JP2001253162A - Ink absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink absorber for recording sheets, which has high optical density, water resistance and light resistance, an ink acceptor and an ink acceptor slurry. SOLUTION: The recording sheets are proved to have high optical density at printing, excellent water resistance and light resistance under the condition that the aimed-at degree of constraint parameter, which shows the order of constraint of the ink coloring matter particles in the ink absorber, is present in a certain range. Further, in the case that the ink absorber is a solid acid such as silica or the like, the above physical properties are remarkably improved by setting its acid strength and acid amount within certain ranges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink absorbent, an ink receptor, an ink receptor slurry used for an ink jet recording sheet and the like, and a recording sheet thereof.

[0002]

2. Description of the Related Art The spread of the Internet and digital cameras has increased the opportunity to output high-quality full-color images on paper or the like. Printers based on the ink jet system have features such as easy full-color printing, low cost, and low noise, and are therefore rapidly becoming popular as output devices for these images. The ink jet system is a system in which ink droplets are ejected from nozzles at a high speed and adhered to a recording material to perform recording. Since a large amount of solvent is contained in the ink and the ink droplets are continuously ejected, problems such as the ink droplets fusing with each other on the recording sheet, spreading the dots, and mixing the colors are likely to occur. For this reason, the ink jet recording sheet is required to absorb ink promptly, not mix ink even when dots overlap, have no dot bleeding, and have high optical density. Further, the light resistance and water resistance of the recorded image obtained at the same time are also required.

[0003] From such a viewpoint, it has been proposed that various organic substances and inorganic substances are coated or filled into a base material together with a binder as necessary, as a recording sheet for ink jet. For example, a recording sheet provided with an ink receiving layer made of a water-soluble resin such as polyvinyl alcohol on paper or a plastic film, or a recording sheet provided with an ink receiving layer containing a filler such as silica gel is known. I have. For example, Japanese Patent Application Laid-Open No. Sho 62-15808
No. 4 discloses an ink jet recording medium that uses synthetic fine-grained silica, has glossiness, and has a high ink color density.

Japanese Patent Application Laid-Open No. 1-259670 discloses an ink jet recording paper characterized by using fine-particle silica surface-treated with calcium and magnesium as a white pigment. An ink jet recording paper using boehmite as an ink receiving layer is disclosed. However, there has not been obtained any one which can sufficiently satisfy all of optical density, water resistance and light resistance at the same time.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink absorbent, an ink receiver, and an ink receiver slurry for a recording sheet having a high optical density, excellent water resistance, and excellent light resistance. .

[0006]

Means for Solving the Problems The present inventors have focused on a constraint degree parameter indicating the degree to which the ink dye molecules of the ink absorbent are constrained. It has been found that the contained recording sheet has a high optical density at the time of printing and is excellent in water resistance and light resistance. Further, when the ink absorbent is a solid acid such as silica, it has been found that the physical properties described above are remarkably improved by limiting the acid strength and the acid amount to certain ranges, and the present invention has been accomplished. That is, the present invention is as follows. 1. The proton-NMR spin-spin relaxation time of a mixture obtained by mixing a 10% by weight D ₂ O solution of a water-soluble ink, Acid Red 18, and an ink absorbent at a weight ratio of 2: 1 at 30 ° C. at CPMG The correlation between the obtained magnetization Mt and the elapsed time waiting time t immediately after the irradiation of the 90 ° pulse in the CPMG pulse sequence,
An ink absorbent characterized in that a constraint degree parameter し て obtained by optimization calculation according to the formula (1) is 0.1 or more. M _t = M ₀ [χexp (−t / T ₂ short) + (1−χ) exp (−t / T ₂ long)] (1) (where T ₂ short, T ₂ long, and A component with a short spin-spin relaxation time obtained by optimization calculation,
Component with long spin spin relaxation time (T ₂ short <T ₂ lon
g), and the constraint parameter (mol fraction of the proton component having T ₂ short in the two components). )

