JP7679235B2 - Ink refill - Google Patents

Description

The present invention relates to an ink refill that is attached to a ballpoint pen.

Some ballpoint pen tips used as the writing tip of a ballpoint pen are formed by cutting a cylindrical metal material. In such ballpoint pen tips, after a writing ball is inserted into the ball house formed inside the tip, the tip edge has a crimped portion that is pressed inward to hold the ball in place.

On the other hand, when the writing tip is held facing down, gravity causes the ink to drop and leak out from the writing tip, a phenomenon known as "direct current." In particular, in ballpoint pens equipped with a crimped part as described above, if the writing angle relative to the writing surface is shallow, the shoulder of the crimped part may come into contact with the paper surface, causing the inner circumference of the crimped part to deform. If this deformation causes a gap between the ball and the crimped part, direct current is likely to occur while the writing tip is held facing down. Other problems include a deterioration in the quality of the drawn line.

As shown in Patent Document 1, a ballpoint pen tip and ink refill using the same are disclosed that can prevent direct current caused by deformation of the inner circumference of the crimped part by preventing the shoulder of the crimped part from contacting the paper surface when writing.

JP 2008-55854 A

However, in the invention described in Patent Document 1, when the writing angle with respect to the writing surface is small, the first shoulder portion comes into contact with the writing surface, resulting in a poor writing feel. Therefore, the object of the embodiment of the present application is to provide a ballpoint pen tip and ink refill that suppresses the deterioration of the writing feel and has little effect on the inner circumference of the crimped portion.

(1) First embodiment In view of the above problems, the ink refill of the first embodiment of the present application is as follows:
A holder and
a first tapered surface having an outer periphery at a tip end of the holder that is tapered;
a connecting surface formed on a tip side of the first tapered surface, the connecting surface having an angle of greater than 180° measured on the outside relative to the first tapered surface in a virtual cross section including an axis of the holder;
a first shoulder portion which is a boundary between the first tapered surface and the connecting surface;
a second tapered surface formed on the tip side of the connecting surface, the second tapered surface having an angle of less than 180° measured on the outside relative to the connecting surface in the imaginary cross section;
a ball house formed as an internal space between the first tapered surface, the connecting surface, and the second tapered surface;
a back hole formed as an internal space extending from a rear end of the holder to a vicinity of the ball house;
an ink hole having a circular cross section penetrating between the ball house and the back hole;
a plurality of channel grooves that are equally spaced around the ink hole so as to connect the bottom surface of the ball house and the ink hole;
A writing ball housed in the ball house;
a ball seat formed on a bottom surface of the ball house by transferring a part of the curved surface of the writing ball;
a crimped portion in which a tip portion of the second tapered surface is crimped inward;
A ballpoint pen tip including a second shoulder portion that is a boundary between the second tapered surface and the crimped portion; and
The rear end of the ballpoint pen tip is attached to a front end of the ink refill, which includes an ink reservoir tube filled with ink,
In a state where the writing ball is in contact with the ball seat,
a volume A (mm ³ ) of an annular portion of the holder that is located outside a virtual tangent line between the first shoulder portion and the writing ball in the virtual cross section;
The area B (mm ² ) of the gap between the writing ball and the crimped portion as viewed from the tip,
The surface tension C of the ink (mN/m),
The Young's modulus D (GPa) of the holder, and
Between the diameter E (mm) of the writing ball,
(A x B x ¹⁰⁸ ) / (C x D x ^E5 ) < 8
The present invention is characterized in that the following relationship holds:

(2) Second embodiment In view of the above problems, the ink refill of the second embodiment of the present application has the same configuration as the first embodiment, and further has the following features: when the writing ball is in contact with the ball seat, the second shoulder is located outside a virtual tangent line between the first shoulder and the writing ball in the virtual cross section;
When the writing ball is in contact with the inner surface of the crimped portion, the second shoulder is located inside the imaginary tangent between the first shoulder and the writing ball in the imaginary cross section.

(3) Third embodiment In view of the above problems, the ink refill of the third embodiment of the present application has, in addition to the configuration of the first or second embodiment, the ink contains at least a colorant, water, and polyglycerin having a degree of polymerization of 2 or more and 6 or less as a main skeleton, and contains 0.1% by mass or more and less than 30% by mass of alkylene oxide-added glycerin ester to which 65 moles or more and less than 120 moles of alkylene oxide are added and which is ester-bonded to a carboxylic acid-containing substance, and
The ballpoint pen tip further includes a spring that is housed inside the back hole and has a tip portion formed as a pressing rod that presses the writing ball toward the tip.

The ink refill of the present invention can prevent direct current caused by deformation of the inner circumference of the crimped part, even if the shoulder of the crimped part comes into contact with the paper surface when writing, and can improve the writing feel.

FIG. 2 is a partial cross-sectional front view of an ink refill according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional front view of a ballpoint pen tip used in the ink refill of FIG. 1 . 3 is an enlarged front cross-sectional view of the tip of the ballpoint pen tip of FIG. 2, with the spring omitted. 4 is a front cross-sectional view of the ballpoint pen tip shown in Fig. 3, showing a state in which the writing ball is pressed by a spring, although the spring is omitted.

