JP2011104805A - Recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium showing ink absorption, which can sufficiently meet the requirements of rapid printing by modern inkjet printers and also has excellent image fastness such as ozone resistance or humidity resistance. <P>SOLUTION: The recording medium includes an ink receptive layer formed on a support. The ink receptive layer contains an alumina hydrate, an alkyl sulfonic acid with 1 to 4 carbon atoms and at least either of hydroxylamine or salt thereof represented by formula (1) HO-N(R<SP>1</SP>)(R<SP>2</SP>) defined by a specification. The alkyl sulfonic acid with 1 to 4 carbon atoms accounts for 1.0 to 2.0 mass% to the alumina hydrate, and the total amount of the hydroxylamine and the salt thereof, accounts for 0.2 to 2.0 mass% to the alumina hydrate. In the formula, R<SP>1</SP>and R<SP>2</SP>represent each independently a hydrogen atom, an alkyl group, an alkoxy group, a carbamoyl group, an alkoxycarbonyl group, a vinyl group, a phenyl group or an acyl group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a recording medium, particularly an inkjet recording medium.

  As a recording medium excellent in color developability and glossiness, a void-type ink receiving layer type recording medium having a small amount of a hydrophilic binder and a crosslinking agent and a large amount of fine inorganic particles such as silica and alumina hydrate is known. ing. There is also known a so-called swelling ink-receiving layer type recording medium mainly composed of a hydrophilic polymer and absorbing ink by swelling with ink. Among these, a void-type ink receiving layer type recording medium is preferable because it has excellent ink absorbability.

  As a method for producing a void-type ink receiving layer type recording medium, a method of forming an ink receiving layer on a support by applying and drying the following coating liquid is generally used. The coating liquid is a coating liquid prepared by preparing an aqueous sol such as fine particle silica or alumina hydrate and mixing the aqueous sol and a water-soluble binder such as polyvinyl alcohol.

  Regarding the above-mentioned aqueous sol of inorganic fine particles, Patent Document 1 discloses an alumina sol comprising alumina hydrate and sulfonic acid and having a solid content concentration of 15% by mass to 30% by mass. Further, there is a disclosure that the solid content concentration is 30% by mass or less, the solid content concentration of the alumina sol is stable even when the solid content concentration is high, and the ink absorbability is good. Patent Document 2 discloses a technique for improving light resistance and water resistance by containing at least one of an acid having a sulfonic acid group and a salt thereof in an ink receiving layer. Patent Document 3 discloses a technique for improving light resistance by incorporating hydroxylamine in a support or an ink receiving layer provided on the support.

Japanese Patent No. 3791039 JP 2001-310549 A JP 09-267544 A

  In Patent Document 1, hydrated alumina is peptized with sulfonic acid having 0 carbon atoms, alkylsulfonic acid having 6 or more carbon atoms, or sulfonic acid having a benzene ring, such as benzenesulfonic acid, hexanesulfonic acid, and amidosulfuric acid. Yes. In the study of the present inventors, when alkylsulfonic acid having 5 or more carbon atoms in the alkyl chain, benzenesulfonic acid or p-toluenesulfonic acid is used as peptizing acid, alumina hydrate cannot be peptized, In some cases, it gelled. In addition, the amidosulfuric acid having 0 carbon atoms may have low moisture resistance, and therefore it was concluded that an alkylsulfonic acid having 1 to 4 carbon atoms is preferable. However, if the amount of the alkyl sulfonic acid is large, the ink absorbability may be decreased, and if the amount of the alkyl sulfonic acid is small, the ozone resistance may be decreased. In some cases, it was difficult to achieve a high level of ozone resistance.

  Japanese Patent Application Laid-Open No. H10-228688 discloses the content of containing sulfonic acid in an ink receiving layer mainly containing silica gel. However, the ink receiving layer containing silica gel may have poor gloss and color developability.

  Further, Patent Document 3 discloses a technique for adding hydroxylamine to an ink receiving layer, which is applied to a swelling ink receiving layer mainly composed of gelatin, and has very poor ink absorbability. There was a case.

  The present invention has been made in view of the above circumstances. An object of the present invention is to provide a recording medium having ink absorptivity that can sufficiently withstand high-speed printing of recent ink jet printers and excellent in image fastness such as ozone resistance and moisture resistance.

  According to the present invention, there is provided a recording medium having an ink receiving layer on a support, wherein the ink receiving layer comprises an alumina hydrate, an alkyl sulfonic acid having 1 to 4 carbon atoms, and the following general formula (1): And at least one of hydroxylamine and a salt thereof represented, and the alkylsulfonic acid having 1 to 4 carbon atoms is 1.0% by mass to 2.0% by mass with respect to the alumina hydrate. The total amount of the hydroxylamine and its salt is 0.2% by mass or more and 2.0% by mass or less with respect to the alumina hydrate.

General formula (1) HO-N (R ¹ ) (R ² )
(Wherein R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a carbamoyl group, an alkoxycarbonyl group, a vinyl group, a phenyl group or an acyl group.)

  According to the present invention, it is possible to provide a recording medium having ink absorbability sufficient to withstand high-speed printing of recent ink jet printers and excellent in image fastness such as ozone resistance and moisture resistance.

  The recording medium of the present invention will be described below based on preferred embodiments thereof.

<Recording medium>
The recording medium of the present invention can be formed from a support and an ink receiving layer containing alumina hydrate provided on the support. The recording medium of the present invention can be used as an ink jet recording medium.

[Ink receiving layer]
The ink receiving layer used in the present invention contains an alumina hydrate, an alkyl sulfonic acid having 1 to 4 carbon atoms, and at least one of hydroxylamine represented by the general formula (1) and a salt thereof. The ink receiving layer contains an alkyl sulfonic acid having 1 to 4 carbon atoms in an amount of 1.0% by mass to 2.0% by mass with respect to the alumina hydrate, and a hydroxylamine represented by the general formula (1) and its The total amount of salt is 0.2% by mass or more and 2.0% by mass or less with respect to the alumina hydrate. Further, the ink receiving layer can be obtained by coating the support with a coating liquid in which an alumina hydrate sol and a polyvinyl alcohol aqueous solution as a binder are mixed. The ink receiving layer may be a solidified product of the coating liquid.

