JPS6120797A - Recording paper having excellent ink acceptability - Google Patents

Abstract

PURPOSE:To obtain a recording paper having excellent ink absorbability, excellent lustrousness, good writability by writing tools, and good capability of giving good color density in color recording by providing a paint coat layer containing a specific light calcium carbonate and a specific polymer binder on a base paper. CONSTITUTION:Light calcium carbonate to be used as a pigment component for a paint coat layer, which is obtained by subjecting a mixture of calcium carbonate having a specific surface area of 70m<2>/g or more (by BET method) and water in equal amounts to a centrifugal separation of relative centrifugal forces of 1,600G at 20 deg.C for 30min in such a way as to form calcium carbonate having a sedimentation volume of 1.0ml/g or more, is mixed with a high polymer binder (e.g., latex binders) in a proportion of 60-95:40-5 in solid ratio. The mixture is further mixed with a pigment component (e.g., kaolin, clay, etc.), a water- resistant agent, etc., as needed, coated on a base paper, and dried. The amount of the paint to be coated is properly 5-50g/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a recording paper for a non-impact printer using an inkjet printer or the like.

The superiority or inferiority of not only conventional inkjet recording methods but also non-impact recording methods in general is determined by many factors such as recording speed, resolution, two-color density, maintenance requestability, and cost per print.

Of course, the quality of each of the above factors depends on the performance of the printer itself, such as the recording method and recording mechanism, but for example, in the case of an inkjet recording method, the recording performance greatly depends on the ink and recording paper. Depends on it.

For example, regarding recording speed, the problem is the ink absorption speed of the recording paper, but no matter how fast the printer's recording speed can be, the absorption of ink on the recording paper will not keep up with the recording speed. In this case, the ink discharged from the printer onto the recording paper remains in an undried state, resulting in contamination of the discharge roll, the worker's hands, and other places that come into contact with the recording surface. Even when mechanical contact often occurs on the recording surface, when performing multicolor recording, inks of different colors discharged adjacent to each other on the recording paper may flow into each other, causing bleeding and color mixing. There is.

Because of the above-mentioned drawbacks, as the recording speed of a printer increases, there is a demand for recording paper with higher ink absorbency.

Next, a similar situation occurs regarding resolution.

If a printer's jet nozzle is made finer, the diameter of the ink droplet ejected from the nozzle will become smaller, and the diameter of the ink droplet recorded on the recording paper will also become smaller, which should improve the resolution. Due to performance, the ink used for wide dot inkjet recording on recording paper is generally water-based, so dot ink is difficult to absorb into the paper surface on so-called large-sized high-quality paper or coated paper.
Therefore, the spread of the dots is small and the ink absorbability is poor, so that the recording speed cannot be improved.

On the other hand, if you use low-size paper or no-size paper to achieve high-speed recording, dot ink will be absorbed quickly, but on the other hand, the dot ink will spread more widely within the paper surface, resulting in a lack of resolution. become.

The density of the recorded image is also related to the spread of the dots; the larger the spread of the dots on the paper, the lower the density.
On the other hand, the reflection density at the culm where one dot of ink remains in a narrow area on the paper surface becomes high.

As mentioned above, the recording performance of inkjet printing is largely controlled by the characteristics of the paper, and it is required to simultaneously satisfy contradictory conditions due to the characteristics of the paper.

Various efforts have been made to harmoniously satisfy the above-mentioned demands, such as uncoated paper that does not contain any sizing agent and is made with low density, and coated paper such as NRIKA etc. A wide variety of inkjet recording papers have been developed, such as papers coated with paints made of pigments and water-soluble polymeric binders.

In general, uncoated (plain type) and low-size recording paper has good ink absorption, but
Since the ink diffuses within the paper layer, a problem arises in the clarity of the image, and in particular, the resolution and color density cannot be said to be sufficient when recording multiple colors. On the other hand, coated type recording paper has excellent recording density and clarity because the dye in the ink is adsorbed and retained in the coating layer, but its ink absorption and drying properties are lower than that of the plain type recording paper. It doesn't come close to that.

In recent years, as the field of use for inkjet recording method 1 has rapidly expanded, customers' quality requirements for inkjet recording media have also become broader, and glossy inkjet recording media such as printed matter and photographs are also required. It has come to be. Of course, unless a matting treatment is purposefully applied, from an aesthetic point of view, if blank paper, coated paper, or art paper that requires glossy printing is used as inkjet recording paper, the only requirement for glossiness will be avoided. Although this problem was solved immediately, as mentioned above, the problem with coated paper is the low absorbency and low drying properties of water-based inkjet ink, which causes the ink to run out on the paper, making it unsuitable for practical use. Become. In addition, in conventional coat-type inkjet recording paper, which is provided with a coating layer consisting of white carbon and a water-soluble polyvinyl alcohol binder as pigments, when gloss treatment is required, 1 strong super calender finish is applied. However, due to the amorphous nature of the white carbon, it was completely difficult to impart a TAPPI gloss of 45 to 75, which is equivalent to that of gloss coated paper. Moreover, coated paper using white carbon has the disadvantage that pencils, ballpoint pens, etc. tend to slip on it, and writing properties are poor.

