JPH10305657A - Ink-jet recording sheet and method for printing on the sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording sheet for water ink which absorbs ink fast and can obtain good print images, by providing an ink-receiving layer on a supporting body, and setting a K-value of the ink-receiving layer expressed by a specific formula to be smaller than a specific value. SOLUTION: An ink-receiving layer of polyvinyl alcohol and its derivative, etc., is set on a supporting body of an ink-jet recording sheet. A K-value (indicating a level of absorption of water ink) of the ink-receiving layer expressed by a formula K=L × cos (π× θ/180)/M is smaller than 0.275 cm/μl. In the formula, L is a distance (cm) of drops of Mμl deionized water dropping downward after coming in touch with the sheet from above the sheet inclined by an angle θ deg. (θ<=90). Accordingly, the recording sheet with which a density irregularity at mixing multiple colors can be prevented is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, in particular, an over head projector (0H).
The present invention relates to an aqueous inkjet recording sheet suitable for use in P) and the like and a method for printing on the sheet.

[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. As ink,
Water-based inks are used from the viewpoint of safety and recording suitability. As the recording material, in addition to 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. Among these, many OHP sheets are manufactured by coating (coating) a water-absorbing resin, particularly a water-soluble resin, on a support. These OHP
The sheet is not considered to be a problem with a single color such as magenta, cyan, and yellow. However, with a mixed color of two colors such as red, blue, and green, unevenness in the density of a printed image occurs when 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 separately from a mode for printing on plain paper and 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 Laid-Open No.
JP-A-3-312155), a method in which the printing operation is performed by dividing the printing operation into a plurality of times for each ink (JP-A-1-264852).
Is disclosed. However, at present, the problem of density unevenness has not been solved simply by printing using these methods.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a water-based ink which has a high ink absorption speed and can provide a good printed image (without density unevenness in solid printing or multicolor printing, for example, in two-color printing). It is an object of the present invention to provide a recording sheet for aqueous ink suitable for use in a recording material for recording, particularly an overhead projector (hereinafter, also referred to as OHP), and a method for printing on the sheet.

[0004]

The ink jet recording sheet of the present invention comprises an ink receiving layer provided on a support as shown in FIG. 2, and the ink receiving layer has the following formula (I).
The K value (representing the degree of absorption of the water-based ink) represented by the formula (1) is less than 0.275 (cm / μl), which satisfies the requirement.

K = L × cos (π × θ / 180) / M (I) [where L is the angle of the sheet inclined at θ ° (θ ≦ 90) and Mμ1 pure water from above the sheet The distance (cm) that the droplet hangs down and travels downward after contacting the sheet. ]

FIG. 1 is a schematic diagram of the K value measuring device. As shown in FIG. 1, an OHP sheet was stuck on the stage inclined at 65 °, and pure water was applied from directly above the OHP sheet.
0 μl was dropped, and the flow distance of pure water in contact with the OHP (c
m) is measured. The value of the K value is such that the higher the water absorption speed of the OHP sheet, the shorter the distance of pure water flowing,
The lower the water absorption rate, the longer the flowing distance. This measurement method also expresses the rate at which the OHP absorbs when a large number of droplets adhere simultaneously, rather than when the amount of adhesion per unit area is small. The inclination angle of the sheet that can be employed in measuring the K value is not limited to 65 °, and the amount of pure water dropped can be changed according to the type of the OHP sheet.

Further, as a measure for examining the wettability between the ink receiving layer and the aqueous ink, a dynamic contact angle between the OHP sheet and pure water can be considered. Its advancing contact angle is 45-100 °
Is appropriate. If the contact angle is 100 ° or more, the wettability with the ink is insufficient and solid printing, density unevenness occurs at the time of two-color printing, and if the contact angle is 45 ° or less, the wettability is sufficient. And the image density becomes insufficient. Preferably, the contact angle with pure water is 45 to 90 °. The advancing contact angle is a dynamic contact angle at the time of transition from the air to the water, and is used to evaluate the reorganization behavior of the molecular chains on the material surface.

The receding contact angle is suitably from 25 to 90 degrees. When the receding contact angle is 90 ° or more, the wettability with the ink is insufficient and solid printing, density unevenness occurs at the time of two-color printing, and when the angle is 25 ° or less, the wettability is sufficient. And the image density becomes insufficient. Preferably, the receding contact angle with pure water is 30 to 85 °. The receding contact angle is a dynamic contact angle at the time of transition from water to air, and is used to evaluate the reorganization behavior of the aggregation state of molecular chains on the material surface.