  The content of alumina hydrate in the ink receiving layer is preferably 70% by mass or more and 98% by mass or less. When the content is 70% by mass or more, the ink absorbability can be excellently prevented from being lowered.

  The components contained in the ink receiving layer used in the present invention and the physical properties thereof will be described below.

(Alumina hydrate)
In the present invention, alumina hydrate is used as a pigment for forming the ink receiving layer.

By using alumina hydrate, it is possible to obtain a recording medium having high glossiness, ink absorption, and good color development. As this alumina hydrate, what is represented by the following general formula (X) can be used suitably, for example.
Al ₂ O _3-n (OH) _2n · mH ₂ O ... (X)
(In the above formula, n represents any one of 0, 1, 2, and 3, and m represents a number of 0 to 10, preferably 0 to 5, provided that 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 a crystal lattice, m can take an integer or a non-integer value. Further, when the alumina hydrate is heated, m may be zero.

  As the crystal structure of the alumina hydrate, amorphous, kibsite type, and boehmite type are known according to the heat treatment temperature, and any of these crystal structures can be used.

  Among these, a preferred alumina hydrate is an alumina hydrate that exhibits a boehmite structure or an amorphous state by analysis by an X-ray diffraction method. Specific examples include alumina hydrates described in JP-A-7-232473, JP-A-8-132731, JP-A-9-66664, JP-A-9-76628, and the like. . Furthermore, examples of the alumina hydrate include commercially available Dispersal HP14 (trade name, manufactured by Sasol Corporation). Two or more kinds of alumina hydrates may be used in combination.

As the alumina hydrate used in the present invention, it is preferable to use an alumina hydrate having an average pore radius of 7.0 nm or more and 10 nm or less when the ink receiving layer is formed. More preferably, the average pore radius of the entire ink receiving layer when forming the ink receiving layer is from 8.0 nm to 10 nm. When the average pore radius of the entire ink receiving layer is 7.0 nm or more and 10 nm or less, it is possible to exhibit excellent ink absorbability and color developability. Further, if the average pore radius of the entire ink receiving layer is 7.0 nm or more, it is excellently prevented that the ink absorbability is lowered, and the amount of the binder with respect to the alumina hydrate is adjusted as necessary. Excellent ink absorbability can be obtained. Further, if the average pore radius of the entire ink receiving layer is 10 nm or less, it is possible to excellently prevent an increase in the haze of the ink receiving layer, and particularly good color developability can be obtained.
The pore volume of the entire ink receiving layer is preferably 0.50 ml / g or more. If the total pore volume is 0.50 ml / g or more, it is excellently prevented that the ink absorbability of the entire ink receiving layer is lowered, and the amount of the binder with respect to the alumina hydrate is adjusted as necessary. Excellent ink absorbability can be obtained.

  Furthermore, it is preferable that pores having a pore radius of 25 nm or more do not exist in the pores of the ink receiving layer. In other words, all the pores in the ink receiving layer used in the present invention preferably have a pore radius of less than 25 nm. When there are no pores having a pore radius of 25 nm or more, it is possible to excellently prevent the haze of the ink receiving layer from being increased, and particularly good color developability can be obtained.

  The average pore radius, total pore volume, and pore radius are the BJH (Barrett-Joyner-Halenda) method based on the adsorption / desorption isotherm of nitrogen gas measured on the recording medium by the nitrogen adsorption / desorption method. This is a value obtained using. In particular, the average pore diameter is a value obtained by calculation from the total pore volume and specific surface area measured during nitrogen gas desorption.

  Note that when the ink-absorbing recording medium is measured by the nitrogen adsorption / desorption method, the measurement is also performed on portions other than the ink receiving layer. However, components other than the ink receiving layer (for example, the pulp layer of the substrate, the resin coating layer, etc.) do not have pores of 1 nm to 100 nm, which is a range that can be generally measured by the nitrogen adsorption / desorption method. For this reason, when the entire ink-absorbing recording medium is measured by the nitrogen adsorption / desorption method, it is considered that the average pore diameter of the ink receiving layer is measured. This can also be understood from the fact that the resin-coated paper has no pores of 1 nm or more and 100 nm or less when the pore distribution is measured by the nitrogen adsorption / desorption method.

In order to obtain the average pore radius (7.0 nm or more and 10 nm or less) at the time of forming the ink receiving layer as described above, the BET specific surface area measured by the BET method is 100 m ² / g or more and 200 m ² / g. It is preferable to use the following alumina hydrate. More preferably, an alumina hydrate having a BET specific surface area of 125 m ² / g or more and 175 m ² / g or less is used.

  The BET method is a method for measuring the surface area of a powder by a 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 an adsorption isotherm. In this BET method, nitrogen gas is usually used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. At this time, the most prominent expression representing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller equation, which is called the BET equation and is widely used for determining the specific surface area. In the BET method, the specific surface area is obtained by calculating the amount of adsorption based on the BET formula and multiplying the area occupied by one adsorbed molecule on the surface. In the BET method, in the nitrogen adsorption / desorption method, the relationship between the adsorption amounts at a certain relative pressure is measured at several points, and the specific surface area is derived by obtaining the slope and intercept of the plot by the least square method. For this reason, in order to increase the accuracy of measurement, it is preferable to measure at least 5 points, and more preferably 10 points or more, between the relative pressure and the amount of adsorption.

  Further, the preferred shape of the alumina hydrate is preferably a flat plate having an average aspect ratio of 3.0 or more and 10 or less and an aspect ratio of the flat plate surface of 0.60 or more and 1.0 or less. The aspect ratio can be obtained by the method described in Japanese Patent Publication No. 5-16015. That is, the aspect ratio is expressed as the ratio of the “diameter” to the “thickness” of the particles. Here, the “diameter” indicates a diameter of a circle (an equivalent circle diameter) having an area equal to the projected area of the particles when the alumina hydrate is observed with a microscope or an electron microscope. Similarly to the aspect ratio, the aspect ratio of the flat surface indicates the ratio of the diameter indicating the minimum value to the diameter indicating the maximum value of the flat surface when the particles are observed with a microscope.

