JP6956654B2 - Non-reversible display ink for pen paper - Google Patents

Description

The present invention relates to an ink for forming an irreversible display on a pen paper that can be repeatedly written with water.

The water brush paper is a specially processed paper that can be repeatedly written with a brush or the like (Patent Document 1). The water brush paper is a colored layer obtained by applying and drying a coloring material such as black with a binder on the base paper, and on the outermost surface obtained by applying and drying a white low refractive index pigment together with a binder. The located white layers are laminated in this order.
Since the difference in refractive index between the pigment in the white layer and the air is large and light is scattered, the water brush paper has a white appearance when dried. When the pen paper gets wet with water, the water fills the gaps between the pigments in the white layer. Then, since the difference in refractive index between the pigment and water is small, the light is not scattered in the white layer, the hiding power of the white layer is lowered, and the color tone of the colored layer located in the lower part of the white layer is revealed and the color tone is changed. Change. Then, in the pen paper wet with water, the water permeates or evaporates with the passage of time and disappears from the white layer, so that the white layer returns to a white tone and is restored to the pen paper before writing.
Taking advantage of such performance, penmanship paper is used for practicing brush writing, children's toys, and the like.

On the other hand, there is also a desire to permanently preserve the image formed on the pen paper, and Patent Document 2 describes a solid substance having a refractive index of 1.3 to 1.8 and showing a solid state at 20 ° C. Compositions made by dissolving / or dispersing have been proposed.
The invention described in Patent Document 2 is required to uniformly dissolve the solid material or to make the solid material finer and to have dispersion stability so that the solid material can penetrate into the fine gaps existing between the pigments.

Japanese Unexamined Patent Publication No. 2012-206491 Japanese Unexamined Patent Publication No. 2005-15777

An object of the present invention is to provide an irreversible display ink for pen paper.

The means for solving the problem of the present invention is as follows.
An irreversible display ink for pen paper, which comprises a non-volatile liquid having a viscosity at 1.23 ° C. of 500 mPa · s or more and 100,000 mPa · s or less.
2. The viscosity at 23 ° C. is 30 mPa · s or more and 300 mPa · s or less. Non-reversible display ink for pen paper described in.
3. 3. The non-volatile liquid is a drying oil. Or 2. Non-reversible display ink for pen paper described in.

The irreversible display ink for pen paper of the present invention fills the gaps between the pigments of the pen paper with a non-volatile liquid, and since it does not contain a solid substance, it is easy to manufacture and has excellent storage stability. The irreversible display ink for pen paper of the present invention preserves an image with a non-volatile liquid. However, since the non-volatile liquid has a high viscosity, the flow on the pen paper is small and the shape of the image changes with time. Can be suppressed.

The present invention relates to an irreversible display ink for pen paper containing a non-volatile liquid having a viscosity at 23 ° C. of 500 mPa · s or more and 100,000 mPa · s or less.

"Non-volatile liquid"
In the present invention, the non-volatile liquid means a compound that is liquid at 20 ° C. and does not boil at 150 ° C. at 1 atm.
The non-volatile liquid used in the irreversible display ink for pen paper of the present invention is characterized by having a viscosity at 23 ° C. of 500 mPa · s or more and 100,000 mPa · s or less. If this viscosity is less than 500 mPa · s, the fluidity of the non-volatile liquid is large, and the formed image is deformed due to bleeding over time. Further, when this viscosity is larger than 100,000 mPa · s, the amount of the volatile solvent added in order to obtain a suitable viscosity for the ink increases, so that the shape at the time of coating composed of the non-volatile liquid and the volatile solvent is used. , The volatile solvent volatilizes, and the difference from the shape after drying, which consists only of a non-volatile liquid, becomes large. The viscosity at 23 ° C. is more preferably 4,000 mPa · s or more and 50,000 mPa · s or less, and further preferably 8,000 mPa · s or more and 30,000 mPa · s or less.

The non-volatile liquid used in the present invention can be used without particular limitation as long as it satisfies the above viscosity. For example, dry oil such as polymerized flaxseed oil and polyethylene glycol dehydrated castor oil, and non-drying oil such as castor oil. , Nonionic surfactants with a freezing point of less than 20 ° C (polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene-polyoxypropylene-alkyl ether, polyoxyalkylene ether, polyoxyethylene monoalkyl ester, sorbitan monoalkyl Esters, polyoxyethylene sorbitan monoalkyl esters, glycerin monofatty acid esters, polyoxyethylene glycerin monofatty acid esters, polyglycerin alkyl esters, polyalkylene glycol derivatives, etc.) and the like. Among these, drying oil is particularly preferable because it oxidatively polymerizes with oxygen in the air over time and solidifies, so that there is little bleeding, stickiness, etc., and the image can be stably stored.

