JP2010131849A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which has image photographing properties almost equal to those of photographic printing paper for silver salt photography, excellent in ink absorption and coat strength, favorable in post-printing light fastness and high humidity feathering, and has a crack-free surface. <P>SOLUTION: The inkjet recording medium has an air-permeable support obtained by applying or saturating a treatment composition containing at least a boric acid and a borate, and an ink receptive layer formed on the surface of the support, and is manufactured by being applied with cast processsing. In addition, the ink receptive layer is formed of a coating composition containing at least a submicron pigment and a polyvinyl alcohol. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an inkjet recording having image clarity comparable to silver salt photographic printing paper, excellent ink absorption and coating layer strength, good light fastness after printing and high-humidity bleeding, and no cracks on the surface. It relates to the medium.

  In recent years, the technology of inkjet printers has advanced rapidly, and it has become possible to obtain recorded matter having image quality equivalent to or higher than that obtained by a general silver salt photography method. Accordingly, ink jet recording media having a texture equivalent to that of photographic paper used in silver salt photography are required.

  Conventionally, cast coated paper has been used as a glossy inkjet recording medium (see, for example, Patent Documents 1 and 2). However, although the recording medium manufactured by these techniques has a certain level of gloss, it cannot be said that the recording medium has a texture equivalent to that of photographic paper used for silver salt photography.

  In order to solve this problem, it has been proposed to cure the coating layer with an electron beam (see, for example, Patent Document 3). However, a curing apparatus using an electron beam is generally large and has a problem that its maintenance and adjustment are extremely complicated.

  Further, as another technique for the same purpose, an ink receiving layer containing polyvinyl alcohol is formed on a base paper, an aqueous solution containing borate and boric acid is applied on the ink receiving layer, and then the ink receiving layer is received. There has been proposed an ink jet recording medium in which a layer is pressed onto a heated mirror surface to give gloss (see, for example, Patent Document 4). Although good image clarity is obtained, since fine cracks exist on the surface of the coating layer, the ink sinks from the cracks, and a sufficient print density is not obtained.

  In order to solve such a problem, borax is coated on a support, a recording layer is coated thereon, and an outermost layer is provided on the recording layer, while the outermost layer is in a wet state. An inkjet recording medium is proposed in which a gloss is imparted by pressure bonding to a heated mirror drum (see, for example, Patent Document 5). This is because borax is coated on the support between the support and the recording layer, and the polyvinyl alcohol contained in the recording layer is crosslinked by the undercoat borax, so that the recording layer is reduced. The coating liquid gels before becoming a dry part, and cracks of the recording layer are suppressed. However, since the outermost layer to which gloss is imparted does not contribute to crosslinking with borax, the surface is cracked and a sufficient print density is not obtained.

  On the other hand, there is a strong demand for a recording medium that not only has the same texture as photographic paper used in the silver salt photographic method, but also has storability comparable to that recorded by the silver salt photographic method.

  In order to solve this problem, a sol in which colloidal particles of alumina hydrate are dispersed in an aqueous solvent is coated with a coating liquid in which a binder is mixed with an alumina sol containing a compound having a sulfonic acid group in the molecule, and then dried. An ink jet recording medium obtained in this manner has been proposed (see, for example, Patent Document 6). Although good storage stability is obtained, many cracks are observed in the coating layer, and the gloss is insufficient.

Further, a first ink receiving layer mainly composed of inorganic fine particles having an average particle size of 10 to 500 nm and a water-soluble binder is provided on a support, and then a glossy resin is provided on the first ink receiving layer. It has been proposed that a second ink receiving layer as a main component is provided and then nipped by a heated or pressurized mirror surface roll (see, for example, Patent Document 7). Although good gloss and storage stability can be obtained, many fine cracks are seen on the surface, and the texture is not as good as that of photographic paper used in silver salt photography. There has not yet been obtained an ink jet recording medium capable of obtaining the same texture and sufficient storage stability as photographic paper used in the silver salt photography.
JP-A-63-264391 Japanese Patent Laid-Open No. 2-27487 JP 2004-330725 A JP 2007-83631 A JP 2005-186604 A JP-A-8-333115 JP 2000-108504 A

  The object of the present invention is to have image clarity comparable to silver salt photographic printing paper, excellent ink absorption and coating layer strength, good light resistance after printing and high humidity bleeding, and no cracks on the surface. To provide an ink jet recording medium.