  When the alumina hydrate having an aspect ratio of 3.0 or more and 10 or less is used, it is possible to excellently prevent the pore distribution range of the formed ink receiving layer from being narrowed. For this reason, it becomes possible to produce the alumina hydrate with the same particle diameter. Similarly, when alumina hydrate having an aspect ratio of 0.60 or more and 1.0 or less is used, the pore diameter distribution of the ink receiving layer can be excellently prevented.

  It is known that alumina hydrate has ciliary and non-ciliated shapes. According to the knowledge of the present inventors, even with the same alumina hydrate, the plate-like alumina hydrate has better dispersibility than the ciliated alumina hydrate. In addition, ciliary alumina hydrate tends to be oriented parallel to the surface of the support during coating, and the pores of the ink receiving layer formed may be small. Absorbency may be reduced. On the other hand, the plate-like alumina hydrate has a small tendency to be oriented parallel to the surface of the support during coating, and is particularly good for the pore size and ink absorbability of the ink receiving layer to be formed. affect. For this reason, it is preferable to use a plate-like alumina hydrate.

(Alkyl sulfonic acid)
Peptizing acid that stably disperses alumina hydrate suitably used in the present invention as a sol is an alkylsulfonic acid having 1 to 4 carbon atoms. When the peptizing acid is an alkylsulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid having an alkyl chain with 5 or more carbon atoms, the color stability is lowered and the image density is also lowered. In the case of alkylsulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid having 5 or more carbon atoms, since the hydrophobicity is strong, the hydrophobicity of the alumina surface becomes strong, the dye fixing speed on the alumina surface becomes slow, and the color is stable. And the image density is considered to decrease.

  In addition, when an alkyl sulfonic acid having 5 or more alkyl chain carbon atoms or a sulfonic acid having a benzene ring is used alone as a peptizing acid for alumina hydrate, sufficient dispersibility cannot be obtained. Easy to stick. Further, it was found that the production suitability was low, and the alumina hydrate aggregated to cause a decrease in image density. For this reason, also from a viewpoint of production suitability, the alkylsulfonic acid used in the present invention has 1 to 4 carbon atoms.

The alkylsulfonic acid (RSO ₃ H) used in the present invention has a sulfonic acid group (SO ₃ H) and an alkyl group (R) which is a substituent of the sulfonic acid group.

  The alkyl sulfonic acid is preferably a monobasic acid having only a sulfonic acid group as a solubilizing group, and the alkyl group is a linear or branched unsubstituted alkyl group having no solubilizing group in terms of improving moisture resistance. It is preferable that Examples of the solubilizing group include a hydroxyl group, a sulfonic acid group, and a carboxylic acid group.

  On the other hand, alkylsulfonic acids having only sulfonic acid groups as solubilizing groups do not have solubilizing groups that do not participate in the peptization of alumina, and therefore have a low tendency to retain moisture in the porous layer, resulting in extreme moisture resistance. Can be excellently prevented. In order to improve moisture resistance and color stability at the same time, the alkyl sulfonic acid is preferably a monobasic acid and a linear or branched unsubstituted alkyl group having 1 to 4 carbon atoms in the alkyl chain. . Preferred alkyl sulfonic acids include, for example, methane sulfonic acid, ethane sulfonic acid, isopropane sulfonic acid, n-propane sulfonic acid, n-butane sulfonic acid, I-butane sulfonic acid, and t-butane sulfonic acid. More preferred are methanesulfonic acid, ethanesulfonic acid, isopropanesulfonic acid and n-propanesulfonic acid having 1 to 3 carbon atoms. Among these, methanesulfonic acid is more preferable.

  The amount of alkylsulfonic acid having 1 to 4 carbon atoms in the alkyl chain is 1.0% by mass or more and 2.0% by mass or less with respect to the alumina hydrate. If it is less than 1.0% by mass, the ozone resistance is lowered, and if it is more than 2.0% by mass, the ink absorbability is lowered. Two or more alkyl sulfonic acids may be used in combination.

(Hydroxylamine and hydroxylamine salts)
The hydroxylamine and its salt used in the present invention will be described. The hydroxylamine compound used in the present invention is represented by the following general formula (1).
General formula (1) HO-N (R ¹ ) (R ² )
(In the formula, R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a carbamoyl group, an alkoxycarbonyl group, a vinyl group, a phenyl group, or an acyl group.)
The alkyl group represented by R ¹ and R ² in the general formula (1) is linear, branched or cyclic having 1 to 18 carbon atoms (substituent atoms and carbon atoms not containing a substituent). An alkyl group is preferred. These alkyl groups may have a substituent atom and a substituent, respectively. Substituent atoms and substituents include, for example, alkoxy groups, aryl groups, heterocyclic groups, alkoxycarbonyl groups, carbamoyl groups, acyl groups, alkenyl groups, hydroxyl groups, halogen atoms, cyano groups, nitro groups, amino groups, sulfo groups, Examples thereof include a carboxy group, a sulfamoyl group, a ureido group, a phosphono group, and a phosphine group. The aryl group and alkenyl group as a substituent preferably have 2 to 18 carbon atoms.
The alkoxy group represented by R ¹ and R ² in the general formula (1) is a linear or branched alkoxy group having 1 to 8 carbon atoms (the number of carbon atoms not including a substituent). preferable. These alkoxy groups may have a substituent. Examples of the substituent include the same substituents as those in the alkyl group.
The carbamoyl group represented by R ¹ and R ² in the general formula (1) is, for example, a methylcarbamoyl group, an ethylcarbamoyl group, or the like. These carbamoyl groups may have a substituent. Examples of the substituent include the same substituents as those in the alkyl group.
The alkoxycarbonyl group represented by R ¹ and R ² in the general formula (1) is, for example, a methoxycarbonyl group, an ethoxycarbonyl group, or the like. These alkoxycarbonyl groups may have a substituent. Examples of the substituent include the same substituents as those in the alkyl group.

