JPH0434501A - Multilayered optical interference film - Google Patents

Abstract

PURPOSE:To provide the above film which has excellent heat resistance and weatherability and a long life and withstands severe use conditions by alternately laminating high-refractive index layers consisting of zinc sulfide and low- refractive index layers consisting of strontium fluoride on a substrate surface. CONSTITUTION:This interference film is constituted by alternately laminating total 25 layers of the high-refractive index layers 2H consisting of the zinc sulfide and the low-refractive index layers 2L consisting of the strontium fluoride from a reflecting part 11 side on the inside surface of the reflecting part 11 constituting the substrate. The optical film thicknesses of the respective layers are 1/4lambda. The film constitution of the alternate layers is controlled to lambda=600nm from the 1st layer up to the 13th layer. Further the films from the 14th layer thereon up to the 25th layer are controlled to lambda=450nm. The strontium fluoride is chemically stable, is highly resistant to heat and weather and is well adaptable to the lamination with the zinc sulfide. The multilayered films which are highly resistant to the heat and weather and are hardly peelable are obtd. in this way.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to a multilayer reflector of a floodlight or an exposure light source, in which thin films of various thicknesses are stacked in multiple layers. The present invention relates to a multilayer optical interference film that has a specific spectral transmittance by utilizing the interference of reflected light from each surface, and particularly relates to a multilayer optical interference film that has improved heat resistance and weather resistance.

(Prior art) Conventionally, a halogen light bulb with a reflector is one in which a visible light reflecting and infrared transmitting film is formed on the inner surface of a hard glass reflector, and a halogen light bulb is mounted inside the reflector. Of the light, visible light is projected forward by being reflected by the visible light-reflecting, infrared-transmitting film, and infrared light is directed backward by passing through the visible-light-reflecting, infrared-transmitting film. For this reason, this halogen light bulb with a reflector emits visible light with little infrared rays, that is, so-called cold light, and is often used as a light source for, for example, floodlights, store lighting, or medical lighting.

Therefore, the visible light reflective infrared transmitting film has a high refractive index layer made of zinc sulfide (ZnS) or the like and a low refractive index layer made of magnesium fluoride (MgF2), silica (S i 02 ), etc. on the reflective mirror surface. For example, it is made by laminating 15 to 25 layers alternately, and reflects visible light through optical interference.
It transmits infrared rays.

In addition, halogen light bulbs are used as light sources for exposure in electronic copiers, facsimile machines, etc., with a filament arranged along the center line of a quartz tube-shaped bulb and a visible light-transmissive infrared reflective film formed on the outer surface of the bulb. ing. This type of halogen light bulb emits visible light to the outside world by passing through a visible light-transmitting infrared reflective film, and infrared light is reflected by a visible light-transmitting infrared reflective film to the filament. The light is returned and heated to improve luminous efficiency. Therefore, halogen light bulbs have the advantage of emitting visible light with little infrared rays, that is, so-called cold light, and having high luminous efficiency.

However, the visible light transmitting infrared reflective film of the lever is similar to the visible light reflective infrared transmitting film described above, and the zinc sulfide (zinc sulfide)
It is made by laminating, for example, 15 to 25 layers of high refractive index layers made of ZnS, etc. and low refractive index layers made of magnesium fluoride (MgF2), silica (S i 02 ), etc., and is visible. A light-reflecting, infrared-transmitting film is a film that transmits visible light and reflects infrared rays by changing the thickness of the layer.

In this way, the visible light reflective infrared transmitting film and the visible light transmitting infrared reflective film are made of the same material, but by simply changing the thickness of the layers, they can be applied to a specific wavelength range using light interference. , and reflects light in other specific wavelength ranges, and such visible light-reflecting, infrared-transmitting films and visible-light-transmitting, infrared-reflecting films are collectively referred to as multilayer optical interference films.

(Problem to be solved by the invention) However, the above-mentioned Z n S M g F 2
A halogen lamp with a reflector coated with an alternating layer interference film or a ZnSSiO2 alternating layer interference film has a problem in that it is likely to peel off due to the heat load during lamp lighting or a high temperature and humid atmosphere. That is, when the ZnS-MgF2 alternating layer interference film is applied to a light source that generates high heat, such as a halogen light bulb, it will peel off in a short time due to the high temperature, and the 2nS in the surface layer will be oxidized and become cloudy. usually,
When a halogen bulb is turned on, the heat load on the reflector is 350
It becomes unusable after 30 hours at 300°C and 100 hours at 300°C. In addition, the ZnS-MgF2 alternating layer interference film is hygroscopic, so if it is left in an atmosphere with a temperature of 50°C and a humidity of 90% for 20 hours, the film will peel off. Ya ZnS S
Table 1 shows the heat resistance and weather resistance of the iO2 alternating layer interference film, which were evaluated based on the time until the optical interference film peeled off.

