JPS58138698A - Pen ball for ball pen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a pen ball for a ballpoint pen with excellent properties,
In particular, it relates to bembol made of zirconia sintered body.

In general, materials for ballpoint pens are not only characterized by abrasion resistance, corrosion resistance, and mechanical strength, but also by good workability that provides precise sphericity, surface smoothness when used as a product, and good writing characteristics. requested.

Until now, cemented carbide such as tungsten carbide, ruby, etc. have been used as materials for ballpoint pen balls, but recently, as a result of the development of new materials, ceramics such as alumina sintered body have attracted attention. It's starting to be done. However, although this alumina ceramic meets the above requirements in terms of wear resistance and corrosion resistance, it lacks impact resistance, so it may chip or crack when subjected to impact when processed into balls or when writing. In addition, it is difficult to obtain high sphericity due to poor polishability, and it also has the disadvantage of poor writing characteristics when used as a ballpoint pen, posing many practical problems.

The present inventors have overcome these drawbacks of conventional ceramic pen balls and developed a ceramic pen ball that has excellent wear resistance and corrosion resistance, has good impact resistance and writing characteristics, and is easy to process. As a result of extensive research for this purpose, it was discovered that the purpose could be achieved by using a certain type of zirconia sintered body, and based on this knowledge, the present invention was completed.

That is, the present invention provides a ball for a ballpoint pen, which is made of a zirconia sintered body containing at least zirconia having a tetragonal crystal structure.

Zirconia has tetragonal, cubic, and monoclinic crystal structures, but in the present invention, zirconia sintered with at least zirconia having a tetragonal crystal structure (hereinafter referred to as tetragonal zirconia) is used. Use concretions. Preferably, 50 mol% or more, especially 70 mol% or more of tetragonal zirconia is used. Particularly preferred is
It is a zirconia sintered body in which all of the zirconia is tetragonal zirconia, or 50 mol% or more of tetragonal zirconia, and the remainder is zirconia having a cubic crystal structure (hereinafter referred to as cubic zirconia). In this way, when a zirconia sintered body contains tetragonal zirconia, the crystal structure transforms from a tetragonal system to a monoclinic system when subjected to an external force. The energy required for this transformation acts to relieve stress, giving the pen ball high mechanical strength.

It is desirable for a pen ball for a ballpoint pen to have as high impact resistance and mechanical strength as possible, and these properties increase as the proportion of tetragonal zirconia in the zirconia sintered body increases. It is advantageous to use a material with a high abundance of crystalline zirconia.

On the other hand, the coexistence of cubic zirconia in the zirconia sintered body improves thermal stability, so its presence can be said to be desirable to some extent. However, when zirconia with a monoclinic crystal structure (hereinafter referred to as monoclinic zirconia) exists, microcracks are usually generated around it when the color changes from a tetragonal crystal structure. When an external force is applied, destruction progresses starting from these microcracks, causing a decrease in mechanical strength.
Even if it does contain it, it is preferable to use it in an amount of 10 mol% or less of the total.

The amount of tetragonal, cubic, and monoclinic zirconia present in such a zirconia sintered body can be determined, for example, as follows.

In other words, to determine the amount of tetragonal zirconia, first measure the surface of the pen ball with an automatic recording type
Analyzed with a line diffraction device, cubic zirconia (400) plane,
Tetragonal zirconia (004) plane and tetragonal zirconia (
220) record the diffraction pattern of the plane on the chart. Next, the area intensity of the diffraction peak of the cubic zirconia (400) plane is determined from this chart, and this area intensity is
Cubic zirconia (4
00) surface, depending on the diffraction angle θ, the formula L = , (1+cos
The diffraction line intensity A of the cubic zirconia (400) plane is determined by dividing by the Lorentz factor calculated according to "2θ)/5in2θ·-θ."

In exactly the same way, from the peak area intensity and diffraction angle of the tetragonal zirconia (004) plane read from the chart and the area intensity and diffraction angle of the tetragonal zirconia (220) plane, The diffraction line intensity B of the ) plane and the diffraction line intensity C of the (220) plane of tetragonal zirconia are determined, and these values are substituted into the following formula to calculate the amount CT (mol %) of the tetragonal zirconia.

In this X-ray diffraction, it is preferable to select diffraction conditions such that the diffraction peaks of each crystal plane do not overlap on the chart. For example, when a copper tube with a nickel filter is used as an X-ray source, the tube voltage and tube current are 24 KV and 10 mA, the rate meter time constant is 4 seconds, and the goniometer rotation speed is 0. .25 degrees/min,
This is achieved by selecting the chart speed to 201IIIZ.

By the way, this method is a so-called simple method, and strictly speaking, it gives an approximate value of the amount of tetragonal zirconia, but there is no particular problem in practical use.

The amount CM (mol %) of monoclinic zirconia can also be determined according to the following formula in exactly the same manner as in the case of tetragonal zirconia.

However, D: Diffraction line intensity of tetragonal zirconia (111) plane E: Diffraction line intensity of monoclinic zirconia (111) plane F: Diffraction line intensity of monoclinic zirconia (nt) plane Next, used in the present invention The zirconia sintered body is 0.1 to 5
It is preferable to have an average crystal grain size of μ, particularly 0.1 to 1 μ. Having such a dense structure provides even higher impact resistance, and when the surface of the ball is line-polished, it makes smooth contact with the paper surface, improving the ink's "wetting to the paper surface." It has the advantage of improving the taste of the paste.It also improves mechanical strength, which reduces breakage during processing and increases the stability of ship quality.