Examples of the acyl group represented by R ¹ and R ² in the general formula (1) include an acetyl group, a propanoyl group, and a benzoyl group. These acyl groups may have a substituent. Examples of the substituent include the same substituents as those in the alkyl group.

  Such a hydroxylamine compound is considered to exhibit a function as a reducing agent and to exhibit an antioxidant action against an oxidizing gas such as ozone.

  Specific examples of the hydroxylamine represented by the general formula (1) include hydroxylamine, N, N-diethylhydroxylamine, N-isopropylhydroxylamine, N- (tert-butyl) hydroxylamine, N-methylhydroxylamine, N -Ethyl-N-methylhydroxylamine, N-ethyl-N-propylhydroxylamine, N, N-dipropylhydroxylamine, N-methyl-N-butylhydroxylamine, N-isopropyl-N-ethylsulfonic acid hydroxylamine, N, N-dibenzylhydroxylamine, benzohydroxamic acid, N-carbobenzoxyhydroxylamine, salicylhydroxylamine, N-benzoyl-N-phenylhydroxylamine, etc. may be mentioned, and these may be used alone or in combination. There.

Since the hydroxylamine compound can be stably handled in the form of a salt, it is preferably added as a hydroxylamine salt in the ink receiving layer. Examples of the hydroxylamine salt include hydrochloride, sulfate, sulfonate, sulfite, phosphate, hypochlorite, acetate, propionate and the like. Among these, methanesulfonate is more preferable because of its high ozone resistance effect. In addition to the methanesulfonic acid added as the peptizing acid (alkyl sulfonic acid) of alumina hydrate during the preparation of the alumina hydrate sol, hydroxylamine methanesulfonate contains methanesulfonic acid for the amount of hydroxylamine salt formed. It can be prepared by adding in excess. Thus, when the acid used for the hydroxylamine salt is an alkylsulfonic acid having 1 to 4 carbon atoms, the amount of the alkylsulfonic acid and the hydroxylamine and its salt in calculating the mass ratio with respect to the alumina hydrate in the ink receiving layer The total amount is as follows. Alkyl sulfonic acid amount = total alkyl sulfonic acid amount−the amount of alkyl sulfonic acid required to neutralize hydroxylamine. Total content of hydroxylamine and its salt = total amount of hydroxylamine and its salt before neutralization with alkylsulfonic acid + the amount of alkylsulfonic acid required to neutralize hydroxylamine.
When the ink receiving layer was analyzed, the alkyl sulfonic acid having 1 to 4 carbon atoms was A mass% and the acid other than the alkyl sulfonic acid having 1 to 4 carbon atoms (“other acids”) with respect to the alumina hydrate. ”) Is B mass%, and hydroxylamine is C mass%. At that time, the alkylsulfonic acid content (relative ratio) with respect to the alumina hydrate in the ink receiving layer, and the total content (relative ratio) of hydroxylamine and its salt with respect to the alumina hydrate are as follows.
1) When A ≦ 2.0, all A are included in the alkylsulfonic acid content. On the other hand, when A> 2.0, 2.0 mass% of A is included in the alkylsulfonic acid content. For the remaining alkylsulfonic acid (A-2.0) mass%, follow 4).
2) Hydroxylamine C% by mass is included in the total content of hydroxylamine and salts thereof.
3) Consider the amount of other acids (corresponding to chemical equivalents) that form a salt without excess or deficiency with C% by weight of hydroxylamine. The amount of the other acid expressed in mass% with respect to the alumina hydrate of the ink receiving layer is referred to as D. When B ≦ D, all B is included in the total content of the hydroxylamine and its salt. On the other hand, when B> D, only D mass% of B is included in the total content of the hydroxylamine and its salt.
4) When B ≧ D, all hydroxylamine C mass% forms salts with other acids, so the remaining alkylsulfonic acid (A-2.0) mass% is included in the alkylsulfonic acid content. . On the other hand, in the case of B <D, the amount of alkylsulfonic acid having 1 to 4 carbon atoms, which is the amount of acid equal to the other acid (D-B) mass% (for example, the valences of these acids are equal The same number of moles). The amount of the alkyl sulfonic acid expressed by mass% with respect to the alumina hydrate of the ink receiving layer is referred to as E. In the case of (A-2.0) ≦ E, all (A-2.0) mass% is included in the total content of the hydroxylamine and its salt. On the other hand, in the case of (A-2.0)> E, E mass% of (A-2.0) mass% is included in the total content of hydroxylamine and its salt, and other excess Alkylsulfonic acid ((A-2.0) -E) mass% is included in the alkylsulfonic acid content.

  For example, a hydroxylamine salt can be obtained by determining the number of moles of hydroxylamine used in the present invention, mixing a monovalent acid having the same number of moles (for example, methanesulfonic acid), and neutralizing. In view of preventing aggregation of the alumina sol, the acid used for the hydroxylamine salt is more preferably a monovalent acid than a divalent or higher acid (for example, sulfuric acid). In addition, the hydroxylamine salt used in the present invention may be one commercially available in the form of hydrochloride or the like.

  The total amount of hydroxylamine represented by the general formula (1) and a salt thereof is contained in the ink receiving layer in an amount of 0.2% by mass to 2.0% by mass with respect to the alumina hydrate. In addition, although it described as a total amount, when only one of hydroxylamine or its salt is used, it is naturally one amount. If it is less than 0.2% by mass, the effects of ozone resistance and light resistance are small. If it exceeds 2.0% by mass, the stability of the alumina sol decreases, which is not preferable. Furthermore, 0.5 mass% or more and 1.5 mass% or less are preferable.

  Moreover, it is preferable that the solubility with respect to the water of the hydroxylamine represented by General formula (1) and its salt is 5 mass% or more at room temperature. If the solubility is 5% by mass or more, the stability of the alumina sol can be excellently prevented from being lowered. Furthermore, the solubility is more preferably 10% by mass or more.

