JPH02149803A - Multilayered optical film - Google Patents

Abstract

PURPOSE:To relatively easily display pictures, characters, marks, etc., by providing parts formed to the film thickness deviating from an optical film thickness of 1/4 wavelength on thin films. CONSTITUTION:At least one layer of the thin films of the multilayered optical films consisting of >=2 layers alternately laminated with the high-refractive index thin film 11, 13 having the optical film thickness of lambda0/4 the wavelength (lambda0) of the light desired to be reflected and the low-refractive index thin films 12, 14 in this order have the display parts for the pictures, characters, etc., formed to the optical film thickness deviated from the optical film thickness of lambda0/4. The rays having a center at the wavelength lambda0 are effectively reflected by the high-refractive index thin films having the optical film thickness of lambda0/4 and the low-refractive index thin films and the visible rays are almost transmitted through the transparent substrate having such multilayered optical films if such substrate is irradiated with light. However, the display parts of the pictures, characters, etc., provided on at least one layer of the high-refractive index thin films or the low-refractive index thin films are formed to the optical film thickness deviated from lambda0/4 optical film thickness and, therefore, the rays having a center at a certain wavelength lambda1 among the visible rays are partly reflected and the pictures, characters, etc., in the display parts are displayed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical multilayer film that utilizes optical interference.

[Prior Art] Recent advances in thin film formation technology have led to optical multilayer i! J.I.
l! Research on multilayer films such as these is actively being conducted.

For example, dichroic filters, cold mirrors, hot mirrors, and the like use optical multilayer films that increase or prevent reflection.

As this optical multilayer film, in order to selectively reflect light of a desired wavelength (λ0), a thin film of a high refractive index material and a thin film of a low refractive index material are alternately formed on a glass substrate with an optical film thickness of λo/4. Multilayer films that utilize the interference effect of light are known. Here, the optical thickness refers to (refractive index of a thin film) X (thickness of a thin film) (the same shall apply hereinafter). For example, when it is desired to effectively reflect a certain wavelength (λ0) of infrared rays, by setting the optical thickness of each layer to λo/4, the infrared rays can be effectively reflected. The optical multilayer film that can effectively reflect infrared rays in this manner is hereinafter referred to as a heat ray film.

By the way, when an optical multilayer film is used for automobile window glass, etc., it must effectively reflect only infrared rays and transmit most of visible rays. However, it is known that the visible light reflectance of the heat ray reflective glass coated with the above-mentioned heat ray reflective film is about twice the visible light reflectance of ordinary glass.

Conventionally, as a means to prevent such reflection of visible light, a high refractive index material of a high refractive index material, in which the optical thickness of each layer is λ0/4 (when the wavelength to be reflected is λ0, which is a certain wavelength of infrared rays), has been used. The film and a low refractive thin film of a low refractive index material are stacked in odd numbers on a glass substrate in the order of high refractive thin film, low refractive thin film, and high refractive thin film, and the outermost layer is further coated with a low optical film thickness of λo/8. It is known that a refractive thin film is formed.

According to this, the visible light reflectance can be reduced to the same level as that of plain glass or even lower.

In addition, in order to prevent the occurrence of a purple reflective color due to the optical thickness of the outermost layer of λo/8, the inventor has determined that the optical thickness of at least one low refractive index film is 1. .0
The proposal is to set the value to 6λo/4 or more and 1.09λo/4 or less (Utility Application No. 6395618).

[Problems to be Solved by the Invention] The above-mentioned heat ray reflective film is also used in automobile window glasses and the like because it effectively reflects only infrared rays and transmits most of visible rays. On the other hand, in recent years, various pictures, characters, marks, etc. are increasingly displayed on the window glass of automobiles. These displays are usually made by pasting stickers with characters printed on them or by baking ceramic onto the window glass.

However, displaying characters or the like on the window glass of a car using stickers or ceramics obstructs the view, and therefore the positions where they can be placed are naturally restricted and there is little freedom. In addition, when forming letters etc. by baking ceramics,
This increases the manufacturing process and manufacturing time, causing problems in terms of cost.

The present invention has been devised in view of the above-mentioned circumstances, and the technical problem to be solved is an optical system having a display part for pictures, characters, etc., which can be manufactured at low cost and without any restrictions on the installation position. The goal is to create multilayer films.

