JP7696159B2 - Writing implements for disposable diapers - Google Patents

Description

The present invention relates to a writing instrument for use with disposable diapers.

Disposable diapers for infants and toddlers are widely used. Disposable diapers are disposable and feel good on the skin. They are also easy for the user (the person wearing them) to put on and take off. For this reason, disposable diapers are used exclusively in childcare facilities that look after infants and toddlers.

Figure 9 shows the structure of a typical disposable diaper. The disposable diaper 100 shown in Figure 9 has a waterproof outer skin 101 and a water-permeable inner skin 102 that comes into contact with the user's skin, with absorbent material 103 built in between. The absorbent material 103 is, for example, a laminate of water-absorbing paper, cotton-like pulp, polymeric water absorbents, etc.

The disposable diapers used at childcare facilities are usually brought by parents, and so childcare facilities handle disposable diapers for multiple people. For this reason, parents are often required to write their infant's name on the disposable diapers they bring with them. Currently, parents write their infant's name and other information on the disposable diapers using existing writing implements such as markers or ballpoint pens.

Japanese Unexamined Patent Publication No. 62-234997 JP 2015-199327 A JP 2020-93511 A

However, the outer cover 101 of the disposable diaper 100 is often made of nonwoven fabric, which is made of fibers solidified into a sheet shape. Therefore, the pen tip of the writing implement of the prior art is likely to get caught on the outer cover 101, making it difficult to write.
For example, a felt-tip pen has a nib made of a bundle of fibers, and when writing with the pen, the nib can get tangled in the fibers of the outer cover material 101 and get caught, making it difficult to write.
The marker pen has a hard pen tip made of resin or sintered material, and so when writing with the marker pen, the pen tip is likely to get caught on the outer cover material 101, making writing difficult.

The same is true for ballpoint pens, where the tip of the pen easily gets caught in the outer cover material 101, making it difficult to write. That is, in normal ballpoint pens, the ball diameter is generally 0.6 mm or less. In contrast, as mentioned above, the outer cover material 101 of the disposable diaper 100 is often nonwoven fabric, in which fibers are solidified into a sheet shape. Therefore, when using a ballpoint pen of the prior art, the ball gets caught between the fibers of the nonwoven fabric, making it difficult to move the ballpoint pen.

In one type of ballpoint pen, a spring is built into the pen, and the ball is pressed toward the tip opening by the spring. In a ballpoint pen with this structure, like the marker described above, it is necessary to push the ball in against the spring. However, when the ball is pressed against the disposable diaper 100, the surface of the disposable diaper 100 is indented, making it difficult for the ball to move. This makes it difficult to write smoothly.

The objective of the present invention is to develop a new writing instrument suitable for writing on disposable diapers.

An aspect for solving the above-mentioned problems is a writing implement for disposable diapers, which has an ink storage section in which ink is stored, a pen tip connected to the ink storage section, and a spring, the pen tip has a tip body and a valve body, the tip body has a storage space that stores the valve body, a tip opening, and an ink introduction hole, the tip opening is located on the tip side of the storage space and communicates between the inside and outside of the storage space, the ink introduction hole has a tip side that opens into an inner surface on the rear end side of the storage space and communicates between the inside and outside of the storage space, a seat is provided within the storage space with the opening of the ink introduction hole as its center, the valve body is spherical with a diameter of 0.8 mm to 1.2 mm, the valve body is within the storage space and a part of it is exposed from the tip opening, the spring presses the valve body toward the tip opening side, and a first pressing force, which is a pressing force of the spring when the valve body closes the tip opening, is 2.9 x ¹⁰ the spring pressure is from 1.5×10 -1 N to 1.5×10 ^-1 N, a value obtained by subtracting the first pressing force from a second pressing force which is the pressing force of the spring when the valve body is in contact with the seat is 6.9×10 ^-3 N or less, and the amount of ink flowing out during continuous writing is from 100 mg to 200 mg per 10 m.

In this embodiment of the writing implement for disposable diapers, the valve body is spherical, and writing is performed by pressing the valve body directly against the surface of the disposable diaper. If the diameter of the valve body is too small, it will get caught on the fibers of the cover material (nonwoven fabric) of the disposable diaper. On the other hand, if the diameter of the valve body is too large, it is difficult to write characters and the characters will become blurred. However, the valve body used in this embodiment has a diameter of 0.8 mm or more, so it is less likely to get caught on the nonwoven fabric that makes up the surface of the disposable diaper. In addition, the valve body used in this embodiment has a diameter of 1.2 mm or less, so it is easy to write characters.

