JPH02293701A - Formation of titanium oxide thin film and material to be deposited by evaporation used therein - Google Patents

Abstract

PURPOSE:To make efficient and inexpensive formation by using a material which is to be evaporated and contains 15 to 30wt.% TiO in a mixture composed of TiO and TiO2 at the time of forming a thin film deposited by evaporation on the surface of a substrate by a vacuum vapor deposition. CONSTITUTION:Metals, glass, resins, etc., are used as the substrate and are preferably transparent, for which, for example, a polymethyl methacrylate resin, etc., are used. The mixture which is composed of the TiO and TiO2 and in which the content of the TiO therein is 15 to 30wt.%, more preferably 20 to 25wt.% is used as the material to be deposited by evaporation. The generation amt. of O2 is large and the workability is poor as the pretreatment of the material to be deposited by evaporation takes too much time if the content of the TiO is below 15wt.%. On the other hand, the use of the costly TiO increases and the cost of the material to be evaporated increases while the improvement in the effect is not admitted if the amt. exceeds 30wt.%. The titanium oxide thin film which is transparent and good in appearance and is adequate for optical applications is inexpensively formed with the good working efficiency by using the material to be evaporated within the prescribed range.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for forming a titanium oxide thin film and a vapor deposition material used therein, and more specifically to an antireflection film, a reflection enhancing film, a heat ray blocking film, a wavelength selective film, etc. The present invention relates to a method for forming a titanium oxide thin film on a substrate surface used for optical films, etc., and a vapor deposition substance used therein.

? 2. Description of the Related Art Optical articles such as lenses and filters are coated with optical films such as antireflection films. The constituent materials of this optical film include MgF2, Si02, Zr(h, TiO2, In
zOs, SnOz, TiO, ZnS% CeOz
, HfOz, Y203, Aβ203, SiO, Mgθ, and other inorganic dielectrics. These substances are heated by resistance heating or electron beam heating in a vacuum evaporation method, evaporated and sublimated, and further processed by an ion plating method or I A D (Ion Assisted Dep).
When using the ionization method, the ions are ionized and formed as a thin film on the surface of the substrate.

Among these inorganic dielectrics, TiO■ has no sublimation property, that is, its evaporation temperature (180°C) is lower than its melting point (1640°C).
Since the temperature is high (0 to 2200°C), it remains in a molten state during evaporation.

For this reason, instead of directly inserting the Tie2 table soot into the copper electron beam hearth, which is cooled with water, it is necessary to use a material such as tungsten, tantalum, molybdenum, boron nitride, or alumina to provide air insulation between the hearth and the hearth. A hearth liner made in? It is used for vacuum evaporation, etc. Furthermore, when TiO■ is heated to its melting point, it decomposes and 0■ is generated (3TiO■→TiOz+TiO
+Ti+ 1.5 02), a scattering phenomenon of molten TiO■ in the hearth liner occurs. For this reason, sufficient degassing is performed before forming the thin film in order to prevent this scattering and to prevent the formation of dirt in the tank.

On the other hand, TiO also remains in a molten state during evaporation because its evaporation temperature (1800-2000°C) is higher than its melting point (1750°C), but contrary to TiOz, it has a genotar action that absorbs 02, and this causes the formation of thin films. For the purpose of preventing coloring, a titanium oxide thin film is formed on the substrate surface by resistance heating or electron beam heating while introducing a gas containing O atoms such as O2 or air into a vacuum chamber.

(Problem to be Solved by the Invention) However, in the conventional method using TiOz alone as the evaporative substance, when heating with an electron beam, 0.0 gas is generated, resulting in a scattering phenomenon of the molten substance in the hearth liner for the electron beam. Is it thin because it happens? There is a drawback that a pretreatment (paking) of sufficient degassing must be carried out before formation. In addition, in order to shorten this pretreatment time, increasing the power of the electron beam increases the pressure inside the vacuum chamber, so a pump with a high pumping speed is required, or conversely, a pump with a low pumping speed Since the pressure becomes too high, the power of the electron beam must be reduced, resulting in problems such as a long preprocessing time. In order to shorten this pretreatment time, even if the formation of a titanium oxide thin film on the substrate surface is started while the pressure is high, a titanium oxide thin film having a predetermined refractive index used for the optical film cannot be obtained.

On the other hand, in the conventional method using TiO alone as a deposition material, it is essential to introduce a gas containing zero atoms into the vacuum chamber, and if the partial pressure of zero is insufficiently adjusted, a brown thin film will result. The problem was that a transparent thin film could not be produced. Furthermore, TiO has the disadvantage that it is several times more expensive than TiO2.

Therefore, the purpose of the present invention is to solve the problem of conventional titanium oxide. It is an object of the present invention to provide a novel method for forming a titanium oxide thin film and a vapor deposition material used therein to eliminate the above-mentioned problems in the method for forming a thin film on a substrate surface.

(Means for Solving the Problems) As a result of intensive studies on vacuum evaporation methods to solve the above-mentioned problems, the present inventors solved the problems by using a mixture of TiO and TiO■ in a specific ratio as a deposition material. They found that this could be solved and completed the present invention.

That is, according to the present invention, the above object is achieved in a method of forming a deposited thin film on a substrate surface by a vacuum evaporation method.
This can be achieved by a method of forming a titanium oxide thin film using an evaporated material in which the content of TiO in a mixture of and TiO2 is 15 to 30% by weight.

In addition, the above purpose is to combine 270 to 85% by weight of TiO and
It can be achieved by a vapor deposition material consisting of a molten mixture of 30 to 15% by weight and forming a thin titanium oxide film on the substrate surface by a vacuum vapor deposition method.

The present invention will be explained in detail below.