As the support of the ink jet recording sheet used in the present invention, a plastic film or sheet of polyester, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene, polycarbonate, etc., paper, glass plate and the like are used. An appropriate one is selected from these supports depending on the application. The ink receiving layer of the OHP sheet used in the present invention includes a water-absorbing polymer, particularly a water-soluble resin, such as polyvinyl alcohol and its derivatives, starch, casein, gum arabic, polyacrylamide, carboxymethylcellulose, polyacrylic acid, and polyvinylpyrrolidone. In particular, polyvinyl alcohol and its derivatives, and polyvinylpyrrolidone and its derivatives are desirable. Polyvinyl alcohol having a saponification degree of 50 to 95% is suitable, and preferably 60 to 90%. If it exceeds 95%, water resistance appears, but water absorption decreases. Also 50
%, The lipophilicity increases, which also reduces the water absorption. The derivative of polyvinyl alcohol is -C
_{OOM, -SO 3 M, -OSO 3} M, -PO (OM)
₂ (where M represents hydrogen, lithium, sodium or potassium); modified polyvinyl alcohol having at least one unit for a hydrophilic group selected from the group consisting of tertiary amines, quaternary ammonium salts, and betaine; No.

In many cases, the aqueous ink uses a cationic or anionic pigment or dye as a component.
For example, an aqueous ink containing a cationic pigment or dye is strongly linked to an anionic modified polyvinyl alcohol, and thus has excellent ink adsorbability. Similarly, an aqueous ink containing an anionic pigment or dye is strongly linked to a modified cationic polyvinyl alcohol, and thus has excellent ink adsorbability. The saponification degree of these modified polyvinyl alcohol derivatives is also 50 to 95%.
Is suitable, preferably 60 to 90%.

[0010] In addition, polyvinylpyrrolidone and its derivatives have high absorptivity that cannot be realized as a general polymer material. Polyvinylpyrrolidone has a molecular weight of 10.0
Those having a size of from 00 to 400,000 are suitable. As a derivative of polyvinylpyrrolidone, a copolymer of polyvinylpyrrolidone and polyvinyl acetate is suitable. The vinylpyrrolidone / vinyl acetate ratio of the copolymer of polyvinylpyrrolidone and vinyl acetate is suitably from 7/3 to 3/7. However, the water absorbing polymer used in the present invention is not limited to the above.

As a method for providing an ink receiving layer made of a water-soluble resin on the support, the respective resin solutions are coated on the support by a known method such as a roll coater method or a blade coater method, and then dried and coated. I do. The ink receiving layer is generally coated at a dry weight of about 0.6 to 14 g / m ² . If the amount is less than 0.6 g, the effect as an ink receiving layer does not appear. Conversely, if the amount is more than 14 g, the transparency decreases, and furthermore, density unevenness occurs when the amount of ink adhered per unit area is large or small.

The resin used for the ink receiving layer includes:
Various known additives can be added to such an extent that the achievement of the object of the present invention is not hindered. Such additives include glycerin, ethylene glycol, polyethylene glycol, a surfactant,
Examples include ultraviolet absorbers, pigment dispersants, defoamers, preservatives, pH adjusters, and fillers such as silica, talc, clay, and alumina. The aqueous ink used in the recording material of the present invention may be a conventional aqueous ink. Examples of the aqueous ink include water-soluble dyes, water, wetting agents, surfactants, other water-miscible organic solvents, and preservatives. It becomes.

The two-color mixture (2
Since the (color superimposition) portion is a method realized by color superimposition of single color ink, the amount of ink to be applied to the same pixel is twice as large as that of a single color, and fixability and density unevenness are likely to occur. Therefore, the printing mode should also make the ink easier to dry and absorb into the base sheet. That is, in the print mode, for example, the amount of one shot is reduced, or printing of a color different from the color of the shot ink is performed after the shot ink dots start drying. It has been found that printing in these modes can further suppress density unevenness. Therefore, the two-color printing in the present invention means (R, G, B,
(Mixed two colors) is printed in a large number of times. As a specific example, a printing mode in the case of two-color mixing (two-color overlapping) employed in the present invention will be described below.

Mode 1 In this example, only one color is printed on the recording sheet at the time of the first scan, and is superimposed on the first color dot immediately after the scan, and the first color dot is printed without printing the second color dot. Is completed. After the completion of the first scan, the print head returns to the line start point. Scanning is repeated, and dots of the same color are printed on already printed dots, or
Alternatively, a different color dot is printed 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. First
Since the absorption of the first color dot 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 second scan, the density unevenness even when the second color dot is printed. Does not occur.

Mode 2 In this example, the amount of ink adhering (M
j) is decomposed into a plurality of parts, and the original one pixel is printed by printing a plurality of times. At the time of the first scan, only one color prints 1 / n of Mj on the recording sheet, and then, immediately after the scan, overlaps the first color dot and records 1 / n Mj of the second color dot. Print on the 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. This printing operation is repeated n times, and printing is completed.

