JP6840536B2 - Aqueous ink composition for writing instruments and writing instruments using it - Google Patents

Description

The present invention relates to a water-based ink composition for writing instruments. More specifically, the present invention relates to a water-based ink composition for writing instruments containing a pigment, nanocellulose, and hydroxyalkylcellulose. The present invention also relates to a writing instrument using the composition.

Conventionally, as a pigment, a water-based ink composition for writing instruments using a thermochromic microcapsule pigment in which a reversible thermochromic composition is encapsulated in microcapsules has been known. Writing instruments that use these inks for ballpoint pens and markers are known, but the microcapsule pigment may settle or float due to the difference in specific gravity between the microcapsule pigment and the vehicle that disperses it. Therefore, in order to stably disperse the microcapsule pigment, a shear thinning agent such as a so-called gelling agent is blended (for example, Patent Document 1), or a polymer flocculant is used to form a loose bridging structure. The water-based ink composition was prepared by improving the redispersibility of the microcapsule pigment (for example, Patent Document 2). However, the water-based ink composition has a high apparent viscosity, and it is difficult to use it for a writing instrument having an ink supply mechanism using a comb groove using a low-viscosity ink represented by a fountain pen. There were problems such as faint handwriting and ink not being able to be supplied to the tip of the writing.

On the other hand, nanocellulose is actively used in water-based ink compositions (for example, Patent Document 3). Patent Document 3 describes that a specific cellulose fiber is used for an aqueous ink composition and a writing instrument, but the writing instrument has an ink viscosity of several tens of mPa · s or more and has an ink supply mechanism using a comb groove. When used in a writing instrument that is used by filling in, the ink viscosity is high, the brush strokes may be blurred, and ink may not be supplied. As with the above-mentioned water-based ink composition, the ink composition was not sufficiently satisfactory. ..

Japanese Unexamined Patent Publication No. 2014-189686 Japanese Unexamined Patent Publication No. 2015-10124 Japanese Unexamined Patent Publication No. 2013-181167

INDUSTRIAL APPLICABILITY The present invention suppresses the settling of pigments in a water-based ink composition for writing instruments, can suppress the settling even when used in low-viscosity writing instrument inks, and does not cause blurring in writing. A water-based ink composition for a writing instrument and a writing instrument using the same are provided.

The present invention has solved the above problems by blending nanocellulose and hydroxyalkylcellulose into a water-based ink composition for writing instruments.
That is, the present invention
"1. A water-based ink composition for writing instruments, which comprises a pigment, water, nanocellulose, and hydroxyalkylcellulose.
2. 2. The water-based ink composition for writing instruments according to item 1, wherein the pigment is a microcapsule pigment containing a functional material.
3. 3. The functional material is
(B) A component consisting of an electron-donating color-forming organic compound and
(B) A component consisting of an electron-accepting compound and
(C) A reaction medium that reversibly causes an electron transfer reaction by the components (a) and (b) in a specific temperature range.
The water-based ink composition for writing instruments according to item 2, wherein the composition is a reversible thermochromic composition comprising the above.
4. The writing instrument according to any one of items 1 to 3, wherein the nanocellulose is cellulose nanocrystal, and the number average fiber diameter thereof is 3 to 70 nm and the fiber length is 100 to 500 nm. Water-based ink composition.
5. The water-based ink for writing instruments according to any one of Items 1 to 4, wherein the viscosity measured at 30 rpm using a BL type viscometer at 20 ° C. is 1 to 20 mPa · s. Composition.
6. A writing instrument having a built-in water-based ink composition for a writing instrument according to any one of items 1 to 5.
7. The writing instrument according to item 6, wherein the writing instrument is a writing instrument provided with an ink flow rate adjusting mechanism using a comb groove. About.

According to the present invention, by using nanocellulose and hydroxyalkylcellulose together in a water-based ink composition for writing instruments, the ink viscosity becomes lower than when each of them is used alone, and even when the ink viscosity becomes low, the pigment It is possible to suppress the sedimentation of the ink composition, improve the storage stability of the water-based ink composition, and exert excellent effects such as no blurring of the writing stroke when writing.

It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment containing the heat decolorizing type reversible thermochromic composition. It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment containing the heat decolorizing type reversible thermochromic composition which has the color memory. It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment containing the heat-coloring type reversible thermochromic composition.

Hereinafter, embodiments of the present invention will be described in detail. In addition, in this specification, "part", "%", "ratio", etc. indicating a composition are based on mass unless otherwise specified.

The water-based ink composition for writing instruments according to the present invention (hereinafter, may be referred to as "water-based ink composition" or "composition" in some cases) uses a combination of nanocellulose and hydroxyalkylcellulose. This is one of the features. Hereinafter, each component constituting the water-based ink composition according to the present invention will be described.

(Nanocellulose)
The nanocellulose according to the present invention is cellulose that has been uniformly refined at the nano level, and is a fiber obtained by subjecting it to a treatment such as mechanical defibration. The nanocellulose used in the present invention is a so-called cellulose nanofiber, which is obtained by further treating a fiber having a fiber diameter of 1 to 100 nm and a fiber length of 5 μm or more and a large aspect ratio, and the cellulose nanofiber. Contains cellulose nanocrystals having a fiber diameter of 3 to 70 nm and a fiber length of about 100 to 500 nm. As a method for measuring the fiber diameter, fiber length, etc., it can be measured by an electron micrograph or the like.

The water-based writing ink composition according to the present invention contains nanocellulose, but the nanocellulose is not particularly limited as long as it can be uniformly dispersed in the water-based ink composition. Specifically, commercially available cellulose nanofibers and cellulose nanocrystals can be used. As commercially available cellulose nanofibers, "BiNFi-s" series manufactured by Sugino Machine Limited, "Serish" series manufactured by Daicel FineChem, "CNF" series manufactured by Chuetsu Pulp & Paper Co., Ltd., and the like can be used. The use of cellulose nanocrystals is particularly preferable because the ink viscosity is lowered and the fiber length is short, so that the ink flow is improved and the handwriting is not blurred while maintaining the dispersion stability.

