Thermochromic ink composition for writing instruments and writing instruments containing the same

Abstract

The present invention provides a thermochromic ink composition for writing instruments and a writing instrument containing it, which, in a water-based ink with excellent drying properties using a sugar mixture, can achieve dispersion stability without increasing viscosity, even when using a material with poor dispersibility, such as a microcapsule pigment, as a coloring agent. [Solution] A thermochromic ink composition for writing instruments comprising a microcapsule pigment containing a thermochromic composition, water, sugar A which is a sugar mixture containing 30% by mass or more of starch saccharified products and / or reduced products thereof of 8 or more sugars, and sugar B which is 3 or less sugar, wherein the mass ratio of sugar A to sugar B incorporated in the ink is in the range of B / A ≥ 2, and a writing instrument containing the same.

Description

Technical Field

[0001] The present invention relates to a thermochromic ink composition for writing instruments. Further, it relates to a thermochromic ink composition for writing instruments having excellent dispersion stability and a writing instrument.

Background Art

[0002] In recent years, ballpoint pens and marking pens in which handwriting is heated and erased or discolored using frictional heat have become widely popular. In these writing instruments, as a colorant, a microcapsule pigment containing a thermochromic composition is used. However, since the pigment has poor dispersibility in an aqueous medium, a shear-thinning viscosity-imparting agent or a thickening agent is added to increase the viscosity of the ink, thereby ensuring dispersion stability in the ink. In a ballpoint pen using a shear-thinning viscosity-imparting agent together with the microcapsule pigment, there is a drawback that drying (drying up) due to moisture evaporation from the pen tip is likely to occur. Therefore, a technique of using in combination a sugar mixture containing 30% by mass or more of an oligosaccharide having 8 or more sugars and / or its reduced product together with the shear-thinning viscosity-imparting agent is disclosed (see, for example, Patent Documents 1 and 2).

[0003] The sugar mixture can suppress moisture evaporation from the pen tip by forming a brittle film when the pen tip of the ballpoint pen is exposed to air for a long time. When rewriting, by bringing the pen tip into contact with the paper surface, the film easily breaks, and thus good handwriting can be obtained from the beginning. In addition, since the ink viscosity can be increased by the addition, more stable pigment dispersibility can be obtained by adjusting the addition amount, and it is a material with high versatility in gel ink. However, when the addition amount to the ink is increased to increase the viscosity, blurring may occur in the handwriting, so adjustment of the addition amount is necessary. Further, in order to obtain the dispersion stability of the microcapsule pigment, it is necessary to use it in combination with a shear-thinning viscosity-imparting agent, so it was only applicable to refill-type ballpoint pens.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-174030 [Patent Document 2] Japanese Patent Publication No. 2011-178979 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention provides a thermochromic ink composition for writing instruments that incorporates this composition, which can be applied to structures other than refillable ballpoint pens. This composition is suitable for aqueous inks with excellent drying properties using the aforementioned sugar mixture, and allows for dispersion stability even when using materials with poor dispersibility, such as microcapsule pigments, as a coloring agent, without the need for shear viscosity reducers or increased viscosity. [Means for solving the problem]

[0006] The present invention comprises a microcapsule pigment containing a thermochromic composition, water, sugar A which is a sugar mixture containing 30% by mass or more of a starch saccharified product of 8 or more sugars and / or its reduced product, and sugar B which is 3 or less sugar. The requirement is a thermochromic ink composition for writing instruments in which the mass ratio of sugar A to sugar B in the ink is in the range of B / A ≥ 2. Furthermore, the requirements are that the ink composition contains sugar A in an amount of 0.5 to 5.0% by mass, sugar B is one or more selected from trehalose, palatinose, and fructose, and the microcapsule pigment is added in an amount of 10 to 35% by mass of the total amount of the ink composition. Furthermore, it is required that the product contains hollow particles, and that the particle size of the hollow particles is in the range of 0.1 to 1 times the particle size of the microcapsule pigment. Furthermore, the viscosity of the ink at 20°C must be in the range of 1 to 20 mPa·s. Furthermore, the requirements include a writing instrument containing a thermochromic ink composition for writing instruments described in any of the above, and comprising a friction member that changes the color of the writing made by the writing instrument due to frictional heat. [Effects of the Invention]

[0007] The present invention provides a thermochromic ink composition for writing instruments that, even when using a water-based ink with excellent drying properties using the aforementioned sugar mixture, is made possible without the use of shear viscosity reducers or increased viscosity, and even when using a material that is prone to settling and has poor dispersion stability, such as microcapsule pigments, as a coloring agent, excellent dispersion stability can be obtained even with a low viscosity ink. The invention also provides a writing instrument containing the aforementioned ink that can be developed into structures other than refillable ballpoint pens. Furthermore, by using hollow particles in combination, the ink flow during writing can be improved and stabilized, resulting in the formation of better handwriting. [Modes for carrying out the invention]

[0008] In this invention, we have found that in an aqueous ink with excellent drying properties using the aforementioned sugar mixture, even when a material that tends to settle, such as microcapsule pigments, is used as a coloring agent, the dispersion stability of the microcapsule pigments can be maintained without increasing the viscosity of the ink by using sugars of three saccharides or less in combination with the sugar mixture in a specific mixing ratio. Therefore, it is not limited to refillable ballpoint pens with a pipe in the ink reservoir, but can be widely applied to general-purpose writing instruments, resulting in a thermochromic writing instrument ink with excellent drying properties and dispersion stability, making it possible to form excellent handwriting in various types of writing instruments.

