JP7824813B2 - Ink reservoir and writing implement equipped with ink reservoir - Google Patents

Description

The present invention relates to an ink reservoir that contains writing ink and a writing instrument equipped with this ink reservoir.

Ballpoint pens, fountain pens, markers, and other writing instruments often come equipped with an ink reservoir that contains writing ink. Known types of ink reservoir include metal and resin reservoirs. Metal reservoirs have excellent gas barrier properties, but are not translucent, meaning the ink inside cannot be seen from the outside. In other words, they lack ink visibility. Without ink visibility, it is impossible to check how much ink is remaining, leading to problems such as suddenly running out of ink and being unable to write.

On the other hand, resin ink reservoirs can maintain ink visibility by using a translucent resin material, but they have poor gas barrier properties. Poor gas barrier properties can cause the ink to evaporate or deteriorate, resulting in issues with the ink's stability over time and the writing performance of writing instruments equipped with the ink reservoir.

In order to improve the gas barrier properties of such resin ink reservoir cylinders, ink reservoir cylinders have been proposed that have a multi-layered resin structure, with at least one layer formed from an ethylene-vinyl alcohol copolymer resin (see, for example, Patent Document 1). The ink reservoir cylinder described in Patent Document 1 has improved gas barrier properties compared to conventional resin ink reservoir cylinders due to the ethylene-vinyl alcohol copolymer resin layer.

JP 2002-307890 A

However, because the layer proposed in Patent Document 1 to improve gas barrier properties is merely a resin layer, there are natural limits to how much gas barrier properties can be improved, and the gas barrier properties do not reach a level sufficient for practical use.

The object of the present invention is to solve the above problems by providing an ink reservoir that has excellent gas barrier properties and ink visibility, as well as a writing instrument equipped with this ink reservoir.

An ink reservoir according to one embodiment of the present invention comprises:
an interior region for containing ink for the writing instrument;
The ink container is made of a ceramic material having a translucency sufficient to allow the ink contained in the internal region to be visible from the outside.

A writing instrument according to one embodiment of the present invention is a writing instrument equipped with the ink reservoir tube described above.

As described above, the present invention provides an ink reservoir that has excellent gas barrier properties and ink visibility, as well as a writing instrument equipped with this ink reservoir.

10 is a graph showing the results of measuring the contact angle of each sample, which is made of alumina and has different surface roughness. 1 is a side cross-sectional view that schematically shows a writing instrument that includes an ink reservoir according to one embodiment of the present invention that functions as a refill for a ballpoint pen. FIG. 10 is a side cross-sectional view schematically showing a writing instrument having an ink reservoir according to another embodiment of the present invention, which functions as a refill for a ballpoint pen.

Next, specific embodiments of the present invention will be described in detail with reference to the drawings. In each figure, corresponding components having the same function are assigned the same reference numerals.

(Outline of ink reservoir according to embodiment)
Ink reservoirs containing writing ink are widely used in oil-based ballpoint pens and oil-based markers that use oil-based ink, water-based ballpoint pens and water-based markers that use water-based ink, and even fountain pens. Such ink reservoirs are often made of metal or resin. Metal ink reservoirs have excellent gas barrier properties, but are not translucent and therefore do not allow the ink to be seen. Without ink visibility, it is not possible to check the remaining ink level, which can lead to problems such as suddenly running out of ink and being unable to write.

On the other hand, resin ink reservoirs can maintain ink visibility by using translucent resin materials, but as mentioned above, ink reservoirs with excellent gas barrier properties have not yet been developed. Poor gas barrier properties can cause ink evaporation and deterioration, resulting in issues with the ink's stability over time and the writing performance of writing instruments equipped with the ink reservoir.

The inventors discovered that by forming the ink reservoir from a translucent ceramic material, it is possible to achieve an ink reservoir that has both excellent gas barrier properties and ink visibility. It is clear that the use of a ceramic material can impart excellent gas barrier properties to the ink reservoir.

