Solid cursive writing instruments and writing instruments using them

Abstract

To provide a solid writing implement which has excellent strength and discoloration characteristics and is applicable for a mechanical pencil.SOLUTION: A solid writing implement contains a microcapsule pigment including a functional material such as a reversible thermochromic composition, a shaping material such as a wax, a polyvinyl alcohol resin and a polyamide resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solid writing body that can form handwriting that changes color according to temperature changes. More specifically, it relates to a solid writing body that is excellent in strength and color development properties and has suppressed abnormal color changes.

Background Art

[0002] Conventionally, solid writing bodies such as colored pencils using wax or the like as a shaping material have been known. In order to improve the strength, moldability, and writing properties of these solid writing bodies, it is known to blend inorganic fillers such as talc to improve their performance.

[0003] Also, conventionally, a solid writing body using a reversible thermochromic composition that can mutually store and retain the states before and after color change in a certain temperature range such as room temperature has been proposed (for example, Patent Document 1). The solid writing body described therein forms handwriting that changes color due to temperature changes by using a reversible thermochromic composition alone or its microcapsule encapsulation as a colorant added to wax, which is a shaping material. In particular, when using a microcapsule pigment encapsulating a heating-decoloring type reversible thermochromic composition, the handwriting can be easily erased by frictional heat, resulting in a highly convenient writing body that allows for corrections such as miswriting. For example, it can be used for writing in notebooks or diaries, or for drawing.

[0004] However, in such solid writing bodies, the materials used are limited, so they tend to be inferior in strength compared to conventional general solid writing bodies. Therefore, the application of various materials has been studied to improve the strength (for example, Patent Document 2).

[0005] On the other hand, when attempting to achieve sufficient strength for use as a thin-diameter lead, such as for mechanical pencil leads, there were cases where discoloration abnormalities occurred, resulting in the discoloration properties obtained by microcapsules containing a reversible thermochromic composition not being fully exhibited. Therefore, there was a need to develop a solid writing material that further improved strength and discoloration properties without compromising writing performance or color development as a solid writing material. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-166310 [Patent Document 2] Japanese Patent Publication No. 2020-105314 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the inventors' research, it has been found that when using a hard material to achieve high strength in a solid writing instrument containing microcapsules, discoloration abnormalities can easily occur. Specifically, when the writing formed by the solid writing instrument is discolored by heat, it sometimes returns to its original color over time. Although the reason has not been fully elucidated, it is presumed that the use of a hard material causes the microcapsules to break down within the core. Therefore, it has been difficult to achieve both strength and discoloration characteristics in the solid writing instrument. The present invention solves these problems and provides a solid writing instrument that is strong and has suppressed discoloration abnormalities. [Means for solving the problem]

[0008] The solid writing material according to the present invention is Microcapsule pigments containing functional materials, excipient material, Polyvinyl alcohol resin, and Polyamide resin It is characterized by containing [a certain element].

[0009] Furthermore, the mechanical pencil according to the present invention is configured such that the solid writing element is held via a chuck and extended as needed. [Effects of the Invention]

[0010] The solid writing material according to the present invention achieves high strength that makes it resistant to breakage even when made thin, while maintaining the high level of writing performance required for solid writing materials, and excellent discoloration characteristics that suppress discoloration abnormalities. [Brief explanation of the drawing]

[0011] [Figure 1] This graph shows the hysteresis characteristics in the color density-temperature curve of a heat-decolorizing, reversible thermochromic composition that can be used in the present invention. [Modes for carrying out the invention]

[0012] [Solid cursive] The solid writing material according to the present invention comprises microcapsule pigment, excipient, polyvinyl alcohol resin, and polyamide resin.

[0013] The solid writing material according to the present invention uses microcapsules containing functional materials as pigments. Preferred functional materials include: (i) A component consisting of an electron-donating colorimetric organic compound, (b) A component consisting of an electron-accepting compound, (c) A reaction medium that causes the electron transfer reaction by the components of (a) and (b) to occur reversibly in a specific temperature range, This is a reversible thermochromic composition comprising [a specific substance].

