JPS59213735A - Method for plasma treatment - 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 relates to a method of etching a polymeric sheet material using low temperature plasma.

Previous research has focused on forming a rough surface by etching the surface of polymer sort materials to improve adhesion, darken the color of dyed products, improve texture, improve gloss, or prevent blocking. However, there are few research examples of etching a polymer sheet-like material by low-temperature plasma treatment to form a rough surface, and even more so, there is no method of continuous etching treatment using low-temperature plasma generated between asymmetric internal electrodes. It is no exaggeration to say that there are no research examples regarding this. The method of etching materials using low-temperature plasma has been widely used in the field of electronic material parts such as semiconductors in recent years, but in these cases, gases such as CF4 are mainly used to react with Sl (silicon). It is used to gasify and perform etching. In some of the processing methods in these cases, the object to be processed is rotated on the electrode, but in most cases the object is fixed on the electrode, and there is no method in which the object is continuously moved on the electrode. The electrode shape is mainly a circular parallel plate, and is a symmetrical electrode. This is because, since the object to be processed is fixed on the electrode, an asymmetrical electrode causes a distribution in the electric field and does not produce homogeneous plasma, resulting in differences in the etching level. That is, homogeneous etching with asymmetric electrodes is possible only when the object to be processed can be continuously moved between the electrodes.

The inventors of the present invention have conducted extensive research for many years on a method for etching polymer sorted materials using low-temperature plasma generated by an asymmetric internal electrode system.

The present invention provides: 1. An asymmetrical electrode in which the discharge surface area of one of the high voltage side electrodes is 11500 to 1/10 of the total surface area of the ground side electrode, and the high voltage side electrode A plasma processing method characterized in that the treatment is performed using low-temperature plasma generated between internal electrodes whose total surface area is 01 times or more and 2.5 times or less the total surface area of the ground side electrode.

2. The gas during low-temperature plasma discharge is oxygen or a mixed gas containing oxygen, and the degree of vacuum P is 0.05 to 1. O.T.
orr, inter-electrode distance d between the high voltage side electrode and the ground side electrode
is 1 crn or more and ioz or less, and 0.05 < P-d
5. The plasma processing method according to claim 1, wherein < 5 (Torr xan).

In the present invention, 15 polymer sheet-like materials refer to sheet-like materials such as resins, molded products, films, cloth, etc. made of synthetic polymers, natural polymers, etc., but they do not necessarily include one type of polymer sheet. It does not necessarily have to be made of composite, nokuimetal, glued, blended, copolymerized, twisted, mixed knitted, mixed woven, mixed fiber, etc., and may also contain a suitable plasticizer or kneaded material inside. , a matting agent, etc. may be included. Further, other polymeric substances, decomposed substances, inorganic substances, or a mixture thereof may be attached to the surface of the sheet-like article.

Plasma is classified into two types: high-temperature plasma and low-temperature plasma, and the term "plasma" used in the present invention refers to low-temperature plasma.

Low-temperature plasma is characterized by the plasma generated during discharge having an average electron energy of 10 eV (104-106 K) and an electron density of 109-1012 crII-3, and at the same time, there is a reason why no equilibrium is established between the electron temperature and the gas temperature. In addition, in an O discharge, which is also called a non-equilibrium plasma, the plasma layer A generated is a mixture of electrons, ions, atoms, molecules, etc.

Low-temperature plasma involves continuously introducing gases such as argon, nitrogen, hydrogen, oxygen, air, carbon oxide, carbon dioxide, etc. into a system with a vacuum degree of 0.01 to 10 Torr.
Produced by applying voltage between electrodes. Any frequency power source can be used to apply the voltage. In terms of continuity and uniformity of discharge, I KHz -: l
Q Gt (z is desirable. Also, from the viewpoint of plasma uniformity in the width direction of the electrode, IKHz to I MHz is preferable,
When the frequency is higher than 1 MHz, if the length of the electrode exceeds 1 m, processing spots are likely to occur in the length direction. Furthermore, at frequencies below 100 Hz, edge effects tend to occur, and arc discharge tends to occur at edge portions. Further, as the current, alternating current, direct current, biased alternating current, pulse waves, etc. can be used, but direct current is not very desirable in terms of etching efficiency. There are two types of electrodes: internal electrodes placed inside the vacuum system and external electrodes placed outside the vacuum system. Since the concentration is diluted and the etching effect is small, it is not suitable for etching, and the present inventors have investigated a processing method using an internal electrode method. In this case, the electrode shape does not necessarily have to be symmetrical. In the case of a large plasma processing apparatus where the processing area is large and therefore a large electrode is required, symmetrical electrodes have more disadvantages. For example, it is almost impossible to flow gas uniformly between large electrodes, and the electric field is likely to be disturbed at the ends of large electrodes, resulting in uneven etching. Therefore, in the case of a large-scale plasma processing apparatus, it has been found that an asymmetrical electrode, particularly a type in which the discharge surface area of one high voltage side electrode is smaller than the total surface area of the ground side electrode, is preferable.