The writing implement for disposable diapers of this embodiment has a valve body at the tip opening of the pen tip, which closes the tip opening, and is pressed toward the tip opening by a spring.
In the writing implement for disposable diapers of this embodiment, the valve body is pressed against the surface of the disposable diaper to open the tip opening and eject ink.
As mentioned above, disposable diapers are soft, but in the disposable diaper writing instrument of this embodiment, the spring pressure (first pressure) when the tip opening is sealed is weak, so that the disposable diaper is less likely to dent when the valve body is pressed against it, making it easy to write.
In addition, with the present embodiment of the writing instrument for disposable diapers, the difference between the spring pressing force (first pressing force) when the valve body is sealing the tip opening and the spring pressing force (second pressing force) when the valve body is in contact with the seat portion is small, making it easy to write even on fluffy disposable diapers.
That is, in a normal ballpoint pen with a spring, the ball is pressed against the seat during writing, and there is no problem even if there is a large difference between the first pressing force and the second pressing force.
In contrast, with a writing instrument for disposable diapers, writing may be performed in an intermediate state where the valve body is not in contact with the seat, and writing is difficult if the change in pressure is large. In contrast, with the writing instrument for disposable diapers of this embodiment, the difference between the pressure of the spring when the valve body is closing the tip opening (first pressure) and the pressure of the spring when the valve body is in contact with the seat (second pressure) is small, making it easy to write on a disposable diaper.

The present invention provides a writing instrument suitable for writing on disposable diapers.

1 is an exploded perspective view of a writing implement for disposable diapers according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the entire core member of the writing instrument for disposable diapers of FIG. 1 . 2 is a cross-sectional view of a tip plug portion of a core member of the writing implement for disposable diapers of FIG. 1 . 4(a) is an enlarged cross-sectional view of the tip opening of the nib tip of the core member in Figure 3, (b) is an enlarged cross-sectional view of the tip opening of the nib tip with the valve body removed from the nib tip portion, and (c) is a cross-sectional view taken along line A-A of (b). 1A and 1B are explanatory diagrams showing the state of the valve body and the tip opening, in which (a) shows the state in which the valve body closes the tip opening, and (b) shows the state in which the valve body is fully pressed in and abuts against the seat. This is a microscopic photograph of the surface of a disposable diaper. These are micrographs showing the state when writing on the surface of a paper diaper with a writing instrument having a pen tip, where (a) shows the case when the tip diameter is 0.6 mm, (b) shows the case when the tip diameter is 0.8 mm, and (c) shows the case when the tip diameter is 1.0 mm. Photographs showing the results of a diaper writing test, where (a) is when the spring load is 3.8 gf, (b) is when the spring load is 5.5 gf, (c) is when the spring load is 7.5 gf, (d) is when the spring load is 10.0 gf, (e) is when the spring load is 12.5 gf, and (f) is when the spring load is 20 gf. 1 is a cross-sectional view showing the cross-sectional structure of a typical disposable diaper, together with the pen tip portion of a writing implement.

The following describes an embodiment of the present invention. Note that in order to make the invention easier to understand, the size and thickness of each component in each drawing are exaggerated and do not necessarily correspond to the actual size and ratio.

First, the components and structure of the writing tool 50 for disposable diapers will be roughly described.
The writing implement 50 for disposable diapers shown in FIG. 1 is composed of a core member 1, a main body portion 51 for housing the core member 1, and a cap 52.

As shown in Figures 2 and 3, the core member 1 has an ink storage section 2, a tip plug 3, a pen tip 5, and a spring 6. The ink storage section 2 is a long, thin tube, and its inside is hollow. The ink storage section 2 is filled with ink 7. There is also an ink follower 8 at the rear end inside the ink storage section 2.

The tip plug 3 is a member for connecting the pen tip 5 to the ink storage section 2, and has a conical shape at the tip. The inside of the tip plug 3 is hollow, and a communication hole 10 is provided for conducting the ink 7 from the ink storage section 2 to the pen tip 5. Inside the tip plug 3, a step 11 is provided, as shown in Figure 3.

The pen tip 5 has a tip body 13 and a valve body 15.

