A colored pencil lead, a method for manufacturing a colored pencil lead, and a replacement lead product comprising a colored pencil lead and a replacement lead case containing it.

Abstract

[Problem] To provide: a color pencil lead having exceptional color development and erasability of writing, a smooth feel, and exceptional storage stability; a method for manufacturing a color pencil lead; and a refill product comprising a color pencil lead and a refill case in which the same is accommodated. [Solution] The color pencil lead according to the present invention includes: a porous lead body that contains a body material, an inorganic binder, a coloring agent, and a high-boiling-point organic solvent having a boiling point of 250°C or higher; and a refractory liquid with which the pores of the porous lead body are filled. The color pencil lead includes bringing a coloring agent solution that contains a coloring agent and a high-boiling-point organic solvent into contact with a porous lead body obtained through firing, furthermore bringing the coloring agent into contact with an insoluble refractory liquid, and filling the voids in the porous lead body with the refractory liquid. The refill product according to the present invention comprises the color pencil lead and a case.

Description

Technical Field

[0001] The present invention relates to a colored pencil lead. More specifically, it relates to a colored pencil lead having excellent color development property and smooth writing feeling.

Background Art

[0002] Conventionally, colored pencil leads used in mechanical pencils etc. are obtained by extrusion molding a kneaded product mainly composed of a extender such as boron nitride and a binder such as clay, and containing an organic polymer compound etc. as required, and then firing at a high temperature, and impregnating ink containing a dye into pores of a obtained white porous base material. In such colored pencil leads, in order to express various color tones, it is desired to use various equipment and materials to realize more excellent color development property, and further improvement is desired also in erasability, stability over time, writing feeling etc.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention provides a colored pencil lead having excellent color development property of handwriting, high stability over time, and smooth writing feeling.

Means for Solving the Problems

[0005] The colored pencil lead according to the present invention includes an extender, an inorganic binder, a colorant, a high-boiling organic solvent capable of dissolving the colorant and having a boiling point of 250°C or higher, and forms a porous core body, and a non-volatile liquid which is insoluble in the colorant, The coloring agent, the high-boiling point organic solvent, and the non-volatile liquid are filled into the pores of the porous core.

[0006] Furthermore, the method for manufacturing colored pencil lead according to the present invention is (a) A kneading step of kneading a binder material and an inorganic binder to prepare a mixture, (b) Extrusion step of extruding the mixture to produce a linear molded product, (c) A firing step in which the linear molded product is fired to create a porous substrate, (d) An impregnation step in which a coloring agent solution containing a coloring agent and a high-boiling point organic solvent with a boiling point of 250°C or higher is brought into contact with the porous substrate and impregnated. (e) A drying step in which the porous substrate after the impregnation step is heated at a temperature of 200°C or less to form a porous core. (f) A filling step in which a non-volatile liquid that cannot dissolve the coloring agent is brought into contact with the porous core, thereby filling the voids in the porous core with the non-volatile liquid. It is characterized by containing [a certain element]. [Effects of the Invention]

[0007] By writing with the colored pencil lead according to the present invention, it is possible to create handwriting with excellent color development. Furthermore, the colored pencil lead according to the present invention provides a smooth writing experience. Moreover, the colored pencil lead according to the present invention has high storage stability and excellent color development and erasability over time. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view of the refill product according to the present invention. [Figure 2] A longitudinal cross-sectional view of a refill case that can be used in the present invention. [Figure 3] A cross-sectional view of a refill case that can be used in the present invention. [Figure 4] A longitudinal cross-sectional view of another refill case that can be used in the present invention. [Figure 5]Cross-sectional view of another refill case that can be used in the present invention. [Figure 6] Longitudinal sectional view of still another refill case that can be used in the present invention. [Figure 7] Cross-sectional view of still another refill case that can be used in the present invention.

Mode for Carrying Out the Invention

[0009] <Colored pencil lead> The configuration of the colored pencil lead according to the present invention will be described as follows.

[0010] The porous core used in the colored pencil lead of the present invention contains a base material and an inorganic binder as main components. Examples of the base material include white materials such as titanium oxide, mica, talc, boron nitride, alumina, calcium carbonate, and colored materials such as molybdenum disulfide, tungsten disulfide, and graphite. The colored pencil lead according to the present invention preferably forms a vivid writing trace. Further, when a fluorescent coloring agent is used as the coloring agent to form a fluorescent writing trace, it is preferable that the coloring agent does not inhibit the color development. For this reason, in order to form a writing trace with high brightness, it is preferable to use a white base material. In particular, the use of boron nitride is preferable because the base material does not inhibit color development and the strength of the colored pencil lead is increased.

[0011] Examples of the inorganic binder include clays such as kaolinites, halloysites, montmorillonites, sericites, bentonites, ceramics, zeolite, diatomaceous earth, activated clay, silica, aluminum phosphate, silicone resin, and silicone rubber, and these can be used alone or in combination.

[0012] The mixing ratio of the base material and the inorganic binder, which are the main components of the porous core, is not particularly limited, but is preferably 9:1 to 7:3 by mass ratio.

[0013] In the present invention, the porous core is typically a combination of a coloring agent and a high-boiling organic solvent in a porous base material. The coloring agent may be localized in a part of the porous base material mainly composed of a extender or an inorganic binder, or may be uniformly dispersed throughout the porous base material, but it is preferably localized in a part of the porous core. Specifically, it is preferable that the coloring agent is attached or adsorbed in the pores of the porous base material. At this time, the coloring agent may be in the state of fine particles or in a state dissolved or dispersed in the high-boiling organic solvent described later. When the coloring agent exists in the final pencil lead core in such a state, penetration of the coloring agent into the interior of the paper is suppressed during writing, and the color development property and erasability are improved. Here, the coloring agent typically forms a layer or a phase in the pores. That is, it is common to form a uniform or non-uniform layer on the inner surface of the pores or to adhere in a lump. In the present invention, the pores mean the pores in the matrix, such as a porous base material, from which an organic solvent or the like has been removed from the pencil lead core. For example, in the porous core, an organic solvent or the like may penetrate into the pores, but the pores of this porous core mean the pores after removing an organic solvent or the like from the porous core.