[Means for solving the yI problem] The optical multilayer film of the present invention is a high refractive index film made of a high refractive index material on a transparent substrate and having an optical film thickness of λ0/4 of the wavelength (λ0) of the light to be reflected. ＠film, an optical multilayer film consisting of two or more layers alternately laminated in the order of low refractive index thin films made of a low refractive index material and having an optical thickness of λ0/4 of the wavelength (λ0) of the light to be reflected; The at least one layer of the high refractive index thin film or the low refractive index thin film is characterized in that it has a display portion for pictures, letters, etc. formed with an optical thickness that deviates from λo/4 optical thickness.

The transparent substrate on which the optical multilayer film of the present invention is V4 layered can be made of glass, transparent plastics, or the like.

The optical multilayer film of the present invention includes a high refractive index thin film made of a high refractive index substance, and a low refractive index 1iIFl made of a low refractive index substance.
It is composed of a multilayer film of two or more layers stacked alternately. Note that in order to further enhance the interference effect, it is preferable to use a multilayer film of four or more layers.

The high refractive index thin film is formed of a high refractive index material and has an optical thickness of λo/4 of the wavelength (λ0) of the light to be reflected. Since λo/4 here is a physical value, it is not exact, and it is more preferable that it be closer to λ0/4. The same applies to the optical thickness of the low refractive index thin film described later.

Examples of high refractive index substances include titanium dioxide (TiO
x>, zirconium Mide (Zr02), etc. can be used.

The low refractive index thin film is formed of a low refractive index material and has an optical thickness of λo/4 of the wavelength (λ0) of the light to be reflected. As the low refractive index substance, for example, silicon dioxide (SiOz), magnesium fluoride (MQF2), etc. can be used.

At least one layer of the high refractive index SS or the low refractive index thin film partially has display portions such as pictures and characters that characterize the present invention. This display portion is formed to have an optical thickness that deviates from the λo/4 optical thickness, and may be provided on either a high refractive index thin film or a low refractive index thin film. Note that in terms of manufacturing, it is easier to provide the first layer from the transparent substrate. For example, it can be formed by attaching a mask member in the shape of a desired picture, character, etc. at the time of forming the S film and changing the II* thickness of the display portion. Further, the optical thickness of the display portion can be set in accordance with the wavelength λ1 of the color desired to be expressed in the display portion (the color reflected by the display portion).

High refractive index thin films and low refractive index thin films can be produced using physical thin film forming methods such as vacuum evaporation, sputtering, and ion blating, and chemical thin film forming methods such as chemical vapor deposition and plasma CVD. The film can be formed by

[Effect] The optical quantity of Honhatsuro! ! ! Fi! When light is applied to a transparent substrate having a wavelength of Transparent. However, the display portion of pictures, characters, etc. provided on at least one layer of the high refractive index thin film or the low refractive index thin film is λ0/4
Optical I! Since it is formed to have an optical thickness that deviates from the optical thickness, it reflects a portion of the visible light rays centered around a certain wavelength λ1. Pictures, characters, etc. on the display portion are displayed by colored reflected light reflected from the display portion. Note that the hue of the colored reflected light reflected from the display portion also changes depending on its reflection angle (viewing angle).

[Example] Hereinafter, this will be explained in detail using examples.

(First Example) FIG. 1 is a schematic cross-sectional view of an automobile window glass in which the optical multilayer film 1 of this example is laminated on the surface of a blue glass substrate 2. This optical multilayer P/A1 consists of a basic component part 11a and a display part 11b in order from the surface of the blue glass substrate 2.
High refractive index thin vj! 11. It is a multilayer film consisting of four layers in which a first low refractive index thin film 12, a second high refractive index thin film 13, and a second low refractive index S film 14 are laminated. As a high refractive index material, 2
．． Titanium dioxide (-ri) with a refractive index (nH) of 50
ot), as a low refractive index material, a refractive index of 1.45 (nL
) was used.

These thin films were formed to the respective thicknesses using the ion blating method under the film forming conditions shown below. In addition,
In this example, the design wavelength λG of the light to be reflected is 1105
It was set to 0n.

