JP2768996B2 - Anti-reflection coating for optical articles made of synthetic resin - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an antireflection film for an optical article made of synthetic resin, and in particular, to an optical lens such as an eyeglass lens, an optical lens attached to a display screen of a word processor, a computer, or the like. The present invention relates to an antireflection film suitable for a filter, an instrument cover of an automobile, and the like.

[Conventional technology]

There are many known examples of an antireflection film for an optical article, and an antireflection film using a synthetic resin as a substrate is also a film of an inorganic substance formed by vacuum deposition or an organic polymer formed by solution coating or the like. Many known examples of a film of a substance are disclosed. Numerous combinations having various characteristics have been proposed for the film configuration of the antireflection film, and a five-layer antireflection film related to the present invention is also disclosed in JP-A-49-8603.
No. 2, JP-A-59-208501, and the like have been proposed.

[Problems to be solved by the invention]

However, most of the above-mentioned conventional techniques aim at lowering the reflectance in the visible region, and in particular, many aim at lowering the reflectance over as wide a band as possible in the visible region.
The same applies to the above two known examples. When lowering the reflectance over a wide band by using a multilayer film, the interference color reflected by the film shows various colors that are colorless or faint. There is a disadvantage that it is difficult to obtain color. Although the interference color may not be a problem depending on the application, it is an important factor in appearance quality of the optical article as well as the low reflectance, and a large variation in the interference color is not preferable and also affects the yield. A main object of the present invention is to obtain a film which stably gives a preferable interference color while reducing the reflectance.

In the five-layer reflecting film described in claim 1 of JP-A-59-208501, the first, third and fifth layers are made of the same low refractive index material and have a refractive index of 1.35. It must be in the range of ~ 1.47. As such a low refractive index material, known Si
In addition to O ₂ , it is limited to metal fluorides such as MgF ₂ , LiF, and CaF ₂ , all of which have a problem in adhesion to a synthetic resin substrate. In other words, there is a limit to the temperature that the substrate can withstand during the formation of the thin film, and the affinity with the substrate is poor, so there is a high risk that the film will not be able to withstand long-term moisture absorption / desorption or cleaning using a cleaner. Another object of the present invention is to firmly adhere to a synthetic resin substrate, to have excellent practical durability such as temperature change, humidity change, contact of a solvent such as a cleaner, light friction indoors, and anti-reflection properties for a long time. The purpose is to obtain a film having a small change and a well-balanced performance.

[Means for solving the problem]

The present inventors have conducted extensive and extensive studies on the materials and the optical film thickness constituting the antireflection film in order to solve the above problems, and as a result, have found an extremely excellent film structure, and have completed the present invention.

That is, the object of the present invention is that the refractive index is 1.4
A five-layer antireflection film provided on the surface of a synthetic resin substrate having a refractive index of 1.5 to 1.7, and a second layer and a fourth layer having a refractive index of 1.9 to The third layer and the fifth layer are made of a material having a refractive index of 1.4 to 1.5, and the first to fifth layers have optical thicknesses n ₁ d ₁ and n ₁ .
_{2 d 2, n 3 d 3} , n 4 d 4, n 5 d 5 is to provide an antireflection film of a synthetic resin article, characterized in that each formula (1) to (5) Mitsurusu.

0.0625λ ≧ n ₁ d ₁ ≧ 0.0375λ (1) 0.0625λ ≧ n ₂ d ₂ ≧ 0.0375λ (2) 0.1125λ ≧ n ₃ d ₃ ≧ 0.0875λ (3) 0.450 λ ≧ n ₄ d ₄ ≧ 0.400 λ (4) 0.250 λ ≧ n ₅ d ₅ ≧ 0.225 λ (5) (where λ is a design wavelength) Further, the object of the present invention is as follows. a SiOx material layers, material of the second layer and the fourth layer is TiO ₂ or ZrO _2, the antireflection film material of the third layer and the fifth layer is characterized by a SiO ₂ To provide.

