JPH0216079A - Recording medium - Google Patents

Abstract

PURPOSE:To improve ink absorptivity, image color properties, and image density and to prevent powder scattering by using a recording medium containing the same fiber substance in the vicinity of the surface of an ink accepting layer and having a roughness index of the surface of the ink accepting layer more than a specified value. CONSTITUTION:To obtain resistance to bleeding, it is required that an ink accepting layer has a roughness index of 10ml/m<2> or more and a Bekk smoothness of 20sec. or less according to the measurement by a Bristol tester. For example, a filter paper used as a base is coated with a liquid mixed with silica, water resisting agent, and polyvinyl alcohol water solution and dried to obtain a recording medium having a roughness index of 22ml/m<2> and a Bekk smoothness of 2sec. In this manner, the obtained medium is free from bleeding even in the printing of a graph or the like using a large ink typing amount and powder scattering even if the surface is rubbed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording material suitable for use in inkjet recording methods as well as pencils, ballpoint pens, felt-tip pens, fountain pens, crayons, and the like.

[Conventional technology]

Conventional recording materials for inkjet use include: (1) paper made from ordinary pulp-based paper to a low size, such as filter paper or blotting paper, and (2) paper on the base material. It is known that the coating amount is determined by using a porous pigment such as silica or zeolite that has a large oil absorption capacity and adsorbs the coloring components in the ink.

Recording material (1) can be produced at a low cost, but although it has excellent ink absorption, the ink penetrates deeply into the fiber layer of the paper, resulting in poor color development of the colorant in the ink (also, the ink does not penetrate the paper surface). Because it is absorbed along the fibers, a phenomenon called feathering occurs, and the dots become jagged instead of circular, and the dots become too large, resulting in a decrease in resolution and the inability to obtain high-quality images. was there.

For this reason, such uncoated paper has been used for applications that do not necessarily require images with relatively low resolution (or high density), such as monochrome recording and personal computer terminals.

Conventionally, for the recording material (2), for example, JP-A-58-1
As disclosed in Japanese Patent Application Laid-open No. 32586 and Japanese Patent Application Laid-Open No. 59-35977, coated paper based on relatively high-sized paper (such as commercially available high-quality paper) has been used.

In such coated paper, the ink absorbing layer is porous and uniform, so that it is possible to obtain a paper with appropriate ink absorbency and excellent dot shape and resolution.

However, in a recording method that requires a color image of higher quality and resolution, it is necessary to absorb and fix a larger amount of ink at high speed.

Conventionally, this has been dealt with by increasing the coating amount of the ink absorbing layer and increasing the void volume. Upon contact, a problem arises in which the coating layer peels off from the base paper, which is called powder shedding.Such paper powder not only stains the inside of the device, but also causes nozzle clogging in the inkjet head, which is a particular problem.

Furthermore, because a large amount of the coating solution must be rapidly dried during the manufacturing process, the binder in the coating solution undergoes migration, resulting in a severe decrease in the strength of the coating layer and ink absorption. These problems can be solved to some extent by making the drying conditions more gentle or, for example, by varying the number of times of coating, but in this case, there is also the problem of increased manufacturing costs.

As a method to solve these drawbacks, there is a method of using paper with a low size degree as a base paper and providing a porous pigment layer thereon. A recording material having a coating layer containing silica having specific physical properties on a base paper of 4 seconds or less is exemplified.

This type of recording material has the advantage that even when a relatively thin ink-receiving layer is provided, a recording material with excellent ink absorption properties can be obtained.

However, even with such recording materials, a large amount of ink penetrates deeply into the base paper, resulting in low print density.The ink-receiving layer is thin and cannot hold much ink, so when ink is absorbed at the interface, , resolution and print quality may deteriorate due to poor dot shape or excessive bleeding of attached ink droplets as mentioned in the above-mentioned recording material (1), and in the case of slightly coated paper, printing If you rub the printed area with your hand or a roller immediately afterward, it will not get dirty, but a unique phenomenon of ink oozing (bleeding) will occur.

During coating, the binder in the coating solution is absorbed by the low-size base paper, resulting in powder falling on the surface despite the thin coating layer.Indoor discoloration of images (mainly black discoloration to colored). Therefore, there are problems such as extremely poor image storage stability.

As described above, at present, no inkjet paper has been found that satisfies all of the above-mentioned requirements.