The blending ratio of the nanocellulose is preferably 0.01 to 0.5% by mass, more preferably 0.02 to 0.3% by mass, based on the total mass of the aqueous ink composition. More preferably, it is 0.03 to 0.2% by mass. If it is less than the above range, the effect of maintaining a stable dispersion of the pigment by nanocellulose may not be sufficiently exhibited, and if it is more than the above range, the viscosity of the aqueous ink composition tends to increase, which is the aim. There is a possibility that it will not be possible to obtain a low-viscosity water-based ink composition. Within the above range, the viscosity of the aqueous ink composition can be lowered and the pigment can stably maintain a dispersed state due to the effect of the combined use with hydroxyalkyl cellulose, which will be described later, which is preferable.

The nanocellulose used in the present invention may be blended directly into the aqueous ink composition or may be blended as a dispersion.

(Hydroxyalkyl cellulose)
Examples of the hydroxyalkyl cellulose used in the present invention include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose and the like.

It is considered that the hydroxyalkyl cellulose used in the present invention has a function of causing a loose bridging action between pigments to form a loosely aggregated state and suppressing the aggregation of pigments. Hydroxyalkyl cellulose is particularly preferable because it can cause a loose bridging action without thickening the aqueous ink composition.

The blending ratio of the hydroxyalkyl cellulose is preferably 0.001 to 0.4% by mass, more preferably 0.005 to 0.3% by mass, based on the total mass of the aqueous ink composition. More preferably, it is 0.1 to 0.25% by mass. If it is less than the above range, pigments due to hydroxyalkyl cellulose tend to aggregate with each other, and if it is more than the above range, the viscosity of the water-based ink composition tends to be high, and the target low-viscosity water-based ink composition is observed. You may not be able to get it. Within the above range, the viscosity of the aqueous ink composition can be lowered due to the combined effect with nanocellulose, and the pigment can stably maintain a dispersed state, which is preferable.

One of the features of the water-based ink composition for writing instruments according to the present invention is that nanocellulose and hydroxyalkylcellulose are used in combination. The reason why the ink viscosity is lowered by using both of them together, the dispersion stability of the pigment is maintained even at that time, and the dispersion stability of the water-based ink composition is improved is presumed as follows.

In the water-based ink composition for writing instruments according to the present invention, nanocellulose is uniformly dispersed in the water-based ink composition. It is considered that the nanocellulose is kept in a state of being uniformly dispersed in a network shape by binding the functional group of cellulose and water molecules. On the other hand, as described above, hydroxyalkyl cellulose has a function of suppressing the aggregation of pigments by causing a loose bridging action between pigments to form a loosely aggregated state. Then, the loose aggregates formed by the pigment and the hydroxyalkyl cellulose are dispersed in a state of being incorporated into the mesh when the nanocellulose is made into a uniformly dispersed state. For this reason, it is possible to maintain a state in which the pigment is easily dispersed as compared with the case where the pigment is dispersed by nanocellulose or hydroxyalkylcellulose alone, so that even when the ink viscosity is low, the precipitation can be suppressed and the dispersed state can be maintained. It is thought that it can be kept stable.

It is particularly preferable that the blending ratio of the nanocellulose and the hydroxyalkylcellulose is 1: 10 to 1: 1 because the viscosity of the ink does not increase and the dispersion stability of the pigment can be maintained.

(Pigment)
In the present invention, pigments usually used for writing instrument inks and the like can be used as pigments. For example, in addition to organic pigments, plastic pigments, and inorganic pigments that are usually used for writing inks, metal powder pigments with metallic luster, colored metal powder pigments, metal vapor deposition powder pigments, glass flakes, and other colors such as iris are used. Non-color-changing pigments such as pearl pigments, liquid crystals, reversible thermo-color-changing compositions, microcapsule pigments containing functional materials such as photochromic materials, and the like can be used.

Specific examples of the organic pigment include Hansa Yellow, Benzidine Yellow, Permanent Red, Lake Red, Victoria Blue Lake, Phthalocyanine Blue, Phthalocyanine Green, and Aniline Black.

If you use plastic pigments that can select white or colorful pigments with relatively low specific gravity, which are easy to suppress settling in the water-based ink composition, some processed pigments have light specific gravity. When a pigment is used, the blending amount of the pigment itself can be increased, an aqueous ink composition with higher dispersion stability can be obtained, and the pigment can be used in combination with a pigment whose specific gravity has been lightened by processing. Is also very effective. Examples of plastic pigments include Low Pake OP-62, OP-84J, OP-91, HP1055 (all manufactured by Roam & Haas), Epocolor FP-1000N, FP-112, FP-113, and FP-113. FP-114, FP-115, FP-116, FP-117, FP-101, MA-1002FW, FP-1050 (all manufactured by Asahi Seigaku Co., Ltd.), Lumicol NKP-8604, Examples thereof include the same NKP-8605, the same NKP-8607, the same NKP-9203, the same NKP-9207, the same NKP-9237, and the same NKP-9238 (all manufactured by Nippon Fluorescent Chemical Co., Ltd.). Further, not only processed pigments but also pigments having a originally low specific gravity can be similarly improved in dispersion stability.

Examples of the inorganic pigment include carbon black, ultramarine blue, kaolin, and various titanium oxides such as rutile type and anatase type. Commercially available titanium oxides include Tytone SR-1, R-650, R-3L, A-110, A-150 (all manufactured by Sakai Chemical Industry Co., Ltd.), and Typaque R-580. R-550, R-780 (above, manufactured by Ishihara Sangyo Co., Ltd.), Kronos KR-310, KR-380, KR-480, KA-10, KA-15 (above, titanium industry (above) (Manufactured by Co., Ltd.), Typure R-900, R-931, R-960 (all manufactured by DuPont Japan Limited), Titanics JR-301, JR-600A, JR-603, JA -4 (above, manufactured by Teika Co., Ltd.) and the like. In addition, LIOFAST WHITE H201, EM WHITE H, EM WHITE FX9048 (all manufactured by Toyo Ink Co., Ltd.), Polx White PC-CR (manufactured by Sumitomo Color Co., Ltd.), FUJI SP WHITE 11, 1011 and 1036, same It is preferable to use a commercially available aqueous titanium oxide dispersion such as 1051 (all manufactured by Fuji Dye Co., Ltd.) because the dispersion step on the production side can be omitted and the ink can be easily converted into ink.

