2). Except for this, a recording medium was manufactured in the same manner as in Example 1.

[Comparative Example 3]
In the surface treatment step, after applying the borate aqueous solution, it was immediately dried and solidified at 60 ° C. Except for this, a recording medium was manufactured in the same manner as in Example 1.

[Comparative Example 4]
A recording medium was prepared in the same manner as in Comparative Example 2 except that 3.0 g of dicyandiamide / polyethyleneamine polycondensate (cationic polymer) in terms of solid content was added to the borate aqueous solution in the surface treatment step. Produced.

[Comparative Examples 5 and 6]
In the coating liquid for the porous ink receiving layer, alumina hydrate solid content: polyvinyl alcohol solid content = 100: 5 (Comparative Example 5), alumina hydrate solid content: polyvinyl alcohol solid content = 100 on a mass basis. : A recording medium was prepared in the same manner as in Example 2 except that it was set to 15 (Comparative Example 6).

[Comparative Examples 7 and 8]
In the coating liquid for the porous ink receiving layer, alumina hydrate solid content: polyvinyl alcohol solid content = 100: 5 (Comparative Example 7), alumina hydrate solid content: polyvinyl alcohol solid content = 100 on a mass basis. : A recording medium was prepared in the same manner as in Example 7 except that it was set to 15 (Comparative Example 8).

[Comparative Example 9]
Comparative Example 1 except that 3% by weight boric acid aqueous solution was added to the alumina hydrate dispersion of Comparative Example 1 so as to be 0.5 parts by mass in terms of boric acid solid content relative to the alumina hydrate solid content. A recording medium was produced in the same manner as in Example 1.

[Comparative Example 10]
A recording medium was prepared in the same manner as in Comparative Example 1 except that 50 g of a 3% by mass boric acid aqueous solution was added to the borate aqueous solution in the surface treatment step of Comparative Example 1.
Next, a method for evaluating the recording media produced in the above examples and comparative examples will be described.

<Occurrence of cracks>
After the recording medium was cut to A4 size, five sheets were visually observed and evaluated in four stages. The evaluation criteria were as follows.
A: Good with no occurrence of cracks.
B: Some cracks are observed.
C: The occurrence of cracks is larger than that in the evaluation B, and is observed.
D: Many cracks are observed.

<Peeling of porous ink receiving layer>
A polyester tape (made by 3M) was pasted on the surface of the porous ink receiving layer of the recording medium. Thereafter, the upper surface of the tape was reciprocated twice using a 1 kg weight, and then the polyester tape was forcibly peeled in the 180 ° direction, and the degree of peeling of the porous ink receiving layer attached to the tape was observed and evaluated. The evaluation criteria at this time were as follows.
A: The glue part of the tape peels off or peels off from the neutral paper substrate.
B: Slight peeling of the porous ink receiving layer is observed, but the peeled area is less than 5% of the tape area.
C: Peeling of the porous ink receiving layer is observed, and the peeled area is 5% or more of the tape area.

<Image density>
A 100% duty solid batch of black, cyan, magenta, and yellow was printed on a recording medium using a photo printer (trade name: manufactured by PIXUS iP8600 Canon) using an inkjet method. Thereafter, 25 ° C., 50% R.I. H. After storage in the environment for 3 days, colorimetry was performed using a spectrophotometer / spectrorino (manufactured by Gretag Macbeth Co.). D. The value was evaluated. The evaluation criteria at this time were as follows.
A: O.I. D. The value is 2.20 or more, the gradation reproducibility of the high density portion is very good, and the practicality is high.
B: O.D. D. The value is 2.00 or more and less than 2.20, and the gradation reproducibility of the high density portion is lower than A, but there is no practical problem.
C: O.I. D. The value is 1.90 or more and less than 2.00, the gradation reproducibility of the high density portion is poor, the print density is low, and it cannot be put into practical use.