As is clear from Table 1, Z n S −M g F
The type 2 optical interference film has good weather resistance but poor heat resistance, so it is suitable for halogen light bulbs with a relatively low heat load and long life. Furthermore, the Z n S Si O 2 -based optical interference film has good heat resistance but poor weather resistance, so it is suitable for a light source with a high heat load and a short life, such as a high output and short life halogen light bulb.

In this way, optical interference films and their film configurations have been selected and used depending on the application, but in recent years, there has been a demand for higher output, higher efficiency, and longer life for halogen light bulbs and halogen light bulbs with reflectors. There is now a need for multilayer optical interference films that simultaneously have high levels of heat resistance and weather resistance.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a multilayer optical interference film having excellent heat resistance and weather resistance.

Table 1 [Structure of the Invention] (Means and Effects for Solving the Problems) In order to achieve the above object, the present invention provides a high refractive index layer made of zinc sulfide and a low refractive index layer made of strontium fluoride on the substrate surface. Strontium fluoride is chemically stable, has excellent heat resistance and weather resistance, and has good lamination compatibility with zinc sulfide. As a result, a multilayer film that has excellent heat resistance and weather resistance and is difficult to peel off can be obtained.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a halogen light bulb with a reflective mirror to which the multilayer optical interference film of the present invention is applied, and FIG. 2 is a schematic enlarged sectional view of one embodiment of the multilayer optical interference film of the invention.

As shown in Fig. 1, a hard glass reflector 1 serves as a base.
is a paraboloid of revolution with four reflective parts L1 expanded on one side.
A visible light reflecting infrared transmitting film 2, which is an example of a multilayer light interference film, is formed on the inner surface of the reflecting mirror 1, that is, on the inner surface of the reflecting portion 11.
is covered. A halogen light bulb 3 serving as a light source is attached to the center of the reflecting portion 11, and the halogen light bulb 3 is fixed to the reflecting mirror 1 with a heat-resistant adhesive 4. This reflector
A front glass 5 is attached to the front of the vehicle for safety.

The halogen light bulb 3 has a cylindrical shape (
T type) The base of the bulb 31 is crushed to form a sealing part 32, and the filament 33 is sealed inside the bulb 31. 33 is positioned at the focal point of the concave portion of the reflecting portion 11, and the base portion 12 is filled with the adhesive 4 to close the sealing portion 32.
Glue and fix.

In addition, as shown schematically and enlarged in FIG. 2, the visible light reflective infrared transmitting film 2 has a high refractive index film made of zinc sulfide (ZnS) formed on the inner surface of the reflective part 11 forming the base body from the reflective part 11 side. The layer 211 (hatched downward to the right) and the low refractive index layer 2L (hatched upward to the right) made of strontium fluoride (S r F 2 ) are alternately stacked for a total of 25 layers, and the optical thickness of each layer is 1. /4λ. As shown in Table 2, the film structure of the alternate layers is controlled by λ1-13-60001 from the first layer to the 13th layer. That is, the high refractive index layer 2H of λ-600ns and the λ-600na
six low refractive index layers 2L each are laminated alternately,
Furthermore, one high refractive index layer 2H of λ-600 ns is added thereon, making 13 layers. Furthermore, the thickness of the 14th to 25th layers above it is controlled to λ -450 nm. That is, the low refractive index layer 2L of λ-450 nm and the λ-
Six 450 nm high refractive index layers 2H are alternately laminated.

(The following is a blank space) Table 2 λB - 600 nm, λb - 450 na To form such a visible light reflective infrared transmitting film 2, a vacuum evaporation method is generally used. Typical deposition conditions are as follows.

(1) Degree of vacuum: 8XlO-3 to lXl0-4 To
rr (2) Scattering gas: Argon gas (3) Substrate temperature = 100 to 300°C (4) Evaporation source: ZnS...Resistance heating S r F 2
...Electron beam ZnS is heated and evaporated by resistance heating, and the boat used for resistance heating is made of tungsten, and the current value when energized is, for example, 290A. On the other hand, S r F 2 is heated and evaporated by an electron beam from an electron gun with an accelerating voltage of 6 KV, but the emission current value at this time is, for example, 6 KV.
It is 0mA.

When the halogen bulb with a reflector, which has the visible light reflective infrared transmitting film 2 coated on the reflective part II, is turned on, the filament 3
Of the light emitted from 3, the visible light is reflected by the visible light reflecting infrared transmitting film 2 and goes forward, and the infrared light is transmitted through the visible light reflecting infrared transmitting film 2 and is reflected by the glass substrate of the base of the reflecting part 11. It passes through and is emitted backwards.

Therefore, this halogen light bulb with a reflector emits visible light with little infrared rays, that is, so-called cold light, in the forward direction, so it is praised as a light source that does not pose the risk of heating and damaging the irradiated object.