(binder)
The ink receiving layer used in the present invention can contain a binder. Any binder can be used without particular limitation as long as it is a material capable of binding the above-mentioned alumina hydrate to form a film and does not impair the effects of the present invention.

  Examples of the binder include the following. Starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch. Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose. Casein, gelatin, soy protein, polyvinyl alcohol and derivatives thereof. Conjugated polymer latex such as polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer. Acrylic polymer latex such as acrylic ester and methacrylic ester polymers. Vinyl polymer latex such as ethylene-vinyl acetate copolymer. Functional group-modified polymer latex with functional group-containing monomers such as carboxyl groups of the above various polymers. What cationized the said various polymers using the cationic group, What cationized the surface of the said various polymers using the cationic surfactant. A polymer obtained by polymerizing the above-mentioned various polymers under cationic polyvinyl alcohol and distributing the polyvinyl alcohol on the surface of the polymer. A polymer obtained by polymerizing the above-mentioned various polymers in a suspension sol of cationic colloidal particles and distributing the cationic colloidal particles on the surface of the polymer. Aqueous binders such as thermosetting synthetic resins such as melamine resin and urea resin. Polymers and copolymer resins of methacrylic acid esters and acrylic acid esters such as polymethyl methacrylate. Synthetic resin binders such as polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin.

  The above binders can be used alone or in combination of two or more. Among them, the most preferably used binder is polyvinyl alcohol. This polyvinyl alcohol can be synthesized, for example, by hydrolyzing polyvinyl acetate. As the polyvinyl alcohol, those having a weight average polymerization degree of 1500 or more are preferably used, and those having a weight average polymerization degree of 2000 or more and 5000 or less are more preferable. The degree of saponification is preferably from 80 mol% to 100 mol%, more preferably from 85 mol% to 100 mol%. The saponification degree here is a value measured by the method of JIS-K6726. Chemically, it is the ratio of the number of moles of hydroxyl groups produced by the saponification reaction when polyvinyl alcohol is obtained by saponifying polyvinyl acetate.

  It is preferable that the usage-amount of polyvinyl alcohol (PVA) is 7 to 12 mass% with respect to an alumina hydrate. When the content is 7% by mass or more, a particularly strong coating film is formed. When the content is 12% by mass or less, gelation is excellently suppressed, and adverse effects such as deterioration of coating suitability can be excellently prevented. In the best mode of the present invention, the amount of polyvinyl alcohol used is 8% by mass or more and 9% by mass or less based on the alumina hydrate.

  The polyvinyl alcohol is preferably used in the form of an aqueous solution, and the dry solid content concentration of the aqueous polyvinyl alcohol solution is preferably 3% by mass or more and 20% by mass or less. If it is 3 mass% or more and 20 mass% or less, it can suppress favorably that the density | concentration of a coating liquid falls excessively and a drying rate falls significantly. Further, it is possible to satisfactorily suppress the coating liquid viscosity from being significantly increased due to an excessive increase in the concentration of the coating liquid and the smoothness of the coated surface being impaired.

(Coating fluid)
The coating liquid that can be used in the present invention can contain an alumina hydrate sol and an aqueous polyvinyl alcohol solution. The coating solution may be a mixed solution of an alumina hydrate sol and a polyvinyl alcohol aqueous solution.

(Alumina hydrate sol)
The alumina hydrate sol that can be used in the present invention will be described.

  The alumina hydrate sol includes the alumina hydrate, the alkylsulfonic acid having 1 to 4 carbon atoms, at least one of hydroxylamine represented by the general formula (1) and a salt thereof, water, It is preferable to contain. The alkyl sulfonic acid having 1 to 4 carbon atoms in the alumina hydrate sol is 1.0% by mass or more and 2.0% by mass or less with respect to the alumina hydrate in the alumina hydrate sol. It is preferable. Furthermore, the total amount of the hydroxylamine represented by the general formula (1) and the salt thereof in the alumina hydrate sol is 0.2% by mass or more and 2% by mass or more with respect to the alumina hydrate in the alumina hydrate sol. It is preferable that it is 0.0 mass% or less.

  Moreover, it is preferable that the content rate of the alumina hydrate in an alumina hydrate sol is 70 mass% or more in the total solid content contained in an alumina hydrate sol. When the content is 70% by mass or more, the ink absorbability can be excellently prevented from being lowered.

  The feature of this alumina hydrate sol is that it can maintain a stable state with a low viscosity even when the solid content concentration of the alumina hydrate sol is higher than 30% by mass. If the solid content concentration of the alumina hydrate sol is higher than 30% by mass, the solid content concentration of the coating liquid mixed with the binder component and the cross-linking agent component can be increased, so that a high concentration coating liquid can be applied. The work speed can be particularly increased. Therefore, when the solid content concentration is higher than 30% by mass, productivity can be particularly improved, which is preferable. The solid content concentration of the alumina hydrate sol is more preferably 33% by mass or more.

(Additive)
In the recording medium of the present invention, a cross-linking component of a binder can be contained in the ink receiving layer as necessary. Specific examples of the crosslinking component include boric acid and borates. By adding at least one of boric acid and borate, the occurrence of cracks in the ink receiving layer can be excellently prevented. In this case, examples of boric acid that can be used include not only orthoboric acid (H ₃ BO ₃ ) but also metaboric acid and hypoboric acid. The borate is preferably a water-soluble salt of boric acid. Specific examples include the following alkaline earth metal salts of boric acid.

For example, sodium salt of boric acid (Na ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ O, etc.), potassium salt of boric acid (K ₂ B ₄ O ₇ · 5H ₂ O, KBO ₂ etc.), etc. And alkali metal salts of boric acid, ammonium salts of boric acid (NH ₄ B ₄ O ₉ .3H ₂ O, NH ₄ BO _2, etc.), magnesium salts of boric acid and calcium salts. Among these boric acids and borates, it is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating solution and the effect of suppressing the occurrence of cracks. The amount of boric acid and borate used is preferably such that the solid content of boric acid is 5% by mass or more and 50% by mass or less with respect to the binder in the ink receiving layer. If it is 50 mass% or less, it can prevent excellent that the temporal stability of a coating liquid falls. If it is 5 mass% or more, the effect as a crosslinking agent will be excellent.