[0014] The reversible thermochromic microcapsule pigment that can be used in the present invention will be described below. As the reversible thermochromic microcapsule pigment, it can be arbitrarily selected and used from conventionally known ones. For example, it changes color before and after a predetermined temperature (color change point), exhibits a decolorized state in a temperature range above the high-temperature side color change point, and a colored state in a temperature range below the low-temperature side color change point. Among the above two states, only a specific one of the states exists in the normal temperature range, and the other state is maintained while the heat or cooling required for the manifestation of the state is applied. However, when the application of the heat or cooling is stopped, it returns to the state presented in the normal temperature range. A reversible thermochromic microcapsule pigment encapsulating a heat-decoloring type (decoloring by heating and coloring by cooling) reversible thermochromic composition having a relatively small hysteresis width ΔH (ΔH = 1 to 7 °C) can be applied.

[0015] In addition, a reversible thermochromic microcapsule pigment encapsulating a heat-decoloring type (decoloring by heating and coloring by cooling) reversible thermochromic composition showing a larger hysteresis characteristic (ΔH = 8 to 50 °C) than the above, that is, the shape of the curve plotting the change in coloring density due to temperature change is significantly different when the temperature is increased from the low-temperature side of the color change temperature range and when the temperature is decreased from the high-temperature side of the color change temperature range. The colored state in the low-temperature range below the complete coloring temperature (T1) or the decolorized state in the high-temperature range above the complete decoloring temperature (T4) has color memory in a specific temperature range [temperature range between T2 and T3 (substantially two-phase holding temperature range)] can also be applied.

[0016] The hysteresis characteristic in the color density-temperature curve of the microcapsule pigment encapsulating the reversible thermochromic composition will be described below with reference to the graph of FIG. 1.

[0017] In Fig. 1, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to temperature change proceeds along the arrow. Here, A is a point indicating the density at the temperature T4 (hereinafter referred to as the complete decolorization temperature) at which the state of complete decolorization is reached, B is a point indicating the density at the temperature T3 (hereinafter referred to as the decolorization start temperature) at which decolorization begins, C is a point indicating the density at the temperature T2 (hereinafter referred to as the color development start temperature) at which color development begins, and D is a point indicating the density at the temperature T1 (hereinafter referred to as the complete color development temperature) at which the state of complete color development is reached.

[0018] Also, the length of the line segment EF, that is, the difference between the highest density and the lowest density, is a measure indicating the contrast of color change. Also, the length of the line segment HG, that is, the intermediate temperature between T1 and T2 is T H , G , , G , and the intermediate temperature between T3 and T4 is T G When regarded as H and T G The difference between them is the temperature width △H indicating the degree of hysteresis. The larger this △H value is, the easier it is to maintain each state before and after color change.

[0019] Furthermore, in the case of a reversible thermochromic composition, only a specific one of the states (color development state) exists in the normal temperature range among the color development and decolorization states, and in order to easily change the color (decolorize) the impression formed by the reversible thermochromic composition by the frictional heat generated by friction, it is preferable that the complete decolorization temperature (T4) is 50 to 95 °C, and it is preferable that the color development start temperature (T2) is -50 to 10 °C.

[0020] Furthermore, when erasing handwriting by frictional heat, if the complete decolorization temperature (T4) is 95 °C or lower, the handwriting formed on the writing surface can be sufficiently discolored by the frictional heat generated by several frictions with a friction member.

[0021] In the aforementioned temperature setting for the complete decolorization temperature (T4), a higher temperature is preferable for the color development state to be maintained under normal use conditions, and a lower temperature is preferable for the frictional heat generated by friction to exceed the complete decolorization temperature (T4). Therefore, the complete decolorization temperature (T4) is preferably 50 to 90°C, more preferably 60 to 80°C. Furthermore, in the present invention, the hysteresis width (ΔH) is in the range of 50°C to 100°C, preferably 55 to 90°C, and even more preferably 60 to 80°C.

[0022] The reversible thermochromic microcapsule pigment used in the solid writing instrument according to the present invention may also be a reversible thermochromic composition having a complete decolorization temperature (T4) on the higher side than the aforementioned discoloration temperature range.

[0023] By using the aforementioned reversible thermochromic composition, the handwriting will not fade even when left in high-temperature environments such as inside a car during the summer, thus expanding the range of applications for solid cursive writing. Furthermore, because it becomes difficult to erase through rubbing with a friction material, it can be used to determine the authenticity of documents.

