JP7796093B2 - Thermochromic writing implements - Google Patents

Description

The present invention relates to a thermochromic writing instrument equipped with a ballpoint pen that has a so-called ball valve mechanism, in which the writing ball is constantly pressed by an elastic body so that it comes into close contact with the inner surface of the crimp at the tip end.

Traditionally, ballpoint pen-type writing instruments include so-called oil-based ballpoint pens, which contain high-viscosity (approximately 10,000 cp) ink primarily made of higher alcohol solvents directly in the ink reservoir; so-called water-based ballpoint pens, which contain low-viscosity ink primarily made of water in a fiber core called a wadding; and gel ballpoint pens, which have shear-thinning properties. However, with ballpoint pens using all types of ink, problems have been identified when the pen is stored and not being used (not observed when writing). Specifically, when a retractable ballpoint pen is stored with the nib protruding downward without being retracted, or when a cap-type ballpoint pen is stored in a pen stand with the nib protruding downward without the cap on, the ball valve at the nib can open, causing ink to leak, or the nib can dry out, making it impossible to write. These problems have created a need for further improvement. Therefore, to solve the above problems, it is common technical knowledge among those skilled in the art to prevent ink leakage from the pen tip by making the load of the ball valve at the pen tip higher than the axial load of the writing instrument, as in Patent Document 1 and Patent Document 2, or to prevent ink stains by using a padding member, as in Patent Document 3.

Patent Publication No. 2005-231033 Patent Publication No. 2014-8629 Patent Publication No. 2010-213912

However, when multiple writing instruments are stacked on top of each other, or when they are propped up in a holder after being tested in a store, and the shaft is not stored with the shaft in a vertical position but tilted at an angle of θ = 10 to 45° as shown in Figure 13, ink leakage can occur, and the leaked ink can harden, interfering with the rotation of the ball and leading to poor writing results.

The present invention aims to improve so-called ballpoint pens, in which the ball that serves as the writing part is loosely fitted inside the pen tip and cannot be removed, protruding from the tip. It also aims to solve the problem of ink leaking from the pen tip, causing it to become dirty and dry up, making it impossible to write with when the pen is stored with the shaft tilted in a pen stand or similar with the pen tip protruding downward.

As a result of diligent development by the inventors, the following inventions have been realized.
The present invention is a thermochromic writing instrument that contains a refill within a barrel, the refill comprising an ink reservoir tube containing thermochromic ink, and a ballpoint pen tip that is provided at the tip of the ink reservoir tube and has a rotatable writing ball loosely fitted therein, the ball being restricted in its forward and backward movement by a crimp at the tip end and by a receiving seat at the rear end, the ballpoint pen tip having an ink hole inside for directing thermochromic ink from the rear end, the ballpoint pen tip having a channel groove formed of a plurality of grooves that connect the receiving seat and the ink hole, and a biasing part of a resilient member that is installed so as to constantly press against the ball at the tip, either directly or via a movable member in between, the thermochromic writing instrument having a writing load of 40 g and an ink consumption of 200 mg or more when writing 100 m at a speed of 1 m per minute, characterized in that, between the writing ball pressing force P (N) exerted by the biasing part and the total weight M (N) of the writing instrument including the refill, P is 150% or more of M.

The barrel also contains a coil spring that biases the refill rearward, and an operating part that is provided at the rear of the barrel and is positioned behind the refill and works in conjunction with the refill. The refill is pushed forward or rotated to project from the tip of the barrel, thereby setting the refill in writing position. The ballpoint pen tip includes a writing ball and a holder that holds the writing ball at its tip. The tip of the holder is provided with a crimped part that holds the writing ball. The internal space of the holder contains a ball house that is provided at the tip of the holder and into which the writing ball is inserted, and a ball house at the rear of the holder. A back hole is formed from the end toward the tip to the vicinity of the ball house, and an ink guide hole is formed connecting the back hole and the ball house. The ball house has a cylindrical surface that is approximately parallel to the axis, a bottom surface that is a conical surface that is continuous with the cylindrical surface and tapers toward the rear, and a ball receiving seat on which the curved surface of the writing ball is transferred. Ink grooves that are radial grooves drilled from the ball house side toward the rear are formed at multiple locations evenly spaced around the ink guide hole, and a resilient member that urges the writing ball toward the tip is inserted into the back hole, and the tip portion of the resilient member is linearly oriented toward the tip. the writing ball has a diameter H, a writing ball projection dimension which is the distance by which the writing ball projects from the tip of the holder, a clearance K which is the amount by which the writing ball can move in the axial direction of the ballpoint pen tip within the holder, an inner diameter L of the cylindrical surface of the ball house, and an inner diameter A of the ink guide hole; When the outermost diameter of the ball seat is F, the wire diameter of the urging portion is G, and the diameter of the circumscribing circle of the ink groove is C, the clearance is (0.05 x H) ≦ K ≦ (0.1 x H), the writing ball is held in the crimped portion so that (J + K) < (0.4 x H), the inner diameter of the cylindrical surface of the ball house is formed so that L ≧ (H x 1.05) and F < (0.65 x H), the ink guide hole is formed so that A ≦ (0.6 x H), the wire diameter of the urging portion is formed so that (0.2 x A) ≦ G ≦ (0.6 x A), and the diameter of the circumscribing circle of the ink groove is formed so that C > H.

Furthermore, the viscosity of the thermochromic ink was 20 to 300 mPa·s at a shear rate of 3.84 (1/S) measured at 20°C using an E-type rotational viscometer.

Furthermore, the position of the operating part from the tip of the barrel to the rear end of the operating part remains constant before and after the writing element is inserted and removed.

In addition, an operating part protrudes from the rear end of the barrel, and the operating part has a friction part that easily changes color with thermochromic ink, and the surface of the friction part has an uneven surface.

This invention prevents ink from leaking or drying up from the pen tip, making it impossible to write, when the pen is stored at an angle in a pen stand or similar with the pen tip protruding downward.