Problems to be Solved by the Invention The present invention has a gloss comparable to that of the above-mentioned cross-coated paper, has good recording density and sharpness when inkjet printing is performed, and has excellent ink absorbency, and is similar to a pencil. It is an object of the present invention to provide a recording paper with improved writing properties with ballpoint pens and the like.

Means for Solving the Problems As a result of extensive research in order to solve the above-mentioned problems, the inventor has found that the specific area measured by the BET method on the base paper is 70 m.
251 samples at 1600G at 27F or higher and 20℃
The sedimentation volume after centrifugation for 30 minutes at a relative centrifugal force of 1
．． 0 yards/L! ' By obtaining a paper provided with a coating layer containing the light calcium carbonate pigment and a polymer binder as described above, the above-mentioned problems can be solved, especially by supercalendering the paper. This led to the completion of the present invention.

According to the present invention, an inkjet that satisfies the above-mentioned problems, that is, the demands for excellent ink absorption and strong gloss, has good color density and tone clarity of color recording, and has improved writing performance with a pencil, etc. It is possible to provide recording paper suitable for etc.

Moreover, the glossy paper according to the present invention continues to maintain the print gloss of the recorded portion, and can meet the demand for a printed material with a highly aesthetic appearance.

Of course, since the recording paper according to the present invention has excellent ink absorbency, recording density, and gloss, it is not only good for paper scales used for general printing, but also for paper surface smoothness and It is also suitable as a receiving paper for wax or dye thermal transfers with sensitive ink receptivity.

The present invention will be explained in detail below.

Calcium carbonate used as a pigment component in the coating composition of the present invention has a specific surface area of 7 according to the BET method.
0 m27? With the above, a mixture of 252 calcium carbonate and the same amount of water was centrifuged for 30 minutes at 20°C and a relative centrifugal force of 1600G using a special centrifuge tube in a centrifuge described below. Sedimentation volume loading after carrying out 1. Oi
/'? The above is a light calcium carbonate pigment.

Generally, light calcium carbonate is produced by blowing carbon dioxide into milk of lime and reacting it, but the light calcium carbonate pigment used in the present invention is produced by devising the reaction conditions during production, such as using metal sulfuric acid. By using salt as an additive and further adding alkali silicate, potassium, etc. to significantly increase the reaction rate, as a result, ultrafine rectangular parallelepiped particles with a particle size of around 0.02 μm were connected in a chain. Commercially available products include Toyo Fine TF-X manufactured by Toyo Denka Kogyo Co., Ltd.

The present inventor previously disclosed in Japanese Patent Application No. 58-59968,
The specific surface area by the BET method is 2 on a nearly sizeless base paper.
00 m2/li1 or more, and the uniformity number n of the rosin-ramura distribution is 1.10 or more, that is, coated paper coated with a paint consisting of fine silica with a narrow particle size distribution range and a water-soluble polymer binder is used as inkjet recording paper. proposed to do so. In the above-mentioned Japanese Patent Application No. 58-59968, an inkjet printed material with high color density and clarity is obtained by coating silica with a very large specific surface area, and a material with a narrow particle size distribution range is selected. By doing so, you can obtain something with significantly improved ink absorption.

In contrast to the above invention, in the present invention, the specific surface area is 70 m2/!
By selecting a light calcium carbonate pigment of i' or higher and coating it on the base paper, a printed matter with high color density and clarity can be obtained, and at the same time, it can be Unlike amorphous silica, a fixed (crystalline) light calcium carbonate pigment is used, and the sedimentation volume of the light calcium carbonate pigment-water slurry is 1. 0 m7/i
By selecting F or more, it is intended to improve ink absorbency.

Generally, the method of measuring sedimentation velocity is known as a method for evaluating the degree of dispersion of fine powder in a dispersion medium.Particles that are aggregated in a dispersion medium have large sedimentation rates with many gaps between particles. Volume is indicated; well-dispersed particles exhibit a small settled volume that is closely packed. Therefore, by comparing the size of the sedimentation volume (the size of the sedimentation height), the dispersibility or flocculation of the particles can be evaluated.

Conditions for the comparison of sedimentation volumes can be determined as appropriate based on data.

