JPH11129610A - Ink jet recording sheet and method for ink jet printing using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet having a fast ink absorbing velocity and excellent fixability without generating a density unevenness in case of solid printing or dichroic printing. SOLUTION: In the ink jet recording sheet comprising at least two or more ink receptive layers each made of an aqueous soluble resin film on a transparent support, the outermost layer of the receptive layers is formed of an aqueous soluble resin having a pH of the aqueous solution of a solid content of 10 wt.% of 5.5 or less, and when a sheet is inclined at θ deg. (θ<=90), a liquid droplet of a pure water of Mμl is dropped on the receptive layer from above the sheet, the droplet is brought into contact with a surface of the receptive layer and then a distance of advancing down is Lcm, it satisfies the following formula: K=Lcos(πθ/10)/M (wherein K<0.275 (cm/μl)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording sheet suitable for forming an overhead transparent image using an ink jet recording apparatus and a recording method using the same.

[0002]

2. Description of the Related Art Ink-jet recording has been rapidly spread in recent years because of low noise, high-speed recording, and easy colorization. A water-based ink is used as the ink from the viewpoints of safety and printability. As the recording material, other than plain paper, a recording material having improved ink absorbency is used. As an ink jet recording material having improved ink absorbency, a recording material in which an ink receiving layer made of a water-soluble resin is provided on a support such as paper, a plastic film, or a glass plate is known. Overhead projector (OHP)
Many sheets used for applications are manufactured by coating (coating) a water-absorbing resin, particularly a water-soluble resin, on a support.

[0003] These OHP sheets are magenta, cyan,
A single color such as yellow does not cause a problem, but a mixed color of two colors such as red, blue and green causes uneven density in a printed image if ink absorbency is low. In addition, when a large number of ink dots overlap, that is, when the amount of ink adhered per unit area is large, uneven density occurs in the printed image.

As a method for solving this, printing is performed in a dedicated OHP sheet mode by dividing the printing mode into plain paper or dedicated paper. For example, a method of printing a second color dot by providing a time difference at a position overlapping with the first color dot (Japanese Patent Application Laid-Open No. 63-212155), a method of performing a printing operation for each ink a plurality of times (particularly) Kaihei 1-
264852). However, simply printing by these methods does not solve the problem of uneven density, and there is an urgent need to develop an OHP sheet that does not have such a problem, especially an ink receiving layer.

[0005] One of the problems as well as the density unevenness is fixability. As a means for solving this problem, a method has been proposed in which the pH of an aqueous solution containing 10% by weight of solid content of a resin used for an ink receiving layer is adjusted to 5 or less (Japanese Patent Application Laid-Open No. 7-81213). However, when the above-mentioned resin is used for all the ink receiving layers, the fixability of the ink is improved, but the amount of ink absorbed is reduced, and density unevenness occurs.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has a high ink absorption speed.
Further, an object of the present invention is to provide an ink jet recording sheet which is excellent in fixability and does not cause density unevenness in solid printing or two-color printing and is suitable for use in an overhead projector or the like.

[0007]

According to the present invention, first, there is provided an ink jet recording sheet comprising at least two or more water-soluble resin coatings on a transparent support. The outermost layer of the receiving layer has a solid content of 10
A wt% aqueous solution is made of a water-soluble resin having a pH of 5.5 or less, and the sheet is inclined by θ ° (θ ≦ 90), and Mμl of pure water droplets are dropped from above the sheet onto the receiving layer. ,
After the droplet contacts the surface of the receiving layer, the distance traveled downward is Lc
When m, an ink jet recording sheet satisfying the following formula (1) is provided.

K = Lcos (πθ / 180) / M (1) where K <0.275 (cm / μl)

Second, in the ink jet recording sheet described in the first aspect, the water-soluble resin in the outermost layer has either an acidic functional group or a quaternary ammonium-substituted acidic functional group. An ink jet recording sheet is provided.

Thirdly, in the ink jet recording sheet described in the first or second aspect, the sheet has an advancing contact angle with pure water in a range of 100 ° to 45 °, and
An ink jet recording sheet having a receding contact angle in a range of 90 ° to 25 ° is provided.

Fourth, the ink jet recording sheet has
In the color superimposing printing method, a second color dot is printed by providing a time difference at a position overlapping with the first color dot, using any one of the inkjet recording sheets described in the first to third aspects. Ink jet printing method is provided.