As the metal powder pigment, a metal powder pigment having a metallic luster such as aluminum powder, brass powder, stainless steel powder, and bronze powder may be used as it is, or a metal pigment in which a colorant is adsorbed on the metal powder pigment may be used. .. Further, the metal powder pigment such as aluminum powder may be processed in advance with a surfactant, a resin, a solvent or the like and dispersed to obtain a paste-like pigment dispersion or a liquid metal pigment dispersion. Further, the metal powder pigment such as aluminum powder is processed with a wax, a surfactant, a resin or the like, but a solid metal pigment or the like that does not contain a solvent may be used.

As aluminum paste, WXM0630, WB0230, 400SW, FM4010WG (above, manufactured by Toyo Aluminum Co., Ltd.) and the like, and as colored aluminum pigments, F503RG, F503BG, F500SI, F500RE, F500RE, F500BL (above, Toyo Aluminum Co., Ltd.) ), Etc., and solid RotosafeAqua250 042, 250 022, 260 003, etc. (all manufactured by ECKART Co., Ltd.).

As the aluminum powder, AA12, AA8, No. 900, No. There are 18,000 (above, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.).

As metal vapor deposition powder pigments, aluminum was vacuum-deposited on a synthetic resin, and the metal layer was protected by the resin and crushed into pieces. Made) and so on. Further, the resin layer was colored by LG R. Gold # 500, B.I. Gold # 500, R.M. Gold # 325, B.I. Gold # 325, Red # 325, Blue # 325, Green # 325, Violet # 325, Black # 325, Copper # 325, R.M. Gold # 200, B.I. Gold # 200, Red # 200, Blue # 200, Green # 200, Violet # 200, Black # 200, Copper # 200 (all manufactured by Oike Kogyo Co., Ltd.) and the like can be mentioned.

The glass flake pigments include Metashine REFSX-2025PS, -2025PS, -2040PS, RCFSX-5030NS, -5030NB, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS, -5030PS. 5090GG (all manufactured by Nippon Plate Glass Co., Ltd.) and the like can be mentioned.

Examples of pearl pigments include Iriodin 120 Rutile Satin, 123 Bright Rutile Satin, 201 Rutile Fine Gold, 211 Rutile Fine Red, 221 Rutile Fine Blue, 223 Rutile Fine, 223 Rutile Fine, and 223 Rutile Fine. , 323 Royal Gold Satin, 520 Bronze Satin, 522 Red Brown Satin, 524 Red Satin (all manufactured by Merck Japan Co., Ltd.) and the like.

Further, as the pigment according to the present invention, a microcapsule pigment containing a functional material can be used, but it is preferable because a handwriting with various functions can be obtained. Examples of the functional material include liquid crystals such as cholesteric liquid crystals and nematic liquid crystals, reversible thermochromic compositions, and photochromic materials.

Examples of the liquid crystal include Helicone HC SLM9002, 90120, 90220, 90320 (all manufactured by Wacker Chemie) and the like.

The reversible thermochromic microcapsule pigment that can be used in the present invention will be described below. The reversible thermochromic microcapsule pigment is defined at a predetermined temperature (discoloration point) described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-2398, and the like. It discolors before and after that, and exhibits a decolorized state in the temperature range above the high temperature side discoloration point and a color development state in the temperature range below the low temperature side discoloration point, and only one of the above two states exists in the normal temperature range. The other state is maintained as long as the heat or cold required for the state to develop is applied, but returns to the state exhibited in the normal temperature range when the heat or cold is not applied, hysteresis width. A reversible thermochromic microcapsule pigment containing a heat-decoloring type (decoloring by heating and developing color by cooling) having a relatively small characteristic (ΔH = 1 to 7 ° C.) is applied. Yes (see Figure 1).

_{Further, large hysteresis characteristics (ΔH B} = 8 to 50 ° C.) described in JP-A-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936 and the like. ), That is, when the shape of the curve plotting the change in coloring density due to temperature change increases the temperature from the lower temperature side than the discoloration temperature range, and conversely decreases it from the higher temperature side than the discoloration temperature range. The color changes by following a path that is significantly different from that of the above, and the color development state in the low temperature range below the _{complete color development temperature (t 1} ) or the decolorization state in the high temperature range above the _{complete decolorization temperature (t 4) is the specific temperature range.} [temperature range between t ₂ ~t ₃ (substantially two-phase retaining temperature region)] with heating decolorizable with color-memorizing (decolored by heating, color is by cooling) reversible thermochromic composition A reversible thermochromic microcapsule pigment containing the above can also be applied (see FIG. 2).

The hysteresis characteristics in the color concentration-temperature curve of the microcapsule pigment containing the reversible thermochromic composition will be described below with reference to the graph of FIG.

In FIG. 2, the vertical axis represents the color density and the horizontal axis represents the temperature. The change in color density due to temperature change progresses along the arrow. Here, A is _{a point indicating the concentration at a temperature t 4} (hereinafter, referred to as a complete decolorization temperature) at which a completely decolorized _{state is reached, and B is a temperature t 3} (hereinafter, a decolorization start temperature) at which decolorization begins. It is a point indicating the density at (referred to as), C is a point indicating the density at the temperature t ₂ at which color development starts (hereinafter referred to as the color development start temperature), and D is the temperature t ₁ (hereinafter referred to as) at which the color reaches a completely developed state. , Called the complete color development temperature).

Further, the length of the line segment EF is a measure indicating the contrast of discoloration, and the length of the line segment HG is a temperature width indicating the degree of hysteresis (hereinafter, referred to as a hysteresis width ΔH), and the larger this ΔH value is, the more. , It is easy to maintain each state before and after discoloration.