As shown in FIGS. 1 and 2, the discharge surface area of one high voltage side electrode refers to the remaining area excluding the surface area of both end faces, and in both FIGS. 1 and 2, πr! It is expressed as Next, the total surface area of the ground side electrode refers to the remaining area excluding the surface area of the end surface as above, and is πRL in Figure 1 and 8x in Figure 2.
Point to RL. High voltage 11 again! l What is the total surface area of the electrode?
It is a value obtained by multiplying the discharge surface area of one high voltage side electrode by the number of high voltage side electrodes, and is 12Xπrl in the case of FIG. 1 and 12 x yrrl in the case of FIG. 2.

According to the study results of the present inventors, the discharge surface area of one high voltage side electrode is 11500-1% compared to the total surface area of the ground side electrode.
/10 has good etching efficiency and uniform plasma is formed. Preferably 1. /20 to 1/1 (10. If this ratio is less than 11,500, the electrode becomes very thin (thin), generates a lot of heat, and is difficult to cool [K
Therefore, temperature control is difficult, and etching spots are likely to occur in the length direction due to temperature changes. If the voltage is higher than IAO, the portion of the high-voltage side electrode that does not face the object to be treated becomes large, resulting in poor discharge efficiency and a tendency for gas flow to become uneven.

However, if only one high-voltage side electrode satisfies the above conditions, the electric field exerted on the ground side electrode is uneven and weak, and therefore the etching effect cannot be sufficiently exerted. Therefore, by arranging several to several hundred high voltage electrodes at a certain distance from the grounded electrode, the distribution of the electric field becomes uniform, and at the same time, the plasma becomes uniform, effectively spreading the plasma over the surface of the workpiece and increasing the etching efficiency. Significantly improved.

The total surface area of the high voltage side electrode is 0.1 to 0.1 of the total surface area of the ground side electrode.
2.5 times is preferable. If it is less than 0.1, the electric field on the ground side electrode is non-uniform and weak, and the plasma is also non-uniformly distributed, resulting in poor etching efficiency. When it is 2.5 times or more, the gas flow becomes non-uniform, which tends to cause etching spots.

Preferably it is 0.5 to 1.0 times.

The shape of the high voltage side electrode may be a cylinder or a rod with a polygonal cross section having an acute angle, but a cylinder is preferred.

As for the shape of the ground side electrode, it is possible to use a drum shape, a plate shape, or a modified shape thereof. In short, the shapes and combinations of both electrodes are not limited as long as they satisfy the above conditions.

Next, the gas to be introduced into the vacuum thread should be introduced with a supply port as far away as possible from the exhaust port of the vacuum pump. This is important in order to avoid a gas bath in the vacuum system, and is also important in order to prevent etching spots on the object to be processed. The types of gases that had good etching efficiency were oxygen and a mixed gas containing oxygen. From this, it is presumed that the surface roughening mechanism of polymer etching by low-temperature plasma is a reaction involving oxidative decomposition.

The degree of vacuum that generates low-temperature plasma is usually 0.0.
1 to IQ'f'orr is used, but according to the study results of the present inventors, it is 0.05 to 1. □ Torr is preferable.

