JPS60121613A - Method of forming transparent conductive film - 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] 1. Industrial application field The present invention relates to a method for forming a transparent conductive film.

2 Conventional technology Conventionally, indium oxide (In20g) and tin oxide (Sn
ITO (Indium
A transparent conductive film provided with a tin oxide film is known.

As a technique for forming such an ITO film, sputtering method;
Reactive vapor deposition method according to JP-A-53-30483; JP-A-50-84474, 49-113733 and 49
No. 120877, each publication proposes a soil and stone RF or DC ion blating method; post-treatment methods such as thermal oxidation treatment, oxygen discharge treatment, or oxidation solution treatment.

However, in any of these methods, the obtained IT
O film adhesion and abrasion resistance are poor, and when a polymeric material is used as the substrate, the substrate temperature must be kept low (for example, about 100° C. for polyethylene terephthalate). In this case, the electrical resistance of ITO is higher and the light transmittance is lower than that of a film formed at a high substrate temperature.

In addition, in the sputtering method, since the degree of vacuum is on the order of 10" Torr, the mean free path of flying particles of the film forming material is reduced to several meters, and it is considered that the distance between the substrate and the target can be reduced to improve film formation. It will be done.

However, there are problems in that the particle flight space is limited by the size of the target, the equipment is expensive, and the film forming time is long. RF or DC ion grading methods cannot completely avoid the problem of contamination due to evaporation of metal acid outputs from the ion blating electrode. Furthermore, in the above-mentioned post-processing method, the process becomes messy, which is disadvantageous in terms of work.

3. Eyes of the Invention 11 The object of the present invention is to effectively form a transparent conductive film that has low electrical resistance, high light transmittance, and has improved practical performance such as abrasion resistance, 1i14 heat resistance, and chemical resistance. The purpose is to provide a method.

44 Structure of the Invention That is, the present invention provides a method for forming a transparent conductive film by a vapor deposition method in the presence of an oxidizing gas ionized or activated by a high-frequency discharge device, [where P is the pressure of the oxidizing gas] (Torr), R is the deposition rate (X/5ee
), W is the high frequency discharge power (Wat
t). The present invention relates to a method for forming a transparent conductive film characterized by performing vapor deposition under the following conditions.

5. Examples Hereinafter, the present invention will be implemented and 0 will be explained in detail.

First, with reference to FIGS. 1 and 2, a method for forming a transparent conductive film will be described using a transparent conductive film as an example.

In Fig. 1, the vapor deposition equipment has each chamber 30.31.32.3.
A winding roll 34 and a supply roll 35 for the sheet substrate 1 are arranged in the chambers 30 and 33 on both sides, and the following processing is performed while the substrate 1 is sequentially fed between both rolls. . First, the adsorbed moisture on the substrate 1 is removed by preheating (60°C) in the chamber 33, and then the substrate 1, which has entered the chamber 32 serving as the first vapor deposition tank, is transported by the transport rollers 36 (transported). The speed is iotyn/min ~2 m/m1n
), evaporation source 37 made of silicon oxide or silicon
is heated and evaporated, and oxygen gas is ionized or activated and introduced through the discharge device.

At the position of the halogen heater lamp 39, the evaporation material from the evaporation source 37 surrounded by the deposition prevention plate 40 is deposited as a silicon oxide layer (layer 12) on one surface of the substrate 1.

Then, once the base body 1 is wound up on the roll 34,
The conveyance direction is reversed and the substrate 1 is conveyed from the roll 34 to the roll 35 direction, and in the vapor deposition tank 32, vapor deposition is performed by changing the vapor deposition conditions (starting with the introduction 02 gas pressure) to form the layer 1.
A layer 11 is deposited on top of 2. Furthermore, the substrate 1 is then conveyed from the roll 35 to the roll 34, and the layer 10 is deposited on the layer 11 while changing the deposition conditions. Next, while the substrate 1 is being transported from the roll 34 to the roll 35, two evaporation sources 42a and 42b (or In-8n alloy or I
'r One evaporation source consisting of O) is heated and evaporated,
By ionizing or activating oxygen gas and introducing it through the discharge device 43, IT is applied to the other surface of the substrate 1.
An O transparent conductive film (14 to be described later) is deposited.

The conditions for each vapor deposition are as follows.

Substrate 1: Polymer (polyethylene terephthalate) sheet: Substrate temperature 200°C or less Evaporation source 37: Evaporation material 5 inches (stored in an aluminum crucible, heated evaporation with a heater or electron gun heating) or 5 inches (E gun heating), evaporation Speed: 500 to 2000 X/min□ Discharge device 38: Oxygen gas is introduced at a rate of 20 to 5 occ/min (vacuum degree of 2X10' to 9X10' Torr, ioo to 700W DC or high frequency discharge).

