FR2630969A1 - WRITING TIP FOR WRITING FLUID INSTRUMENT - Google Patents

Abstract

The invention relates to a writing tip for a liquid writing instrument. According to the invention, a surface hardened layer 3 is formed on the surface of the writing tip 2 which is made of a thermoplastic resin and which contains an ink conductive space 1, the layer 3 comprises one or more films chosen from a metal, or an oxide, nitride, carbide or silicide of this metal, deposited by a low temperature plasma method. The invention applies in particular to writing nibs subjected to high pressure.

Description

The present invention relates to a writing tip having a space

ink conductor. More particularly, the present invention relates to a writing tip for a writing liquid instrument having a remarkably extended writing life and allowing smoother writing with its better wear resistance compared to the tips.

conventional writing.

Traditionally, most of these writing tips are made by extrusion molding.

a thermoplastic resin, and the thermo-resin

plastic generally contains a single substance of polyamide, polyurethane, polyacetal, etc., or else a composite material of one of these resins mixed with

a load.

These conventional writing tips have the disadvantage that they wear out a great deal compared to the sliding friction during writing, although liquid ink, etc., serves as a lubricating agent, and in particular when a liquid ink is used. high writing pressure is applied or when using high surface roughness writing paper, this tendency is evident; in fact, all the resins used for conventional writing tips have insufficient resistance to wear, which adversely affects the writing life of the tips. When a writing tip has insufficient wear resistance, this poses a problem as described below when designing a liquid writing instrument. The problem is that the ink remaining in an ink absorption tank

and the life of a writing tip are unbalanced.

released, rendering the liquid writing instrument unusable because the writing life of the tip has ended although there is a sufficient amount of ink remaining in the ink absorption reservoir. Accordingly, it is unnecessary to attempt to extend the life of a writing instrument remarkably by forming an ink absorption reservoir in the form of a cartridge. In order to improve the wear resistance of a writing point, there is a method of manufacturing this point, for example, in glass, ceramic or certain metals, but this has a disadvantage in that the point obtained only allows very little flowing writing in comparison with a plastic point. In particular, there is a tendency for the writing tip to move less smoothly on the paper as the line width of the written images decreases. This also has disadvantages in that the point is blocked or the lines are interrupted by the paper fibers which make

intrusion into the conductive space of the ink.

it is therefore an object of the present invention to solve the problems of conventional writing tips by providing a writing tip for a liquid writing instrument which has a remarkably extended writing life with improved resistance to writing. 'wear and also move smoother on the paper, which can be inexpensively manufactured by a process

industrially simple and easy.

According to the present invention, a writing tip for a liquid writing instrument having good writing ability, in particular high wear resistance and allowing smooth writing, can be obtained by depositing a hardened layer in surface comprising one or more films selected from a metal, or an oxide, nitrous, carbide or silica thereof on the surface of a writing tip made of a thermoplastic resin having an ink conductive space, which the this is obtained by a conventional method using a low temperature plasma method. Examples of low temperature plasma methods which are suitable for forming this layer on the surface of a writing tip include a well known spray deposition method, an ion plating method, a chemical vapor deposition method. plasma, etc., but in the present invention, the low temperature plasma method is not limited to the above-mentioned methods and the surface of the

writing tip can be processed repeatedly.

In the low temperature plasma method, the tip surface is preferably treated near room temperature so that the temperature of the writing tip can be kept below the softening point of the thermoplastic resin used on the tip. this tip as a substrate on which a film is deposited in order to prevent a conductive space of the ink from being thermally deformed. The resulting film has

normally a very smooth surface.

Using the above-mentioned process, most metals, including those with a high melting point, can be deposited in the form of a film, but according to the present invention, a metal of high surface hardness is preferably chosen. and high wear resistance. An alloy made from two or more metals can also be used. A film of a metal compound of an oxide, nitride, carbide or silicide of said metal is obtained by introducing gaseous oxygen, gaseous nitrogen, a gaseous compound of nitrogen, a gaseous hydrocarbon or a compound of silicon gas as a reactive gas in plasma. In certain treatment processes, inorganic or organic metal compounds can be introduced into

as a reactive gas in the plasma.

The writing tip according to the present invention, on the surface of which is deposited a surface hardened layer comprising one or more films chosen from a metal or an oxide, nitride, carbide or silicide of this metal by a low temperature plasma method , has the following advantages: 1 - the writing tip has a high resistance to wear during writing because its surface is covered with a film much harder than the substrate made of

thermoplastic resin.

2 - the hardened film which covers the surface of the writing tip normally has a very smooth surface with a low coefficient of friction, so the tip

to write runs easily on paper.

3 - as the writing tip has a plastic structural member, this allows smooth writing in comparison with those made of glass, ceramic or

some metals.