[0024] The components (a), (b), and (c) that constitute the reversible thermochromic composition are described below.

[0025] In the present invention, component (a) is an electron-donating chromogenic organic compound that produces color by donating electrons to component (b), which is a color developer, causing the cyclic structure of component (a), such as a lactone ring, to open and form a resonance structure with component (b). Examples of such electron-donating chromogenic organic compounds include diphenylmethane phthalides, phenyl indolyl phthalides, indolyl phthalides, diphenylmethane azaphthalides, phenyl indolyl azaphthalides, fluoranes, styrinoquinolines, diazalodamine lactones, pyridines, quinazolines, and bisquinazolines.

[0026] Component (b) can be an electron-accepting compound, and may include compounds with active protons, pseudoacidic compounds (compounds that are not acids but act as acids in the composition to cause component (a) to develop color), and compounds with electron vacancies.

[0027] Examples of compounds having active protons include compounds having a phenolic hydroxyl group, ranging from monophenols to polyphenols, and further, those having substituents such as alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxyl groups and their esters or amide groups, halogen groups, etc., as well as bis-type and tris-type phenols, phenol-aldehyde condensation resins, etc. Alternatively, metal salts of the compounds having the phenolic hydroxyl group may also be used.

[0028] Examples of component (c) of the reaction medium that causes the electron transfer reaction between components (a) and (b) to occur reversibly in a specific temperature range include alcohols, esters, ketones, and ethers.

[0029] Preferably, as component (c) above, a carboxylic acid ester compound exhibiting a ΔT value (melting point-cloud point) of 5°C to less than 50°C is used, which can form a reversible thermochromic composition exhibiting color memory properties, characterized by a large hysteresis characteristic (the curve plotting the change in color intensity due to temperature changes differs depending on whether the temperature is changed from low to high or from high to low) with respect to the color intensity-temperature curve.

[0030] Various compounds have been proposed for this purpose, and they can be arbitrarily selected and used.

[0031] The proportions of the constituent components of (a), (b), and (c) above depend on the concentration, discoloration temperature, discoloration pattern, and the type of each component. Generally, the component ratios that yield the desired discoloration characteristics are in the range of 1 part (a) to 0.1 to 50 parts (b), preferably 0.5 to 20 parts, and 1 to 800 parts (c), preferably 5 to 200 parts (all proportions are based on mass). In addition, each component may be used in mixtures of two or more types.

[0032] The aforementioned reversible thermochromic composition is encapsulated in microcapsules and used as a reversible thermochromic microcapsule pigment. This is because the reversible thermochromic composition maintains the same composition and can exert the same effects under various usage conditions.

[0033] Methods for microencapsulating the aforementioned reversible thermochromic composition include 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, and spray drying, which can be appropriately selected depending on the application. Furthermore, depending on the purpose, a secondary resin coating can be applied to the surface of the microcapsules to provide durability, or the surface properties can be modified to make them practical.

[0034] Here, the mass ratio of the reversible thermochromic composition to the microcapsule wall film is preferably in the range of 7:1 to 1:1, more preferably 6:1 to 1:1.

[0035] If the ratio of the reversible thermochromic composition to the wall film exceeds the aforementioned range, the wall film becomes too thin, which can easily lead to a decrease in resistance to pressure and heat. Furthermore, if the ratio of the wall film to the reversible thermochromic composition exceeds the aforementioned range, it can easily lead to a decrease in color density and vividness during color development.

[0036] In addition to the reversible thermochromic compositions mentioned above, functional materials include liquid crystals such as cholesteric liquid crystals and nematic liquid crystals, and photochromic materials. Examples of such liquid crystals include Helicone HC SLM90020, 90120, 90220, and 90320 (all manufactured by Wacker Chemie).

[0037] The solid writing material according to the present invention further comprises an excipient. In the present invention, any excipient that can be used in solid writing materials can be used. Specifically, the excipient is preferably one with a weight-average molecular weight Mw of 1,000 to 100,000, and examples include wax, gelling agent, and clay. Of these, wax, particularly polyolefin wax, is preferably used because it maintains the strength of the writing material to prevent easy breakage during writing, while also providing good abrasion resistance during writing, resulting in a smooth writing feel and the formation of dark, clear lines.

