KR101685474B1 - Composition for forming thin film and optical thin film - Google Patents

Abstract

It is an object of the present invention to provide a composition for forming an optical thin film which can be used with high moisture resistance, low splash, and addition.
In order to solve the above-described problem, w = 19 to 54 and x + y = 81 to 46 (x: y = 1: 99 to 100), where La _w Ti _x Al _y O _z 99: 1), 1.5w + 1.5x + 1.5y? Z? 1.5w + 2x + 1.5y).

Description

TECHNICAL FIELD [0001] The present invention relates to a composition for forming a thin film,

The present invention relates to a composition for forming a thin film for forming a functional thin film such as an optical thin film, and an optical thin film formed by using the composition for thin film formation.

BACKGROUND ART [0002] Conventionally, in many industries, a thin film made of an oxide is widely used as an optical function or a protective layer. For example, there are many technical fields, such as the production of filters and mirrors for color copying machines, mirrors and pickup lenses of optical drive devices and dichroic prisms, antireflection films for spectacle lenses, camera lenses, telescope lenses and displays, A thin film made of an oxide is used.

Thin films of these oxides can be generally formed by a vacuum deposition method, a sputtering method, or the like, but a vacuum deposition method is often selected from the viewpoint of the deposition rate and cost. The vacuum deposition method is a method in which an evaporation material is heated and evaporated and sublimated in a vacuum of about 10 ^-4 to 10 ^-2 Pa to collide and deposit on the substrate surface to form a thin film. Various thin films having a low refractive index can be obtained from a high refractive index by selecting an evaporation material, and various vacuum deposition compositions for vapor deposition on a substrate have been proposed.

In general, as the low refractive index oxide, silicon dioxide, a compound of silicon dioxide and aluminum oxide, an oxide having a refractive index of about middle, aluminum oxide, a compound of aluminum oxide and zirconium oxide, a compound of aluminum oxide and lanthanum oxide are frequently used do. Examples of the oxide having a high refractive index include titanium oxide, niobium oxide, tantalum oxide, zirconium oxide, a compound of titanium oxide and zirconium oxide, and a compound of titanium oxide and lanthanum oxide.

Among them, an oxide thin film having a high refractive index has been widely used as an evaporation material containing titanium oxide, which is relatively high in mechanical strength, rich in resources and cost, and two kinds of lanthanum oxide having high transparency and adhesion as the main components come. In the oxide thin film having a medium refractive index, a compound of lanthanum oxide and aluminum oxide, in which a thin film having a refractive index of 1.6 to 1.9 is obtained with little absorption in a relatively wide wavelength region including the near ultraviolet region Has been widely used. The following techniques are known as technologies relating to the evaporation material containing lanthanum oxide.

For example, Patent Document 1 discloses La ₂ Ti ₂ O _7-y (y = 0.3 to 0.7) in order to obtain an optical thin film having a high refractive index.

Patent Document 2 discloses LaTi _{(1 + y)} O _(3-z) (0 < _y ? 0.2 and 0.3? Z? 0.7), and Patent Document 3 discloses that TiO _{x + z} La ₂ O ₃ (x = 1.5 to 1.8 and z is 10 to 65% based on the total weight of the mixture).

In addition to this, La _1-x Al _{1 + x} O ₃ (x = 0 to 0.84) of Patent Document 4 and La ₂ O ₃ + SiO ₂ of Patent Document 5 as an evaporation material for obtaining an optical thin film having a moderate refractive index ₂ (La ₂ O ₃ : SiO ₂ = 70: 30 to 5:95).

Japanese Patent No. 2720959 Japanese Patent Application Laid-Open No. 11-264068 Japanese Patent Application Laid-Open No. 2002-226967 Japanese Patent No. 3723580 Japanese Patent No. 3723620

In the evaporation material containing two or more kinds of oxides disclosed in Patent Document 5, generally, the oxide having a high vapor pressure is preferentially evaporated, and the oxide having a low vapor pressure remains in the evaporation source. Therefore, when an unused evaporation material is added to the evaporation material residue after vacuum deposition, there arises a problem that the element composition of the thin film to be formed and the evaporation source are changed. Therefore, it is difficult to replenish a new evaporation material after the use of the evaporation material after use, which may be disadvantageous in terms of cost and resource protection.