When the degree of vacuum is below Q, Q 5 Torr, the mean free path of ions and electrons increases and the energy of accelerated particles increases, but the total number of accelerated particles that reach the object to be processed is small and the etching effect is not good. . Furthermore, in order to maintain the temperature of a large processing chamber at 0.05 Torr or less while introducing gas, a vacuum pump with a very large displacement is required, which is not desirable in terms of equipment cost. The degree of vacuum is l
When the temperature exceeds Torr, the mean free path of ions, electrons, etc. becomes smaller, and the energy of accelerated particles becomes smaller.
Although the total number of accelerated particles is large, the etching efficiency deteriorates.

Thinking in this way, the mean free path of an accelerated particle, in other words, the degree of vacuum P that determines the distance over which a charged particle is accelerated by an electric field and the number of accelerated particles, and the degree of vacuum P that determines the number of accelerated particles, and the accelerated particle loses its energy or activity. It is conceivable that some optimal relationship exists between the inter-electrode distance d between the high voltage side electrode and the ground side electrode, which determines the probability that the process can be reached without any damage. As a result of considering this point, 1≦d
≦10 (ci) and 0.05 < P4 < 5
It has been found that the etching efficiency is particularly good when the degree of vacuum and the distance between the electrodes satisfies (Torrxcm). In other words, the etching efficiency was good when d was set small when the pressure was high, and when d was set large when the pressure was low.

Furthermore, regarding the relative position of the cloth placed between the electrodes, the etching efficiency can be improved regardless of whether the cloth is placed in contact with the sieve pressure side electrode or in contact with the ground side electrode.

Naturally, in these cases, etching is limited to the portions of the sheet that are not in contact with the electrodes.

When a sheet-like material is disposed at an intermediate position between the high-voltage side electrode and the ground-side electrode, the etching surface becomes a screen of the sheet-like material, but the etching efficiency is not good. Considering this phenomenon from the discharge characteristics, it can be explained by the voltage drop characteristics between the two electrodes. It is said that the voltage drop characteristics between the two electrodes are the largest near the ground side electrode, followed by the high voltage side, and the voltage drop near the middle of the two electrodes is small, and this voltage drop f is the strength of the electric field. This is probably because the part with the larger voltage drop can give more energy to the charged particles.

Next, the question is whether the cloth should be placed in contact with the high voltage side electrode or the ground side electrode. Directional force in contact with 5 Desired 0 Regarding heat generation, the high voltage side electrode generates more heat;
For this reason, it is desirable to arrange the sheet-like material in contact with the ground-side electrode in order to prevent the sheet-like material from hardening or to change its texture. Of course, it is possible to cool the electrode, but
If you think about it from a device standpoint, it's a little complicated. Further, it goes without saying that a device that continuously moves a sheet-like object in contact with a high-voltage side electrode is more complicated than a device that moves a sheet-like object in contact with a ground-side electrode. This is because it is better to ground the can body for stability, and since the high voltage side must be insulated from the can body, driving it becomes complicated in terms of equipment.

Next, in terms of etching uniformity, the high voltage side electrode must be held parallel to the ground side electrode, and must also be placed at right angles to the direction of movement of the polymer sheet material to be processed. 0 If this condition is not satisfied, unevenness due to cutting and pinching will occur in the middle direction of the sheet-like material. Furthermore, the high voltage side electrode must be at least 5 tyn longer than the width of the polymer sheet to be treated. This is to eliminate electric field non-uniformity at the end of the high voltage side electrode. If this length is less than 5 CrIT, the degree of etching in the width direction of the sheet-like material, particularly on both sides, will be different from that near the center, which is undesirable.

In the present invention, the sheet-shaped material moves in contact with the grounded electrode, which means that this device can continuously move and process polymer sorted materials in the atmosphere into a vacuum system, and polymer sheet-like materials These include those that are placed in the preliminary vacuum system and can be moved to the processing chamber, and those that have a polymer sheet-like material placed as a partition in the processing chamber. Anything that can be moved is fine.

The surface morphology of the polymer sheet obtained by these etching treatments varies depending on the type of polymer, internal fine structure, degree of orientation, direction of orientation, etching time, etc. For example, in the case of polyester, when observed with a scanning electron microscope, a biaxially stretched film has a so-called honeycomb structure. , resulting in ridge-like irregularities perpendicular to the orientation direction.