[0009] Microcapsule pigments containing thermochromic compositions are used as colorants. Any type of thermochromic composition encapsulated in microcapsules can be applied, regardless of whether the effect is reversible or irreversible. By heating or cooling the handwriting, the hue of the handwriting can be changed, or the color can be altered, removed, or colored. By encapsulating the thermochromic composition in microcapsules, the changes in the handwriting can be achieved stably over a long period without any changes in composition.

[0010] In particular, as the thermochromic composition encapsulated in the microcapsule pigment, a reversible thermochromic composition comprising (a) an electron-donating color-changing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction between the two occurs is preferred, from the viewpoint of repeated use and accuracy of temperature changes. Specifically, as microcapsule pigments containing the reversible thermochromic composition, we can use heat-decolorizing microcapsule pigments containing a reversible thermochromic composition, as described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc., which changes color before and after a predetermined temperature (color change point), exhibiting a decolorized state in the temperature range above the high-temperature color change point and a colored state in the temperature range below the low-temperature color change point, where only one of the two states exists in the room temperature range, and the other state is maintained as long as the heat or cold required to bring about that state is applied, but returns to the state exhibited in the room temperature range when the application of heat or cold is stopped, and which have a relatively small hysteresis width (ΔH=1~7℃). Furthermore, there are those exhibiting relatively large hysteresis characteristics (ΔH=8~50℃) as described in Japanese Patent Publication No. 4-17154, Japanese Patent Publication No. 7-179777, Japanese Patent Publication No. 7-33997, Japanese Patent Publication No. 8-39936, etc., and those exhibiting large hysteresis characteristics as described in Japanese Patent Publication No. 2006-137886, Japanese Patent Publication No. 2006-188660, Japanese Patent Publication No. 2008-45062, Japanese Patent Publication No. 2008-280523, etc. In other words, the shape of the curve plotting the change in color intensity due to temperature changes follows a significantly different path depending on whether the temperature is raised from a temperature below the color change temperature range or lowered from a temperature above the color change temperature range. This means that the color development state at low temperatures below the complete color development temperature, or the decolorization state at high temperatures above the complete decolorization temperature, can be determined by using a reversible thermochromic composition that has color memory properties in a specific temperature range, and heat-decolorizing microcapsule pigments can also be applied. Furthermore, as a reversible thermochromic composition having color memory properties that can be applied to writing instrument inks, the complete color development temperature is set to a temperature that can only be obtained in a freezer, a cold region, etc., i.e., -50 to 0°C, preferably -40 to -5°C, more preferably -30 to -10°C, and the complete decolorization temperature is set to a temperature that can be obtained from frictional heat from a friction body, a hair dryer, or other readily available heating source, i.e., 50 to 95°C, preferably 50 to 90°C, more preferably 60 to 80°C, and the ΔH value is set to 40 to 100°C, thereby enabling it to effectively maintain the color exhibited under normal conditions (daily living temperature range).

[0011] Microencapsulation of the aforementioned thermochromic composition can be carried out by interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid curing coating, phase separation from aqueous solutions, phase separation from organic solvents, melt-dispersion cooling, air suspension coating, spray drying, etc., and can be appropriately selected depending on the application. Furthermore, depending on the purpose, a secondary resin film can be applied to the surface of the microencapsulated pigment to provide durability or modify the surface properties for practical use. The aforementioned microcapsule pigments are applied with an average particle size in the range of approximately 0.1 to 4.0 μm, but those with an average particle size of 0.5 μm or more are particularly preferred for achieving high ink density in handwriting. When the average particle size is 0.5 μm or more, it becomes necessary to set a larger clearance in the ballpoint pen tip or to use a marking pen tip with a large porosity in order to eject the large particles, which increases the surface area of ​​the pen tip (ink ejection part) that is exposed to air, making it prone to drying out. Therefore, the composition of the present invention is particularly effective. Preferably, those in the range of 0.5 to 3.5 μm particularly satisfy practical requirements. Furthermore, the average particle diameter is measured using Mountec's image analysis-based particle size distribution software "MacView" to determine the particle area, calculate the projected area circle equivalent diameter (Heywood diameter) from the area of ​​the particle area, and then measure the average particle diameter of particles equivalent to an equivolute sphere based on that value. In addition, if the particle diameter of all or most of the particles exceeds 0.2 μm, it is also possible to measure the average particle diameter of particles equivalent to an equivolute sphere using the Coulter method with a particle size distribution analyzer (Beckman Coulter, Ltd., product name: Multisizer 4e).