[0014] In the present invention, the porous core comprises an extender, an inorganic binder, a coloring agent, and a high-boiling organic solvent. Generally, a pencil lead is manufactured by firing a mixture of an extender and a binder after molding, but the same method can also be applied in the present invention. That is, it can be manufactured by firing a mixture of an extender and an inorganic binder and adsorbing or attaching a coloring agent and a high-boiling organic solvent to the formed porous base material (details will be described later). Alternatively, the extender, the inorganic binder, the coloring agent, and the high-boiling organic solvent may be mixed and fired, but in such a case, it is preferable to use a coloring agent with high heat resistance or a high-boiling organic solvent having a boiling point higher than the firing temperature. On the other hand, in the case of the former method, a coloring agent with low heat resistance or a high-boiling organic solvent having a boiling point lower than the firing temperature can also be used.

[0015] Furthermore, a porous core can also be manufactured by compressing a mixture containing a binder, an inorganic binder, inorganic substances or water-soluble resins, and a coloring agent as needed, under high pressure, and then immersing it in water or a solvent to remove the inorganic substances or water-soluble resins.

[0016] Furthermore, the porosity of the porous core used in the present invention is not particularly limited, but it is preferably in the range of 1 to 50%, more preferably in the range of 5 to 50%, even more preferably in the range of 10 to 40%, and particularly preferably in the range of 20 to 40%. If the porosity is less than 1%, the amount of coloring agent and non-volatile liquid present in the pores decreases, which tends to result in poor color development and slight resistance when writing. If it is greater than 50%, the strength of the resulting porous core tends to decrease, making it prone to breakage. A porosity in the range of 1 to 50% is preferable because it provides good color development, a smooth writing feel, and maintains the strength of the fired colored pencil lead.

[0017] The porosity of the porous substrate used in this invention can be measured by the following method, with reference to JIS R1634 (1998). First, the dry mass (W1) of the porous substrate is measured. Next, it is immersed in a highly permeable liquid (e.g., benzyl alcohol) and allowed to absorb the liquid until the pores of the porous substrate are saturated, after which the mass in the liquid (W2) is measured. Furthermore, the porous substrate is removed from the liquid, the liquid adhering to its surface is removed, and then the saturated mass (W3) is measured. Using these measured values, the porosity can be determined by the formula (1) shown below.

[0018] Porosity = (W3-W1) / (W3-W2)×100 (1)

[0019] The porosity of colored pencil leads or porous cores can also be measured using a similar method. However, before applying the above method for measuring the porosity of porous substrates, it is necessary to remove organic solvents, etc., by heating or reducing the pressure. When measuring the porosity of colored pencil leads or porous cores, even after removing the solvents, some organic solvents may remain in the pores. Therefore, there may be a slight difference between the porosity of the porous substrate and the porosity of colored pencil leads or porous cores. Taking such differences into account, the porosity of the porous substrate is preferably in the range of 5 to 50%, more preferably in the range of 10 to 40%, and particularly preferably in the range of 20 to 40%.

[0020] As a coloring agent, dyes or pigments can be used. Alternatively, colored pigments, which are resins dyed with dyes, can also be used. While dyes generally have low heat resistance, they readily penetrate porous substrates when in solution, facilitating the manufacture of pencil leads according to the present invention. For this reason, dyes are preferred as the coloring agent.

[0021] The dyes that can be used in the present invention are not particularly limited and include general dyes and fluorescent dyes.

[0022] Examples of general dyes include oil-soluble dyes, acid dyes, basic dyes, and metal-containing dyes. Furthermore, salt-forming dyes of these dyes include salt-forming dyes of acid dyes and basic dyes, salt-forming dyes of basic dyes and organic acids, and salt-forming dyes of acid dyes and organic amines. More specifically, Varifast Black 1802, Varifast Black 1805, Varifast Black 1807, Varifast Violet 1701, Varifast Violet 1704, Varifast Violet 1705, Varifast Blue 1601, Varifast Blue 1605, Varifast Blue 1613, Varifast Blue 1621, Varifast Blue 1631, Varifast Red 1320, Varifast Red 1355, Varifast Red 1360, Varifast Yellow 1101, Varifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (Orient Chemical Industry Co., Ltd.), Eisenspiron Black GMH-Special, Eisenspiron Violet CRH, Eisenspiron Blue Examples include GNH, Eisenspiron Blue 2BNH, Eisenspiron Blue C-RH, Eisenspiron Red C-GH, Eisenspiron Red C-BH, Eisenspiron Red C-PH, Eisenspiron Yellow C-GNH, Eisenspiron Yellow C-2GH, SPT Blue 111, SPT Blue GLSH-Special, SPT Red 533, SPT Orange 6, SBN Violet 510, SBN Yellow 530, and SRC-BH (Hodogaya Chemical Co., Ltd.).

[0023] Examples of fluorescent dyes include Basic Yellow 1, Basic Yellow 40, Basic Red 1, Basic Red 1:1, Basic Red 13, Basic Violet 1, Basic Violet 7, Basic Violet 10, Basic Violet 11:1, Basic Orange 22, Basic Blue 7, Basic Green 1, Acid Yellow 3, Basic Yellow 7, Acid Red 52, Acid Red 77, Acid Red 87, Acid Red 92, Acid Blue 9, Disperse Yellow 121, Disperse Yellow 82, Acid Red 83, Disperse Orange 11, Disperse Red 58, Disperse Blue 7, Direct Yellow 85, Direct Orange 8, Direct Red 9, Direct Blue 22, Direct Green 6, Solvent Yellow 44, Solvent Red 49, Solvent Blue 5, Solvent Green 7, and others.

[0024] These dyes may be used individually or in combination of two or more to adjust the color of the writing, etc., as long as they do not affect the performance of the colored pencil lead. Furthermore, other dyes may be used in combination with these dyes.

[0025] Furthermore, any pigment can be used as a coloring agent. Ultrafine pigments and processed pigments can also be used.

[0026] Furthermore, colored pigments, which are resins dyed with dyes or other substances, can also be used. Such colored pigments are preferable because they can improve color development.

[0027] Any resin can be used as the resin constituting the coloring pigment, such as acrylic resin, styrene-acrylonitrile resin, styrene resin, nitrogen-containing resin, polyethylene resin, or polypropylene resin. The dyes to be combined with these resins can be selected from those listed above.