On the other hand, although the evaporation materials made of lanthanum oxide, titanium oxide, lanthanum oxide and aluminum oxide disclosed in Patent Documents 1 to 4 are composite compositions composed of two kinds of oxides, a new evaporation material is deposited on the evaporation material residue after deposition It can be used supplementally. This is because the evaporation characteristics of lanthanum oxide, titanium oxide and aluminum oxide are relatively close to each other, so that they are harmonized and evaporated, and the composition of the deposited thin film and the deposition residue is hardly changed.

Here, since the antireflection film of the spectacle lens is used in harsh environments such as friction due to wiping of contamination, cleaning by ultrasonic cleaning, cleaning by an acidic detergent or an alkaline detergent, or use for a long period of time, , A higher durability is required.

The oxide thin films and evaporation materials having lanthanum of Patent Documents 1 to 5 have a problem in stability in the atmosphere. According to the knowledge of the present inventors, if the deposited thin film is left in the atmosphere for a certain period of time, not only the film characteristics are changed but also white turbidity, cracks, film peeling and the like may occur, which is a serious problem from the standpoint of stability . Further, if the evaporation material is left in the atmosphere for a certain period of time, it may be expanded or collapsed in powder form, which may not only increase the splash but also become unusable for vacuum evaporation. These are considered to be attributed to the fact that lanthanum oxide reacts with moisture and carbon dioxide in the air and changes from oxides to hydroxides or the like when free lanthanum exists in the optical thin film or the evaporation material. Further, it is considered that the above-described thin film containing lanthanum oxide is used in an atmosphere having a high humidity such as in a bathroom or rainy day, or is washed in a liquid containing water such as detergent cleaning or ultrasonic cleaning Clouding, cracking, film peeling, etc. of the thin film may occur.

The thin film made of lanthanum oxide and titanium oxide in Patent Documents 2 and 3 has a higher composition ratio of titanium than the thin film of Patent Document 1. As a result, favorable lanthanum oxide is difficult to generate, stability in the atmosphere is improved, but it can not be said to be sufficient. In some cases, such as the thin film of Patent Document 1, film characteristics change, film peeling, or cloudiness may occur. In addition, since the content of titanium oxide is high, splashes are often generated during vacuum deposition.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a composition for forming an optical thin film which can be used with a high moisture resistance, a low splash and a supplementary use, and also has a high moisture resistance, And to provide an optical thin film having alkalinity.

For thin film formation composition of the present invention, when the composition formula as _{La w Ti x Al y O z} (w + x + y = 100, w = 19~54, x + y = 81~46 (x: y = 1: 1.5w + 1.5x + 1.5y? Z? 1.5w + 2x + 1.5y).

Further, the optical thin film of the present invention is characterized by being formed by vacuum evaporation of the composition for thin film formation of the present invention.

The composition for forming a thin film of the present invention has high stability against moisture in the air, generates little splash during vacuum deposition, and can be supplemented.

Further, the optical thin film of the present invention can simultaneously satisfy high moisture resistance, adhesion, transparency, acid resistance and alkali resistance. Therefore, by using this optical thin film, the stability of the thin film of the optical component or the like in the atmosphere improves, and the defects such as opacity and film peeling can be reduced. In addition, an optical component having high moisture resistance, acid resistance, alkali resistance and transparency can be provided.

1 is a triangular diagram showing the composition range of lanthanum (La), titanium (Ti) and aluminum (Al) elements of the composition for thin film formation of the present invention.
Fig. 2 is a triangular diagram showing the composition ratios of lanthanum (La), titanium (Ti) and aluminum (Al) elements in the composition in Examples.
FIG. 3 is a view for explaining a method of reading the triangles in FIGS. 1 and 2. FIG.

Hereinafter, the present invention will be described in detail.

For thin film formation composition of the present invention, when the composition formula as _{La w Ti x Al y O z} (w + x + y = 100, w = 19~54, x + y = 81~46 (x: y = 1: 1.5w + 1.5x + 1.5y? Z? 1.5w + 2x + 1.5y).

Fig. 1 shows the composition ranges of lanthanum, titanium and aluminum elements of the composition for forming a thin film of the present invention. Here, the method of reading the triangular figure shown in Fig. 1 will be described with reference to Fig. In Fig. 3, the thick line (upper) shows that the composition of La (w) = 60 mol% although the ratio of Ti and Al (x and y) is different. The thick dotted line represents Ti: Al (x: y) = 40: 60 although the ratio of La (w) is different. In the above, the point P indicates the composition of (w, x, y) = (60:16:24).