[0012] The microcapsule pigments can be used individually or in appropriate mixtures of two or more types, and are used in an amount of 10 to 35% by weight, preferably 15 to 30% by weight, in the ink composition. Since the individual concentrations of the microcapsule pigments are lower than those of general-purpose colorants, their use within the above range is preferable from a practical standpoint regarding ink concentration. As a result, the ink is more likely to undergo high solid differentiation, making the configuration of the present invention effective. In this invention, we focused on microcapsule pigments containing the aforementioned thermochromic composition as a coloring agent and found the effects obtained from this. However, it is presumed that similar effects can be obtained with other color-changing materials such as light-color-changing materials, microcapsule pigments containing dyes or pigments, or colored resin particle pigments in which a coloring agent is incorporated into hollow or non-hollow resins.

[0013] Furthermore, to impart a desired hue to the handwriting without thermal discoloration, it is possible to use colorants (dyes and general pigments) that can be dissolved or dispersed in an aqueous medium. For example, as dyes, acid dyes, basic dyes, direct dyes, etc., can be used, and as general pigments, inorganic pigments such as carbon black and ultramarine, organic pigments such as copper phthalocyanine blue and benzidine yellow, and water-dispersible pigment products that have been finely and stably dispersed in an aqueous medium using surfactants, etc., can be used. In addition, metallic luster pigments such as metal powders and pearl pigments, fluorescent pigments, phosphorescent pigments, and white pigments such as titanium dioxide can also be applied. These can also be encapsulated in microcapsule pigments.

[0014] A sugar mixture (sugar A) containing 30% by mass or more of starch saccharified products and / or reduced products thereof, when added to an aqueous ink, can impart excellent drying resistance to inks with a high pigment content and that dry easily, such as the ink of the present invention. Preferably, the sugar mixture used contains 50% or more of eight or more sugars, and more preferably contains 70% or more of eight or more sugars. In writing instruments, to provide drying resistance to the pen tip, a film needs to form as the ink dries while the pen tip is exposed to the air. However, monosaccharides and disaccharides do not form a sufficient film, resulting in little effect on drying resistance. Furthermore, their high water absorption means that when applied to ballpoint pens, drooping is likely to occur if the tip is left upside down. While triploat to heptagosaccharides have lower water absorption than monosaccharides and disaccharides, they do not provide sufficient drying resistance. Therefore, if you try to add a large amount to obtain sufficient drying resistance, it may result in excessive viscosity, increased water absorption causing sagging, or an increase in solid content in the ink due to incomplete dissolution of the added sugar, thus worsening drying resistance. As the saccharides have the characteristic that their hygroscopicity decreases and they are more likely to form a film during drying as their molecular weight increases, using saccharides with 8 or more sugar units can improve the dry resistance without causing dripping under high humidity. Furthermore, as the proportion of saccharides with 8 or more sugar units increases, the film becomes brittle to impact, so when the pen tip touches the non-writing surface during writing, it is easily broken, and ink can be stably discharged from the writing.

[0015] As saccharides with 8 or more sugar units, starch saccharides obtained by enzymatic decomposition of starch or the like, and reduced starch saccharides obtained by reducing the end groups of the starch saccharides can be used. In addition, as starch is decomposed, saccharides with various degrees of polymerization are generated. Therefore, it is technically difficult and costly to completely isolate only saccharides with 8 or more sugar units. Thus, in a sugar mixture containing saccharides with 7 or less sugar units, by containing 30% by mass or more of the saccharides with 8 or more sugar units, the above performance can be sufficiently obtained in the ink, and dry resistance performance can be imparted without causing dripping.

[0016] The sugar mixture (sugar A) is blended in the range of 0.5 to 5.0% by mass, preferably 1.0 to 4.0% by mass, based on the total amount of the ink composition. If it is less than 0.5% by mass, it is difficult to obtain the effect of dry resistance. If it is more than 5.0% by mass, the viscosity of the ink increases, and it will impose restrictions on the structure of the writing instrument containing the ink.

[0017] Sugars with 3 or less sugar units (sugar B) are added to increase the specific gravity of the whole ink in order to maintain the dispersion state of the microcapsule pigment in the ink. Different from the conventionally general specific gravity adjusters that affect the physical properties of the ink such as pH, since they are the same saccharides as the above sugar mixture, they do not affect the physical properties of the sugar mixture (sugar A) composed of starch saccharides with 8 or more sugar units and their reduced products. Therefore, it is an excellent material that can maintain high ink stability without causing aggregation or sedimentation of the pigment, especially when using the above sugar mixture. Also, since it is difficult for the viscosity of the ink to change due to the addition, the dispersion stability of the microcapsule pigment can be maintained while maintaining a low viscosity state.

[0018] Examples of sugars with three or fewer sugars include trehalose, raffinose, maltitol, glucose, xylose, sucrose, maltose, etc., and trehalose, palatinose, and fructose are particularly preferred.