2. The amount of acid (A4) up to the acid strength function H0 = + 4.0 is 0.05 mmol / g or less, and the amount of acid (A4.8) up to the acid strength function H0 = + 4.8, 0.
2. The ink absorbent according to 1, wherein the amount is 1 mmol / g or less. 3. The ink absorbent according to 1 or 2, wherein the ink absorbent according to 3, 1 or 2 is mesoporous silica. 4. An ink receiver comprising the ink absorbent described in any one of 4, 1 to 3, and a binder. An ink receiver slurry comprising the ink receiver described in 5, 5 and a solvent. A recording sheet obtained from the ink receiver slurry according to any one of claims 6 and 5.

Hereinafter, the present invention will be described in detail. The ink absorbent of the present invention has a constraint parameter χ obtained by nuclear magnetic resonance spectrum (NMR) relaxation time measurement of 0.1.
It is characterized by indicating one or more. That is, when the restricting degree parameter の of the ink absorbent is 0.1 or more, the ink has a high optical density and is an excellent ink absorbent that simultaneously satisfies water resistance and light resistance. The constraint parameter is preferably 0.1
The range of -0.3 is good. More preferably 0.12-
A range of 0.18 is good. The ink absorbent of the present invention is not particularly limited as long as it satisfies the above conditions, and organic substances such as white carbon, inorganic substances, and mixtures thereof,
Anything can be used. Preferably, inorganic porous materials such as amorphous silica, mesoporous silica, and alumina and mixtures thereof are preferable.

The constraint parameter of the ink absorbent of the present invention is calculated by the following method. In the present invention, a commercially available acid red ink 18 is used. The solid acid red 18 is dissolved in heavy water (D ₂ O). The ink concentration at that time is 10 wt%. Next, this Acid Red 18 solution is thoroughly stirred at a weight ratio of 2/1 with respect to the dried ink absorbent, sealed, left for 2 hours, and measured by nuclear magnetic resonance spectrum (NMR). The type of the ink absorbent varies depending on its type, but it is necessary that 90% or more of the contained water is removed.

The spin relaxation time of the proton in the ink is 30 ° C., Curr-Purr-Meiboom-
Gill (CPMG) method (Meiboom and G
ill, Rev .; Sci. Instrum. 1958)
Using a JNM-Mu25 Pulse NMR spe
The measurement was carried out with a trometer (JEOL Co. Ltd) without rotation and without locking. The optimization calculation is
Relaxation curve of magnetization, namely the measured value Mtobs magnetization corresponding to each of the waiting time t, the following equation _{M t = M 0 [χexp (} -
t / T ₂ short) + (1-χ) exp (−t / T ₂ long)], and using a correlation coefficient R between calculated values Mtcal of magnetization Mt corresponding to each t as an evaluation function, R> 0.999
The optimization calculation is repeated until the following three variables T ₂ sh
ort, T ₂ long, χ optimization calculation. here,
M ₀ , M _t T ₂ short, T ₂ long, and χ are the magnetization at time t = 0, the magnetization at time t after applying 90 pulses in the pulse sequence of the CPMG method, and the spin spin relaxation time, respectively. The short component, the component having a long spin-spin relaxation time, and the constraint parameter (molar fraction of the proton component having T ₂ short in the two components) are shown.