Fifth, the ink jet recording sheet has
In the color overlay printing method, using any one of the ink jet recording sheets described in the first to third, the first color dot is printed in a plurality of times, and the first color dot is printed in a position overlapping the first color dot. An ink jet printing method is provided wherein two color dots are printed in a plurality of times.

Hereinafter, the present invention will be described in detail. The ink jet recording sheet of the present invention is provided with an ink receiving layer composed of two or more water-soluble resin coating layers on a support, and the outermost layer on the innermost surface has a pH of an aqueous solution having a solid content of 10 wt%. Is 5.5 or less. Then, the measurement is further performed by a measurement method as illustrated in FIG.
It satisfies the following general formula (1). According to such a sheet, the above-mentioned density unevenness is suppressed, and excellent fixability is obtained.

K = Lcos (πθ / 180) / M (1) where K <0.275 (cm / μl) In the formula (1), M is the amount of pure water to be dropped (μl), L
Represents the distance (cm) that the liquid droplet traveled downward on the sheet, and θ represents the angle (°) at which the sheet was inclined.

The ink jet recording sheet of the present invention comprises:
By forming the receiving layer into a two-layer structure, the functions are separated, the dye is fixed in the outermost layer, and the ink is absorbed in the lower layer. Such a two-layer structure has the above-described effects. Is achieved. Therefore, a resin most suitable for fixing the dye is used for the outermost layer. For the lower layer, a resin most suitable for absorbing ink is used. As the resin of the outermost layer, the pH of the aqueous solution having a solid content of 10 wt% is 5.5.
It is the following water-soluble resin. Among them, those having either an acidic functional group or a quaternary ammonium substituent of the acidic functional group are most effective. The lower layer resin is a water-soluble resin, particularly a resin having a high ink absorbency, such as polyvinyl alcohol and its derivatives, and polyvinylpyrrolidone and its derivatives.

The ink jet recording sheet of the present invention comprises:
Having a water-soluble resin receiving layer consisting of two layers as described above,
Further, the sheet satisfies the expression (1) by a measuring method as exemplified in FIG. The measuring method in the present invention measures the speed at which the ink jet recording sheet used as the OHP sheet absorbs the aqueous ink. As shown in FIG. 1, the OHP sheet is placed on the stage 1 inclined at 65 °.
Paste the sheet 2 and pour pure water 3 right above the OHP sheet 2
0 μl is dropped, and the distance over which the pure water 3 in contact with the OHP sheet flows on the sheet 2 is measured.

The distance of pure water flowing becomes shorter as the water absorbing speed of the OHP sheet is higher, and the distance of flowing pure water becomes longer as the water absorbing speed is lower. Further, this measurement method indicates the speed at which the OHP sheet absorbs the droplets when a large number of droplets are simultaneously adhered, as compared with the case where the amount of adhesion per unit area is small.
The angle of tilting the seat is not limited to 65 °,
Also, the amount of pure water dropped can be sequentially changed by the OHP sheet.

Further, when the ink jet recording sheet of the present invention has an advancing contact angle with pure water of 45 to 100 ° and a receding contact angle of 25 to 90 °, the above-mentioned effects of density unevenness and fixability can be obtained. It can be further improved. That is, as a measure for examining the wettability between the inkjet recording sheet and the aqueous ink, a dynamic contact angle between the sheet and pure water can be considered. The advancing contact angle is suitably 45 to 100 °. If the advancing contact angle is 100 ° or more, the wettability with the ink is insufficient, and density unevenness occurs during solid printing or two-color printing. And the image density becomes insufficient. The receding contact angle is suitably from 25 to 90 °, and if it is 25 ° or less, the wettability is sufficient, but it becomes larger than required pixels and the image density becomes insufficient. Preferably, the receding contact angle with pure water is 30 to 85 °.

An embodiment of the present invention will be described below. The transparent support used for the ink jet recording sheet of the present invention is a plastic film or sheet of polyester, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene, polycarbonate, etc., paper, glass plate and the like. An appropriate one is selected from these supports depending on the application.

Next, the ink receiving layer of the ink jet recording sheet of the present invention comprises at least two or more water-soluble resin films. Of these, the function of the outermost layer is fixation of the dye, and the water-absorbing polymer,
In particular, it is a water-soluble resin, and the pH of an aqueous solution having a solid content of 10 wt% becomes 5.5 or less. Preferably pH 2
4 to 4 water-soluble polymers as main components. When the pH is 5.5 or more, the fixability of the ink using an anionic dye is particularly impaired, and when the pH is 2 or less, the coloring property may be impaired depending on the properties of the ink.