 Hereinafter, the present invention will be described in detail.

The synthetic resin used as the substrate does not matter whether it is thermoplastic or thermosetting, but it needs to be a transparent or colored transparent resin, and the refractive index of the easily obtainable synthetic resin is in the range of 1.4 to 1.6. Some can be used. Examples of these resins include polystyrene, polycarbonate, rigid polyvinyl chloride, polyethylene terephthalate, polymethyl methacrylate, lead-containing methacrylic resin, cellulose triacetate resin, and the like, and polyfunctional (meth) acrylic resins. Alternatively, a resin substrate which has been subjected to a polyorganosilane-based surface hardening treatment is particularly preferable from the viewpoint of film adhesion.

Specific examples of the thin film forming substance used in the present invention are shown below.
The substance having a refractive index of 1.5 to 1.7 forming the first layer thin film is Al
It can be selected from ₂ O ₃ , SiOx, Y ₂ O ₃ , WO _3, etc., but since the first layer is formed, adhesion to the substrate is required, good affinity with the synthetic resin surface, good binding force Especially strong SiOx (2
>X> 1) is optimal. The so-called high-refractive-index substance having a refractive index of 1.9 to 2.2, which forms the thin films of the second and fourth layers, is Sb ₂ O
₃ , SnO ₂ , TiO ₂ , ZnO, ZrO _2, etc., but TiO ₂ and ZrO ₂ are preferable from the viewpoint of stability of film forming accuracy. However, since it is used for the intermediate layer, the restriction on the durability performance is small. Refractive index of 1.4 to form thin films of the third and fifth layers
Called low refractive index material AlF ₃ of 1.5, CaF _2, SiO ₂ can be selected from such scratch resistance dense film having been required SiO ₂ is particularly so constituting the fifth layer of the outermost layer preferable.

The method for forming the thin film used in the present invention can be a known method such as vapor deposition, ion plating and sputtering of an inorganic substance such as a metal oxide.

SiOx forms a thin film having a refractive index of 1.6 to 1.7 (or 1.6 to 1.65 for a thin film thickness of about the formula (1) as in the present invention) by a normal thin film forming method. It has an instability that decreases and eventually decreases to about 1.5. As a result, the anti-reflection effect and the interference color gradually change, resulting in a film having poor anti-reflection effect and an unstable factor that changes to an undesired interference color. In the present invention, a film thickness configuration that effectively uses SiOx is adopted in consideration of this change. That is, the thickness of SiOx used for the first layer is made as thin as possible to the minimum necessary, and the second layer to the fifth layer are obtained with a suitable thickness configuration by a combination of a high refractive index material and a low refractive index material. is there. This effect is shown below with simulations and actual examples. FIG. 5 (simulation) and FIG.
The data of the figure (Example) is displayed collectively in Table 3.
In Table 3, the values of Y _S and Y _P are weighted average reflectances and are characteristic values that appropriately represent the antireflection effect over the entire visible range. Y _S and Y _P change with a decrease in n ₁ due to a long-term change with time, but the changes are small and show a substantially constant or decreasing tendency. That is, the anti-reflection effect remains almost constant or is improved. The change in the interference color is represented by C _{1 to} C _{5 in} FIG.
As shown in (1), there is an excellent feature that the color stays in a substantially constant color range (blue or blue-violet).

The specific and quantitative expression method of the interference color and the weighted average reflectance used in the present invention will be described below.

That is, the reflected interference color (A) (usually represented by x, y or u, v values) represented by the CIE chromaticity in the International Commission on Illumination (CIE1931) chromaticity coordinates is expressed by the following equation (6):
(7) and (8). According to CIE's XYZ color scheme,
For three stimulation values of X, Y and Z, In addition, JIS Z8727-1971 gives the following equations (9), (10), and (11) using a weighting factor as a method for measuring an object color.