Adhesion prevention plate 40: Prevents abnormal adhesion of evaporation material to the substrate surface.

Evaporation source 42a: In (resistance heating or electron gun heating),
Vapor deposition rate 200 A/min ~ 1000 A/m1n
O Evaporation source 42b: Sn (resistance heating or electron gun heating) Discharge device 43: Introducing oxygen gas at 10 to 6 occ/min (degree of vacuum 5X10'Torr' to 9X10'Torr
, e.g. 7 x 10'Torr; 200-700
W, for example, a high frequency discharge of 400 W) 0 Note that the antireflection layer 13 can also be formed of a material other than Sin or Si0g, and in this case, the deposition may be performed under the following conditions.

Vapor deposition 9 Evaporation material Evaporation method aluminum oxide I'JzOs Electron gun heating, vapor deposition aluminum oxide in 0□ M Heater heating, reaction vapor deposition tin oxide in 0□ 5n02 Electron gun heating, reaction vapor deposition oxidation in 0□ Tin Sn heater heating, reactively vapor deposited indium oxide in 02 ln=0- fit sub gun heating, vapor deposited indium oxide in 0° In heater heating, reactively vapor deposited titanium oxide Ti or Tidy in 0□ electron gun heating, 02(0
<Y≦2) The above-mentioned discharge device 38 or 43 may be configured as a high-frequency discharge tube as shown in FIG. 2. That is, when mounting this high-frequency discharge tube, a through hole (inlet) 50 connected to the gas inlet 46 is formed in the center of the plate 49, and a ring-shaped projection 51 with a small diameter is formed around the inlet 50. A ring-shaped projection 52 with a large diameter is provided concentrically.

A gas introduction pipe 53 is detachably fitted and fixed to the inner protrusion 51 so as to wrap around it, and a cylindrical anti-stick member 54 is similarly fitted and fixed to the outer protrusion 52. has been done. The outer periphery of the introduction pipe 53 and the adhesion prevention member 54
For example, a coil-shaped discharge electrode 55 is wound between the inner circumference and the inner periphery of the electrode. A common ring plate 56 forming a part of the adhesion prevention member is provided on the inner end surfaces of the introduction pipe 53 and the adhesion prevention member 54.
are fixed with screws 57, so that the introduction pipe 53 and the anti-adhesion member 54 are attached to the plate 4 while containing the discharge electrode 55.
Attached to 9.

However, this attachment can be done in various ways or in various orders, and after the ring plate 56 is fixed in advance as described above, the projection 51.5 is attached.
2 may be fitted at the same time.

For installation, a high-frequency introduction terminal connected to one end of an electrode 55 is fitted and fixed on the front side of the plate 49, and a gas introduction pipe 60 from the outside is screwed and fixed on the center part through a threaded part 59. be done.

By the vapor deposition method as described above, as shown in FIG.
A transparent conductive film (17['0 film) 14 is placed on top of the film, for example, 600
It is formed to a thickness of ~1oooX. This ITO film 1
4 is, for example, a sheet resistance of 200 to 500 Ω/C, 2,
The refractive index (ne) is 2'. In addition, the substrate 1 has a refractive index (n, ) −1,49~ which is optically transparent.
1.60, thickness 100 μm (D polyethylene terephthalate substrate, this other surface has a refractive index (ns
) -1,50 to 1.55, thickness λ/4 (λ is the wavelength of the incident light) 71 silicon oxide evaporated M layer 10, and a refractive index (
nz) = 1.75 to 1.83, the second silicon oxide vapor deposited layer 11 with a thickness of λ/4, and a refractive index (n,) = 1.
60 to 168, and a third silicon oxide deposited layer 12 with a thickness of λ/4.
10 l1jt while changing the above deposition conditions.

In forming the ITO film 14 by the above-mentioned vapor deposition method, the present inventor has repeatedly conducted various experiments and studies, and has found that setting the vapor deposition conditions to the conditions of the following formula (11) is effective in achieving the purpose of the present invention. He found that it is essential and extremely important.

(However, PX RlW is the same as above.) The first thing to point out is that the above vapor deposition method is carried out in ionized or activated oxygen gas, and therefore the vapor deposition surface is exposed to oxygen ions, etc. Cleaned (oxidation removal of organic matter on the surface of the substrate → generation of active groups such as carboxyl groups on the same surface)
, 2) The adhesion of the TO film is greatly improved, and the abrasion resistance is also improved.

