JPH10147091A - Ballpoint pen, ceramic ball for the pen, and manufacture of the ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve satisfactory processability of giving precise sphericity in addition to wear resistance, corrosion resistance and mechanical strength, surface smoothness in the case of a product and writing characteristics by specifying surface roughness of a ceramic ball for a ballpoint pen. SOLUTION: The ceramic ball for a ballpoint pen is formed on its surface to have a width of 0.5μm or more, a depth of 0.2μm or more, a length of 10μm or more without a polishing damage within a region of 100μm<2> , a centerline mean roughness of 4.5 to 10nm and maximum and minimum roughnesses of 50 to 100nm. On the surface of the ball, in an arbitrary range of 2,500m<2> , polishing damages of a width of 0.5μm or more, a depth of 0.2μm or more and a length of 10μm or more are two or less. As the material of the ceramics adapted to the ball for the pen, suitable hardness and strength are required, and hence any of ceramics of alumina, silicon nitride and composite ceramic sintered material is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ballpoint pen, a ceramic ball for a ballpoint pen, and a method for manufacturing a ceramic ball.

[0002] The ceramic ball of the present invention is suitably used for a ballpoint pen, especially a water-based ballpoint pen using a water-based ink, is effective in improving abrasion resistance and corrosion resistance, improving writing characteristics, and has the above object. The present invention relates to a method for easily manufacturing a ceramic ball for a ballpoint pen.

[0003]

2. Description of the Related Art In a writing instrument, in addition to abrasion resistance, corrosion resistance, and mechanical strength, good workability for giving precise sphericity, surface smoothness when a product is produced, and good writing characteristics are obtained. In recent years, there has been a demand for a ballpoint pen ball to be further improved in corrosion resistance with the adoption of a water-based ink which has no ink accumulation and excellent writing taste even in a ballpoint pen.

Normally, the refill of a ball-point pen is a tip,
It consists of a tube and ink, and the tip part consists of a ball and a holder. The size of the ball diameter is generally 0.5 mm to 2.0 mm, and its sphericity is required to be 0.3 μm or less. If a line is drawn at 10 cm / sec, the rotation speed is 60 rpm for a 0.5 mm ball and 45 rpm for a 0.7 mm ball, which indicates that the rotation speed is extremely severe. In the use of several thousand meters, friction of more than one million rotations occurs between the ball and the cradle.

Hitherto, chromium carbide, which is inexpensive and has good writing characteristics, has been most often used as a material for ballpoint pens. There are many problems, such as poor corrosion resistance.

Accordingly, cemented carbides such as tungsten carbide, ceramics and the like have come to be used. Carbide and ceramics have high hardness and are chemically stable, so that their abrasion resistance and corrosion resistance are improved, and the initial writing quality is maintained for an extremely long time as compared with chromium carbide.

If the ball for a ball-point pen is polished too much, the portion that comes into contact with the seat increases, thereby blocking the introduction of ink. Conversely, if the polishing is insufficient, the ball rattles, smooth rotation cannot be obtained, and the metal of the seat is worn away, causing a ball sink (the phenomenon that the ball sinks into the seat), and in a short time There are problems such as being unable to write. For this reason, appropriate polishing is required, and it is required that the ball have a certain range of surface roughness.

However, the optimum surface roughness varies greatly due to differences in materials, submicron surface micropores, and the like. In particular, there are many unclear points regarding the optimum value in the case of ceramics. In addition, the workability is inferior to carbide and ceramics, and it is difficult to always adjust the surface roughness to a certain level depending on the situation such as clogging of the grindstone even if the polishing method is specified. Until now, skilled processing techniques were required,
In order to obtain the required processing accuracy, labor such as repeating the measurement of roughness many times was required.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides good workability that gives precise sphericity in addition to abrasion resistance, corrosion resistance and mechanical strength. An object of the present invention is to provide a ballpoint pen having excellent surface smoothness and good writing characteristics, and a method for producing the same.