_{X = Σ (R i × P} λ λi) ····· (9) Y = Σ (R i × P λ λi) ····· (10) Z = Σ (R i × P λ λi) · (11) where i is the wavelength and is applied in the range of 380 to 780 nm. R _i is the spectral reflectance, and P _{λ λi} , P _{λ λi} , P _λ
λi is the weighting factor for each of the three stimulation values,
The JIS gives a weight coefficient value for a standard light source.

The spectral energy intensity of the measuring light source S, a spectral luminous efficiency for CIE standard observer V (scotopic V _s, photopic
V _p ), when the measured value of the spectral reflectance of the surface to be measured is R, the weighted average reflectance (B) is expressed by equation (12) for scotopic vision and by equation (13) for photopic vision. , expressed in units% of the time to the R _i% units.

The method of design calculation of the antireflection film will be described below.

Has a specific preferred interference color, by determining the refractive index and optical thickness of the thin film weighted average reflectance of the (Y _s and / or Y _p) constitute the anti-reflection film so as to minimize And a method for designing a multilayer antireflection film. That is, as shown in the flow chart of FIG. 7 describing an example of a three-layer film, first, the refractive index of the substrate, the high-refractive-index material, the low-refractive-index material, and if necessary, the refractive index of the intermediate-refractive-index material are selected and input, Then, the optical film thickness is set to λ / 4 (this is 100
%), Each layer is sequentially input at 10% intervals, and the theoretical reflectance of the multilayer film is calculated by a computer to calculate the spectral reflectance. Next, the interference color and the weighted average reflectance are calculated using the spectral reflectance, and it is determined whether the interference color and the weighted average reflectance are within the target interference color range or not. Thus, some appropriate film configurations can be selected. Theoretical calculation is again performed on the plurality of candidate groups, including the periphery thereof, with an optical film thickness in increments of 5% of λ / 4 to narrow down the appropriate range of the plurality of candidate groups.
Finally, the optimum film configuration can be determined in consideration of controllability of film formation, practical evaluation of durability performance, and the like.

The optical film thickness is usually expressed in units of λ / 4, but in the present invention, the film thickness of λ / 4 is hereinafter expressed as 100%, and the film thickness is expressed in proportion to this. According to this expression, equations (1) to (5) are rewritten as (1) 'to (5)'.

Here, λ is a design wavelength, which is selected from one wavelength in visible light, and in the present invention, 550 to 570 nm is used.

If the optical thickness is out of the range, the weighted average reflectance is 1% or less, the interference color of blue or blue-violet,
It is extremely difficult to satisfy all three conditions, that is, when the refractive index of the layer changes between 1.7 and 1.5. In addition, the above range does not always coincide with the range indicating blue or bluish purple, and the CIE chromaticity coordinates in FIG.
It is preferable to use a combination of optical film thicknesses such that the interference color belongs to a range satisfying both (4) and (15).

y ≧ 2x−0.235 and y ≧ 1.5x−0.135 (14) y ≦ 0.5x + 0.15 (15) This color range is determined to be favorable as a result of visual observation by a number of OA operators. This is the coordinate range of the interference color obtained by statistically processing the colors.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1: Kyowa Gas Chemical Industry Co., Ltd. Paragurasu transparent plate (methacrylic resin cast plate, thickness 2 mm, refractive index n ₀ = 1.49, a total light transmittance of 93%) as a substrate, a first layer SiOx, Vacuum deposition of the second and fourth layers TiO ₂ , the third and fifth layers SiO ₂
Performed on both sides of the substrate under a vacuum of ^-5 Torr. SiOx is SiO
TiO ₂ was degassed by an electron beam heating method after degassing, and SiO ₂ was processed by an electron beam heating method for granular materials under pressure control by gaseous oxygen. The refractive index of the thin film of each layer is approximately n ₁ =
1.60, n ₂ = 1.95, n ₃ = n ₅ = 1.45, n ₄ = 2.00, and the optical film thicknesses are n ₁ d ₁ = λ / 4 × 20% and n ₂ d ₂ = λ / 4 ×, respectively. 20
%, N ₃ d ₃ = λ / 4 × 40%, n ₄ d ₄ = λ / 4 × 170%, n ₅ d ₅ = λ /
The film configuration was 4 × 95% as shown in the schematic diagram of FIG. The deposited product was measured using a SOM200 type multicolor optical monitor manufactured by Showa Vacuum Co., Ltd., and the reflectance curve shown in FIG. 3 and the data shown in Table 2 were obtained. Using the reflectance data at 13 wavelengths in Table 2, data processing is performed by the above-described quantitative expression method of the interference color and the weighted average reflectance, and x = 0.163 and y = 0.198 are calculated as interference colors. it turns out that belong to the range of the chromaticity coordinates a CIE blue shown, also Y _s = 1.43% as a weighted average reflectance (scotopic vision), Y _p = 0.90% (photopic) is obtained Was. It has good antireflection properties as an antireflection film for a transparent substrate. The durability performance of this film was evaluated, and the results shown in Table 1 were obtained. It has been found that even if SiOx is used, the untreated surface methacrylic resin is insufficient in adhesion to the substrate. The evaluation items and evaluation method of the durability performance were performed using the following criteria.