Furthermore, it has been found that by employing an appropriate ceramic material and manufacturing method, it is possible to make the ink contained in the internal region of the ink reservoir visible from the outside. In other words, it has been found that it is possible to impart a level of ink visibility sufficient for practical use to the ink reservoir. For example, as will be described later, by using alumina (Al ₂ O ₃ ) as the ceramic material and subjecting the molded product to hot isostatic pressing, it is possible to manufacture a ceramic ink reservoir having sufficient translucency for practical use.

The table below compares the properties of ink reservoir tubes made from translucent ceramic material, non-translucent ceramic material, metal material, and transparent resin material.

As shown in Table 1 above, metal materials and general ceramic materials that do not have translucency have excellent gas barrier properties but do not allow ink visibility. On the other hand, transparent resin materials allow ink visibility but have poor gas barrier properties. The only material that provides excellent gas barrier properties and ink visibility is the ink reservoir tube made from a translucent ceramic material, as in this embodiment.

The ink reservoir of this embodiment has excellent gas barrier properties, making it less susceptible to ink evaporation and deterioration, and also provides excellent ink stability over time and writing performance for writing instruments equipped with the ink reservoir. Additionally, the ink is highly visible, making it easy to check the remaining ink level from the outside, preventing problems such as sudden ink shortages.

As described above, this embodiment provides an ink reservoir tube that has excellent gas barrier properties and ink visibility.

In particular, when the ceramic material is alumina, it is possible to provide an ink reservoir with excellent ink visibility.

In addition, because it does not use resin materials, it complies with the SDGs (Sustainable Development Goals) and can particularly contribute to environmental conservation and the prevention of global warming. Furthermore, because the ink inside can be seen all around, it is easier and more reliable to determine the amount of ink remaining than, for example, when a gas barrier promoting film is formed on the outer surface of an ink reservoir made of transparent resin and part of it is removed to make the ink inside visible.

<Method for manufacturing ink reservoir according to this embodiment>
Next, a method for manufacturing the ink reservoir according to this embodiment will be described.
The method for manufacturing the ink reservoir according to this embodiment includes the following steps.
Step 1: A step of mixing a ceramic raw material fine powder (for example, alumina (Al ₂ O ₃ ) fine powder) with an organic binder to obtain a compound.
Step 2: A step of forming a cylindrical molded body from the obtained compound using an extruder.
Step 3: Sintering the formed compact.
Step 4: A step of subjecting the obtained sintered body to a hot isostatic pressing (HIP) treatment to obtain a light-transmitting ink reservoir.

Hot isostatic pressing (HIP) can be performed, for example, at 1400°C and 1000 atmospheres in an argon atmosphere. Applying isostatic pressure to a sintered body using gas as a pressure medium reduces porosity and increases density. Sintered bodies lack translucency due to scattering from pores and precipitates, scattering from grain boundary phases, and scattering from grain boundary domains. However, applying isostatic high pressure in a high-temperature environment reduces scattering factors from pores and grain boundaries, making the body translucent.

By using the hot isostatic pressing (HIP) process described above, it is possible to obtain a ceramic ink reservoir that is translucent enough to allow the ink contained in the interior region to be seen from the outside.

In this embodiment, the ink reservoir is formed by extrusion molding, but the method is not limited to this and it can also be formed by a conventionally known molding method such as injection molding or press molding.
In the present embodiment, the ink reservoir cylinder is manufactured by hot isostatic pressing (HIP), but the method is not limited to this. For example, the ink reservoir cylinder can be manufactured by any known manufacturing method, including a method using microwave plasma sintering, a method in which primary sintering is followed by secondary sintering at a higher temperature, and the like.

In addition, while this embodiment uses alumina as the ceramic material, this is not a limitation. Any known translucent ceramic material, including PLZT (oxide of lead, lanthanum, zirconium, and titanium), can be used. Among these, alumina is preferable, taking into consideration the ease of material availability and the balance between translucency, strength, and hardness.