1, an ink refill 10 according to an embodiment of the present invention is composed of a ballpoint pen tip 20, a joint 14, and an ink reservoir 11. The ink reservoir 11 is a polypropylene tube, and is filled with a water-based ink 12 having a viscosity of 100 to 3,000 mPa·sec at a shear rate of 3.84 sec ^-1 at 25°C.

Figure 2 is a partial front cross-sectional view of the ballpoint pen tip 20. Also, Figure 3 is an enlarged front cross-sectional view of the tip of the ballpoint pen tip of Figure 2, and is shown as a virtual cross section including the axis 40. However, in Figure 3, the spring 36 is omitted. The ballpoint pen tip is composed of a holder 21 formed by cutting a cylindrical material made of stainless steel, a writing ball 35 housed at the tip of the holder 21, and a spring 36 housed inside the holder 21. The tip of the holder 21 is cut into a tapered, approximately conical shape to form a first tapered surface 22, and further formed on the tip side is a connecting surface 23 whose diameter is reduced inward, and a second tapered surface 24 that protrudes toward the tip side so as to further reduce the diameter from there.

The holder 21 is the main body of the ballpoint pen tip 20 excluding the writing ball 35, and is formed, for example, by cutting a cylindrical metal material such as stainless steel as in this embodiment. Alternatively, depending on the application, it may be formed by plastic deformation processing and cutting processing of a pipe material. The part cut to a tapered shape at the tip side of the holder 21 is called the first tapered surface 22. The "tip" here refers to the side of the writing tip of the ballpoint pen tip 20, and the opposite side is the "rear end." The rear end portion of the holder 21 is formed as an inserted portion 28 with a reduced outer diameter, and this part is inserted into the tip side of the fitting 14 as shown in FIG. 1.

The connecting surface 23 is a surface that reduces the diameter of the tip side of the first tapered surface 22 and connects the first tapered surface 22 and the second tapered surface 24. Here, the angle between the first tapered surface 22 and the connecting surface 23 is greater than 180° when measured on the outside in a virtual cross section including the axis 40 of the holder 21. That is, in the ballpoint pen tip 20 according to this embodiment, it is assumed that there is a cross section that includes the axis 40 of the holder 21 (this is called a "virtual cross section". Figure 3 shows this virtual cross section). Then, when measuring the angle between the line segment derived from the first tapered surface 22 and the line segment derived from the connecting surface 23 in the virtual cross section, if the angle in the substantial part of the holder is the "inside", the angle in the other "outside" (i.e., the angle on the side that is not the substantial part of the holder, angle α shown in Figure 3) is greater than 180°. Here, the boundary between the first tapered surface 22 and the connecting surface 23, i.e., the portion that forms the apex of the above-mentioned "angle α", is the first shoulder portion 26.

The second tapered surface 24 is a tapered surface that is inclined so as to protrude from the connecting surface 23 so that the tip side of the connecting surface 23 becomes further tapered. Here, the angle between the connecting surface 23 and the second tapered surface 24 is smaller than 180° when measured "outside" in the above virtual cross section (i.e., angle β shown in FIG. 3). Note that this angle β is an angle smaller than 180° and an angle at which the second tapered surface 24 becomes tapered. In other words, this angle β is an angle smaller than 180° and larger than the angle at which the second tapered surface 24 is parallel to the axis 40 of the holder 21.

The tip of the writing ball 35, which is held inside the first tapered surface 22, the connecting surface 23, and the second tapered surface 24, is exposed from the tip edge of the second tapered surface 24, and the end of the second tapered surface 24 is pressed inward to form a crimped portion 25 that has been reduced in diameter. A spring 36 formed from a coil spring is inserted inside the back hole 32, which is formed as the internal space of the holder 21. The tip of the spring 36 is formed as a push rod 37 that extends straight toward the tip.

The ball house 29 is a space formed from the tip side as a part that contacts the inner circumference of the part where the first tapered surface 22, the connecting surface 23, and the second tapered surface 24 are located, and the writing ball 35 is inserted into this space. When the holder 21 is made of a cylindrical material as in this embodiment, the ball house 29 is formed by cutting from the tip, but when the holder 21 is made of a pipe material, the ball house 29 is formed by using the internal space from the outer circumference up to the part that has been pressed and deformed by punching, or by cutting to slightly expand the inner diameter. The bottom surface 30 of the ball house 29 has a funnel-like shape.

As shown in FIG. 1, the back hole 32 is a central hole that reaches from the rear end of the holder 21 to a position close to but not reaching the ball house 29 (see FIG. 3). When the holder 21 is made of a cylindrical material as in this embodiment, the back hole 32 is formed by cutting, but when the holder 21 is made of a pipe material, the internal space from the rear end to the ball house 29 becomes the back hole 32 as it is. The ink 12 contained in the ink containing tube 11 is guided through this hole to the ball house 29.