[0028] Considering solubility in high-boiling point organic solvents, dispersibility and dispersion stability, and dyeability with dyes, it is preferable to use nitrogen-containing resins or styrene-acrylonitrile resins among these resins, with nitrogen-containing resins being more preferable. Among nitrogen-containing resins, melamine resins, polyamide resins, urethane resins, urea resins, or benzoquanamine resins are preferred. Furthermore, from the viewpoint of solubility and stability in high-boiling point organic solvents, melamine resins or polyamide resins are preferred, with melamine resins being more preferable.

[0029] Examples of colored pigments include the NKS-1000 series, MPI-500 series (manufactured by Nippon Fluorescent Chemicals Co., Ltd.), FNP series, and FM series (manufactured by Shinloihi Co., Ltd.).

[0030] These coloring pigments may be used in combination of two or more types, for example, to adjust the color of the handwriting, as long as the effects of the present invention are not impaired. Furthermore, dyes may be used in combination with these coloring pigments.

[0031] Furthermore, in this invention, it is also preferable to use a fluorescent coloring agent. By using such a coloring agent, fluorescent handwriting can be obtained, resulting in handwriting with richer color development. This makes it easier to use not only for simply writing letters, but also for drawing and marking.

[0032] The appropriate amount of coloring agent relative to the total mass of the colored pencil lead varies depending on the type, but it is preferably 0.1 to 30% by mass, more preferably 0.2 to 25% by mass, and most preferably 1 to 20% by mass.

[0033] When forming a porous core by combining a coloring agent with a porous substrate, the porous substrate containing a filler material and an inorganic binder is impregnated with a coloring agent solution obtained by dissolving the coloring agent in a solvent, and then, if necessary, a portion of the solvent is removed. (Details will be described later.) For this reason, it is preferable that the solvent used in the manufacturing process is capable of dissolving the coloring agent used.

[0034] The colored pencil lead according to the present invention contains a high-boiling point organic solvent with a boiling point of 250°C or higher that can dissolve the coloring agent contained in the lead. Such a solvent can impart excellent color development and writing feel to the colored pencil lead according to the present invention. Furthermore, because of its high boiling point, it is less likely to volatilize during the manufacturing process and storage, allowing it to maintain stable performance.

[0035] Here, a high-boiling point organic solvent being able to dissolve a coloring agent means that the solubility of the coloring agent in that high-boiling point organic solvent is 10 g / 100 g or more at 20°C, that is, 10 g or more of the coloring agent dissolves in 100 g of high-boiling point organic solvent at 20°C. The higher the solubility of the coloring agent, the greater the storage stability of the colored pencil lead tends to be, and a solubility of 30 g / 100 g or more is more preferable, and 40 g / 100 g or more is even more preferable.

[0036] Such solvents can be arbitrarily selected considering the solubility of the colorant used and other properties, but aromatic glycol ethers or aliphatic glycol ethers are preferred. Glycol ethers contain both ether groups and hydroxyl groups in their structure and generally have the characteristics of high solubility of dyes and resins, as well as high affinity for other organic solvents.

[0037] Examples of such high boiling point organic solvents include Diethylene glycol monophenyl ether (phenyldiglycol, 283°C), Diethylene glycol monobenzyl ether, (302°C), Triethylene glycol monobutyl ether (butyl triglycol, 271°C), Ethylene glycol monobenzyl ether (256℃) These are some examples. The numbers in parentheses indicate the boiling point (the same applies below).

[0038] Furthermore, as high-boiling point organic solvents, carboxylic acid esters of polyalkylene glycols or carboxylic acid esters of alcohols can be used.

[0039] Furthermore, higher fatty acids and higher alcohols with boiling points of 250°C or higher can also be used. Specifically, these include carboxylic acids with 10 or more carbon atoms, such as decanoic acid (259°C) and oleic acid (360°C), and alcohols with 12 or more carbon atoms, such as dodecyl alcohol (259°C) and myristyl alcohol (292°C). However, caution is necessary as higher fatty acids may cause corrosion if the colored pencil lead comes into contact with metal parts when used in a mechanical pencil.

[0040] It should be noted that some organic solvents, even if liquid at room temperature and pressure, may sublimate or undergo chemical reactions when heated under normal pressure conditions, making it impossible to accurately measure their boiling point. However, such organic solvents can sometimes be used as high-boiling-point organic solvents. In such cases, for example, if the weight loss rate after 30 minutes when held at 250°C under normal pressure is 10% by mass or less, the boiling point of that high-boiling-point organic solvent can be considered to be 250°C or higher.

[0041] The content of the high-boiling point organic solvent in the colored pencil lead according to the present invention is appropriately adjusted according to the purpose, but it is preferably 0.5 to 20% by mass, and more preferably 1 to 15% by mass, based on the total mass of the colored pencil lead. The content of the high-boiling point organic solvent can be measured by any method. For example, the presence of a high-boiling point organic solvent in the colored pencil lead can be confirmed by methods such as thermogravimetric analysis.

[0042] Furthermore, the colored pencil lead according to the present invention may contain an organic solvent other than the high-boiling point organic solvent (hereinafter sometimes referred to as a low-boiling point organic solvent). The low-boiling point organic solvent referred to here is different from the non-volatile liquid described later. Specifically, it is an organic solvent with a boiling point of less than 250°C that can dissolve the coloring agent. Here, the solubility of the coloring agent in the low-boiling point organic solvent means that the solubility of the coloring agent in that low-boiling point organic solvent is 10 g / 100 g or more at 20°C, that is, 10 g or more of the coloring agent dissolves in 100 g of the low-boiling point organic solvent at 20°C. The higher the solubility of the coloring agent, the higher the storage stability of the colored pencil lead tends to be, and a solubility of 30 g / 100 g or more is more preferable, and 40 g / 100 g or more is even more preferable.

[0043] Among low-boiling point organic solvents, those with relatively high boiling points, such as those with a boiling point of 150°C or higher but less than 250°C, are generally expected to compensate for the effects of high-boiling point organic solvents, such as improved writing feel. Also, those with relatively low boiling points, such as those with a boiling point of less than 150°C, are generally effective in reducing the viscosity of the coloring agent solution when impregnating porous substrates with coloring agents during the manufacturing process. However, most or all of these relatively low-boiling point solvents are removed during the manufacturing process and are therefore rarely present in colored pencil leads. Furthermore, the boiling point of the low-boiling point solvent is preferably 100°C or lower, more preferably 90°C or lower, even more preferably 85°C or lower, and still more preferably 80°C or lower.