<Ink absorbability>
Using a photo printer (trade name: manufactured by PIXUS iP8600 Canon) using an ink jet method, a solid color of black, cyan, magenta, yellow, which is a single color on the recording surface of the recording medium, and a secondary color 100% Duty of red (secondary color of 100% yellow and 100% magenta), blue (secondary color of 100% cyan and 100% magenta), green (secondary color of yellow 100% and cyan 100%) Each solid patch was printed. And it evaluated as follows by observation by visual observation of a printing part, and a finger.
A: Immediately after printing, ink does not adhere to fingers in all secondary color images B: Immediately after printing, there is a slight ink overflow in the secondary color image, but it is absorbed in a short time, and all single colors immediately after printing In the image, ink does not adhere to the finger.
C: Immediately after printing, ink adheres to the finger in one of the monochrome images.
Table 1 shows the evaluation results of the recording media prepared in the above examples and comparative examples.

  As can be seen from the results of the examples in Table 1, in the examples, the coating amount of the borate aqueous solution is 1% by mass or more and 2% by mass with respect to the mass of the entire porous ink receiving layer based on the borate. It was as follows. Further, the content of polyvinyl alcohol in the porous ink receiving layer was set to 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the pigment in the porous ink receiving layer. In these examples, “cracks”, “peeling of porous ink receiving layer”, “print density” and “ink absorbability” are all “A” or “B”, while suppressing the occurrence of cracks, It can be seen that a recording medium was obtained in which the porous ink receiving layer was prevented from being peeled off, and further excellent in ink absorbability and image density. In addition, it can be seen that the peeling of the porous ink receiving layer is further suppressed by adding a cationic polymer to the borate aqueous solution.

  On the other hand, as can be seen from the results of Comparative Example 1 in Table 1, when the coating amount of the borate aqueous solution is less than 1% by mass with respect to the total mass of the porous ink receiving layer based on the borate, Although no peeling of the ink receiving layer was observed, cracks occurred. Further, as can be seen from the results of Comparative Example 2 in Table 1, when the coating amount of the borate aqueous solution exceeds 2% by mass with respect to the total mass of the porous ink receiving layer based on the borate, it is clear. Peeling of the porous ink receiving layer was observed.

  Furthermore, as can be seen from the results of Comparative Example 3 in Table 1, when the coating solution for the porous ink receiving layer is applied after drying the borate aqueous solution, cracks are generated in the porous ink receiving layer. I understand that. Further, as can be seen from the results of Comparative Examples 5 and 7, when the content of polyvinyl alcohol in the porous ink receiving layer is less than 7 parts by mass with respect to 100 parts by mass of the pigment in the porous ink receiving layer, cracks occurred. There has occurred. On the other hand, as can be seen from the results of Comparative Examples 6 and 8, when the amount exceeded 13 parts by mass, a decrease in ink absorbency was observed.

It is sectional drawing which shows an example of the manufacturing method of the recording medium of this invention.

Explanation of symbols

1: Neutral paper base material 2: Undercoat layer (pH = 7-8)
3: Support 4: Borate aqueous solution 5: Porous ink receiving layer

Claims (4)

A method for producing a recording medium in which a porous ink receiving layer is provided on a neutral paper substrate provided with an undercoat layer,
Preparing a neutral paper substrate provided with an undercoat layer,
A surface treatment step of coating an aqueous borate solution on the undercoat layer;
While the surface of the undercoat layer coated with the borate aqueous solution is in a wet state, a coating liquid containing a pigment and polyvinyl alcohol is applied onto the undercoat layer and dried to form a porous ink receiving layer. Process,
Have
The undercoat layer contains a pigment containing a salt of a weak acid and a strong base, and a binder, and
The coating amount after drying of the borate aqueous solution is 1% by mass or more and 2% by mass or less based on borate with respect to the mass of the entire porous ink receiving layer,
The content of polyvinyl alcohol in the porous ink receiving layer is 7 parts by mass or more and 13 parts by mass or less with respect to 100 parts by mass of the pigment in the porous ink receiving layer. Manufacturing method.   2. The recording medium according to claim 1, wherein the pigment containing the salt of the weak acid and the strong base is at least one pigment selected from the group consisting of calcium carbonate, barium carbonate, and magnesium carbonate. Method.   The method for manufacturing a recording medium according to claim 1, wherein the borate aqueous solution further contains a cationic polymer. 4. The recording medium according to claim 1, wherein the coating amount of the porous ink receiving layer after drying is 25 g / m ² or more and 45 g / m ² or less. 5. Production method.