As the vacuum evaporation method of the present invention, a commonly used method can be adopted, and the vacuum evaporation tank used for this is, for example, an ordinary one equipped with an electron gun for generating an electron beam and its power source, and is made of copper. Equipment with a tungsten or tantalum hearth liner inside the hearth is commonly used. When using the ion plating method or the IAD method, this becomes possible by equipping the device with a high frequency oscillator or an ion gun, respectively.

The substrate used in the present invention may be made of metal, glass, resin, etc., but is preferably transparent; for example, polymethyl methacrylate resin, polycarbonate resin, polyethylene terephthalate resin, polystyrene resin, transparent As resin, transparent ABS resin. , plastics such as transparent vinyl chloride resin, cellulose acetate resin, diethylene glycol bisallyl carbonate resin, and glass molded products are preferably used.

Also, is there an inorganic or organic thin film on the surface of the above substrate? The formed molded product can also be used as a substrate, and a silicone-based or polyfunctional acrylic-based surface hardening film is formed on the substrate for the purpose of improving the adhesion between the resin substrate and the vapor-deposited thin film. Preferably used is one in which an inorganic thin film is formed on the surface hardened crotch.

The vapor deposition substances used in the present invention include TiO and TiO
The TiO content in the mixture (2) is 15 to 30% by weight, preferably 20 to 25% by weight. The content of TiO in the mixture of rTio and TiO in the present invention is 15 to 30% by weight" means that the weight ratio of TiO and TiO
This refers to cases in which the amounts are measured and prepared or mixed so as to be 30% by weight and 85 to 70% by weight, respectively, or cases in which the prepared and mixed materials are heated above the melting point and melted and mixed.

If the TiO content is less than 15% by weight, the amount of 02 generated is large and it takes too long to pre-treat the evaporated substances, resulting in poor workability, and the temperature inside the vacuum chamber becomes high due to radiant heat from the evaporated substances. Isn't it too much? I don't like it. On the other hand, if it exceeds 30% by weight, no further improvement in the effect is observed, the amount of expensive TiO used increases, and the cost of the evaporated material becomes expensive, which is not preferable.

The shape of the evaporated substance can be any shape as long as it can fit inside the electron beam hearth liner, and examples of the shape used include granular, cylindrical, spherical, and angular shapes.

In the present invention, an oxidized optical film is formed on the surface of a substrate by a commonly used vacuum evaporation method using a vapor deposition material in which the content of TiO in the mixture of TiO and Ti (h) is 15 to 30% by weight. A titanium thin film can be formed.In this case, 75-85% by weight of TiOz and 30-15% of TiO
When a molten mixture obtained by heating % by weight above the melting point as described above is used as the vapor deposition material, it is convenient because there is no need for preparation for measurement and adjustment.

(Effects of the Invention) As described above, according to the present invention, by using an evaporative material in which the content of TiO in the mixture of TiO and TiO is 15 to 30% by weight, it has a transparent appearance. The process of forming titanium oxide thin films, which are suitable for optical film applications, is efficient.
It can also be made cheaper.

(Example) Next, the present invention will be specifically explained using examples.

Examples 1 to 3, Comparative Examples 1 and 2 Cylindrical (15φ x 7t) TiOz (manufactured by Optron ■: bulk density 4.9, melting point 1640°C, refractive index 2.35
) and granular (10-20 mesh) TiO (Osaka Titanium Manufacturing @: bulk density 4.9, melting point 1750°C)
5 types of evaporated substances 1 adjusted so that the content of TiO is θ~30% by weight by mixing 3. 7 g was placed in a tungsten hearth liner provided in a vacuum chamber, and the vacuum chamber was evacuated to 5 X 10-5 Torr. After this, the pressure regulator was set so that the pressure in the vacuum chamber automatically became 5 x 10-' Torr by introducing 0.
m^, Amp was set to 3.5.

Figures 1 to 5 show the pressure changes in the vacuum chamber at this time.
As shown in the figure. FIG. 1 of Comparative Example 1 (TiO: 0%),
What about 2nd E (TiO: 10%) of Comparative Example 2?
■There is a large pressure change due to gas generation, and 5X10-5To
It took a long time to reach rr, and the pretreatment took time. In FIG. 3 of Example 1 (TiO: 15%), the pressure change was small, and in FIG. 4 of Example 2 (TiO: 24%), the pressure change was small.
%), and in FIG. 5 of Example 3 (Tie: 30%), no pressure change is seen at all. That is, from this result, it can be seen that no particular pretreatment is necessary when the TiO content is 24% by weight or 30% by weight.

When the TiO content was 15% by weight, the evaporated material was pretreated for 5 minutes, and when the TiO content was 24% and 30% by weight, the evaporated material without pretreatment was used to form polymethyl methacrylate resin molded products. On the board, 5 x 1 0-5To
At a pressure of rr, the power of the electron beam is 9kV, 2 5
0mA. ．． Amp=3. 5, Ti(h
When a thin film with an optical thickness of 90 nm (measured by spectroscopy) was formed, each titanium oxide thin film was transparent, had a good appearance, and had good adhesion to the substrate.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams for explaining the present invention.
The influence of O content on pressure change in the vacuum chamber is shown. Figure 1 (TiO: O%) Figure 2 (TiO: 10%) Figure 3 (TiO: 15%) Figure 4 (TiO: 24%) Figure 5 (TiO: 30%)

Claims (1)

[Claims] 1. A method for forming a deposited thin film on a substrate surface by a vacuum evaporation method, characterized in that an evaporation material having a TiO content of 15 to 30% by weight in a mixture of TiO and TiO_2 is used. Method for forming titanium oxide thin film. 2. Vapor deposition material consisting of a molten mixture of 270-85% by weight of TiO and 30-15% by weight of TiO.