[0038] Examples of the polyolefin wax include polyethylene, polypropylene, polybutylene, α-olefin polymers, ethylene-propylene copolymers, ethylene-butene copolymers, and the like. The polyolefin wax may also be modified with styrene or maleic anhydride, etc.

[0039] While the molecular weight of the polyolefin wax is not particularly limited, a polyolefin wax with a weight-average molecular weight (Mw) of 1,000 to 30,000, as determined by gel permeation chromatography (GPC method), is preferred as the excipient. If the weight-average molecular weight of the polyolefin wax exceeds 30,000, the solid writing material tends to wear down less easily during writing, and the writing tends to become unclear. If the molecular weight falls below 1,000, it is difficult to increase the strength of the writing material, and the writing material tends to break easily during writing. Furthermore, when erasing by rubbing, the writing material tends to spread on the paper surface (the wax becomes thinner), which can stain the blank areas of the writing surface or cause color transfer and staining to other papers.

[0040] " To enhance the strength of the cursive writing material, suppress breakage during writing, provide a smooth writing feel, and form a highly dense line, it is more preferable that the weight-average molecular weight of the polyolefin wax be in the range of 1,000 to 20,000.

[0041] Furthermore, among polyolefin waxes, those with a softening point in the range of 20°C to 120°C are preferred because they offer a good balance between cursive strength and abrasion resistance during writing. The softening point of polyolefin wax is measured according to JIS K2207-6 (2006) (ring-ball method).

[0042] Specific examples of polyolefin waxes that can be used in the present invention include the Neowax series (polyethylene manufactured by Yasuhara Chemical Co., Ltd.), the Sunwax series (polyethylene manufactured by Sanyo Chemical Industries, Ltd.), the Highwax series (polyolefin manufactured by Mitsui Chemicals, Inc.), AC polyethylene (polyethylene manufactured by Honeywell), the HS Crysta series (α-olefin manufactured by Toyokuni Oil Co., Ltd.), the El Crysta series (α-olefin manufactured by Idemitsu Kosan Co., Ltd.), and the Licocene PP series (manufactured by Clariant).

[0043] Of these polyolefin waxes, it is preferable to use side-chain crystalline polyolefins. Side-chain crystalline polyolefins are characterized by crystallization occurring mainly in the side chains rather than the polyolefin main chain, resulting in a low melting point and melting occurring within a narrow temperature range. Such side-chain crystalline polyolefins are characterized by having long alkyl groups in the side chains. Specifically, those having long-chain alkyl groups of C12 to C28 are preferred. Furthermore, the long-chain alkyl groups of the side chains are not particularly limited to linear or branched types, but linear types are more preferred from the viewpoint of crystallinity. Note that these alkyl groups in the side chains may have substituents, but this tends to reduce crystallinity. Therefore, in order to adjust the crystallinity, the side chains of the side-chain crystalline polyolefin can be modified with, for example, styrene. In addition, it is preferable that the long-chain alkyl groups have functional groups that form hydrogen bonds, as this causes hydrogen bonding and aggregation of alkyl groups, improving crystallinity.

[0044] Another example of a side-chain crystalline polyolefin is a polyolefin with a highly branched structure (hereinafter referred to as a highly branched polyolefin for simplicity). That is, a highly branched polyolefin has a structure that is slightly different from that of a single main chain to which side chains are bonded. However, because the main chain is less folded during crystallization, it has a low melting point and melting occurs within a narrow temperature range.

[0045] Furthermore, from the viewpoint of the mechanical strength, discoloration characteristics, and handling during manufacturing of the solid writing material, the weight-average molecular weight Mw of the side-chain crystalline polyolefin is preferably 2,000 to 50,000, and more preferably 10,000 to 30,000. In addition, the number-average molecular weight Mn of the side-chain crystalline polyolefin is preferably 1,000 to 10,000. Here, the weight-average molecular weight and number-average molecular weight were measured by gel permeation chromatography with polystyrene as the reference.