a. Adhesion by cellophane tape peeling method. Store in a normal indoor atmosphere, and after one month and three months after film formation,
The inspection is performed on the corners, and the presence or absence of film peeling is visually observed. The data are expressed as fractions, with the denominator being 4 at the four corners and the numerator being the number of corners where no film detachment occurred.

b. Scratch resistance Use a cross cut peeling tester manufactured by Toyo Seiki Seisaku-sho, Ltd. Laminate two flannel cloths as a scratching medium, load 400g
After 50 reciprocations at / cm ² , the occurrence of flaws in the reciprocating direction is visually observed.

c. Severe test Save for 96 hours in an atmosphere of 50 ° C and 90% RH, take out, visually inspect and observe under a 40x microscope to check for abnormalities such as peeling, foaming and whitening of the film. The adhesiveness is examined at the center of both sides of the sample by a tape peeling method.

d.Chemical resistance After soaking ethanol in a cotton wool piece, slide the sample surface back and forth by hand 10 times, then peel off the film with a 10x loupe.
Observe for abnormalities such as whitening. Renew the absorbent cotton pieces and perform the same procedure for ethyl ether, acetone, and shiny (Kyowa Gas Chemical Industry Co., Ltd. OA filter cleaner).

Example 2 Same as Example 1 using a paragrass smoked color plate (methacrylic resin cast plate, with surface hardening treatment, plate thickness 2 mm, brand number TS-5KH, refractive index of surface hardened film n ₀ = 1.43) as a substrate Vacuum evaporation was performed on both surfaces of the substrate to form an antireflection film. In Example 1, TiO ₂ was used as the high refractive index substance.
In the second embodiment, ZrO ₂ is used and the refractive index of the film is approximately n ₂ = n ₄ = 1.95.
Met. The optical film thicknesses are respectively n ₁ d ₁ = λ / 4 × 20
%, N ₂ d ₂ = λ / 4 × 15%, n ₃ d ₃ = λ / 4 × 45%, n ₄ d ₄ = λ / 4
× 170%, n ₅ d ₅ = λ / 4 × 95%, and the other deposition conditions were the same as in Example 1. Evaluation results of the anti-reflective properties of the deposited products are as shown in FIG. 4 and Table 2, x = 0.173 as the interference color, it belongs to the blue range of _{y = 0.201, Y s = 0.64} %, Y p = 0.43 % Of the antireflection effect. As shown in Table 1, the evaluation results of the durability performance of this vapor-deposited product showed no problem in each evaluation item.