Examples include polyvinyl alcohol derivatives, polyacrylic acid, polyacrylic acid copolymers, polymethacrylic acid, and polyvinylpyrrolidone derivatives. Particularly, polyvinyl alcohol derivatives, polyvinylpyrrolidone derivatives, polyacrylic acid, and polyacrylic acid copolymers are exemplified. desirable. Polyvinyl alcohol derivatives, Polyvinyl bi Lori pyrrolidone derivatives -COOM, -SO ₃ M, -OSO
₃ M, -PO (OM) ₂ (where M represents hydrogen or quaternary ammonium) Modified polyvinyl alcohol, modified polyvinyl pyrrolidone, cation modified polyvinyl alcohol having at least one unit for a hydrophilic group selected from the group consisting of Is mentioned.

The function of the lower layer on the inner side of the outermost layer is absorption of ink, and the lower layer used for this is a water-absorbing polymer, especially a water-soluble resin such as polyvinyl alcohol and its derivatives, starch, casein. , Gum arabic, polyacrylamide, carboxymethylcellulose, polyacrylic acid, and polyvinylpyrrolidone, and polyvinyl alcohol and its derivatives, and polyvinylpyrrolidone and its derivatives are particularly desirable.

The polyvinyl alcohol has a saponification degree of 50 to
95% is suitable and desirably 60-90%. If it exceeds 95%, water resistance appears, but water absorption decreases. If less than 50%, the lipophilicity increases, which also decreases the water absorption. As the polyvinyl alcohol derivative, -COOM, -SO
Modified polyvinyl alcohol having at least one unit for a hydrophilic group selected from the group consisting of ₃ M, -OSO ₃ M, -PO (OM) ₂ (where M represents hydrogen or quaternary ammonium), and the like. . The saponification degree of these modified polyvinyl alcohol derivatives is also 50 to 95%.
Is suitable and desirably 60 to 90%.

[0022] Further, polyvinylpyrrolidone and its derivatives have high absorptivity which cannot be realized as a general polymer material. Polyvinylpyrrolidone has a molecular weight of 100
Those having a value of 00 to 400,000 are suitable. As a derivative of polyvinylpyrrolidone, a copolymer of polyvinylpyrrolidone and vinyl acetate is suitable. The vinylpyrrolidone / vinyl acetate ratio of the copolymer of polyvinylpyrrolidone and vinyl acetate is suitably from 7/3 to 3/7. It is also possible to mix and use these resins so as not to phase separate. The water-absorbing polymer used in the present invention is not limited to this.

As a method of providing an ink receiving layer made of a water-soluble resin on the support, the respective resin solutions may be formed by a known method such as a roll coater method or a blade coater method.
After coating on a support, it is dried and coated.

The ink receiving layer (both the outermost layer and the lower layer) is generally applied in a dry weight of about 0.6 to 14 g / m ² . If it is less than 0.6 g / m ² , the effect as an ink receiving layer does not appear. Conversely, if it is more than 14 g / m ² , the transparency is reduced, and the density is increased when the amount of ink adhered per unit area is large or small. Unevenness occurs.

The resin used in the ink receiving layer may contain various known additives to such an extent that the object of the present invention is not hindered. Such additives include glycerin, ethylene glycol, polyethylene glycol, a surfactant, an ultraviolet absorber, a pigment dispersant, a defoamer, a preservative, and a pH improve ink absorption performance.
Examples include fillers such as modifiers, silica, talc, clay, and alumina.

Next, the water-soluble ink used in the ink jet recording sheet of the present invention includes water-soluble dyes, water, wetting agents, surfactants, other water-miscible organic solvents (wetting agents, penetrants), preservatives, It consists of an agent and the like. As the water-soluble dye, a direct dye or an acid dye can be used. Specifically, as acid dyes and food dyes, C.I. I. Acid yellow 17,23,42,44,
79, 142 C.I. I. Acid red 1,8,13,14,18,
26, 27, 35, 37, 42, 52, 82, 87, 8
9, 92, 97, 106, 111, 114, 115, 1
34,186,249,254,289 C.I. I. Acid Blue 9,2 9,4 5,92,2
49 C.I. I. Acid black 1,2,7,24,26,
94 C.I. I. Food Yellow 3,4 C.I. I. Food Red 7, 9, 14 C.I. I. Food Black 1,2 As direct dye, C.I. I. Direct yellow 1,12,24,26,
33, 44, 50, 86, 120, 132, 142, 1
44 C.I. I. Direct red 1,4,9,13,17,
20, 28, 31, 39, 80, 81, 83, 89, 2
25,227 C.I. I. Direct orange 26,29,62,10
2 C. I. Direct blue 1,2,6,15,22,
25, 71, 76, 79, 86, 87, 90, 98, 1
63, 165, 199, 202 C.I. I. Direct Black 19,22,32,3
8, 51, 56, 71, 74, 75, 77, 154,
168,171.