The mathematical method of optimization is not particularly limited,
For example, the Simplex method (P. K. MacKeon and
d D. J. Newman, “Computation
alTechniques in Physics ", p
124, IOP, Bristol, 1987). The ink absorbent having a constraint parameter χ of 0.1 or more obtained from NMR relaxation time measurement using Acid Red 18 has high optical density, water resistance, and light resistance in a printing test using any commercially available ink. Excellent. The ink itself used for the printing test may be a known one,
Any dye such as a direct dye, an acid dye, a basic dye, a reactive dye, or a water-soluble dye such as a food colorant can be used. For example, as a direct dye, CIDirect Black 17, 19, 32, 51, 71, 1
08, 146, CIDirect Blue 6, 22, 25, 71, 86, 9
0, 106, 199 CIDirect Red 1, 4, 17, 28, 83 CIDirect Yellow 12, 24, 26, 86, 98,
142 CIDirect Orange 34, 39, 44, 46, 60 CIDirect Violet 47, 48 CIDirect Brown 109 CIDirect Green 59 CIAcid Black 2, 7, 24, 26, 31, 52, 6
3, 112, 118 CIAcid Blue 9, 22, 40, 59, 93, 10
2, 104, 113, 117, 120, 167, 22
9,234 CIAcid Red 1,6,18,32,37,51,5
2, 80, 85, 87, 92, 94, 115, 180,
256, 315, 317, CIAcid Yellow 11, 17, 23, 25, 29, 4
2,61,71 CIAcid Orange 7,19 CIAcid Violet 49 Others CIBasic Blue 1,3,5,7,9,24,25,2
6, 28, 29 CIBasic Red 1, 2, 9, 12, 13, 14, 27 CIBasic Black 1, 2, and the like.

In the present invention, the acid strength function H0 = + 4.
An ink absorbent having an acid amount up to 0 (A4) of 0.05 mmol or less and an acid amount (A4.8) of 0.1 mmol or less up to an acid strength function H0 = + 4.8 has a remarkable optical density and water resistance. Excellent light fastness. The acid strength function H0 = +
Acid amount up to 4.0 (A4) and acid strength function H0 = +
The acid amount up to 4.8 (A4.8) can be determined by the n-butylamine titration method (also known as the Johnson method) (Reference: for example, "Catalyst" Vol. 11, No. 6, p. 210-216 (196)
Determined based on 9)).

The amount of acid (A4) up to the acid strength function H0 = + 4.0 which satisfies the condition that the constraint degree parameter is 0.1 or more.
Is 0.05 mmol or less, and the acid strength function H0 = +
An ink absorbent having an acid amount (A4.8) of 0.1 mmol or less up to 4.8 is excellent in optical density, water resistance, and light resistance.
In particular, light resistance is dramatically improved as compared with the conventional one. Here, the amount of acid up to the acid strength function H0 = + 4.8 is 0.1 m.
Even if the amount is less than or equal to mol, the above performance is not improved unless the amount of acid (A4) up to the acid strength function H0 = + 4.0 is less than 0.05 mmol. Further, even if the acid amount (A4) up to the acid strength function H0 = + 4.0 is 0.05 mmol or less,
Unless the amount of acid (A4.8) up to the acid strength function H0 = + 4.8 is 0.1 mmol or less, the above performance is not improved.

The present invention is characterized in that it exhibits effects on optical density, water fastness and light fastness when the restraint degree parameter and acid strength function of the ink absorbent are under certain conditions as described above. It is more effective when silica is used as the ink absorbent. Hereinafter, a case where mesoporous silica is used as an ink absorbent will be described more specifically.

The mesoporous silica in the present invention is:
It is an inorganic porous material having a uniform average pore diameter in the mesopore region of 1.5 to 30 nm, and has crystallinity that is clearly recognized by powder X-ray diffraction. Mesoporous silica is
For example, as described in JP-T-5-503499, an amorphous silica powder or an aqueous solution of an alkali silicate is used as a silica source, and a quaternary ammonium salt having a long-chain alkyl group or a phosnium salt is used as a template. And a method of synthesizing by hydrothermal synthesis. Alternatively, P.I. T. Taev et al. (Chem. Mater. Vol. 8 P. 2068-
2079 (1996)), a method using an alkoxide such as tetraethoxysilane as a silica source and using an alkylamine or the like as a template, or Zhao et al. (J. Am. Che
m. Soc. vol. 120 p. 6024 (199
As shown in 8)), there is a production method based on a two-stage reaction in which a silica condensation reaction is carried out at around normal temperature using a nonionic surfactant as a template in an acidic medium, and then left at 80 ° C.

