WO2020137195A1 - Dielectric multilayer film, production method therefor and image display device equipped with same - Google Patents

Abstract

The objective of the present invention is to provide a dielectric multilayer film that is formed on a resin substrate and that balances shape change suppression, crack prevention, optical characteristics (oblique incidence characteristics) and producibility of the dielectric multilayer film, and to provide a production method therefor and an image display device equipped with the same.　This dielectric multilayer film comprises at least one layer of a low refractive index layer and a plurality of high refractive index layers on a resin substrate, and is characterized in that the total film thickness of the dielectric multilayer film is 2 μm or thicker, the refractive indices for the plurality of high refractive index layers for a light wavelength of 550 nm are 1.9 or greater and are different from one another, an alternately layered part wherein the plurality of high refractive index layers have been layered alternately is provided, and the low refractive index layers, having a refractive index of less than 1.9 for a light wavelength of 550 nm, are disposed between the alternately layered parts.

Description

Dielectric multilayer film, method of manufacturing the same, and image display device having the same

The present invention relates to a dielectric multilayer film, a method for manufacturing the same, and an image display device equipped with the same. More specifically, the present invention relates to a dielectric multilayer film formed on a resin substrate, which has suppression of shape change of the dielectric multilayer film, crack prevention, optical characteristics (oblique incidence characteristics), and productivity.

When forming a dielectric multilayer film on a resin substrate, thermal deformation and cracks due to the difference in linear expansion become major problems. During film formation, the temperature rises due to the radiant heat from the vapor deposition source and the kinetic energy of vapor deposition molecules, so when returning to room temperature due to leakage, the shape changes due to stress (thermal stress) due to the difference in linear expansion between the substrate and the film. Since the thermal stress of the film at this time acts in the compression direction, if the stress of the film itself (intrinsic stress) is oriented in the tensile direction, it cannot withstand the stress difference at the interface and cracks occur in the dielectric multilayer film. In order to suppress cracks, the intrinsic stress of the dielectric multilayer film may be set in the compression direction, but since the stress of the vapor deposition material (especially high refractive index material) is in the tensile direction, the ion assisted deposition (Ion Assisted Deposition, hereinafter, simply Also referred to as "IAD"), stress adjustment is required.

Patent Document 1, the high refractive index layer (TiO ₂₎ and the low-refractive index layer and method of forming the alternate multilayer film of (SiO ₂₎ is disclosed, IAD the TiO ₂ film formation, the SiO ₂ normal Technology that offsets internal stress of laminated multilayer film by alternately laminating compressive stress film and tensile stress film by forming by vapor deposition to improve adhesion between film and substrate and suppress crack generation Is disclosed.

However, since a large amount of contradictory stress is applied to the interface between the TiO ₂ layer and the SiO ₂ layer, the interface is vulnerable to a stress environment and, for example, the generation of cracks cannot be suppressed in a high temperature environment or a high temperature and high humidity environment.

Also, in order to satisfy the desired optical characteristics, a thick film of 2 μm or more is required, so the film formation time is long, and if the power during IAD is increased, the resin substrate may reach the deflection temperature under load due to radiant heat.

In addition, SiO ₂ (low-refractive index material), whose stress can be adjusted at a relatively low temperature, has high sensitivity to variations in the incident angle of light on the dielectric multilayer film, so that optical characteristics such as blue shift occur (oblique light incident characteristics). There is a problem that is inferior. The blue shift means that the wavelength of the spectrum line shifts to the short wavelength side due to a certain cause, which causes fluctuations in light reflectance and light transmittance, which causes poor visibility.

Furthermore, even if cracks can be suppressed, there is also the problem that the power during IAD cannot be increased too much because the shape change will be large if the intrinsic stress is large. For this reason, if the interlayer interval is considerably lengthened to suppress thermal stress (for example, if each layer is left for 12 hours), the productivity is remarkably poor.

The method described in Non-Patent Document 1 can be referred to for measuring the stress of each layer of the multilayer film.

In Patent Document 2, in an optical element in which a multilayer film is formed on one surface of a substrate and a single layer film in the same stress direction is formed on the opposite surface, a single layer film having a stress in the same direction as the stress of the multilayer film is formed. A technique is disclosed in which the warpage due to the stress of the multilayer film and the warpage due to the stress of the single layer film are offset, and as a result, the warpage of the substrate is relaxed and reduced. However, since thin films are formed on both sides of the substrate, the production process is complicated and the productivity is poor.

In Patent Document 3, a high-refractive-index layer (TiO ₂ or LaTiO ₃ ) and a low-refractive-index layer (SiO ₂ ) are formed under a specific pressure to compress the high-refractive-index layer and the low-refractive-index layer. Therefore, when the resin base material expands due to heat, the dielectric multilayer film expands while releasing the compressive stress of each layer. Therefore, the optical multi-layer film expands while sufficiently following the substrate, so that cracks are less likely to occur in the dielectric multi-layer film.

However, since the film forming pressure is changed for each layer, the production process is complicated and the productivity is poor. Further, as described above, since SiO ₂ (low refractive index material) has high sensitivity to variations in the incident angle of light on the dielectric multilayer film, there is a problem that the optical characteristics are inferior such as the occurrence of blue shift.

