JP4693401B2 - Method for forming ITO transparent conductive film and color filter substrate with ITO transparent conductive film - Google Patents

Description

  The present invention relates to a color filter substrate on which an ITO transparent conductive film used for a flat panel display is formed.

  The transparent conductive film is an important member indispensable in flat panel displays, touch panels, and solar cells due to the characteristics of passing light and flowing electricity. In particular, indium oxide (ITO) containing several wt% of tin oxide is It is the most famous transparent conductive film.

  Many of the ITO transparent conductive films used for flat panel displays are formed by a vacuum film forming method.

As a method for forming the ITO transparent conductive film by a vacuum film forming method, there are a method such as an ion plating method, a sputtering method, and a vapor deposition method, and the sputtering method is the most common method. Regarding the ITO transparent conductive film formed by sputtering, the ITO transparent conductive film having a resistance value of 2 × 10 ⁻⁴ Ω · cm or less can be obtained by forming the film by heating the substrate to 300 ° C. or higher. It is described in Patent Document 1.

  In addition, when an ITO transparent conductive film is formed by an ion plating method using a plasma gun, since the energy of the film formation particles is high, the resistance value is low at a relatively low temperature of about 200 ° C. It is disclosed that an ITO transparent conductive film having a low thickness can be obtained (Patent Document 2).

  When emitting three primary colors of RGB light on a display, irradiate phosphors emitting these lights with electron beams or ultraviolet rays, or absorb light other than the target wavelength using white light as the primary light. Or use a color filter that produces light of the desired wavelength. An organic polymer material is used for a part of the color filter (Non-Patent Document 1). This is applied to a transparent substrate such as glass at a predetermined interval, but when an ITO film as a transparent conductive film is formed thereon, if the substrate with a color filter is heated too much, the color that is an organic polymer When a substrate made of an inorganic material such as a glass substrate is released from the surface or inside of the filter, gas remaining during production, organic polymer decomposition product gas, or moisture adsorbed on the surface is released into the film formation atmosphere. Compared to the above, it is difficult to stably obtain an ITO transparent conductive film having good characteristics. In addition, an overcoat layer made of an organic polymer for smoothing the surface is often laminated on the color filter, and a similar outgassing from the overcoat layer also increases the resistance of the ITO transparent conductive film. It is a factor. For this reason, when the ITO transparent conductive film is formed by heating the substrate with the color filter, it has been difficult to obtain a low resistance ITO transparent conductive film.

Patent Document 3 describes that an ion plating method using a plasma gun can obtain a low resistance film when an ITO film is formed on a color filter, but when the substrate temperature is heated to 180 ° C. or higher, As pointed out earlier, the gas remaining at the time of film production, the decomposition gas of organic polymer due to overheating, and moisture adsorbed on the surface are released into the film formation atmosphere from the surface and inside of the color filter, There was a problem that an extremely low resistance ITO film having a resistivity lower than 2.0 × 10 ⁻⁴ Pa could not be formed.
JP-A-9-171188 JP 2000-17430 A Patent 2657206 Manabu Sasaki “Liquid Crystal Color Filter”, Electronic Materials August 2004 issue, p60

An object of the present invention is to obtain a smooth color filter substrate with an ITO transparent conductive film having a low resistance in an ITO transparent conductive film formed on a color filter.

The ITO transparent conductive film forming method of the present invention is a method of forming an ITO transparent conductive film on a substrate on which a color filter is provided, and an ion plating method using a plasma gun for forming the ITO transparent conductive film. When the ITO transparent conductive film is formed, the temperature of the substrate provided with the color filter is 90 ° C. to 160 ° C., and the input power per unit area of the plasma beam irradiated to the ITO raw material is 0 A method for forming an ITO transparent conductive film , wherein the film thickness is from 0.5 to 1.6 kW / cm ² .

  The color filter substrate with an ITO transparent conductive film of the present invention has an arithmetic average roughness Ra (ITO) indicating the surface smoothness of the color filter substrate with the ITO transparent conductive film, and the arithmetic average roughness of the substrate provided with the color filter. The color filter substrate with an ITO transparent conductive film according to the above-described ITO transparent conductive film forming method, wherein Ra (ITO) -Ra (CF) ≦ 1 nm with respect to the thickness Ra (CF).