The tip body 13 has an outer shape such that the tip end side has a substantially conical shape and the rear end side has a substantially cylindrical shape.
A valve body accommodating space 16 and an ink introduction hole 17 are provided inside the tip body 13. The ink introduction hole 17 has a tip side that opens to the inner surface of the rear end side of the valve body accommodating space 16, and communicates between the inside and outside of the valve body accommodating space 16.
Further, at the tip of the valve body accommodating space 16, there is a tip opening 18. The tip opening 18 is located on the tip side of the valve body accommodating space 16 and connects the inside and outside of the valve body accommodating space 16.
The valve body accommodating space 16 has a seat 22 centered on the opening 20 of the ink introducing hole 17 .

3 and 4 , the valve body accommodating space 16 has a side wall surface 21 which is a side wall shaped like the inside of a cylinder, and a seat forming surface 25 and a connecting surface 23 which are located on the rear end side of the side wall surface 21. The connecting surface 23 is a surface which connects the side wall surface 21 and the seat forming surface 25.
As shown in FIG. 4, the shape of the connection surface 23 is a side shape of a truncated cone with the apex facing the tip.
Therefore, an annular groove 30 is formed between the side wall surface 21 and the seat portion 22. In addition, a bulge 31 that bulges toward the ink introducing hole 17 is formed on the center side of the seat portion 22.
4C, radial slits 38 are provided around the ink conducting hole 17. The slits 38 are called arrow grooves.
The slit 38 is connected to the valve body accommodating space 16 side, and the ink 7 can enter the slit 38 from the ink introducing hole 17 and flow out to the valve body accommodating space 16 side.
That is, at the opening end of the ink through hole 17 facing the valve body accommodating space 16, there is a seat 22 that supports the valve body 15, and the valve body 15 contacts the seat 22, but since there is a slit 38 in the seat 22, the opening end of the ink through hole 17 is not completely blocked by the valve body 15.

The valve element 15 employed in this embodiment is spherical. As shown in Figures 3 and 4(a), a part of the valve element 15 is exposed from a tip opening 18 which is an opening of the valve element accommodating space 16. The valve element 15 is held in the valve element accommodating space 16 so as to be rotatable.
The material of the valve body 15 is SiC. However, the material of the valve body 15 is not particularly limited, and stainless steel, sintered alumina, zirconia, WC, or other known materials can also be used.

3, the spring 6 is a member for biasing the valve body 15 outward from within the pen tip 5. The spring 6 has a generally spirally wound coil shape and has a biasing force.
3, the spring 6 is provided with densely wound portions 33, 35 and a coarsely wound portion 36. The coarsely wound portion 36 is located between the densely wound portions 33, 35.
At the tip of the densely wound portion 33 on the tip side, there is a small diameter wound portion 40 .

The rear end side of the front plug 3 is fitted into the front end part of the ink storage part 2. Furthermore, the rear end side of the pen tip 5 is fitted into the front end part of the front plug 3.
The spring 6 is fixed in the tip plug 3 and the pen tip 5. Specifically, the spring 6 is disposed across the ink conducting hole 17 of the tip body 13 of the pen tip 5 and the communication hole 10 of the tip plug 3. The rear end side of the spring 6 protrudes from the tip body 13 and abuts against and engages with the step 11 of the communication hole 10 of the tip plug 3. Meanwhile, the tip end of the spring 6 reaches the valve body accommodating space 16 through the ink conducting hole 17 of the tip body 13 and abuts against the valve body 15.

The writing implement 50 for disposable diapers has a core member 1 housed in a main body 51, and a cap 52 attached thereto.
When in use, the cap 52 is removed and the main body 51 is held by hand.

In this embodiment, the valve body 15 is pressed outward from within the pen tip 5 by the spring 6. Therefore, the tip opening 18 of the pen tip 5 is normally forcibly sealed by the valve body 15 to prevent leakage of the ink 7. In other words, except when writing, the valve body 15 is pressed by the spring 6 to forcibly seal the tip opening 18.
On the other hand, when writing using the writing instrument 50 for disposable diapers, the valve body 15 is pressed against the disposable diaper 100, the valve body 15 moves backward against the spring 6, and the valve body 15 leaves the tip opening 18, creating an ejection gap between the tip opening 18 and the valve body 15.
The ink 7 is discharged from between the tip opening 18 and the valve body 15. When the writing tool 50 for disposable diapers is moved while being pressed against the disposable diaper 100, the valve body 15 rotates and a line is drawn.