The crystal grain size of the ceramic that makes up the ink reservoir is preferably 0.1 μm or more and 30 μm or less, more preferably 0.2 μm or more and 10 μm or less, even more preferably 0.3 μm or more and 5 μm or less, and particularly preferably 0.3 μm or more and 1 μm or less. If the crystal grain size of the ceramic is within the above numerical range, it is easy to achieve a balance between translucency, strength, and hardness, and, as will be described later, it is easy to adjust the surface roughness to an appropriate level.

The crystal grain size of ceramics can be determined by a planimetric method using an SEM observation image. Specifically, a circle of known area is drawn on the SEM observation image, and the number of crystal grains within the circle (Nc) and the number of crystal grains on the circumference of the circle (Ni) are counted, and the total number of crystal grains (Nc
+Ni) is 250±50, and then the crystal grain size can be calculated using the following formula (A).

Crystal particle diameter = 2/{π×(Nc+(1/2)×Ni)/(A/M2)}0.5...Formula (A)

In the above formula (A), Nc is the number of crystal grains in the circle, Ni is the number of crystal grains on the circumference of the circle, A is the area of the circle, and M is the magnification of the scanning electron microscope observation (for example, 5,000 to 10,000 times).
0 times). In addition, the number of crystal grains (Nc + Ni) in one SEM observation image is 200.
When the number is less than 1, (Nc+Ni) may be set to 250±50 using multiple SEM observation images.

(Ink visibility)
It is generally considered preferable for the ink contained in the internal region to have a contact angle of 20 degrees or more or 30 degrees or more (see "θ" in Figures 2 and 3) between the ink contained in the internal region and the inner surface of the internal region. Even when the contact angle is in this range, if the contact angle is relatively small, even when the ink is consumed and reduced, the ink may adhere to the inner surface of the internal region, making it difficult to visually confirm the ink level from the outside. In other words, when the ink follows, ink may adhere and remain on the inner surface of the ink reservoir, causing problems with ink visibility.

If there is a problem with the visibility of the ink, it will be impossible to accurately check the remaining ink level, which could lead to problems such as suddenly running out of ink.

Regarding the contact angle with ink, it is generally said that a smooth surface has a contact angle of about 50 degrees. Furthermore, a surface with a contact angle of 60 degrees or more is said to be a "water-repellent surface" that can sufficiently suppress ink adhesion. Furthermore, a water-repellent surface with a contact angle of 70 degrees or more can even more effectively suppress ink adhesion.
Therefore, in order to ensure the visibility of the ink so that the remaining amount of ink can be accurately confirmed, it is preferable that there is a contact angle of 50 degrees or more between the ink and the inner surface of the ink storage area that comes into contact with this ink, more preferably a contact angle of 60 degrees or more, and even more preferably a contact angle of 70 degrees or more.

As described above, when the contact angle between the stored ink and the inner surface of the internal region in contact with this ink is 50 degrees or more, the ink can be made visible enough to accurately check the remaining amount of ink. Furthermore, when the contact angle between the stored ink and the inner surface of the internal region in contact with this ink is 60 degrees or more, the ink can be made even more visible, and when the contact angle between the stored ink and the inner surface of the internal region in contact with this ink is 70 degrees or more, the ink can be made even more visible.

(Relationship between surface roughness of the inner surface of the internal region and contact angle)
It is known that the contact angle varies depending on the surface roughness of the contact surface. In order to obtain a contact angle that ensures sufficient ink visibility, the inventors fabricated ceramic samples with various surface roughnesses and measured their contact angles.

Specifically, rectangular alumina components were prototyped by extrusion molding, and the outer surfaces were surface-treated to create four samples with different surface roughness. The samples used were ordinary alumina (milky white) rather than translucent alumina, but this is thought to have little effect on the relationship between surface roughness and contact angle.