  As a result of studying this problem, the inkjet recording medium of the present invention, that is, an air-permeable support formed by applying or impregnating a treatment composition containing at least boric acid and borate on at least one surface, and An inkjet recording medium having an ink receiving layer coated on the surface of the support and manufactured by casting, wherein the ink receiving layer contains at least a submicron pigment and polyvinyl alcohol It is possible to provide an ink jet recording medium characterized by being formed from a coating composition.

Further, the treatment composition has a total concentration of boric acid and borate of 5 to 30% by mass, and a total solid content of boric acid and borate is 0.15 to 2.0 g / m ² attached. It is preferable.

  Moreover, it is preferable in the said treatment composition being 1 / 1-1 / 3 by the mass ratio in a boric acid / borate.

  Moreover, it is preferable that the said processing composition is pH 6-9.

  According to the present invention, ink jet recording having image clarity similar to silver salt photographic printing paper, excellent ink absorption and coating layer strength, good light resistance after printing and high humidity bleeding, and no cracks on the surface. A medium is obtained.

  In the present invention, paper is usually used as the air-permeable support, but a support other than paper, such as a nonwoven fabric, can be used as necessary.

  In the present invention, the ink receiving layer is an object corresponding to characteristics such as absorptivity, image reproducibility, and color for dye inks and pigment inks used in commercially available ink jet printers, ink jet plotters, and ink jet proofers. The coating layer is a liquid composition for drying to form an ink receiving layer. This coating composition is usually used in the form of an aqueous liquid in which each material is dissolved or dispersed in water. In the present invention, two or more ink receiving layers may be provided.

  In the present invention, the cast treatment refers to pressing the ink receiving layer in a wet state onto a heated mirror surface, transferring the mirror surface shape to the surface of the ink receiving layer, and removing moisture from the ink receiving layer by drying to give gloss to the ink jet recording medium. The process to give. The apparatus used for the casting process (casting apparatus) is usually an apparatus having a structure in which the coated paper is continuously crimped to the surface of the cylinder whose surface is chrome-plated using an elastic roll. An apparatus having another structure having the same action may be used. As a method of casting used for producing the ink jet recording medium of the present invention, a so-called rewetting method in which a coating composition is coated, dried once, reapplied with moisture, and then pressure-bonded to a mirror surface of a casting apparatus, coating A method such as a so-called direct method in which the coating composition is coated and then directly pressed onto the mirror surface of the casting apparatus without being dried can be exemplified, but is not limited thereto.

In the present invention, boric acid and borate are contained as a treatment composition on at least one surface of the air-permeable support. Examples of boric acid include orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and the like, and orthoboric acid is particularly preferable in terms of ease of handling and workability. Examples of borates include borax, orthoborate, diborate, metaborate, pentaborate, octaborate, and the like. Particularly, borax can increase the printing density. Therefore, it is preferable.
The reason for using boric acid and borate in combination is as follows. When boric acid is used alone as a treatment composition, a large amount of boric acid is required to crosslink with the polyvinyl alcohol contained in the coating composition and prevent cracking on the surface of the ink receiving layer. It becomes. However, since the solubility of boric acid alone is low, the boric acid concentration cannot be increased. For this reason, a large amount of boric acid aqueous solution must be adhered, resulting in an increase in drying load and a decrease in operation efficiency. In addition, there is a method of increasing the temperature of the treatment composition in order to increase the boric acid concentration, but this requires a large facility for maintaining the high temperature.
In addition, when borate is used alone as a treatment composition, as with boric acid, it crosslinks with polyvinyl alcohol contained in the coating composition so that the surface of the ink receiving layer does not crack. Requires a large amount of borate. The solubility of borate alone is the same as boric acid, and since the borate concentration cannot be increased because it is low, a large amount of borate aqueous solution must be attached, increasing the drying load and operating efficiency. Reduce. Further, there is a method of increasing the temperature of the treatment composition in order to increase the borate concentration, but this requires a large facility for maintaining the high temperature.
However, by mixing boric acid and borate, the solubility of each increases and it becomes easy to make a high concentration aqueous solution, so there is no need to attach a large amount of aqueous solution, and the drying load can be reduced. It becomes possible to operate efficiently. Moreover, since it is not necessary to require a large-scale facility for maintaining a high temperature, the existing facility can be used.