Further, dyes newly developed for ink jet printing can of course be used. For example, Projet Fast Blac marketed by Zeneca
k2, Project Fast Magenta 2, P
rojet Fast Yellow 2, Projet
Fast Cyan 2 (registered trade name).
Many direct dyes are neutral (nonionic) dyes and form salts with metals, ammonium, etc.
When this is made acidic, what precipitates is preferred in the present invention. The amount of the dye is 1 to 10% by weight based on the total amount of the ink, and is appropriately determined depending on the color.

Surfactants are mentioned as additives for controlling the wettability between the OHP sheet and the ink.
Nonionic surfactants are desirable. In some cases, the surface tension of the ink does not decrease due to the interaction between the acid dye and the nonionic surfactant. In this case, it is necessary to further add an anionic surfactant. The amount of the surfactant added is from 0.01 to 3%, preferably from 0.5 to 1.5%, based on the total amount of the ink. If it is 0.01% or less, the surface tension does not decrease and the contact angle with OHP does not decrease. On the other hand, if it is 3% or more, the surface tension is too low, and the contact angle is too low.

Other penetrants added for the purpose of improving the liquid absorption property and adjusting the surface tension include diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether. And alkyl and aryl ethers of polyhydric alcohols such as tetraethylene glycol chlorophenyl ether, fluorine-based surfactants, acetylene-based surfactants, and lower alcohols such as ethanol and 2-propanol. Particularly preferred is diethylene glycol. Monobutyl ether.

In the ink used in the present invention, the following organic solvents can be used for the purpose of preventing drying of the ink and improving the dissolution stability. Ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, 1,2,4-
Polyhydric alcohols such as butanetriol, 1,2,3-butanetriol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether , Polyhydric alcohol alkyl ethers such as propylene glycol monoethyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2- Pyrrolidone, 2-pyrrolidone, 1,
Nitrogen-containing heterocyclic compounds such as 3-dimethylimidazolidinone and ε-caprolactam; amides such as formamide, N-methylformamide and N, N-dimethylformamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine; Amines such as diethylamine and triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol; propylene carbonate; ethylene carbonate; and γ-butyrolactone. These solvents may be used alone or in combination.

Examples of preservatives and fungicides include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate,
Sodium pentachlorophenol can be used.

As the pH adjuster, any substance can be used as long as it can adjust the pH to 7 or more without adversely affecting the prepared ink. Amines such as diethanolamine and triethanolamine,
Hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary
Quaternary ammonium hydroxides, quaternary phosphonium hydroxides, carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate.

Next, in the above-described method of printing on the ink jet recording sheet of the present invention, a printing method which does not cause density unevenness in two-color printing will be described. In the case of color ink jet recording, a two-color mixed (two-color superimposed) portion is a system realized by color superposition of a single color ink.
The amount of ink applied to the same pixel is 2 for a single color.
And the fixability is poor, and density unevenness is likely to occur. Therefore, the printing mode should be such that the ink is easier to dry and is easily absorbed by the ink jet recording sheet. In other words, the amount of one shot is reduced, or printing is performed after the ejected ink dots start drying. It has been found that printing in these modes can further suppress density unevenness. The print mode is described below as a specific example.

Mode 1 In the first scan, only one color is printed on the recording sheet. Immediately after the scan, the first color dot is superimposed on the first color dot, and the first scan is performed without printing the second color dot. finish. After the completion of the first scan, the print head returns to the start of the line. The scanning is further repeated to print the same color dot on the already printed dot or to print a different color dot on the already printed dot. In each case, a total of two ink droplets are printed, and the two printings print one color dot on the other color dot. Since the absorption of the first color dots into the medium has started within the time required for the print head to return to the line start point after the completion of the first scan, the density unevenness occurs even when the second color dots are printed. Does not occur.