4 - the hardened film on the surface of the writing tip is usually formed after cleaning the substrate of the writing tip by spraying ions such as argon, etc., whose atoms collide with the substrate to a high energy, and the film that is formed is still subjected to the impacts of ions. As a result, the cured film can be easily mixed and diffused with the substrate material and therefore adheres very strongly to the writing tip substrate without easily chipping when writing. the formation of a cured film generally requires high technology and expensive equipment. But in the present invention, a surface hardened layer is formed on a very small area of a writing tip, thus it has an advantage that mass processing allows reduction.

remarkable in the price of writing point processing.

The invention will be better understood, and other objects, features, details and advantages thereof

will appear more clearly during the description

explanatory which will follow made with reference to the appended schematic drawing given solely by way of example illustrating one embodiment, and in which: - the single figure is a cross-sectional view taken through a writing tip according to

one embodiment of the present invention.

According to one embodiment of the invention, a writing tip 2 having an ink-conducting space i having an unusually shaped section, for example cruciform, as shown in the figure, has been molded from a heated polyacetal and melted by conventional extrusion, then a 2m thick tungsten film 3 was formed on the surface of the tip 2 by

a well known spray depSt method.

The conditions of film formation are such that a direct current is discharged at a pressure of 6.65 x 10-6 bar and at a temperature of the substrate near room temperature, using argon gas as the plasma source and tungsten

metallic as a target. -

It was possible to confirm by observations with a scanning electron microscope that the tungsten film thus obtained was formed very regularly and

without damaging the conductive space of the ink.

the writing tip obtained as described above was mounted in the writing instrument, the tip wear was measured by means of a mechanical writing test machine and the writing test The fluent writing was performed by sensory evaluation by skilled hands. The results of the measurements and the test are shown in the table below. In the comparison example, a writing tip without a surface hardened coating was used. According to another embodiment, a writing tip made of polyacetal of the same shape as in the first embodiment was used as the substrate.

and a titanium nitride film about 2 µm thick

sor was formed on the surface of the tip by the method

well-known ion plating.

The film forming conditions are such that a direct current is discharged at a pressure of 4 x 10 bar and at a substrate temperature near room temperature using argon gas as the plasma source, metallic titanium as the target and using nitrogen gas as the reactive gas. It was possible to confirm, by observation with a scanning electron microscope, that the film thus obtained of tungsten was formed very regularly and

without damaging the conductive space of the ink.

The writing tip obtained as described above was mounted in the writing instrument and was subjected to the same tests as in the first embodiment. The results are shown in the table below. A writing tip of a third embodiment, made of polyacetal of the same shape as in the first embodiment was used as the substrate.

and a silicon nitride film of about 2 .mu.m thick

If it has been formed on the surface of the tip by a well known chemical vapor deposition method, the film forming conditions are such that a high frequency current is discharged at a substrate temperature equal to room temperature using a mixed gas of silane, ammonia and nitrogen as a reactive gas. It was possible to confirm, by observation with a scanning electron microscope, that the film thus obtained of tungsten formed very regularly and without

damage the unusually shaped section.

The writing tip obtained as described above was mounted in the writing instrument and was subjected to the same tests as those of the first embodiment. The results are shown in the table below.

BOARD

JExample of Mode Mode Mode

. Example of

PoirLs TESTS realiza- real isa-

1 LioIn 2 L JiOn 3

Number of echlan

UsureL tllo-ns 20 20 20 201 jlJmJre J. tin (afterVl3] etur average 0.90, 10mm (Jf13 im F1.05 min dl'P ('> cri Ltur) standard deviation 0, (J5 fimm in 0, 06 mi 0.006 mm l, (05 mmin rcfri- Nullbihre de moyels; to assess1. Ni 1 ,. 11re_ _, I

C JII- Mi elx that the example of coii-

paraisitii oil 7 8 B I) if icirle to be evaluated 3 2 2

Worse than the example of Compa-

rai soi i so1) 1 Note) in the wear test, the writing test with a mechanical typewriter is carried out under the conditions of Japanese standard "JIS-S-6037-1986 Making Pen" except that a write load of 0.981N is applied. The writing tip according to the present invention, on the surface of which is deposited a surface hardened layer comprising one or more films selected from a metal or an oxide, nitride, carbide or silicide thereof, by a plasma method using low temperature has significantly improved wear resistance and allows smooth writing even for a long time, as can be seen from the test results described above, while conventional tips with a sufficient amount of ink remaining become unusable after a short writing distance. The point according to the present invention is particularly advantageous when a high writing pressure is applied to it or when a paper with a high surface roughness is used. It is also very useful in combination with various types of recorders where a writing tip must have a long life. A cartridge type marking pen will also have practical application using the writing tip according to the present invention. As described above, the tip according to the present invention has

a large number of beneficial effects.

Claims (1)

RESELL I CATION A writing tip for a liquid writing instrument, characterized in that a surface hardened layer (3) is formed on the surface of the tip (2) made of a thermoplastic resin having a conductive space (1) of l ink and said layer comprises one or more films selected from a metal or an oxide, nitride, carbide, or silicide thereof, deposited by a low temperature plasma method.