Films subjected to these etching treatments have good adhesive properties, and in particular, adhesive strength is significantly improved. Furthermore, in the case of fibers, a squeaky feel can be obtained, and especially when etching dyed materials, a remarkable color deepening effect can be obtained, and furthermore, the gloss can be improved. It is also possible to improve the frictional properties, transparency, etc. of the sheet-like material.

In addition, if the electrodes are arranged so that the high voltage side electrode is covered with the ground side electrode, there will be no discharge between the high voltage side electrode and the can body (grounded), and a discharge will occur between the high voltage side electrode and the ground side electrode very effectively. It was found that the etching efficiency was improved approximately twice. An example of this type of device is shown in FIG.

This will be explained below based on an example.

Examples and Comparative Examples Biaxially stretched films of polyethylene terephthalate are shown in Table 1.
Plasma treatment was performed under each of the following conditions, and defects in Table 1nj were observed using a scanning electron microscope and an ultrathin section transmission electron microscope. Power frequency is 150 Kfiz, output 10KW'
, 5o=7200 mA, discharge time 3 minutes, cloth speed 0
．． 33 m/min S+: Surface area of one 4 voltage side electrode (==='l) S: Total surface area of high voltage fl11 electrode (crA) SO: Total optical area of ground side electrode (CIA) P: Degree of vacuum (Torr ) d: Distance (picture) between high voltage side electrode and ground side electrode a: Length and width of high voltage side electrode) - Polymer sheet-like material 1] (cr
n) From Example 1.2 and Comparative Example 1.2, the surface area Sl of one high voltage side electrode is 15% compared to the total surface area SO of the ground side electrode.
It can be seen that the etching efficiency is good for values from 00 to "/io".

According to Examples 3 and 4.5 and Comparative Example 3.4, the total surface area of the high voltage side electrode is 0.1 to 2.0% of the total surface area of the ground side electrode.
It can be seen that the etching efficiency is good when the ratio is 5 times.

It can be seen from Example 4.6 and Comparative Examples 5.6 and 7 that oxygen or a gas containing oxygen is desirable.

From Example 7.8.9.10 and Comparative Example 8.9, the preferred condition for etching efficiency is a vacuum degree of 0.05 to 1.
．． It can be seen that the distance d between the electrodes is 1 to 10 crn1 and the value of P-d is 0.05 to 5 Torr, crnte (from Example 11 and Comparative Example 10, the length and width of the high voltage side electrode)
It can be seen that unless the width is at least 5 m or more longer than the width of the polymer sheet to be treated, etching spots will occur at both ends of the cartridge due to the edge effect.

Example 12 shows the case where the etching process was performed using an apparatus (Fig. 2) in which the high-voltage side electrode was covered with the ground side electrode, but compared to Example 4 (when the etching was carried out using the apparatus shown in Fig. 1). It can be seen that approximately twice as many etched moving parts were obtained. Furthermore, the surface condition of the films obtained in these Examples and Comparative Examples was determined by scanning electron microscopy to be a non-nicum structure.

[Brief explanation of drawings]

1(a) and 2(a) are schematic diagrams of an example of an apparatus for carrying out the method of the present invention, and FIG. 1(b) and FIG.
b) is a schematic diagram for explaining the high voltage side electrode and the ground side electrode as seen from the side of FIG. 1(a) or FIG. 2(a), respectively. Further, FIG. 3 is a diagram illustrating voltage drop characteristics between electrodes. 1...Polymer sheet-like material 3...High voltage side electrode 2...Grounding side electrode 4...Power supply patent applicant Rira Co., Ltd. Representative patent attorney Ken Honda

Claims (1)

[Claims] 1. The discharge surface area of one high voltage side electrode of the polymer sheet-like material is 11500 to 1/10 of the total surface area of the ground side electrode.
The treatment is performed with low-temperature plasma generated between the internal electrodes, which are asymmetric electrodes having a ratio of plasma treatment method. 2. The gas during low-temperature plasma discharge is oxygen or a mixed gas containing oxygen, and the degree of vacuum P is 0.05 to 1. □T
orr, the distance d between the high voltage side electrode and the ground side electrode is 1 m or more 1:1 (lcnn or less, 0.05 <
The plasma processing method according to claim 1, characterized in that p-a (5 (Torrxcm)).