Mode 2 In this example, the original one pixel is printed by decomposing the ink adhering amount (Mj) forming one pixel into a plurality of parts and printing a plurality of times. During the first scan, only one color is M
1 / n of j is printed on the recording sheet, and then, immediately after scanning, is superimposed on the first color dot, and 1 of the second color dot is printed.
/ N is printed on the recording sheet. After the completion of the first scan, the print head returns to the start of the line. The scanning is further repeated, and 1 / n of Mj of the first color is printed on the recording sheet on the already printed dots. 1 / n of the dot Mj is printed on the recording sheet. The ink is absorbed by the OHP sheet within this one scanning time. This printing operation is repeated n times, and printing is completed.
Since the ink is absorbed during one scan, the dot diameter does not increase when printing n times.

Mode 3 In this example, the original one pixel is printed by decomposing the ink adhering amount (Mj) forming one pixel into a plurality and printing a plurality of times. During the first scan, only one color is M
1 / n of j is printed on the recording sheet, and then immediately after the scanning, the first color dot is superimposed, and the first scanning is completed without printing the second color dot. The print head returns to the start of the line. Further, the scanning is repeated, the first color dot is superimposed on the already printed dot, only 1 / n of Mj is printed on the recording sheet, and the printing is performed n times. One color dot is completed.
The ink is absorbed into the ink jet recording sheet within one scanning time. After that, the second color is printed on the completed first color dot in the same manner by dividing it into n times, and the two-color superimposed color dot is completed. Since the ink is absorbed during one scan, the dot diameter does not increase when printing n times.

Mode 4 A unit of data is decomposed into a plurality of data in the sub-scanning direction and is performed based on each data. At the time of the first scan, 1 / n of the first color data is printed. The first scan ends without printing. After the first scan is completed, the process returns to the print head line start point. Further scanning is repeated, and the non-printed 2 / n divided in the sub-scanning direction
Print the data. By repeating this scanning n times, the first color data (first color line) in the sub-scanning direction is printed. Thereafter, the second color data is also printed in the same manner as the first color data so as to be superimposed on the printed first color line, and the color line of the two-color mixture is completed.

Mode 5 A unit of data is decomposed into a plurality of units in the sub-scanning direction and is performed based on each data. At the time of the first scan, 1 / n of the first color data is printed. 1 / n of the second color data is printed, and the first scan ends. After the completion of the first scan, the print head returns to the start of the line. The scanning is further repeated to print the unprinted first color data divided in the sub-scanning direction and then 2 / n data of the second color data to be superimposed next. By repeating this scanning n times, the color line of the two-color mixture of the first and second color data in the sub-scanning direction is completed.
The print mode used in the present invention is not limited to this.

[0039]

【Example】

<< Preparation of Receptor Layer Forming Solution >> Preparation of Polyvinyl Alcohol Solution Cation-modified polyvinyl alcohol (PVA substituted by quaternary ammonium: (degree of saponification: 85%, manufactured by Kuraray Co., Ltd.)) is dissolved in water, and cation having a solid content of 10 wt% A modified polyvinyl alcohol aqueous solution was prepared. Preparation of Polyacrylic Acid Aqueous Solution A polyacrylic acid solution (25%: manufactured by Wako Pure Chemical Industries, Ltd.) was diluted with pure water to prepare a polyacrylic acid aqueous solution having a solid content of 10 wt%. Preparation of polyacrylic acid copolymer aqueous solution The polyacrylic acid copolymer (solid content: 40%, manufactured by Nippon Pure Chemical Co., Ltd.) is diluted with pure water, and an aqueous solution of the polyacrylic acid copolymer having a solid content of 10 wt% is prepared. Prepared. Preparation of polyvinylpyrrolidone solution Polyvinylpyrrolidone (manufactured by ISP) is dissolved in water,
An aqueous solution of polyvinylpyrrolidone having a solid content of 10 wt% was prepared. Preparation of aqueous sodium polyacrylate solution A sodium polyacrylate solution (30%, manufactured by Nippon Shokubai Co., Ltd.) was diluted with pure water to prepare an aqueous sodium polyacrylate solution having a solid content of 10 wt%.

<< Preparation of Ink-Jet Recording Sheet >> One surface of a 50 μm-thick polyethylene terephthalate (PET) film was subjected to a surface treatment by plasma treatment.
The above-mentioned polyvinyl alcohol solution or polyvinylpyrrolidone solution was applied and dried to obtain a lower layer.
Further, a cation-modified polyvinyl alcohol, polyacrylic acid, polyacrylic acid copolymer aqueous solution or the like was applied thereon and dried to obtain a target ink jet recording sheet.