In the color filter substrate with an ITO transparent conductive film of the present invention, the specific resistance of the ITO transparent conductive film is in the range of 1.2 × 10 ^{−4 to} 2.0 × 10 ⁻⁴ Ω · cm. This is a color filter substrate with an ITO transparent conductive film formed by the above-described ITO transparent conductive film forming method.

  In the color filter substrate with an ITO transparent conductive film of the present invention, the ITO transparent conductive film has low resistance and excellent smoothness, and can contribute to high performance of flat panel displays such as liquid crystal display elements and organic EL display elements.

  As shown in FIG. 1, a color filter substrate 3 with an ITO transparent conductive film of the present invention is formed by forming an ITO transparent conductive film 1 on the surface of a substrate 2 provided with a color filter.

  The substrate 2 provided with the color filter has a configuration as shown in FIG. Normally, color filters used for display devices such as liquid crystal and organic EL devices have a black matrix 2b arranged on a glass substrate 2a such as soda lime glass to improve display contrast and prevent TFT malfunction. Further, red (R), Green (G), and Blue (B) RGB color organic polymers are separately applied to form a color pixel 2c, and an overcoat layer made of a transparent organic polymer is further formed thereon. 2d is applied.

  As the glass substrate 2a, relatively inexpensive soda lime glass is mainly used, but when used for a TFT element or the like, alkali-free glass or the like is also used.

Metal chrome has been mainly used for the black matrix 2b until now, but recently, cases of using resin materials are increasing in relation to diversification of display modes and environmental problems.
For the color pixel 2c, a polyvinyl alcohol type or an acrylic type in which pigments or dyes are dispersed is used. Further, the overcoat layer 2d formed thereon is for smoothing the level difference caused by the color polymer pixel, and an acrylic or epoxy organic polymer is formed with a thickness of 2 to 3 μm. .

  Further, if necessary, a thin silica film or silicon oxynitride film having a thickness of about 30 nm may be formed as a protective film 2e to improve chemical durability and adhesion with ITO. is there.

  The ITO transparent conductive film 1 formed on the substrate 2 provided with a color filter is obtained by adding 5 to 10 wt% of tin in terms of oxide to indium oxide. When the amount of tin added is less than 5 wt% in terms of oxide, the carrier concentration in the ITO transparent conductive film is low, and when it exceeds 10 wt%, the carrier mobility is low. Therefore, the amount of tin added is preferably 5 to 10 wt% in terms of oxide.

  The ITO transparent conductive film is formed using an ion plating method using a plasma gun, more preferably using an arc plasma deposition method using a pressure gradient type holocathode plasma gun.

  The arc plasma deposition method includes a pressure gradient type plasma gun that generates a plasma beam toward the inside of the vacuum chamber, a magnet that contracts the cross section of the plasma beam, and an annular focusing coil, and is arranged in the vacuum chamber by the plasma beam. For example, a film forming apparatus schematically shown in FIG. 3 is used.

  3 is a vacuum chamber 4, a pressure gradient type plasma gun 5 attached to the side wall of the vacuum chamber 4, a crucible 6 disposed at the bottom of the vacuum chamber 4, and an upper portion of the vacuum chamber 4. The substrate support holder 7 and the like.

The crucible 6 is desirably made of carbon. The pressure gradient type plasma gun 5 is preferably a pressure gradient type holocathode plasma gun. The pressure gradient plasma gun 5 is a composite cathode composed of a Ta pipe 8 and a LaB ₆ disk 9. When the discharge argon gas 10 is introduced into the Ta pipe 8, the pressure gradient plasma gun 5 is heated. Thermal electrons are emitted from the Ta pipe 8 and the LaB ₆ disk 9 to form a plasma beam 11.

The inside of the pressure gradient type plasma gun 5 is always kept at a higher pressure than the vacuum chamber 4 and has a structure in which Ta and LaB ₆ exposed to a high temperature prevent deterioration such as oxidation by oxygen gas or evaporation gas. .

