JPS6027588B2 - Inkjet recording paper with water-based ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording paper suitable for inkjet recording using water-based ink, in which the ink adhering to the paper surface is quickly absorbed into the paper layer, and the ink on the paper surface is To provide a recording paper that can suppress the spread of dots.

Inkjet recording is a recording method that has been rapidly developing in recent years.It produces low noise, can record at high speed, and can use commercially available medium-quality paper, so-called plain paper, as the recording paper. is characterized by

Incidentally, inkjet recording paper using water-based ink has the property that ink droplets adhering to the paper surface are quickly absorbed into the paper layer, resulting in an apparently dry state and suppressing the spread of ink dots on the paper surface. In addition to the above-mentioned commercially available medium-quality paper, it is also necessary to have the properties that allow the ink to be Since it is possible to provide a margin for the absorption time of , these two contradictory properties can be practically satisfied.

In other words, in this case, if the ink adhering to the paper surface is absorbed into the paper layer within a few seconds to several tens of seconds, it will not cause much trouble in handling the recorded paper; This is because the spread (blur) of ink dots can also be suppressed to below the required level. however,
When performing multicolor recording by applying two or more different colors of ink to one point on the paper using two or more jet guns at once, or when performing high-speed single-color recording, the paper layer If ink is not absorbed quickly, other ink droplets may overlap with the first ink droplet that reaches the paper surface, causing the ink droplets to become saturated on the paper surface and flow out, or cause the recorded paper to deteriorate. During handling, problems arise such as ink remaining on the paper surface causing contamination.

Therefore, in such cases, paper with particularly good ink absorption properties is required, but in general, paper with good ink absorption properties causes the ink dots to spread widely on the paper surface, which reduces the resolution of recording. It has other drawbacks, and the reality is that no recording paper has been obtained that has the properties required by those skilled in the art. The present invention provides a recording paper that is suitable for inkjet recording using water-based ink, that is, can quickly absorb water-based ink droplets into the paper layer and suppress the spread of ink dots on the paper surface. It is.

In general, in the production of coated paper in which paint is applied to the surface of base paper, sizing is imparted in advance using an appropriate sizing agent, and the base paper is coated to prevent moisture penetration of the paint during the coating process. By using it as paper, troubles such as paper breakage due to a decrease in paper strength due to wet penetration of paint during the coating process, and migration of paint into the inside of paper waste due to excessive paint absorption are avoided, but the present invention So-called non-sizing paper base paper in which a wet paper strength enhancer is internally added almost uniformly, and the internal sizing has a Steckigt size degree of 1 second or less and is not subjected to any substantial sizing treatment such as surface sizing. is used as the paper to be coated.

That is, the recording paper of the present invention is obtained by coating the surface of the above-mentioned so-called non-sizing paper base paper with a paint for the production of ordinary surface-coated paper at a binder amount of 1 to 5 coats/day. By using surface coated paper with a Steckigt size degree of 3 seconds or less, preferably within the pH range of 5 to 10, it does not have the disadvantages of conventional recording paper as described above. It was possible to provide inkjet recording paper using water-based ink. In the recording paper of the present invention, a wet paper strength enhancer is internally added almost uniformly, and a considerable amount of a filler that acts to promote the absorption of paint in the coating process is added internally as desired. It is obtained by coating so-called non-sizing base paper with a coating for the production of ordinary surface-coated paper, as described below. By using a papermaking base paper that has a large paint coating capacity and a high penetration rate of paint into the paper layer, it is possible to create surface-coated paper with a small size suitable for inkjet recording paper using water-based inks. It is something.

In the recording paper of the present invention, in order to prevent a decrease in paper strength during the coating process of the papermaking base paper when obtaining the recording paper, a wet paper strength enhancer is added in the process of adjusting the papermaking raw material of the base paper. However, it is necessary to avoid using sulfuric acid, which not only causes a decrease in ink absorption, but also causes discoloration and coagulation of the ink in some cases.

Fillers for paper base paper that can be used in the present invention include commonly used clay, talc, etc., military calcium carbonate, light calcium carbonate, silica, aluminum hydroxide, titanium oxide, urea-formalin resin-based organic materials, etc. However, base paper containing precipitated (light) calcium carbonate, fine powder seaweed, organic filler, etc. becomes bulky and improves ink absorption. Suitable for manufacturing. The wet paper strength enhancer is preferably one that improves the wet strength without reducing the ink absorption of the paper itself, such as polyamide resins, especially their epichlorohydrin-modified resins and ethoxy-modified resins, glyoxal, and melamine. Resins and modified resins thereof, urea resins and modified resins thereof, polyethyleneimine and derivatives thereof, dialdehyde starch or dialdehyde gum, etc. can be used.