[0010]

The object of the present invention can be basically achieved by the following constitution. That is, "100 μm or more in width, 0.2 μm or more in depth, and 10 μm or more in length on the surface of the ball without polishing scratches 100
In the region of μm ² , the center line average roughness is 4.5 nm to 10
nm and a maximum and minimum roughness of 50 to 100 nm. "
It is.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the arithmetic mean roughness can be used as the center line average roughness. In this case, the average value of the absolute values of the deviations from the center plane to the surface in the quantitative plane is used. be able to. Here, the quantitative surface is an area (for example, 10 μm square) for measuring the roughness, and the surface is a curved surface (actually, AFM) obtained by actually measuring the roughness.
Interpolated from the point or line data obtained by the measurement
It is. And, the central plane is a plane formed from the area, which is translated vertically, and the sum of the surface above this plane and the volume enclosed by this plane is equal to the surface below this plane. This plane is set so as to be equal to the sum of the volumes enclosed by this plane (the volume is actually obtained by interpolation from point or line data obtained by measurement with AFM or the like). The deviation is a standard deviation. As the maximum and minimum roughness, the vertical distance from the highest peak to the lowest valley in the quantitative surface can be used, and generally, the maximum and minimum roughness is directly affected by a projection or a deep hole that happens to be in the field of view. Therefore, center line average roughness is more suitable for precise comparison between samples.

In the ceramic ball for a ball-point pen according to the present invention, the surface of the ball has a width of 0.5 μm or more, a depth of 0.2 μm or more, and a length of 10 μm or more in an area of 100 μm ² having no polishing scratches. 3. The center line average roughness is 4.
5 nm to 10 nm, and the maximum and minimum roughness is 50 to 10
It needs to be 0 nm. 4.5n center line roughness
m or less, and when the maximum and minimum roughness is 50 nm or less, the ball is close to a mirror surface state, is too smooth when the ball is set in the pen tip receiver, and comes into contact with the metal of the receiver at the surface, It becomes a state that plugs the ink introduction hole,
Immediately the ink fades and you can no longer write. Also,
Conversely, if the average roughness of the center line of the ball surface is 10 nm or more and the maximum and minimum roughness is 100 nm or more, the surface is too rough and the metal of the seat is rapidly worn, and the ball sinks immediately and the ball rotates. It becomes difficult to write and can not write immediately. Preferably, the center line average roughness is 5 to 9
nm, the maximum and minimum roughness is 60 to 90 μm. The 100
There is no particular limitation on how to take the area of μm ² , but it is convenient and convenient to take a square of 10 μm square, for example. The selected 100 μm ² region satisfies the range of the maximum and minimum roughness and the center line roughness.
When the area of m ^{2 and} the area of 100 μm ² that are not satisfied are mixed on the ceramic ball, a large number of areas of 100 μm ² are selected on one ceramic ball so as not to overlap, and the area of 100 μm ² that is not satisfied is selected. Area is 5
As long as it is within the position, it is acceptable, but preferably it is within 3 positions, more preferably within 1 position.

Further, on the surface of the ball, an arbitrary 25
0.5 μm or more in width and 0.2 μm in depth in the range of 00 μm ²
Preferably, the number of polishing scratches having a length of 10 μm or more is 2 or less, more preferably 1 or less. In the process of polishing, if a groove-like scratch having a width of 0.5 μm or more and a depth of 0.35 μm or more is generated, ink flows from this portion, causing ink dripping or bleeding, which is not desirable. .

As a ceramic material suitable for a ballpoint pen ball, appropriate hardness and strength are required. The hardness is preferably from 1100 to 2000 in Vickers hardness. Below this, the ball is too soft and wears out quickly, while if too hard, the metal in the seat is worn away and a ball sink is more likely to occur. 1200 or more, 1
More preferably 700 or less.

Ceramics made of any one of alumina, mullite, zirconia, silicon nitride, silicon carbide, and a composite ceramic sintered body thereof can be suitably used, and zirconia and silicon carbide are preferable.

Further, the sintered body is desirably made of tetragonal high-strength zirconia substantially free of monoclinic crystals by analyzing the crystal structure by powder X-ray diffraction.
The crushing load of the ball is 200 Newton or more at 0.5 mm diameter, 300 Newton or more at 0.7 mm diameter, 1.0 mm
More preferably, the diameter is 500 Newton or more and the 2.0 mm diameter is 1500 Newton or more.