To describe the four samples in more detail, Sample 1 was an extrusion-molded and sintered component that had been finish-processed using a lapping machine and had an arithmetic mean roughness Ra (JIS B0601) of 0.011 μm; Sample 2 was an extrusion-molded component that had not been processed and had an arithmetic mean roughness Ra (JIS B0601) of 0.035 μm; Sample 3 was an extrusion-molded component that had been medium-polished and had an arithmetic mean roughness Ra (JIS B0601) of 0.298 μm; and Sample 4 was an extrusion-molded component that had been coarse-polished and had an arithmetic mean roughness Ra (JIS B0601) of 0.540 μm.

Ion-exchanged water was dropped onto these four samples, and the contact angles were measured. More specifically, measurements were made using the sessile drop method (θ/2 method) using an automatic contact angle meter DMo-602 manufactured by Kyowa Interface Science Co., Ltd. Light was shone on the droplet dropped onto the sample, an image of the droplet was captured with an imaging device, and the contact angle was calculated using image analysis. The measurement results are shown in the table below.

It is known that there is no difference in contact angle trends (contact angle increases as the arithmetic mean roughness increases) between writing ink and ion-exchanged water, at least for water-based inks that use water as the primary solvent. Furthermore, for water-based inks that contain 90% or more water as a solvent, such as fountain pen inks (for example, product name: INK-30-B, manufactured by Pilot Corporation), there is only a slight difference in the contact angle between them and ion-exchanged water.

Ink for writing instruments may contain additives such as surfactants to control the surface tension (contact angle with the ink reservoir).
The components of the fountain pen ink (INK-30-B) include dye, water, pH adjuster, surfactant, preservative, etc. The surface tension of the fountain pen ink (INK-30-B) was measured in an environment of 20°C using a surface tension meter (DY-200) manufactured by Kyowa Interface Science Co., Ltd. by the vertical plate method using a platinum plate, and was found to be 51 mN/m.

The measurement results are shown in a graph in Figure 1. Figure 1 is a graph showing the results of measuring the contact angle of samples made from alumina with different surface roughness. The horizontal axis shows surface roughness Ra [μm], and the vertical axis shows contact angle [degrees]. Samples 1 to 4 above were plotted, and the graph was created by connecting the points with a smooth curve.

As is clear from Figure 1, the contact angle tends to increase as the surface roughness increases. In particular, when the surface roughness Ra [μm] is 0.1 μm or less, the degree of increase in contact angle with increasing surface roughness (the slope of the graph) is large, and when the surface roughness Ra [μm] is greater than 0.1 μm, the degree of increase in contact angle with increasing surface roughness (the slope of the graph) tends to decrease.

From the graph, it is believed that if the surface roughness Ra [μm] of the inner surface is 0.01 μm or more, a contact angle of more than 60 degrees will be obtained, resulting in sufficient ink visibility. If the surface roughness Ra [μm] of the inner surface is 0.03 μm or more, a contact angle of more than 65 degrees will be obtained, resulting in better ink visibility. If the surface roughness Ra [μm] of the inner surface is 0.05 μm or more, a contact angle of more than 70 degrees will be obtained, resulting in even better ink visibility.
The surface roughness Ra of the inner surface is measured using a stylus surface roughness meter (product name: Surfcorder SE-3400) manufactured by Kosaka Laboratory Co., Ltd. under the measurement conditions of JIS B 061-2001.

(Balance between ink visibility and ink legibility)
As mentioned above, increasing the surface roughness of the inner surface increases the contact angle, which is advantageous for the visibility (wettability) of the ink, but on the other hand, increasing the surface roughness may decrease transparency, i.e., increasing the surface roughness increases the scattering of light on the surface, which may reduce the visibility of the ink.

The relationship between surface roughness and transparency has been investigated, for example, in the technical paper "Effect of Surface Properties of Transparent Acrylic Resin on Visual Texture" in Journal of the Japan Society of Color Materials, Vol. 92, No. 5, No. 131-135, 2019. The relationship between the measured surface roughness and transmittance of acrylic resin is shown in Fig. 6.
According to Fig. 6, when the arithmetic mean height Sa (ISO 25178) is 1 μm or less, the total light transmittance is considered to exceed 80%. Furthermore, when the arithmetic mean height Sa (ISO 25178) is 0.3 μm or less, the total light transmittance is considered to be 85% or more. Furthermore, it is stated that "when the arithmetic mean height Sa (ISO 25178) is 0.1 μm or less, the total light transmittance exceeds 90%, which is consistent with the optical properties of general acrylic resins (see Section 3.2)."