[Problem that the invention attempts to solve]

SUMMARY OF THE INVENTION Therefore, the purpose of the present invention is to solve the above-mentioned drawbacks, to have extremely excellent absorbency of water-based ink, and to solve the problem of ink seepage (bleeding) that is unique to slightly coated paper.
It is an object of the present invention to provide a recording material suitable for inkjet use, which is excellent in dye color development and indoor storage stability, is inexpensive, and does not cause powder falling.

[Means and effects for solving the problems] The above objects are achieved by the present invention as described below.

That is, the present invention provides a recording material in which an ink-receiving layer is provided on a base paper, in which the fibrous material of the base paper is present in the vicinity of the surface of the ink-receiving layer, and the ink resistance measured with a Bristow tester is The roughness index of the receptor layer surface is 10 m I! /
This recording material is characterized in that it has a length of 15 mm or more, more preferably 15 m 172 or more. According to the above configuration, the ink absorption is extremely good, and the color quality of the recorded image is 9.
An inexpensive recording material with excellent image density and no powder falling can be obtained.

By the way, conventional printers have a printing density of 2 at most.
00 dpi, but recently, in order to increase the resolution of printed images, higher densities such as 360 dpi are progressing. In addition, the uses of color printers have expanded, and in addition to text and pictures, the use of so-called business color, such as graphs and diagrams, has rapidly increased. graph,
The type of illustration requires a large amount of ink compared to each character. As a result, ink oozes out (bleeding) due to insufficient absorbency at color boundaries. Bleeding occurs equally for all colors, but particularly from dark colors to light colors (for example, from black to yellow), it significantly degrades image quality.

However, bleeding does not occur with heavy coated paper or filter paper, but is a problem specific to many lightly coated papers. In order to solve these problems, we prototyped various slightly coated papers, and selected those with good bleeding resistance and those with poor bleed resistance.
Size degree (JIS-P-8140).

It was investigated using Klemm's water absorbency (JIS-P-8141) and Stekicht size (JIS-P-8122).

However, with Cobb size, it is impossible to measure because the liquid penetrates to the back surface instantly after contact, and with Klemm water absorption, the height of water absorption did not change for both 1 minute and 10 minutes.

Also, regarding the Steckcht size degree, since most of the base papers of the slightly coated papers were weak size or no size paper, all of them had a Steckcht size degree of 5 seconds or less, and no difference occurred.

These results indicate that bleeding is not due to differences in the absorption capacity of paper with a contact time of 15 seconds or more (
In the case of the Cobb method, JIS requires liquid contact for 60 seconds, but depending on the skill level of the measurer, it is possible to measure up to about 15 seconds after contact with liquid, so high absorption type paper such as inkjet paper can be measured. We keep the contact time as short as possible. ). Recently, as a method to measure the instantaneous absorption rate,
There is a liquid absorption test method for paper and paperboard using the Bristow method registered in Tappi (Japan Ta
ppi paper, pulp test method No. 5l-87).

To briefly explain the principle of the Bristow tester, the paper to be tested is wrapped around the circumference of a disk and rotated at a given speed. A headbox containing a known amount of liquid is gently placed on the paper. The headbox has a slit of constant width through which the liquid penetrates into the irregularities on the surface of the paper and, depending on the speed, into the interior of the paper. By keeping the amount of liquid constant and changing the speed of the disk, the contact time and liquid absorption capacity (transfer amount) can be determined from the area of ink transferred to the paper at that time.

Depending on the type of paper, the size of the disk (usually the circumference is 100 mm)
From the 100O and the speed, the maximum measurable contact time is around 2 seconds. It is known that the amount of liquid transferred and the contact time are correlated with the square root of time.

In a graph where the vertical axis is the amount of liquid dislocation and the horizontal axis is the square root of the contact time, the slope of the straight line is the absorption coefficient (permeation coefficient), 0.
The value in seconds is taken as the roughness index. The roughness index is calculated by extending the value of the amount of dislocation at the time of wetting time for liquids that require wetting time (those with large contact angles), and by extending the value of the amount of dislocation at the time of wetting time. For angles close to 0, it can be found by extending a straight line. Although the absorption coefficient differs depending on the liquid, the roughness index does not change even if the liquid is changed, and is a unique value of paper, as shown in References J and A.

Bristow: 5vensk Papers
tidn, 70 (19).

623 (1967).