In the present invention, for example, when high strength zirconia is used for a ball, the zirconia can be obtained by the following manufacturing method and manufacturing process, but the present invention is not limited thereto, and the present invention is not limited thereto. The same can be applied to ceramics.

[Powder type and synthesis method] Purity
A 9% solution of zirconyl oxychloride and yttrium chloride is converted to zirconia (ZrO ₂ ) and yttria (Y ₂ O ₃ ), and the mixture is adjusted so that the molar ratio is 95: 5 to 98: 2. A hydrolysis method for obtaining crystalline hydrated zirconia in an autoclave set at a temperature of about 100 ° C. from the prepared mixed solution, or neutralization by adding ammonia water or the like to lower the solubility to reduce the solubility, A zirconia precursor is obtained by a method such as a neutralization coprecipitation method in which zirconium hydroxide and yttrium hydroxide are precipitated, and then fired to obtain a high-strength zirconia powder raw material.

[Powder Properties and Physical Properties] The primary particle size of the powder is affected by the firing temperature, and when fired at 800 to 1000 ° C., it is distributed in the range of 0.01 to 0.2 μm, with an average of 1 μm.
The secondary particle size is about 0.1 μm. When measured by a laser diffraction method, the secondary particle diameter is distributed in the range of 0.01 to 30 μm, and the average secondary particle diameter is about 1 μm.

[Granulation and Forming Methods] Methods for producing balls for ballpoint pens include a compression type, an extrusion type, and a rolling type. In particular, the compacting by the rolling granulation method rolls the powder to form pellets, so that mass production and cost reduction are easy.

In this method, the liquid is sprayed while rolling the dry powder raw material by the action of a rotating container, a stirring blade, or by a mechanical method using a vibrating means, thereby producing a substantially spherical pellet having the required strength. Things.

[Sintering and Processing Method] The compacted pellets can be obtained by firing the formed pellets in the atmosphere at 1300 to 1500 ° C. for 30 minutes to 3 hours. The finish is polished by a double-sided honing machine and a barrel polisher, and finally finished to a mirror surface having a maximum roughness of 50 nm or less. Preferably, it is mirror-polished to 30 nm or less.

The mirror-finished ball is given a smooth uneven shape by the following surface treatment. The surface treatment is not particularly limited, but a non-abrasive treatment is preferable.

One method of the surface treatment includes, for example, a method of performing a heat treatment at a sintering temperature of 85% or more of the sintering temperature, preferably a sintering temperature of 70% or more. Heat treatment (percentages are calculated in degrees Celsius). In the case of the above zirconia, 1200 to 145
A method in which a grain boundary is corroded by performing a heat treatment in a range of 0 ° C. for 10 minutes to 2 hours to provide appropriate surface undulations is preferable. The heat treatment condition at this time may be that the oxide may be in the air or in a non-oxidizing atmosphere, or may be under atmospheric pressure or under pressure.

Further, another method is a method of chemically eroding grain boundaries by immersing the same in an acid or basic corrosive solution to provide surface irregularities. Preferably p
An acidic solution of H2 to 4, a basic solution of pH 8 to 12, and the like are included.

Alternatively, the heat treatment may be performed under a hot isostatic pressure, preferably, under a condition of 500 to 2000 kg / cm ² under a hot isostatic pressure.

The ceramic ball obtained by the above method can be used for a ballpoint pen ball, particularly a water-based ballpoint pen ball.

Next, a general method of manufacturing a ballpoint pen will be described. A ball-point pen holder processed into a predetermined size and shape from a metal rod is drilled in a stepwise manner from one end thereof to provide an ink introduction hole. Further, broaching is performed with a cutting tool having feather blades at five or six places, and a cut is formed in the seat to form an ink groove.

After cleaning the seat and removing cutting chips, etc.,
The ball is driven in with a hammer, and the ball is exposed about 30% of the diameter from the tip of the seat, and caulked with an anvil to prevent the ball from jumping out. Thereafter, the tube is filled and ink is introduced. For the seat, nickel silver or stainless steel is used.

Next, a method for measuring the surface roughness will be described.

Since the surface roughness of the ballpoint pen ball is 0.1 μm or less in terms of the center line average roughness, there is a limit in the detection accuracy in a method of measuring using a stylus type or an optical phase difference such as a laser. For this reason, a method of measuring the surface roughness by using an atomic force microscope or a scanning electron microscope having a plurality of detectors is preferable because highly accurate measurement can be performed with good reproducibility.