Furthermore, surface coating materials include oxidized starch, modified starch, PVA, sodium alginate, CM○, other water-dropping cellulose derivatives, casein, soybean protein, synthetic resin emulsion, etc., which are used in ordinary coated paper manufacturing. In addition to the binder component, paints whose main ingredients are kaolin, carmine or light calcium carbonate, aluminum hydroxide, titanium oxide, titanium white, and other pigments can be used, and these paints can be used. is applied to base paper using a size press, roll coater, or other type of coater.

In this case, if a large amount of synthetic resin, which is particularly hydrophobic and has strong film-forming power, is blended as a binder in the paint component, it will be a factor that inhibits ink absorption, so this blend should be kept low.

Also, if the amount of paint applied is too small, the effect of suppressing the spread of ink dots will be poor, so it is recommended that the amount of binder is applied at a rate of 1 to 5 days/day, preferably 2 to 4 days/day. . In addition, starch, PVA, etc. are added as pre-coating treatments that are carried out in the production of ordinary surface-coated paper.
If coating with a surface paint is performed after surface sizing with other surface sizing agents, ink absorption will decrease even if the Steckigt sizing degree of the obtained surface coated paper is 3 seconds or less. In the recording paper of the present invention, the coating treatment on the base paper must be performed directly on the so-called non-sizing base paper.

In the recording paper of the present invention, if the Steckigt size degree of the paper is not suppressed to 3 seconds or less, during high-speed inkjet recording or multicolor inkjet recording using water-based ink, the surface of the recording paper may be damaged by undried ink. Phenomena such as spillage due to dirt or overlapping ink may occur.
Since a clear recorded image cannot be obtained, the recording paper is unsuitable for such uses.

Furthermore, the coating process for papermaking base paper in the present invention does not particularly need to be carried out after drying the papermaking basepaper; undried papermaking base paper can also be coated in the same manner as dried papermaking basepaper. can.

The recording paper of the present invention has the above-mentioned structure, and uses so-called non-sizing paper with a Steckigt size of 1 second or less and a Steckigt size of substantially 0 as the base paper to be coated. In surface coating treatment with paint,
The paint does not form a film on the paper surface, resulting in a surface-coated paper that has good ink absorption, has a low size, and has the effect of suppressing the spread of ink dots on the paper surface. . The inkjet recording paper using the water-based ink of the present invention can be obtained at low cost because it can substantially omit the use of a sizing agent and the surface sizing process, etc., which are required in the production of conventional paper. Moreover, it can be manufactured with a small number of steps.

In addition, the recording paper of the present invention does not require any special processing agent or processing process when obtaining the paper, and can be obtained using the same paint and coating equipment used in the production of conventional surface-coated paper.
It also has the advantage that it can be manufactured using

In the present invention, the Steckigt size degree is a value measured based on a basis weight of 60 mm/force.

The specific structure of the recording paper of the present invention and the characteristics of the paper will be explained below using Examples.

Example 1 LBKP with a freeness (C.S.F.) of 400 was used as the raw material pulp, and 1 wt. Chimen 557 (Dicks Hercules Co., Ltd., registered trademark) as a wet paper strength enhancer was added internally at 0.2% by weight based on the pulp solid components, and a paper with a basis weight of 60 tano was added using a small Fourdrinier-type last machine. The paper was then sanded using a conventional method to obtain paper base paper.

Next, a 5% solution of oxidized starch and PVA powder mixed at a ratio of 1:1 was used as a paint and applied to the paper base paper using a size press method, and the amount of binder was 2.8 y/ml.
Surface-coated paper, which is an example of the present invention, was obtained.

The obtained surface-coated paper was used as a recording paper and was injected into three inkjet guns with a nozzle diameter of 40 mm.
The three-color ink of Yellow and Magenta was ejected almost simultaneously, and the print grain size was 70mm. Surface-coated paper'
Table 1 shows a comparison with the case where each of B} is used as a recording paper.

As can be seen from the results in Table 1, when the surface-coated paper obtained in this example is used as recording paper, the ink runs out due to overlapping compared to commercially available high-quality paper. There is no blurring, and the blur can be suppressed to a level almost similar to that of commercially available high-quality paper.

Example 2 To the same base paper used in Example 1, 10 parts of kaolin as a filler, 0.3 parts of sodium hexametaphosphate as a dispersant, 24 parts of oxidized starch as a binder, and P
8 parts VA, 0.0 parts calcium stearate as a shaping agent.
A paint consisting of a 25% solid component dispersion of a blended composition consisting of 6 parts was applied by a size press method to obtain a surface-coated paper with a solid component coating amount of 13 parts/day.