Mode 3 In this example, the original one pixel is printed by decomposing the ink adhesion 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 the scanning, the first color dot is superimposed, and the first scanning is completed without printing the second color dot. The printhead 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.
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.

Mode 4 In this example, the data unit is divided into a plurality of data in the sub-scanning direction and is performed based on each data. In the first scan, 1 / n of the first color data is printed, and immediately after the scan, , The first scanning is completed without printing. After the completion of the first scan, the print head returns to the start of the line. Further, the scanning is repeated, and the unprinted 2 / n data divided in the sub-scanning direction is printed. 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 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 In this example, the data unit is divided into a plurality of data in the sub-scanning direction and is performed based on each data. In the first scan, 1 / n of the first color data is printed, and immediately after the scan, Is printed over 1 / n of the second color data, and the first scan is completed. After the completion of the first scan, the print head returns to the line start point. 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 first in the sub-scanning direction,
The color line of the two-color mixture of the second color data and the second color data is completed. The printing mode used in the present invention is not limited to this, and for example, the two-color mixing (2
Not only in the case of (color superposition), but also in the case of multi-color mixing (multi-color superposition) of two or more color mixing (two-color superposition), it can be performed in the above-described respective modes.

[0019]

Embodiments of the present invention will be described below.

Examples 1 to 6 and Comparative Examples 1 to 5 (1) Preparation of polyvinyl alcohol solution and polyvinyl pyrrolidone solution The polyvinyl alcohol solution was prepared by dissolving polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) in water (warm water) and adding 10 wt% A polyvinyl alcohol aqueous solution was prepared. The polyvinylpyrrolidone solution was prepared by dissolving polyvinylpyrrolidone (manufactured by ISP) in water to prepare a 10 wt% polyvinylpyrrolidone aqueous solution. (2) Production of recording material Polyethylene terephthalate (PET) having a thickness of 50 μm
After one surface of the film was subjected to a surface treatment such as UV-O ₃ treatment or plasma treatment, the above-mentioned polyvinyl alcohol solution or polyvinyl pyrrolidone solution was applied and dried to obtain a target recording material.

(3) Evaluation of Recording Material Dynamic Contact Angle Measurement The advancing contact angle (°) and the receding contact angle (°), which are the dynamic contact angles of the produced recording material with pure water, are dynamic contact angle measuring devices. (Orientex). (4) Printing Magenta, yellow,
Cyan was solid-printed (two-color printing: red, green, yellow) in a range of 5 × 5 mm on the recording material. (5) Print mode Printing was performed in the above print modes 1, 2, and 4. (6) Density non-uniformity Actually projected with OHP, Δ was given when there was almost no density unevenness at the time of projection, Δ was given when there was slight density unevenness, and x was given when others were not.

Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Table 1 below.
The ink receiving layer shown in Table 2 was prepared and evaluated on a polyester support as described above, and the evaluation results are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2] Comparative Example 1 corresponds to Example 1 Comparative Example 2 corresponds to Example 2 Comparative Example 3 corresponds to Example 3 Comparative Example 4 corresponds to Example 4 Comparative Example 5 corresponds to Example 5 Printing of Table 2 The X in the mode is not to be performed in the mode described in the first aspect, but to continue printing a single color during one scan as in the related art.

[0025]

(1) Claims 1 to 3 It is possible to provide a recording sheet in which the density unevenness at the time of multicolor mixing is improved. (2) Claims 4 and 5 It is possible to provide a printing method in which the density unevenness at the time of multicolor mixing is improved when printing a multicolor mixture on a recording sheet.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for measuring a K value.

FIG. 2 is a schematic sectional view of the ink jet recording sheet of the present invention.

 ──────────────────────────────────────────────────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] The K value represented by the following formula (I) is 0.275
An ink jet recording sheet comprising an ink receiving layer having a density of less than (cm / μl) formed on a support. K = L × cos (π × θ / 180) / M (I) [where L is the angle of the sheet inclined at θ ° (θ ≦ 90), and Mμ1 pure water from above the sheet. The distance (cm) that the droplet hangs down and travels downward after contacting the sheet. ] 2. The advancing contact angle of the ink receiving layer with pure water is 4
2. The ink jet recording sheet according to claim 1, wherein the angle is in the range of 5 [deg.] To 100. 3. The receding contact angle of the ink receiving layer with pure water of 2
3. The ink jet recording sheet according to claim 1, wherein the angle is in the range of 5 [deg.] To 90. 4. The printing method according to claim 1, wherein the color dots are overprinted with a time difference between the color dots. 5. The printing method according to claim 1, wherein at least one color dot is overprinted in a plurality of times in the method of performing two-color printing on a recording sheet according to claim 1, 2 or 3.