The ball house 29 and the back hole 32 are connected by an ink hole 33, which is a circular hole with a smaller diameter than the back hole 32. A plurality of channel grooves 34 (four in this embodiment), which are axial grooves, are evenly arranged around the ink hole 33. When the holder 21 is made of a cylindrical material as in this embodiment, the channel grooves 34 are formed by cutting the bottom surface 30 of the ball house 29 with a channel tool. When the holder 21 is made of a pipe material, the gap between the areas that are pressed and deformed by the punching process when forming the ball house 29 is used as the channel grooves 34.

The ink 12 guided to the tip of the back hole 32 travels from the ink hole 33 through this channel groove 34 to the ball house 29. That is, the channel groove 34 connects the ball house 29, the bottom surface 30 of which is blocked by the writing ball 35, to the ink hole 33. If the ink 12 used is relatively highly viscous and unlikely to cause a direct current, it is desirable for the channel groove 34 to extend all the way to the back hole 32 from the viewpoint of the flow of the ink 12. On the other hand, if the ink 12 used is relatively low viscous and prone to cause a direct current, it is desirable for the channel groove 34 not to extend all the way to the back hole 32, but to stop midway at the ink hole 33, as shown in FIG. 3.

Here, the writing ball 35 is a metallic sphere made of ultra-hard stainless steel or the like, and is inserted into the ball house 29. The ink that reaches the ball house 29 adheres to the surface of the writing ball 35 and is transferred to the writing surface.

The writing ball 35 inserted into the ball house 29 is pressed backwards by a process known as "pounding," and part of the curved surface of the writing ball 35 is transferred to the bottom surface 30 of the ball house 29, creating a concave curved surface that serves as the ball seat 31.

Furthermore, after the writing ball 35 is inserted into the ball house 29 and subjected to the above-mentioned hammering process, the end of the second tapered surface 24 is crimped inward to reduce the inside diameter, forming the crimped portion 25. This crimped portion 25 is structured to hold the writing ball 35 and prevent it from falling. The boundary between this crimped portion 25 and the second tapered surface 24 is the second shoulder portion 27.

The ballpoint pen tip 20 shown in Figure 2 is attached to the tip of an ink reservoir tube 11 made of synthetic resin via the joint 14 with its inserted portion 28 inserted into the joint 14 to form an ink refill 10 (see Figure 1). Water-based gel ink is injected into the ink reservoir tube 11 of the ink refill 10 as the ink 12, and a grease-like ink follower 13 is injected into the rear end of the ink 12 to prevent the ink 12 from leaking out from the rear end.

In addition to the above structure, if it is further assumed that there is a tangent between the writing ball and the first shoulder portion in the imaginary cross section (this is referred to as a “virtual tangent”),
(A x B x ¹⁰⁸ ) / (C x D x ^E5 ) < 8
Here, "A" is the volume (unit: mm ³ ) of the annular portion located outside the imaginary tangent between the first shoulder portion and the writing ball in the imaginary cross section, "B" is the area (unit: mm ² ) of the gap between the writing ball and the crimped portion as viewed from the tip, "C" is the surface tension (unit: mN/m) of the ink, "D" is the longitudinal elastic modulus (Young's modulus) of the holder (unit: GPa), and "E" is the diameter (unit: mm) of the writing ball.

As shown in FIG. 3, when the writing ball 35 is in contact with the ball seat 31, the second shoulder 27 is located outside the imaginary tangent 41 between the first shoulder 26 and the writing ball 35 in the imaginary cross section. The above volume A is specifically the portion including the second shoulder 27, and is the volume of the annular portion obtained by rotating the triangular area indicated by "A" in FIG. 3 around the axis 40. Since this portion is located outside the imaginary tangent, when the writing angle with respect to the paper surface is small, the portion near the second shoulder 27 will hit the paper surface before the first shoulder 26.

The first tapered surface 22 and the connecting surface 23 in front of and behind the first shoulder 26 are formed by cutting, and therefore have a relatively large surface roughness. In contrast, the crimped portion 25 on the tip side of the second shoulder 27 is formed by plastic deformation, and is machined to be smoother and closer to a mirror surface than the vicinity of the first shoulder 26. Therefore, compared to when the second shoulder 27 is located inside the imaginary tangent, when the writing angle is small, the writing surface comes into contact with the smooth second shoulder 27 before coming into contact with the rough first shoulder 26, resulting in a smoother writing feel.

If the ratio of volume A to the volume of the writing ball 35 is less than 1%, the smooth writing feel caused by the second shoulder 27 contacting the writing surface before the first shoulder 26 due to wear caused by writing will be quickly lost. On the other hand, if it is 15% or more, the feeling of the second shoulder 27 catching when writing will actually become greater. Therefore, in order to obtain the effect of the present invention of a smooth writing feel as described above, it is preferable that the ratio of volume A to the volume of the writing ball is 1% to 15%.

If the above-mentioned area B is less than 5% of the cross-sectional area of the writing ball 35, the written line will be thin, while if it is 15% or more, the effect of preventing direct current will not be sufficient. Therefore, it is preferable that the ratio of area B to the cross-sectional area of the writing ball 35 is 5% or more and less than 15%.