Using a Bristow tester (dynamic permeability tester, Toyo Seiki model, measurement conditions will be described later), we measured those with good bleeding resistance and those with poor bleeding resistance. The value of this roughness index is 10 mj! All of them were very large, /rrr. Furthermore, when the Bekk smoothness and surface roughness of the surface of paper with a roughness index of 10 m1/rd or more were measured, it was found that the surface of both papers was non-smooth compared to bleeding paper.

Bleeding does not occur when the amount of initial metastasis is large, but only when it is small. Since the initial amount of transfer is determined by the absorption coefficient and roughness index, it is thought that paper with a large roughness index, or paper with a large absorption coefficient even if the roughness index is small, is advantageous in terms of bleeding resistance.

Next, the configuration of the present invention will be described below.

The base paper of the present invention has Bekk smoothness (JIS-P-8119)
It is desirable for the paper to have a heating time of 20 seconds or less, more preferably 10 seconds or less, and a Steckigt size degree of 15 seconds or less, more preferably 5 seconds or less. Paper with a smoothness greater than 20 seconds has fewer pores on the surface regardless of the amount of coating and the type of coating layer, so the roughness index becomes less than 10 ml/rd, causing bleeding. do.

Furthermore, when the Steckigt sizing degree of the base paper is greater than 15 seconds, the ink absorption is poor, so that the coating layer is relied upon to absorb the ink, and the coating layer must be made thicker.

Regarding the coating layer, all conventionally known pigments can be used for the coating layer, but silicon-containing pigments are suitable because they are excellent in whiteness, coloring properties of dyes, etc.

Regarding the binder, any conventionally known water-soluble or water-dispersible binder may be used, but polyvinyl alcohol is mainly used in view of the storage stability of the recording material, the color development of the dye, and the ease of coating. What you did is amazing. The ratio of these pigments to the binder is preferably 5:1 to 1:3, more preferably 3:1 to 1:2. 5:1
If the pigment ratio is higher than that of the pigment, the viscosity of the coating liquid will be high, making coating difficult and causing powder to fall off easily. If the binder content is greater than 1:3, the paper will have extremely poor ink absorbency. Furthermore, additives such as a waterproofing agent, a fluorescent whitening agent, a surfactant, a pH adjuster, an antifoaming agent, and an ultraviolet absorber may be added as necessary.

All methods such as a bar coater, blade coater, air knife coater, reverse coater, gate roll coater, and pigment size press method can be used to coat the base paper with the aqueous coating liquid obtained by mixing the above-mentioned materials. However, among these, bar coaters can supply the most stable recording material.

An ink-receiving layer containing a pigment is provided on the base paper shown above, but at this time, in order to reflect the roughness of the base paper even after the ink-receiving layer is coated, the fibrous material of the base paper is placed near the surface of the ink-receiving layer. It is best to apply the coating to the extent that it exists. The specific dry coating amount is preferably 0. Ig/rrr or higher, 6
．． 0g/rr? The following, more preferably 1. Og/d or more and 3.0g/i or less are preferable.

When the amount is less than 0.1 g/rrr, the color development of the dye is poor and is no different from non-coated paper. Also, 6.0g/rrf
If the amount is more than 1, powder will easily fall off, the cost will be high, and it will be difficult to differentiate it from heavy coated paper.

The Bekk smoothness of the surface of the recording material thus obtained needs to be adjusted to less than 20 seconds in terms of ink absorption and dot density.

Color properties of recorded images 9 Regarding image density, the dye is adsorbed by the pigment contained in the ink-receiving layer and remains on the surface layer, eliminating the sinking of dye that occurs with non-coated paper, resulting in a high density. Clear images can be obtained.

Indoor discoloration of images is said to be caused by oxidative decomposition of dyes, but pigments in the coating layer that have a large specific surface area have a high surface activity because the contact area between the dye molecules and air becomes large. Promotes indoor discoloration. Therefore, in the present invention, the BET specific surface area is 200 rr? By using a silicon-containing pigment of /g or less, slightly coated paper that does not cause indoor discoloration can be obtained.

Regarding the cost, it is preferable to use something as cheap as possible, assuming that it will become as popular as PPC paper. The paper of the present invention has a single ink-receiving layer, has a small coating amount, uses a reasonable process for the base paper, and does not use special or expensive materials, so it is inexpensive. It is extremely advantageous.

Bristow tester measurement conditions Disc circumference 1000mm Head box: Slit size 1mm x 15mm
Pressing pressure (*) 0.05MPa (500g/crr
r) (*) J, Tappi is 0.1MPa (1,0
2Kg/crt? ) is the standard, but paper with good absorbency would tear during measurement under this load, so the pressing pressure was reduced. Other measurements were performed according to J. Tappi.