[0019] The sugar (sugar B) with three or fewer sugars is used in the range of 3.0 to 10.0% by mass, preferably 4.0 to 7.0% by mass, in the total amount of the ink composition. If the addition amount is less than 3.0% by mass, it is difficult to exhibit the desired performance, and even if it is blended in an amount exceeding 10% by mass, no further effect can be obtained, so no further addition is required.

[0020] By setting the mass ratio of the sugar A and the sugar B in the ink to be in the range of B / A ≧ 2, the aqueous ink can maintain the high drying-up performance of the sugar A and maintain the dispersion stability of the microcapsule pigment without increasing the viscosity, so that excellent handwriting can be formed over a long period of time. When B / A is less than 2, sufficient dispersion stability is difficult to be exhibited. The upper limit is not particularly limited, but it is preferably adjusted within the range of the addition amount of the aforementioned sugar B.

[0021] The water used in the aqueous ink is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltration water, distilled water, and the like. The content rate of water with respect to the total mass of the ink composition is not particularly limited, but is preferably in the range of 35 to 95% by mass, more preferably 40 to 90% by mass.

[0022] In addition to the above essential components, optional components can be blended in the aqueous ink composition of the present invention as long as the effects of the present invention are not impaired. For example, conventional water-soluble organic solvents that are compatible with water can be used. Specifically, examples include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, hexylene glycol, 1,3-butanediol, neoprene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 2-pyrrolidone, and N-methyl-2-pyrrolidone. Furthermore, the aforementioned water-soluble organic solvent may be used individually or in combination of two or more types, and is used in an amount of 2 to 60% by mass, preferably 5 to 35% by mass, in the ink composition.

[0023] Furthermore, a water-soluble resin can be added to provide adhesion to the paper surface. Examples of water-soluble resins include alkyd resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, and dextrin. One or more water-soluble resins can be used in combination, and they are used in an amount of 1 to 20% by mass in the ink composition, provided that they do not impair drying resistance.

[0024] Furthermore, by adding hollow particles to the ink in combination with the aforementioned sugars A and B, it is possible to improve ink flow during writing and stabilize the amount of ink dispensed. This allows for the formation of better handwriting, which is presumed to be because the uniform dispersion of hollow particles in the ink allows them to penetrate between the microcapsule pigments, which are also uniformly dispersed, effectively suppressing the adsorption of the microcapsule pigments. In general, this is particularly useful for small-diameter ballpoints (e.g., 0.3 mm or less) where ink dispensing is particularly unfavorable, as even fine particles can easily cause pigment aggregation and sedimentation, making it easier to observe differences in handwriting quality with and without the use of hollow particles. Furthermore, when the particle size of the hollow particles is in the range of 0.1 to 1 times (i.e., 1 / 10 to 1 time) relative to the particle size of the microcapsule pigment, a state can be formed in which many small-diameter hollow particles exist between the microcapsule pigments, resulting in a higher effect and greater usefulness.

[0025] The aforementioned hollow particles are organic particles such as resin particles or inorganic particles such as silica that have a hollow portion, and their material and shape are not particularly limited as long as they do not impair the aforementioned effects. Furthermore, they may be single-hollow particles having one hollow portion per particle, or multi-hollow particles having multiple hollow portions per particle.

[0026] Examples of hollow particles that can be used include inorganic hollow particles such as glass and silica particles, and hollow resin particles made of polymer compounds such as styrene resins such as cross-linked styrene-acrylic resin, acrylic resins such as acrylonitrile-acrylic resin, methacrylic resins, phenolic resins, fluorine resins, polyamide resins, polyimide resins, polycarbonate resins, and polyether resins. In terms of shape, spherical, elliptical, and needle-shaped particles are acceptable, and preferably, hollow resin particles are preferred in terms of material and spherical in shape. Solid particles (dense particles) that do not have a hollow portion have poor dispersion stability, making it difficult to obtain a continuous effect, and therefore, this invention is applicable only to hollow particles.

[0027] For hollow particles, an average particle size of 0.01 to 4.0 μm, preferably 0.05 to 2.5 μm, and more preferably 0.1 to 2.0 μm is practical. Specific commercially available products include Lowpake OP-62 (average particle size 450 nm), Lowpake OP-91, Lowpake HP-1055 (average particle size 1000 nm), Lowpake HP-91 (average particle size 1000 nm), Lowpake ULTRA (average particle size 380 nm), Lowpake ULTRA E (average particle size 380 nm), and Lowpake ULTRA Examples include DUAL (average particle size 380nm) (manufactured by DOW Corporation), SX-863(A), SX-864(B), SX-866(A), SX-866(B) (average particle size 300nm), SX-868 (average particle size 500nm) (manufactured by JSR Corporation), Banstar SP760 (average particle size 530nm), Banstar SP700 (average particle size 900nm) (manufactured by Chubu Saiden Co., Ltd.), Nipol MH5055 (average particle size 500nm), Nipol MH8101 (average particle size 1μm) (manufactured by Nippon Zeon Co., Ltd.), etc., and one or more types can be used in combination. Furthermore, the same method as described above for measuring microcapsule pigments can be applied to measure the average particle size.

