JPH08267908A - Ink jet recording paper - Google Patents

Abstract

PURPOSE: To provide ink jet recording paper imarting high printing density, reduced in bronzing and excellent in printing characteristics generating no feathering. CONSTITUTION: In ink jet recording paper of which the surface printed by an ink jet printer is coated with a surface size agent of which the pH is 8.5 or more as a dilute aq. soln. with a concn. of 1.0wt.%, the 30sec Cobb size degree of the recording paper by a 5.0% aq. isopropyl alcohol soln. after the 24h conditioning of humidity under a condition of 20 deg.C and 65% relative humidity is 16.0g/m<2> or less.

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 paper having improved size and ink jet suitability. More specifically, the present invention relates to an ink jet recording paper which has a high print density when printed by an ink jet method, and does not suffer from feathering or discoloration of the print portion over time.

[0002]

2. Description of the Related Art The ink jet recording system is one in which a small amount of ink is ejected by various mechanisms and adhered onto a recording paper to form dots for recording, which is different from the dot impact type recording system. No noise,
Further, there are advantages such that full-color printing is easy and high-speed printing is possible. In general, the properties required for an inkjet recording paper used in an inkjet recording system include (1) a fast ink drying speed, (2) a high print density, and (3) little bleeding.

Further, there is a phenomenon that the ink is discolored during the process of drying the ink on the surface and inside of the ink jet recording paper. In particular, the phenomenon that the color tone changes from black to glossy brown during the drying process of black ink is called “bronzing”. The degree of this “bronzing” is a newly required quality characteristic in addition to the quality characteristic described above.

On the other hand, in the market, from a coated paper type ink jet recording paper in which a pigment having a large specific surface area is coated with a binder on the surface of the base paper as an ink receiving layer,
There is an increasing demand in the market for plain paper-like, so-called non-coated ink jet recording paper.

In order to solve these problems for non-coated type ink jet recording paper, for example, in JP-A-62-156985 and JP-A-4-331182, an alkali metal salt or A method of applying a phosphate, JP-A-6-220794 discloses a synthetic aluminum silicate or kaolin mineral which adsorbs ammonia or ammonium ions derived from a nitrogen compound serving as a dissolution aid of a dye in ink. A method of internal addition is disclosed.

However, when these methods are used, it is very important to balance the print density, the degree of discoloration, and the bleeding that occurs along the fibers on the surface of the ink jet recording paper (hereinafter referred to as feathering). It's difficult. In addition, the amount of filler used in the base paper can be limited.

[0007]

The object of the present invention is to:
An object of the present invention is to provide an ink jet recording paper excellent in characteristics required for image quality printed by an ink jet method such as feathering, print density, and bronzing.

[0008]

DISCLOSURE OF THE INVENTION As a result of intensive investigations by the present inventors to solve the above-mentioned drawbacks, the inventors have invented the ink jet recording paper of the present invention.

That is, the ink jet recording paper of the present invention is obtained by applying a surface sizing agent having a concentration of 1.0% by weight of a diluted aqueous solution having a pH of 8.5 or more on the surface to be printed by an ink jet printer, and at 20 ° C. , Relative humidity 65%
Under the conditions of 24 hours, the Cobb size degree of 30 seconds by the 5.0% isopropyl alcohol aqueous solution after the humidity control for 24 hours is 1
It is characterized by being 6.0 g / m ² or less.

The ink jet recording paper of the present invention will be described in detail below.

The present inventors firstly examined the relationship between the size characteristics and the printing characteristics of the ink jet recording paper of the present invention.

[0012] As a representative index that generally indicates the sizing property of paper, there are the Stecht sizing degree and the Cobb sizing degree. However, no good correlation was found between these indexes and the printing characteristics of the inkjet recording paper. It is considered that this is because the ink of the inkjet printer has a lower surface tension than water in order to improve the penetration into the paper layer. Therefore, as a result of a comparative study of the Cobb sizing degree of aqueous solutions having different surface tensions and the printing characteristics of ink jet recording paper, the Cobb sizing degree and the printing characteristics measured by using a 5% isopropyl alcohol aqueous solution are excellent, especially between feathering. There was a strong correlation. And 5% of inkjet recording paper
It was found that the feathering when printing with an inkjet printer was good when the Cobb size degree of 30 seconds in an isopropyl alcohol aqueous solution was 16 g / m ² or less,
The inventors have invented the inkjet recording paper of the present invention.