Examples and comparative examples Examples 1 to 4 are given below. Comparative Examples 1 to 3 are shown.

Regarding the recording materials created in each case, 1. Presence or absence of bleeding, 21 image density, 3. Dot density, 4, chromaticity,
5. Ink fixing method, 6. Indoor discoloration, 7° panel test,
8. An evaluation was made regarding powder falling off.

Details of each evaluation method will be described later.

In addition, unless otherwise specified, parts or percentages in the text are important criteria.

Example 1 A filter paper manufactured by Toyo Roshi Co., Ltd. (qualitative filter paper No. 131, Bekk smoothness of 0 seconds) was used as a base paper.

On the above base paper, 3.44 g of silica (Fine Seal X-37, manufactured by Tokuyama Soda), 24.16 g of water, and a waterproofing agent (
2.10 g of a 10% aqueous solution of Polyfix 601 (Showa Kobunshi) was homogenized, and
, :PVA (R-1130 manufactured by Kuraray) 10% aqueous solution 6
．． 66g.

PVA (117H manufactured by Kuraray) 10% aqueous solution 13.34
Add g and stir well with a spatula etc.
, coated by hand using 10 bars, llo'c.

Dry for 5 minutes, dry coating amount 1.5g/n? got the paper. The roughness index of the recording surface of the obtained recording material was 22mf/
B. The smoothness was 2 seconds.

Example 2 A filter paper manufactured by Toyo Roshi Co., Ltd. (quantitative filter paper 5A, Beck smoothness 2 seconds) was used as the base paper.

The coating solution of Example 1 was applied onto the base paper in the same manner as Example 1 to obtain paper with a dry coating weight of 1.5 g/rd.

The roughness index of the recording surface is 28m1! /rrr, Beck smoothness was 10 seconds.

Example 3 A paper with a texture similar to that of filter paper (handmade sheet, Beck smoothness of 4 seconds) was used as the base paper.

The coating solution of Example 1 was applied onto a high-quality base paper in the same manner as in Example 1 to obtain paper with a dry coating weight of 1.5 g/rd.

The roughness index of the recording surface was 16 ml/m2, and the Beck smoothness was 17 seconds.

Example 4 Filter paper manufactured by Toyo Roshi Co., Ltd. (hard filter paper 4A, Beck smoothness 18 seconds) was used as the base paper.

The coating solution of Example 1 was coated on the base paper in the same manner as in Example 1 to obtain paper with a dry coating weight of 1.5 g1rd.

Roughness index of recording surface is 19mf/rri, Bekk smoothness is 1
It was 1 second.

The Steckigt sizing degrees of the base papers of Examples 1 to 4 were all 1 second or less.

Example 5 On the base paper used in Example 1, high purity alumina (AKPG manufactured by Sumitomo Chemical, BET specific surface area 1 I0 manufactured by Tokuyama Soda, specific surface area 18rd/g) was used in a ratio of 1:l. A coating liquid was prepared in the same manner as in Example 1, and coating was performed in the same manner as in Example 1, with a dry coating amount of 2. O glrd paper was obtained. The roughness index of the recording surface of the obtained recording material was 18 m.
I! /rrr, Beck smoothness was 17 seconds.

Example 6 The coating liquid used in Example 5 was applied on the base paper used in Example 2 in the same manner as in Example 1, and the dry coating amount was 2.0 g/l.
I got ri paper. The roughness index of the recording surface of the obtained recording material was 19 m I! / rrr, Beck smoothness was 13 seconds.

Comparative Example 1 The coating solution of Example 1 was applied in the same manner as Example 1 to a commercially available paper with a smoothness of 65 seconds and a Steckigt size of 5 seconds.
The dry coating amount was approximately 1.5 g/rrr. The roughness index of the recording surface of the obtained recording material was 8 ml/rd.

Beck smoothness was 24 seconds.

Comparative Example 2 The coating solution of Example 1 was applied in the same manner as in Example 1 using Canon NP paper (smoothness: 17 seconds, Steckigt size: 35 seconds) as a base paper. The dry coverage was approximately 1.5 g/%. The roughness index of the recording surface of the obtained recording material was 9 m 1
/ rrr, Beck smoothness was 22 seconds.

Comparative example 3 The base paper used in Example 1 was used as a recording material.

The roughness index of the recording surface is 88m1! /rrf, Beck smoothness was 0 seconds.