In addition, a substrate heating heater 12 and a thermometer 13 are disposed above the substrate support holder 7. The substrate heating heater 12 is provided to keep the substrate 2 provided with the color filter for film formation at a predetermined temperature, and controls the output of the substrate heating heater 12 based on the measured value of the thermometer 13. ing. The substrate 2 provided with the color filter controls the output of the substrate heater 12 so that the temperature during film formation is 90 ° C. to 160 ° C. The substrate heater 12 is preferably a lamp heater.
An oxygen gas supply nozzle 14 is disposed on the side wall of the vacuum chamber 4, and oxygen gas 15 is supplied to the oxygen gas supply nozzle 14 via a mass flow controller (not shown). A vacuum exhaust device 16 is connected to the vacuum chamber 4. The vacuum exhaust device 16 is operated based on the value of the vacuum gauge 17, and the inside of the vacuum chamber 4 is maintained at a predetermined pressure (degree of vacuum). The

  The ITO transparent conductive film 1 according to the present invention is formed by the following procedure using the film forming apparatus shown in FIG.

  A carbon crucible 6 is filled with granular ITO raw material 18, and the crucible 6 is set at the bottom of the vacuum chamber 4. The ITO raw material 18 is preferably granular in order to be put in a crucible, but the shape is not particularly limited.

After the substrate 2 provided with the color filter for forming the ITO transparent conductive film 1 is attached to the substrate support holder 7, the pressure inside the vacuum chamber 4 may be exhausted until the pressure is about 5 × 10 ⁻⁴ Pa or less. desirable. At the same time, it is preferable to heat the substrate 2 provided with the color filter to a predetermined temperature to remove the gas adsorbed on the surface and the gas released from the inside.

  After the evacuation, the discharge argon gas 10 whose flow rate is controlled to 10 to 40 sccm using a mass flow controller (not shown) is supplied to the vacuum chamber 4 through the pressure gradient type plasma gun 5.

  Next, a predetermined amount of oxygen gas 15 is supplied from the gas supply nozzle 14 to the vacuum chamber 4, and the pressure inside the vacuum chamber 4 is adjusted to a pressure of 0.08 to 0.2 Pa by the vacuum exhaust device 16.

Next, the pressure gradient type plasma gun 5 is operated, the plasma beam 11 is focused on the ITO raw material 18 in the crucible 6, and the ITO raw material 18 is heated to a temperature at which the ITO sublimates. In order to focus the plasma beam 11 on the ITO raw material 18 in the crucible 6, a focusing coil 19 and a magnet 20 are used. Here, as charged power per unit area of the plasma beam to be irradiated on the ITO material 18 is 1.6 kW / cm ² or less, to adjust the current flowing in the convergence coil. At this time, the shutter plate 22 is closed so that the evaporated ITO material 18 does not adhere to the substrate. At this time, by the temperature of the substrate 2 on which the color filter is provided in the 160 ° C. or less, for small Ku the resistance of the ITO transparent conductive film.

  After the evaporation of the ITO raw material 18 heated by the plasma beam 11 is stabilized, the shutter 22 is opened for a predetermined time, and ITO is deposited on the substrate 2 provided with the color filter. The time for which the shutter 22 is opened and the ITO film is formed is about 2 minutes at the maximum, and usually about 1 minute.

The ITO material 18 heated and evaporated by the plasma beam 11 and the introduced oxygen gas 15 are ionized by the plasma atmosphere 21. The ITO raw material 18 becomes ionized particles. The ionized particles are accelerated toward the substrate 2 provided with the color filter by a potential difference between the plasma potential of the plasma atmosphere 21 and the floating potential of the substrate 2 provided with the color filter, and have a large energy of about 20 eV. The ITO transparent conductive film 1 having a low resistance (specific resistance 1.2 × 10 ^{−4 to} 2.0 × 10 ⁻⁴ Ω · cm) reaches and deposits on the lower surface of the substrate 2 provided with the color filter. A film is formed.