The most common method for measuring the sedimentation rate of an inorganic pigment-water slurry is one that utilizes natural sedimentation, but the light calcium carbonate pigment used in the present invention has a specific surface area of Since it is very thick and therefore difficult to settle using natural sedimentation, the following method using centrifugal force was used. That is, an equal weight of water and a dispersant (Aron A600'l manufactured by Toagosei Co., Ltd.) are added to the inorganic pigment to form a slurry. Transfer to a graduated centrifuge tube for swing-type centrifuges and incubate at 20°C at 1600G (3100 rpm) for 30 minutes.
After centrifugation was continued in the centrifuge for 0 minutes, the volume of sedimentation (m4/li') per weight of the resulting sediment was calculated.

For ordinary calcium carbonate pigments, no particular correlation is found between the sedimentation volume calculated in the above-mentioned manner and the BET specific surface area, as described in the Examples described later. Especially with the light calcium carbonate pigment used in the invention, extremely high sedimentation volume values can be obtained. The reason for this is, as mentioned above, that the light carnoum carbonate pigment used in the present invention has a special shape in which rectangular parallelepiped ultrafine particles are connected in a chain. When the light calcium carbonate pigment used in the above is applied to a base paper, the coating layer becomes bulky, which is thought to be the reason for the improvement in ink absorption. .

Regarding the gloss of coated paper, in coated papers in which calcium carbonate pigments are generally used, the smaller the particle size of Cal-Z-lam carbonate is from 5 μm to approximately 0.05 μm, and therefore the larger the specific surface area, the more Although the gloss is improved, it is 0.0
It is said that the improvement in gloss reaches a plateau at around 5 μm.

As shown in the Examples below, coated paper using calcium carbonate with a large specific surface area, except for the light calcium carbonate pigment used in the present invention, generally tends to be glossy, but on the other hand, it has poor ink absorption. It is clear that the light calcium carbonate pigment used in the present invention is superior in all three aspects of gloss, ink absorption, and color density for the reasons mentioned above.

In the present invention, the synthetic polymer binder used in combination with the above-mentioned light calcium carbonate pigment includes polyvinyl alcohol or its derivatives, oxidized or modified starch, and gums such as guar gum.

Sodium alginate, casein, gelatin, vegetable protein, water-soluble cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, and carboxymethyl cellulose, polyvinylpyrrolidone and other arbitrary water-soluble polymer binders, and styrene-butadiene copolymers (SBR).
Synthetic polymer latexes such as acrylonitrile-butadiene copolymer (NBR latex), methyl methacrylate-butadiene copolymer (MBR latex), chloroprene latex, and ethylene-hinyl acetate copolymer latex can be used. However, from the standpoint of ink absorption, latex binders are more suitable than water-soluble polymer binders because they tend to create fine gaps between pigment particles during drying of the coating layer.

When adjusting the paint, it is desirable to use a relatively large amount of pigment, such as a solid content ratio of the light calcium carbonate pigment and binder of about 60 to 95 to 40 to 5. In addition, if necessary, pigment components such as kaolin, various clays, talc, aluminum hydroxide and other metal hydroxides, calcium carbonate, magnesium carbonate and other carbonates, barium sulfate, white carbon, calcium silicate or synthetic silicates, Diatomaceous earth, calcium sulfate, colloidal silica, titanium white, etc., polycations, etc. may be used as a water-resistant agent, and a portion of a dispersant, a fluidizing agent, a lubricant, an antifoaming agent, etc. may be used in combination.

When applying paint, use blades, air knives, bars,
Any coating machine such as a roll or size press can be used, and the coating amount is 5 to 50 f? on one side.
/m2 is appropriate.

Example The configuration of the present invention will be explained below according to examples.

1. In order to test the quality of the recording paper according to the present invention, solid printing was performed in each of the four colors black, cyan, magenta and yellow using an inkjet color image printer 10-0700 manufactured by Sharp Corporation. The color density of each recorded printed matter is determined by using the following SPI filters: visual for black for the black printed portion, red for cyan for the cyan printed portion, green for magenta for the magenta printed portion, and blue for yellow for the yellow printed portion. The gloss was measured using a Macbeth densitometer at 75° for the magenta printed area before and after printing.
It was measured with a gloss meter (manufactured by Murakami Color Research Laboratory).

In addition, regarding ink absorption, when performing solid printing (two-color overlapping printing) using the printer, if it is set so that a part of the solid printing part is in contact with the paper presser roll,
If the paper is fed immediately after the printing is finished, the solid printing part will pass the paper presser roll surface after 0.6 seconds, so up to the moment of this passing (0.6 seconds after printing). If the ink in the solid printed area is not dried within 6 seconds), the ink in the solid printed area will adhere to the surface of the paper presser roll, causing obvious stains on the roll surface. Therefore,
If the ink dries within the above 0.6 seconds and no stains appear on the paper surface, it is marked as ○, and if stains occur, it is marked as ×.
Table 1].