Here, _{the difference between t 4} and t ₃ or the difference between t ₂ and t ₁ (Δt) is a measure of the sensitivity of discoloration.

Further, among the decolorizing states of the reversible thermochromic composition, only one specific state (coloring state) exists in the normal temperature range, and the brush strokes of the reversible thermochromic composition can be easily generated by frictional heat generated by friction. In order to discolor (decolorize), it is preferable that the complete decolorization temperature (t ₄ ) is 50 to 95 ° C. and the color development start temperature (t ₂ ) is −50 to 10 ° C.

Here, in order to maintain the color development state in the normal temperature range and facilitate the discoloration due to the friction of the brush stroke, why the complete decolorization temperature (t ₄ ) is 50 to 95 ° C. and the color development start temperature (t ₂ ). Explaining whether the temperature is -50 to 10 ° C., when the heating is stopped in the state where the color development state _{passes through the decolorization start temperature (t 3} ) and does not reach the complete decolorization temperature (t ₄ ), the first state again. Even if the cooling is stopped before the complete color development temperature (t _{1 ) is reached after the color development start temperature (t 2} ) from the decolorization state, the color development state is maintained. Therefore, if the complete decolorization temperature (t ₄ ) is 50 ° C. or higher, which exceeds the normal temperature range, the color development state is maintained in the normal use state, and the color development start temperature (t ₂ ) is lower than the normal temperature range. At temperatures between -50 and 10 ° C, the decolorized state is maintained during normal use.

In the above-mentioned temperature setting of the complete decolorization temperature (t ₄ ), it is preferable that the temperature is higher in order for the color development state to be maintained in the normal use state, and the frictional heat due to friction is the complete decolorization temperature (t 4). It is preferable that the temperature is low in order to exceed t _4). Therefore, the complete decolorization temperature (t ₄ ) is preferably 50 to 90 ° C, more preferably 60 to 80 ° C. Further, in the temperature setting of the color development start temperature (t ₂ ) described above, it is preferable that the temperature is lower in order for the decolorized state to be maintained in the normal use state, and −50 to 5 ° C. is preferable. −50 to 0 ° C. is more preferable. In the present invention, the hysteresis width (ΔH) is in the range of 50 ° C. to 100 ° C., preferably 55 to 90 ° C., and more preferably 60 to 80 ° C.

As the microcapsule pigment that can be used in the water-based ink composition for writing according to the present invention, a reversible thermochromic composition having a _{complete decolorization temperature (t 4) on the higher temperature side than the discoloration temperature range can also be used.}

Of the decolorizing states of the reversible thermochromic composition, only one specific state (coloring state) is present in the normal temperature range, and the brush strokes of the reversible thermochromic composition are heated by heat obtained from a heat erasing tool or the like. In order to decolorize, the complete decolorization temperature (t ₄ ) is 80 ° C. or higher, and the color development start temperature (t ₂ ) is 15 ° C. or lower. Here, since the color development state can be maintained in the normal temperature range and the decolorization state is maintained in normal use, why the complete decolorization temperature (t ₄ ) is 80 ° C. or higher and the color development start temperature (t ₂ ). Explaining whether the temperature is 15 ° C. or lower, if the heating is stopped before the complete decolorization temperature (t _{4 ) is reached after passing through the decolorization start temperature (t 3} ) from the color development state, the temperature returns to the first state again. This is because the color development state is maintained even if the cooling is stopped in the state where the _{color development start temperature (t 2} ) is not reached from the decolorization state and the complete color development temperature (t _{1) is not reached.} If the complete decolorization temperature (t ₄ ) is 80 ° C or higher, which exceeds the normal temperature range, the color development state is maintained in a high temperature environment such as in a car in summer, and the color development start temperature (t ₂ ) is 15 ° C, which is lower than the normal temperature range. At the following temperatures, the decolorized state is maintained in normal use. Further, when the complete decolorization temperature (t ₄ ) is 90 ° C. or higher, the color development state is more maintained in a high temperature environment, and when the color development start temperature (t ₂ ) is 10 ° C. or lower, the decolorization state is normal. More maintained in use. Therefore, the temperature setting is an important requirement for selecting and selectively visualizing a handwriting in a discolored state on the writing surface, and the handwriting can achieve the intended purpose. In the above-mentioned temperature setting of the complete decolorization temperature (t ₄ ), it is preferable that the temperature is higher in order for the color development state to be maintained in a high temperature environment, and the complete decolorization temperature (t ₄ ) is preferably 90. ° C. or higher, more preferably 100 ° C. or higher. Further, in the temperature setting of the color development start temperature (t ₂ ) described above, it is preferable that the temperature is lower in order for the decolorized state to be maintained in the normal use state, and −50 to 10 ° C. is preferable. −50 to 5 ° C. is more preferable. In order to bring the reversible thermochromic composition into a color-developed state in advance, it is preferable to cool it in a general-purpose freezer as a cooling means, but considering the cooling capacity of the freezer, the temperature is limited to -50 ° C. Therefore, the complete color development temperature (t ₁ ) is −50 ° C. or higher. In the present invention, the hysteresis width (ΔH) is in the range of 70 ° C. to 150 ° C.

By using the reversible thermochromic composition, the handwriting formed on important documents does not fade even if left in a high temperature environment such as in a car in summer, and the range of application as a water-based ink composition for writing instruments. Can be expanded. Further, since it becomes difficult to erase due to rubbing by the friction member, it can be used to determine the authenticity of the document.

The components (a), (b), and (c) constituting the reversible thermochromic composition will be described below.

In the present invention, the component (a) donates an electron to the component (b) which is a color developer, and the cyclic structure such as the lactone ring of the component (a) is opened to develop an electron-donating color-developing property. It consists of an organic compound. Examples of such electron-donating color-developing organic compounds include diphenylmethanephthalides, phenylindrylphthalides, indolylphthalides, diphenylmethaneazaphthalides, phenylindrylazaphthalides, fluorans, and stirinoquinazolines. , Diazalodamin lactones, pyridines, quinazolines, bisquinazolines and the like.