In order to suppress feathering, it is sufficient that the 30-second Cobb size degree in a 5% isopropyl alcohol aqueous solution is 16 g / m ² or less as described above. However, if the size of the ink jet recording paper is increased too much, the ink absorbency deteriorates, and the bronzing of the printing portion progresses,
Ink that does not completely dry on the transfer paper may stain the printing surface during continuous printing with an inkjet printer. Therefore, considering the printing characteristics of the inkjet recording paper and the operability during printing, it is desirable that the 30 second Cobb size degree in a 5% isopropyl alcohol aqueous solution is 13 to 15 g / m ² .

The appropriate sizing property as described above for the highly penetrative ink ejected from such an ink jet printer depends on the amount of the internally added sizing agent used when manufacturing the recording paper. This can be achieved by a control method or a method of applying a surface sizing agent on the printed surface of the recording paper, alone or in combination.

The inventors of the present invention have studied the means for controlling the sizing property, and in the course of this, the discoloration in the drying process of the printing part depending on the kind of the surface sizing agent, especially from the black tint in the drying process of the black ink. It was found that the phenomenon of discoloration to glossy brown, that is, the degree of "bronzing" was greatly different. Then, as a result of diligent study on the pH of the dilute aqueous solution of the surface sizing agent and the degree of "bronzing", the surface sizing agent having a dilute aqueous solution of pH 8.5 or more at a concentration of 1.0% by weight was used. By applying it to the ink, it is possible to provide an inkjet recording paper with a lesser degree of "bronzing".

Regarding the mechanism of occurrence of "bronzing", as described in JP-A-6-220794,
It is considered that a part of the dye in the ink is agglomerated in an oriented form and is not absorbed in the paper layer and is deposited on the paper surface, so that the black printed portion looks brown in particular.

Therefore, in order to suppress the bronzing, it is necessary to increase the absorbability of the ink into the paper layer. As a method for improving the ink absorbability, as described in JP-A-62-156985, an alkali metal hydroxide, an alcar metal carbonate, or an alkali metal hydrogen carbonate is applied to the surface of the base paper. It is known that this improves ink absorbency, but in reality, it is difficult to balance with feathering.

However, by applying a surface sizing agent in which the pH of the diluted aqueous solution at a concentration of 1.0% by weight is 8.5 or more to the printing surface of the recording paper, the fibers on the printing surface of the recording paper are made into ink. On the other hand, it shows the size property to the paper layer and at the same time, in the paper layer, as an "alkaline substance", it is considered to help the absorption of the ink into the paper layer.

As the surface sizing agent to be coated on the surface of the above-mentioned base paper, the main components are styrene / acrylic acid type copolymers, styrene / methacrylic acid type copolymers, acrylonitrile / vinyl formal / acrylic acid ester copolymers. Examples thereof include coalesced products, styrene / maleic acid type copolymers, olefin / maleic acid type copolymers, and AKD type surface sizing agents.

The coating amount of the above surface sizing agent depends on the sizing property of the base paper, but preferably about 0.05 to 1.5 g / m ² as a solid amount on the base paper surface. It is desirable to apply it.

A conventional size press, a gate roll size press, a film transfer type size press, a rod coater, a bill blade, a short dwell coater, or the like can be used as an apparatus for applying the surface sizing agent by a size press. it can. Among these coating devices, it is desirable to use a system in which the surface sizing agent is applied to the inside of the paper layer.

Simultaneously with the coating of the surface sizing agent, a binder such as starch and polyvinyl alcohol, a dimensional stabilizer such as ethylene-urea resin, an inorganic conductive agent such as sodium chloride and potassium chloride, an organic conductive agent, a surfactant, It is of course possible to apply a pigment or dye.

The wood pulp used for making the base paper of the present invention includes NBKP, LBKP, NBS.
In addition to P, LBSP, GP, TMP, etc., waste paper pulp can be mentioned. In use, several kinds of them are mixed and used at a ratio according to the purpose.