Here, a method of measuring the surface roughness using an atomic force microscope will be described in detail. An atomic force microscope is a microscope that measures a fine shape of a sample surface three-dimensionally in a non-contact manner. It utilizes the van der Waals force that acts between the sample and the probe at the tip of the cantilever. The probe has a pyramid-shaped projection. By bringing the sample close to the apex, repulsion between atoms acts, and the cantilever bends. The sample is scanned in the horizontal direction while controlling the sample height so as to keep the deflection constant. At this time, the three-dimensional shape of the sample surface can be drawn on the image from the control signal in the height direction. The deflection of the cantilever is detected by utilizing a change in the direction of reflection of the laser beam. Since the atomic force microscope does not require the coating of the conductor film, which is necessary for a normal scanning electron microscope, it is possible to perform more accurate measurement.

[0033]

The present invention will be specifically described below with reference to the following examples. However, the present invention is not limited to this.

Example 1 (Ceramic Slurry Composition) (1) Inorganic Powder Yttria partially stabilized zirconia (ZrO ₂ added with 2.75 mol% of Y ₂ O ₃ ) having an average particle size of 0.12 μm was used as a raw material powder. Using.

As a sintering aid, 0.375% by weight of Al ₂ O ₃ (average particle size: 0.01 μm) was added to the powder.

(2) 5% by weight of polyvinyl alcohol was added to the binder.

(3) Pure water was used as a solvent (Production of ceramic balls) Balls for ballpoint pens were formed by a rolling granulation method. Here, pure water was sprinkled while rolling the dry powder raw material using a rotating container to produce spherical pellets having a diameter of 0.7 mm.

[Sintering and Processing Method] The formed pellets are fired at 1400 ° C. for 1 hour in the atmosphere,
A dense sintered body could be obtained. The finish was polished using a double-sided honing machine and finally finished to a mirror surface with a maximum roughness of 0.03 μm.

The mirror-finished ball was subjected to a heat treatment at 1350 ° C., which is lower than the sintering temperature, for 30 minutes in the air, so that an appropriate surface undulation could be provided.

(Surface Roughness and Structure of Ceramic Ball) The surface roughness of the ceramic ball obtained in Example 1 was measured by an atomic force microscope. Center line average roughness is 5.4
In nm, the maximum roughness was 78 nm. In addition, on the surface of the observed ball, there was no polishing scratch having a width of 0.5 μm or more, a depth of 0.35 μm or more, and a length of 10 μm or more.

The crystal structure of the ceramic ball of Example 1 was analyzed by powder X-ray diffraction. As a result, the ceramic ball was tetragonal zirconia substantially free of monoclinic crystal, the Vickers hardness of the ball was 1350, and the crushing load was Is 0.5mm diameter 2
50 Newton, 430 Newton at 0.7mm diameter,
It was 750 Newton with a diameter of 1.0 mm.

(Evaluation of Ballpoint Pen) Even after the writing taste test of 1000 m, there was no blurring or bleeding of the ink, and almost no ball sink phenomenon was observed. As a result of removing the ball from the seat and measuring the surface roughness, the center line average roughness was 5.
At 6 nm, the maximum roughness was 74 nm, not much different from the initial surface roughness.

Example 2 (Composition of Ceramic Slurry) (1) Inorganic Powder Silicon carbide having an average particle size of 0.78 μm was used as a raw material powder.

As a sintering aid, 0.75% by weight of B ₄ C (average particle size: 1.2 μm) and 0.375% by weight of Al ₂ O ₃ (average particle size: 0.01 μm) Was added.

(2) 5% by weight of polyvinyl alcohol was added to the binder.

(3) Pure water was used as a solvent (Production of ceramic balls) Balls for ballpoint pens were formed by a rolling granulation method. Here, pure water was sprinkled while rolling the dry powder raw material using a rotating container to produce spherical pellets having a diameter of 0.7 mm.

[Sintering and Processing Method] The formed pellets were fired at 2150 ° C. for 1 hour in an argon atmosphere to obtain a dense sintered body. The finish was polished using a double-sided honing machine and finally finished to a mirror surface with a maximum roughness of 0.03 μm.