If the total concentration of boric acid and borate in the treatment composition of the present invention is too low, a large amount of adhesion may be required, and the drying load may increase. Since salt may precipitate, it is preferable in it being 5-30 mass%. More preferably, it is 6-25 mass%.
In addition, if the adhesion amount of boric acid and borate is too small, the surface of the ink receiving layer after drying may crack and gloss may decrease, and if it is too large, the print density may decrease. from preferably a 0.15~2.0g / ^{m 2} in total solids. More preferably 0.3 to 1.5 g / ^{m 2.} Further, when the mass ratio of boric acid and borate is 1/1 to 1/3, the pH of the treatment composition changes at a high place, so that the ink receiving layer is in contact with the coating composition having a low pH. This is preferable because the solidification speed is increased, the operation efficiency is improved, and the printing density is increased. More preferably, it is 1/1 to 1/2.

  If the pH of the boric acid and borate treatment composition of the present invention is too low, the surface of the ink-receiving layer after drying may crack and gloss may be lowered. Since bleeding may be reduced, it is preferably 6 to 9. More preferably, it is 7-8.5.

  In the treatment composition containing boric acid and borate of the present invention, a surfactant, an antifoaming agent, a thickening agent, a color adjusting agent, a fluorescent whitening agent, a water-resistant agent, and an antioxidant are added as necessary. Various additives such as an agent and an ultraviolet absorber can also be added.

  In the present invention, there is no particular limitation on the method of applying or impregnating the treatment composition containing boric acid and borate, and vertical type size press, horizontal type size press, incline type size press, gate roll, bill blade, etc. It can be adhered using various coating apparatuses such as a size press apparatus, an air knife coater, a blade coater, a rod blade coater, a bar coater, a reverse roll coater, a comma coater, a lip coater, a die coater, and a curtain coater.

  In the present invention, the submicron pigment means that when the dispersion is dispersed on a substrate and observed with a scanning electron microscope, 80% or more of the area occupied by the particles in the observation field is occupied by particles having a long side of 1 μm or less. Refers to inorganic pigment. The type of submicron pigment used in the coating composition of the present invention is not particularly limited, and examples thereof include gel method silica, precipitation method silica, colloidal silica, gas phase method silica, gas phase method alumina, and pseudoboehmite. . In particular, it is preferable to use an inorganic pigment in which particles having a long side of 400 nm or less occupy 80% or more of the area occupied by the particles in the observation field because particularly high surface gloss can be obtained. In addition, when an inorganic pigment occupying 80% or more of the area occupied by the particles in the observation field is used, particles having a long side of 100 to 400 nm are used. It is more preferable because defects such as surface cracks are less likely to occur.

As the submicron pigment used in the coating composition of the present invention, it is preferable to use a pigment having a specific surface area of a certain level or more because a high printing density can be obtained. On the other hand, if the specific surface area is too large, the ink absorbability may decrease. Specifically, it is preferable to use one having a specific surface area of 60 to 600 m ² / g by the BET method, and more preferably 150 to 400 m ² / g. In addition, the submicron pigment having such a specific surface area is usually a pigment formed by forming a higher order structure in which primary particles having a diameter of several tens of nanometers or less are combined and voids are formed therein.

  In the present invention, when the rewetting method is used as the casting method, pseudoboehmite is preferably used as the submicron pigment of the coating composition because an inkjet recording medium having particularly high gloss can be obtained.