Using the obtained surface coated paper as a recording paper, ink jet recording was carried out under the same conditions as in Example 1. A comparison is shown in Table 2.

From the results shown in Table 2, the blurring of inkjet recordings on commercially available surface-coated paper can be suppressed to a slightly smaller level than the blurring on the recording paper obtained in this example, but the ink flow is large and the recordings are unclear. It is unusable.

On the other hand, in this example, the ink did not flow out, the diameter of the dots was kept small, and clear recording was obtained. In the case of commercially available paper, the ink did not run out, but the ink was blurry and clear records could not be obtained.

Example 3 Freeness (C.S.F.
) 400 'LBKP of 8% by weight, freeness (C
．． S. F. ) 450 NBKP at a ratio of 2% by weight, 25% by weight of bonito calcium carbonate as a filler based on the pulp solid components, and Kymen 557 ( as a retention improver and wet paper strength enhancer). Dicks Hercules Co., Ltd., registered trademark) is also used for pulp solid components.
．． 2% by weight was added internally, and paper was made with the same paper machine as used in Example 1 with a basis weight of 60 m/m to obtain paper base paper.

To this paper base paper, light calcium carbonate 10 base, acidic acid Q
Solid component concentration of a compounded composition consisting of 1 part of starch, 5 parts of SBR latex, a small amount of sodium hexametaphosphate as a dispersant, and a small amount of calcium stearate as a mold release agent.
% solution was applied, and the amount of solid component applied was 12 days/day.
Thus, a surface coated paper with a Steckigt size of 0 seconds was obtained.

The resulting surface-coated paper has a viscosity layer. p. The diameter of the dots as a result of printing with an ink jet gun using the ink water-based ink was circular, similar to that of commercially available surface-coated paper, and the drying time of the ink droplets was within 1 min.

However, a 4% solution of Acid-Q starch was size-press coated on the base paper, and then a paint made from the same solution as above was applied, the solid component coating amount was 9 mm/final, and the Steckigt size was 0 seconds. The drying time of the ink droplets printed on the surface-coated paper using the same ink jet gun as above required more than 3 coats. Example 4 The same base paper as used in Example 3 was mixed with 8 parts of kaolin as a pigment, 2 parts of vertical calcium carbonate, 0.2 parts of sodium hexametaphosphate, and 0.2 parts of sodium polyacrylate as a dispersant. parts, 12 parts of oxidized starch as a binder, PV
A12 parts, calcium stearate 0.6 as mold release agent
A paint consisting of a 30% solid component concentration solution mixed in a ratio of 1.0 parts was coated on one side using an air knife coater to obtain surface coated paper with a solid content coating amount of 11 #/〆 on one side and a Steckigt size degree of 0 seconds. Ta.

The resulting surface-coated paper was recorded using an ink jet gun under the same conditions as in Example 3, and the dot diameter and ink drying time were approximately the same as those of the surface-coated paper obtained in Example 3. A good print record was obtained.

Example 5 C. S. F. 400' of LBKP8 and C.
S. F. 450' of NBKP2 (wt%) and 15 wt% of Yuluk as a filler based on the solid components of the pulp, and Kymen 557 (Dix-Hercules Co., Ltd., registered trademark) as a wet paper strength enhancer. Similarly, 0.1% by weight was added internally to the pulp solid components, and this was then sanded to a basis weight of 60 mm/gap using a small Fourdrinier-type last machine in a conventional manner to obtain paper base paper.

Next, each coating material 'd), 'e', and
'f} is applied at a ratio of solid component application amount 12 times/final,
Two types of surface coated paper ■ and 'E' which are examples of the present invention
And the surface coated paper value was obtained for comparison. Table 4 shows the results of inkjet recording using water-based ink in the same manner as described in Example 1 using each of the surface-coated papers obtained as recording paper. From the results in Table 3 and Table 4, it can be seen that as the Steckigt size of the surface-coated paper increases, the drying time of the ink droplet on the surface-coated paper becomes longer, and the Steckigt size of the surface-coated paper increases by 4 seconds. It is clear that the paper does not have sufficient performance as a recording paper.

Claims (1)

[Claims] 1. On the surface of a substantially unsized base paper to which a wet paper strength enhancer has been internally added almost uniformly, a paint for normal surface coating is applied at a binder content of 1 to 5 g/m^2. 1. An inkjet recording paper using a water-based ink, which is characterized by being infiltrated into the inside of paper base paper and having a Steckigt sizing degree of 3 seconds or less.