In the synthesis of mesoporous silica, the parameter of the degree of constraint can be kept in the range of 0.1 to 0.3 by changing the reaction temperature, time and the like. For example,
In the case of a production method using a nonionic surfactant as a template in the above-described acidic medium, increasing the reaction temperature in the second stage can increase the constraint parameter.
Preferably, the temperature is 95 ° C. or higher. Even when the reaction is carried out at about 80 ° C., by setting the reaction time longer than 48 hours, the constraint parameter can be made 0.1 or more.

The constraint parameter can also be controlled by changing the type and amount of the micelle forming aid of the template. For example, when 1,3,5-triisopropylbenzene, 1,3,5-tributylbenzene, or the like, whose structure is bulkier than conventionally reported micelle formation aids, the constraint degree parameter is set to 0.1 or more. However, the micelle forming aid that can be used is not limited to these. When 1,3,5-triisopropylbenzene or 1,3,5-tributylbenzene is used, the amount of the micelle forming aid may be about 1.0 to 3.0 times by weight based on the template. It is preferably, more preferably, 2.5 to 3.0 times.

Further, by combining the above preferable reaction conditions, the constraint degree parameter can be controlled in a more preferable range of 0.12 to 0.18. These preferred reaction conditions can be applied to other mesoporous silica synthesis methods. Alternatively, the constraining degree parameter can be controlled by partially introducing a cationic functional group such as an amino group, an amide group, or a quaternary ammonium base into the obtained mesoporous silica. Examples of the method of introduction include a method of adsorbing the above-mentioned compound having a cationic functional group on mesoporous silica, and a method of reacting the compound with a silanol group of mesoporous silica using a silane coupling agent.

Even if the ink absorbent of the present invention is not mesoporous, it is possible to control the constraint parameters by controlling the synthesis method such as temperature conditions and reaction time, or by introducing a cationic functional group. . When mesoporous silica is used as the ink absorbent, the acid strength function H0
The amount of acid (A4) up to +4.0 is 0.05 mmol or less, and the amount of acid up to the acid strength function H0 = + 4.8 (A4.
In order to limit 8) to 0.1 mmol or less, a method of adding a metal salt of an alkaline earth metal or the like when synthesizing the mesoporous silica can be adopted.

As the metal atom of the alkaline earth metal, calcium, magnesium and zinc are preferred. The content of the metal atom of the alkaline earth metal is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the mesoporous silica on an oxide basis. Also, a method for limiting the surface silanol group density,
Alternatively, a method of coating with an alkali metal or an alkaline earth metal is possible. Also, as in the case of the constraint degree parameter, appropriate introduction of an amino group, an amide group, or a quaternary ammonium base is effective for controlling the acid strength function.

Even if the ink absorbent of the present invention is other than mesoporous silica, the acid strength function can be controlled by containing an alkaline earth metal atom. The method for preparing the ink absorbent containing an alkaline earth metal atom is not particularly limited. For example, it can be obtained by a method in which a slurry of the ink absorbent and a solution or slurry containing metal atoms are mixed and deposited or reacted. Alternatively, a method in which a metal salt or the like is directly added to the slurry of the ink absorbent to cause deposition or reaction may be employed.

The ink receiver according to the present invention is characterized by containing an ink absorbent and a binder. The binder in the present invention is not particularly limited, carboxymethyl cellulose, ethyl cellulose,
Hydroxyethyl cellulose, starch, carboxymethyl starch, cyanoethylated starch, casein, gum arabic,
Water-soluble binders such as tragacanth rubber, dextrin, polyvinyl alcohol, vinyl ether / maleic acid copolymer, polyvinyl pyrrolidone, and water-soluble acrylic resin, aqueous latex binders such as styrene / butadiene copolymer latex, and self-emulsifying acrylic resin Emulsifying binders and the like are not limited to these.