1 is an overall view of a writing instrument showing an embodiment of the present invention. 1 is a front cross-sectional view of a refill housed in a writing instrument showing an embodiment of the present invention. 1 is a component diagram of a ballpoint pen tip, which is a writing part of a writing instrument showing an embodiment of the present invention. FIG. 4 is a cross-sectional view of the tip portion of the holder. FIG. 5 is a cross-sectional view taken along line II of FIG. 4. 2 is a cross-sectional view taken along line II-II of FIG. 4. FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 4. 4 is a cross-sectional view taken along the line IV-IV of FIG. 7 shows a ballpoint pen tip according to another embodiment in accordance with the cross-sectional view of FIG. 6. 1 is a partial cross-sectional view showing the state of the holder and the resilient member of the ballpoint pen tip according to the present invention, with the writing ball omitted. FIG. 4 is a front cross-sectional view of the tip of the ballpoint pen tip of FIG. 3. 12 is a cross-sectional view taken along line II of FIG. 11. 1 is an overall view showing a tilted state of a writing implement according to the present invention;

Embodiments of the present invention will be described in detail below with reference to the drawings. Corresponding components will be designated by the same reference numerals throughout the drawings. The writing end will be referred to as the tip or front, and the other end will be referred to as the rear end or rear.

Figure 1 shows a writing instrument 1 according to an embodiment of the present invention. An operating unit 3 protrudes rearward from the rear end of a barrel 2, and a ballpoint pen refill 5 housed inside the barrel 2 can be extended or retracted from a tip member 4 at the front of the barrel by operating the operating unit 3. A clip 6 is fixed to the side of the barrel 2, allowing it to be clipped between the barrel 2 and a pocket or piece of paper. The operating unit 3 can extend or retract the ballpoint pen refill 5 from the tip surface of the tip member 4 by pressing it forward in the axial direction or rotating it radially. The distance from the rear end surface of the operating unit 3 to the tip surface of the barrel 2 or the tip surface of the tip member 4 is constant regardless of whether the ballpoint pen refill 5 is extended or retracted. Apart from the tip of the ballpoint pen refill 5 protruding from the barrel 2 or the tip member 4 in the writing state, the writing instrument remains the same in both the writing and storage states, ensuring a consistent appearance of the writing instrument. Additionally, a coil spring (not shown) is housed inside the barrel 2, which urges the ballpoint pen refill backward.

The operating unit 3 has an uneven surface 7 formed on it to prevent slipping during operation. The uneven surface 7 is made up of protrusions, grooves, or a combination of protrusions and grooves. The uneven surface 7 may also have a matte finish.

The operating element 3 can function as a friction element when the ballpoint pen refill 5 contains thermochromic ink. It is designed to wear moderately so as not to damage the paper surface or cause the printed characters to fade. Specifically, it is preferable that the Taber abrasion amount be 10 mg or more when using the abrasion wheel CS-17 of a Taber abrasion tester under an abrasion test (ASTM D1044) specified in JIS K7204, with a load of 9.8 N and 1000 rpm. If the friction element has a Taber abrasion amount of less than 10 mg, the paper surface will be damaged and the printed characters will fade when the handwriting discolors due to friction.

The operating unit 3 may be formed from a rubber-elastic material such as a thermosetting rubber such as silicone rubber, nitrile rubber, ethylene propylene rubber, or ethylene propylene diene rubber; a thermoplastic elastomer such as a styrene-based elastomer, an olefin-based elastomer, or a polyester-based elastomer; a mixture of two or more rubber-elastic materials; or a mixture of a rubber-elastic material and a synthetic resin, configured to have a Taber abrasion of 10 mg or more. Furthermore, the operating unit 3 may be formed from a mixture of polypropylene resin and a styrene-based thermoplastic elastomer, or a mixture of polypropylene resin and an olefin-based thermoplastic elastomer, configured to have a Taber abrasion of 10 mg or more.

Furthermore, to adjust the Taber abrasion to 10 mg or more, alkylsulfonic acid phenyl ester, cyclohexanedicarboxylic acid ester, or phthalic acid plasticizers may be added to the material of the operation unit 3 to make it more flexible. By including alkylsulfonic acid phenyl ester, cyclohexanedicarboxylic acid ester, methacrylic acid ester, acrylic acid ester, acetyl tributyl citrate, adipic acid polyester, acetyl tributyl citrate, sebacate diester, diethylene glycol dibenzoate, or a phthalic acid plasticizer in the operation unit 3, the operation unit 3 becomes more susceptible to wear, making it possible to erase handwriting without damaging the paper surface or blurring printed characters. The operation unit 3 can also be used as a touch pen or stylus pen.

Furthermore, it is desirable that the operating unit 3 have a durometer D hardness of 30 or more as specified in JIS K6203. This ensures the required hardness and enables a more stable scraping operation.

Anti-aging agents such as amines, phenols, imidazoles, phosphorus compounds, or thioureas may also be added.

Amines include phenyl-α-naphthylamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, p,p'-dioctyldiphenylamine, p,p'-dicumyldiphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

Examples of phenols include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, styrenated methylphenol, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

Imidazoles include 2-mercaptobenzimidazole, zinc salts of 2-mercaptobenzimidazole, and nickel dibutyldithiocarbamate.

Other compounds that may be used include phosphorus compounds such as tris(nonylated phenyl)phosphite, thioureas such as 1,3-bis(dimethylaminopropyl)-2-thiourea and tributylthiourea, and waxes that prevent ozone degradation.

The above antioxidants may be used alone or in combination of two or more. Among these, it is preferable to use N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

The content of the antioxidant is preferably 0.1 to 5 parts by mass per 100 parts by mass of the polymer component. If the content of the antioxidant is less than 0.1 parts by mass, the anti-aging effect cannot be achieved. On the other hand, if the content of the antioxidant exceeds 5 parts by mass, blooming occurs in the polymer composition. The content of the antioxidant is more preferably 0.3 to 4 parts by mass.