The effect of surface roughness on transmittance is thought to be similar for translucent ceramic materials as it is for transparent acrylic resins. Arithmetic mean roughness Ra (JIS B0601) and arithmetic mean height Sa (ISO 25178) are essentially the same indicators, and it can be assumed that reducing the arithmetic mean roughness Ra (JIS B0601) value will improve total light transmittance in ceramic materials. Therefore, although this varies depending on the material used, keeping the arithmetic mean roughness Ra (JIS B0601) value to 1 μm or less is likely to achieve good transmittance, e.g., 30% or more, with limited impact from surface roughness and sufficient visual ink visibility. Furthermore, an arithmetic mean roughness Ra (JIS B0601) value of 0.3 μm or less is thought to further improve total light transmittance and therefore provide better ink visibility. Furthermore, it is believed that even better ink visibility (e.g., transmittance of 50% or more) can be achieved by setting the arithmetic mean roughness Ra (JIS B0601) value to 0.1 μm or less.

As described above, in order to achieve both ink visibility and ink recognizability, the surface roughness Ra [μm] of the inner surface is
It is preferable that the thickness is in the range of 0.001 μm or more and 1 μm or less,
More preferably, it is in the range of 0.005 μm or more and 1 μm or less,
It is more preferable that the thickness is in the range of 0.01 μm or more and 1 μm or less,
It is particularly preferable that the thickness is in the range of 0.03 μm or more and 0.3 μm or less.
It is most preferable that the thickness is in the range of 0.05 μm or more and 0.1 μm or less.
The range of the surface roughness Ra [μm] can be any combination of the above lower limit value and upper limit value.

When the surface roughness Ra [μm] of the inner surface of the internal region is in the range of 0.001 μm or more and 1 μm or less, an ink reservoir cylinder can be provided that has excellent ink visibility and gas barrier properties, as well as excellent ink visibility. Furthermore, when the surface roughness Ra [μm] of the inner surface is in the range of 0.005 μm or more and 1 μm or less, an ink reservoir cylinder with even better ink visibility can be provided. Furthermore, when the surface roughness Ra [μm] of the inner surface is in the range of 0.01 μm or more and 1 μm or less, an ink reservoir cylinder with even better ink visibility can be provided. Furthermore, when the surface roughness Ra [μm] of the inner surface is in the range of 0.03 μm or more and 0.3 μm or less, an ink reservoir cylinder with even better ink visibility and excellent ink visibility can be provided. Furthermore, if the inner surface roughness Ra [μm] is in the range of 0.05 μm or more and 0.1 μm or less, an ink reservoir cylinder with even better ink visibility can be provided.

(Ink contained in the ink container)
The ink contained in the ink reservoir will be described below.
The ink contained in the ink reservoir of the present invention may be any ink normally used in writing instruments. The components used in the ink and the physical properties of the ink will be described below.

<Organic solvent>
From the viewpoint of gas barrier properties, suppressing evaporation of the organic solvent, and considering the ink stability over time, it is preferable to use an organic solvent with a boiling point of 160°C or higher, and even more preferably, to use an organic solvent with a boiling point of 200°C or higher. On the other hand, if the boiling point exceeds 300°C, it is likely to affect the drying properties of the handwriting. For this reason, it is preferable to use an organic solvent with a boiling point of 300°C or lower.

Specifically, organic solvents used in aqueous inks include glycerin (290°C), diethylene glycol (245°C), triethylene glycol (276°C), dipropylene glycol (225°C), propylene glycol (188°C), and ethylene glycol (198°C).
Examples of organic solvents for oil-based inks include benzyl alcohol (205° C.), ethylene glycol monophenyl ether (245° C.), and propylene glycol-n-butyl ether (170° C.).