The raw materials for waste paper pulp referred to in the present invention include white, ruled white, cream white, card, and white, as shown in the waste paper standard quality standard table of the Waste Paper Recycling Promotion Center.
Special white, medium white, imitation, fair white, Kent, white art, special cut,
Examples include separate papers, newspapers, and magazines. More specific examples include non-coated computer paper, which is information-related paper,
Printer paper such as thermal paper and pressure-sensitive paper, and OA waste paper such as PPC paper, art paper, coated paper, lightly coated paper, coated paper such as matte paper, or high-quality paper, high-quality paper, notebook, notepaper, wrapping paper , Fancy paper, medium-quality paper, newsprint, waste paper, super hanging paper, imitation paper, pure white roll paper,
Paper such as uncoated paper such as milk carton and waste paper such as paperboard, such as chemical pulp paper and high-yield pulp-containing paper are used, but are not particularly limited to printing, copying, printing and non-printing. Absent.

As the filler used when making the base paper of the present invention, various fillers can be used in addition to the calcium carbonate used in the neutral paper, and several kinds of these fillers and calcium carbonate can be used in combination. It is also possible to use.

As the internally added sizing agent used for making the base paper of the present invention, rosin-based sizing agent, alkenyl succinic anhydride, alkyl ketene dimer, petroleum resin-based sizing agent and the like can be used.

In addition to the above, various anionic, nonionic, cationic or amphoteric paper strength improvers which have been conventionally used, etc. may be added to the paper stock within a range not impairing the desired effects of the present invention. An internal additive for papermaking is appropriately selected and used as necessary. For example, one of starch, polyacrylamide, polyethyleneimine, polyamine, polyamide / polyamine, urea formalin resin, melamine formalin resin, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide, and polyamide resin.
They may be used either individually or in combination of two or more.

It is also possible to appropriately add an internal additive for papermaking such as a dye, a pH adjusting agent, a defoaming agent, a pitch control agent and a slime control agent according to the purpose.

In the papermaking method of the present invention, as the papermaking machine, a papermaking machine known in the papermaking industry such as a Fourdrinier paper machine, a twin wire papermaking machine, a combination papermaking machine, a round net papermaking machine or a Yankee papermaking machine can be appropriately used.

The ink jet recording paper of the present invention can be used not only as an ink jet recording paper but also as an electrophotographic transfer paper, a thermal transfer image receiving paper, and a printing paper.

[0031]

In the ink jet recording paper of the present invention, the surface to be printed is coated with a surface sizing agent having a concentration of 1.0% by weight of a dilute aqueous solution having a pH of 8.5 or more, and at 20 ° C. and a relative humidity of 65%. 5.0 after 24 hours humidity control
% Isopropyl alcohol aqueous solution having a 30-second Cobb size of 16.0 g / m ² or less.
By satisfying these conditions, a surface sizing agent that exhibits appropriate sizing property for ink having high permeability on the fiber surface and at the same time exhibits alkalinity under specific conditions helps absorption of ink into the paper layer. be able to. As a result, it is possible to provide an inkjet recording paper having high printing density, less bronzing, and excellent printing characteristics without feathering.

[0032]

EXAMPLES The present invention will be described in detail below with reference to examples. The present invention is not limited to this. All parts and% in the following are by weight.

First, a base paper was prepared according to the following formulation. <Preparation of base paper> Base paper formulation; LBKP (freeness: 450 ml, cf) 100 parts Calcium carbonate (Okutama Kogyo; TP-121) 7 parts AKD emulsion sizing agent (Arakawa Chemical Co., Ltd .; Saibein K) -903) 0.10 part Aluminum sulfate 0.5 part Amphoteric starch (Oji National Co .; Cato3210) 1 part Yield improver (Himo Co .; NR-11LS) 0.02 part

A 0.3% slurry having the above composition was used to make paper width 1,3.
00 mm, papermaking speed 150 m / min. With a Fourdrinier paper machine, the basis weight is 62.7 g / m ² , the density is 0.75 g / cm ³ , and the water content is 5.
A 0% base paper was made into a paper, which was used as a base paper for a size press.

Next, ink jet recording papers of Examples and Comparative Examples were prepared according to the following method.