[0044] Furthermore, the boiling point BP of the high boiling point organic solvent in the present invention H And the boiling point BP of low boiling point organic solvents L If we focus on the differences, BP H and BP LThe difference in boiling points is preferably 100 degrees or more, and more preferably 150 degrees or more. This difference in boiling points between the high-boiling point organic solvent and the low-boiling point organic solvent makes it possible to remove only the low-boiling point organic solvent in the manufacturing process described later. As a result, the colored pencil lead has excellent color development and writing quality provided by the high-boiling point organic solvent. Furthermore, the high-boiling point organic solvent does not volatilize easily during the manufacturing process or storage, allowing it to maintain stable performance.

[0045] Examples of such low-boiling point organic solvents include: Triethylene glycol monomethyl ether (249°C), Phenylcellulose (247°C), Propylene glycol monomethyl ether (243°C), Benzyl alcohol (205℃), 3-Methoxy-3-methyl-1-butanol (174℃), Xylene (139°C), Toluene (111℃), Isopropyl alcohol (82°C), Methyl ethyl ketone (79°C), Ethyl alcohol (78°C), Ethyl acetate (77℃), Acetone (56℃) These are some examples.

[0046] Of these, isopropyl alcohol, methyl ethyl ketone, ethyl alcohol, ethyl acetate, or acetone are preferably used.

[0047] The colored pencil lead according to the present invention has a non-volatile liquid filled in the pores of the porous lead body described above. This non-volatile liquid further improves the writing feel during writing.

[0048] In the present invention, a non-volatile liquid refers to a liquid that cannot dissolve the coloring agent and does not volatilize easily at room temperature. Here, "cannot dissolve" does not mean that the solubility of the coloring agent is zero, but rather that it is substantially insoluble. Here, the solubility of the coloring agent in the non-volatile liquid is preferably lower than the solubility in the high-boiling point organic solvent described above, and more specifically, the solubility of the coloring agent in the non-volatile liquid at 20°C is preferably less than 10 g / 100 g, and more preferably 5 g / 100 g or less.

[0049] Furthermore, while the boiling point of a non-volatile liquid is not particularly limited, it is preferable that the liquid does not volatilize below 250°C.

[0050] By using such a non-volatile liquid, the long-term stability of the colored pencil lead can be maintained at a high level, improving the writing experience. Furthermore, in replacement lead products, if the lead contains an organic solvent, there is a possibility that the lead and the case may fuse together inside the lead case. However, by including a non-volatile liquid in the colored pencil lead, such fusion can be improved.

[0051] While this improvement in fusion is also affected by the case material, a significant improvement is observed when the solubility parameter (hereinafter sometimes referred to as the SP value) of the non-volatile liquid used in this invention satisfies a specific relationship with the SP value of the resin material used in the refill case, which will be described later. This relationship will be described later, but generally, the SP value of the non-volatile liquid is preferably 6 to 8. Here, while Fedors solubility parameter, Hildebrand solubility parameter, Hansen solubility parameter, etc., are known as SP values, in this invention, the Fedors solubility parameter is used as the solubility parameter.

[0052] Furthermore, it is preferable that the non-volatile liquid has low viscosity in order to facilitate impregnation into the pores of the porous core.

[0053] Furthermore, the surface tension of the non-volatile liquid is preferably 35 mN / m or less, more preferably 30 mN / m or less, and even more preferably 25 mN / m or less, because it allows for excellent impregnation into the pores of the porous core, ensuring that the non-volatile liquid is evenly and uniformly impregnated throughout the porous core, resulting in a colored pencil lead with excellent writing and erasability. Here, the surface tension can be measured under conditions of 25°C by the method specified in JIS K2241.

[0054] Specific examples of preferred low-volatility liquids include those selected from the group consisting of silicone oil, fluorine-based oil, mineral oil, vegetable oil, and liquid paraffin, with silicone oil being more preferred. Silicone oil exhibits little viscosity change with temperature and excellent stability. By using silicone oil as the low-volatility liquid, colored pencil leads become less susceptible to environmental changes and the effects of time. Furthermore, when the colored pencil lead is used in a mechanical pencil, it is less likely to corrode metal components such as the tip opening, chuck, and lead storage cylinder of the mechanical pencil. Dimethyl silicone and methylphenyl silicone are particularly preferred as silicone oils, and modified silicones can also be cited as preferred. It is also preferable that the silicone oil does not easily dissolve the coloring agent. By making it difficult to dissolve the coloring agent, the penetration of the coloring agent into the paper along with the low-volatility liquid in the formed writing is suppressed, thereby improving erasability. As for the liquid paraffin, those with 14 or more carbon atoms are preferred.

[0055] The content of the non-volatile liquid relative to the total mass of the colored pencil lead is preferably 5 to 40% by mass, more preferably 8 to 45% by mass, and even more preferably 10 to 35% by mass.

[0056] The colored pencil lead according to the present invention may contain various additives to the extent that they do not affect its performance. Specific examples of additives include surfactants, preservatives, fungicides, and resins.

[0057] The shape of the colored pencil lead according to the present invention is not particularly limited, but is generally a linear body with a circular cross-section. For example, as a colored pencil lead for mechanical pencils, the cross-sectional diameter is preferably 0.2 to 2.0 mm, and more preferably 0.3 to 0.7 mm. The length is preferably 30 to 100 mm, and more preferably 40 to 70 mm. When applied to general colored pencils held on a support such as wood, the cross-sectional diameter is preferably 0.5 to 3.0 mm, and more preferably 0.8 to 2.0 mm. Since general colored pencils are often manufactured by sandwiching long colored pencil leads between pieces of wood or other materials before cutting, the length is not limited, but is generally 1,000 mm or less.

[0058] The colored pencil lead according to the present invention can achieve high physical strength when using a porous substrate manufactured by firing. This is thought to be because the coloring agent forms a uniform or non-uniform layer on the inner surface of the pores, or adheres in clumps. The bending strength of the colored pencil lead according to the present invention is preferably 120 MPa or higher, and more preferably 180 MPa or higher. Here, the bending strength can be measured by the method specified in JIS S 6005:2007.