[0028] The hollow particles are used in the aqueous ink composition in an amount of 0.1 to 10% by mass, preferably 0.1 to 5% by mass. If the content is less than 0.1% by mass, the desired effect is difficult to obtain, while the desired effect can be obtained even if the content does not exceed 10% by mass; therefore, no further addition is necessary.

[0029] In addition, if necessary, pH adjusters such as organic basic compounds, rust inhibitors such as benzotriazole, toltriazole, and saponins, preservatives or fungicides such as carbolic acid, sodium salt of 1,2-benzthiazolin 3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, wetting agents such as urea, sorbitol, mannitol, sucrose, glucose, and sodium pyrophosphate, defoamers, and fluorinated or nonionic surfactants to improve ink penetration may be used. Furthermore, lubricants can be added, and examples include metal soaps, polyalkylene glycol fatty acid esters, ethylene oxide-additive cationic surfactants, phosphate ester surfactants, N-acyl amino acid surfactants, dicarboxylic acid-type surfactants, β-alanine-type surfactants, 2,5-dimercapto-1,3,4-thiadiazole and its salts or oligomers, 3-amino-5-mercapto-1,2,4-triazole, thiocarbamate, dimethyldithiocarbamate, α-lipoic acid, condensates of N-acyl-L-glutamic acid and L-lysine and their salts. Furthermore, shear-reducing agents such as xanthan gum, gellan gum, succinoglycan, and guar gum can also be added. Furthermore, the functionality of the retractable ballpoint pen form can be enhanced by adding thickening inhibitors such as N-vinyl-2-pyrrolidone oligomer, N-vinyl-2-piperidone oligomer, N-vinyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, ε-caprolactam, and N-vinyl-ε-caprolactam oligomer.

[0030] The ink composition having the above configuration maintains the dispersion state of microcapsule pigments in the ink regardless of the ink viscosity, and is therefore adjusted to an ink viscosity that can be dispensed during normal writing. However, it is preferable to set the viscosity at 20°C in the range of 1 to 30 mPa·s. By achieving a low viscosity of 1-30 mPa·s, it becomes possible to house the ink in various writing instruments with structures other than ballpoint pens, which conventionally used a pipe-shaped ink reservoir when using microcapsule pigments. As a result, good thermochromic writing can be formed in marking pens, as well as in ballpoint pens with cotton wicks or direct-ink systems. The viscosity was measured using a rheometer (TA Instruments, product name: Discovery HR-2, cone plate (diameter 40 mm, angle 1°)) with the ink placed at 20°C and a shear rate of 7.68 sec. -1 These are values ​​measured under the following conditions.

[0031] The thermochromic ink composition of the present invention is filled into marking pens and ballpoint pens equipped with a fiber tip, felt tip, plastic tip, or ballpoint pen tip at the writing end. The marking pens and ballpoint pens may be of the cap type, which has a cap that covers the pen tip, or they may be of the retractable type, which has a retractable mechanism such as a push-button type, twist-button type, or slide-button type, and the pen tip can be stored inside the barrel.

[0032] When filling a marking pen, the structure and shape of the marking pen itself are not particularly limited. For example, a marking pen tip (bullet-shaped, chisel-shaped, brush-pen-shaped, etc.) such as a fiber tip, felt tip, or plastic tip, or a fountain pen-type metal tip, can be attached to the writing tip, and ink can be impregnated into an ink-absorbing body made of fiber bundles housed inside the barrel, supplying ink to the writing tip. Another example is a marking pen in which ink is directly housed inside the barrel, and a predetermined amount of ink is supplied to the writing tip via a comb-shaped ink flow rate adjustment member or an ink flow rate adjustment member made of fiber bundles. Yet another example is a marking pen in which ink is directly housed inside the barrel, and a predetermined amount of ink is supplied to the writing tip via a valve mechanism. In addition to a cap type, a retractable type can be created by providing an airtight opening and closing lid on the pen tip retraction hole, or by using an ink component with a highly moist composition. In addition to having a single pen tip, a double-ended design may also be available, with pen tips of different thicknesses and shapes at both ends of the barrel. Furthermore, in the aforementioned double-ended design, one end may be a ballpoint pen.

[0033] When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited. Examples include a structure in which ink is impregnated into an ink-absorbing material made of fiber bundles housed inside the barrel and supplied to the writing tip; a structure in which ink is directly housed inside the barrel and an ink flow rate adjustment member with comb-shaped grooves or an ink flow rate adjustment member made of fiber bundles is interposed; and a ballpoint pen having an ink-retaining tube filled with an ink composition inside the barrel, the ink-retaining tube communicating with a tip to which a ball is attached, and a liquid stopper to prevent backflow closely attached to the end face of the ink. A solid stopper can also be used in combination with the liquid stopper.