Furthermore, the outer components of the writing instrument 1, such as the barrel 2, operating element 3, tip member 4, and clip 6, can also be impregnated with an antibacterial agent. Main materials used for the substrate containing the antibacterial agent of the present invention include synthetic resins such as styrene resin, acrylic resin, polyvinyl chloride, polyethylene, polypropylene, chlorosulfonated polyethylene, ABS resin, polycarbonate, polyamide, polyester, polyethylene terephthalate, polyacetal, phenolic resin, urea resin, natural rubber, and synthetic rubber, as well as paper, wood, and metal. Synthetic resins are typically used together with auxiliary agents such as colorants, fillers, stabilizers, and plasticizers. For example, resin materials that can be sterilized in an autoclave (120-130°C) include polyetherimides (PEI) such as "Ultem" manufactured by GE; polyethersulfones (PES) such as "Sumikaexcel" manufactured by Sumitomo Chemical, "Ultrason" manufactured by BASF, and "Radel" manufactured by AMOCO; polysulfones (PSF) such as "Udel" manufactured by AMOCO; polyetheretherketones (PEEK) such as "Victrex" manufactured by Victrex and "PEEK" manufactured by Mitsui Toatsu Co., Ltd.; and polyphenylene sulfide (PPS) such as "PPS" manufactured by Toray Industries, Inc.

Antibacterial agents used in the present invention include imidazole-based agents such as 2-(4-thiazolyl)benzimidazole, 2-benzimidazole carbamate methyl, 1-(butylcarbamoyl)2-benzimidazole carbamate methyl, 2-(methoxycarbonylamino)benzimidazole, and 2-(benzimidazole) carbamate methyl; 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 2-(4-thiazolin-3-one. thiocyanomethylthiobenzthiazole, 5-chloro-2-methyl-4-isothiazolin-3-one and other thiazole-based compounds; iodine-based compounds such as 3-iodo-2-propargylbutylcarbamic acid, 4-chlorophenyl-3-iodopropargylformal, diiodomethyl-p-tolylsulfone, 3-ethoxycarbonyloxy-1-bromo-1,2-diiodo-1-propene and other iodine-based compounds; 2,3,5,6-tetrachloroisophthalonitrile, 5-chloro-2,4,6 -trifluoroisophthalonitrile and other nitriles; p-chloro-m-cresol, phenols such as 2,4,4'-trichloro-2'-hydroxydiphenyl ether; haloalkylthios such as N-(fluorodichloromethylthio)phthalimide, N,N-dimethyl-N'-(dichlorofluoromethylthio)-N'-phenylsulfamide, N,N-dimethyl-N'-(dichlorofluoromethylthio)-N'-tolylsulfamide, N-(trichloromethylthio)phthalimide, tetrachloroethylthiotetrahydrophthalimide, and N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide; pyridines such as 2-pyridinethiol-1-oxide sodium, 2-pyridinethiol-1-oxide zinc, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; hexahydro-1,3,5-tris(2-hydroxyethyl)S-triazine, hexa triazines such as hydro-1,3,5-triethyl-S-triazine; bromines such as 2-bromo-2-nitro-1,3-propanediol and 1,2-dibromo-2,4-dicyanobutane; inorganics such as silver-zeolite, zinc-zeolite, silver-apatite, zirconium phosphate-silver, titania-silver, water-soluble glass-silver, calcium phosphate-silver, zeolite-copper, zeolite-zinc, zinc oxide, magnesium oxide, amorphous copper, sodium percarbonate, sodium hypochlorite, and barium metaborate; halodiallylureas such as trichlorocarban; guanidines such as chlorohexazine gluconate, chlorohexazine gluconate + cyclopirox olamine, and polyhexamethylenepyridine hydrochloride; fatty acid esters such as propyl glycol mono fatty acid esters and glycerin fatty acid esters; cellulose copper, copper cross-linked acrylonitrile-acrylic acid copolymer, and metal oxide-coordinated aminosilicon polymers. Polymer-coordinated metal systems such as zinc-coordinated acrylic acid polymers, 10,10'-oxybisphenoxyarsine, 8-oxyquinoline copper, methylenedithiocyanate, bis(dimethyldithiocarbamoyl)disulfide, 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, 3,5-dimethyltetrahydro-1,3,5-thiadiazine-2-thione, zinc dimethyldithiocarbamate, 4,4'-(2-ethoxyphenyl)-2,3-dimethylpropanol, ... Examples of suitable benzophenones include 2-(2-methyl-2-nitrotrimethylene)dimorpholine, levan-degrading enzymes, N-(2-hydroxypropyl)aminomethanol, 2-(methoxycarbonylamino)benzimidazole + 8-oxyquinoline copper, 5-(chloro-2-methyl-4-isothiazolin-3-one + 1,2-benzisothiazolin-3-one, and the like. Commercially available benzophenones include Polyalpha BN, ZAG, AG, and DN (manufactured by Towa Chemical Co., Ltd.), and Amteclean Z. Examples include MK-10, MK-2, MK-20, and MK-30 (manufactured by Matsushita Amtec Co., Ltd.). Also, select from masterbatch products such as Daikiller PEM701, PEM702, PEM703, ABM501, and PSM401 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and silver nanoparticles (IonFlare, manufactured by Yachiyo Kogyo Co., Ltd., average particle size = 5 nm).

As a method for incorporating an antibacterial agent into the outer surface components of the writing implement of the present invention, metal and wood can be coated with a coating material containing an antibacterial agent, but it is preferable to mix the antibacterial agent into the above-mentioned synthetic resin and the necessary auxiliary agents, and then mold it by injection or extrusion. It is also preferable to apply a rounded finish to the uneven parts and corners of the outer surface components, known as R-processing, and to combine the components so that grooves, gaps, etc. do not form.