Next, the characteristic configuration of the writing tool 50 for disposable diapers of this embodiment will be described.
The writing implement 50 for disposable diapers of this embodiment has the following characteristic configuration.
(1) The diameter of the valve body 15 is larger than that of a normal ballpoint pen.
(2) The pressing force of the spring 6 pressing the valve body 15 is weak.
(3) The amount of change in the force pressing against the valve body 15 is small.
(4) The amount of ink ejected is large.

(1) Diameter of the Valve Body 15 The diameter of the valve body 15 employed in the writing tool 50 for disposable diapers of this embodiment is not less than 0.8 mm and not more than 1.2 mm.
The writing implement 50 for disposable diapers of this embodiment uses a ball that is larger than the ball of a normal ballpoint pen as the valve body and writing ball, so that it is less likely to get caught on the nonwoven fabric that constitutes the surface of the disposable diaper, making it easier to write.
In addition, since the diameter of the valve body 15 is 1.2 mm or less, the lines when writing do not become excessively thick and the ink does not bleed, making it easy to write characters.

(2) Pressing Force of Spring 6 The spring 6 employed in the disposable diaper writing instrument 50 of this embodiment has a pressing force (first pressing force) of 2.9×10 ⁻² N to 1.5×10 ⁻¹ N (3 gf to 15 gf) when the valve body 15 closes the tip opening 18 of the tip body 13. The first pressing force of the spring 6 is preferably 6.9×10 ⁻² N to 1.2×10 ⁻¹ N (7 gf to 12 gf), and more preferably 8.8×10 ⁻² N to 1.1×10 ⁻¹ N (9 gf to 11 gf).

In the writing instrument for disposable diapers 50 of this embodiment, the tip body 13 of the pen tip 5 has a tip opening 18, which is closed by the valve body 15. Although the disposable diaper 100 is soft, in the writing instrument for disposable diapers 50 of this embodiment, the pressing force (first pressing force) of the spring 6 when the tip opening 18 is closed is weak, so that the disposable diaper 10 is less likely to be dented when the valve body 15 is pressed against it, making it easy to write. In other words, the valve body 15 can be pressed and moved with a slight force that does not dent the surface of the disposable diaper, allowing ink to be ejected.
In addition, since the valve body 15 is pressed against the tip opening 18 by the spring 6 with a weak force, there is little risk of ink leaking when the pen is not in use. In addition, since the valve body 15 seals the tip opening 18 with a weak force, the ink inside does not dry out when the pen is not in use.
According to experiments by the inventors, if the first pressing force of the spring 6 is 2.9×10 ⁻² N or more (3 gf or more), ink is unlikely to leak when the pen is not in use. However, there are cases where it takes time for the valve body 15 to completely close the tip opening 18 immediately after writing, which may cause ink to leak immediately after writing.
If the first pressing force of the spring 6 is 6.9×10 ⁻² N or more (7 gf or more), leakage of ink immediately after writing is significantly reduced. If the first pressing force of the spring 6 is 8.8×10 ⁻² N or more (9 gf or more), leakage of ink immediately after writing can be almost completely prevented.
On the other hand, the weaker the pressing force of the spring 6, the smaller the indentation of the disposable diaper 10.

(3) Amount of change in force pressing against valve body 15 The spring 6 used in the disposable diaper writing instrument 50 of this embodiment has a difference (ΔF=F2-F1) between the pressing force of the spring 6 when the valve body 15 is blocking the tip opening 18 (first pressing force: F1) and the pressing force of the spring when the valve body 15 is fully pressed in and abutting against the seat portion 22 (second pressing force: F2), i.e., the value obtained by subtracting the first pressing force from the second pressing force, of 6.9 x ^10-3 N or less (0.7 gf or less).
5A shows a state in which the valve body 15 closes the tip opening 18, and FIG. 5B shows a state in which the valve body 15 is fully pressed in and abuts against the seat portion 22. As shown in FIG.
In this embodiment, the amount of movement L of the valve body 15 between the two is 0.08 mm to 0.12 mm, and preferably 0.1 mm.
The spring constant of the spring 6 is desirably 7.4×10 ⁻³ N/mm or less (7.5 gf/mm or less).