[0034] The aforementioned ballpoint pen tip can be a tip in which a ball is held in a ball-holding portion formed by pressing the tip of a straight metal pipe, or a metal pipe with a stepped shape that narrows the inner diameter of the front part that serves as the writing section, inward from the outer surface, or a tip in which a ball is held in a ball-holding portion formed by cutting a metal material with a drill or the like, or a tip in which the ball held in such a metal pipe or tip formed by cutting a metal material is biased forward by a spring. Furthermore, the balls used are those made of cemented carbide, stainless steel, ruby, ceramic, etc., with an outer diameter of 0.1 to 2.0 mm, preferably 0.2 to 1.2 mm, and more preferably 0.28 to 1.0 mm.

[0035] The barrel containing the thermochromic ink is preferably made of a thermoplastic resin such as polyethylene, polypropylene, or polyethylene terephthalate, in terms of low ink evaporation and productivity. The tip can be directly connected to the barrel, or it can be connected to the barrel and tip via a connecting member. Furthermore, it can be configured as a replaceable cartridge type. When the ink composition is low viscosity, the ink composition can be contained within the barrel by either attaching an ink retaining member to the front of the barrel and directly containing the ink composition within the barrel, or by impregnating a porous body or a fibrous material with the ink composition and then containing it.

[0036] Furthermore, by using a transparent, colored transparent, or translucent molded body for the barrel, the ink color and ink level can be checked. In the form of a ballpoint pen, the barrel may be in the form of a ballpoint pen refill, with the refill housed inside the outer barrel, or the barrel itself, with a tip attached to the end, may be used as the ink reservoir, with ink directly filled into the barrel.

[0037] Furthermore, the ballpoint pen using the aforementioned barrel can be either a capped or retractable type. As for retractable ballpoint pens, any structure in which the writing tip provided on the ballpoint pen refill is housed inside the outer barrel while exposed to the outside air, and the writing tip protrudes from the opening of the outer barrel when the retractable mechanism is activated, can be used. Examples of operating methods for the retraction mechanism include knocking, rotating, and sliding mechanisms. A retractable pen may have a retractable mechanism at the rear end or side of the outer barrel, and pressing the retractable mechanism causes the writing tip of the ballpoint pen refill to extend and retract from the opening at the front end of the outer barrel. Alternatively, pressing a clip on the outer barrel can cause the writing tip of the ballpoint pen refill to extend and retract from the opening at the front end of the outer barrel. A rotary type can be exemplified by having a rotating part (such as a rear shaft) on the outer shaft, and by rotating this part, the writing tip of the ballpoint pen refill extends and retracts from the opening at the front end of the outer shaft. A sliding type may be exemplified by having a sliding part on the side of the barrel, which allows the writing tip of the ballpoint pen refill to extend and retract from the opening at the front of the outer barrel by operating the slide, or by sliding a clip part provided on the outer barrel, which allows the writing tip of the ballpoint pen refill to extend and retract from the opening at the front of the outer barrel. Furthermore, a retractable ballpoint pen may be a composite type that houses multiple ballpoint pen refills in addition to one that houses a single ballpoint pen refill within the outer barrel. Also, the ink reservoir that makes up the ballpoint pen refill may be made of resin or metal.

[0038] An ink backflow prevention device can also be filled into the trailing end of the ink contained in the ballpoint pen refill. The ink backflow prevention body can be either liquid or solid. Examples of liquid ink backflow prevention bodies include non-volatile media such as polybutene and silicone oil. If desired, silica, aluminum silicate, etc., can be added to the media. Furthermore, resin molded products can be used as solid ink backflow prevention bodies. Furthermore, the liquid and solid ink backflow prevention devices can be used in combination.

[0039] Furthermore, along with the writing instrument, a friction member can be used to erase or change the color of the writing by generating frictional heat. As the friction member, an elastic body containing an elastomer that is highly elastic and can generate appropriate friction and frictional heat during friction is preferred. Although it is also possible to rub the ink marks with an eraser, eraser residue is generated during friction, so the aforementioned friction member is preferred. The material used for the friction member may be a resin containing silicone resin or styrene copolymer, or a polyester resin. The friction member can be combined with a separate, arbitrarily shaped component (friction body) from the writing instrument to create a writing instrument set, but by fixing the friction member to the outer casing of the writing instrument, a form with superior portability can be achieved. In the case of capped writing instruments, there are no particular limitations on where the friction element can be provided. For example, the cap itself may be formed from the friction element, the barrel itself from the friction element, the clip itself may be formed from the friction element if a clip is provided, or the friction element may be provided at the tip (top) of the cap or the rear end of the barrel (the part opposite the cap side where the writing tip is not provided). In the case of retractable writing instruments, the location where the friction element is provided is not particularly limited, but for example, the barrel itself may be formed from the friction element, or if a clip is provided, the clip itself may be formed from the friction element, or the friction element may be provided near the barrel opening (pen tip side), at the rear end of the barrel (the part without the writing tip), or at the knock mechanism. [Examples]

[0040] Examples are described below, but the present invention is not limited to these examples. Tables 1-3 show the compositions of the thermochromic aqueous inks used in the examples and comparative examples. The composition values ​​in the tables represent parts by mass. The viscosity of each ink was measured using a rheometer (TA Instruments, product name: Discovery HR-2, cone plate (diameter 40 mm, angle 1°)) at 20°C with a shear rate of 7.68 sec. -1 It was measured using [this method]. Furthermore, the average particle diameter was measured using the Coulter method with a particle size distribution analyzer (Beckman Coulter, Ltd., product name: Multisizer 4e) as the average particle diameter of particles equivalent to an equivolute sphere.