The composition of the lanthanum, titanium and aluminum elements in the thin film forming composition of the present invention shown in Fig. 1 is such that the respective points (units: mol%) of A, B, C and D shown below are in a range surrounded by a straight line And on each straight line.

A (w, x, y) = (19, 0.81, 80.19)

B (w, x, y) = (19, 80.19, 0.81)

C (w, x, y) = (54, 45.54, 0.46)

D (w, x, y) = (54, 0.46, 45.54)

When w exceeds 54, the characteristics of the lanthanum oxide are liable to be manifested, and the resulting thin film or evaporation material tends to react easily with acid, alkali and moisture. On the other hand, when the value of w is less than 19, it is not preferable from the standpoint that characteristics unique to aluminum oxide and titanium oxide, which tend to cause absorption, are easily produced and adhesion is deteriorated.

In addition, if one of them is too large in the range of x: y = 1: 99 to 99: 1, the effect of the simultaneous presence of lanthanum, titanium and aluminum, that is, the effect of improving the acid resistance, alkali resistance, Is difficult to be expressed.

Further, when z is less than 1.5w + 1.5x + 1.5y, the resulting thin film tends to become a low-grade oxide, so that absorption is likely to occur in the thin film, which is not preferable.

The composition of the present invention has a composition of y? 10, that is, in Fig. 1, the respective points (units: mol%) of the following B ', B, C and C' are surrounded by a straight line It is preferable that each line is on a straight line. With this range, it is possible to obtain an optical thin film having a high refractive index with high scratch resistance by vacuum evaporation.

B '(w, x, y) = (19, 71, 10)

B (w, x, y) = (19, 80.19, 0.81)

C (w, x, y) = (54, 45.54, 0.46)

C '(w, x, y) = (54, 36, 10)

The composition of the present invention is more stable in the atmosphere than a compound comprising only an oxide of lanthanum and titanium or a compound containing only an oxide of lanthanum and aluminum. The reason is that the simultaneous presence of lanthanum oxide, titanium oxide and aluminum oxide promotes relaxation and diffusion of the crystal lattice during sintering and synthesis, so that molecules between neighboring lattices are easily bonded to each other, It is believed that it is difficult to exist due to free (free) aggregation.

In the composition of the present invention, x &lt; = 10, that is, in FIG. 1, the respective points (units: mol%) of A, A ', D' and D shown below are surrounded by a straight line And it is also preferable that they are on each straight line. With this range, an optical thin film having a medium refractive index with high transparency up to the near ultraviolet region can be obtained by vacuum evaporation.

A (w, x, y) = (19, 0.81, 80.19)

A '(w, x, y) = (19, 10, 71)

D '(w, x, y) = (54, 10, 36)

D (w, x, y) = (54, 0.46, 45.54)

The composition of the present invention may be any of a compound and a mixture, but is preferably in the form of a compound. In the present invention, the term &quot; compound &quot; means a compound in which each element is chemically bonded and stabilized, and a compound is a compound in which two or more elements or compounds containing such elements are merely mixed and not chemically bonded State.

When the compound is a compound, since the lanthanum oxide forms a stable compound with titanium oxide or aluminum oxide, the lanthanum oxide rarely exists alone. Therefore, absorption of moisture or carbon dioxide is scarcely caused, so that generation of harmful gas at the time of film formation can be suppressed, and splash at the time of vapor deposition is reduced, so that a thin film can be stably obtained. On the other hand, in the form of a mixture, since lanthanum oxide absorbs water and carbon dioxide in the atmosphere, there is a possibility that harmful gas generation or splashing may occur during vacuum deposition.

The composition of the present invention is more preferably a sintered body or a molten body.

The sintering pressure and temperature vary depending on the element composition ratio and the specific surface area of the powder, and are preferably 1350 DEG C or higher in vacuum. When sintering or melting in a vacuum of 10 &lt; ^-2 &gt; Pa or lower, splashes and gas generation such as oxygen can be further reduced during deposition. If the temperature is lower than 1350 DEG C, there is a possibility that the sintering reaction becomes insufficient, and there is a possibility that unreacted lanthanum oxide remains and the resultant sintered body has low strength and low density. The sintering time is appropriately selected according to the sintering temperature, and is usually one hour or more. If it is less than 1 hour, there is a possibility that the sintering reaction becomes insufficient.