Example 1 Light calcium carbonate pigments and heavy calcium carbonate were used as PC, Brilliant 15. PY (all manufactured by Shiraishi Kogyo Co., Ltd.), Toyo Fine TF-X (manufactured by Toyo Denka Kogyo Co., Ltd.), and Super 150.0 (manufactured by Maruo Calcium Co., Ltd.).

Calpital 90 (manufactured by Fuji Kaolin Co., Ltd.) is made into a slurry by adding water and dispersants Aron and A6001 (manufactured by Toagosei Kagaku Co., Ltd.), and SBR latex (LX4) is added to 100 parts by weight (solid content) of the slurry.
07G.

30% liquid of Nippon Zeon Co., Ltd.) and fully Mated polyvinyl alcohol (PVA117. made by Kuraray Co., Ltd.)
Mix 7.5 parts by weight (solid content) of 15% liquid [Table 1]
Seven types of paints were prepared as shown below. Each of the above paints was applied to the Steckigt size for 20 seconds.

6597m2. It was applied with a wire bar to a coating amount of 2517 m2 on a 72 μm thick high-quality paper, and after drying, it was calendered with a test super calender manufactured by Yuri Roll Co., Ltd. at 14 ON, 7 cm, and coated type inkjet. Recording paper 16.1~'
116.7 was obtained.

In addition, the coating base paper for each coated paper, a commercially available coated type inkjet recording paper provided with a coating layer consisting of white carbon (SiO2) as a pigment and a water-soluble polymer binder, was used in the same manner as the samples. Calendar linear pressure 140
Samples subjected to supercalendering at kV/crn, commercially available typical coated papers, and art papers were also used as comparison samples (boiled 8 to 11).

The recording physical property evaluation test results of the sample Al-plate 11 are shown in Table 1.
].

Although there are various synthetic polymer latex binders other than SBR, in this example, for comparison,
In particular, SRR latex is used in accordance with the treatment of glossy coated paper, and it goes without saying that the synthetic polymer latex used is not limited to SBR.

Recording paper according to the present invention specified in [Table 1] &6
and Boiled 7, the gloss of the blank paper is 50.2-59.1%, and the gloss of the stamp surface after printing is 53.3-59.1%.
At 60.6%, it far exceeds the gloss level of 45%, which is the lower limit of European cross-coated paper standards, and print color density is also 3.
．． 31 to 3.57, which is high, and the ink absorption and drying properties are also good.

Said sample A6. Compared to A7, sample/I61 is a reference example containing light or heavy calcium carbonate with a small specific surface area.
~A5 recording paper has a color density of 1.90~2.
It is low at 72. However, the gloss of the blank paper and stamp surface was 46.6% or more for sample names 3 to 5, which had a slightly larger specific surface area.
The ink absorption properties of samples A 2 , , 116.4 and 55 containing light calcium carbonate having a sedimentation volume of 1.0 m/S' or more as specified in the claims of the present invention
The results were good for each recording paper.

That is, each of the recording sheets of Sample Al-Flat 5, which is a reference example, has one or more of the three items of color density, gloss, and ink absorbency as Example Sample A6. It is clear that it is inferior to &7 and cannot be used in actual use.

Sample No. 9, a commercially coated inkjet paper containing white carbon and a water-soluble binder, had extremely high color density and good ink absorption, but had very low gloss and was not used as a base paper for coating. Sample A8, which is a high-quality paper, was inferior in all three items above, and was inferior to commercially available coated paper (
Although sample Al0) and art paper (sample A11) exhibited high values in terms of both gloss and color density, their ink absorption was extremely poor, and as a result, ink flowed out significantly.

Effects of the Invention The present invention provides a coating comprising a light calcium carbonate pigment having a specific surface area of 70 m27f or more and a sedimentation volume of 1.0 m/f' or more and a polymer binder as specified in the claims. It is a recording paper with excellent ink receptivity that is provided with a layer, for example, the gloss of the inkjet-recorded stamp surface is much better than that of conventional paper, and the color density and
Sharpness.

It is an object of the present invention to provide a recording paper that has excellent ink absorbency, writability, etc., has a high recording speed, is suitable for multicolor inkjet recording, and has excellent ink receptivity and is also suitable for supercalender finishing. It was made.

Claims (1)

[Claims] 1. On the base paper, the specific surface area measured by the BET method is 7.
0 m^2/g or more, and a light calcium carbonate pigment having a sedimentation volume of 1.0 ml/g or more after centrifuging a 25 g sample at 20° C. for 30 minutes under a relative centrifugal force of 1600 G. A recording paper with excellent ink receptivity, characterized by being provided with a coating layer containing a polymer binder. 2. A recording paper with excellent ink receptivity according to claim 1, wherein the polymer binder is a synthetic polymer latex. 3. Claim 1 with super calender finish
A recording paper with excellent ink receptivity according to item 1 or 2.