The holder 21 is preferably made of a non-lead metal material. If the Young's modulus D of the holder 21 made of this material is less than 190 GPa, which is in the plastic region of the metal material, plastic deformation occurs when the writing tip is subjected to an impact due to being dropped, etc., and elastic recovery is unlikely to occur. On the other hand, if the Young's modulus D is 210 GPa or more, it is difficult to process the metal material into the holder 21. Therefore, it is preferable that the Young's modulus D of the holder 21 is 190 GPa or more and less than 210 GPa.

The arithmetic mean surface height Sa of the crimped portion 25 is preferably 10 nm or less. The projection dimension from the end face of the crimped portion 25 to the tip of the writing ball 35 is preferably 30% or more of the diameter of the writing ball 35. A seal surface 25a is formed on the inner surface of the crimped portion 25 along the writing ball 35 to make the ball house airtight. The axial length C of the seal surface 25a is preferably 5 μm or more and less than 30 μm.

In addition, the pressure rod 37 of the spring 36 that biases the writing ball 35 toward the tip is omitted in FIG. 3, but FIG. 3 shows the state in which the writing ball 35 is pressed toward the rear end by the writing surface during writing and is in contact with the ball seat 31. In contrast, when not writing, as shown in FIG. 4, the writing ball 35 is pressed toward the tip by the pressure rod 37 of the spring 36, which is also omitted from the illustration, and is in contact with the inner surface of the crimped portion 25, i.e., the seal surface 25a. This isolates the ball house 29 from the outside, preventing direct current. In this state, the second shoulder 27 is located inside the imaginary tangent 42 between the first shoulder 26 and the writing ball 35 in an imaginary cross section including the axis 40 (see FIG. 3).

In the ink 12 of this embodiment, the ink contains at least a colorant and water, and contains 0.1% by mass or more and less than 30% by mass of alkylene oxide-added glycerin ester, which has a main skeleton of polyglycerin with a degree of polymerization of 2 or more and 6 or less, has 65 moles or more and 120 moles or less of alkylene oxide added thereto, and is ester-bonded to a carboxylic acid-containing substance.

The alkylene oxide-added glycerin ester used in the embodiment is contained in order to improve the writing feel, non-bleeding and line drying properties, without causing any change in the ink properties over time even during long-term storage, and is a polyglycerin having a main skeleton with a degree of polymerization of 2 to 6, with 65 to 120 moles of alkylene oxide added thereto and ester-bonded to a carboxylic acid-containing substance. This alkylene oxide-added glycerin ester is obtained by reacting a polyglycerin having a degree of polymerization of 2 to 6 with 65 to 120 moles of alkylene oxide and a carboxylic acid-containing substance.

In an embodiment, the degree of polymerization of the polyglycerin used, which is the glycerin skeleton, is preferably 2 or more and 6 or less. If the degree of polymerization exceeds 6, the bulkiness of the entire molecule increases, improving the writing feel and the non-bleeding properties of the drawn lines, but it will not dry, resulting in problems such as dirtying the hands.

In the embodiment, the alkylene oxide used may be at least one of ethylene oxide, propylene oxide, butylene oxide, etc. (each alone or in combination of two or more, the same applies below), and preferably ethylene oxide is preferable from the viewpoint of the hydrophilicity of the alkylene oxide. The number of moles added of this alkylene oxide is preferably 65 to 120 moles. If the number of moles added is less than 65 moles, the non-bleeding property decreases and the swelling degree of the paper surface is low, so that a dramatic improvement in the writing feel cannot be expected, and when used in a pigment ink, the dispersibility decreases. On the other hand, if the number of moles added exceeds 120 moles, the ink viscosity increases, and therefore, especially when designing a low-viscosity ink, the content must be reduced, and the desired writing feel and non-bleeding property cannot be achieved. Furthermore, when used in a pigment ink, in order to ensure the content required for pigment dispersion stability, an increase in the ink viscosity is unavoidable, and as a result, the content is reduced, and dispersion stability cannot be ensured. Furthermore, when imparting shear thinning properties to an ink, there is more leeway in terms of viscosity than with low-viscosity inks, but the viscosity before the viscosity imparting agent is added is higher, which results in a reduction in the amount of viscosity imparting agent contained, and particularly when the viscosity imparting agent is added to a pigment ink, this can cause the pigment to settle over time.

In the embodiment, the carboxylic acid-containing substance used may be, for example, at least one of fatty acids, aromatic carboxylic acids, etc. The fatty acid used may be either linear or branched, or saturated or unsaturated, and from the viewpoint of further improving the effects of the embodiment, fatty acids having 4 to 25 carbon atoms are preferred, and fatty acids having 8 to 20 carbon atoms are more preferred, such as capric acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, oleic acid, etc.
Examples of aromatic carboxylic acids include benzoic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, 1,4-naphthalene dicarboxylic acid, and 2,6-naphthalene dicarboxylic acid, and these may have a substituent such as an alkyl group, a halogen group, or an alkoxy group.