[0046] Furthermore, preferred side-chain crystalline polyolefins have a melting point (mp) of 20 to 80°C. More preferably, it is 25°C to 60°C, and even more preferably, 30°C to 55°C. If the melting point is lower than this range, the strength of the solid writing material tends to decrease, and if it is higher than this range, the color development tends to deteriorate. When the melting point is within this range, the solid writing material becomes flexible due to frictional heat during writing without compromising stability in practical environments, and the amount of transfer to the writing surface increases, thereby improving the density of the writing.

[0047] Examples of such side-chain crystalline polyolefins include HS Crysta 4100, HS Crysta 6100 (both trade names, manufactured by Toyokuni Oil Co., Ltd.), El Crysta 4100, and El Crysta 6100 (both trade names, manufactured by Idemitsu Kosan Co., Ltd.), while examples of highly branched polyolefins include VYBAR 103, VYBAR 260, VYBAR 343, and VYBAR 852 (all trade names, manufactured by Baker Hughes).

[0048] Polyolefin waxes may be used individually or in combination.

[0049] In addition, other waxes, gelling agents, clays, etc., can be used as excipients along with the polyolefin wax. Any conventionally known wax may be used as the other wax, specifically including carnauba wax, wood wax, beeswax, microcrystalline wax, montane wax, candelilla wax, sucrose fatty acid esters, dextrin fatty acid esters, and paraffin wax. Conventionally known gelling agents can be used, such as 12-hydroxystearic acid, dibenzylidene sorbitols, tripenzylidene sorbitols, amino acid oils, and alkali metal salts of higher fatty acids. Examples of clay minerals include kaolin, bentonite, and montmorillonite.

[0050] The excipient content is preferably 0.2 to 70% by mass, and more preferably 0.5 to 40% by mass, based on the total mass of the solid writing material. When the content is within the above range, it is easy to create a solid writing material that increases the strength of the writing material while maintaining good abrasion resistance during writing, resulting in a good writing feel and the formation of highly dense lines.

[0051] Furthermore, the solid writing material according to the present invention contains a polyvinyl alcohol resin. This polyvinyl alcohol resin is generally produced by saponifying polyvinyl acetate. Using a polyvinyl alcohol resin in the solid writing material tends to improve the moldability and strength of the writing material. The molecular weight of the polyvinyl alcohol resin is not particularly limited, but it is preferable that the weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC method) is 100 to 4000. In addition, a partially saponified polyvinyl alcohol with a relatively low degree of saponification is preferred. Specifically, it is preferable that the degree of saponification of the partially saponified polyvinyl alcohol be 80 mol% or less, and more preferably 3 to 50 mol%. Examples of such partially saponified polyvinyl alcohol include JMR-10LL (manufactured by Nippon Vitamin Vinegar & Poval Co., Ltd., degree of saponification 5-20 mol%), JMR-10L (manufactured by Nippon Vitamin Vinegar & Poval Co., Ltd., degree of saponification 30-40 mol%), JMR-20L (manufactured by Nippon Vitamin Vinegar & Poval Co., Ltd., degree of saponification 30-40 mol%), LM-10HD (manufactured by Kuraray Co., Ltd., degree of saponification 38-42 mol%), LM-20 (manufactured by Kuraray Co., Ltd., degree of saponification 33-38 mol%), and LM-25 (manufactured by Kuraray Co., Ltd., degree of saponification 33-38 mol%).

[0052] The polyvinyl alcohol resin content is preferably 5% to 30% by mass, more preferably 10% to 20% by mass, relative to the total mass of the solid writing material. In general solid writing materials, when polyvinyl alcohol resin is included, its content is less than 5% by mass. The solid writing material according to the present invention achieves superior properties by containing a relatively large amount of polyvinyl alcohol resin through interaction with other components.