[0059] Furthermore, the colored pencil lead according to the present invention can be formulated without acidic components. Since colored pencil leads are often used in mechanical pencils and the like, they frequently come into contact with metal materials. Therefore, by formulating the lead without acidic components, corrosion of the metal parts of the mechanical pencil can be suppressed. Accordingly, it is preferable that the colored pencil lead according to the present invention does not contain acidic materials.

[0060] <Method of manufacturing colored pencil lead> The method for manufacturing colored pencil leads according to the present invention is not particularly limited. However, (a) A kneading step of kneading a binder material and an inorganic binder to prepare a mixture, (b) Extrusion step of extruding the mixture to produce a linear molded product, (c) A firing step in which the linear molded product is fired to create a porous substrate, (d) An impregnation step in which a coloring agent solution containing a coloring agent and a high-boiling point organic solvent with a boiling point of 250°C or higher is brought into contact with the porous substrate and impregnated. (e) A drying step in which the porous substrate after the impregnation step is heated at a temperature of 200°C or less to form a porous core. (f) A filling step in which a non-volatile liquid that cannot dissolve the coloring agent is brought into contact with the porous core, thereby filling the voids in the porous core with the non-volatile liquid. It is preferable to manufacture it by a method comprising the following. This method is described below.

[0061] (a) Mixing process First, a mixture is prepared by kneading a binder material and an inorganic binder. This mixture will be the main component of the porous substrate. During mixing, organic solvents, plasticizers, etc., may be added as needed. The organic solvent used here is to give the raw material mixture fluidity and make the mixture homogenized, and is almost completely removed during the calcination process. It is independent of the high-boiling point organic solvents, low-boiling point organic solvents, and non-volatile liquids mentioned above.

[0062] (b) Extrusion process, Next, the formed mixture is extruded to create a linear molded product. Since the colored pencil lead according to the present invention is generally preferably formed into a linear body with a circular cross-sectional shape, it is formed into a linear molded product by extrusion molding.

[0063] (c) Firing process The resulting linear molded material is dried as needed and then fired to create a porous substrate. The firing removes the organic solvent contained in the mixture, and the filler material and inorganic binder sinter to form a porous substrate. The firing conditions are not particularly limited as long as they allow the material to sinter and form a porous substrate; for example, the maximum temperature can be 650-1000°C. Furthermore, to avoid abrupt temperature changes, the firing temperature can be increased continuously or in stages. In such cases, the heating rate can be, for example, 10-100°C / hr. It is also preferable to fire the material at a constant temperature for a certain period, for example, 0.5-2 hours, after raising it to the set temperature. Moreover, these conditions can be arbitrarily combined depending on the purpose. For example, conditions such as heating from room temperature to 650°C at a rate of 10°C / hr in an oxygen atmosphere, and then maintaining the temperature at 650°C for 1 hour, or heating from room temperature to 1000°C at a rate of 100°C / hr, and then maintaining the temperature at 1000°C for 1 hour, can be used.

[0064] (d) Impregnation process After cooling the formed porous substrate as needed, the porous substrate is brought into contact with a solution containing a coloring agent and a high-boiling point organic solvent. In this step, the coloring agent solution penetrates into the pores present in the porous substrate. The impregnation method can be atmospheric pressure impregnation or reduced pressure / pressure impregnation.

[0065] The colorant content of the above colorant solution is not particularly limited, but based on the total mass of the solution, the colorant concentration is preferably 5 to 50% by mass, more preferably 5 to 45% by mass, and particularly preferably 10 to 40% by mass. If it is less than this range, the colorant content will be low and the color development will tend to be poor, and if it is more than this range, the improvement in color development will not be seen in proportion to the amount of colorant added, and there is a risk that the solution's stability over time will be low, such as the colorant precipitation over time. In addition, surfactants can be added to the solution to improve the solubility and stability of the colorant.

[0066] Furthermore, using a mixed solvent combining a high-boiling point organic solvent and a low-boiling point organic solvent as the solvent for the coloring agent solution lowers the viscosity of the coloring agent solution, making impregnation easier, and also facilitates the formation of voids within the pores during the subsequent drying process. In this case, it becomes easier to impregnate the pitted liquid into the pores of the core, and the effects obtained by impregnating with the pitted liquid can be fully realized. As such a low-boiling point organic solvent, a solvent that evaporates at 100°C or below is preferred, more preferably at 90°C or below, and even more preferably at 80°C or below. Aliphatic alcohol having 1 to 4 carbon atoms is even more preferred. The mixing ratio of the high-boiling point organic solvent and the low-boiling point organic solvent can be adjusted depending on the difference in their boiling points and the solubility of the coloring agent, but for example, the ratio of the mass of the high-boiling point organic solvent to the mass of the low-boiling point organic solvent is preferably 1:1 to 1:15, more preferably 1:1 to 1:12, even more preferably 1:1.5 to 1:10, and particularly preferably 1:1.5 to 1:7.

[0067] (e) Drying process Subsequently, the porous substrate after the impregnation process is heated to remove some of the solvent contained in the solution impregnated into the pores. As a result, the coloring agent and high-boiling point organic solvent remain in the pores and are adsorbed or adhered to them. Then, some of the solvent is removed by heating, or the impregnation of the solvent into the porous substrate progresses, forming voids in the pores and creating a porous core. Drying is carried out at a temperature of 200°C or lower, but if the coloring agent solution contains a solvent with a relatively low boiling point, it can be carried out at an even lower temperature, for example, 100°C or lower. Drying at a lower temperature is preferable because it can reduce energy costs.

[0068] (f) Filling process After cooling the porous core that has been formed as needed, a non-volatile liquid is brought into contact with it. This process fills the voids formed in the porous core with the non-volatile liquid. The conditions at this time are not particularly limited, but for example, a temperature of 60°C for 6 to 12 hours can be used. For filling with the non-volatile liquid, atmospheric pressure impregnation or reduced pressure / pressure impregnation methods can be used.

[0069] If necessary, further washing or other processes can be performed to obtain the colored pencil lead according to the present invention.