Fatty acids with less than 4 carbon atoms tend to have a relatively high hydrophilicity in the molecule, which can lead to poor line drying, and when contained in a pigment ink, can lead to poor pigment dispersibility due to a reduced pigment adsorption capacity. On the other hand, fatty acids with more than 25 carbon atoms tend to increase the ink viscosity, similar to the number of moles of alkylene oxide added, which places restrictions on ink viscosity design.

In the alkylene oxide-added glycerin ester of the embodiment, it is preferable that, from the viewpoints of the hydrophilicity of the molecule, the pigment adsorption in the case of a pigment ink, and the ink viscosity design, when the number of moles of the carboxylic acid-containing substance is X and the degree of polymerization of glycerin is Y, X/[Y+2], i.e., the degree of esterification (number of esters/number of hydroxyl groups), is 0.30 to 0.60.

As described above, the alkylene oxide-added glycerin ester of the embodiment is produced by reacting polyglycerin having a degree of polymerization of 2 to 6 with 65 to 120 moles of alkylene oxide and a carboxylic acid-containing substance, so that the main skeleton is made of glycerin, 65 to 20 moles of alkylene oxide are added, and the ester bond is formed with the carboxylic acid-containing substance. The HLB of the glycerin ester is preferably 16 to 20.

If the HLB is less than 16, the number of moles of alkylene oxide added will be small and the number of moles of alkyl and aromatic groups added will tend to be large, resulting in a poor writing feel and, when used in pigment inks, a decrease in dispersion stability. On the other hand, if the HLB is more than 20, the number of moles of alkylene oxide added will tend to be large, resulting in an increase in ink viscosity, which will place restrictions on ink viscosity design.

The average molecular weight of the alkylene oxide-added glycerin ester in the embodiment is preferably 3000 to 9000. If the average molecular weight is less than 3000, the line drying will be reduced due to a lack of hydrophobic groups, which are the components that penetrate the paper surface, and the pigment dispersibility will be poor in pigment inks. On the other hand, if the average molecular weight exceeds 9000, the ink viscosity will increase, resulting in restrictions on ink viscosity design.

In the embodiment, the content of the alkylene oxide-added glycerin ester is desirably 1 to 10% by mass relative to the total amount of the ink composition. If the content is less than 1% by mass, the writing feel cannot be improved, while if it exceeds 10% by mass, in the case of Newtonian ink, the viscosity becomes too high and the target viscosity cannot be set. In addition, in the case of non-Newtonian ink, when setting the target viscosity, it is necessary to limit the content of the non-Newtonian agent, which results in a weak network structure and problems such as pigment sedimentation.

As the colorant used in the embodiment, any one of inorganic and organic pigments, water-soluble dyes, and oil-soluble dyes that dissolve in water at low concentrations can be used. When an oil-soluble dye is used, the solubility of the dye can be improved by dissolving an organic solvent in the vehicle. Examples of inorganic pigments include titanium oxide, carbon black, and metal powder, and examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, and nitroso pigments. As the water-soluble dyes, any of direct dyes, acid dyes, food dyes, and basic dyes can be used.

It is desirable that the content of these colorants be in the range of 1 to 15% by mass of the total composition of the ink 12. If the content of these colorants exceeds 15% by mass, the pigments may aggregate or the dyes may precipitate, clogging the pen tip and causing poor writing results when stored for a long period of time. Also, if the content is less than 1% by mass, the coloring will be weak and the hue will be difficult to discern when written on paper, which is undesirable.

Regarding the pH of ink 12 in this embodiment, it is preferable to adjust the pH of the ink composition to a range of 7 to 10 (measurement temperature: 25°C, measuring device: Horiba pH meter). The pH of ink 12 is adjusted to the above range to prevent rust when the ballpoint pen tip is made of a metal material, as well as to prevent aggregation of the dispersant used to disperse the pigment and the acid dye used as a colorant from remaining undissolved.

The ink 12 of the embodiment can be used in a wide range of viscosities. In the case of low-viscosity inks, such as inks with a Newtonian viscosity of 1 to 10 mPa·s, effects are seen in terms of non-bleeding and writing feel. Effects similar to those of low-viscosity inks can be expected for inks with a viscosity of about 10 to 100 mPa·s. In the case of non-Newtonian viscosity inks, when the ink viscosity at a shear rate of 3.84 ^s-1 is about 100 to 4000 mPa·s, a strong network structure can be constructed with the non-Newtonian agent, and physical property stability can be achieved.

The surface tension of the ink 12 is preferably set in the range of 30 to 40 mN/m (measurement temperature: 25°C, measurement equipment: surface tension meter manufactured by Kyowa Interface Science Co., Ltd.). If the surface tension of the ink 12 falls below the above ranges (below the minimum value of each range), the written lines may be prone to bleeding, or direct currents or blowing may occur, while if the surface tension exceeds the above preferred ranges, the writing feel of the pen and the flow rate stability may deteriorate.