[0053] The solid writing material according to the present invention comprises a polyamide resin. Polyamide resin is a polymer in which many repeating units are polymerized by amide bonds, and although there are various types depending on the chemical structure of the repeating units, they can be arbitrarily selected and used according to the purpose. Polyamide resins are classified into polymers of fatty acids and amines, and polymers of aromatic carboxylic acids and amines, but polymers of fatty acids and amines are preferably used. Furthermore, the crystallinity and melting point of the polyamide resin change depending on the type of fatty acid and amine and the degree of polymerization, but those with high crystallinity and a low melting point are preferred. Specifically, polyamide resins with a melting point of 150°C or lower are preferred. Considering both writing performance and the strength of the lead, a melting point of 50°C to 150°C is more preferable. The polyamide resin may also contain other repeating units derived from esters, etc., to the extent that it does not impair the effects of the present invention. Specifically, examples include the crystalline polymerized fatty acid polyamide resins PA-100 and PA-100A-S (both manufactured by T&K TOKA Corporation), and the amorphous polyether ester amide resins TPAE-12, TPAE-32, and PA-201 (all manufactured by T&K TOKA Corporation).

[0054] The polyamide resin content is preferably 1 to 10% by mass, and more preferably 2 to 7% by mass, relative to the total mass of the solid writing material. The inventors' research has shown that polyamide resin has the effect of improving discoloration abnormalities when incorporated into a relatively hard core material. However, if the amount incorporated is too small, the effect is insufficient, and if it is incorporated in excess, the effect becomes saturated.

[0055] The solid writing material according to the present invention is thought to achieve its excellent properties particularly through the interaction between the polyvinyl alcohol resin and the polyamide resin. For this reason, particularly excellent effects tend to be obtained when the relative mixing ratio is within a specific range. Specifically, it is preferable that the ratio of the polyamide resin content to the polyvinyl alcohol resin content is less than 1 / 1. Furthermore, it is more preferable that it is 1 / 2 to 1 / 10, and particularly preferable that it is 1 / 3 to 1 / 7.

[0056] The solid writing material according to the present invention may contain various other additives as needed. Examples of additives include fillers, other resins, non-discoloring colorants, antifungal agents, preservatives, antibacterial agents, UV inhibitors, light stabilizers, and fragrances.

[0057] Fillers are added to improve the strength of solid writing materials and adjust the writing feel. Examples of fillers used in this invention include talc, clay, silica, calcium carbonate, barium sulfate, alumina, mica, boron nitride, potassium titanate, and glass flakes. Talc and calcium carbonate are particularly preferred in terms of moldability and their effect on discoloration performance when microencapsulated pigments are used.

[0058] The filler content is preferably 10 to 65% by mass relative to the total mass of the solid writing material. Below this range, the strength tends to decrease, and above this range, the color development may decrease or the writing quality may deteriorate.

[0059] Other resins, such as natural and synthetic resins, can be used to improve the strength of solid writing instruments. Specifically, these include cellulose-based resins, pyrrolidone-based resins, acrylic resins, styrene-based resins, and resins containing basic groups.

[0060] The solid writing material according to the present invention may also contain non-thermochromic colorants such as dyes and pigments in addition to microcapsules. By combining such non-thermochromic colorants, it is possible to achieve not only color changes from colored to colorless or from colorless to colored, but also changes from one color to another.

[0061] Furthermore, a hindered amine compound may be added to the composition according to the present invention. Adding a hindered amine compound has the advantage of making the afterimage of the erased writing even less visible. Therefore, it is preferable because it can satisfy the re-writing requirement without impairing the appearance of the writing surface, and thus enhance marketability.

[0062] The aforementioned hindered amine compound is preferable because its molecular weight is 1,000 or less, resulting in high compatibility with other components and reduced bleed-out, thus allowing for the formation of clear handwriting even after time has passed.

[0063] Furthermore, it is preferable that the melting point of the hindered amine compound is 120°C or lower. A low melting point allows for the production of thermoreversible color-changing compositions, reversible thermocolor-changing microcapsule pigments, and solid writing materials using them without applying excessive heat during manufacturing, thereby preventing deterioration of the composition's components.

[0064] The solid writing material according to the present invention may also contain non-thermochromic colorants such as dyes or pigments to achieve a change from one color to another.

[0065] The solid writing instrument according to the present invention can be used as a writing instrument on its own, but its exterior can also be coated with an outer shell containing resin or the like. Such an outer shell prevents the solid writing instrument inside from being damaged by physical contact and can also contribute to improving the overall mechanical strength of the solid writing instrument. Such an outer shell generally contains fillers and excipients. Such an outer shell may or may not contain a coloring agent that contributes to the formation of the handwriting.