[0070] <Refill cases and refill products> The replacement lead product according to the present invention comprises a colored pencil lead housed in a replacement lead case. Preferably, a resin material having a solubility parameter that differs by 1.5 or more from the solubility parameter of the non-volatile liquid is placed on a portion of the inner surface of the replacement lead case where the pencil lead may come into contact. The replacement lead case is made of a relatively hard material to protect the colored pencil lead, but it is generally made of resin from the viewpoint of ease of manufacture and cost. However, if an appropriate resin is not selected, the colored pencil lead and the resin material may adhere to each other.

[0071] According to the inventors' studies, it was found that such adhesion can be suppressed when the difference between the SP value of the non-volatile liquid contained in the colored pencil lead and the SP value of the resin constituting the lead case is sufficiently large. Since such adhesion naturally occurs in the part of the lead case that comes into contact with the colored pencil lead, it is sufficient that the SP value of the resin placed in that part of the lead case differs sufficiently from the SP value of the non-volatile liquid. Specifically, it is preferable that the difference between the SP value of the non-volatile liquid and the SP value of the resin material placed in the part that comes into contact with the colored pencil lead be 1.5 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and still more preferably 5.0 or more.

[0072] The difference between the SP value of the non-volatile liquid and the SP value of the resin material is preferably 1.5 or more, but either can be larger. Furthermore, as long as these relative differences are satisfied, the SP values ​​of the non-volatile liquid and the resin material are not particularly limited. For example, if a silicone oil with an SP value of 7.2 is used as the non-volatile liquid, the SP value of the resin material must be 5.7 or less, or 8.7 or more. Examples of resin materials that satisfy these conditions include polystyrene (8.6-9.7), vinyl acetate resin (9.4), vinyl chloride (9.5-9.7), polycarbonate (9.7), polyacetal (11.1), acrylonitrile styrene resin (12.8), and acrylonitrile-butadiene-styrene copolymer synthetic resin (12.1-15.0). Generally, the SP value of resin materials tends to be higher than that of non-volatile liquids. The SP value of the resin material is preferably 8.5-15.

[0073] Furthermore, it is preferable that the remaining amount of pencil lead in the replacement lead product according to the present invention be visible from the outside. For this reason, it is preferable to use a transparent resin material for the case. Therefore, it is preferable to use a resin that is highly robust, has excellent moldability, and is transparent, and in particular, it is preferable to use polycarbonate (9.7) or acrylonitrile styrene resin (12.8).

[0074] In the present invention, the shape of the replacement lead case is not particularly limited, and any conventionally known shape can be adopted. For example, a replacement lead case can be adopted that comprises a storage section for housing colored pencil leads, and a lid section that temporarily seals and deforms an opening provided in the storage section, thereby allowing the colored pencil leads to be removed. Here, the lid section can be any object generally referred to as a lid section. Specifically, during transport or storage, the opening provided in the storage section is temporarily sealed to hold the colored pencil leads inside the replacement lead case, and when necessary, the lid can be detached, moved, or rotated to allow the colored pencil leads to be removed from the opening in the storage section.

[0075] As the simplest form, a replacement lead case can be exemplified as shown in Figure 1, which consists of a cylindrical storage section 101 with one end sealed and a lid section 102 that fits into an opening formed at one end of the storage section. The colored pencil lead 103 stored in this replacement lead case can be removed from the storage section by removing the lid section 102 from the storage section 101.

[0076] In the refill product according to the present invention, a specific resin material is placed on a portion of the refill case that may come into contact with the colored pencil lead. In the refill case shown in Figure 1, the entire inner surface of the space defined by the inner surface of the housing and the bottom surface 102a of the lid after fitting becomes a portion that may come into contact with the colored pencil lead of the refill case. In the present invention, a specific resin material is placed on a portion of the refill case that may come into contact with the colored pencil lead.

[0077] Here, "placing resin material in a specific area" means, for example, forming that area out of resin material, placing a component made of resin material in that area, or covering that area with resin material. For example, in the case of a refill case having the shape shown in Figure 1, this can be achieved by forming the entire housing area out of a specific resin material. Of course, the lid may be formed out of resin material, or the inner surface of the housing area may be covered with resin material.

[0078] In this invention, if a specific resin material is placed on a portion of the part of the lead case that can come into contact with the colored pencil lead, it is possible to suppress the adhesion of the colored pencil lead to the lead case. However, it is preferable that the ratio of the area where the specific resin material is placed to the total area of ​​the part of the lead case that can come into contact with the colored pencil lead is high. Specifically, it is preferable that the area where the specific resin material is placed is 50% or more, more preferably 80% or more, and particularly preferably 90% or more, relative to the total area of ​​the part of the lead case that can come into contact with the colored pencil lead. Ideally, it is preferable that the specific resin material is placed on all parts of the lead case that can come into contact with the colored pencil lead. Therefore, in the lead case of Figure 1, depending on the dimensions, the adhesion of the colored pencil lead can be suppressed by molding the housing part with a resin material having a specific SP value.

[0079] Furthermore, a lead replacement case like the one shown in Figures 2 and 3 can also be used. This lead replacement case has a lid 202 detachably attached to a storage section 201 that can hold lead replacements. In this lead replacement case, an engaging piece 202a is formed on the lid 202, protruding from its lower end, and a recessed portion 201a is formed on the storage section that matches the engaging piece 202a. By forming it in this way, when the engaging piece 202a of the lid is combined to match the recessed portion 201a of the storage section, the protruding portion and the recessed portion engage with each other, allowing the lid to be stably attached to the storage section. The protruding portion and the recessed portion can also be formed in reverse. Even in such a lead replacement case, the adhesion of colored pencil leads can be suppressed by forming the entire storage section 201 using a specific resin material. In addition, the inner surface of the storage section 201 may be covered with a specific resin material.

[0080] Furthermore, a replacement lead case like the one shown in Figures 4 and 5 can also be used. This case is also a replacement lead case in which a lid portion 402 is detachably attached to a storage portion 401 for storing colored pencil leads. An engaging piece 402a is formed on the lid portion 402 protruding from its lower end, and a recessed portion 401a is formed on the storage portion 401 that matches the engaging piece 402a. By forming it in this way, when the engaging piece 402a of the lid is combined to match the recessed portion 401a of the storage portion, the protruding portion and the recessed portion engage with each other, allowing the lid to be stably attached to the storage portion. The protruding portion and the recessed portion can also be formed in reverse. In such a replacement lead case as well, the adhesion of colored pencil leads can be suppressed by forming the entire storage portion 401 using a specific resin material.