The content of the binder in the ink receiver varies depending on the kind thereof, and is not particularly limited. However, the content is usually 5 to 100 parts by weight of the ink absorbent.
Used in the range of 300 parts by weight. Further, silica gel, calcium carbonate, talc, titanium oxide, kaolin, zeolite, alumina or the like may be added as a pigment to the ink receiver of the present invention.

The ink receiver slurry according to the present invention is characterized by containing the above-mentioned ink receiver and a solvent.
The solvent used for the ink receiver slurry is not particularly limited, but alcohols such as ethanol and isopropyl alcohol, various known organic solvents such as acetone and methyl ethyl ketone, and water can be used. The content of the ink absorbent in the ink receiver slurry varies depending on the coating method and the mode of use, and is not particularly limited, but is preferably 5% by weight or more, more preferably 10% by weight or more. It is preferred to contain.

The recording sheet in the present invention is obtained by coating or filling the above-mentioned ink receptor slurry on a substrate such as a synthetic resin film or paper. As the synthetic resin film, for example, polyester, polyolefin, polyamide, polyesteramide, polyvinyl chloride and the like can be used. In addition, these copolymers, blends, crosslinked products, or opaque films kneaded with pigments, foamed films,
A gloss film or the like can be used. Among the above substrates, polyester, preferably polyethylene terephthalate, is preferred in terms of mechanical properties, workability, and the like.

As the paper, for example, high quality paper, medium quality paper, art paper, cast coated paper, coated paper, synthetic paper, resin coated paper and the like can be used. In addition to synthetic resin films and papers, cloths such as cotton, rayon, acrylic, etc., glass plates, metals and the like can be used according to the application. There is no particular limitation on the thickness of the substrate, but usually a substrate having a thickness of 10 to 200 μm is often used.

The means for coating the ink receptor slurry on the substrate surface may be, for example, a method in which the slurry is coated with a die coater,
Roll coater, rod coater, blade coater,
A method of applying and drying using various known methods such as an air knife coater can be used. Further, a dip coating method in which the substrate is immersed in the slurry, a spray method in which the slurry is sprayed on the substrate, a method in which the slurry is coated on the molding surface and transferred to the substrate, and the like can also be used.

The base material may be subjected to a known surface treatment such as corona discharge treatment or primer treatment in the air or other atmosphere before coating, if necessary, to improve the coating properties and adhesiveness of the slurry. You can also. Further, it may be coated in multiple layers, coated on both sides of the substrate, or laminated with layers having different physical properties such as a protective layer, a gloss layer, and an adhesive layer. The thickness of the coating is 1-100 μm, preferably 5-50 μm
m, more preferably 5 to 30 μm. The content of the ink absorbent in the coating layer is 0.5 to 30 g /
m ² is preferred, and more preferably 0.5 to 15 g / m ² . If the content of the ink absorbent is less than 0.5 g / m ² , the ink absorbency may be insufficient.

[0029] The ink absorbent may be incorporated into the base material. For example, in the case of paper, a method in which the slurry of the present invention is added to the slurry for papermaking can be used. . Further, a method in which an ink absorbent is mixed with a synthetic resin or the like and formed into a film or sheet by a casting method, an extrusion method, a calendar method, or the like can also be used. The synthetic resin is not particularly limited, but is preferably a vinyl alcohol-based resin, an acrylic resin, a urethane-based resin, an amino acid-based resin, or the like, which has high water permeability. The content of the ink absorbent based on the entire sheet is preferably 0.5 to 30% by weight. The recording sheet according to the invention is more effective by printing the ink containing the dye as described above in an ink jet mode. The form of printing is not particularly limited, such as a bubble jet method or a piezo method.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the embodiment, the acid strength function H0 = +
Acid content up to 4.0 (A4) and acid strength function H0 = + 4.
The acid amount up to 8 (A4.8) was measured by the following method. 2
10m benzene in two 50ml stoppered Erlenmeyer flasks
Then, 0.3 g of the dried ink absorbing agent is put into each of them. In each of these two flasks,
(Phenylazo) -1-naphthalene and methyl red solution were added in an amount of 0.3 ml each to color the sample in an acidic color, and then 0.1 n-n-
Each is titrated with a butylamine / benzene solution over 2 days until the sample loses its acidic color. At this time, the amount of each acid A (A4 and A4.
8) was calculated using the following equation. A (mmol / g) = NfV / W