When incorporating antibacterial agents into synthetic resins, the following methods can be used to enhance their effectiveness after molding: (1) Adding wax during molding or using a masterbatch in which wax and antibacterial agent are pre-mixed. (2) Adding additives such as zinc stearate, magnesium stearate, or lithium stearate to improve dispersion of the antibacterial agent. For example, the antibacterial agent and zinc stearate are mixed, stirred, and dissolved in a ratio of 7:3 to 8:2. That is, the antibacterial agent is heated to 120-180°C and melted, and then a metal stearate is added. The resulting mixture of antibacterial agent and additive is added at 1-2% to a resin such as polyolefin, PVC, or ABS, and mixed in a kneader for approximately 10 minutes. (3) Adding a surfactant. (4) Adding a hydrophilic polymer. This method increases the effectiveness of the antibacterial agent by moistening the surface of the molded product.

The amount of antibacterial agent contained in the components of the writing/applicating tool of the present invention varies depending on the type of antibacterial agent, the type of component, and the type of material used, and is not particularly limited, but is typically contained in the component at 0.001 to 30%.

Furthermore, by adding an antibacterial agent to the ink in the ballpoint pen refill 5, it is possible to impart antibacterial properties to handwriting as well.

As an antibacterial standard, it is preferable that the antibacterial activity value be 2.0 or higher when antibacterial processed products are tested according to JIS Z2801, which meets the guidelines set by the Antibacterial Products Council.

As shown in Figure 2, the ballpoint pen refill 5 is formed by attaching the ballpoint pen tip 20, which serves as the writing part, to an ink reservoir 16 containing ink 18 via a coupling 17, forming the ballpoint pen refill 15. The rear end of the ink 18 is filled with a grease-like ink follower 19 to prevent backflow from the tail end of the ink 18, and a float 19a with an equal specific gravity is housed within the ink follower 19 to enhance its followability. The ballpoint pen refill 5 is housed inside the barrel 2. In this embodiment, the writing instrument 1 including the ballpoint pen refill 5 weighs 25 g, and the spring pressure load at that time is 40 g. This prevents ink 18 from leaking from the ballpoint pen tip 20 even when the writing instrument 1 is stored at an angle with the ballpoint pen tip 20 protruding from the barrel 2.

The ink 18 is a thermochromic ink filled into the ink reservoir 16. Thermochromic ink maintains a predetermined color (first color) at room temperature (e.g., 25°C), changes to a different color (second color) when heated to a predetermined temperature (e.g., 65°C), and then returns to the original color (first color) when cooled to a predetermined temperature (e.g., -10°C). Generally, the second color may be colorless, and lines drawn in the first color (e.g., red) may be heated to become colorless. Thus, the friction body 9 rubs against the paper surface on which the lines are drawn, generating frictional heat, which causes the drawn lines to become colorless. Naturally, the second color may be a color other than colorless. More specifically, the thermochromic microencapsulated pigment used as the coloring material for the thermochromic ink may be a microencapsulated thermochromic composition containing at least a leuco dye, a color developer, and a color change temperature adjuster. The reversible thermochromic microencapsulated pigment preferably has an average particle size in the range of 0.3 to 2.5 μm. The reversible thermochromic microencapsulated pigment is preferably blended in an amount of 4 to 30 wt% of the total ink composition. The average particle size was measured using an N4Plus particle size analyzer (manufactured by COULTER). The sample was diluted with water to the recommended concentration for the N4Plus and measured at a temperature of 25°C. The ink viscosity, measured at a shear rate of 3.84 (1/S) at 20°C using an E-type rotational viscometer, is 20 to 300 mPa·s. The volume of ink contained in the ink reservoir 16 is 0.5 ml or more.

The leuco dyes that can be used are not particularly limited, as long as they are electron-donating dyes that function as color formers. Specifically, in order to obtain inks with excellent color development properties, conventionally known dyes such as triphenylmethane, spiropyran, fluoran, diphenylmethane, rhodamine lactam, indolylphthalide, and leucoauramine can be used alone (one type) or in a mixture of two or more types (hereinafter simply referred to as "at least one type").

Specific examples include 6-(dimethylamino)-3,3-bis[4-(dimethylamino)phenyl]-1(3H)-isobenzofuranone, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide. Lithium fluoride, 1,3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-dimethylaminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 2-(2-chloroanilino)-6-dibutylaminofluoran, 3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluoran fluoran, 1,2-benz-6-diethylaminofluoran, 1,2-benz-6-dibutylaminofluoran, 1,2-benz-6-ethylisoamylaminofluoran, 2-methyl-6-(N-p-tolyl-N-ethylamino)fluoran, 2-(N-phenyl-N-methylamino)-6-(N-p-tolyl-N-ethylamino)fluoran, 2-(3'-trifluoromethylanilino)-6-diethylaminofluoran, 3-chloro-6-chlorophenyl Examples of suitable leuco dyes include cyclohexylaminofluoran, 2-methyl-6-cyclohexylaminofluoran, 3-di(n-butyl)amino-6-methoxy-7-anilinofluoran, 3,6-bis(diphenylamino)fluoran, methyl-3',6'-bisdiphenylaminofluoran, chloro-3',6'-bisdiphenylaminofluoran, and 3-methoxy-4-dodecoxystyrinoquinoline, and at least one of these can be used. These leuco dyes have a lactone skeleton, pyridine skeleton, quinazoline skeleton, bisquinazoline skeleton, or the like, and develop color through ring-opening of these skeletons (rings). Preferably, a leuco dye that changes from colored to colorless upon heating is used.