<Ink viscosity>
The ink viscosity of the ink used in this embodiment at 20°C when stationary is preferably 30,000 mPa·s or less. If the viscosity exceeds 30,000 mPa·s, it is likely to affect ink tracking ability and the visibility of the ink in the ink reservoir cylinder according to this embodiment. Therefore, in consideration of improving the visibility of the ink, the ink viscosity is more preferably 10,000 mPa·s or less, even more preferably 5,000 mPa·s or less, particularly preferably 4,000 mPa·s or less, and even more preferably 3,000 mPa·s or less.
The ink viscosity at rest is measured under the following conditions.
For oil-based inks, the ink viscosity is measured at 20°C and a shear rate of 5 sec ^-1 .
For water-based inks, the ink viscosity is measured at 20°C and a shear rate of 1.92 sec ^-1 .

As described above, when the ink viscosity at 20°C when stationary is 30,000 mPa·s or less, the ink contained in the internal region can achieve excellent ink visibility in the ink reservoir.

<Ink surface tension>
The surface tension of the ink used in this embodiment at 20°C is preferably 20 mN/m or more. If the surface tension of the ink is equal to or greater than the above-mentioned range, the visibility of the ink in the ink reservoir according to this embodiment can be improved. In order to improve the above-mentioned effects as well as to maintain good ink dischargeability from the pen tip and obtain good handwriting, the surface tension of the ink is more preferably 25 to 65 mN/m, and even more preferably 30 to 60 mN/m.

As described above, when the ink surface tension at 20° C. of the stored ink is 20 mN/m or more, excellent ink visibility can be obtained in the ink storage cylinder.
The surface tension of the ink is determined by measuring in an environment of 20° C. using a surface tension measuring instrument (DY-200) manufactured by Kyowa Interface Science Co., Ltd., by the vertical plate method using a platinum plate.

(ink follower)
It is preferable that the rear end of the ink contained in the internal region of the ink reservoir be filled with an ink follower that follows the consumption of the ink (see "F" in Figure 3). This is because it improves ink followability and visibility in an ink reservoir made of ceramic material. Furthermore, it also has the effect of a liquid stopper, which further suppresses solvent evaporation from the perspective of gas barrier properties and tends to improve the ink's stability over time.

Either liquid or solid ink followers can be used. Liquid ink backflow preventers preferably contain a non-volatile medium such as polybutene or silicone oil. If desired, silica, aluminum silicate, etc. can also be added to the medium.

As described above, when the rear end of the stored ink is filled with an ink follower that follows the consumption of the ink, ink followability is improved, resulting in better ink visibility.

(Writing implement with ink reservoir)
Next, a writing instrument equipped with an ink reservoir will be described with reference to Figures 2 and 3, taking a ballpoint pen as an example. Figure 2 is a side cross-sectional view schematically showing a writing instrument equipped with an ink reservoir according to one embodiment of the present invention, which functions as a ballpoint pen refill. Figure 3 is a side cross-sectional view schematically showing a writing instrument equipped with an ink reservoir according to another embodiment of the present invention, which functions as a ballpoint pen refill.

In the writing instrument (ballpoint pen) 10 shown in Figure 2, a ballpoint pen tip 4 is attached directly to the tip side of an ink reservoir 2 (translucent ceramics) whose internal region contains ink G1. In the writing instrument (ballpoint pen) 10 shown in Figure 3, the ballpoint pen tip 4 is attached via a tip holder 6 to the tip side of an ink reservoir 2 whose internal region contains ink G2. In the writing instrument (ballpoint pen) 10 shown in Figure 3, the rear end of the stored ink G is filled with an ink follower F (containing polybutene) that follows the consumption of the ink.

The ink viscosity of Ink G1 was measured using an AR-G2 (stainless steel 40 mm 2° rotor) manufactured by TA Instruments Inc. at a shear rate of 5 sec ⁻¹ (at rest) in an environment of 20°C, and was found to be 20,000 mPa·s.
The ink viscosity of Ink G2 was measured using a Brookfield DV-II viscometer (CPE-42 rotor) at a shear rate of 1.92 sec ⁻¹ (at rest) in an environment of 20° C., and was found to be 1600 mPa·s.