Further, the zirconia sintered body used in the present invention preferably has a porosity of 2% or less, preferably 1% or less. This porosity P (to) is determined according to the following formula.

In this way, making Benball from a zirconia sintered body with low porosity not only further improves impact resistance, but also has extremely minimal minute pore irregularities on the pole surface, which dramatically reduces wear on the holder. However, as a result, the flow of ink on the pole surface is maintained constant, which is preferable because a desirable writing feeling is guaranteed over time.

The zirconia sintered body used in the present invention as described above is
For example, it can be obtained by dissolving a stabilizer such as ittria or calcia in zirconia. This way,・6. By using such a stabilizer, it is possible to perform sintering at a relatively low temperature, so the diameter of the crystal grains can be reduced, and the crystals become denser, making it possible to obtain a sintered body with even higher mechanical strength. It has the advantage of being able to In this case, ittria is 1 to 5 mol% of the total
, calcia is added in a proportion of 1 to 9 mol % to the total. In addition, ittria and calcia can be used together, but in that case, it is better to select so that the total amount of both is within the range of 2 to 12 mol%. The bold type is usually processed into spheres with a diameter of 500 to 1500 μm depending on the purpose of use. This ball is inserted into the holder at the tip of the ballpoint pen, and must be held firmly and rotated smoothly when writing, so high precision is required, and the dimensional tolerance of the reel and diameter must be within a few microns. Also, the difference in diameter between each ball is less than 1μ, and the sphericity is 1
Needless to say, it is not acceptable to have cracks, scratches, rust, holes, etc. on the surface.

The pole of the present invention can be manufactured, for example, as follows.

Pure IN 99.9% Zirconyl Oxychloride (ZrOC
12) and an aqueous solution of yttrium chloride (YCl3) are mixed and prepared such that the molar ratio of zirconia (ZrOa) and yttrium (Y2O3) is 95:5 to 99. Next, this mixed solution is heated slowly until it reaches a temperature of about 200° C., during which water is completely removed, and then further heated and pre-calcined at a temperature of about 1000° C. for several hours. The obtained zirconia sintered body) The IJA mixed powder was wet-pulverized using a ball mill and heated to about 1000°C.
A solid solution powder of ZrO2Y2O3 is prepared by repeating the heating plate firing and pulverizing operations at a temperature of . next,
For example, an aqueous polyvinyl alcohol solution is added to this powder, mixed, and then granulated and dried using a spray dryer to obtain a finely divided raw material powder.

Using the raw material powder prepared in this way and then using a mold forming machine having a mold suitable for molding the required pole, about 50
It is molded at a molding pressure of 0 to 1000 Kg/-. The obtained molded body was heated at a heating rate of 10°C until the temperature reached approximately 1000°C.
After heating at 50 to 1,000 to 1,600 degrees Celsius, the material is held at a temperature of approximately 1,600 degrees Celsius for several hours for sintering. Next, the sintered body is slowly cooled at 200-b until the temperature reaches about 1000°C, 100-b until the temperature is about 600°C, and further cooled in a furnace to room temperature. In this way, a spherical zirconia sintered body is obtained.

The obtained spherical zirconia sintered body is placed in a fireball polisher or barrel polisher and polished for 1 to 4 weeks.
A pole whose ball diameter and sphericity meet the standards is manufactured.

In addition, in the above method, the molded body is not completely sintered, but is fired at a temperature below the sintering temperature, for example, at a temperature of about 1300 to 1400°C, and then subjected to an automatic rough grinding machine to form rough balls. After sintering at a high temperature, it is also possible to process the material into a perfect sphere using, for example, a barrel grinder.

In the above-mentioned sintered body manufacturing process, for example, a zirconia spherical molded body is fired at a temperature of 1200 to 1300°C, and then heated at a temperature of 1400 to 1500°C for several hours under argon gas pressurization of 2000 to 3ooo Kp/d. By using sintering, so-called hot isostatic pressing (HIP), the sintered body can be made even denser and the crystals can be made microcrystalline, which significantly improves the mechanical strength of the sintered ball. At the same time, it is possible to extremely reduce the minute irregularities on the surface to improve the slippage with the paper surface and virtually eliminate the wear of the ball holder. It is highly desirable to adopt

The pole of the present invention, which is formed of the zirconia sintered body containing at least tetragonal zirconia, manufactured in this manner not only has good polishing workability and can be machined into a true sphere, but also has excellent wear resistance. It has significantly improved mechanical properties, such as toughness and impact resistance, compared to conventional balls.

Furthermore, compared to balls made of alumina ceramics or cemented carbide, the free energy of formation of the Bonyl of the present invention is 1 lower, so the chemical reactivity with the paper surface and ink is extremely weak, resulting in excellent corrosion resistance and fine particles on the surface. Since there are few irregularities, the initial clear writing feeling can be maintained forever, and it is possible to provide a high-quality ballpoint pen with excellent writing characteristics.

In addition, in the ball of the present invention, the above-mentioned excellent properties become even more remarkable when the average particle diameter of the zirconia sintered body is in the range of 0.1 to 5μ and the porosity is 2% or less. It is desirable.

Patent applicant: Mitsubishi Lead Ren Co., Ltd. (1 other person) Agent Same form Akira

Claims (1)

[Claims] l A pen ball for a ballpoint pen made of a zirconia sintered body containing zirconia having at least a tetragonal crystal structure. 2. Benball according to claim 1, wherein the zirconia sintered body contains 50 mol% or more of zirconia having a tetragonal crystal structure. 3. The pen ball according to claim 1, wherein the zirconia sintered body has a porosity of 2% or less.