Example 1 The above-prepared base paper was size-pressed with the following composition to obtain an inkjet recording paper having a solid content of 1.5 g / m ^{2 and used as} the inkjet recording paper of Example 1. The pH of a 1.0% by weight dilute aqueous solution of KN-500 was 10.3. <Size press liquid formulation> Oxidized starch (manufactured by Japan Food Processing Co .; MS-3800) 5 parts Surface sizing agent (manufactured by Harima Chemicals; KN-500) consisting of styrene / acrylic acid type copolymer 0.15 parts water 94 .85 parts

Example 2 The surface sizing agent in the size press liquid in Example 1 was 0.20.
An inkjet recording paper of Example 2 was produced in the same manner except that the parts were used.

Example 3 The same as in Example 1 except that the surface sizing agent in the size press liquid was 0.15 part of the surface sizing agent (manufactured by Japan PMC; SS315) made of a styrene / methacrylic acid copolymer. Inkjet recording paper of Example 3 was produced. In addition, p of a 1.0% by weight diluted aqueous solution of SS315 was added.
H was 9.5.

Example 4 Same as Example 1 except that the surface sizing agent in the size press liquid was 0.20 part of the surface sizing agent (manufactured by Japan PMC; SS315) composed of a styrene / methacrylic acid copolymer. Then, an inkjet recording paper of Example 4 was produced.

Example 5 The same as Example 1 except that the surface sizing agent in the size press liquid was 0.15 part of the surface sizing agent (manufactured by Arakawa Chemical Co., Ltd .; Polymaron 1308S) consisting of a styrene / acrylic acid copolymer. Then, an inkjet recording paper of Example 5 was produced. The pH of a 1.0% by weight diluted solution of polymalon 1308S was 8.8.

Example 6 The same as Example 1 except that the surface sizing agent in the size press liquid was 0.20 part of the surface sizing agent (Polymaron 1308S manufactured by Arakawa Chemical Co., Ltd.) made of a styrene / acrylic acid copolymer. Inkjet recording paper of Example 6 was produced.

Example 7 The same as in Example 1 except that the surface sizing agent in the size press liquid was 0.15 part of the surface sizing agent (Polymaron 1343S manufactured by Arakawa Chemical Co., Ltd.) made of a styrene / acrylic acid copolymer. Inkjet recording paper of Example 7 was produced. The pH of a 1.0% by weight diluted solution of polymalon 1343S was 8.7.

Example 8 The same as Example 1 except that the surface sizing agent in the size press liquid was 0.20 part of the surface sizing agent (manufactured by Arakawa Chemical Co., Ltd .; Polymaron 1343S) composed of a styrene / acrylic acid copolymer. Inkjet recording paper of Example 8 was produced.

Example 9 The same as Example 1 except that the surface sizing agent in the size press liquid was 0.15 part of the surface sizing agent (Polymaron 1346, manufactured by Arakawa Chemical Co., Ltd.) made of a styrene / acrylic acid copolymer. Inkjet recording paper of Example 9 was produced. The pH of a 1.0 wt% dilute aqueous solution of polymalon 1346 was 8.5.

Example 10 The same as Example 1 except that the surface sizing agent in the size press solution was 0.20 part of the surface sizing agent (manufactured by Arakawa Chemical Co., Ltd .; Polymaron 1346) composed of a styrene / acrylic acid copolymer. Inkjet recording paper of Example 10 was produced.

Comparative Example 1 The surface sizing agent in the size press liquid in Example 1 was 0.05.
An inkjet recording paper of Comparative Example 1 was produced in the same manner except that the parts were used.

Comparative Example 2 The same as in Example 1 except that the surface sizing agent in the size press liquid was 0.05 part of the surface sizing agent (manufactured by Arakawa Chemical Co., Ltd .; Polymarlon 1308S) made of a styrene / acrylic acid copolymer. Then, an inkjet recording paper of Comparative Example 2 was produced.

Comparative Example 3 The same as Example 1 except that the surface sizing agent in the size press liquid was 0.15 part of the surface sizing agent (Hamacoat S920, manufactured by Misawa Ceramics Co., Ltd.) made of a styrene / acrylic acid copolymer. Then, an inkjet recording paper of Comparative Example 3 was produced. 1.0% by weight of Hamacoat S920
The pH of the diluted aqueous solution of was 7.3.