The electron-accepting compound of the component (b) includes a group of compounds having an active proton, a group of pseudo-acidic compounds (a group of compounds that are not acids but act as acids in the composition to develop the color of component (a)), and electrons. There are a group of compounds having pores and the like.

Examples of compounds having an active proton include monophenols to polyphenols as compounds having a phenolic hydroxyl group, and alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxy groups and esters thereof as their substituents. Alternatively, those having an amide group, a halogen group and the like, bis-type and tris-type phenols and the like, phenol-aldehyde condensed resins and the like can be mentioned. Further, it may be a metal salt of the compound having a phenolic hydroxyl group.

Examples of the component (c) of the reaction medium that reversibly causes the electron transfer reaction by the components (a) and (b) in a specific temperature range include alcohols, esters, ketones, and ethers. ..

As the component (c), preferably, with respect to the color density-temperature curve, a large hysteresis characteristic (a curve plotting a change in coloring density due to a temperature change changes the temperature from a low temperature side to a high temperature side, and a case where the temperature changes from a low temperature side to a low temperature side A carboxylic acid ester compound having a ΔT value (melting point-cloud point) of 5 ° C. or higher and lower than 50 ° C. capable of forming a reversible thermochromic composition showing color memory, which changes color depending on the case of changing to the side). Used. Various compounds have been proposed as such compounds, and they can be arbitrarily selected and used, and specific examples thereof include the following.

（式中、Ｒ１は水素原子又はメチル基を示し、ｍは０〜２の整数を示し、Ｘ１、Ｘ２のいずれか一方は−（ＣＨ２）ｎＯＣＯＲ２又は−（ＣＨ２）ｎＣＯＯＲ２、他方は水素原子を示し、ｎは０〜２の整数を示し、Ｒ２は炭素数４以上のアルキル基又はアルケニル基を示し、Ｙ１及びＹ２は水素原子、炭素数１〜４のアルキル基、メトキシ基、又は、ハロゲンを示し、ｒ及びｐは１〜３の整数を示す。） First, as the component (c), a compound represented by the following general formula (1) described in JP-A-2006-137886 is preferably used.

(In the formula, R1 represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, one of X1 and X2 represents − (CH2) nOCOR2 or − (CH2) nCOOR2, and the other represents a hydrogen atom. , N represents an integer of 0 to 2, R2 represents an alkyl group or an alkenyl group having 4 or more carbon atoms, and Y1 and Y2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen. , R and p represent integers 1-3.)

Among the compounds represented by the formula (1), when R ₁ is a hydrogen atom, it is suitable because a reversible thermochromic composition having a wider hysteresis width can be obtained, and further, R ₁ is a hydrogen atom and , M is more preferably 0.

（式中のＲは炭素数８以上のアルキル基又はアルケニル基を示すが、好ましくは炭素数１０〜２４のアルキル基、更に好ましくは炭素数１２〜２２のアルキル基である。） Of the compounds represented by the formula (1), the compound represented by the following general formula (2) is more preferably used.

(R in the formula represents an alkyl group or an alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, and more preferably an alkyl group having 12 to 22 carbon atoms.)

（式中、Ｒは炭素数８以上のアルキル基又はアルケニル基を示し、ｍ及びｎはそれぞれ１〜３の整数を示し、Ｘ及びＹはそれぞれ水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲンを示す。） Further, as the component (c), a compound represented by the following general formula (3) can also be used.

(In the formula, R represents an alkyl group or an alkoxy group having 8 or more carbon atoms, m and n represent integers of 1 to 3 respectively, and X and Y represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and carbon, respectively. Indicates the number 1 to 4 alkoxy groups and halogens.)

Further, as the component (c), a compound represented by the following general formula (4) can also be used.

（式中、Ｘは水素原子、炭素数１〜４のアルキル基、メトキシ基、ハロゲン原子のいずれかを示し、ｍは１乃至３の整数を示し、ｎは１〜２０の整数を示す。） With a reaction medium that reversibly causes an electron transfer reaction by the (a) electron-donating color-forming organic compound, (b) electron-accepting compound, and (c) the above-mentioned (a) and (b) components in a specific temperature range. The reversible thermochromic microcapsule pigment in which the reversible thermochromic composition consisting of at least the above is encapsulated in microcapsules will be described below.

(In the formula, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen atom, m represents an integer of 1 to 3, and n represents an integer of 1 to 20.)

（式中、Ｒは炭素数１乃至２１のアルキル基又はアルケニル基を示し、ｎは１〜３の整数を示す。） Further, as the component (c), a compound represented by the following general formula (5) can also be used.

(In the formula, R represents an alkyl group or an alkenyl group having 1 to 21 carbon atoms, and n represents an integer of 1 to 3).

（式中、Ｘは水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲン原子のいずれかを示し、ｍは１〜３の整数を示し、ｎは１〜２０の整数を示す。） Further, as the component (c), a compound represented by the following general formula (6) can also be used.

(In the formula, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, m represents an integer of 1 to 3, and n represents 1 to 20. Indicates an integer of.)

（式中、Ｒは炭素数４〜２２のアルキル基、シクロアルキルアルキル基、シクロアルキル基、炭素数４〜２２のアルケニル基のいずれかを示し、Ｘは水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲン原子のいずれかを示し、ｎは０又は１を示す。） Further, as the component (c), a compound represented by the following general formula (7) can also be used.

(In the formula, R represents any of an alkyl group having 4 to 22 carbon atoms, a cycloalkyl alkyl group, a cycloalkyl group, and an alkoxy group having 4 to 22 carbon atoms, and X is a hydrogen atom and an alkyl having 1 to 4 carbon atoms. Indicates a group, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, and n indicates 0 or 1).