As the polyvinyl alcohol used in the coating composition of the present invention, polyvinyl alcohol having various saponification degrees from 70 mol% to 100 mol% can be used, but when using the rewet method as the method of the casting process used in the present invention, It is preferable to use a saponification degree of 70 to 95 mol% because gloss is easily developed. It is also possible to use modified polyvinyl alcohol in which various functional groups such as silyl group, carboxyl group, amino group, and acetoacetyl group are introduced, and other monomers such as ethylene are introduced randomly, grafted, or in blocks. it can.
If the amount of polyvinyl alcohol added in the present invention is too small, the surface may be cracked during drying, or the surface strength of the formed inkjet recording medium may be insufficient. On the other hand, if the amount of polyvinyl alcohol added is too large, the ink absorbability may decrease. Specifically, the addition amount of polyvinyl alcohol is preferably 2 to 40% by mass of the submicron pigment, and more preferably 5 to 30% by mass.

  Since the polyvinyl alcohol of the coating composition of the present invention has a higher viscosity of the aqueous solution, surface cracks are less likely to occur when the coated composition is dried even if the amount added is relatively small. The addition amount can be reduced, and as a result, the ink absorbability can be improved, which is preferable. However, if the viscosity of the aqueous solution is too high, the viscosity of the coating composition obtained by the present invention becomes too high, which may make the coating operation difficult. Specifically, the viscosity of an aqueous solution having a solid content concentration of 4% by mass measured at 25 ° C. using an Ubbelohde viscometer based on JIS Z8803 is preferably 15 to 400 mPa · sec, and 30 to 200 mPa · sec. More preferably. One of these polyvinyl alcohols may be used alone, or two or more thereof having different saponification degree, viscosity, modification and the like may be used in combination.

  In the ink receiving layer of the present invention, a surfactant, an antifoaming agent, a thickening agent, a color adjusting agent, a fluorescent whitening agent, a water-resistant agent, an antioxidant, an ultraviolet absorber, and a cationic agent are added as necessary. Various additives such as a polymer electrolyte can also be added.

In the present invention, there is no particular limitation on the method of coating the coating composition, air knife coater, blade coater, rod blade coater, bar coater, reverse roll coater, comma coater, gate roll coater, film transfer coater, lip coater, Various coating methods such as a die coater and a curtain coater can be used. Among these, the curtain coater has a high uniformity of the obtained coating layer, and furthermore, when coating the ink receiving layer, the coating composition hardly permeates in the direction of the support and gives a very good surface quality. Therefore, it is preferably used for coating of the coating composition. Although there is no restriction | limiting in particular in the quantity which coats the coating composition of this invention on a support body, In order to make ink absorptivity and economical efficiency compatible, normally 10-25 g / m < ² > is applied as solid content. It is preferable. However, when it is particularly required to absorb a large amount of ink, it may be preferable to apply a maximum of about 30 g / m ² .

  In addition, after applying or impregnating a treatment composition containing boric acid and borate and drying, or after applying or drying the coating composition, a soft calendar, a super calendar, etc. It is also possible to perform the casting process after increasing the smoothness with a calendar device.

  In addition, a release agent such as an oily substance or an aqueous dispersion of an oily substance is added to the coating composition of the present invention for the purpose of improving the peelability from the mirror surface in the casting apparatus, or is applied prior to the casting treatment. When using the rewet method as a casting process, it is preferable to add to the water used for rewet because stable production is possible over a long period of time. Examples of substances that can be used as a release agent in the present invention include higher alkylamines such as dimethyloctylamine and dimethyloctadecylamine or salts thereof, higher alkyl quaternary ammoniums such as trimethyloctylammonium chloride and trimethyloctadecylammonium chloride. Examples thereof include salts, higher carboxylic acids such as oleic acid, stearic acid and caprylic acid or salts thereof, higher alcohols such as octyl alcohol and octadecyl alcohol, liquid paraffin, polyethylene wax and silicone oil.

  Examples of the present invention will be described below. In the examples, unless otherwise indicated, parts are parts by mass, and% is mass%.

[Example 1]
[Preparation of Treatment Composition 1]
To 420 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 40 parts of boric acid _(H 3 _BO 3) 40 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 1 having a total concentration of 16% by mass to be 1/1 was prepared. The pH of the treatment composition 1 at this time was 7.1.