  Other additives include pH adjusters, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, surfactants, release agents, penetrants, colored pigments, colored dyes, An optical brightener, an ultraviolet absorber, an antioxidant, an antiseptic, an antifungal agent, a water resistant agent, a dye fixing agent, a curing agent, a weather resistant material, and the like may be added as necessary.

[Support]
As the support used in the present invention, for example, papers such as cast-coated paper, baryta paper, resin-coated paper (resin-coated paper coated on both surfaces with a resin such as polyolefin), and those made of films are preferably used. Is done. As this film, for example, a transparent thermoplastic resin film such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate can be used.

  In addition to this, non-sized paper or coated paper, which is appropriately sized paper, or a sheet-like substance (such as synthetic paper) made of a film made opaque by filling with inorganic substances or fine foaming can be used. A sheet made of glass or metal may be used. Furthermore, in order to improve the adhesive strength between the support and the ink receiving layer, the surface of the support can be subjected to corona discharge treatment or various undercoat treatments. Among the above-mentioned supports, it is preferable to use resin-coated paper from the viewpoint of gloss after the ink receiving layer is formed.

[Coating method of coating liquid]
For coating of the coating liquid for forming the ink receiving layer, for example, various curtain coaters, coaters using an extrusion method, and coaters using a slide hopper method are preferably used. Among these, a slide curtain coating apparatus can be preferably used. In addition, at the time of coating, for the purpose of adjusting the viscosity of the coating solution, the coating solution may be heated, or the coater head can be heated. For drying the coating liquid after coating, 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, or the like can be used. In addition, a dryer using infrared rays, a heated dryer, a microwave, or the like can be appropriately selected and used.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these examples. In Examples and Comparative Examples, ink jet recording media were produced.

<Production of support>
A support was prepared under the following conditions. First, a paper stock having the following composition was prepared with water so that the solid content concentration was 3% by mass.

(Paper composition)
-100 parts by weight of pulp (80 ml of hardwood bleached kraft pulp (LBKP) having a freeness of 450 ml CSF (Canadian Standard Freeness)
And 20 parts by mass of bleached kraft pulp (NBKP) having a freeness of 480 ml CSF),
-0.60 parts by mass of cationized starch,
・ 10 parts by weight of heavy calcium carbonate,
・ 15 parts by weight of light calcium carbonate,
-Alkyl ketene dimer 0.10 parts by mass,
-Cationic polyacrylamide 0.03 mass part.

Next, this stock was made with a long paper machine, subjected to a three-stage wet press, and then dried with a multi-cylinder dryer. Thereafter, the starch starch aqueous solution was impregnated with a size press apparatus so that the coating amount was 1.0 g / m ² and dried. Thereafter, machine calendar finishing was performed to obtain a base paper A having a basis weight of 170 g / m ² , a Steecht size of 100 seconds, an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN. On the base paper A, 25 g / m ^{2 of a} resin composition composed of low density polyethylene (70 parts by mass), high density polyethylene (20 parts by mass), and titanium oxide (10 parts by mass) was applied. Furthermore, a resin-coated support is formed by applying 25 g / m ² of a resin composition comprising high-density polyethylene (50 parts by mass) and low-density polyethylene (50 parts by mass) to the back surface of the base paper A. 1 was obtained.

<Preparation of alumina hydrate sol>
(Alumina hydrate sol 1):
In 207 parts by mass of pure water, 100 parts by mass of Dispersal HP14 (trade name, manufactured by Sasol Corporation) as an alumina hydrate, and an alkyl sulfonic acid having 1 to 4 carbon atoms, methanesulfonic acid to alumina hydrate On the other hand, 1.5% by mass and, as hydroxylamine, hydroxylamine hydrochloride is mixed with 0.5% by mass with respect to alumina hydrate, and stirred with a homomixer for 30 minutes to produce alumina hydrate sol 1. did. When the solid content concentration of the alumina hydrate sol 1 was measured, it was 33.0% by mass and its viscosity was 280 mPa · s. The solid content concentration was measured by weighing 5 g of alumina hydrate sol and measuring at 120 ° C. using an infrared moisture meter FD-620 (trade name, manufactured by Kett Science Laboratory). The viscosity was measured using a B-type viscometer RB-80L (trade name, manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. and 30 rpm.

(Alumina hydrate sol 2):
Alumina hydrate sol 2 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that hydroxylamine hydrochloride was changed to N-methylhydroxylamine hydrochloride. When the solid content concentration of the alumina hydrate sol 2 was measured, it was 33.0% by mass and its viscosity was 170 mPa · s.

(Alumina hydrate sol 3):
Alumina hydrate sol 3 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that hydroxylamine hydrochloride was changed to N, N-dibenzylhydroxylamine. When the solid content concentration of the alumina hydrate sol 3 was measured, it was 33.0% by mass and its viscosity was 150 mPa · s.

(Alumina hydrate sol 4):
The same composition and the same conditions as the alumina hydrate sol 1 except that the amount of methanesulfonic acid was changed to 2.0 mass% with respect to the alumina hydrate and the hydroxylamine hydrochloride was changed to N, N-diethylhydroxylamine. To obtain an alumina hydrate sol 4. When the solid content concentration of the alumina hydrate sol 4 was measured, it was 33.0% by mass and its viscosity was 380 mPa · s.

(Alumina Hydrate Sol 5):
Alumina hydrate sol 5 was prepared by dispersing the hydroxylamine hydrochloride in the same composition and under the same conditions as the alumina hydrate sol 1 except that the amount of hydroxylamine hydrochloride was 1.8% by mass with respect to the alumina hydrate. . When the solid content concentration of the alumina hydrate sol 5 was measured, it was 33.0% by mass and its viscosity was 1200 mPa · s.