Unlike the ion blating method, this method does not cause acceleration of oxygen ions or metal ions such as In or Sn (that is, bombardment damage to the film), so it is even better, and both film adhesion and film quality are improved.

Table 1 below shows the discharge power of the high frequency discharger at 500W%.
When the temperature of a 13.56 MHz, 100 μm thick polyethylene terephthalate substrate is 20 to 70°C, the characteristics of each ITO film formed at various P (oxygen gas pressure) and R (evaporation rate) are summarized. Indicated.

In this table, the abrasion resistance, chemical resistance, and evaluation were as follows.

Scratch resistance: 100f/ctn on the ITO membrane surface with gauze
Rub with the pressure of 2 and measure the change in sheet resistance R/Ro (R is the sheet resistance after the test and before the Rold test) before and after the rubbing, ◎ means the change is very small, ○ means the change is small, × means the change is small. Indicates that the change is very large.

Chemical resistance: The ITO film surface was treated with an acid CI NU (J) or an alkali (INKOH) or an organic solvent, and the surface condition was observed. ○ indicates a good surface condition, and × indicates a poor surface condition.

Evaluation: Indicates the overall evaluation of the ITO film, where 0 is extremely good, ◯ is good, △ is slightly poor, and × is poor.

FIG. 4 is a plot of the data shown in Table 1. According to this, the straight line P-2×10-'
The area between R and P=6X10'XR, i.e. 6X10
It can be seen that the ITO film has good characteristics in the oxygen gas pressure range represented by 'XR≦P≦2X10'XR. Since this gas pressure range corresponds to the above-mentioned 2fi+ (discharge power W = 500 Watt), it is extremely important to perform the vapor deposition under the conditions of equation (1). If the gas pressure P is lower than 6 x 10-'
Furthermore, if the gas pressure P exceeds 2×10'XR (or 1×-510 lo x w ), the degree of oxidation becomes too large and the sheet resistance increases again, which is inappropriate.

Moreover, from FIG. 4, the above gas pressure range is further 1X1. O
'XR≦P≦1.5 X to 'XR (or 5X10
"R, R ×w≦P≦0.75 X 10 X-W),
It can be seen that very good results can be obtained.

Next, the results of the high frequency discharge power W and oxygen gas pressure P are shown in FIG. Here, the deposition rate R=10
0 A/see. From this result, 1×]shoulder≦
Good results were obtained in the range of P≦3X10'XL, which corresponds to the gas pressure range of the present invention.

Furthermore, the above PXW and R are closely related to the oxidation degree (therefore, sheet resistance, light transmittance, etc.) of the transparent conductive film, and the results shown in Table 2 below were obtained regarding this.

Table 2 The degree of oxidation was estimated from the content ratio of In and O by ESCA analysis, and when expressed as 0/In, it was 1.3≦0/I
Good results will be obtained if n≦1.5.

This oxidation degree range can be realized under the conditions of the above formula (11) according to the present invention.

Based on the present invention, for the ITO film, its Sn content is In
It is preferable to reduce the content to 5% by weight or less (particularly 4% by weight or less).

In other words, in conventional technology, films are generally formed at high temperatures, but if the substrate temperature is lowered (particularly below 2008C) during film formation by vapor deposition, unlike high-temperature film formation, Sn It was found that the content sensitively affects the sheet resistance and light transmittance of the ITO film. In other words, when the Sn content increases (1+, the number of free electrons in ITO shows an increasing tendency, but the mobility of free electrons decreases more than that, and the sheet resistance increases. thing.

In particular, in low-temperature film formation, the crystallinity of ITO is incomplete, so the mobility of free electrons is lower than in high-temperature film formation.

(2) Since Sn is more difficult to oxidize than In, especially in low-temperature film formation, the degree of oxidation of Sn becomes insufficient and the light transmittance of ITO becomes low.

This defect occurs. However, if the Sn content is 5% by weight or less, the I
When a film of TO is formed, the decrease in the mobility of free electrons can be significantly suppressed, and the sheet resistance of the film can be extremely reduced. Moreover, since Sn is present in a small amount, its oxidation is sufficiently carried out, which increases the light transmittance (transparency) of the film.
In addition, the patterning (etching) of ITO becomes easier.

Note that the above-described low-temperature film formation is suitable when a substrate with low heat resistance, such as a polymer substrate, is used as the substrate on which the ITO film is provided.