[Preparation of Alumina Hydrate Sol]
1 part of acetic acid is mixed with 299 parts of water, 100 parts of alumina hydrate having a pseudo boehmite structure (Dissal HP 14 manufactured by Sasol) is added and stirred as it is for 2 hours, and the alumina hydrate sol with a solid content concentration of 25% is added. Got. When this dispersion was diluted 100 times with water, dispersed on a glass substrate and observed with a scanning electron microscope, 80% or more of the area occupied by particles in the observation field was occupied by particles having a long side of 100 to 400 nm. It was.

[Preparation of Coating Composition 1]
To 100 parts (solid content 25 parts) of the alumina hydrate sol obtained above, a 10% aqueous solution of polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd.) having a saponification degree of 88 mol% and a 4% aqueous solution having a viscosity of 95 mPa · s at 25 ° C. 20 parts (2 parts of solid content) were added to prepare a coating composition 1.

[Preparation of inkjet recording medium]
^On the base paper (Diafoam made by Mitsubishi Paper Industries Co., Ltd.) having a basis weight of 157 g / m ² , the treatment composition 1 is applied using an air knife coater so that the adhesion amount after drying becomes 1 g / m ^2, and is dried with hot air. machine dried using, after treatment with a soft calender, a coating composition 1, a coating amount after drying was coated with a curtain coater such that the 20 g / m ^2, a hot air type drying It was dried using a machine. Furthermore, the obtained coated paper was processed using a soft calendar. After the ink receiving layer of this coated paper was wetted by contact with water for 5 seconds, it was pressure-bonded to a mirror chrome plating cylinder of a casting apparatus heated to a temperature of 95 ° C. at a linear pressure of 30 kN / m and a speed of 25 m / min. The ink jet recording medium of Example 1 was produced by peeling from the cylinder after drying.

[Example 2]
An ink jet recording medium of Example 2 was produced in the same manner as in Example 1 except that the adhesion amount after drying of the treatment composition 1 was changed to 0.3 g / m ² .

[Example 3]
An ink jet recording medium of Example 3 was produced in the same manner as in Example 1 except that the adhesion amount after drying of the treatment composition 1 was changed to 1.8 g / m ² .

[Example 4]
An ink jet recording medium of Example 4 was produced in the same manner as in Example 1 except that the adhesion amount after drying of the treatment composition 1 was changed to 0.1 g / m ² .

[Example 5]
Deposition amount after drying of the treatment composition 1 to was changed to 3 g / m ² was prepared inkjet recording medium of Example 5 in the same manner as in Example 1.

[Example 6]
[Preparation of Treatment Composition 2]
In 470 parts of water, 15 parts of boric acid (H ₃ BO ₃ ) and 15 parts of borax (Na ₂ B ₄ O ₇ · 10H ₂ O) as a borate are dissolved, and the mass ratio in boric acid / borax is A treatment composition 2 having a total concentration of 6% by mass to be 1/1 was prepared. The pH of the treatment composition 2 at this time was 7.7.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 6 was produced in the same manner as in Example 1 except that the treatment composition 2 was used instead of the treatment composition 1.

[Example 7]
[Preparation of Treatment Composition 3]
380 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 60 parts boric acid _(H 3 _BO 3) 60 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 3 having a total concentration of 24% by mass to be 1/1 was prepared. The pH of the treatment composition 3 at this time was 6.8.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 7 was produced in the same manner as in Example 1 except that the treatment composition 3 was used instead of the treatment composition 1.

[Example 8]
[Preparation of Treatment Composition 4]
In 480 parts of water, 10 parts of boric acid (H ₃ BO ₃ ) and 10 parts of borax (Na ₂ B ₄ O ₇ · 10H ₂ O) as a borate are dissolved, and the mass ratio in boric acid / borax is A treatment composition 4 having a total concentration of 4% by mass to be 1/1 was prepared. The pH of the treatment composition 4 at this time was 7.8.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 8 was produced in the same manner as in Example 1 except that the treatment composition 4 was used instead of the treatment composition 1.

[Example 9]
[Preparation of Treatment Composition 5]
340 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 80 parts of boric acid _(H 3 _BO 3) 80 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 5 having a total concentration of 32% by mass to be 1/1 was prepared. The pH of the treatment composition 5 at this time was 6.5.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 9 was produced in the same manner as in Example 1 except that the treatment composition 5 was used instead of the treatment composition 1.