In the ion plating method using a plasma gun, since the ITO material 18 is heated to a high temperature by the plasma beam 11 in order to evaporate the ITO material 18, the temperature of the substrate rises due to the radiant heat from the ITO material 18 that has become high temperature. . In particular, in the substrate 2 provided with a color filter, heat radiation is easily absorbed by the black black matrix 2b, and the temperature of the substrate 2 is likely to rise. When the maximum temperature of the substrate 2 provided with the color filter for forming the ITO transparent conductive film 1 is lower than 90 ° C., the ITO transparent conductive film is not crystallized and the resistance value of the ITO transparent conductive film is 2.0. In order to use it as a good device exceeding × 10 ⁻⁴ Ω · cm, it is necessary to increase the film thickness, which causes problems such as attenuation of transmittance. If the maximum temperature reached during film formation of the substrate 2 provided with the color filter is 90 ° C. or higher, the resistance value of the ITO transparent conductive film is lowered and the conductivity is improved. Therefore, the formation of the substrate 2 provided with the color filter is improved. The filming temperature is preferably 90 ° C. or higher.

  In addition, if the substrate 2 provided with the color filter is deposited at a temperature exceeding the maximum temperature of 160 ° C., the residual gas from the surface of the color pixel or overcoat layer, which is an organic polymer, and the overcoat layer, decomposition and generation Gas is easily generated, and the hardness of the polymer is also softened. As a result, the film is cracked and does not function as a transparent conductive film, making it difficult to use as a device.

The input power per unit area of plasma irradiated to the ITO raw material 18 when evaporating the ITO raw material 18 is 1.6 kW / cm ² or less because the input power per unit area of plasma is 1.6 kW / cm ^2. If it exceeds 1, the temperature of the ITO raw material 18 becomes extremely high and exceeds 160 ° C., which is not preferable. In addition, if the input power is smaller than 0.5 kW / cm ² , the ITO raw material is not sufficiently evaporated, and the rate of forming the ITO transparent conductive film is decreased. Therefore, the input power should be 0.5 kW / cm ² or more. Is desirable.
In particular, when the temperature rise of the substrate 2 provided with the color filter during film formation exceeds 50 ° C., the color filter made of organic polymer or the overcoat layer is deteriorated or gas is released from the inside of these organic substances. Or a film with non-uniform characteristics in the thickness direction of ITO.

When the input power of the plasma beam irradiated to the ITO raw material 18 exceeds 3 kW / cm ² or the input current of the plasma beam exceeds 40 A / cm ² , the radiant heat increases remarkably and a color filter is formed during film formation. The temperature rise of the substrate 2 exceeds 50 ° C., and the color filter substrate and the overcoat layer made of organic polymer are deteriorated, or the gas emission from the inside of these organic substances occurs. It cannot be. Therefore, in order to make the temperature rise 50 ° C. or less, it is desirable that the input power of the plasma beam irradiated to the ITO raw material 18 is 3 kW / cm ² or less.

  The arithmetic average roughness Ra (ITO) indicating the surface smoothness of the ITO transparent conductive film formed in this way is expressed by Ra (CF) with respect to the arithmetic average roughness Ra (CF) of the substrate provided with the color filter. ITO) —Ra (CF) ≦ 1 nm is obtained. The arithmetic average roughness of the surface is a value defined in JIS B0601, and is calculated from a roughness curve obtained by measuring surface irregularities.

  In general, an ITO transparent conductive film obtained by a sputtering method has a rough surface with a roughness of about 5 nm when Ra is formed at a substrate temperature of about 300 ° C. in order to increase conductivity. In order to obtain the film, it is necessary to lower the substrate temperature to about 100 ° C., but when the substrate temperature is 100 ° C., the conductivity of the film is remarkably lowered.

  The color filter substrate with an ITO transparent conductive film of the present invention is a substrate provided with a color filter that is not as heat resistant as glass, on which an ITO transparent conductive film having excellent conductivity and smoothness is formed, It can be suitably used for display devices such as liquid crystal elements and organic EL elements.

  3 is a batch-type film forming apparatus in which ITO is formed on a substrate provided with a color filter one by one, but the substrate provided with the color filter is continuously placed in the film forming chamber. It can also be produced by an in-line type film forming apparatus that has been transported to enable continuous production of ITO films.

Examples of the present invention will be described below. The ITO transparent conductive film was formed into a film using the film-forming apparatus shown in FIG. In addition, this invention is not limited to a following example.
In both examples and comparative examples, the surface roughness characteristics were measured by an atomic force microscope, and the arithmetic average roughness was calculated.
Example 1
As the ITO raw material 18, ITO powder granules (Sn content is 5 wt% in terms of oxide) manufactured by Kojundo Chemical Laboratory Co., Ltd. were used. This was filled into a carbon crucible 6 and placed at the bottom of the vacuum chamber 4.