Comparative Example 4 The surface sizing agent in the size press liquid used in Example 1 was replaced by a surface sizing agent (BAS) composed of a styrene / acrylic acid copolymer.
An inkjet recording paper of Comparative Example 3 was produced in the same manner except that 0.15 part of F. Co., Ltd .; Bathoplast 250D) was used. The pH of the 1.0 wt% diluted aqueous solution of Bathoplast 250D was 3.5.

The pH of the surface sizing agent aqueous solution used when the above-mentioned ink jet recording paper is prepared is obtained by diluting the surface sizing agent stock solution to 1.0% by weight with distilled water as described in JIS P8133. , Glass electrode pH meter (manufactured by Yokogawa Electric; pH meter PH-81-53J
Type). The measured value was rounded off to the first decimal place and reported.

The Cobb sizing degree of the ink jet recording paper produced as described above is 20 ° C. and relative humidity is 65%.
After humidity control for 24 hours, measurement was performed according to JIS P8140. The contact time between the measurement solvent and the measurement sample was 30 seconds, and the measurement solvent was a 5% isopropyl alcohol aqueous solution. In the present invention, the water absorption measured with respect to the 5% isopropyl alcohol aqueous solution measured under the above conditions is defined as “30 seconds Cobb size”.

With respect to the ink jet suitability of the above ink jet recording paper, the print quality of characters printed using an ink jet printer BJ-10V manufactured by Canon Inc. was evaluated by the following method.

1. Printing Density: Solid printing is performed by the above inkjet printer, and after the solid printing portion is sufficiently dried, the optical density (OD) of the solid printing portion is measured using a Macbeth reflection densitometer (Macbeth RD-918). did. As the optical density that can withstand normal use,
It is 1.30 or more.

2. Bronzing: Solid printing is performed by the above inkjet printer, and after the solid printing portion is sufficiently dried, a colorimeter (CR-200 manufactured by Minolta Co.)
It measured using. The measurement results are displayed in the L ^* a ^* b ^* color system according to JIS Z8729. The degree of bronzing is expressed by the chromaticness index a ^* of the solid print portion. Normally, when you look at the print part, at first glance "black"
Rather, it is "brown" when the chromaticness index a ^* is 3.0 or more.

3. Feathering: The outer edge of the characters printed by the above inkjet printer was evaluated by visual evaluation in 6 levels. 6 without any feathering
The value 1 was assigned when the ink was bleeding and the characters could not be identified. The print quality that can withstand normal use is 4 or more.

[0056]

[Table 1]

Evaluation results: In Table 1 above, the sizing properties of the ink jet recording sheets of Examples 1 to 8 and Comparative Examples 1 to 4 were compared with the printing characteristics of the ink jet printer.

By comparing Examples 1 to 10 with Comparative Examples 3 and 4, p of a 1.0% by weight dilute aqueous solution of the surface sizing agent was compared.
It can be seen that when H is 8.5 or more, the degree of bronzing is small. At the same time, it can be seen that the higher the pH of the diluted aqueous solution, the less the degree of bronzing.

Example 1, Example 5 and Comparative Example 1, Comparative Example 2
Even if the surface sizing agent having a pH of 8.5% or more of the 1.0 wt% diluted aqueous solution is applied to the surface,
% Cobb size of isopropyl alcohol aqueous solution
If it is 16 g / m ² or more, the density of the solid print portion is lowered and the feathering is deteriorated.

[0060]

From the above results, in the ink jet recording paper of the present invention, a surface sizing agent showing the alkalinity of the diluted aqueous solution having a pH of 8.5 or more is applied to the surface of the recording paper, and 5.0% under the specified condition. By using an isopropyl alcohol aqueous solution and having a Cobb size degree of 30 seconds in a specific range,
It has excellent print characteristics such as print density, bronzing, and feathering.

Claims (1)

[Claims] 1. A surface sizing agent having a pH of 8.5 or more in a 1% by weight diluted aqueous solution is applied to a printed surface, and 20
An inkjet recording paper having a Cobb size degree of 30 seconds in a 5.0% isopropyl alcohol aqueous solution of 16.0 g / m ² or less after conditioning for 24 hours at a temperature of 65 ° C. and a relative humidity of 65%.