First, when forming the first high refractive index thin film 111, the optical quantity of the blue glass substrate 2 is 1III! A mask material was formed by printing, for example, characters such as rABCJ by screen printing at a desired position on the side where the I film was formed, and the mask material was subjected to a baking process. This blue glass substrate 2 was placed in a vacuum chamber, and after the vacuum chamber was evacuated to 5×10-3 Pa, oxygen was introduced.
The degree of vacuum was set to X10-2 Pa. Then, a high frequency power of 300 W was applied to generate oxygen plasma, and a bias of 500 μ was applied to the acceleration electrode. Next, the evaporation material TtOt was heated with an electron beam to form a film at a rate of 0.2r1 m/sec. Then, a 55 nm film was deposited on the blue glass substrate 2.
The film formation was stopped once a Ti01til film was formed, and
After removing the mask material, 50 nm of Ti was applied again under the same conditions.
A 1t thin film was formed. As a result, the display part 11b (the part where characters are formed with the mask material) with a film thickness of 5 Qnm and the display part 11b with a film thickness of 1
A first high refractive index thin film 11 consisting of a basic constituent portion 11a (other portions) having a thickness of 0'5 nm was formed.

Next, an evaporation material is applied to the surface of the first high refractive index thin film 11.
O2, and the other film forming conditions were the same as in the case of the first high refractive index film 11, and the film J! ii. A first low refractive index thin film 12 of 195 nm was formed. Furthermore, in the same manner, a second high refractive index layer made of TiO2 with a thickness of 1105 nm is formed on the surface of the first low refractive index film 12. S on the surfaces of the iJ film 13 and the 28th refractive index film 13.
A second low refractive index thin film 14 made of ioz and having a thickness of 97.5 nm was formed.

As a result, the thickness of the entire portion of the optical multilayer film 1 including the display portion 11b is 5 onm (T +02) + 195 nm.
(SiOz)+105nm (105n>+97.5nm
(SiOz) = 447.5 nm, and the film thickness of the entire portion including the other basic component portion 11a is 105 nm (T
105n+195nm(SiOz)+105nm(T1
05n+97°5nm (S i Of >=502.
It becomes 5 nm.

Note that the second low refractive index i11! The reason why the optical film thickness of the outermost If layer 14 is set to λo/8 is to reduce the visible light reflectance, and when it is not necessary, the outermost low refractive index thin film is not necessary.

Further, the film thickness of the first low refractive index thin film 12 is set to 1.08λo/4.
This is because the optical thickness of the second low refractive index "a film (outermost layer) 14 is set to λo/8, so that the basic component 11
This is to prevent reflection colors such as purple from occurring in a.

As described above, the automobile window glass in which the optical multilayer film 1 of this embodiment is formed on the blue glass substrate 2 has the basic structure 11.
The reflected color of the portion a is almost colorless, which is the same as that of the blue glass substrate 2, and the reflected color of the display portion 11b is, for example, bluish-purple when the reflection angle (viewing angle) is 5°. Due to this difference in reflected color, the characters rABCJ in the display portion 11b are displayed.

(Second to Fourth Examples) As a second example, as shown in the table, the display portion 11 of the first high refractive index film 11 of the optical multilayer film of the first example is
The optical multilayer films of the second to fourth examples, in which only the film thickness of -b was changed, were formed on a blue glass substrate in the same manner as in the first example. The optical multilayer films of the second to fourth embodiments were formed so that the thickness of the display portion was 10 nm, 30 nm, and 190 nm, respectively.

(Test) The automobile window glasses having the optical multilayer films of Examples 1 to 4 above were illuminated with standard light source C adopted by the International Commission on Illumination as an illumination light source, and The xy chromaticity coordinate values of the color of the reflected light were measured when the angle (with respect to the normal line) was 5°. The results are shown in the table, and FIG. 2 shows the xy chromaticity diagram of the blue glass substrate (x mark) and the basic component part (○ mark), and FIG. 3 shows the xy chromaticity diagram of the display part (φ mark). Here, the chromaticity coordinate value is a value that indicates chromaticity in the C■E display system determined by the International Commission on Illumination, and is
In the case of Z system, the tristimulus values are XSY, Zl or X+Y+Z
=S means x=X/S, V=Y/S, and z=Z/S. The xy chromaticity diagram is a diagram that displays the above-mentioned chromaticity coordinates, and refers to one in which Xs"p' of the three color coefficients is expressed in an orthogonal coordinate system. The curves shown are isohue lines, purple (P), blue color (PB)
), blue (B), blue-green (BG), green (G), yellow-green (YG), yellow (Y), yellow-red (YR), red (R
), indicating a reddish-purple color (RP).