In Figure 6, the horizontal axis shows Sn determined by ESCA analysis.
By changing the content (Sn/In), we showed changes in properties depending on this content. According to this, if Sn/In is set to 5% by weight, especially 4% by weight or less (furthermore, 0.05 to 3.5% by weight, especially 0.05 to 1% by weight), 'immediately after film formation (Fig. t-(a) in the figure), and after heat treatment (A-(b) in the figure
)) sheet resistance can be kept very low.

That is, from the viewpoints of both the fact that sheet resistance increases when Sn/In exceeds 5% by weight and the change in sheet resistance caused by heat treatment being kept small to improve the heat resistance or long-term stability of the film, Sn /In is preferably 5% by weight or less. In this content range, the sheet resistance is IKΩ/
Furthermore, the heat resistance (resistance change due to heat treatment) can be made 15 times or less, resulting in a film that is practically excellent. However, S
If n/In is too small, the change in sheet resistance will be rather large, so it is desirable to set the lower limit to 0.05% by weight (7).

Furthermore, as shown in Figure 6, the light transmittance of the ITO film decreases when the Sn/In content exceeds 5% by weight.
It can be seen that the light transmittance is low at mμ, but becomes worse at 5% by weight or more, reaching 80 or less. This is because Sni increases too much and its oxidation degree decreases. Also from the viewpoint of light transmittance, Sn/In should be less than 4% by weight.

The above results indicate that the ITo film 14 was formed at a low temperature (substrate temperature 20
0° C.), and is found to be effective in such low-temperature film formation.

This low-temperature film formation is useful when a polymeric material is used as the substrate 1.

Materials that can be used as substrate materials include polyester resin,
Polycarbonate resin, polyamide resin, acrylic resin, ABS resin, polyamideimide resin, styrene resin,
Thermoplastic resins such as polyacetal resins and polyolefin resins; or epoxy resins, diallyl phthalate resins,
These include thermosetting resins such as silicone resins, unsaturated polyester resins, phenol resins, urea resins, and melamine resins.

Among these, polyester resins, particularly polyethylene terephthalate film or polyethylene-2°6-naphthalene dicarboxylate film, are preferred because they are excellent in heat resistance, mechanical properties, and translucency. However, their refractive index is generally 1.5 to 1.6, and among them, polyethylene terephthalate has a refractive index of 151. Therefore, if the substrate has such a refractive index, the above amplitude condition cannot be satisfied.

However, as shown in FIG.
In the anti-reflection layer consisting of 0, the refractive index is changed stepwise or continuously in the thickness direction, so the conditions under which the low reflectance at the center wavelength required for the anti-reflection layer can be obtained. can be satisfied, and it is possible to fully exhibit the antireflection effect. Moreover, since the anti-reflection layer can be formed from materials with the same components by simply changing the conditions during deposition, it can be manufactured easily and at low cost, and the film quality can be improved by preventing the contamination of foreign substances during the manufacturing process. can. In addition, since they are composed of the same components, the structure and film strength between each film are sufficient even when used as a multilayer film.

Note that the present invention applies not only to the case of low-temperature film formation described above, but also to
Effective even in high-temperature film formation. For example, when a glass substrate was used as the substrate and an ITO film containing 65% by weight of Sn/In was formed thereon at about 550'C under the same conditions as described above, the following good results were obtained.

Sheet resistance (KCl port) Immediately after film formation 0.3 to 070 After being left in the air at 80°C for 0.35 to 1000 hours, the above-mentioned transparent conductive film 8 can be attached to, for example, a display screen of a see-through type finger touch input device. It is very effective when used.

This type of input device can be used without using a keyboard.
Data can be input simply by touching a predetermined position on the display screen with a fingertip. For this reason, until now the input/output terminal devices for converters have been a display section (display surface) and an input section (keyboard).
This greatly simplifies the operation compared to when the two were separate. In such an input device, the seventh
As shown in the enlarged figure, the screen (or front spring glue 7)
The above-mentioned transparent conductive film 8 is attached to the front surface of the front panel 7o with the antireflection layer 13 on the outside, and another transparent conductive film 18 is attached directly to the front surface of the front panel 7o, so that both films are attached. 8 and 18 are integrated via a peripheral gasket (or spacer) 15, and a constant gap 16 is formed between both films. In this case, the film 18 may be a film in which a transparent conductive film (ITO film) 14 and an antireflection layer 17 are laminated on the polymer sheet substrate 1 as is known in the art. In both of the opposing films 8 and 18, the conductive films 14-14 are arranged in stripes so as to be orthogonal to each other, thereby forming a matrix switch group. Since this matrix itself is well known, its details will not be explained.