The color developer that can be used is a component capable of causing the leuco dye to develop color, and examples thereof include phenolic resin compounds, salicylic acid metal chlorides, salicylic acid resin metal salt compounds, and solid acid compounds. Specific examples include o-cresol, tertiary butyl catechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, hexafluorobisphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcinol, dodecyl gallate, 2,2-bis(4'-hydroxyphenyl)propane, 4,4-dihydroxydiphenyl sulfone, 2-bis(4'-hydroxyphenyl)ethane, 2,2-bis(4'-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)sulfide, 1-phenyl-2-bis( 4'-hydroxyphenyl)ethane, 2-bis(4'-hydroxyphenyl)-3-methylbutane, 2-bis(4'-hydroxyphenyl)-2-methylpropane, 2-bis(4'-hydroxyphenyl)n-hexane, 2-bis(4'-hydroxyphenyl)n-heptane, 2-bis(4'-hydroxyphenyl)n-octane, 2-bis(4'-hydroxyphenyl)n-nonane, 2-bis(4'-hydroxyphenyl)n-decane, 2-bis(4' Examples include at least one of 2,2-bis(4'-hydroxyphenyl)n-dodecane, 2,2-bis(4'-hydroxyphenyl)butane, 2,2-bis(4'-hydroxyphenyl)ethyl propionate, 2,2-bis(4'-hydroxyphenyl)-4-methylpentane, 2,2-bis(4'-hydroxyphenyl)hexafluoropropane, 2,2-bis(4'-hydroxyphenyl)n-heptane, and 2,2-bis(4'-hydroxyphenyl)n-nonane.

The amount of developer used can be selected arbitrarily depending on the desired color density and is not particularly limited, but it is usually preferable to select an amount within the range of approximately 0.1 to 100 parts by weight per 1 part by weight of the leuco dye.

The color change temperature regulator is a substance that controls the color change temperature during color development of the leuco dye and color developer, and conventionally known substances can be used. Examples include alcohols, esters, ketones, ethers, acid amides, azomethines, fatty acids, and hydrocarbons.

Specific examples include at least one of bis(4-hydroxyphenyl)phenylmethane dicaprylate (C7H5), bis(4-hydroxyphenyl)phenylmethane dilaurate (C2H23), bis(4-hydroxyphenyl)phenylmethane dimyristate (C13H27), bis(4-hydroxyphenyl)phenylethane dimyristate (C13H27), bis(4-hydroxyphenyl)phenylmethane dipalmitate (C5H30), bis(4-hydroxyphenyl)phenylmethane dibehenate (C21H43), and bis(4-hydroxyphenyl)phenylethylhexylidene dimyristate (C13H27).

The viscosity of the ink to which the shear thinning agent has been added is preferably 20 to 300 mPa·s at a shear rate of 3.84 (1/S) as measured at 20°C using an E-type rotational viscometer, and the shear thinning index is preferably 0.1 to 0.9. By achieving the above-mentioned viscosity range and shear thinning index, ink leakage and backflow can be further prevented. The shear thinning index (n) is a value calculated by applying the shear stress value (T) and shear rate value (j) to the empirical formula T = Kjn (K is the non-Newtonian viscosity coefficient) obtained from rheological measurements using a viscometer.

Figure 3 shows the ballpoint pen tip 20, which is the writing part of this embodiment. The ballpoint pen tip 20 is composed of a holder 21, a writing ball 35 held at the tip of the holder 21, and a resilient member 40 housed inside the holder 21.

The holder 21 is formed by cutting a cylindrical piece of stainless steel material. As shown in Figure 3 (A), its tip portion is cut into a tapered, approximately conical shape to form the tapered portion 22. On the other hand, the rear end portion is formed as the inserted portion 24 with a reduced outer diameter. This portion is inserted into the joint 17, which will be described later. Furthermore, the tip of the writing ball 35 held inside the tapered portion 22 is exposed from the tip edge, and the end of the tapered portion 22 is pressed inward to form the crimped portion 23, which has been deformed to reduce its diameter. The internal space of the holder 21 is formed as a ball house 26 inside the tapered portion 22 into which the writing ball 35 is inserted, a back hole 28 provided from the rear end of the holder 21 in the tip direction to the vicinity of the ball house 26, and an ink guide hole 30 connecting the back hole 28 and the ball house 26. Ink grooves 31 are formed at a plurality of locations evenly spaced around the ink guide hole 30, and are grooves that radiate through the ink guide hole 30 from the ball house 26 side to a tip portion 29 of the back hole 28. A resilient member 40 that urges the writing ball 35 in the tip direction is inserted into the back hole 28, and the tip portion of the resilient member 40 is formed in a straight rod shape and can be moved in the tip direction. The writing ball 35 is formed as a biasing portion 41 that extends through the ink guide hole 30 and contacts the rear end of the writing ball 35, biasing it. An inwardly protruding inner convex portion 32 is formed at a position in contact with the rear end of each ink groove 31 at the tip portion 29 of the back hole 28. When the inner diameter of the ink guide hole 30 is A, the inner diameter of the tip portion 29 of the back hole 28 is B, the diameter of the circumscribing circle of the ink groove 31 is C, and the diameter of the inscribing circle of the inner convex portion 32 is D, the relationships A<B<C and D<B are satisfied. The inner convex portion 32 is formed by utilizing the deformation that occurs when the ink groove 31 is formed. The biasing portion 41 contacts the inner convex portion 32 without coming into contact with the ink groove 31.

The holder 21 refers to the "main body portion of the ballpoint pen tip 20 excluding the writing ball 35," and can be formed, for example, by cutting a cylindrical metal material such as stainless steel. The tapered portion at the tip of the holder 21 is called the "tapered portion 22." For example, if the holder 21 is formed from a cylindrical metal material, the tapered portion 22 will be formed by cutting. The "tip" here refers to the side of the writing tip of the ballpoint pen tip 20, and it goes without saying that the opposite side is the "rear end." There are no particular restrictions on the rear end of the holder 21, but it can be cut to reduce the outer diameter to form a portion that is inserted directly into the ink reservoir 16, or a portion that is inserted into a fitting 17 or the like that is interposed between the ink reservoir 16 and the ink reservoir 16.