In the ink 12 of the embodiment, a water-soluble organic solvent can be used as a moisturizer to prevent the writing tip from drying out, if necessary. Derivatives of glycerin, diglycerin, polyglycerin, etc. can be contained in the ink in order to obtain an effect similar to that of organic solvents through their moisturizing effect. The content of these water-soluble organic solvents is preferably in the range of 5 to 40% by mass of the total composition of the ink 12. If the content of this water-soluble organic solvent exceeds 40% by mass, the drawn lines will be difficult to dry, which is not preferable.

In addition, in the ink 12 of the embodiment, sugars, urea derivatives, etc. can be used as necessary as a humectant to prevent the writing tip from drying out. The humectants may be used alone or in combination of two or more types.

The content of these humectants, such as sugars and urea derivatives, is preferably 0.25 to 10% by mass of the total ink composition. If the content of this humectant is less than 0.25% by mass, it will not be effective as a humectant, while if it exceeds 10% by mass, it will increase the ink viscosity and reduce the drying time of the drawn lines.

In addition to the above, the ink 12 of the embodiment may contain lubricants, preservatives, pH adjusters, water-soluble alkali-soluble resins, resin emulsions, corrosion inhibitors, antioxidants, and thickeners as necessary, with the remainder being adjusted to water (ion-exchanged water, purified water, distilled water, pure water, ultrapure water, etc.).

Examples of lubricants include fatty acid salts such as potassium linoleate, sodium ricinoleate, potassium oleate, and sodium oleate, as well as the nonionic, anionic, and amphoteric surfactants shown below. In particular, in the case of low-viscosity inks (about 10 mPa·s), the content of these is preferably 0.01 to 2.0% by mass, more preferably 0.05 to 1.5% by mass, and particularly preferably 0.1 to 1.2% by mass, based on the total amount of the ink composition, from the viewpoint of non-bleeding. In the case of inks with non-Newtonian viscosity of 100 to 4000 mPa·s (at a shear rate of 3.84 s ^-1 ), the content does not need to be limited due to the viscosity effect.

Examples of preservatives include phenol, isopropylmethylphenol, sodium pentachlorophenol, benzoic acid, sodium benzoate, dehydroacetic acid, sodium dehydroacetate, sorbic acid, potassium sorbate, 2-pyridinthiol-1-oxide sodium salt, 1,2-benzisothiazon-3-one, 5-chloro-2-methyl-4-isothiazon-3-one, 2,4-thiazoline benzimidazole, and paraoxybenzoic acid esters.

Examples of pH regulators include amines or bases, such as various organic amines such as aminotriethanolamine, monoethanolamine, and diethanolamine, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide, and ammonia.

Water-soluble alkali-soluble resins or resin emulsions are contained mainly in the hope of acting as viscosity adjusters and water-resistant agents, and examples thereof include polyvinyl chloride, polyvinylidene chloride, polystyrene, polyethylene, polycarbonate, polymethyl methacrylate, benzoguanamine resin, styrene-acrylotryl copolymers, modified acrylic methyl methacrylate-styrene copolymers, acrylic acid alkyl ester copolymers, acrylonitrile-acrylic acid alkyl ester copolymers, styrene-acrylic acid alkyl ester copolymers, styrene-methacrylic acid alkyl ester-acrylic acid alkyl ester copolymers, styrene-acrylonitrile-methacrylic acid alkyl ester-acrylic acid alkyl ester copolymers, methacrylic acid alkyl ester-acrylic acid alkyl ester copolymers, acrylic acid-methacrylic acid-acrylic acid alkyl ester copolymers, methacrylic acid alkyl ester-acrylic acid alkyl ester copolymers, acrylic acid-methacrylic acid-acrylic acid alkyl ester copolymers, vinylidene chloride-acrylic acid alkyl ester copolymers, etc.

The antioxidant is used mainly to suppress the hydrolysis of the ester compound of the embodiment and to eliminate problems caused by gas expansion inside a writing instrument such as a ballpoint pen barrel. Specific examples include at least one of sodium L-ascorbate, sodium erythorbate, vinylpyrrolidone oligomer, polyphenols such as tocophenol, catechin, flavangenol, BHT (dibutylhydroxytoluene), BHA (butylhydroxyanisole), and acetylcysteine.

Thickeners are broadly classified into organic and inorganic thickeners. Examples of organic thickeners include acrylic synthetic polymers, natural gums, cellulose, and polysaccharides. Specific examples include gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, casein gum, welan gum, succinoglycan, alcalan, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium starch glycolate, propylene glycol alginate, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, sodium polyacrylate, carboxyvinyl polymer, polyethylene oxide, copolymers of vinyl acetate and polyvinylpyrrolidone, crosslinked acrylic acid polymers, acrylic swelling associative emulsions, and salts of styrene-acrylic acid copolymers. Examples of inorganic thickeners include clays such as smectite, bentonite, and diatomaceous earth, and fine particles such as silicon dioxide. The amount of these thickeners added can be adjusted according to the viscosity of the ink.