[0041] [Table 1]

[0042] [Table 2]

[0043] [Table 3]

[0044] The contents of the raw materials listed in the table are explained according to the footnote numbers. (1) A microcapsule pigment containing a reversible thermochromic composition consisting of (a) 4.5 parts of 2-(2-chloroanilino)-6-di-n-butylaminofluorane as component (b) 4.5 parts of 1,1-bis(4′-hydroxyphenyl)n-decane and 7.5 parts of 2,2-bis(4′-hydroxyphenyl)hexafluoropropane as component (c) 50.0 parts of 4-benzyloxyphenylethyl caprate (color development temperature: -20℃, decolorization temperature: 57℃, ΔH: 63℃, average particle size: 1.0 μm, changes color from black to colorless) (2) A microcapsule pigment containing a reversible thermochromic composition consisting of (a) 2.0 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide as component (a), 8.0 parts of 2,2-bis(4′-hydroxyphenyl)hexafluoropropane as component (b), and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c), which changes color from blue to colorless). (3) A microcapsule pigment containing a reversible thermochromic composition consisting of (a) 2.0 parts of 4-[2,6-bis(2-ethoxyphenyl)-4-pyridinyl]-N,N-dimethylbenzeneamine, (b) 6.0 parts of 2,2-bis(4′-hydroxyphenyl)-hexafluoropropane, and (c) 5.0 parts of 4-benzyloxyphenylethyl caprate (color development temperature: -20°C, decolorization temperature: 61°C, ΔH: 66°C, average particle size: 2.3 μm, changes color from yellow to colorless). (4) A sugar mixture containing 94% of starch syrups of 8 or more sugars, manufactured by Sanwa Starch Industry Co., Ltd., product name: Sandec 30 (5) Sugar mixture containing 83% of starch saccharified with 8 or more sugars, manufactured by Sanwa Starch Industry Co., Ltd., product name: Sandec 70FN (6) Sugar mixture containing 56% of starch saccharified sugars of 8 or more sugars, manufactured by Sanwa Starch Industry Co., Ltd., product name: Sandec 150 (7) Fructose (monosaccharide) (8) Trehalose (disaccharide) (9) Palatinose (2 sugar) (10) Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Prysurf AL (11) Manufactured by Arcsarda Japan, Product name: Proxel XL-2 (12) DOW Corporation, Product name: Lowpayk ULTRA (Aqueous dispersion with average particle size of 380 nm and 30% solids content) (13) Manufactured by Chubu Saiden Co., Ltd., product name: Banstar SP700 (aqueous dispersion with average particle size of 900 nm and solid content of 28%) (14) Manufactured by Chubu Saiden Co., Ltd., product name: Banstar SP760 (aqueous dispersion with average particle size of 530 nm and solid content of 42%) (15) Manufactured by Nippon Shokubai Co., Ltd., Product name: Epostor MX200W (Aqueous dispersion with average particle size of 350 nm and 10% solid content)

[0045] Preparation of marking pen ink (ballpoint pen ink A) The raw materials were mixed in the proportions specified in Examples 1-6 and 9-15 and Comparative Examples 1-4 and 6-8, stirred at 2000 rpm for 1 hour in a disperser at 20°C, and then filtered to obtain a marking pen ink composition (ballpoint pen ink A).

[0046] Making a marking pen The marking pen ink composition is impregnated into an ink-absorbing body made of polyester sliver coated with a synthetic resin film, housed in a barrel made of polypropylene resin, and assembled to connect a processed tip (bullet-shaped plastic pen) with numerous ink guide holes formed in polyester resin to the tip of the barrel via a holder, and a cap is attached to obtain a marking pen. A friction member made of an elastic material containing styrene elastomer is provided on the top of the cap.

[0047] Making ballpoint pen A A ballpoint pen A is manufactured by filling the pen-type writing instrument exterior, which has a stainless steel tip holding a 0.7 mm diameter cemented carbide ball (comb-shaped ink reservoir), with the ink reservoir at the rear (sealed side) by fitting a pen core (comb-shaped ink reservoir) to the front (open side) of the barrel, and then fitting a cap onto it.

[0048] Preparation of ballpoint pen ink B The raw materials, excluding succinoglycan, were mixed in the proportions specified in Examples 7 and 8 and Comparative Examples 5 and 8. The mixture was stirred at 2000 rpm for 1 hour at 20°C using a disper, then a thickener was added and the mixture was stirred for another hour. The mixture was then filtered to obtain a ballpoint pen ink composition.