Here, N and f represent the normality and factor of n-butylamine, V represents the amount of n-butylamine solution required for titration, and W represents the exact weight of the sample charged.
f is determined by the following method. 20 ml of distilled water is placed in a 50 ml Erlenmeyer flask, and 5 ml of a 0.1 N n-butylamine / benzene solution is added thereto. The n-butylamine eluted in the aqueous phase is titrated with a 0.1 N oxalic acid standard solution using a phenolphthalein indicator to obtain f. In some cases, H0 is larger than +4.8 as a solid acid, that is, there may be some weaker acids. However, in reality, the amount of the acid obtained by the above method is scarcely considered as the total acid amount.

The performance evaluation (optical density, light fastness, and water fastness) of the ink absorbent was performed by the following method unless otherwise specified. Each sample was mixed with a solvent (water or alcohol) and a commercially available binder (cation-modified polyvinyl alcohol and silanol-modified polyvinyl alcohol) to form a slurry, which was then coated on a commercially available polyethylene terephthalate (PET) film, dried, and recorded. I got a sheet. Solid printing of yellow, magenta, cyan, black, green, red, and blue was performed on this recording sheet using a commercially available inkjet printer (PM800, manufactured by Seiko Epson Corporation). The evaluation items are as follows.

1) Optical Density The optical density of magenta immediately after printing and drying was measured using a reflection densitometer (RD-918, manufactured by Gretag Macbeth).
The grades of the optical density were classified into the following four types. ◎ Extremely high optical density ○ High optical density △ Normal optical density ×
Low optical density 2) Light fastness A black-panel temperature of 60 ° C, a window glass filter is used, and irradiance is 7 on the printed recording sheet, using a desktop accelerated weathering exposure system, Suntest CPS + (manufactured by Toyo Seiki).
Irradiation was performed under the conditions of 65 W / m ² . After 60 hours, the optical density of magenta was measured, and the rate of change in density was determined. The optical density was measured as described above. Light resistance was classified into the following four grades. ◎ Excellent light resistance ○ Excellent light resistance △ Normal light resistance × Poor light resistance 3) Water resistance The printed recording sheet was immersed in water for 2 minutes, then dried at room temperature, and the degree of ink bleeding and runoff was visually determined. The grades were similarly classified into the following four types. ◎ Excellent water resistance ○ Good water resistance △ Normal water resistance × Poor water resistance

[0034]

Example 1 Nonionic high molecular surfactant (Aldri)
ch Pluronic P123, poly (ethyl
ene glycol) -block-poly (pr
opyleneglycol) -block-poly
50 g of (ethylene glycol) was dissolved in 1324 g of purified water at room temperature. 100 g of 1,3,5-triisopropylbenzene and 250 ml of concentrated hydrochloric acid were added thereto, and the temperature was raised to 35 ° C. To this, 104.2 g of tetraethoxysilane was added and stirred at 35 ° C. for 20 hours. Then, it was left at 80 ° C. for 48 hours. The obtained complex is filtered,
After washing with water, a composite powder of silica and a template was obtained. The obtained white powder is dispersed in 800 ml of ethanol,
The mixture was stirred at 60 ° C. for 30 minutes. This is filtered and 80
0 ml of ethanol was added for washing. This operation was repeated five times. Then, it was dried at 70 ° C. for 23 hours to obtain mesoporous silica. This is designated as Sample 1.