(Alumina Hydrate Sol 6):
Alumina hydrate sol 6 was prepared by dispersing the hydroxylamine hydrochloride in the same composition and under the same conditions as the alumina hydrate sol 1 except that the amount of hydroxylamine hydrochloride was 0.2% by mass with respect to the alumina hydrate. . When the solid content concentration of the alumina hydrate sol 6 was measured, it was 33.0% by mass and its viscosity was 450 mPa · s.

(Alumina Hydrate Sol 7):
Alumina hydrate sol 7 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that the amount of methanesulfonic acid was 2.0 mass% with respect to the alumina hydrate. . When the solid content concentration of the alumina hydrate sol 7 was measured, it was 33.0% by mass and its viscosity was 88 mPa · s.

(Alumina hydrate sol 8):
Alumina hydrate sol 8 was prepared by dispersing in the same composition and conditions as alumina hydrate sol 1 except that the amount of methanesulfonic acid was 1.0 mass% with respect to the alumina hydrate. . When the solid content concentration of the alumina hydrate sol 8 was measured, it was 33.0% by mass and its viscosity was 2300 mPa · s.

(Alumina hydrate sol 9):
An alumina hydrate sol 9 was prepared by dispersing under the same composition and conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to ethanesulfonic acid. When the solid content concentration of the alumina hydrate sol 9 was measured, it was 33.0% by mass and its viscosity was 380 mPa · s.

(Alumina hydrate sol 10):
An alumina hydrate sol 10 was prepared by dispersing under the same composition and conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to propanesulfonic acid. When the solid content concentration of the alumina hydrate sol 10 was measured, it was 33.0% by mass and its viscosity was 460 mPa · s.

(Alumina hydrate sol 11):
An alumina hydrate sol 11 was prepared by dispersing under the same composition and conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to sulfuric acid. When the solid content concentration of the alumina hydrate sol 11 was measured and found to be 33.0% by mass, the entire liquid of the alumina hydrate sol 11 was gelled.

(Alumina hydrate sol 12):
An alumina hydrate sol 12 was prepared by dispersing in the same composition and conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to hydrochloric acid. When the solid content concentration of the alumina hydrate sol 12 was measured, it was 33.0% by mass and its viscosity was 170 mPa · s.

(Alumina hydrate sol 13):
Dispersed under the same composition and the same conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to acetic acid and the amount of acetic acid was 2.0% by mass with respect to the alumina hydrate. A Japanese sol 13 was prepared. When the solid content concentration of the alumina hydrate sol 13 was measured, it was 33.0% by mass and its viscosity was 300 mPa · s.

(Alumina hydrate sol 14):
Dispersed under the same composition and the same conditions as the alumina hydrate sol 1 except that methanesulfonic acid was changed to lactic acid and the amount of lactic acid was 2.0% by mass with respect to the alumina hydrate. A Japanese sol 14 was prepared. When the solid content concentration of the alumina hydrate sol 14 was measured, it was 33.0% by mass and its viscosity was 340 mPa · s.

(Alumina hydrate sol 15):
Alumina hydrate sol 15 was prepared by dispersing in the same composition and conditions as alumina hydrate sol 1 except that methanesulfonic acid was changed to amidosulfuric acid. When the solid content concentration of the alumina hydrate sol 15 was measured, it was 33.0% by mass and its viscosity was 240 mPa · s.

(Alumina hydrate sol 16):
Alumina hydrate sol 16 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that the amount of methanesulfonic acid was 2.5% by mass with respect to alumina hydrate. . When the solid content concentration of the alumina hydrate sol 16 was measured, it was 33.0% by mass and its viscosity was 52 mPa · s.

(Alumina Hydrate Sol 17):
Alumina hydrate sol 17 was prepared by dispersing in the same composition and conditions as alumina hydrate sol 1 except that the amount of methanesulfonic acid was 0.8% by mass with respect to alumina hydrate. . When the solid content concentration of the alumina hydrate sol 17 was measured and found to be 33.0% by mass, the entire liquid of the alumina hydrate sol 17 was gelled.

(Alumina Hydrate Sol 18):
Alumina hydrate sol 18 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that the amount of hydroxylamine hydrochloride was 2.5% by mass with respect to the alumina hydrate. . When the solid content concentration of the alumina hydrate sol 18 was measured and found to be 33.0% by mass, the entire liquid of the alumina hydrate sol 18 was gelled.

(Alumina Hydrate Sol 19):
An alumina hydrate sol 19 was prepared by dispersing under the same composition and conditions as the alumina hydrate sol 1 except that hydroxylamine hydrochloride was not added. When the solid content concentration of the alumina hydrate sol 19 was measured and found to be 33.0% by mass, the entire liquid of the alumina hydrate sol 19 was gelled.

(Alumina hydrate sol 20):
An alumina hydrate sol 20 was prepared by dispersing under the same composition and conditions as the alumina hydrate sol 1 except that hydroxylamine hydrochloride was changed to ammonium chloride. When the solid content concentration of the alumina hydrate sol 20 was measured, it was 33.0% by mass and its viscosity was 290 mPa · s.

(Alumina Hydrate Sol 21):
Alumina hydrate sol 21 was prepared by dispersing under the same composition and conditions as alumina hydrate sol 1 except that hydroxylamine hydrochloride was changed to sodium methanesulfonate. When the solid content concentration of the alumina hydrate sol 21 was measured, it was 33.0% by mass and its viscosity was 150 mPa · s.

<Formation of ink receiving layer>
Example 1
Polyvinyl alcohol PVA235 (trade name, manufactured by Kuraray Co., Ltd., average polymerization degree: 3500, saponification degree: 88 mol%) was dissolved in ion-exchanged water to obtain a PVA aqueous solution having a solid content concentration of 9.0% by mass. . This PVA aqueous solution and the above-prepared alumina hydrate sol 1 were converted into PVA solid content ((polyvinyl alcohol) / (alumina hydrate) × 100) with respect to the solid content (preparation amount) of alumina hydrate. ) Was 9.0 mass%. Next, a 3.0% by mass boric acid aqueous solution is mixed with the solid content (preparation amount) of alumina hydrate so as to be 1.5% by mass in terms of the solid content of boric acid. Prepared.