The ball finished to a mirror state is 2000 ° C.
For 30 minutes in an argon atmosphere under atmospheric pressure, thereby providing appropriate surface undulations.

(Surface Roughness and Structure of Ceramic Ball) The surface roughness of the ceramic ball obtained in Example 2 was measured by an atomic force microscope. Center line average roughness is 5.8
In nm, the maximum roughness was 84 nm. In addition, on the surface of the observed ball, there was no polishing scratch having a width of 0.5 μm or more, a depth of 0.35 μm or more, and a length of 10 μm or more.

The ceramic ball of Example 2 had a Vickers hardness of 2300 and a crushing load of 21 mm for a 0.5 mm diameter.
0 Newton, 380 Newton at 0.7 mm diameter, 1.
It was 700 Newtons with a 0 mm diameter.

(Evaluation of Ballpoint Pen) Even after the writing taste test of 1000 m, there was no blurring or bleeding of the ink, and almost no ball sink phenomenon was observed. As a result of removing the ball from the seat and measuring the surface roughness, the center line average roughness was 6.
At 3 nm, the maximum roughness was 86 nm, not much different from the initial surface roughness.

Comparative Example 1 The procedure of Example 1 was repeated, except that the mirror-finished ball was not heat-treated at 1350 ° C. for 30 minutes to provide proper surface undulations.

(Surface Roughness and Structure of Ceramic Ball) The surface roughness of the ceramic ball obtained in Comparative Example 1 was measured by an atomic force microscope. Center line average roughness is 35n
m and the maximum roughness was 40 nm. In addition, on the surface of the observed ball, there was no polishing scratch having a width of 0.5 μm or more, a depth of 0.35 μm or more, and a length of 10 μm or more.

(Evaluation of Ballpoint Pen) The roughness of the ball surface was too small, and the portion in contact with the seat increased, blocking the introduction of the ink.

Comparative Example 2 Polishing was stopped halfway and the mirror was not finished.
Example 1 was repeated except that no heat treatment was performed at 0 ° C. for 30 minutes.

(Surface Roughness and Structure of Ceramic Ball) The surface roughness of the ceramic ball obtained in Comparative Example 2 was measured by an atomic force microscope. Center line average roughness is 80n
m, the maximum roughness was 150 nm. In addition, many polishing scratches having a width of 0.5 μm or more, a depth of 0.35 μm or more, and a length of 10 μm or more were observed on the surface of the observed ball.

(Evaluation of Ballpoint Pen) Since the polishing was insufficient, the ball rattled and smooth rotation was not obtained. After writing taste test of 1000m, fading of ink,
Bleeding occurred, and the phenomenon of ball sink was observed.

Claims (8)

[Claims] 1. A center line average roughness of a ball having a width of 0.5 μm or more, a depth of 0.2 μm or more, and a length of 10 μm or more and 100 μm ² without polishing scratches on the surface of the ball. A ceramic ball for a ballpoint pen, having a thickness of 4.5 nm to 10 nm and a maximum and minimum roughness of 50 to 100 nm. 2. An arbitrary 2500 on the surface of the ball.
^2. The ceramic ball for a ball-point pen according to claim 1, wherein the number of said polishing scratches is 2 or less in a range of μm ² . 3. The ball material has a Vickers hardness of 1100.
The ceramic ball for a ballpoint pen according to claim 1, wherein the ceramic ball is made of any one of alumina, mullite, zirconia, silicon nitride, silicon carbide, and a composite ceramic sintered body thereof. 4. A method for producing a ceramic ball, comprising: forming a ceramic powder into a ball shape, sintering the resultant, polished to a mirror surface having a surface roughness of 50 nm or less, and further imparting an uneven shape by surface treatment. 5. A method for producing a ceramic ball, wherein the surface treatment is performed by heat treatment at a sintering temperature of 85% or more of the sintering temperature. 6. A method for producing a ceramic ball, wherein the heat treatment is performed by heat treatment under hot isostatic pressure. 7. A method for producing a ceramic ball for a ball-point pen, wherein said surface treatment is performed by immersion in an acid or basic corrosive solution. 8. A ballpoint pen using the ceramic ball for a ballpoint pen according to claim 1.