The surface tension of Ink G2 was measured in an environment of 20° C. using a surface tension measuring instrument (DY-200) manufactured by Kyowa Interface Science Co., Ltd. by the vertical plate method using a platinum plate, and was found to be 28 mN/m.
Ink G1 ingredients: dye, benzyl alcohol (205°C), ethylene glycol monophenyl ether (245°C), butyral resin, amine, surfactant. Ink G2 ingredients: pigment, glycerin (290°C), water, amine, surfactant, preservative, xanthan gum.

In either case, it is possible to provide an ink reservoir 2 and a writing instrument (ballpoint pen) 10 that have both excellent gas barrier properties and ink visibility.

The ink reservoir tube according to this embodiment is not limited to being attached to a ballpoint pen, but can also be attached to a marker, fountain pen, etc. The ink contained in the internal region can be any known oil-based or water-based ink.

As described above, the first embodiment of the present invention is
an interior region for containing ink for the writing instrument;
The ink reservoir is made of a ceramic material that is translucent enough to allow the ink contained in the internal region to be seen from the outside.

A second embodiment of the present invention is a method for manufacturing a semiconductor device according to the first embodiment,
The ink reservoir cylinder has an inner surface in the interior region having an arithmetic surface roughness Ra in the range of 0.001 μm to 1 μm.

A third embodiment of the present invention is the first or second embodiment,
The ink reservoir cylinder has a contact angle of 50 degrees or more between the ink contained therein and the inner surface of the internal region that comes into contact with the ink.

A fourth embodiment of the present invention is any one of the first to third embodiments,
The ceramic material of the ink reservoir is alumina.

A fifth embodiment of the present invention is any one of the first to fourth embodiments,
The ink reservoir cylinder has a surface tension of 20 mN/m or more at 20°C.

A sixth embodiment of the present invention is any one of the first to fifth embodiments,
The ink reservoir cylinder has a viscosity of 30,000 mPa·s or less when the ink is stored at 20° C. and stationary.

A seventh embodiment of the present invention is any one of the first to sixth embodiments,
This is an ink storage tube in which the rear end of the stored ink is filled with an ink follower that follows the consumption of the ink.

An eighth embodiment of the present invention is
A writing implement equipped with the ink reservoir of any one of the first to seventh embodiments.

Although embodiments of the present invention have been described, the disclosed content may vary in structural details, and changes in the combination and order of elements in the embodiments may be made without departing from the scope and spirit of the claimed invention.

2 Ink reservoir 10 Writing implement F Ink follower G1, G2 Ink

Claims (8)

an interior region for containing ink for the writing instrument;
The ink cartridge is formed from a ceramic material that does not contain a resin material and has a translucency that allows the ink contained in the internal region to be visually recognized from the outside,
The ink reservoir cylinder is characterized in that the crystal grain size of the ceramic material is 0.1 μm or more and 30 μm or less . An ink reservoir cylinder as described in claim 1, characterized in that the arithmetic surface roughness Ra of the inner surface of the internal region is in the range of 0.001 μm or more and 1 μm or less. The ink reservoir cylinder according to claim 1, characterized in that the contact angle between the stored ink and the inner surface of the internal region that comes into contact with the ink is 50 degrees or more. An ink reservoir as described in claim 1, characterized in that the ceramic material is alumina. The ink reservoir cylinder according to claim 2, characterized in that the ink contained therein has a surface tension of 20 mN/m or more at 20°C. The ink reservoir cylinder according to claim 2, characterized in that the viscosity of the ink contained therein at 20°C and when stationary is 30,000 mPa·s or less. The ink reservoir cylinder according to claim 2, characterized in that the rear end of the stored ink is filled with an ink follower that follows the consumption of the ink. A writing instrument comprising the ink reservoir tube described in any one of claims 1 to 7.