Examples of corrosion inhibitors include tolyltriazole, benzotriazole and its derivatives, fatty acid phosphorus derivatives such as octyl phosphate and dioctyl thiophosphate, imidazole, benzimidazole and its derivatives, 2-mercaptobenzothiazole, octyl methanesulfonic acid, dicyclohexylammonium nitrite, diisopropylammonium nitrite, propargyl alcohol, and dialkylthiourea.

As an example, ink refills using two types of ink were evaluated using a direct current test and a sensory test for the feeling of adhesion.

(1) Ink 1
Ink 1 had the following composition:
Color material (water black): 5% by mass
Solvent (ethylene glycol): 20% by mass
pH adjuster (triethanolamine): 0.3% by mass
pH adjuster (aminomethylpropanol): 0.1% by mass
Preservative (2-benzisothiazolin-3-one): 0.1% by mass
Rust inhibitor (benzotriazole): 0.3% by mass
Thickener (xanthan gum): 0.4% by mass
Sugars (glucose): 2% by mass
Acetylene oxide-added glycerin ester (molecular weight 5043, HLB 18): 3% by mass
Purified water: remainder

The viscosity of ink 1 having the above composition was measured at a measurement temperature of 25°C using an ELD-EMD viscometer (Tokimec) as a measuring instrument, and was 1500 mPa·s at a rotation speed of 1 rpm and 230 mPa·s at a rotation speed of 50 rpm. The pH of ink 1 was measured at 25°C using a pH measuring instrument (Horiba) and was 8.5. Furthermore, the surface tension (C) of ink 1 was 32 mN/m.

This ink 1 was filled into the ink reservoir of an ink refill as shown in Figure 1. The ballpoint pen tip attached to the end of the ink reservoir was a holder made of stainless steel that contained a writing ball with a ball diameter (E) of 0.7 mm. The Young's modulus (D) of this holder was 200 GPa. The pressing load of the spring pressing the writing ball was an average of 15 g force (0.15 N).

Ink refills using this ink 1 were created in Examples 1 to 4 and Comparative Examples 1 to 3 shown in Table 1 below.

(2) Ink 2
Ink 2 had the following composition:
Color material (carbon black): 7% by mass
Solvent (ethylene glycol): 10% by mass
Solvent (propylene glycol): 15% by mass
pH adjuster (triethanolamine): 0.3% by mass
pH adjuster (aminomethylpropanol): 0.1% by mass
Preservative (2-benzisothiazolin-3-one): 0.1% by mass
Rust inhibitor (benzotriazole): 0.1% by mass
Urea: 1.5% by mass
Acetylene oxide-added glycerin ester (molecular weight 5095, HLB 17.8): 1% by mass
Purified water: remainder

The viscosity of ink 2 having the above composition was measured at a measurement temperature of 25°C in the same manner as ink 1, and was 3.8 mPa·s at a rotation speed of 50 rpm. The pH of ink 2 was also measured in the same manner as ink 1, and was 8.5. Furthermore, the surface tension (C) of ink 2 was 38 mN/m.

This ink 2 was filled into the ink reservoir of an ink refill as shown in Figure 1. The ballpoint pen tip attached to the end of the ink reservoir was a holder made of stainless steel that contained a writing ball with a ball diameter (E) of 0.5 mm. The Young's modulus (D) of this holder was 193 GPa. The pressing load of the spring pressing the writing ball was an average of 15 g force (0.15 N).

Ink refills using this ink 2 were created in Examples 5 to 10 and Comparative Examples 5 and 6 shown in Table 2 below.

(3) Test Method (3-1) DC Test In an environment of 23±2°C temperature and 65±10% relative humidity, the writing tip was extended from the tip of the ballpoint pen shaft equipped with the ink refill of each Example or Comparative Example, and the writing tip was dropped downward from a height of 1 m onto a receiving plate inclined at 50° to the horizontal plane. After that, five circles of about 20 to 25 cm were written freehand, and the pen was immediately fixed facing downward and left for 60 minutes. After that, the size of the ink droplets accumulated at the tip of the ballpoint pen tip was measured. The evaluation criteria are as follows.
Evaluation A: No ink droplets were generated. Evaluation B: The size of the ink droplets was greater than 0 mm and less than 1 mm. Evaluation C: The size of the ink droplets was greater than 1 mm and less than 2 mm. Evaluation D: The size of the ink droplets was greater than 2 mm.

(3-2) Gripping Feeling Test Subjects were asked to write freely with a ballpoint pen equipped with an ink refill of each Example or Comparative Example, while keeping the writing angle at approximately 45°. The grabbing feeling at that time was sensorily evaluated as shown below.
Rating A: No sticking sensation at all Rating B: Slight sticking sensation Rating C: Some sticking sensation Rating D: Significant sticking sensation

(4) Test Results The evaluation results for ink 1 are shown in Table 1 below, and the evaluation results for ink 2 are shown in Table 2 below. In each table, "A" is the volume A (see FIG. 3) of the annular portion of holder 21 that is outside the imaginary tangent 41 between first shoulder portion 26 and writing ball 35 in an imaginary cross section including axis 40, in ^mm3 . In each table, "B" is the area B (see FIG. 3) of the gap between writing ball 35 and crimped portion 25 as viewed from the tip, in ^mm2 . In each table, "F" is a value calculated by the following formula using the above parameters A to E.
F=(A×B×10 ⁸ )/(C×D×E ⁵ )

As can be seen from Tables 1 and 2 above, the evaluation results for the feeling of grip for both the Examples and Comparative Examples were highly rated as "A."