（式中、Ｒは炭素数３〜７のアルキル基を示し、Ｘは水素原子、メチル基、ハロゲン原子のいずれかを示し、Ｙは水素原子、メチル基のいずれかを示し、Ｚは水素原子、炭素数１〜４のアルキル基、炭素数１又は２のアルコキシ基、ハロゲン原子のいずれかを示す。） Further, as the component (c), a compound represented by the following general formula (8) can also be used.

(In the formula, R indicates an alkyl group having 3 to 7 carbon atoms, X indicates any of a hydrogen atom, a methyl group, and a halogen atom, Y indicates any of a hydrogen atom and a methyl group, and Z indicates a hydrogen atom. , An alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom.)

Further, as the electron-accepting compound, a specific alkoxyphenol compound having a linear or side-chain alkyl group having 3 to 18 carbon atoms may be used (Japanese Patent Laid-Open No. 11-129623, JP-A-11-5973), or a specific one. Hydroxybenzoic acid ester was used (Japanese Patent Laid-Open No. 2001-105732), gallic acid ester or the like was used (Japanese Patent Laid-Open No. 51-44706, Japanese Patent Application Laid-Open No. 2003-253149). It is also possible to apply a microcapsule pigment containing a reversible thermochromic composition (which is decolorized by cooling) (see FIG. 3).

The proportions of the constituents of the components (a), (b), and (c) depend on the concentration, the discoloration temperature, the discoloration form, and the type of each component, but generally, the desired discoloration characteristics can be obtained. The component ratio is in the range of (a) component 1, (b) component 0.1 to 50, preferably 0.5 to 20, (c) component 1 to 800, and preferably 5 to 200 (described above). All ratios are based on mass). Further, each component may be used as a mixture of two or more kinds.

The reversible thermochromic composition is encapsulated in microcapsules and used as a reversible thermochromic microcapsule pigment. This is because the reversible thermochromic composition can be kept in the same composition under various usage conditions and can exert the same action and effect.

Examples of the method for microencapsulating the reversible thermochromic composition include an interfacial polymerization method, an interfacial polycondensation method, an in-Situ polymerization method, an in-liquid curing coating method, a phase separation method from an aqueous solution, and a phase separation method from an organic solvent. , Melt-dispersion cooling method, air suspension coating method, spray-drying method, etc., which are appropriately selected according to the application. Further, a secondary resin film may be provided on the surface of the microcapsules according to the purpose to impart durability, or the surface characteristics may be modified for practical use.

Here, the mass ratio of the reversible thermochromic composition to the microcapsule wall film satisfies the range of 7: 1 to 1: 1, preferably 6: 1 to 1: 1.

The reversible thermochromic microcapsule pigment has an average particle size of 0.1 to 5 μm, preferably 0.1 to 3 μm, and more preferably 0.5 to 3 μm. If the average particle size exceeds 5 μm, the microcapsule pigment may lack dispersion stability, and if the average particle size is less than 0.1 μm, it becomes difficult to exhibit high-concentration color development. The particle size is measured using a laser diffraction / scattering type particle size distribution measuring device [manufactured by HORIBA, Ltd .; LA-300], and the average particle size (median size) is calculated based on the volume based on the value. To do.

When the ratio of the reversible thermochromic composition to the wall film is larger than the above range, the thickness of the wall film becomes too thin and the resistance to pressure and heat tends to decrease, and the ratio of the wall film to the reversible thermochromic composition. When is larger than the above range, the color density and sharpness at the time of color development are likely to decrease.

The reversible thermochromic microcapsule pigments include antioxidants, ultraviolet absorbers, infrared absorbers, solubilizers, preservatives / fungicides, non-thermochromic dyes and pigments as long as they do not affect their functions. Various additives such as and the like can be added.

The pigments may be used alone or in combination of two or more. Further, pigments and dyes having different specific gravities may be used in combination as long as the stability is not affected. Further, even a dye that is not completely dissolved in water can be used because it can obtain a sedimentation suppressing effect as insoluble particles. The amount of these pigments and / or dyes added is not particularly limited as long as a sufficient concentration can be obtained as a water-based ink composition for writing instruments. The particle size of these pigments and / or dyes is not particularly limited as long as it is within a range suitable for the recording method used.

The water-based ink composition for writing according to the present invention can be configured to contain at least a reversible thermochromic microcapsule pigment, water, nanocellulose and hydroxyalkylcellulose.

In the water-based ink composition, a non-thermally discoloring dye or pigment may be blended so as to form a handwriting that exhibits tautomerization from colored (1) to colored (2) due to a temperature change. it can.

Water and, if necessary, a water-soluble organic solvent are used as the medium of the water-based ink composition for writing according to the present invention. Examples of the water-soluble organic solvent include glycols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,3-butylene glycol and ethylene glycol monomethyl ether, and their lower alkyl ethers, 2-pyrrolidone and N-. Examples thereof include vinylpyrrolidone and urea.

Water and, if necessary, a water-soluble organic solvent are used as the medium of the water-based ink composition for writing according to the present invention. Examples of the water-soluble organic solvent include glycols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,3-butylene glycol and ethylene glycol monomethyl ether, and their lower alkyl ethers, 2-pyrrolidone and N-. Examples include vinylpyrrolidone.

Additives such as a moisturizer, a pH adjuster, a preservative, and an antifungal agent can be added to the water-based ink composition for writing instruments according to the present invention, if necessary.

Examples of the moisturizer include urea, sorbitol, and the like in addition to the water-soluble organic solvent. The amount of the moisturizer added is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, based on the water-based ink composition. If it is less than this range, the moisturizing property when used in a writing instrument tends to be inferior, and if it is more than this range, the dryness of the handwriting tends to be deteriorated and the ink viscosity tends to be improved.

In the present invention, it is preferable to use glycerin and urea together as a moisturizer because the precipitation of the pigment can be further suppressed and the dry-up performance when used in a writing instrument is improved.

When the ratio of the moisturizer is 25 to 40% by mass with respect to the total mass of the ink and the mixing ratio of glycerin and urea is 1: 1 to 1: 2.5, urea does not precipitate and the dry-up performance is improved. Therefore, it is particularly preferable.