Therefore, as shown in FIG. 7, when a desired position on the surface of the film 80 is pressed with the fingertip 9, the film 8 is elastically deformed until it comes into contact with the other film 18, as shown by the dashed line, and at this point the matrix crosses. Both conductive films 14-1 at the position
4 are electrically connected (capacitively coupled), a corresponding output is obtained, and the above-described operation can be started. In addition, in the above-mentioned film 18, the antireflection film 17 is not necessarily necessary, and a direct contact method of both conductive films 14-14 can also be adopted. Alternatively, the film 18 may not be a conductive film, but may be a mere resistive sheet, and the capacitance change between the two films or the voltage value at the contact point may be taken out as an output.

In any case, since the input method is based on the touch of the fingertip 9, the influence of dirt on the base surface is likely to occur, but in the case of the row shown in FIG.
effectively prevented by the presence of In particular, when used in a bright room, light reflection on the surface of the film 8 is significantly reduced by the anti-reflection layer 13, so the displayed image on the screen can be seen clearly and the above-mentioned dirt is hardly noticeable. It disappears.

Note that the combination of both films as shown in FIG. 7 can also be applied to a liquid crystal display device. That is, as shown in FIG. 8, the conductive films on one side (for example, on the film 18 side) of each of the conductive films 14-14 of both films 8 and 18 are arranged in the shape of a Japanese character,
A liquid crystal 19 is sealed in the gap 16 between both films, and a voltage is applied to the sun-shaped electrodes in time series according to a known operation, thereby making it possible to display a predetermined number. However, in the case of twisted nematic display,
An alignment film and a polarizing film are required. In this case as well, since reflection on the film 8 on the front side (that is, the viewing side) is sufficiently prevented by the antireflection layer 13, a clear numerical pattern can be displayed.

The implementation ttU described above can be further modified based on the technical idea of the present invention.

In other words, the conditions and method Fi for forming the transparent conductive film and antireflection layer described above may be varied. The transparent conductive film may be formed of only indium oxide or other materials. The transparent conductive film may be formed on the antireflection layer side, and may be provided at the middle position, the top position, or the bottom position of the antireflection layer. Depending on the application, an antireflection layer may not be necessary.

6. Effects of the invention Since the vapor deposition is carried out under the conditions of 1×10−“×”L, the electrical resistance of the transparent conductive film is extremely low, and the degree of oxidation is sufficient even at low concentrations to ensure light transmission. rate can also be maintained high. Further, the adhesion of the transparent conductive film is good because there is no bombardment damage and the substrate interface is cleaned, and the abrasion resistance and the like are improved.

[Brief explanation of the drawing]

The drawings show examples of the present invention, in which Fig. 1 is a schematic sectional view of a vapor deposition apparatus, Fig. 2 is a sectional view of a high frequency discharge tube, Fig. 3 is a sectional view of a transparent conductive film, and Fig. 4 is a sectional view of a transparent conductive film. The figure is a graph showing characteristics depending on evaporation rate and oxygen gas pressure. Figure 5 is a graph showing changes in characteristics depending on high frequency discharge power and oxygen gas pressure. Figure 6 is a graph showing changes in characteristics depending on tin content (Sn/In). Graphs showing characteristic changes, FIG. 7 is a sectional view of a finger touch input device, and FIG. 8 is a sectional view of a liquid crystal display device. In addition, in the symbols shown in the drawings, 1...
・・・Base body or substrate 13・・・・・・・・・・・・・・・
・・・・・・・・・・・・ Antireflection layer 14 ・・・・・
・・・・・・－・・・・・・・・・・・・Transparent conductive film (I
TO film) 42 a, 42 b...
・Evaporation source 43・・・・・・・・・・・・・・・・・・・・・
...It is a high frequency discharge tube. Agent Patent attorney Hiroshi Aisaka (and 1 other person) No. 10 No. 30 No. 40 0 510 15 20 Drug development level R (A/ac) 50 0.5'θθ lθθθ ] 6th field A B ″U, front shoulder amount (heavy layer 70th 5th 80th

Claims (1)

[Claims] 1. When forming a transparent conductive film by a vapor deposition method in the presence of an oxidizing gas ionized or activated by a high-frequency discharge device, [where P is the pressure of the oxidizing gas (Torr)] ), R is the deposition rate W (A/5ee), and W is the high frequency discharge power (Watt) of the high frequency discharge device. ] A method for forming a transparent conductive film, characterized by performing vapor deposition under the following conditions.