Example 3 Using the same substrate as in Example 2, vacuum deposition was performed on both surfaces of the substrate as in Examples 1 and 2 to form an antireflection film. However, TiO ₂ is used as a high refractive index material, and the refractive index of the film is almost
n ₂ = 2.00 and n ₄ = 2.05. The optical film thickness and other vapor deposition conditions were the same as in Example 1. A simulation diagram in this case is shown in FIG. Although the total light transmittance of this substrate was 50%, it was not uniform over the entire visible range, so the calculation was performed using the respective spectral transmittances at 13 wavelengths. In addition, SiOx, Ti
Since both O ₂ and SiO ₂ have refractive index dispersions that are too large to assume that the refractive index in the visible region is constant, the refractive indices at 13 wavelengths were used in consideration of this. FIG. 6 shows the results obtained by actual measurement, and the agreement with FIG. 5 was almost satisfactory. The plurality of curves shown in the above both figures show how the room changes over time for a long time after vapor deposition. While indicating some change with decreasing n ₁ of SiOx, interference color is remained in the range of as blue shown in Figure 1, the weighted average reflectance almost constant as shown in Table 3, or A film having the advantage of changing in the direction of decreasing the size, that is, the direction of improving the antireflection effect, was obtained. As shown in Table 1, the practical durability of this antireflection film was an excellent film having no problem at all.

[Effects of the Invention] As described above, according to the antireflection film of the present invention, a preferable reflection interference color of blue or blue-violet is stably provided (with respect to fluctuations in production and changes with time). It has an antireflection effect with a weighted average reflectance of 1.5% or less, and tends to be constant or lower over time, and has excellent practical durability performance. Suitable antireflection film can be provided.

[Brief description of the drawings]

FIG. 1 is a CIE chromaticity diagram used in the detailed description and examples of the present invention, FIG. 2 is a schematic diagram used in Example 1, FIG. 3 is a reflectance curve of Example 1, and FIG. FIG. 5 is a simulation diagram used in the third embodiment, FIG. 6 is a reflectance curve used in the third embodiment, and FIG. 7 is a flowchart used in the detailed description of the present invention. is there. In FIG. 1, a: chromaticity coordinate values of the vapor-deposited product of Example 1 b: chromaticity coordinate values of the vapor-deposited product of Example 2 c ₁ … chromaticity coordinate values of the vapor-deposited product of Example 3 immediately after vapor deposition c ₂ ...... example chromaticity coordinate values of the deposition 4 days at 3 c ₃ ...... example chromaticity coordinate values after deposition 26 days in 3 c ₄ ...... example chromaticity coordinate values after deposition 34 days in 3 c ₅ ...... Chromaticity coordinate value 72 days after vapor deposition in Example 3

Claims (2)

(57) [Claims] 1. An anti-reflection film comprising a five-layer thin film provided on the surface of a synthetic resin substrate having a refractive index in the range of 1.4 to 1.6, wherein the anti-reflection film extends from the substrate side to the air side. The first layer is made of a material having a refractive index in the range of 1.5 to 1.7, the second layer and the fourth layer are made of the same material having a refractive index in the range of 1.9 to 2.2, and the third and fifth layers are made of the same material. It is made of the same material having a refractive index in the range of 1.4 to 1.5, and the optical thicknesses n ₁ d ₁ , n ₂ d ₂ , n ₃ d ₃ , n ₄ d ₄ , n _{5 of} the first to fifth layers d ₅ is the following equations (1) to (5) anti-reflection film of plastic optical article, characterized in that Mitsurusu the scope of. 0.0625λ ≧ n ₁ d ₁ ≧ 0.0375λ (1) 0.0625λ ≧ n ₂ d ₂ ≧ 0.0375λ (2) 0.1125λ ≧ n ₃ d ₃ ≧ 0.0875λ (3) 0.450 λ ≧ n ₄ d ₄ ≧ 0.400 λ (4) 0.250 λ ≧ n ₅ d ₅ ≧ 0.225 λ (5) (λ is a design wavelength and 550 to 570 nm is used.) 2. The material of the first layer is SiOx (2>x> 1), the material of the second and fourth layers is TiO ₂ or ZrO ₂ , and the material of the third and fifth layers is _{2. The} antireflection film according to claim 1, wherein the antireflection film is SiO2.