When the composition of the present invention is sintered or melted, a composition of a low-grade oxide in which a low-grade titanium oxide, metallic titanium, titanium hydride, metallic aluminum or the like is added and reduced may be used. By using a low-grade oxide, the generation of oxygen gas liberated from the composition at the time of vapor deposition can be reduced.

The shape of the composition of the present invention may be any of pellet, tablet, and granular, but it is preferably used after being dissolved by electron beam before vapor deposition, and granules are particularly easy to use.

The composition of the present invention may contain other elements within a range not affecting the present invention. That is, not only impurity elements inevitably present in the composition of the present invention but also other elements may be added as needed within the range not affecting the present invention.

Next, the optical thin film of the present invention will be described.

The optical thin film of the present invention is formed on a substrate such as glass or synthetic resin by vacuum vapor deposition of the composition of the present invention and has a refractive index of about 1.7 to 2.2. The deposition can be performed by an ordinary method using an electron beam.

According to the knowledge of the present inventors, aluminum oxide, lanthanum oxide and titanium oxide are sufficiently transparent substances as optical thin films, and all have evaporation characteristics close to each other.

Further, it is considered that the presence of the oxides of lanthanum, titanium, and aluminum at the same time causes the lattice mobility of the evaporation material and the migration of the evaporation material to be promoted on the substrate at the time of film formation. Therefore, it is considered that the laminar acid lanthanum or the like in the thin film is hardly present in the glass or agglomerated state, so that the moisture resistance is improved and the physical and chemical stability such as adhesion of the thin film, acid resistance and alkali resistance are improved. This effect does not occur in a thin film made of only lanthanum oxide and aluminum oxide, and does not occur in a thin film made of only lanthanum oxide and titanium oxide.

The optical thin film of the present invention can be used as a thin film for forming a multilayer thin film such as an antireflection film, an optical filter, an optical mirror, and an optical prism.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

&Lt; Preparation of composition >

Lanthanum oxide powder (La ₂ O _3, purity of 99.99%, average particle diameter 2㎛), titanium oxide powder (TiO _2, purity of 99.99%, average particle diameter 1㎛), metallic titanium powder (Ti, purity: 99%, average particle diameter 7㎛ ) And aluminum oxide powder (Al ₂ O ₃ , purity 99.99%, average particle diameter 0.6 탆) were weighed out in the weight ratios shown in Table 1 so as to have the composition formula (calculated value) shown in Table 1.

Each powder thus obtained was mixed with a ball mill for 48 hours. Then, a dispersing agent was added to the mixed powder and further mixed with a ball mill for 8 hours. The obtained mixture was cold-formed at a pressure of 98066.5 kPa (1000 kgf / cm ² ), pulverized and granulated. Subsequently, using a vacuum heating device with a degreasing function, the granular sintered body was obtained by heating at a temperature shown in Table 1 in a vacuum of 1 × 10 ^-2 Pa or less for 24 hours.

[Table 1]

&Lt; Formation of deposited thin film &

The composition thus obtained was charged into an electron beam deposition hearth liner disposed in a vacuum deposition apparatus (deposition distance: 1100 mm), and the inside of the apparatus was evacuated to a pressure of 1 x ^10-3 Pa. Subsequently, the composition is evaporated by the electron beam, and the optical film thickness is adjusted to a desired film thickness (for example, a wavelength of 550 nm) within a range of 1/4? 4? (Wavelength? = 540 nm) Lt; RTI ID = 0.0 &gt; A / sec. &Lt; / RTI &gt;

&Lt; Evaluation of Composition >

The composition thus prepared was evaluated by the following test method. The results are shown in Table 2.

(1) Composition analysis

The composition was pulverized in the form of powder with agate, dissolved by alkali melting method, and yttrium nitrate solution was added as an internal standard substance to prepare a sample liquid. Subsequently, the resulting solution was introduced into an ICP emission spectrochemical analyzer, and quantitative analysis of La, Ti and Al elements was performed by an internal standard method. The ICP emission spectroscopic analyzer used the VISTA PRO AX manufactured by Varian Inc. to observe the emission intensity by axial observation.

Further, oxygen was quantified by inert gas dissolution-infrared absorption method. The apparatus was an EMGA-650 manufactured by Horiba Seisakusho Co., Ltd., and the measurement was performed in accordance with the infrared absorption method in accordance with the general rule of oxygen quantitative method of JIS-Z2613 metal material.