  This coating solution was applied onto the support 1 using a slide die so that the thickness after drying was 35 μm. The temperature of the coating solution was 45 ° C. Next, this was dried at 80 ° C. to prepare a recording medium 1.

(Examples 2 to 10 and Comparative Examples 1 to 11)
Recording media 2 to 21 were produced in the same manner as in Example 1 except that the alumina hydrate sol 1 was changed to alumina hydrate sols 2 to 21. However, since the alumina hydrate sols 11 and 17 to 19 were gelled, no recording medium was produced. For this reason, the recording media 11 and 17 to 19 are missing numbers.

<Evaluation of recording medium>
Next, a recording medium evaluation method and evaluation results will be described.

(Evaluation 1: Evaluation of ink absorbency)
The ink absorbability of the recording media 1 to 21 obtained above was evaluated. For printing, an apparatus modified from the printing method of iP4600 (trade name, manufactured by Canon Inc.) was used. The printing pattern uses a green solid color of 64 gradations (64 gradations in 6.25% duty increments, 0 to 400% duty), and the carriage speed is 25 inches / second, printing in two reciprocating passes. The two-way printing was completed. Note that 400% Duty means that 44 ng of ink is applied to 600 dpi square (a square of 1 square inch at 600 dpi). Since ink absorptivity and beading are substantially correlated, the ink absorptivity of the recording medium was evaluated by evaluating beading. Evaluation was performed visually and the rank was determined based on the following evaluation criteria. As can be seen from Table 1, the recording medium of the present invention has sufficiently usable ink absorbability even at the printing speed of the next generation high-speed printing printer.

Evaluation criteria rank 3: No beading was observed even at 300% duty.
Rank 2: Some beading was observed in the range of 200% duty to 300% duty, but no beading was observed below 200% duty.
Rank 1: Beading was observed even below 200% Duty.

(Evaluation 2: Evaluation of ozone resistance)
The ozone resistance of the recording media 1 to 21 obtained above was evaluated. The printer used was iP4600 (trade name, manufactured by Canon Inc.) and 256 gray patches were printed on each recording medium. Bk (black) O.D. D. The patch closest to 1.0 is exposed to ozone, and the O.D. D. The ozone property was evaluated by the ratio of values (OD residual rate). The conditions for ozone exposure were as follows: temperature: 23 ° C., relative humidity: 50%, ozone concentration: 10 vol ppm, and ozone exposure time: 40 h.

Evaluation criteria rank 4: O.D. D. Residual rate is 95% or more,
Rank 3: O.D. D. Remaining rate is 90% or more and less than 95%,
Rank 2: O.D. D. Residual rate is 80% or more and less than 90%,
Rank 1: O.D. D. Residual rate is less than 80%.

(Evaluation 3: Evaluation of moisture resistance)
The moisture resistance of the recording media 1 to 21 obtained above was evaluated. On these recording media, the printer is iP4600 (trade name, manufactured by Canon Inc.), white letters “Denatsu” are printed on blue solid with 48 points, temperature: 30 ° C., relative humidity: 90%. Left in the environment for 7 days. The degree of bleeding of the color material into the white portions before and after being left was visually evaluated.

・ Evaluation criteria rank 3: Smudge is not confirmed.
Rank 2: A level that is slightly blurred when observed under magnification, but is hardly noticeable with the naked eye.
Rank 1: Bleeding can be confirmed with the naked eye, and the moisture resistance is low.

  As shown in Table 1, in each of the recording media 1 to 10 (Examples 1 to 10), the alumina hydrate sol did not gel, and the solid content concentration of the alumina hydrate sol was 33% by mass. It could be prepared at a high concentration. Moreover, the inkjet recording medium using these alumina hydrate sols 1-10 was excellent in ink absorptivity, moisture resistance, and ozone resistance. On the other hand, in Comparative Examples 1 and 7 to 9 among Comparative Examples, gelation occurred when an alumina hydrate sol was prepared at a high solid content concentration. Also in other comparative examples that do not gel, ink jet recording media using these alumina hydrate sols are inferior in ink absorbability, moisture resistance, or ozone resistance (rank 1). It was.

Claims (3)

A recording medium having an ink receiving layer on a support,
The ink receiving layer contains alumina hydrate, an alkyl sulfonic acid having 1 to 4 carbon atoms, and at least one of hydroxylamine and a salt thereof represented by the following general formula (1):
General formula (1) HO-N (R ¹ ) (R ² )
(Wherein R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a carbamoyl group, an alkoxycarbonyl group, a vinyl group, a phenyl group or an acyl group.)
The alkylsulfonic acid having 1 to 4 carbon atoms is 1.0% by mass or more and 2.0% by mass or less with respect to the alumina hydrate, and the total amount of the hydroxylamine and a salt thereof is 0.2 mass% or more and 2.0 mass% or less with respect to alumina hydrate,
A recording medium characterized by the above. The ink receiving layer is an ink receiving layer obtained by coating a coating liquid containing an alumina hydrate sol and a polyvinyl alcohol aqueous solution on the support,
The alumina hydrate sol includes alumina hydrate, an alkyl sulfonic acid having 1 to 4 carbon atoms, hydroxylamine represented by the general formula (1) and at least one of its salts, and water. ,
The total amount of hydroxylamine represented by the general formula (1) and a salt thereof in the alumina hydrate sol is 0.2% by mass or more based on the alumina hydrate in the alumina hydrate sol. 1.0 mass% or less of the alkyl sulfonic acid having 1 to 4 carbon atoms in the alumina hydrate sol is 1.0 mass% based on the alumina hydrate in the alumina hydrate sol. The recording medium according to claim 1, wherein the recording medium is 2.0% by mass or less and the solid content concentration of the alumina hydrate sol is higher than 30% by mass.   The recording medium according to claim 1, wherein the alkylsulfonic acid is methanesulfonic acid.