The ball house 26 is the space formed in the area from the tip side to the inner circumference of the tapered portion 22, into which the writing ball 35 is inserted. When the holder 21 is formed from a metal cylindrical material, the ball house 26 is formed by cutting from the tip. The writing ball 35 inserted into the ball house 26 is held in place by the "crimped portion 23" which narrows the tip edge of the tapered portion 22 inward to prevent it from falling out. From the standpoint of ink flowability and writing ball retention, it is desirable that the inner diameter L of the inner cylindrical surface of the ball house 26 be at least 1.05 times the diameter H of the writing ball 35, more preferably at least 1.10 times but less than 1.15 times.

The back hole 28 is a central hole that extends from the rear end of the holder 21 to a point just short of the ball house 26, and is formed by cutting when the holder 21 is made of a cylindrical metal material. It is also desirable for the back hole 28 to have an inner diameter that gradually decreases from the rear end of the holder 21 as it approaches the ball house 26.

The ink guide hole 30 is a central hole with a smaller diameter than the back hole 28 that connects the back hole 28 and the ball house 26.

The ink grooves 31 are multiple axial grooves evenly spaced around the ink guide hole 30. When the holder 21 is formed from a metal column, the ink grooves 31 are formed by cutting from the bottom surface 27 of the ball house 26 using a broaching tool. The ink grooves 31 extend all the way to the tip 29 of the back hole 28. This allows ink guided to the tip of the back hole 28 to reach the ball house 26 via the ink grooves 31 and the ink guide hole 30. For processing stability, it is desirable to make the diameter C of the circumscribing circle of the ink groove 31 smaller than the inner diameter of the ball house 26. Furthermore, it is desirable to make the diameter C of the circumscribing circle of the ink groove 31 larger than the diameter of the writing ball 35. This prevents the bottom surface 27 of the ball house 26 from wearing away due to the long rotation of the writing ball 35 during writing, which could lead to the writing ball 35 clogging the ink groove 31. This also contributes to stable ink outflow.

The resilient member 40 is preferably a coil spring that minimizes clogging of the ink guide hole 30, but a rubber rod or damper can also be used as long as it constantly presses the writing ball 35 forward when stationary. In knock-type ballpoint pens, where the writing tip is constantly exposed to the outside air, the resilient member 40 is a necessary component for preventing ink from dripping when the writing tip is left facing downwards. Of course, there is no problem with using such a resilient member 40 in a cap-type ballpoint pen, where the writing tip is sealed by putting the cap on when not in use, since the pen may be stored upside down without the cap on. Furthermore, when using shear-thinning ink, using the resilient member 40, particularly a coil spring, makes it easier to generate shear force in the ink as the coil spring moves internally during writing, improving ink outflow.

The biasing portion 41 formed at the tip of this resilient member 40 penetrates from the back hole 28 through the ink guide hole 30 and abuts against the rear end of the writing ball 35 located inside the ball house 26. The elasticity of the resilient member 40 constantly biases the writing ball 35 toward the tip. This biasing portion 41 is formed in the shape of a straight rod. It is desirable that the wire diameter G of the biasing portion be between 20% and 60% of the inner diameter A of the ink guide hole.

The inward convex portion 32 is a protrusion formed to protrude inward at a position that contacts the tip portion 29 of the back hole 28 and the rear end of the ink groove 31. Because this inward convex portion 32 is provided to correspond to each of the multiple ink grooves 31, it is equally spaced about the axis, just like the ink grooves 31. Furthermore, the inner surface of the inward convex portion 32 is finished, as necessary, by cutting or other processing to have an inner diameter D that is smaller than the inner diameter B of the tip portion 29 of the back hole 28. In other words, the ink groove 31 in the portion of the ink guide hole 30 with the highest fluid resistance before the ink reaches the writing ball 35 has a through structure. Furthermore, the inner diameter B of the tip portion 29 of the back hole 28 is set smaller than the diameter C of the circumscribing circle of the ink groove 31 and larger than the inner diameter A of the ink guide hole 30. Furthermore, the ink groove 31 is machined up to the tip portion 29 of the back hole 28. The inward protrusion 32 is formed by a deformed portion that occurs when cutting the ink groove 31, such as a metal portion that is cut and pushed toward the rear end of the ink groove 31 during the process. With the above configuration, if the tip of the biasing portion 41 of the elastic member 40 tilts toward the ink groove 31, it will come into contact with the inner surface of the inward protrusion 32 before reaching the ink groove 31. Further movement toward the ink groove 31 is then prevented. This prevents the elastic member 40 from becoming stuck in the ink groove 31, even if the width of the ink groove 31 is designed to be larger than the diameter of the biasing portion 41 of the elastic member 40, and improves the outflow of ink with high static viscosity.

There are no particular restrictions on the size of the writing ball 35 as long as it is in the form of a ballpoint pen tip 20, but a particularly significant effect is achieved with a relatively large ball diameter of 0.9 mm or more. As for the number of ink grooves 31, two or more will not pose any problems with ink outflow, but three wide, evenly spaced grooves are particularly desirable.

Next, with reference to Figures 3 through 10, the manufacturing process for the ballpoint pen tip 20 according to the present invention will be described. First, the tip end of a stainless steel cylindrical material is tapered to form the tapered portion 22. Next, the outer diameter near the rear end of the holder 21 is reduced to form the insertion portion 24 (Figure 3(A)). The back hole 28 is then drilled, reducing its diameter in several stages from the rear end of the holder 21 to the middle of the tapered portion 22 (Figures 3(B) and 4). Next, an ink guide hole 30 is drilled from the tip of the holder 21 to the back hole 28, and then a drill with a diameter slightly larger than the outer diameter of the writing ball 35 is used again from the tip to form the ball house 26 (Figure 4). Next, an ink groove 31 is formed around the ink guide hole 30 from the bottom surface 27 of the ball house 26 using a broaching tool (Figures 5 and 10). As shown in Figure 5, which is a cross section taken along line I-I in Figure 4, and Figure 6, which is a cross section taken along line II-II in Figure 4, three ink grooves 31 are arranged radially and equidistantly around the ink guide hole 30. The ink grooves 31 extend all the way to the tip 29 of the back hole 28 (Figure 4). When the ink grooves 31 are formed, the pressed portion is pushed toward the rear end, causing the inner periphery of the portion that bulges inward. This is then smoothly machined with a drill to form an inward protrusion 32 (Figure 4). As shown in Figure 5 and Figure 7, which is a cross section taken along line III-III in Figure 4, the inward protrusion 32 is visible toward the rear end of the ink groove 31 when viewed from the front end. Furthermore, as shown in Figure 8, which is a cross section taken along line IV-IV in Figure 4, the inward protrusion 32 is formed to protrude inward from the tip 29 of the back hole 28.