A substrate 2 on which a color filter using soda lime glass having a size of 370 mm × 470 mm and a thickness of 0.4 mm as a substrate was placed on the substrate support holder 7 with the surface on which the color filter was applied facing down. Thereafter, the vacuum evacuation device 16 was evacuated for about 10 minutes until the pressure in the vacuum chamber reached 4.0 × 10 ⁻⁴ Pa.
After heating the substrate 2 provided with the color filter to 110 ° C., 25 sccm of argon gas for discharge was supplied to the pressure gradient type plasma gun 5, and 25 sccm of oxygen gas was supplied from the oxygen gas supply nozzle 14. Next, electric power is gradually applied until the output of the pressure gradient type plasma gun 5 reaches 2.5 kW, a plasma beam 11 is generated from the pressure gradient type plasma gun 5 and irradiated to the ITO material 18, and the ITO material 18 is heated. And evaporated.

As the pressure gradient type plasma gun 5, a pressure gradient type holo cathode plasma gun was used. At this time, the current flowing through the focusing coil 19 is adjusted while controlling the exhaust of the vacuum exhaust device 16 so that the pressure inside the vacuum chamber 4 becomes 0.15 Pa, and the plasma source 11 irradiated to the ITO raw material 18 is adjusted. The irradiation area was set to 3 cm ² . At this time, the input power per unit area of the plasma beam 11 input to the ITO raw material 18 was 0.8 kW / cm ² .

  After the irradiation of the plasma beam 11, the pressure inside the vacuum chamber 4, and the evaporation of the ITO raw material 18 were stabilized, the shutter 22 was opened for 63 seconds, and the ITO transparent conductive film 1 was formed on the substrate 2 provided with the color filter.

  The temperature of the substrate on which the film is formed is increased by receiving radiant heat from the ITO raw material 18 heated during the film formation. The temperature of the color filter substrate 2 with the ITO transparent conductive film immediately after the film formation is 145 ° C. It was 35 ° C higher than before the membrane.

  The appearance of the obtained color filter substrate 3 with the ITO transparent conductive film was good, and visual inspection did not show any appearance defects such as cracks.

The thickness of the ITO transparent conductive film 1 is 157 nm, the sheet resistance value of the ITO transparent conductive film 1 is 9.2Ω / □, and the specific resistance is 1.4 × 10 ⁻⁴ Ω · cm, which is a low resistance film. there were.

  The arithmetic average roughness Ra (ITO) of the surface of the ITO transparent conductive film 1 is 1.3 nm, which is an increase of 0.8 nm with respect to Ra (CF) (= 0.5 nm) of the color filter before film formation. there were.

Comparative Example 1
A color filter substrate 3 with an ITO transparent conductive film was prepared in the same manner as in Example 1 except that the substrate 2 on which the color filter was applied was not heated.

  The appearance of the color filter substrate 3 with the ITO transparent conductive film was good, and there was no appearance defect such as a crack in the visual inspection. The temperature of the substrate immediately before the film formation was 27 ° C., and the temperature of the color filter substrate immediately after the film formation was 70 ° C., which was 43 ° C. higher than before the film formation.

The arithmetic average roughness Ra (ITO) of the surface of the ITO transparent conductive film 1 is 0.6 nm, which is slightly 0.1 nm compared to Ra (CF) (= 0.5 nm) of the color filter before film formation. The increase was a very smooth film. However, on the other hand, the thickness of the ITO transparent conductive film 1 is 155 nm, the sheet resistance value of the ITO transparent conductive film 1 is 39Ω / □, and the specific resistance is 6 × 10 ⁻⁴ Ω · cm so that the resistance is high. It was a poor film.

Comparative Example 2
The production of the color filter substrate 3 with the ITO transparent conductive film was tried in the same manner as in Example 1 except that the substrate 2 on which the color filter was applied was heated to 190 ° C. However, since the gas was released from the organic polymer constituting the substrate 2 to which the color filter was applied at the heating temperature of the substrate 2 to which the color filter was applied, the vacuum exhaust device 16 was operated for 20 minutes. The plasma gun pressure gradient type plasma gun 5 was operated in a state where the internal pressure did not reach 5.0 × 10 ⁻⁴ Pa and the pressure was 1.5 × 10 ⁻³ Pa.