"Reversible display ink for pen paper"
The irreversible display ink for pen paper of the present invention preferably has a viscosity of 30 mPa · s or more and 300 mPa · s or less at 23 ° C. as a whole ink. When the viscosity of the ink as a whole is within the above range, the writing feeling with a brush is excellent. The viscosity of the irreversible display ink for pen paper of the present invention as a whole is not limited to the above range. For example, when an image is formed by a stamp or the like, the viscosity is larger than 300 mPa · s and 5000 mPa.・ It can be less than or equal to s.

"Volatile solvent"
In order to make the viscosity of the ink as a whole 30 mPa · s or more and 300 mPa · s or less, a volatile solvent may be added to dilute the highly viscous non-volatile liquid. At this time, the amount of the volatile solvent added is preferably 200 parts by mass or less with respect to 100 parts by mass of the non-volatile liquid. If the amount of the volatile solvent added to 100 parts by mass of the non-volatile liquid is more than 200 parts by mass, the amount of the volatile solvent to be added becomes too large, and the shape at the time of coating composed of the non-volatile liquid and the volatile solvent, and the shape at the time of coating. The difference from the shape after drying, which consists only of the non-volatile liquid, becomes large. In the present invention, the volatile solvent means a compound having a boiling point of 130 ° C. or lower.

As the volatile solvent used in the present invention, water and an organic solvent can be used without particular limitation. Examples of the organic solvent include alcohols such as methanol, ethanol, n-propanol and isopropanol, hydrocarbons such as n-hexane, n-heptane and n-octane, propyl formate, butyl formate, propyl acetate, butyl acetate and the like. Ester type, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, methyl isobutyl ketone and other ketone type, ethylene glycol monomethyl ether and other ether type and the like can be used. In order to adjust the aroma of the volatile solvent, a small amount of liquid fragrance (limonene, linalool, citral, etc.) that becomes liquid at 20 ° C. can be added.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited thereto.
"Experiment 1"
The non-volatile liquid shown in Table 1 below was used as a sample. The viscosity of each sample was No. 1 at 23 ° C. using a Brookfield type viscometer (B type viscometer, manufactured by Tokyo Keiki Co., Ltd.). 3 or No. It was measured at a rotation speed of 6 rpm using a rotor of 4. The refractive index is the value at 20 ° C. on the D line (589 nm) of sodium. In addition, using each sample as a paint, write kana characters on commercially available water brush paper CA black (manufactured by Nippon Paper Papilia Co., Ltd.) using a pen for water brush paper (manufactured by Kuretake Co., Ltd.), and writeability and bleeding are as follows. It was evaluated on a three-point scale. Table 1 shows the evaluation results. The water brush paper CA black uses art paper as a base paper, has a black base layer composed of a black pigment and a binder resin emulsion on one side, and is porous on which a pigment such as fine particle silica and a binder resin emulsion. It is a multi-layer coated paper with a structure in which white layers are laminated.

"Writability"
◯: Has moderate viscosity and is easy to carry when writing.
X: The viscosity is high, and the resistance is large when writing, causing blurring.
XX: Very viscous and difficult to include in the brush.
"Blur"
◯: Even after 24 hours of writing, the original shape is maintained without bleeding.
X: After 24 hours of writing, it spreads due to bleeding and the original shape is not maintained.

Samples 1 to 6 having a viscosity of 500 mPa · s or more and 100,000 mPa · s or less had high viscosity and had some difficulty in writing, but the written characters maintained their original shape without bleeding.
Samples 7 to 11 having a viscosity of less than 500 mPa · s were excellent in writability, but the written characters spread over time and could not maintain the original shape.
The sample 12 having a viscosity higher than 100,000 mPa · s had a high viscosity and was difficult to include in the brush. Since the sample 12 could not be written, the bleeding evaluation was not performed.

"Experiment 2"
If necessary, a volatile solvent was added to the non-volatile liquid used in Experiment 1 to adjust the viscosity, and the ink was used as an irreversible display ink for pen paper in Examples and Comparative Examples. Types of volatile solvent added to each irreversible display ink for water brush paper in Examples and Comparative Examples, parts by mass of volatile solvent added to 100 parts by mass of non-volatile liquid, viscosity of ink (B-type viscometer, rotation) Number 60 rpm, No. 2 rotor used, value at 23 ° C.) was measured. In addition, the following evaluation was performed using each sample and commercially available pen paper CA Black (manufactured by Nippon Paper Papylia Co., Ltd.). Table 2 shows the evaluation results.