Therefore, it is possible to form a dielectric multilayer film on a resin substrate that has both thermal stress, suppression of shape change of the dielectric multilayer film due to compression and tensile stress, crack prevention, optical characteristics (oblique light incidence characteristics) and productivity. Technology is desired.

JP, 2007-63574, A JP, 2006-308721, A JP 2006-251760 A

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to suppress the shape change of the dielectric multilayer film, prevent cracks, combine optical characteristics (oblique light incidence characteristics) and productivity, and resin. A dielectric multilayer film formed on a substrate, a method for manufacturing the same, and an image display device including the same.

In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, a dielectric multilayer film in which at least one low refractive index layer and a plurality of high refractive index layers are formed on a resin substrate. There, a high refractive index layer having a specific refractive index is alternately laminated to form an alternating laminated portion, and the low refractive index layer is arranged between the alternating laminated portions by a dielectric multilayer film. , A dielectric multi-layer film formed on a resin substrate, which has suppression of shape change of the dielectric multi-layer film, crack prevention, optical characteristics (oblique light incidence characteristics) and productivity, its manufacturing method and image display including the same It has been found that a device is obtained.

That is, the above problems according to the present invention are solved by the following means.

1. A dielectric multilayer film comprising at least one low refractive index layer and a plurality of high refractive index layers on a resin substrate,
The total thickness of the dielectric multilayer film is 2 μm or more,
The plurality of high refractive index layers have different refractive indices at a light wavelength of 550 nm of 1.9 or more, and have a plurality of high refractive index layers alternately laminated, and
A dielectric multilayer film, wherein the low refractive index layer having a refractive index of less than 1.9 at a light wavelength of 550 nm is arranged between the alternating laminated portions.

2. 2. The dielectric multilayer film according to item 1, wherein the layer thickness of each of the alternating laminated portions is 1.5 μm or less.

3. The difference in refractive index between the plurality of high refractive index layers is 0.2 or more, and the materials contained in the plurality of high refractive index layers may be the same or different. The dielectric multilayer film according to the item.

4. The dielectric multilayer film according to any one of items 1 to 3, wherein the dielectric multilayer film has an average refractive index at a light wavelength of 550 nm of 1.95 or more.

5. 5. The dielectric multilayer film according to any one of items 1 to 4, wherein the layer thickness of the low refractive index layer is 8 nm or more.

6. 6. The stress per unit layer thickness of the low refractive index layer and the high refractive index layer is in the range of 0 to 500 MPa in the compression direction, according to any one of the items 1 to 5. Dielectric multilayer film.

7. The material contained in the high refractive index layer is selected from Nb ₂ O ₅ , TiO ₂ , Ti ₃ O ₅ , Ta ₂ O ₅ and LaTiO ₃ , or a mixture of materials selected from these. ,And,
The material contained in the low refractive index layer is SiO ₂ , LaSiO, Al ₂ O ₃ , and La _2x Al _2y O _3(x+y) (wherein x and y are 0.3 to 0.7, respectively _). Which represents a numeral in the range of 1), or a mixture of materials selected from these, the dielectric multilayer film according to any one of 1 to 6 above. ..

8. When the total thickness of the dielectric multilayer film is 3 μm or more and there are a plurality of the low refractive index layers, the interval between the low refractive index layers is 1.2 μm or less, and the plurality of the high refractive index layers. 8. The dielectric multilayer film according to any one of items 1 to 7, wherein each layer thickness is 500 nm or less.

9. The dielectric constant according to any one of items 1 to 8, wherein the amount of blue shift when the incident angle of light changes from 0° to 10° at a light wavelength of 635 nm is 6 nm or less. Body multilayer film.

10. A method for producing a dielectric multilayer film according to any one of claims 1 to 9, which comprises a step of forming the dielectric multilayer film by ion-assisted vapor deposition. Method for manufacturing multilayer film.

11. An optical see-through type image display device for projecting and displaying an image on an external landscape by projecting it to an observer's eye,
A display element that displays the image, a combiner that simultaneously guides image light from the display element and external light from the external scene to an observer, and two resin prisms that form the combiner,
The two resin prisms are bonded to each other, and the bonding surface includes a prism convex surface and a prism concave surface, and
An image display device, comprising the dielectric multilayer film according to any one of items 1 to 9 on the joint surface.

By the above means of the present invention, suppression of shape change of the dielectric multilayer film, crack prevention, optical characteristics (oblique light incidence characteristics) and having both productivity, the dielectric multilayer film formed on the resin substrate, its manufacturing method and It is possible to provide an image display device equipped with it.

The mechanism of action or mechanism of action of the present invention has not been clarified, but is presumed as follows.

The present inventor has organized past technical contents relating to the formation of a dielectric multilayer film, and has been addressed to problems such as suppression of shape change of the dielectric multilayer film, crack prevention, and optical characteristics such as blue shift and productivity. On the other hand, the dielectric multilayer film has a layer structure mainly composed of a high-refractive index material (for example, TiO ₂ or LaTiO ₃ ) and has a strong compressive stress without increasing the power during IAD (hereinafter referred to as IAD power). I thought that the solution would be to form the film without doing so. However, the following findings were obtained.