Here, the inner diameter of the ink guide hole 30 is A, the inner diameter of the tip portion 29 of the back hole 28 is B, the diameter of the circumscribing circle of the ink groove 31 is C, and the inner diameter of the inner circumferential surface of the inward convex portion 32 is D. As shown in Figures 5 and 7, D<A<C, and as shown in Figure 8, D<B. Furthermore, a comparison with D, which is the same size, in Figures 7 and 8 clearly shows that A<B and B<C. Therefore, from these figures, A<B<C and D<B.
Note that A>D as shown in Fig. 7 is just one example, and it is also possible to make A<D as in another embodiment shown in Fig. 9. However, if the dimensional difference A<D is too large, it becomes difficult for ink to flow out, so the relationship A≈D is desirable.

Then, a writing ball 35 made of cemented carbide is inserted into the ball house 26, and the tip of the tapered portion 22 is then pressed inward with a crimping tool to form the crimped portion 23 (Figures 3(A), (B), and 11). By ensuring that the sphericity of the writing ball is 1.0 μm or less, the ball's rotation can be stabilized, resulting in a comfortable writing experience. The sphericity is measured using a sphericity measuring device (ROUNDTEST RA-2000, manufactured by Mitutoyo Corporation). The writing ball 35 is also formed with a maximum surface roughness Ra of 10 nm. This is because if the surface roughness Ra of the writing ball 30 exceeds 10 nm, severe wear of the receiving seat occurs during writing, reducing the amount of ink flow as the writing distance increases. In the worst case, ink flow may stop, making writing impossible. The surface roughness Ra was measured using a non-contact surface profiler (Zygo NewView 7200) under the following conditions: lens magnification: 50x, evaluation length: 100 μm, Gaussian filter: 25 μm; all other conditions conform to JIS B0601 (Product Geometric Characteristics Specifications - Surface Texture). A spring member 40 formed from a coil spring is inserted into the back hole 28. The tip of the spring member 40 is shaped like a straight rod and is referred to as the biasing portion 41. The tip of the biasing portion 41 passes through the ink guide hole 30 and contacts the rear end of the writing ball 35, constantly pressing it toward the tip. A portion of the rear end of the holder 21 is crimped inward, forming the fixing portion 25 that prevents the spring member 40 from falling off (Figure 3(B)).

In this ballpoint pen tip 20, as shown in Figure 10, if the biasing portion 41 at the tip of the elastic member 40 becomes eccentric toward the ink groove 31, it abuts against the inward convex portion 32 and does not come into contact with the ink groove 31. Therefore, even if the width of the ink groove 31 is designed to be larger than the diameter of the biasing portion 41, the biasing portion 41 will not get stuck in the ink groove 31.

Figure 11 is a front cross-sectional view of the tip of the ballpoint pen tip 20. The diameter of the writing ball 35 is 0.5 mm or more, preferably 0.9 to 1.2 mm. Furthermore, if the diameter of the writing ball 35 is H, the writing ball extension dimension, which is the distance the writing ball 35 protrudes from the tip of the holder 21 as shown in Figure 12, is J, and the clearance, which is the amount the writing ball 35 can move within the holder 21 in the axial direction of the ballpoint pen tip 20, is K, the clearance is (0.05 x H) ≤ K ≤ (0.1 x H), and the writing ball 35 is held in the holder 21 so that the relationship (J + K) < (0.4 x H) holds. Furthermore, the outer diameter of the crimped portion 23 is chamfered to reduce frictional resistance when writing at an angle.

Figure 12 is a detailed enlarged front view of the tip of the ballpoint pen tip, cut along section I-I in Figure 11. The ball house 26 has a cylindrical surface 26b that is approximately parallel to the axis, a conical bottom surface 27 that is continuous with the cylindrical surface 26b and tapers rearward, and a ball receiving seat 27c on which the curved surface of the writing ball 35 is transferred to the bottom surface 27. As shown in Figure 4, if the inner diameter of the cylindrical surface 26b of the ball house 26 is L, the inner diameter of the ink guide hole 30 is A, and the outermost diameter of the ball receiving seat is F, then the ball house 26 is formed so that L ≧ (diameter H of the writing ball × 1.05) and F < (0.65 × H). The ink guide hole 30 is formed so that its inner diameter A is 60% or less of the diameter H of the writing ball, and ink grooves 31, which are grooves that radiate from the ball house 26 toward the back hole 28, are formed at three equally spaced locations around the periphery of the ink guide hole 30. The diameter C of the circumscribed circle of the ink grooves 31 is made larger than the diameter H of the writing ball 35, so that a stable writing flow rate can be maintained even if the ball seat 27c wears and the diameter increases.