[Example 10]
[Preparation of Treatment Composition 6]
To 440 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 40 parts of boric acid _(H 3 _BO 3) 20 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 6 having a total concentration of 12% by mass that is ½ was prepared. The pH of the treatment composition 6 at this time was 8.3.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 10 was produced in the same manner as in Example 1 except that the treatment composition 6 was used instead of the treatment composition 1.

[Example 11]
[Preparation of Treatment Composition 7]
To 440 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 45 parts boric acid _(H 3 _BO 3) 15 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 7 having a total concentration of 12% by mass to be 1/3 was prepared. The pH of the treatment composition 7 at this time was 8.4.

[Preparation of inkjet recording medium]
An ink jet recording medium of Example 11 was produced in the same manner as Example 1 except that the treatment composition 7 was used instead of the treatment composition 1.

[Example 12]
[Preparation of Treatment Composition 8]
In 440 parts of water, 40 parts of boric acid (H ₃ BO ₃ ) and 20 parts of borax (Na ₂ B ₄ O ₇ · 10H ₂ O) are dissolved, and the mass ratio in boric acid / borax is A treatment composition 8 having a total concentration of 12% by mass to be 2/1 was prepared. The pH of the treatment composition 8 at this time was 6.3.

[Preparation of inkjet recording medium]
Instead of the treatment composition 1, the treatment composition 8 was used in the same manner as in the embodiment 1 except that the treatment composition 8 was used and the amount of the treated composition 8 after drying was changed to 1.5 g / m ² . An ink jet recording medium was produced.

[Example 13]
[Preparation of Treatment Composition 9]
450 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 40 parts of boric acid _(H 3 _BO 3) 10 parts of boric acid salt, the weight ratio of boric acid / borax A treatment composition 9 having a total concentration of 10% by mass that was ¼ was prepared. The pH of the treatment composition 9 at this time was 8.6.

[Preparation of inkjet recording medium]
An ink jet recording medium of Example 13 was produced in the same manner as in Example 1 except that the treatment composition 9 was used instead of the treatment composition 1.

[Example 14]
[Preparation of vapor phase silica dispersion]
While stirring 392 parts of water, 8 parts of a 50% aqueous solution of a dimethyldiallylammonium chloride polymer having a viscosity of 400 mPa · s (solid content 4 parts), gas phase method silica (specific surface area 90 m ² / g by BET method) 100 Part was added and predispersed using a blade type disperser. The obtained preliminary dispersion was treated with a colloid mill to obtain a vapor phase silica dispersion having a solid concentration of 20.8%. When this dispersion was diluted 100 times with water, dispersed on a glass substrate and observed with a scanning electron microscope, 80% or more of the area occupied by the particles in the observation field was occupied by particles having a long side of 100 to 400 nm. It was.

[Preparation of Coating Composition 2]
To 100 parts (solid content 20.8 parts) of the vapor phase silica dispersion obtained above, a saponification degree of 88 mol%, a 4% aqueous solution of polyvinyl alcohol having a viscosity of 95 mPa · s at 25 ° C. (PVA235 manufactured by Kuraray Co., Ltd.) A coating composition 2 was prepared by adding 40 parts of a 10% aqueous solution (4 parts solids) and mixing.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 14 was produced in the same manner as in Example 1 except that the coating composition 2 was used instead of the coating composition 1.

[Example 15]
[Preparation of Treatment Composition 10]
In 465 parts of water, 30 parts of boric acid (H ₃ BO ₃ ) and 5 parts of borax (Na ₂ B ₄ O ₇ · 10H ₂ O) are dissolved, and the mass ratio in boric acid / borax is A treatment composition 10 having a total concentration of 7% by mass to be 6/1 was prepared. The pH of the treatment composition 10 at this time was 5.8.

[Preparation of inkjet recording medium]
In place of the treatment composition 1, the treatment composition 10 was used, and the amount of adhesion after drying of the treatment composition 10 was changed to 1.5 g / m ² . An ink jet recording medium was produced.