When using the writing tool 50 for disposable diapers, writing may be performed in an incomplete state where the valve body 15 is not in contact with the seat portion 22, and large changes in pressure can make writing difficult. In contrast, the writing tool 50 for disposable diapers of this embodiment makes it easy to write on the disposable diaper 100 because the difference between the spring pressure (first pressure) when the valve body 15 is sealing the tip opening and the spring pressure (second pressure) when the valve body 15 is in contact with the seat portion is small.

(4) Amount of ink discharged The writing implement 50 for disposable diapers of this embodiment has an ink flow rate of 100 mg or more and 200 mg or less per 10 m during continuous writing. The ink flow rate during continuous writing can be evaluated by measuring the amount of ink flow (mg) when 10 m is continuously written on high-quality paper under the following conditions: load of 100 g, writing angle of 65 degrees, writing speed of 7 cm/sec, temperature of 23° C., and humidity of 50%. The ink flow rate during continuous writing with the writing implement 50 for disposable diapers is greater than the ink flow rate of a normal ballpoint pen.

1. Relationship between catching and ball diameter (1) Microscopic observation of the surface of a paper diaper The surface of a commercially available paper diaper (product name: Mooney, manufactured by Unicharm Corporation) was observed under a microscope (Figure 6). In Figure 6, circles with diameters of 0.5 mm, 0.6 mm, 0.8 mm, and 1.0 mm are additionally shown (represented as φ05, φ06, φ08, and φ10, respectively). In other words, the fibers of the nonwoven fabric are randomly entangled on the surface of the paper diaper, and it was thought that the state of this entanglement strongly influenced the catching of the ball.

(2) Microscopic observation of the state during writing In order to investigate the relationship between the catching on the surface of the paper diaper and the diameter of the ball (ball diameter), simulated writing implements with balls of 0.6 mm, 0.8 mm, or 1.0 mm diameter were prepared. To simulate writing, the surface of the paper diaper was rubbed with each writing implement, and the state at that time was observed under a microscope. The results are shown in Figures 7(a) to (c). That is, in the case of a ball diameter of 0.6 mm, the tip penetrated into the gaps between the fibers of the nonwoven fabric, and catching during writing was noticeable (Figure 7(a)). On the other hand, in the case of a ball diameter of 0.8 mm, the catching of the tip was reduced (Figure 7(b)), and in the case of a ball diameter of 1.0 mm, there was almost no catching (Figure 7(c)).

2. Relationship between spring load and ink leakage (1) Preparation of ink composition An ink composition having the following composition was prepared (unit: parts by mass).
Nigrosine dye: 11
Oleic acid: 7
・Alkylphenol resin: 4
Maleic acid resin: 6
Benzoic acid sucrose ester: 2
Propylene glycol monomethyl ether: 53.5
Ethyl alcohol: 10
Propylene glycol n-butyl ether: 6
Silicone surfactant: 0.5

The viscosity of the prepared ink composition (20°C, 20 rpm, ELD type viscometer 1°34' cone) was 15 mPa·s and the surface tension was 22.5 mN/m.

(2) Preparation of writing implements with different spring loads Six writing implements (ballpoint pens) with different spring loads (the spring pressure when the ball closes the tip opening; first pressure) were prepared using a ball with a diameter of 0.8 mm and the above ink composition. The spring loads selected were 3.8 gf (Experimental Example 2), 5.5 gf (Experimental Example 3), 7.5 gf (Experimental Example 4), 10.0 gf (Experimental Example 5), 12.5 gf (Experimental Example 6), and 20 gf (Experimental Example 7). A similar writing implement (Experimental Example 1) without a spring was also prepared separately.
The ball movement amount L (FIG. 5) was set to 0.1 mm. At this time, the second pressing force (the pressing force of the spring when the ball is in contact with the seat) in each writing instrument was 3.99 gf (Experimental Example 2), 5.77 gf (Experimental Example 3), 7.88 gf (Experimental Example 4), 10.51 gf (Experimental Example 5), 13.14 (Experimental Example 6), and 21.04 gf (Experimental Example 7). Table 1 shows the first pressing force (F1), the second pressing force (F2), the difference between the first pressing force and the second pressing force (ΔF=F2-F1), and the ratio (%) of the difference to the first pressing force (P=ΔF/F1×100) in each writing instrument.