Χ, A4, A4.8 of this sample 1 were calculated by the above-mentioned method, and are shown in Table 1. The performance of Sample 1 as an ink absorbent was evaluated by the following method. This sample 1 and water were mixed to prepare a dispersion of the sample 1 having a concentration of 13.8% by weight. This was mixed with a 10% by weight aqueous solution of a cation-modified polyvinyl alcohol and a 10% by weight aqueous solution of a silanol-modified polyvinyl alcohol, and the weight ratio of the dispersion of Sample 1 to the aqueous solution of the cation-modified polyvinyl alcohol and the aqueous solution of the silanol-modified polyvinyl alcohol was 6: 2. :
In 2, an ink absorbent slurry having a solid content of 12% by weight was prepared. Subsequently, an ink absorber slurry was applied to a polyethylene terephthalate sheet (thickness: 100 μm) using a bar coater and then dried to obtain a recording sheet having a 30 μm thick ink absorber layer. With respect to this recording sheet, printing performance was evaluated for the evaluation items described above.
The evaluation results are also shown in Table 1.

[0036]

Example 2 150 g of 1,3,5-triisopropylbenzene was used.
A sample 2 was mesoporous silica synthesized under the same conditions as in Example 1 except that the temperature was ° C. Χ, A of this sample 2
4 and A4.8 were calculated under the same conditions as in Example 1, and are shown in Table 1. A recording sheet was obtained from Sample 2 in the same manner as in Example 1. Table 1 also shows the results of the printing performance evaluation.
Shown in

[0037]

Example 3 Mesoporous silica prepared in the same manner as in Example 1 except that methyltriethoxysilane was used instead of tetraethoxysilane in Example 1 was used as Sample 3. Δ, A4, and A4.8 were determined according to the above-described method, and are shown in Table 1. A recording sheet was obtained from this sample 3 in the same manner as in Example 1. Table 1 also shows the results of the printing performance evaluation.

[0038]

Example 4 4 g of the sample 1 obtained in Example 1 was weighed,
Dispersed in 70 ml of benzene. To this, 4 mmol of commercially available 3-aminopropylethoxysilane was added, and 48 hours 8
Heated to reflux at 0 ° C. The reaction product was subjected to extraction and removal of the hot benzene-soluble portion using a Soxhlet extractor for 24 hours.
Dried at 0 ° C. 160 ml of benzene was added to 4 g of this sample,
8 mmol of commercially available cinnamic acid chloride and 8 mmol of triethylamine were added, and the mixture was refluxed for 24 hours. The product was put into a Soxhlet extractor, and the benzene-soluble portion was extracted and removed for 24 hours, then washed with ethanol and dried at 80 ° C. under reduced pressure. This cinnamamidated mesoporous silica is referred to as Sample 4. Χ, A4, and A4.8 of this sample 4 were calculated under the same conditions as in Example 1, and are shown in Table 1. A recording sheet was obtained from Sample 4 in the same manner as in Example 1. Table 1 also shows the results of the printing performance evaluation.

[0039]

Example 5 10 g of the sample 2 obtained in Example 2 was weighed, and
00g. Here, commercially available zinc chloride (ZnCl
₂ ) was added and stirred at room temperature for 2 hours. Continue 11
Drying at 0 ° C. for 24 hours gave Sample 5. Χ, A of sample 5
4 and A4.8 were calculated under the same conditions as in Example 1, and are shown in Table 1. Sample 5 was treated in the same manner as in Example 1 to obtain a recording sheet, and a printing evaluation test was performed in the same manner. The results are shown in Table 1.