[Example 16]
[Preparation of Treatment Composition 11]
To 455 parts of water, was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 40 parts of boric acid _(H 3 _BO 3) 5 parts boric acid salt, the weight ratio of boric acid / borax A treatment composition 11 having a total concentration of 9% by mass to be 1/8 was prepared. At this time, the pH of the treatment composition 11 was 9.3.

[Preparation of inkjet recording medium]
An inkjet recording medium of Example 16 was produced in the same manner as in Example 1 except that the treatment composition 11 was used instead of the treatment composition 1.

[Comparative Example 1]
[Preparation of Treatment Composition 12]
To 460 parts of water, it was dissolved 40 parts of boric acid _(H 3 _BO 3), to prepare a concentration of 8% by weight of the treatment composition 12 only with boric acid. At this time, the pH of the treatment composition 12 was 3.6.

[Preparation of inkjet recording medium]
Instead of the treatment composition 1, the treatment composition 12 was used, and the amount of adhesion after drying of the treatment composition 12 was changed to 1.5 g / m ² . An ink jet recording medium was produced.

[Comparative Example 2]
[Preparation of Treatment Composition 13]
To 460 parts of water, it was dissolved borax _{(Na 2 B 4 O 7 ·} 10H 2 O) 40 parts to prepare a concentration of 8% by weight of the treatment composition 13 only borax. The pH of the treatment composition 13 at this time was 9.6.

[Preparation of inkjet recording medium]
An inkjet recording medium of Comparative Example 2 was produced in the same manner as in Example 1 except that the treatment composition 13 was used instead of the treatment composition 1.

[Comparative Example 3]
An inkjet recording medium of Comparative Example 3 was produced in the same manner as in Example 1 except that the treatment composition 1 was not adhered.

[Comparative Example 4]
[Preparation of coating composition 3]
To 100 parts (solid content 25 parts) of the above-obtained alumina hydrate sol, 15 parts (solid content 4.5 parts) of a 30% solution of polyurethane resin (Daiichi Kogyo Seiyaku Superflex 620) was added. Then, a coating composition 3 was prepared.

[Preparation of inkjet recording medium]
An inkjet recording medium of Comparative Example 4 was produced in the same manner as in Example 1 except that the coating composition 3 was used instead of the coating composition 1.

[Evaluation of image clarity]
The gloss was evaluated by measuring the image clarity having a good correlation with visual gloss. In addition, the measurement was performed using a Suga Test Instruments Co., Ltd. image clarity measuring device at a measurement angle of 45 ° and an optical comb width of 2.0 mm. In the measurement by this method, in general, an ink jet recording medium giving 60% or more image clarity has a high gloss, and an ink jet recording medium giving 65% or more image clarity has a very high gloss.

[Evaluation of ink absorbency]
Using a PIXUS850i type ink jet printer manufactured by Canon Inc., a white line (non-printing portion) lattice pattern is created in a mixed color solid pattern composed of cyan ink and magenta ink. Evaluated. The evaluation Δ and × are practically problematic levels.
A: The lattice is completely clear.
○: Ink oozing is observed on only a part of the lattice.
(Triangle | delta): A grating | lattice becomes narrow and the bleeding of an ink is seen generally.
X: Lattice is absent due to ink bleeding.

[Print density]
Using the ink jet printer described above, a solid pattern was printed with black ink, and the optical reflection density of the printed portion was measured with a Macbeth RD-918 reflection densitometer.

[Evaluation of light resistance]
Using the ink jet printer, solid printing was performed with cyan, magenta, yellow, and black inks, respectively, and irradiation was performed at 600 W / m ² for 30 hours with a Suntest CPS photobleaching tester manufactured by Atlas. The degree of fading of each color density of the image was observed and evaluated according to the following criteria. The evaluation Δ and × are practically problematic levels.
A: Almost no fading is observed.
○: Slight fading is observed.
Δ: Considerable fading is observed.
X: The degree of fading is remarkable.