The heat resistance and weather resistance of the visible light reflective and infrared transmitting film 2 of the reflective mirror 1 thus obtained were evaluated. This evaluation is shown in Table 3. Here, the heat resistance is expressed as the time until peeling starts at 300°C and 350°C, which are the temperatures of the reflective part 11 when the halogen bulb 3 is turned on, and the weather resistance is expressed as the time until peeling starts at a temperature of 50°C.
, expressed as the time until the start of peeling in an atmosphere with a humidity of 90%.

Comparing Table 3 with Table 1, it is clear that the products of this example have excellent heat resistance and weather resistance, have a long life, and can withstand harsh usage conditions.

This is because S r F 2 constituting the visible light reflective infrared transmitting film 2 of this example is chemically stable and has excellent heat resistance and weather resistance, and the lamination of S r F 2 and ZnS has good compatibility. For this reason, it is possible to obtain a film that has excellent heat resistance and weather resistance and is difficult to peel off.

Next, another embodiment in which the present invention is applied to a tubular halogen light bulb used for exposure in copying machines and the like will be described with reference to FIG.

As shown in FIG. 3, this tubular halogen bulb has a filament 7 sealed along the center line of a quartz bulb 6,
A visible light transmitting and infrared reflecting film 8 is formed on the outer surface of the bulb 6, and the bulb B is further filled with necessary halogen along with argon.

The visible light transmitting infrared reflecting film 8, like the visible light transmitting infrared transmitting film 2 shown in FIG. r F 2 ) and low refractive index layers 2L (hatched upward to the right), for example, a total of 15 layers are alternately laminated, and the optical film thickness of each layer 211.2L is different from that of the visible light reflective infrared transmitting film 2. This gives it the property of transmitting visible light and reflecting infrared rays.

When this halogen bulb is turned on, visible light out of the light emitted from the filament 7 is reflected by the visible light transmitting infrared reflective film 8.
On the other hand, the infrared rays are reflected by the visible light transmitting infrared reflective film 8 and returned to the filament 7, thereby heating the filament 7 and improving the luminous efficiency.

Therefore, this halogen bulb is highly efficient and emits so-called cold light with little infrared radiation.

Furthermore, since the visible light-transmitting infrared reflective film 8 is formed in the same manner as the visible light-reflecting infrared transmitting film 2 described above, it has excellent heat resistance and weather resistance, has a long life, and can withstand harsh usage conditions.

As mentioned above, by using strontium fluoride as a material constituting the multilayer optical interference film, strontium fluoride is chemically stable and has excellent heat resistance and weather resistance. Since the compatibility is good, it is possible to obtain a multilayer optical interference film that is difficult to peel off and has excellent heat resistance and weather resistance.

In addition, in the above embodiment, an example was explained in which the multilayer light interference film is applied to a visible light reflective infrared transmitting film or a visible light transmitting infrared reflective film, but the application is not limited to this, and can be applied to, for example, a color filter film, an ultraviolet blocking film, etc. You may.

Further, in the above embodiments, the method for forming the multilayer optical interference film was the vacuum evaporation method.
Other forming methods such as apor deposition method may also be used.

Further, in the above embodiments, a hard glass reflector and a tube quartz bulb are used as the base, but the base body is not limited to this.
For example, any material suitable for the purpose, such as a filter substrate, may be used, and its shape and material may be selected as appropriate.

Further, at least one of the zinc sulfide layer and the strontium fluoride layer may contain a glassy reinforcing agent, light-diffusing fine particles, or the like as appropriate.

Furthermore, it goes without saying that the present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist of the present invention.

(The following is a blank space) Table 3 [Effects of the invention] As detailed above, according to the multilayer optical interference film of the present invention,
By alternately laminating high refractive index layers made of zinc sulfide and low refractive index layers made of strontium fluoride on the substrate surface, each component is chemically stable and has good compatibility during lamination, making it heat resistant. It has excellent durability and weather resistance, and can withstand harsh usage conditions with a long life.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a halogen light bulb with a reflector to which the multilayer optical interference film of the present invention is applied, and FIG. 2 is an enlarged sectional view of a model of an embodiment of the multilayer optical interference film of the invention. FIG. 3 is a sectional view of another application example. 1...Reflecting mirror (substrate), 2...Visible light reflecting infrared transmitting film (multilayer optical interference film), 2...
H...High refractive index layer, 2L...Low refractive index layer,... Bulb (substrate),... Visible light transmitting infrared reflecting film (multilayer optical interference film).

Claims (1)

[Claims] A multilayer optical interference film comprising a multilayer film in which a high refractive index layer made of zinc sulfide and a low refractive index layer made of strontium fluoride are alternately laminated on a substrate surface.