[0081] Furthermore, a replacement lead case like the one shown in Figures 6 and 7 can also be used. This case houses the colored pencil lead inside the storage section 601. By rotating the lid 602 around the pivot axis 602D, the colored pencil lead can be held in the storage section or removed from the lead exit 603. Specifically, the lead exit 603 can be opened by rotating the lid 602 upright, and the exit 603 can be closed by tilting the lid 602 sideways. In this replacement lead case, a non-circular mounting hole 604E is formed in the lid fixing member 604, and a groove 604F is formed in the lid fixing member 604 that crosses the mounting hole, so that the mounting hole can be expanded. In addition, an arc-shaped groove is formed in the lid fixing member on the opposite side of the exit, and a pivot axis 602D with a non-circular cross-section is formed in the lid. The end on the side with the rotating shaft is formed in a semicircular shape, and a protrusion of an appropriate width is formed on the edge of the semicircular end in the direction from the front wall toward the back, and the rotating shaft of the lid is rotatably attached to the mounting hole of the lid fixing member. When the lid is tilted to the side to close the opening, the rotating shaft of the lid engages with the mounting hole of the lid fixing member, and the protrusion covers the groove that crosses the mounting hole of the lid fixing member. When the lid is raised to open the opening, the protrusion of the lid comes into contact with the stopper portion of the groove which is made up of an arc of the lid fixing member, and the rotation of the lid is stopped. Even in such a replacement lead case, the adhesion of colored pencil leads can be suppressed by forming the entire storage section 601 with a specific resin material. [Examples]

[0082] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0083] [Manufacturing Example 101] [Mixing process, extrusion process, and baking process] Boron nitride 45 parts by mass Silica 45 parts by mass 10 parts by mass of polyvinyl alcohol 100 parts by mass of water The above mixture was heated and kneaded using a kneader and a three-roll machine while evaporating the moisture. The resulting mixture was extruded to a predetermined diameter to obtain a linear molded product. This linear molded product was heated in argon gas at a heating rate of 10°C / hour to 600°C and held for 5 hours. Then, in an oxygen atmosphere, it was heated at 100°C / hr and fired at 900°C for 1 hour to obtain a porous substrate with a porosity of 25% and a cross-sectional diameter of 0.55 mm.

[0084] [Impregnation process] Coloring agent (blue dye) 30 parts by mass High boiling point organic solvent (phenyl diglycol) 10 parts by mass Low boiling point organic solvent (ethyl alcohol) 50 parts by mass Resin (ketone resin) 10 parts by mass The above mixture was stirred at 30°C until uniformly mixed to obtain a coloring agent solution.

[0085] The porous substrate obtained in the firing process was immersed in the above-mentioned coloring agent solution at a temperature of 30°C and held there for 6 hours.

[0086] [Drying process] The porous substrate, after undergoing the impregnation process, was held at 80°C for 6 hours to evaporate and remove the low-boiling point organic solvent in the pores of the porous substrate, thereby obtaining a porous core.

[0087] [Filling process] The porous core obtained in the drying process was immersed in silicone oil heated to 80°C and held for 6 hours to obtain a colored pencil lead. Next, excess silicone oil adhering to the surface of the colored pencil lead was removed by shaking it off with a centrifuge to obtain the colored pencil lead of Example 101 impregnated with 12.5% ​​by mass of silicone oil. Furthermore, thermogravimetric analysis of this colored pencil lead confirmed the presence of phenyldiglycol. Its content was 1% by mass or more.

[0088] [Examples 102-110, Comparative Examples 101-103] Colored pencil leads were obtained in the same manner as in Example 101, except that each component was changed to those listed in Table 1. Thermogravimetric analysis and manufacturing conditions confirmed that the colored pencil leads in Examples 102-110 and Comparative Example 102 contained high-boiling point organic solvents. Note that Comparative Examples 102 and 103 were not filled with a non-volatile liquid. [evaluation] The performance of the obtained colored pencil leads was evaluated using the following method.

[0089] [Method for evaluating writing feel and handwriting color development] Using colored pencil leads, draw on high-quality paper (equivalent to writing paper A as defined in the old JIS P3201; made from 100% chemical pulp, with a weighing range of 40-157 g / m²). 2 The writing surface was tested by writing on paper with a whiteness of 75.0% or higher, and the writing feel was evaluated by a sensory test (Writing feel 1). The color development of the resulting handwriting was also evaluated (Handwriting color development 1). Furthermore, the colored pencil leads, which had been left at 25°C for four weeks after manufacturing, were used to write on the aforementioned high-quality paper, and the writing feel (writing feel 2) and the color development of the resulting handwriting (handwriting color development 2) were evaluated by sensory testing. (Evaluation criteria for writing feel 1 and 2) A: It writes very smoothly. B: Allows for smooth writing. C: The brushstrokes feel slightly rough and heavy. D: The brush feels rough and heavy. (Evaluation criteria for handwriting color development 1 and 2) S: The color payoff is excellent. A: The colors are vibrant. B: The color is slightly inferior, but still good. C: Poor color development. D: It can write, but the color reproduction is very poor. E: Unable to write, handwriting is not visible.

[0090] [Method for evaluating the erasability of handwriting] The erasing performance was evaluated by a sensory test (Erasing Performance 1) after erasing the writing in accordance with the erasing performance test for plastic erasers disclosed in JIS S 6050-2008. In addition, the erasing performance was evaluated by a sensory test using writing lines that had been left in a 25°C environment for 4 weeks after writing, in accordance with the erasing performance test for plastic erasers disclosed in JIS S 6050-2008 (Erasing Performance 2). The existing product refers to the mechanical pencil lead "Product name: Neox Color Eeno (Yellow)" manufactured by Pilot Corporation. (Evaluation criteria for extinction ability 1 and 2) A: It's better than existing products. B: Equivalent to existing products. C: Not erasable.