[Evaluation of coating layer strength]
The writing property when writing characters with a ballpoint pen on the ink receiving layer was visually evaluated. The evaluation Δ and × are practically problematic levels.
A: The ink receiving layer is never scraped off by a ballpoint pen, and the writing property is very good.
○: The ink receiving layer is hardly scraped off by a ballpoint pen, and the writing property is good.
Δ: The ink receiving layer is slightly scraped off by a ballpoint pen, and there is a slight problem in character interpretation.
X: The ink receiving layer is significantly scraped off by a ballpoint pen, and the character cannot be read.

[Evaluation of high humidity bleeding]
Using a Seiko Epson PM-G800 type ink jet printer, after printing a solid pattern (ink placement amount 100%) with yellow, magenta, cyan and black inks, the ink jet recording medium was placed in an environment of 30 ° C. and 80% RH. For 1 week, the degree of bleeding of each color was visually observed and evaluated according to the following criteria. The evaluation Δ and × are practically problematic levels.
A: No bleeding is observed for each color.
○: Slight bleeding is observed in any color.
(Triangle | delta): A blur is considerably seen in either color.
X: Significant bleeding is observed in any color.

[Evaluation of surface cracks]
The ink receiving layer was visually observed, and the surface cracks were evaluated according to the following criteria. The evaluation Δ and × are practically problematic levels.
A: No cracks are seen on the surface.
○: Slightly small cracks are observed on the surface.
Δ: The surface is considerably cracked.
X: Cracks are clearly seen on the entire surface.

  Table 1 shows the image clarity, ink absorptivity, printing density, coating layer strength, light resistance, high humidity bleeding, and surface cracks of the recording media obtained in each Example and each Comparative Example.

  From Table 1, an air-permeable support formed by applying or impregnating at least one surface of Examples 1 to 16 with a treatment composition containing at least boric acid and borate, and on the surface of the support An ink jet recording medium having a coated ink receiving layer and manufactured by casting, wherein the ink receiving layer is formed from a coating composition containing at least a submicron pigment and polyvinyl alcohol. The medium has the same image clarity as photographic paper for silver salt photography, excellent ink absorption, printing density and coating layer strength, good light fastness after printing and high humidity bleeding, and no cracks on the surface. It is good.

  On the other hand, when only boric acid is adhered to the surface of the support and no borate is adhered to the surface of the support as in the ink jet recording medium of Comparative Example 1, the surface of the ink receiving layer is cracked, and image clarity and ink absorption are observed. The properties and coating layer strength decreased. Further, as in the case of the ink jet recording medium of Comparative Example 2, when only borate is adhered to the surface of the support and no boric acid is adhered, the surface is not cracked, but the light resistance and high humidity after printing are not observed. Bleeding worsened. Further, as in Comparative Example 3, when boric acid and borate are not attached to the surface of the support, there is no cross-linking reaction with the polyvinyl alcohol of the ink receiving layer, so the surface is cracked after coating the ink receiving layer. As a result, cracks on the surface remained even after casting, and a great decrease in image clarity and coating layer strength was observed. Further, the ink absorbability was also lowered. Further, as in the ink jet recording medium of Comparative Example 4, when a polyurethane resin was added instead of polyvinyl alcohol in the ink receiving layer, the ink absorbability was good, but boric acid present on the surface of the support was present. Since there was no cross-linking reaction with borate, the surface was cracked after application of the ink-receiving layer, and the surface crack remained even after the casting process, so that the image clarity was reduced. In either case, satisfactory quality could not be obtained.

Claims (4)

  An air-permeable support formed by applying or impregnating a treatment composition containing at least boric acid and a borate on at least one surface, and an ink receiving layer coated on the surface of the support And an ink jet recording medium produced by casting, wherein the ink receiving layer is formed of a coating composition containing at least a submicron pigment and polyvinyl alcohol. The treatment composition has a total concentration of boric acid and borate of 5 to 30% by mass, and a total solid content of boric acid and borate is 0.15 to 2.0 g / m ² attached. The ink jet recording medium according to claim 1.   The ink jet recording medium according to claim 1, wherein the treatment composition has a mass ratio of boric acid / borate of 1/1 to 1/3.   The inkjet recording medium according to any one of claims 1 to 3, wherein the treatment composition has a pH of 6 to 9.