<< Evaluation of Inkjet Recording Sheet >> Dynamic Contact Angle Measurement The dynamic contact angle of the prepared ink jet recording sheet with pure water was measured with a dynamic contact angle measuring device (manufactured by Orientex). Printing the thermal ink jet system, magenta by the inkjet printer of piezo inkjet system, yellow,
Cyan ink was solid-printed on a recording sheet in a range of 5 × 5 mm (two-color printing: red, green, blue). Prescription of magenta, yellow, and cyan ink Magenta: Direct red 227 2 wt%, diethylene glycol / glycerin (= 3/1) 20 wt
%, Surfactant 1% by weight, antiseptic / antifungal agent 0.4% by weight Cyan: Fast cyan 3% by weight, diethylene glycol / glycerin (= 3/1) 20% by weight, surfactant 1% by weight, antiseptic / antifungal agent 0.4% by weight yellow : Fast yellow 2 / Direct
yellow142 2 wt%, diethylene glycol / glycerin (3/1) 20 wt%, surfactant 1 wt
%, Antiseptic and fungicide 0.4 wt% Printing mode Printing was performed in the printing modes 1, 2, and 4 described above. Density non-uniformity Actually projected by OHP, ○ indicates that there was almost no density non-uniformity at the time of projection, Δ indicates that there was a little, and x otherwise. One minute after the two-color printing of the solid fixability , a filter paper was placed on the printing portion, a load of 20 g / cm was applied thereon, and the evaluation was made based on the presence or absence of ink transfer to the filter paper.

Examples 1 to 6 and Comparative Examples 1 to 5 Ink jet recording sheets having the constitutions and components shown in Tables 1 and 2 were prepared and evaluated. Tables 3 and 4 show the evaluation results.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

In the table, the print mode x is a mode in which a secondary color (two colors) is printed in one scan when two-color printing is performed.

As can be seen from Tables 3 and 4, the water-soluble resin having a specific range of pH value is used for the outermost layer of the receiving layer, and the sheet of the example having a specific K value has suppressed density unevenness and excellent fixability. It can be seen that it is more preferable to have the advancing contact angle and the receding contact angle in the ranges specified in the present invention.

[0049]

As described above, according to the ink jet recording sheet of the present invention, it is possible to improve the density unevenness at the time of two-color mixing and obtain excellent fixability by two-color printing. Further, according to the printing method of the present invention using the sheet, when printing a mixed color of two colors on the sheet, the density unevenness at the time of two-color mixing is improved.

[Brief description of the drawings]

FIG. 1 is a diagram (side view) for explaining a method of measuring a speed at which ink of an ink jet recording sheet absorbs ink.

[Explanation of symbols]

 Reference Signs List 1 stage 2 inkjet recording sheet 3 pure water droplet

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akiko Konishi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Masayuki Kogano 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Inside Ricoh Company (72) Inventor Takanori Tsukiki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Ikuko 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company

Claims (5)

[Claims] 1. An ink jet recording sheet comprising at least two layers of a water-soluble resin coating on a transparent support, wherein the outermost layer of the receiving layer is an aqueous solution having a solid content of 10% by weight. Is made of a water-soluble resin having a pH of 5.5 or less, and the sheet is tilted by θ ° (θ ≦ 90), and M μl of pure water droplets are dropped on the receiving layer from above the sheet to form droplets. An ink jet recording sheet characterized by satisfying the following expression (1) when the distance traveled downward after contacting the surface of the receiving layer is Lcm. K = Lcos (πθ / 180) / M (1) where K <0.275 (cm / μl) 2. The ink jet recording sheet according to claim 1, wherein the water-soluble resin in the outermost layer has either an acidic functional group or a quaternary ammonium substituent of the acidic functional group. Sheet. 3. The ink jet recording sheet according to claim 1, wherein the sheet has a forward contact angle with pure water in the range of 100 to 45 ° and a receding contact angle of 9 °.
An ink jet recording sheet having a range of 0 to 25 °. 4. A method for performing two-color superimposition printing on an ink jet recording sheet, comprising using the ink jet recording sheet according to claim 1 and providing a time difference at a position overlapping the first color dot. An ink-jet printing method characterized by printing the following color dots. 5. A method for printing two colors on an ink jet recording sheet, wherein the first color dots are printed in a plurality of times by using the ink jet recording sheet according to any one of claims 1 to 3; An ink-jet printing method, wherein a second color dot is printed in a plurality of times at a position overlapping with one color dot.