The F value exceeded 8 in Comparative Examples 1 to 4, which used Ink 1, and Comparative Examples 5 and 6, which used Ink 2. As a result, the DC test was rated as "C" for Comparative Examples 1, 4, and 6, which were the best, and "D" for the other comparative examples, which were poor results.

On the other hand, the F values of Examples 1 to 4 using Ink 1 and Examples 5 to 10 using Ink 2 were all below 8. Accordingly, the DC test was rated at best "B" (Examples 1, 5 and 9), while the other Examples were rated "A", which was an excellent result.

The above formula for calculating the F value shows that the larger the A and B values are, the larger the F value is, and therefore the DC test tends to be poorer, as shown in Tables 1 and 2 above. This is thought to be because when the thickness of the crimped portion including "A" in Figure 3 is large, it becomes difficult to restore the deformation when the writing tip hits, making it easier for DC to occur afterwards. In contrast, when the thickness of the crimped portion is small, the first shoulder portion 26 (see Figure 3) is more likely to hit, so deformation of the crimped portion is less likely to occur, and it is thought that there is less of an adverse effect on the DC.

The present invention can be used for ink refills for ballpoint pens.

REFERENCE SIGNS LIST 10 ink refill 11 ink reservoir tube 12 ink 14 joint 20 ballpoint pen tip 21 holder 22 first tapered surface 23 connecting surface 24 second tapered surface 25 crimped portion 25a sealing surface 26 first shoulder portion 27 second shoulder portion 28 inserted portion 29 ball house 30 bottom surface 31 ball seat 32 back hole 33 ink hole 34 channel groove 35 writing ball 36 spring 37 pressure rod 40 shaft center 41 imaginary tangent 42 imaginary tangent

Claims (3)

A holder and
a first tapered surface having an outer periphery at a tip end of the holder that is tapered;
a connecting surface formed on a tip side of the first tapered surface, the connecting surface having an angle of greater than 180° measured on the outside relative to the first tapered surface in a virtual cross section including an axis of the holder;
a first shoulder portion which is a boundary between the first tapered surface and the connecting surface;
a second tapered surface formed on the tip side of the connecting surface, the second tapered surface having an angle of less than 180° measured on the outside relative to the connecting surface in the imaginary cross section;
a ball house formed as an internal space between the first tapered surface, the connecting surface, and the second tapered surface;
a back hole formed as an internal space extending from a rear end of the holder to a vicinity of the ball house;
an ink hole having a circular cross section penetrating between the ball house and the back hole;
a plurality of channel grooves that are equally spaced around the ink hole so as to connect the bottom surface of the ball house and the ink hole;
A writing ball housed in the ball house;
a ball seat formed on a bottom surface of the ball house by transferring a part of the curved surface of the writing ball;
a crimped portion in which a tip portion of the second tapered surface is crimped inward;
A ballpoint pen tip including a second shoulder portion that is a boundary between the second tapered surface and the crimped portion; and
The rear end of the ballpoint pen tip is attached to a front end of the ink refill, which includes an ink reservoir tube filled with ink,
In a state where the writing ball is in contact with the ball seat,
a volume A (mm ³ ) of an annular portion of the holder that is located outside a virtual tangent line between the first shoulder portion and the writing ball in the virtual cross section;
The area B (mm ² ) of the gap between the writing ball and the crimped portion as viewed from the tip,
The surface tension C of the ink (mN/m),
The Young's modulus D (GPa) of the holder, and
Between the diameter E (mm) of the writing ball,
(A x B x ¹⁰⁸ ) / (C x D x ^E5 ) < 8
An ink refill characterized in that the following relationship holds: When the writing ball is in contact with the ball seat, the second shoulder is located outside a virtual tangent line between the first shoulder and the writing ball in the virtual cross section,
2. The ink refill according to claim 1, characterized in that, when the writing ball is in contact with the inner surface of the crimped portion, the second shoulder is located inside a virtual tangent between the first shoulder and the writing ball in the virtual cross section. The ink contains at least a colorant, water, and polyglycerin having a degree of polymerization of 2 or more and 6 or less as a main skeleton, and contains 0.1% by mass or more and less than 30% by mass of alkylene oxide-added glycerin ester to which 65 moles or more and 120 moles or less of alkylene oxide are added and which is ester-bonded to a carboxylic acid-containing substance,
3. The ink refill according to claim 1, wherein the ballpoint pen tip further comprises a spring housed inside the back hole and having a tip portion formed as a pressing rod for pressing the writing ball toward the tip.