From the analysis results obtained, the chemical composition formula of the composition was calculated. As shown in Table 2, it was confirmed that the element composition was almost the same as the calculated value shown in Table 1 in all of the examples and the comparative examples.

The composition ratios of the lanthanum, titanium and aluminum elements in each composition are shown in Fig.

(2) Moisture resistance

The composition was stored for 30 days in a constant temperature and humidity bath at a temperature of 35 DEG C and a relative humidity of 95% RH, and the change in appearance was observed to measure the change in weight. An electronic balance was used to measure the change in weight.

The obtained results were evaluated based on the following criteria.

◎: There is no change in appearance for 30 days, and weight increase due to moisture absorption is less than + 1 wt%

○: There was no change in appearance for 30 days, but the weight increased by 1 wt% or more due to moisture absorption

DELTA: Composition collapses or swells within 1 day to 30 days

X: Composition disintegrates in less than 1 day

As shown in Table 2, it was confirmed that all of the compositions of the present invention had sufficient stability against humidity in the atmosphere.

On the other hand, in Comparative Examples 23 to 25 and Comparative Example 30, the moisture resistance was lower than those of Examples and Comparative Examples. These are considered to have absorbed moisture in the atmosphere because the content of lanthanum is too high.

(3) Supplemental availability

After forming a vapor-deposited thin film (optical film thickness of 1/4?) On a glass substrate (synthetic quartz), the reduced minute composition was supplemented. The change of the refractive index of the deposited thin film and the change of the element composition of the composition residue when this was repeated 20 times were examined.

The refractive index was calculated from the reflectance of the thin film in the following formula (1). For the measurement of reflectance, Lambda 900 manufactured by Perkin Elmer was used.

[Number 1]

The element composition of the residue of the composition was analyzed using an ICP emission spectrochemical analyzer as in the above-mentioned (1) composition analysis.

The obtained results were evaluated based on the following criteria.

[Variation of Refractive Index of Thin Film]

&Amp; cir &amp;: The difference in refractive index between the first film formation and the 20th film formation is less than 0.01

?: Difference in refractive index between the first film formation and the 20th film formation is 0.01 or more and less than 0.02

DELTA: difference in refractive index between the first film forming and the film forming 20th time is 0.02 or more and less than 0.05

X: Difference in refractive index between the first film formation and the 20th film formation is 0.05 or more

[Composition variation of composition residue]

?: The difference in La content between the film before film formation and after film formation 20 times is less than ± 1%.

?: The difference in the La content in the composition before the film formation and after 20 times of the film formation is within ± 1% or more and less than ± 2%.

DELTA: Difference in La content in the composition before deposition and after 20 times of film formation is within ± 2% or more and less than ± 3%.

占 Difference in La content in the composition before deposition and after 20 times of film formation is 占 3% or more.

As shown in Table 2, the oxides of lanthanum, titanium and aluminum, the oxides not containing aluminum, and the oxides not containing titanium showed little variation in element composition.

Further, the refractive index of the thin film hardly changed. The refractive index varies in some comparative examples because absorption occurs in the thin film due to oxygen deficiency in the thin film, and an accurate refractive index can not be calculated.

From these results, it was confirmed that the composition of the present invention can be supplementarily used.

(4) splash

The state of occurrence of splash when the composition was irradiated with an electron beam at the time of the deposited thin film was observed, and evaluation was carried out based on the following criteria.

◎: Splash hardly occurs

○: A little splash occurred

△: Splash occurred frequently

X: Splash occurs at all times

As shown in Table 2, no occurrence of splash was observed in the composition of the present invention.

On the other hand, in some comparative examples, a lot of splashes occurred. In Comparative Examples 23 to 25 and Comparative Example 30, since the content of lanthanum was high, it was considered that the water was absorbed in the atmosphere and splash occurred. Further, in Comparative Example 32, the characteristics of titanium oxide having many splashes were confirmed.

From these results, it was confirmed that the composition of the present invention has a low splash composition.

(5) Attachment state of fine particles to the substrate

The number of fine particles adhered on a chewing plate glass substrate (80?) By splashing or the like was observed with an optical microscope and evaluated according to the following criteria.