[0066] The solid writing material according to the present invention preferably has an outer diameter of 0.3 to 3.5 mm. An outer diameter within this range allows for use in writing instruments that use a chuck to hold and extend the lead, such as mechanical pencils. This is preferable because it allows for repeated use of only the lead, and enables the use of even a small portion of the lead remaining, thus being environmentally friendly. Furthermore, compared to conventional mechanical pencils, the absence of eraser residue is a significant advantage in terms of convenience. More preferably, the outer diameter is 0.5 to 2.0 mm, and even more preferably, 0.7 to 1.3 mm. The solid writing material according to the present invention possesses excellent strength; specifically, when the outer diameter is 0.9 mm, a bending strength of 30 MPa or more can be achieved.

[0067] The solid writing material of the present invention can write on various writing surfaces. Furthermore, the writing can be discolored by rubbing with a finger or by applying a heating or cooling device.

[0068] Examples of the aforementioned heating devices include electrically heated color change devices equipped with resistance heating elements, heated color change devices filled with hot water, etc., and the use of hair dryers. However, it is preferable to use a friction member as a means of easily changing the color.

[0069] The friction member is preferably made of an elastic material such as an elastomer, which is highly elastic and can generate appropriate friction and frictional heat during friction. The material of the friction member can be silicone resin, SEBS resin (styrene-ethylene-butylene-styrene block copolymer), polyester resin, etc. While a solid writing pen set can be obtained by combining a solid writing pen with a friction member of any shape, providing the friction member on the exterior of the solid writing pen or the solid writing instrument containing the solid writing pen in an external container results in superior portability.

[0070] The solid writing material according to the present invention can be used in combination with a wooden barrel exterior in the shape of a so-called pencil, but it is preferable to use it in writing instruments that use solid writing material with a thin lead diameter, such as so-called mechanical pencils, because it can improve both the strength of the solid writing material and the density of the writing when writing. Furthermore, the solid writing material according to the present invention can be used in writing instruments that use a chuck to hold the lead and extend the lead, such as mechanical pencils.

[0071] The present invention provides a method for producing solid writing materials, which is conventionally known, such as heating and kneading a composition, followed by extrusion or injection molding. Furthermore, when heating and kneading the composition, a crosslinked product can be obtained by crosslinking an acid-modified polyolefin wax with a crosslinkable resin. [Examples]

[0072] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0073] (Manufacturing of microencapsulated pigments) A reversible thermochromic composition with color memory properties, comprising (a) 2.0 parts by mass of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide as component (a), 8.0 parts by mass of 2,2-bis(4′-hydroxyphenyl)hexafluoropropane as component (b), and 50.0 parts by mass of 4-benzyloxyphenylethyl capric acid as component (c), was heated and dissolved. A solution was mixed with 25.0 parts by mass of aromatic isocyanate prepolymer as a wall film material and 50.0 parts by mass of a co-solvent. This solution was emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution, and after continued stirring while heating, 2.5 parts by mass of water-soluble aliphatic-modified amine was added, and stirring was continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was centrifuged to isolate the reversible thermochromic microcapsule pigment.

[0074] Furthermore, when the particle size of the microcapsule pigment was measured using a Multisizer 4e (manufactured by Beckman Coulter, Inc.), it was found to be in the range of 0.5 to 5.0 μm. The complete decolorization temperature was 60°C, and the complete color development temperature was -10°C. The color reversibly changes from blue to colorless and from colorless to blue with temperature changes.

[0075] (Examples 1-6 and Comparative Examples 1-5) The formulations shown in Table 1 were heated and kneaded in a kneader, and the resulting kneaded material was compressed and molded in a press to obtain solid cursive writing materials with an outer diameter of φ0.9 mm and a length of 60 mm. The values ​​in the table represent mass %.

[0076] The kneaded materials obtained in each example were evaluated according to the following procedure. The results are shown in (Table 1).

[0077] The resulting solid cursive writing was evaluated as follows.

[0078] Bending strength: The bending strength of each example of solid cursive writing material was measured in accordance with JIS-S6005:2007. A higher numerical value indicates greater strength.