Figure 13 shows a writing instrument according to an embodiment of the present invention tilted at an angle θ. By configuring the writing ball pressure P (N) generated by the biasing unit and the total weight M (N) of the writing instrument, including the refill, so that P is 150% or more of M, writing inability due to ink leakage or drying-up from the ballpoint pen tip 20 can be avoided even in a tilted state. The total weight M of this writing instrument is 0.157 N (16 g), and the writing ball pressure P is 0.245 N (25 g). Furthermore, if a metal component is used to create a luxurious feel in the barrel, increasing the total weight M to 0.245 N (25 g) or more, a more significant effect can be achieved by correspondingly setting the writing ball pressure P to 0.39 N (40 g) or more. Furthermore, a writing distance of 100 m or more can be achieved by holding at least 0.5 ml of ink in the ballpoint pen refill 5. Furthermore, at a writing speed of 1.0 m/min and a writing load of 40 g, the ink consumption per 100 m should be 200 to 400 mg when the outer diameter of the writing ball 35 is 0.5 to 0.7 mm, and 500 to 1000 mg when it is 0.9 to 1.2 mm. If the ink consumption is low relative to the ball diameter H, the handwriting will be thin and difficult to read, while if it is high, the handwriting will be difficult to dry and there is a risk of staining your hands after writing. A ball diameter of 0.9 mm to 1.2 mm is particularly suitable, as it provides a smooth writing feel. Note that ink consumption is measured using a measuring device and under writing conditions that comply with JIS S 6061, except for the writing conditions mentioned above.

Furthermore, in the case of a retractable writing instrument in which the ball diameter H (mm) and the writing ball pressing force P (N) exerted by the biasing section are related by the following formula: (15 x H x H) < P < (60 x H x H). Also, in the case of a retractable writing instrument in which the ballpoint pen refill 5 is biased toward the rear of the barrel by a coil spring, the writing ball pressing force P (N) exerted by the biasing section, the return spring pressing force S (N), and the total weight M (N) of the writing instrument are related by the following formula: 50 M < S < (50 x M + 20 x P). This is advantageous as it ensures high performance in terms of ball flight, smearing during strong impacts, and a balance of writing performance.

1 Writing implement 2 Barrel 3 Operation part 4 Tip member 5 Ballpoint pen refill 6 Clip 7 Concave and concave part 16 Ink reservoir tube 17 Joint 18 Ink 19 Ink follower 19a Float 20 Ballpoint pen tip 21 Holder 22 Tapered part 23 Crimped part 24 Inserted part 25 Fixed part 26 Ball house 26b Cylindrical surface of ball house 27 Bottom surface 27c Ball receiving seat 28 Back hole 29 Tip part of back hole 30 Ink guide hole 31 Ink groove 32 Inward convex part 33 Cylindrical surface 35 Writing ball 40 Elastic member 41 Urging part A Inner diameter of ink guide hole B Inner diameter of tip part of back hole C Diameter of circumscribed circle of ink groove (outer diameter of ink groove on ball house side)
D Diameter of the inscribed circle of the inward convex part F Outermost diameter of the ball seat G Wire diameter of the biasing part H Diameter of the writing ball J Writing ball projection dimension K, which is the distance the writing ball protrudes from the tip of the holder Clearance L Inner diameter of the cylindrical surface of the ball house M Total weight of the writing implement P Writing ball pressing force by the biasing part S Pressing force of the return spring

Claims (2)

The refill is housed in a barrel, and the refill comprises an ink reservoir tube containing thermochromic ink, a ballpoint pen tip provided at the tip of the ink reservoir tube, a writing ball loosely fitted in a rotatable manner and restricted in its forward and backward movement by a crimp at the tip end and by a receiving seat at the rear end, and an ink hole inside for leading out the thermochromic ink from the rear end, the ballpoint pen tip having a channel groove formed by a plurality of grooves communicating with the receiving seat and the ink hole, and a biasing part of a resilient member installed so as to constantly press the ball at the tip directly or via a movable member, and a writing load of 40 g. A thermochromic writing instrument that consumes 200 mg or more of ink when writing 100 m at a speed of 1 m per minute, is configured such that P (N) of the writing ball pressing force by the urging part and M (N) of the total weight of the writing instrument including the refill are equal to or greater than 150% of M, the surface of the barrel contains an antibacterial agent, and is provided with an operating part that protrudes from the rear end of the barrel and allows the refill to be operated to extend and retract from the front end of the barrel, the operating part is a friction part that can discolor the thermochromic ink, and the friction part has added thereto an antioxidant that is 0.1 to 5 parts by mass per 100 parts by mass of polymer components . The ballpoint pen tip comprises a writing ball having a diameter of 0.9 to 1.2 mm and a holder that holds the writing ball at its tip, and the tip of the holder is provided with a crimped portion that holds the writing ball. The internal space of the holder is formed with a ball house that is provided at the tip of the holder and into which the writing ball is inserted, a back hole that is provided from the rear end of the holder toward the tip to the vicinity of the ball house, and an ink guide hole that connects the back hole to the ball house. The ball house has a cylindrical surface that is approximately parallel to the axis, a conical bottom surface that is continuous with the cylindrical surface and tapers rearward, and a ball receiving seat on the bottom surface of which the curved surface of the writing ball is transferred. The diameter of the writing ball is H, and the distance that the writing ball projects from the tip of the holder is I. 2. The thermochromic writing instrument of claim 1, wherein the clearance is (0.05 × H)≦K≦(0.1 × H), and the writing ball is held in the crimped portion so that (J + K)<(0.4 × H), where J is the ball projection dimension, K is the clearance that is the amount by which the writing ball can move within the holder in the axial direction of the ballpoint pen tip, L is the inner diameter of the cylindrical surface of the ball house, A is the inner diameter of the ink guide hole, F is the outermost diameter of the ball seat, G is the wire diameter of the biasing portion, and C is the diameter of the circumscribing circle of the ink groove. 3. The thermochromic writing instrument of claim 1, wherein the clearance is (0.05 × H)≦K≦(0.1 × H), the writing ball is held in the crimped portion so that (J + K)<(0.4 × H), the inner diameter of the cylindrical surface of the ball house is formed so that L≧(H × 1.05) and F<(0.65 × H), the ink guide hole is formed so that A≦(0.6 × H), and the diameter of the circumscribing circle of the ink groove is formed so that C > H.