[0049] Preparation of an ink backflow prevention device An ink backflow prevention body was obtained by adding 1.5 parts of fatty acid amide as a thickening agent to 98.5 parts of polybutene as a base oil, and then kneading the mixture using a three-roll machine.

[0050] Making Ballpoint Pen B Ballpoint pen B was manufactured by filling a ballpoint pen refill, in which a stainless steel tip (containing a spring that presses the ball toward the writing section) holding a 0.4 mm diameter cemented carbide ball was fitted to one end of a transparent polypropylene pipe, with each of the aforementioned ink compositions, and then placing the ink backflow prevention body at the rear end of the refill. Finally, the ballpoint pen refill was assembled into the barrel and the cap was attached. A friction member made of an elastic material containing styrene elastomer is provided at the rear end of the barrel.

[0051] The following tests were conducted using each of the obtained ink compositions and writing instruments (marking pen and ballpoint pens A and B). Dry-up test Each writing instrument, confirmed to be writable, was left horizontally at 20°C for 7 days with its tip exposed to air. Then, at room temperature, 12 spiral circles were handwritten on JIS P3201 writing paper A in three consecutive lines. The condition of the handwriting was visually inspected. Ink stability test Each ink was sealed in a container and left in a 50°C incubator for 30 days. After cooling to room temperature, the condition of the ink was visually inspected. Written Examination (1) After confirming that each writing instrument was capable of writing, it was left in a 50°C environment for 30 days, then allowed to cool to room temperature. Twelve spiral circles were then continuously written by hand on JIS P3201 writing paper A.

[0052] Making Ballpoint Pen C A ballpoint pen C was manufactured by filling a ballpoint pen refill, in which a stepped stainless steel tip (housing a spring that presses the ball toward the writing section) holding a 0.3 mm diameter cemented carbide ball was fitted to one end of a transparent polypropylene pipe, filling the refill with ballpoint pen ink, placing an ink backflow prevention body at the rear end, assembling the ballpoint pen refill into the barrel, and attaching the cap. A friction member made of an elastic material containing styrene elastomer is provided at the rear end of the barrel.

[0053] Written Examination (2) Ten ballpoint pens (C) that had been confirmed to be writable were left in a 50°C environment for 30 days, then allowed to cool to room temperature. Using an automatic writing test machine, spiral circles were continuously written on JIS P3201 writing paper A, and the condition of the writing was observed visually. The test machine was used under the conditions of a writing load of 50g, a writing angle of 70°, and a writing speed of 4m / min. The results of each test are shown below.

[0054] [Table 4]

[0055] [Table 5]

[0056] [Table 6]

[0057] The evaluation of the test results is as follows: Dry-up test ○: No smudging occurred, or the writing recovered within one line or less. ×: The writing does not recover within 3 lines or is impossible to write on. Ink stability test ○: No change from before the exam. ×: Separation and precipitation of layers, and aggregation of microcapsule pigments were observed. Written examination (1) (A and B are considered passing grades) A: Shows good, dark handwriting. B: Some areas of the handwriting showed slight blurring or skipping of lines. C: The handwriting is faint, the lines are broken, or it is impossible to write. Written examination (2) (A and B are considered passing grades) A: All 10 pens have stable ink flow and produce dark, clear lines until the very end of writing. B: While the pens could be completed, there were four or fewer pens where the ink flow was unstable, resulting in areas where the ink density decreased midway through the writing. C: There are five or more pens with unstable ink ejection in multiple locations, or the pens are completely unusable for writing.

Claims

1. It consists of a microcapsule pigment containing a thermochromic composition, water, sugar A which is a sugar mixture containing 30% by mass or more of starch saccharified products and / or reduced products thereof of 8 or more sugars, and sugar B which contains 3 or fewer sugars. A thermochromic ink composition for writing instruments in which the mass ratio of sugar A and sugar B blended in the ink is in the range of B / A ≥ 2.

2. The thermochromic ink composition for writing instruments according to claim 1, wherein the aforementioned sugar A is contained in the ink composition in an amount of 0.5 to 5.0% by mass.

3. The thermochromic ink composition for writing instruments according to claim 1, wherein the sugar B is one or more selected from trehalose, palatinose, and fructose.

4. The thermochromic ink composition for writing instruments according to claim 1, wherein the microcapsule pigment is added in an amount of 10 to 35% by mass of the total amount of the ink composition.

5. A thermochromic ink composition for writing instruments according to claim 1, comprising hollow particles.

6. The thermochromic ink composition for writing instruments according to claim 5, wherein the particle diameter of the hollow particles is in the range of 0.1 to 1 times the particle diameter of the microcapsule pigment.

7. The thermochromic ink composition for writing instruments according to claim 1, wherein the viscosity at 20°C is in the range of 1 to 30 mPa·s.

8. A writing instrument containing the thermochromic ink composition for writing instruments according to any one of claims 1 to 7.

9. The writing instrument according to claim 8, further comprising a friction member that changes the color of the writing made by the aforementioned writing instrument due to frictional heat.

Images