(3) Evaluation of diaper writing property and ink leakage Each writing instrument was used to draw 10 circles (◯) on blank letter paper in succession, and the presence or absence of ink leakage from the pen tip when not writing was examined (pen tip ink leakage test). In addition, each writing instrument was used to write on a paper diaper, and the presence or absence of interruption of the writing was examined (diaper writing property test). As paper diapers, the following products were used: "Moony" (Unicharm), "Mamy Poko" (Unicharm), "Pampers" (Procter & Gamble), "Merry's" (Kao), "Genki!" (Oji Nepia), and "Goon" (Daioh Paper). Ten samples of each writing instrument were prepared and used for each test.

The results of the ink leakage test are shown in Table 2. The results of the diaper writability test are shown in Figure 8. In the values (fractions) in Table 2, the denominator indicates the number of times 10 circles were written, and the numerator indicates the number of times ink leaked. For example, "1/20" indicates that 10 circles were written 20 times, and ink leakage occurred one time. The leakage rate is the percentage of the total number of times ink leaked out of the total number of tests. Table 2 also shows the spring load (3.8 to 20 gf) of each writing implement.

As shown in Table 2, ink leakage from the pen tip was effectively suppressed when the spring load was 3.8 gf or more (leakage rate: 0-5.8%). In particular, the effect of suppressing ink leakage from the pen tip was remarkable when the spring load was 7.5 gf or more (leakage rate: 0%). On the other hand, when there was no spring, ink leakage from the pen tip frequently occurred (leakage rate: 17%).

As shown in Figure 8, good writing performance was obtained when the spring load was in the range of 12.5 gf or less (ratings A and B). Particularly good writing performance was obtained when the spring load was in the range of 10.0 gf or less (rating A). On the other hand, when the spring load was 20 gf, there were many interruptions in the writing (rating C).

(4) Amount of ink flowing out during continuous writing The amount of ink flowing out during continuous writing was measured for each writing instrument. In detail, 10 circles with a circumference of 10 cm were written continuously on high-quality paper (manufactured by Kishu Paper Co., Ltd.) under the conditions of a load of 100 g, a writing angle of 65 degrees, a writing speed of 7 cm/sec, a temperature of 23°C, and a humidity of 50%, and 10 m of writing was performed. As a result, the amount of ink flowing out for each writing instrument was in the range of 100 mg to 200 mg/10 m.

From the above, by setting the spring load (F1) in the range of 3.8 gf to 12.5 gf (3.7 x 10 ^-2 N to 1.2 x 10 ^-1 N) and setting the difference in pressing force (ΔF) to 0.64 gf or less (6.3 x 10 ^-3 N or less), it is possible to provide a writing implement for disposable diapers that is excellent in both preventing ink leakage from the pen tip and in writing performance on diapers.

REFERENCE SIGNS LIST 1 Core member 2 Ink storage section 5 Pen tip 6 Spring 7 Ink 13 Tip body 15 Valve body 16 Valve body storage space (storage space)
17 Ink guide hole 18 Tip opening 22 Seat 50 Writing implement for disposable diaper 100 Disposable diaper

Claims (1)

A writing implement for disposable diapers, comprising an ink storage section in which ink is stored, a pen tip connected to the ink storage section, and a spring,
the pen tip has a tip body and a valve body, the tip body having an accommodation space for accommodating the valve body, a tip opening, and an ink conducting hole;
the tip opening is located at the tip side of the storage space and communicates the inside and outside of the storage space, the tip side of the ink introducing hole is open to the inner surface at the rear end side of the storage space and communicates the inside and outside of the storage space, and a seat is provided within the storage space centered on the opening of the ink introducing hole,
The valve body is spherical with a diameter of 0.8 mm or more and 1.2 mm or less,
The valve body is disposed within the accommodation space and a portion of the valve body is exposed from the tip opening,
The spring presses the valve body toward the tip opening side,
a first pressing force, which is a pressing force of the spring when the valve body closes the tip opening, is 2.9 × 10 ⁻² N or more and 1.5 × 10 ⁻¹ N or less;
a value obtained by subtracting the first pressing force from a second pressing force, which is a pressing force of the spring when the valve body is in contact with the seat portion, is 6.9 × 10 ^-3 N or less;
A writing implement for use in disposable diapers, characterized in that the amount of ink flowing out during continuous writing is 100 mg or more and 200 mg or less per 10 m.

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