As shown in the table and FIG.
The display portion of the second example had a yellow-red color, the display portion of the third example had a purple color, and the display portion of the fourth example had a yellow-green reflection hue.

In addition, for the automobile window glasses according to the first and fourth embodiments, reflected light when the incident angle (the angle between the incident light beam and the normal line of the glass) is shifted from 5'' to 30'' to 45° to 60°. The xy chromaticity coordinate values were measured for the color. The results are shown in the xy chromaticity diagram of FIG. In the figure, the ○ marks are the xy chromaticity coordinates j for the basic components of the first and fourth embodiments.
IA (Il'I), the Δ mark indicates the xy chromaticity coordinate value for the display part of the first embodiment, and the * mark indicates the xy chromaticity coordinate value for the display part of the fourth embodiment. In each case, the xy coordinate values are smaller in the order of the arrows when the incident angle is changed from 56.30° to 45° to 609.

As is clear from FIG. 4, in the case of the basic component, although the hue changes, the saturation is small and it is almost colorless at all angles. On the other hand, in the case of the display part of the W11 embodiment, the color changes from blue-violet to purple in the range of 5° to 300°, becomes almost colorless at 45°, and becomes yellow-green at 60°. In addition, in the case of the display part of the fourth embodiment, 5° ~
In the range of 30 degrees, the color is yellow-green, in the range of 45 degrees, it is red, and in the range of 60 degrees, it is a color close to iI color. In other words, the basic component part is almost colorless and does not change, but the display part has a reflection angle (
The reflected color changes depending on the viewing angle).

As described above, the optical multilayer films of the first to fourth embodiments are capable of displaying characters and the like based on the reflected color of the display portion.

Therefore, the visible light transmittance of the display portion can be set to 70% or more as defined by the JIS standard, and there is no fear that the view will be obstructed.

Therefore, it can be provided in a position where it would obstruct the view, which could not be displayed conventionally, and the degree of freedom can be expanded.

Then, in the process of forming an optical multilayer film, a first high refractive index book r is formed.
Since a reflection angle can be generated only by partially shifting the optical thickness of fA11, display parts such as pictures, characters, marks, etc. can be formed relatively easily. Furthermore, by changing the optical film thickness of one display portion, it is possible to produce various hues.

Furthermore, since characters and the like are displayed using reflective colors, the display area has a glossy appearance and is excellent in design.

Furthermore, since the reflected color of display parts such as characters changes depending on the reflection angle (viewing angle), an interesting effect can be created in terms of design.

[Effect of the invention 1] The optical multilayer film of the present invention has pictures, letters, etc. formed on at least one high refractive index thin film or low refractive index thin film to an optical film thickness that deviates from an optical film thickness of λo/4. It has a display part. Therefore, pictures, characters, etc. can be displayed by reflecting part of the visible light at the display portion, so there is no restriction on the position where the display portion is provided. Therefore, the degree of freedom in the placement position can be increased compared to the conventional art. Further, since the display portion can be formed by simply shifting the optical film Jq during the film formation process of the optical multilayer film, it can be produced relatively easily and at low cost.

[Brief explanation of the drawing]

1 to 4 relate to embodiments of the present invention, and FIG.
A schematic cross-sectional view of an automobile window glass in which the optical multilayer film of the example is laminated on a helmet glass substrate-1-, FIG. 2 is an xy chromaticity diagram of the blue glass substrate and its basic constituent parts, and FIG. 4. An xy chromaticity diagram of the display portion of the fourth embodiment. FIG. 4 is an xy chromaticity diagram of reflected light when the angle of incidence is shifted in the basic components and display portion of the first and fourth embodiments. . 1... Optical multilayer film 2... Portable glass substrate (transparent substrate) 11... First high refractive index thin film 12... First low refractive index thin film 13... Second high refractive index thin film 14. ...Second low refractive index thin film Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] (1) A high refractive index thin film with an optical thickness of λ_0/4 of the wavelength of the light to be reflected (λ_0) made of a high refractive index material on a transparent substrate;
An optical multilayer film of two or more layers alternately laminated in the order of low refractive index thin films having an optical thickness of λ_0/4 of λ_0), at least one layer of the high refractive index thin film or the low refractive index thin film. is an optical multilayer film characterized by having a display portion for pictures, characters, etc. formed to an optical film thickness that deviates from an optical film thickness of λ_0/4.