◎: Mounting position 0

O: Mounting position 1 to 2

?: Attachment point 3 to 4

X: At least 5 points of attachment

As shown in Table 2, in the composition of the present invention, no fine particles were observed on the substrate. On the other hand, in some comparative examples, many fine particles were observed. It is considered that the comparative example in which fine particles are observed exhibited the characteristics of titanium oxide and aluminum oxide, which are liable to adhere to fine particles.

From these results, it was confirmed that the composition of the present invention obtained a thin film having a small adhesion of fine particles.

[Table 2]

&Lt; Evaluation of deposited thin film &

The formed thin film was evaluated by the following test method. The results are shown in Table 3.

(6) Moisture resistance

The thin film (glass substrate: BK7, optical film thickness: 4?) Was stored for 30 days in a constant temperature and humidity bath at 35 DEG C and 95% RH to observe changes in the refractive index of the thin films. The refractive index was obtained in the same manner as the above-mentioned (3) supplementary utilization.

The obtained results were evaluated based on the following criteria.

&Amp; cir &amp;: No change in appearance and a variation value of refractive index of less than 0.03

○: The appearance does not change, but the refractive index changes by 0.03 or more

?: Clouding appeared on appearance

X: Peeling or cracking occurred on the appearance

As shown in Table 3, it was confirmed that all of the compositions of the present invention had high stability against moisture in the air.

On the other hand, in Comparative Examples 20 to 25 in which the contents of lanthanum were large, in Comparative Examples 15 to 19 in which aluminum was not contained, and in Comparative Examples 7 to 11 in which titanium was not contained, .

(7) Absorption rate (Visible area)

The absorption rate in the visible light range was calculated from the spectral transmittance and the spectral reflectance of a thin film (glass substrate: synthetic quartz, optical film thickness: 3/4?) As "absorption rate = 100% - transmittance - reflectance". The transmittance and the reflectance were measured using Lambda 900 manufactured by Perkin Elmer.

The calculated absorption rate was evaluated based on the following criteria.

◎: Absorption rate less than 0.5%

O: absorption rate 0.5% to 0.7%

?: Absorption rate 0.7% to 1.5%

X: absorption rate 1.5% or more

As shown in Table 3, in the composition of the present invention, absorption of the thin film was small.

On the other hand, in some comparative examples, absorption of the thin film was large. In Comparative Examples 33 to 35, since the oxygen content of the composition is small, it is considered that the obtained thin film becomes a low-grade oxide and absorption occurs. For the comparative example in which other absorption is large, it is considered that the characteristics of titanium oxide and aluminum oxide, in which absorption of a thin film is prone to occur, are exhibited.

From these results, it can be confirmed that the composition of the present invention provides a thin film having high transparency.

(8) Refractive index

The refractive index of the thin film (glass substrate: synthetic quartz, optical film thickness: 3/4?) Was obtained in the same manner as in the above-mentioned (3) replenishment utilization.

As shown in Table 3, it can be confirmed that a wide thin film having a refractive index of about 1.7-2.2 can be formed in the composition of the present invention.

(9) Transparency in the near-infrared region (absorption edge at the outer side)

The absorptivity was calculated from the spectral transmittance and the spectral reflectance in the near-infrared region (300 to 400 nm) of the thin film (glass substrate: synthetic quartz, optical film thickness: 3/4?) As "absorption rate = 100% -transmittance-reflectance". For measurement of the transmittance and reflectance in the near-infrared range, Lambda 900 manufactured by Perkin Elmer Co., Ltd. was used.

Here, the evaluation was carried out based on the following criteria, assuming that the wavelength at which the calculated absorption rate is 3% or more is taken as the absorption edge at the extraterrestrial side.

⊚: absorption edge less than 330 nm

O: Absorptive layer 330 nm or more

As shown in Table 3, in Examples 6 to 11 and Comparative Examples 7 to 11 in which the content of Ti was low, transparency was remarkably excellent especially in the near-infrared region.

(10) Acid resistance (JIS-K5400 8. 22)

The thin film (glass substrate: BK7, optical film thickness: 4?) Was immersed in diluted sulfuric acid (liquid temperature 35 ° C) of 5 w / v% for 168 hours and the change of the thin film was observed every 24 hours, .

◎: No change

○: It does not change until within 24 hours, but after that, there is a change other than film peeling such as opacity

Δ: Within 24 hours, a change other than film peeling such as opacity and crack occurred

X: peeling occurred within 24 hours

As shown in Table 3, it was confirmed that all of the compositions of the present invention were stable to acids.