Examples of the pH adjuster include inorganic salts such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide and sodium acetate, and organic basic compounds such as water-soluble amine compounds such as triethanolamine and diethanolamine.

As preservatives or antifungal agents, 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 2-methyl- 4,5-Trimethylene-4-isothiazolin-3one, N- (n-butyl) -1,2-benzisothiazolin-3-one, 2-pyridinethiol-1-oxide sodium, 3-iodo-2-propynylbutyl Carbamate sodium benzoate, benzotriazole and phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetrachloro-4- (methylsulfonyl) pyridine and the like. ..

Examples of the rust preventive include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrate, diisopropylammonium nitrate, sodium thiosulfate, saponin, and dialkylthiourea. Further, as the water-soluble resin, an acrylic resin, an alkyd resin, polyvinylpyrrolidone, polyvinyl alcohol and the like can be used. Further, as the resin emulsion, an emulsion containing an acrylic resin, a urethane resin, a styrene-butadiene resin, a polyester resin, a vinyl acetate resin or the like can be added.

Furthermore, a fluorine-based surfactant that improves the permeability of the solvent, a nonionic, anionic, cationic surfactant, and a defoaming agent such as dimethylpolysiloxane can be added.

The water-based ink composition for writing instruments has an ink viscosity of preferably 1 to 20 mPa · s, more preferably 3 to 10 mPa · s, measured at 20 ° C. using a BL type viscometer at 30 rpm. The water-based ink composition for writing instruments of the present invention exerts the maximum effect in suppressing pigment settling when used in a low-viscosity ink.

As the blending ratio of the pigment, the blending amount can be appropriately selected depending on the type of pigment used and the function to be obtained, but 1 to 50% by mass is preferable with respect to the total amount of the water-based ink composition for writing instruments. If it is less than this range, the color density tends to decrease, and if it exceeds this range, the ink viscosity in the water-based ink composition tends to increase, and there is a risk that low-viscosity ink cannot be obtained.

The water-based ink composition for writing instruments according to the present invention can be used as a water-based ink for various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens, and various markers. In particular, writing tools equipped with an ink supply mechanism utilizing the capillary phenomenon, such as writing tools equipped with an ink supply mechanism using a comb groove such as a perennial brush and writing tools equipped with an ink supply mechanism using a fiber bundle typified by markers, are Since it is not possible to use ink with high ink viscosity due to its ink supply mechanism, it is necessary to use ink with low viscosity. The handwriting may be blurred or it may become impossible to write. However, in the water-based ink composition for writing tools according to the present invention, it is possible to suppress the precipitation of the pigment even in a low-viscosity ink, so that it is preferably used. .. Further, a water-based ink composition using cellulose nanocrystals as nanocellulose is particularly preferably used because its fiber length is short and it does not get caught in fiber bundles or the like.

As described above, the water-based writing ink composition according to the present invention can be provided in various writing instruments, and handwriting can be formed by using the writing instruments. Further, when a thermochromic composition typified by a reversible thermochromic microcapsule pigment is used as a colorant, the handwriting (hereinafter, may be referred to as a thermochromic handwriting) may be scratched by a finger. The color can be changed by applying a heating tool or a cooling tool.

Examples of the heating tool include an energization heating discoloring tool equipped with a resistance heating element, a heating discoloring tool filled with hot water, and a hair dryer. However, a friction member is preferably used as a means capable of discoloring by a simple method. Be done. In particular, an elastic body that does not substantially wear when scraped is preferable.

As the friction member, an elastic body such as an elastomer or a plastic foam, which has a high elastic feeling and can generate an appropriate friction at the time of rubbing to generate frictional heat, is suitable. As the material of the friction member, a silicone resin, a SEBS resin (styrene ethylene butylene styrene block copolymer), a polyester resin, a polyester elastomer, or the like is used. As the friction member, a writing instrument set can be obtained by combining a writing instrument and a friction body which is a separate member having an arbitrary shape, but by providing the friction member in the writing instrument, the portability becomes excellent.

Examples of the cooling tool include a cold discoloring tool using a Peltier element, a cold discoloring tool filled with a refrigerant such as cold water and ice pieces, an ice pack, and an application of a refrigerator or a freezer.

The thermally discolorable handwriting can be discolored by applying a heat discoloring tool or a cold discoloring tool. Examples of the heating discoloring tool include an energization heating discoloring tool equipped with a resistance heating element such as a PTC element, a heating discoloring tool filled with a medium such as hot water, a heating discoloring tool using steam or laser light, and an application of a hair dryer. However, a current-carrying heating discoloring tool is preferably used. Examples of the energization heating discoloring tool include an energizing heating discoloring tool using a thermal head, a heat roller, and a hot stamp.

(Manufacture of Microcapsule Pigment A)
(A) 2.5 parts of 1,3-dimethyl-6-diethylaminofluorane as a component, 5.0 parts of 2,2-bis (4'-hydroxyphenyl) hexafluoropropane as a (b) component, 1,1- A reversible thermochromic composition having color memory and consisting of 3.0 parts of bis (4'-hydroxyphenyl) n-decane and 50.0 parts of 4-benzyloxyphenylethyl capricate as a component (c) is heated and dissolved. Then, a solution obtained by mixing 30.0 parts of an aromatic isocyanate prepolymer and 40.0 parts of an auxiliary solvent as a wall film material was emulsified and dispersed in an 8% aqueous solution of polyvinyl alcohol, and the mixture was continuously stirred while being heated, and then water-soluble. 2.5 parts of the aliphatic modified amine was added, and further stirring was continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The average particle size D of the microcapsule pigment is 2.0 μm, t ₁ : -18 ° C, t ₂ : -9 ° C, t ₃ : 45 ° C, t ₄ : 64 ° C, temperature-sensitive color-sensitive color memory. The composition showed a behavior having a hysteresis characteristic of wall film = 2.6: 1.0, and the color changed reversibly from orange to colorless and from colorless to orange.