[0091] [Table 1-1]

[0092] [Table 1-2] In the table: Blue dye B: Oil Blue 613 (manufactured by Orient Chemical Industry Co., Ltd.) Red dye R: Spiron Red C-PH (manufactured by Hodogaya Chemical Co., Ltd.) Pink fluorescent pigment P: NKS1007 (manufactured by Nippon Fluorescent Chemicals Co., Ltd., a mixture of polyamide resin and CI Basic Violet 11:1) Yellow fluorescent pigment Y: NKS1005 (manufactured by Nippon Fluorescent Chemicals Co., Ltd., a mixture of polyamide resin and CI Basic Yellow 40) Surfactant: Neugen EA-137 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) SO1: Dimethyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-96-50cs. Surface tension: 20.8 N / m) SO2: Methylphenyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-96-100cs) [Examples 201-202, Comparative Example 201] Each example of colored pencil lead was obtained in the same manner as in Production Example 101, except that the components were changed to those listed in Table 2. Thermogravimetric analysis and manufacturing conditions confirmed that each example of colored pencil lead contained a high-boiling point organic solvent. Comparative Example 201 was not filled with a non-volatile liquid.

[0093] [Examples 201-202, Comparative Example 201] The obtained colored pencil leads were each housed in the lead cases shown in Figure 2 to create replacement lead products. The resin material used for the housing portion of these lead cases is shown in Table 2, and more than 90% of the area of ​​the part of the lead case that can come into contact with the colored pencil leads is composed of this resin material.

[0094] [Method for evaluating the adhesion of colored pencil lead] For each refill product, the colored pencil lead was kept in contact with the inner surface of the refill case's storage compartment for 14 days at 50°C, and the adhesion of the lead was evaluated according to the following criteria.

[0095] (Evaluation criteria for adhesion) A: The colored pencil lead does not adhere to the storage compartment at all. B: A small amount of colored pencil lead adheres to the storage compartment, but it can be easily removed. C: Colored pencil lead is stuck to the storage compartment.

[0096] [Method for evaluating writing feel and handwriting color development] The evaluation was performed using the same evaluation method as in Example 101.

[0097] [Table 2] Blue dye B: Oil Blue 613 (manufactured by Orient Chemical Industry Co., Ltd.) Pink fluorescent pigment P: NKS1007 (manufactured by Nippon Fluorescent Chemicals Co., Ltd., a mixture of polyamide resin and CI Basic Violet 11:1) AS: Acrylonitrile styrene resin (SP value 12.8) PC: Polycarbonate (SP value: 9.7) SO1: Dimethyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-96-50cs, SP value: 7.3, surface tension: 20.8 N / m) [Explanation of Symbols]

[0098] 101 Storage Unit 102 Lid 102a Bottom surface of the lid 103 Colored pencil lead 201 Storage Unit 201a Engagement piece 202 Lid 202a Recessed part 401 Accommodation Unit 401a Concavity 402 Lid 402a Engaging piece 601 Accommodation Unit 602 Lid 602D Rotation axis 603 Exit 604 Lid fixing member 604E Mounting Holes

Claims

1. A binder material selected from the group consisting of titanium dioxide, mica, talc, boron nitride, alumina, and calcium carbonate, An inorganic binder selected from the group consisting of clay, ceramics, zeolite, diatomaceous earth, activated clay, silica, and aluminum phosphate, A colorant selected from the group consisting of oil-soluble dyes, acid dyes, basic dyes, gold-containing dyes, and salt-forming dyes thereof, and color pigments obtained by dyeing resins with these dyes, A high-boiling point organic solvent, selected from the group consisting of aromatic glycol ethers or aliphatic glycol ethers, which is capable of dissolving the coloring agent and has a boiling point of 250°C or higher, A porous core comprising, A non-volatile liquid selected from the group consisting of silicone oil, fluorinated oil, mineral oil, vegetable oil, and liquid paraffin, which is insoluble in the coloring agent. It includes, A colored pencil lead characterized in that the coloring agent, the high-boiling point organic solvent, and the non-volatile liquid are filled in the pores of the porous core.

2. The colored pencil lead according to claim 1, wherein the content of the high-boiling point organic solvent is 0.5 to 20% by mass, based on the total mass of the colored pencil lead.

3. The colored pencil lead according to claim 1 or 2, wherein the solubility of the coloring agent in the high-boiling point organic solvent at 20°C is 10 g / 100 g or more.

4. The colored pencil lead according to any one of claims 1 to 3, wherein the solubility of the coloring agent in the non-volatile liquid at 20°C is lower than the solubility of the coloring agent in the high-boiling point organic solvent at 20°C.

5. The colored pencil lead according to any one of claims 1 to 4, wherein the porosity of the porous core is 1 to 50%.

6. The colored pencil lead according to any one of claims 1 to 5, wherein the porous core is a fired core.

7. (a) A kneading step to prepare a mixture by kneading a binder selected from the group consisting of titanium dioxide, mica, talc, boron nitride, alumina, and calcium carbonate with an inorganic binder selected from the group consisting of clay, ceramics, zeolite, diatomaceous earth, activated clay, silica, and aluminum phosphate. (b) Extrusion step of extruding the mixture to produce a linear molded product, (c) A firing step in which the linear molded product is fired to create a porous substrate, (d) An impregnation step of contacting the porous substrate with a coloring solution containing a coloring agent selected from the group consisting of oil-soluble dyes, acid dyes, basic dyes, gold-containing dyes, and salt-forming dyes thereof, and coloring pigments obtained by dyeing resins with these dyes, and a high-boiling point organic solvent with a boiling point of 250°C or higher, selected from the group consisting of aromatic glycol ethers or aliphatic glycol ethers, and impregnating the porous substrate with the coloring solution. (e) A drying step in which the porous substrate after the impregnation step is heated at a temperature of 200°C or less to form a porous core. (f) A filling step in which the porous core is brought into contact with a non-volatile liquid selected from the group consisting of silicone oil, fluorine-based oil, mineral oil, vegetable oil, and liquid paraffin, which is insoluble in the coloring agent, and the non-volatile liquid fills the voids of the porous core. A method for manufacturing colored pencil lead, characterized by comprising [a certain component].

8. The method according to claim 7, wherein the coloring agent solution further comprises a low-boiling point organic solvent having a boiling point of less than 250°C.

9. A replacement lead product comprising a colored pencil lead according to any one of claims 1 to 6 and a replacement lead case containing the lead.

10. The replacement lead product according to claim 9, characterized in that a resin material having a solubility parameter that differs by 1.5 or more from the solubility parameter of the non-volatile liquid is placed on a part of the inner surface of the replacement lead case that can come into contact with the colored pencil lead.

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