[0040]

Example 6 10 g of the sample 2 obtained in Example 2 was weighed and water 1
00g. 0.7 g of commercially available magnesium chloride (MgCl ₂ .6H ₂ O (manufactured by Wako Pure Chemical Industries, Ltd.)) was added thereto, followed by stirring at room temperature for 2 hours. Subsequently, Sample 6 was obtained by drying at 110 ° C. for 24 hours. Δ, A4, and A4.8 of Sample 6 were calculated under the same conditions as in Example 1 and are shown in Table 1. Sample 6 was treated in the same manner as in Example 1 to obtain a recording sheet, and a printing evaluation test was performed in the same manner. The results are shown in Table 1.

[0041]

Comparative Example 1 A recording sheet was obtained in the same manner as in Example 1, except that silica gel (Carplex 304N, trade name, manufactured by Shionogi Pharmaceutical Co., Ltd., average particle diameter 9 μm) was used in place of Sample 1. Table 1 shows the results of the printing performance evaluation. Table 1 also shows Δ, A4, and A4.8 of this silica gel.

[0042]

Comparative Example 2 A recording sheet was obtained in the same manner as in Example 1, except that silica gel (trade name: Cycilia 350, manufactured by Fuji Silysia Chemical Ltd.) was used in place of Sample 1. Table 1 shows the results of the printing performance evaluation. Also, シ リ カ ゲ ル, A of this silica gel
4 and A4.8 are also shown in Table 1.

[0043]

Comparative Example 3 A recording sheet was obtained in the same manner as in Example 1, except that silica gel (manufactured by Tokuyama, trade name X-37B) was used in place of the sample 1. Table 1 shows the results of the printing performance evaluation.
Shown in Table 1 also shows Δ, A4, and A4.8 of this silica gel.

[0044]

Comparative Example 4 Mesoporous silica was synthesized under the same conditions as in Example 1 except that the trimethylbenzene used in Example 1 was not used and the curing time was 12 hours. Table 1 shows Δ, A4, and A4.8. Using this mesoporous silica, a recording sheet was obtained in the same manner as in Example 1. Table 1 also shows the results of the printing performance evaluation.

[0045]

[Table 1]

[0046]

The recording sheet containing the ink absorbent of the present invention can form a printed matter having a high optical density and excellent water resistance and light resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H086 BA33 BA34 BA41 4G072 AA33 AA38 EE01 EE06 GG02 HH30 KK01 KK15 LL11 MM23 MM31 RR12 UU25

Claims (6)

[Claims] 1. An acid red 18, which is a water-soluble ink.
NMR spin of a mixture obtained by mixing a 10% by weight D ₂ O solution of the above and an ink absorbent in a 2: 1 weight ratio.
-The spin relaxation time is measured at 30 ° C. by the CPMG method, and the correlation between the obtained magnetization Mt and the elapsed time waiting time t immediately after the irradiation of the 90 ° pulse in the CPMG pulse sequence is optimized and calculated by the equation (1). An ink absorbent, wherein the obtained degree-of-constraint parameter χ is 0.1 or more. M _t = M ₀ [χexp (−t / T ₂ short) + (1−χ) exp (−t / T ₂ long)] (1) (where T ₂ short, T ₂ long, and A component with a short spin-spin relaxation time obtained by optimization calculation,
Component with long spin spin relaxation time (T ₂ short <T ₂ lon
g), and the constraint parameter (mol fraction of the proton component having T ₂ short in the two components). ) 2. An acid amount (A4) up to an acid strength function H0 = + 4.0 of 0.05 mmol / g or less, and an acid amount (A4.8) up to an acid strength function H0 = + 4.8, 0.
The ink absorbent according to claim 1, wherein the amount is 1 mmol / g or less. 3. The ink absorbent according to claim 1, wherein the ink absorbent according to claim 1 is mesoporous silica. 4. An ink receiver comprising the ink absorbent according to claim 1 and a binder. 5. An ink receiver slurry comprising the ink receiver according to claim 4 and a solvent. 6. A recording sheet obtained from the ink receptor slurry according to claim 5.