(Example 1)
Reversible thermochromic microcapsule pigment A 15.0 parts by mass Cellulosic nanocrystal 0.05 parts by mass (fiber diameter 5 to 20 nm, fiber length 150 to 400 nm)
Hydroxyethyl cellulose 0.3 parts by mass Glycerin 14.0 parts by mass Urea 20.0 parts by mass Preservative 0.2 parts by mass (1,2-benzoisothiazolin-3-one manufactured by Arch Chemical Co., Ltd., trade name: Proxel XL-2)
50.45 parts by mass of water The above composition was stirred and mixed with a homogenizer to obtain a water-based ink composition for writing instruments.
The viscosity of the water-based ink composition was 6.6 mPa · s when measured at 20 ° C. and 30 rpm using a BL type viscometer.

(Examples 2-9, Comparative Examples 1-5)
A water-based ink composition for writing instruments was obtained in the same manner as in Example 1 with the formulations shown in Tables 1 and 2. Details of the materials used in these examples are as follows.
-Cellulose nanofibers (BiNFi-s FMa-1002, manufactured by Sugino Machine Limited)
-Cellulose nanocrystal (fiber diameter 5 to 20 nm, fiber length 150 to 400 nm)
-Preservative Proxel XL-2 (1,2-benzoisothiazolin-3-one, manufactured by Arch Chemical Co., Ltd.)

The water-based ink compositions for writing instruments obtained in Examples 1 to 9 and Comparative Examples 1 to 5 were visually evaluated for ink storage stability by the following method. The results are shown in Tables 1 and 2.
Dispersion stability: A 20 ml screw tube was filled with the water-based ink compositions for writing instruments of Examples 1 to 9 and Comparative Examples 1 to 5, and the dispersion stability was visually confirmed.
◯: Even after 2 weeks, no sedimentation or floating of the pigment was observed, and the pigment remained uniformly dispersed.
Δ: Slight sedimentation or floating of the pigment was observed after 2 weeks, but the pigment was dispersed almost uniformly.
X: After 3 days, the pigment is settled or suspended, and the dispersion stability of the pigment cannot be maintained.
XX: The pigment is settled or suspended after the screw tube is filled, and the dispersion stability cannot be maintained.
Writing performance test: A fountain pen (Lucina) manufactured by Pilot Corporation is filled with a water-based ink composition for writing instruments and left with the writing tip facing down for one day, and then printing paper A (manufactured by Nippon Paper Co., Ltd., Writing was performed on Shiraoi 46 format equivalent 55 kg), and the writing performance was evaluated.
◯: Good writeability with no blurring on the handwriting.
Δ: The handwriting is faint.
×: Writing is not possible.

As is clear from the results shown in Tables 1 and 2, the water-based ink composition for writing instruments according to the present invention in which nanocellulose and hydroxyalkylcellulose are used in combination is used by filling the writing instrument with good dispersion stability. Even when this was done, good handwriting was obtained, and it was clarified that it had excellent performance as a water-based ink composition for writing instruments. On the other hand, in Comparative Examples 1, 3 to 5, when the microcapsule pigment was stored in the screw tube, sedimentation of the microcapsule pigment was observed. Further, in Comparative Example 2, floating of the microcapsule pigment was observed, and the dispersion stability was inferior to that of Example. Further, the writing performance was also inferior due to a problem.

The water-based ink composition for writing instruments according to the present invention can be used as a water-based ink for various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens, and various markers. In particular, it can be suitably used for writing instruments that use low-viscosity ink.

t ₁ Complete color development temperature of the microcapsule pigment containing the heat decolorizing type reversible thermochromic composition t ₂ Color development start temperature of the microcapsule pigment containing the heat decolorizing reversible heat discoloring composition t ₃ Heat extinguishing Decolorization start temperature of microcapsule pigment containing color-type reversible thermochromic composition t ₄ Complete decolorization temperature of microcapsule pigment containing heat-decoloring reversible thermochromic composition T ₁ Heat-decoloring type Complete decolorization temperature of microcapsule pigment containing reversible thermochromic composition T ₂ Decolorization start temperature of microcapsule pigment containing reversible thermochromic composition T ₃ Heat reversible thermochromic complete coloring temperature ΔH hysteresis width of the microcapsule pigment enclosing a coloring initiation temperature T ₄ heating-color forming reversible thermochromic composition of the microcapsule pigment enclosing composition

Claims (8)

A water-based ink composition for writing instruments containing a pigment, water, nanocellulose, and hydroxyalkylcellulose.
The blending ratio of the hydroxyalkyl cellulose to the total mass of the ink composition for writing instruments is 0.001 to 0.4% by mass.
A water-based ink composition for writing instruments, wherein the viscosity of the water-based ink composition for writing instruments measured at 20 ° C. using a BL-type viscometer at 30 rpm is 1 to 20 mPa · s . The water-based ink composition for writing instruments according to claim 1, wherein the pigment is a microcapsule pigment containing a functional material. The functional material is
(B) A component consisting of an electron-donating color-forming organic compound and
(B) A component consisting of an electron-accepting compound and
(C) A reaction medium that reversibly causes an electron transfer reaction by the components (a) and (b) in a specific temperature range.
The water-based ink composition for writing instruments according to claim 2, wherein the composition is a reversible thermochromic composition comprising the above. The water-based writing instrument according to any one of claims 1 to 3, wherein the nanocellulose is cellulose nanocrystal, and the number average fiber diameter thereof is 3 to 70 nm and the fiber length is 100 to 500 nm. Ink composition. The invention according to any one of claims 1 to 4, wherein the hydroxyalkyl cellulose is at least one selected from the group consisting of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose. Aqueous ink composition for writing utensils. The water-based ink composition for writing instruments according to any one of claims 1 to 5, wherein the blending ratio of the nanocellulose and the hydroxyalkylcellulose is 1: 10 to 1: 1. A writing instrument comprising the water-based ink composition for a writing instrument according to any one of claims 1 to 6. The writing instrument according to claim 7 , wherein the writing instrument is a writing instrument provided with an ink flow rate adjusting mechanism using a comb groove.

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