"Writability"
Kana characters were written on the water brush paper CA black (manufactured by Nippon Paper Papylia Co., Ltd.) using a brush pen for water brush paper (manufactured by Kuretake Co., Ltd.), and the writeability was evaluated in the following three stages.
◯: Has moderate viscosity and is easy to carry when writing.
Δ: The viscosity is low, and dripping occurs from the brush.
X: High viscosity, high resistance during writing, and blurring occurs.

"Concentration maintenance"
Using a small desktop printing tester (manufactured by RK Print Coated Instruments Co., Ltd.) equipped with a gravure plate (plate size 106 x 155 mm, solid plate), for each of the example and comparative examples of ink-painted paper CA black. The irreversible display ink was solid-printed by a gravure coating method and then dried to volatilize the volatile solvent to prepare a coated paper ^{having a non-volatile liquid adhering amount of 12 to 17 g / m 2.}
The color density of the portion colored by the adhesion of the non-volatile liquid was visually observed immediately after coating, 4 hours, 1 day, and 30 days after coating, and evaluated in the following three stages.
◯: The color development image density is the same as immediately after color development.
Δ: The colored image is lightened but can be visually recognized.
X: The colored image is extremely lightened and difficult to see.

"Area change rate"
The color-developed area of the gravure-coated sample was measured from the captured image of the color-developed portion using an image analyzer (dot analyzer DA-5000S type, manufactured by Oji Measuring Instruments Co., Ltd.). From the measured color development area, the area change rate was calculated by the following formula.
Area change rate (%) = Colored area after 4 hours of coating ÷ Area of gravure plate x 100

"Shape retention"
For the gravure-coated sample and the kana characters written with a brush pen for water brush paper (manufactured by Kuretake Co., Ltd.), visually observe the shape of the colored part due to the adhesion of the non-volatile liquid 4 hours, 1 day, and 30 days after coating. , The shape was evaluated in the following three stages in comparison with the shape immediately after coating.
◯: The visual shape is the same as immediately after color development.
Δ: Slight deformation is observed in the visual shape.
X: A large change is seen in the visual shape.

Examples 1 to 9 in which the viscosity of the irreversible display ink at 23 ° C. was 30 mPa · s or more and 300 mPa · s or less were excellent in writeability with a brush. Further, Examples 1 to 5 containing a non-volatile liquid having a viscosity at 23 ° C. of 9900 mPa · s to 17,600 mPa · s were excellent in shape retention and could maintain the same image even after 30 days.

Comparative Examples 1, 4 to 8 in which the viscosity of the irreversible display ink at 23 ° C. was 30 mPa · s or more and 300 mPa · s or less were excellent in writeability with a brush. However, in Comparative Examples 1, 4 to 7, the viscosity of the contained non-volatile liquid at 23 ° C. was as small as less than 500 mPa · s and spread over time, so that the area change rate was as large as 120% or more and the shape could not be maintained. Further, in Comparative Example 8, since the amount of water, which is a volatile solvent contained, is large, the characters become thinner due to the volatilization of water, and the contour is partially lost to reduce the area of the colored portion, resulting in an area change. The rate changed below 100% and the shape changed.
In Comparative Example 2 in which the viscosity at 23 ° C. was larger than 300 mPa · s, resistance was large and faintness occurred when writing with a brush.
In Comparative Examples 3 and 9 in which the viscosity at 23 ° C. was smaller than 30 mPa · s, dripping from the brush occurred. Further, in Comparative Examples 3 and 9, since the amount of n-heptane or water contained as a volatile solvent is large, the characters are thinned by volatilization of these, and the decolorized portion is formed in the outline portion or the inside of the coloring region. The area change rate was significantly less than 100%, and the shape immediately after color development could not be maintained.

Claims (3)

An irreversible display ink for pen paper, which comprises a non-volatile liquid having a viscosity at 23 ° C. of 500 mPa · s or more and 100,000 mPa · s or less. The irreversible display ink for pen paper according to claim 1, wherein the viscosity at 23 ° C. is 30 mPa · s or more and 300 mPa · s or less. The irreversible display ink for pen paper according to claim 1 or 2, wherein the non-volatile liquid is a drying oil.