On the other hand, in Comparative Examples 20 to 25 in which the content of lanthanum was large, it was confirmed that the acid resistance was inferior as compared with the composition of the present invention. It is considered that the characteristics of the lanthanum oxide having low acid resistance and low water resistance are exhibited. Further, in Comparative Examples 15 to 19 containing no aluminum and Comparative Examples 7 to 11 containing no titanium, it was confirmed that the acid resistance was lower than that of the composition of the present invention.

(11) Alkali resistance (JIS-K5400 8. 21)

A thin film (glass substrate: BK7, optical film thickness: 4?) Was immersed in a 5 w / v% aqueous solution of sodium carbonate (liquid temperature 35 ° C) for 168 hours and the change of the thin film was observed every 24 hours, .

◎: No change

○: It does not change until within 24 hours, but after that, there is a change other than film peeling such as opacity

Δ: Within 24 hours, a change other than film peeling such as opacity and crack occurred

X: peeling occurred within 24 hours

As shown in Table 3, it was confirmed that all of the compositions of the present invention were stable against alkali.

On the other hand, in Comparative Examples 20 to 25 in which the content of lanthanum was large, the alkali resistance was inferior as compared with the composition of the present invention. It is considered that the characteristics of the lanthanum oxide having low alkali resistance and low water resistance are exhibited.

(12) Adhesion (JIS-R3255)

The adhesion of the thin film (glass substrate: synthetic quartz, optical film thickness: 4?) Was evaluated by a micro scratch test. CSR-02F made by Lescas was used as the tester. The measurement conditions were a diamond indenter radius of 5 占 퐉, a stage speed of 10 占 퐉 / s, a stage angle of 3DEG, a gain of 1000, and an excitation level of 90 占 퐉.

The value of the critical load sensor output obtained by the micro-scratch test was evaluated based on the following criteria.

?: 50 mN or more

○: 30 mN or more and less than 50 mN

?: 20 mN or more and less than 30 mN

×: less than 20 mN

As shown in Table 3, in the composition of the present invention, all of the adhesives were relatively high, and in particular, the adhesiveness was high in Examples 1 to 2, 5 and 15 to 20.

On the other hand, in Comparative Examples 23 to 25 and Comparative Example 30 in which lanthanum content was high, Comparative Examples 26 to 29 in which content of lanthanum was low, Comparative Examples 15 to 19 in which aluminum was not contained, and Comparative Examples 7 to 11 in which titanium was not contained Resulting in poor adhesion.

(13) Composition analysis

Qualitative analysis of an element contained in a thin film (glass substrate: synthetic quartz, optical film thickness: 4?) Was performed using a wavelength dispersive X-ray fluorescence spectrometer (WD-XRF). The analytical apparatus used was RIX 3000 manufactured by Rigaku Corporation.

As shown in Table 3, the detection element in the thin film obtained by the vacuum deposition was in agreement with the element of the composition, and it was confirmed that the optical thin film of the present invention contained lanthanum, titanium and aluminum elements.

<Overall evaluation>

The evaluations of the above (2) to (7) and (9) to (12) were summarized and evaluated.

&Amp; cir &amp;: The evaluation shows that the number of items of &quot; 0 &quot;

○: The evaluation shows that there are two or more items of ○, and the items of △ and × are 0

△: The evaluation has at least one item of △, and the item of × is 0

X: More than one item of evaluation x

As shown in Table 3, the composition of the present invention is a composition that is stable to moisture in the air, has little splashing and fine particle adhesion to the substrate, and has little variation in composition even when supplemented.

Further, the optical thin film obtained from the composition of the present invention is an optical thin film composed of elements of lanthanum, titanium, aluminum and oxygen which simultaneously satisfy high moisture resistance, adhesion, transparency, acid resistance and alkali resistance.

[Table 3]

Claims (4)

When it referred to the composition formula _{La w Ti x Al y O z} (w + x + y = 100, w = 19~54, x + y = 81~46 (x: y = 1: 99~99: 1), 1.5w + 1.5x + 1.5y? Z? 1.5w + 2x + 1.5y). The method according to claim 1,
And y? 10 in the above composition formula. The method according to claim 1,
X &lt; / = 10 in the above composition formula. An optical thin film formed by vacuum evaporation of the composition for forming a thin film according to any one of claims 1 to 3.

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