  The produced color filter substrate 3 with an ITO transparent conductive film could not be used because fine cracks were observed by microscopic observation.

  In this comparative example, the temperature of the color filter substrate immediately after film formation was 215 ° C., which was 25 ° C. higher than before the film formation.

Comparative Example 3
Example 1 is the same as Example 1 except that the current flowing through the converging coil 19 of the plasma beam 11 is adjusted so that the irradiation area of the plasma beam 11 irradiated to the ITO raw material 18 is 1.5 cm ^2. Similarly, an ITO transparent conductive film was formed.

The input power per unit area of the plasma beam 11 input to the ITO raw material 18 was 1.7 kW / cm ² .

  The external appearance of the produced color filter substrate 3 with an ITO transparent conductive film was slightly cracked by microscopic observation and could not be used.

  In this comparative example, the temperature of the color filter substrate immediately after film formation was 165 ° C., which was 55 ° C. higher than before film formation.

Comparative Example 4
In the first embodiment, the output of the pressure gradient plasma gun 5 is set to 7.5 kW, and the plasma coil 11 irradiation area is adjusted to 3 cm ² by adjusting the converging coil current of the plasma beam. An ITO transparent conductive film was formed in the same manner as in Example 1 except for the above. At this time, the input power per unit area of the plasma beam input to the ITO raw material 18 was 2.5 kW / cm ² .

  The appearance of the obtained color filter substrate 3 with the ITO transparent conductive film had cracks in the microscopic observation, and was incomplete as the transparent conductive film. In this film formation, the temperature of the color filter substrate immediately after the film formation was 195 ° C., and the temperature was increased by 85 ° C. compared to before the film formation.

It is the schematic of the cross section which shows the structure of the ITO transparent conductive film formed into a film on the board | substrate with which the color filter was provided. It is the schematic of the cross section which shows the structure of the board | substrate with which the color filter was provided. It is an apparatus schematic diagram of an ion plating method using a plasma gun (an activated reaction vapor deposition method using a pressure gradient type plasma gun).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ITO transparent conductive film 2 Substrate 2a provided with color filter Glass substrate 2b Black matrix 2c Color pixel 2d Overcoat layer 2e Protective film 3 Color filter substrate with ITO transparent conductive film 4 Vacuum chamber 5 Pressure gradient type plasma gun 6 Crucible 7 Substrate support holder 8 Ta pipe 9 LaB ₆ disc 10 Discharge argon gas 11 Plasma beam 12 Substrate heating heater 13 Thermometer 14 Oxygen gas supply nozzle 15 Oxygen gas 16 Vacuum exhaust device 17 Vacuum gauge 18 ITO raw material 18
19 Convergence coil 20 Magnet 21 Plasma atmosphere 22 Shutter plate 23 Power supply for discharge

Claims (3)

In the method of forming an ITO transparent conductive film on a substrate provided with a color filter, an ITO transparent conductive film is formed by using an ion plating method using a plasma gun for forming the ITO transparent conductive film. When the temperature of the substrate provided with the color filter is 90 ° C. to 160 ° C., the input power per unit area of the plasma beam irradiated to the ITO raw material is 0.5 to 1.6 kW / cm ^2. A method for forming a transparent ITO conductive film , which is characterized. The arithmetic average roughness Ra (ITO) indicating the surface smoothness of the color filter substrate with the ITO transparent conductive film is Ra (ITO) -Ra with respect to the arithmetic average roughness Ra (CF) of the substrate provided with the color filter. The color filter substrate with an ITO transparent conductive film obtained by the method for forming an ITO transparent conductive film according to claim 1, wherein (CF) ≦ 1 nm. The specific resistance of the ITO transparent conductive film is in the range of 1.2 × 10 ^{−4 to} 2.0 × 10 ⁻⁴ Ω · cm, according to the method for forming the ITO transparent conductive film according to claim 1. Color filter substrate with ITO transparent conductive film.

Images