Comparative Example 4 Tsubo fi 72g/rd. The coating liquid used in Example 1 was applied to paper with an ash content of 15%, a size degree of 2 seconds, and a Beck smoothness of 69 seconds.
.

Perform the same operation below using a bar of 30 to obtain a coating amount of 9.
．． A recording material of 7 g/rrr was prepared. The roughness index of the recording surface of the obtained recording material was 8 m! ! /rr? ,
The Bekk smoothness is 52 seconds.

Each evaluation method is shown below.

■Is there any bleeding?Using a prototype machine with an ink printing density of 360 dpi, print color bars in the order of black, yellow magenta, and cyan by increasing the printing density C) by 1 to 4 to improve the sharpness of the boundary between black and yellow ( The presence or absence of bleeding of black to the yellow side was investigated.

was printed on. R represents overprinting of magenta and yellow.

2. Image density Image density is 0, D,
was measured using Macbeth Densitometer RD-914.

3. Dot density Dot density is determined by applying JIS-7505 to printed microdots using Sakura Microdensity Meter PDM.
-5 (manufactured by Konishiroku Photo Industry ■) to measure black dots.

4. Color property Color property was measured by measuring the saturation of solid printed matter of Bk, Y, M, and C using a high-speed color analyzer CA-35 (Murakami Color Chemical System).

5. Ink fixing property The ink fixing time was measured by measuring the time required for the ink to dry and stop adhering to the finger when touching the recorded image after recording.

6. Indoor discoloration The Bk solid print area formed by the printer used in 1 was mounted on the wall of the office and left for 2 months.

Difference ΔE between the chromaticity of the image after standing and the chromaticity of the image immediately after printing
*Ab was determined and indoor discoloration was evaluated.

7. Panel test In the panel test, recorded images were created using the printer used in 1, and 40 people (24 men, 16 women) were asked the question, ``Which image has the best clarity and contrast?'' Good items were given 5 points and bad items were given 1 point, and the total was shown for a comprehensive evaluation.

8. Powder removal Powder removal is caused by paper powder adhering to the finger when touching the surface of the coating layer, or by peeling or scraping of the coating layer when the surface is scratched with a hardness H pencil. Items that generate powder
, Those that do not are marked as ○.

The recording materials prepared in Examples and Comparative Examples were printed using the recording device ink shown below, and evaluated on the evaluation items shown above. The evaluation results are shown in Tables 1-3.

On-demand inkjet recording head that ejects ink using a piezo vibrator (ejection orifice diameter 60μ)
m, piezo vibrator drive voltage 70v1 frequency 2.6KHz
) Inkjet recording was carried out using the inks shown below and evaluated.

in · C, 1, Direct Yellow 86 diethylene glycol Polyethylene glycol #200 water In and C, 1, acid red 35 diethylene glycol Polyethylene glycol #200 water Blood in and C, 1, Direct Blue 86 diethylene glycol Polyethylene glycol #200 water in .

C, 1, hood black 2 diethylene glycol Polyethylene glycol #200 2nd part 20 copies 10 copies 68 copies 2nd part 20 copies 10 copies 68 copies 2nd part 20 copies 10 copies 68 copies 2nd part 20 copies 10 copies Table 1゜ Presence of bleeding Table 2゜ Image density.

Chromaticity [Effect] As explained above, the recording material of the present invention has (1) high ink absorbency, so it does not become stained even if rubbed with a roller or a finger immediately after printing.

■Not only text and pictures, but also graphs and diagrams that require a large amount of ink can be printed without ink seepage (bleeding) and provide clear images.

(2) Good color properties (a θ image with high image density can be obtained).

■No indoor discoloration of recorded images.

(2) Since a simple manufacturing method is used, inexpensive recording materials can be provided.

It has the following advantages.

Table 3. Dot density, ink fixability, ΔE"ab.

Panel test, powder removal Patent applicant: Canon Co., Ltd.

Claims (3)

[Claims] (1) In a recording material in which an ink-receiving layer is provided on a base paper,
A recording material characterized in that the fibrous substance of the base paper is present near the surface of the ink-receiving layer, and the roughness index of the surface of the ink-receiving layer measured with a Bristow tester is 10 ml/m^2 or more. Material. (2) The recording material according to claim 1, wherein the roughness index is 15 ml/m^2 or more. (3) The recording material according to claim 1, wherein the surface smoothness of the ink receiving layer is 20 seconds or less.