[0079] Discoloration characteristics: Handwriting obtained with solid cursive writing material was erased using a friction eraser to create erased traces. The resulting erased traces were left at 0°C for 24 hours, and the traces after 24 hours were visually evaluated. A: No re-discoloration of the erased area was observed, and good discoloration characteristics were obtained. B: There was almost no re-discoloration of the erased areas, and it maintained good discoloration characteristics. C: Some discoloration reappeared in the erased areas, and slight deterioration in the discoloration characteristics was observed, but it was at a level that did not pose any practical problems. D: Re-discoloration of the erased area was confirmed, and a discoloration abnormality was observed.

[0080] [Table 1]

[0081] In the table: FH105: Talc (median diameter D50 = 5 μm, manufactured by Fuji Talc Co., Ltd.) HW2203A: Acid-modified polyethylene wax (High Wax 2203A, manufactured by Mitsui Chemicals, Inc.) HS-4100: α-olefin derivative (HS Crysta 4100, manufactured by Toyokuni Oil Co., Ltd.) JMR-10LL: Ultra-low saponification polyvinyl alcohol resin (JMR-10LL, manufactured by Nippon Vi-Poval Co., Ltd.) LM-10HD: Low-saponification polyvinyl alcohol resin (LM-10HD, manufactured by Kuraray Co., Ltd.) EP1010N: Ethylene oxide-propylene oxide copolymer (Alcox EP1010N, manufactured by Meisei Chemical Industry Co., Ltd.) S400: Low molecular weight polypropylene (Elmodu S400, manufactured by Idemitsu Kosan Co., Ltd.) TPAE-12: Polyamide elastomer (TPAE-12, polymerized fatty acid-based polyamide block copolymer, polyether ester amide, manufactured by T&K TOKA Corporation) PA-100A-S: Special polyamide resin (PA-100-AS, polymerized fatty acid polyamide, melting point 136℃, manufactured by T&K TOKA Corporation) SB305: Styrene acrylic ester resin (manufactured by Sanyo Chemical Industries, Ltd., number average molecular weight 4000) 770DF: Hindered amine light stabilizer (Tinuvin 770DF, manufactured by BASF Japan Ltd.)

[0082] These results show that the solid writing materials of the examples containing a combination of polyvinyl alcohol resin or polyamide resin exhibit superior flexural strength and discoloration characteristics compared to the case without either polyvinyl alcohol resin or polyamide resin (Comparative Example). Furthermore, it can be seen that the solid writing materials according to the present invention achieve superior properties compared to the case where polystyrene resin is omitted instead of polyamide resin (Comparative Example 1).

Claims

1. Microcapsule pigments containing functional materials, excipient material, Polyvinyl alcohol resin, and Polyamide resin It includes, The excipient is polyolefin wax, The polyvinyl alcohol resin is a partially saponified polyvinyl alcohol having a degree of saponification of 3 to 50 mopl%, The melting point of the polyamide resin is 50 to 150°C. A solid cursive writing instrument characterized by its features.

2. The aforementioned functional material, (i) A component consisting of an electron-donating color-producing organic compound, (b) A component consisting of an electron-accepting compound, (c) A reaction medium that causes the electron transfer reaction by the components of (a) and (b) to occur reversibly in a specific temperature range, The solid writing material according to claim 1, which is a reversible thermochromic composition comprising the above.

3. The solid writing material according to claim 1 or 2, wherein the weight-average molecular weight of the excipient is 1,000 to 100,000.

4. The solid writing body according to any one of claims 1 to 3, wherein the content of the polyvinyl alcohol resin is 5 to 30% by mass and the content of the polyamide resin is 1 to 10% by mass, based on the total mass of the solid writing body.

5. The solid writing instrument according to any one of claims 1 to 4, wherein the ratio of the polyamide resin content to the polyvinyl alcohol resin content is less than 1 / 1.

6. A solid writing instrument according to any one of claims 1 to 5, having a cylindrical shape and an outer diameter of 0.3 to 3.5 mm.

7. A mechanical pencil in which a solid writing instrument according to any one of claims 1 to 6 is held via a chuck and is arranged so as to extend the solid writing instrument as needed.

8. The mechanical pencil according to claim 7, further comprising a friction member.

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