(1) In the case of a high refractive index material, columnar growth is likely to occur particularly when the IAD power is low, and the film density decreases as the layers are stacked, and the layer as a whole becomes tensile stress, which cannot solve the above problems. (2) It is also important to suppress the thermal stress that causes the shape change of the resin substrate, and it is preferable to set the film forming temperature as low as possible, but the interlayer interval (a cooling time is provided in each layer), the dome cooling mechanism. Also, the shielding of the radiant heat of the vapor deposition oblique component complicates the production process and lengthens the production time, resulting in poor productivity.
(3) If the directions of the intrinsic stress and the thermal stress of the multilayer film are opposite, cracks occur at the interface between the substrate and the film (that is, the film wants to stretch the base material, but the base material itself tends to shrink, so stress is applied. ..). If the intrinsic stress is a strong compressive stress, the substrate is largely deformed together with the thermal stress.
(4) If the IAD power is weakened so as to easily follow the deformation of the resin substrate, or if the film density of the multilayer film is reduced by vacuum deposition without IAD, the adhesion will decrease and a large amount of moisture will be obtained in the high temperature and high humidity test. Therefore, the light wavelength shift such as the blue shift becomes large. Further, film peeling occurs.

As a result of earnestly studying the above findings, the dielectric multilayer film has a layer structure in which high refractive index materials having a refractive index of 1.9 or more at an optical wavelength of 550 nm are alternately laminated, and the film forming temperature and IAD power are controlled. The high refractive index material is formed so as not to have a strong compressive stress, but columnar growth is likely to occur particularly when the IAD power is low, and the film density decreases as the layers are laminated and the layer as a whole has tensile stress. However, by adding a low-refractive-index layer such as SiO _{2 in} the middle of alternate lamination of high-refractive-index materials to reset the columnar growth once, the columnar growth can be eliminated, and as a result, the film density can be increased. I found it possible.

That is, when a dielectric multilayer film is formed on a resin substrate, the film should be formed with an appropriate IAD power so as to have a compressive stress, and a low-refractive layer such as SiO ₂ may be formed in the middle of an alternate laminated portion of high-refractive material. The columnar growth is eliminated to increase the film density, and the temperature during film formation is controlled to suppress the thermal stress of the resin substrate, thereby suppressing the shape change of the dielectric multilayer film, preventing cracks, and improving optical characteristics ( It is considered that it was possible to obtain a dielectric multilayer film in which the reduction in productivity was suppressed by film formation using oblique light incidence characteristics: suppression of blue shift and appropriate IAD power.

The schematic diagram which shows an example of a structure of the dielectric multilayer film of this invention. The graph which shows the light reflection characteristic of the dielectric multilayer film of this invention. The schematic diagram which shows an example of the vapor deposition apparatus using IAD. Example of optical see-through type image display device The graph which shows the light transmission characteristic of the dielectric multilayer film of this invention.

The dielectric multilayer film of the present invention is a dielectric multilayer film in which at least one low refractive index layer and a plurality of high refractive index layers are formed on a resin substrate, and the total thickness of the dielectric multilayer film is 2 μm. The refractive index of the plurality of high refractive index layers at the light wavelength of 550 nm is 1.9 or more and different from each other, and the plurality of high refractive index layers are alternately laminated to form an alternating laminated portion, and The low refractive index layer having a refractive index of less than 1.9 at a light wavelength of 550 nm is arranged between the alternating laminated portions. This feature is a technical feature common to or corresponding to the following embodiments.

The total film thickness of the dielectric multilayer film is a requirement of 2 μm or more, but in the range of 3 μm or more, the visibility is improved (the transmittance of the transmission band is high and the external scenery can be seen more). preferable.

As an embodiment of the present invention, from the viewpoint of manifestation of the effect of the present invention, the layer thickness of each of the alternating laminated portions is a requirement of 1.5 μm or less, but a range of 1.2 μm or less, It is preferable from the viewpoint of preventing the generation of cracks.

The difference in refractive index between the plurality of high refractive index layers is 0.2 or more, and the materials contained in the plurality of high refractive index layers may be the same or different, from the viewpoint of preventing the occurrence of cracks and It has a peak of light reflectance at a specific wavelength and is preferable from the viewpoint of configuring a see-through type image display device. The refractive index difference is preferably in the range of 0.25 or more from the viewpoint of improving visibility (the transmittance of the transmission band is high and the external scenery can be seen more), and the range of 0.3 or more is more preferable.
It is preferable that the dielectric multilayer film has an average refractive index of 1.95 or more from the viewpoint of forming a see-through type image display device having a light reflectance peak at a specific wavelength. The average refractive index is preferably in the range of 2.0 or more from the viewpoint of improving the visibility (small color unevenness caused by the positional deviation between the eyes of the observer and the image display surface), and the range of 2.1 or more is more preferable. preferable.

The layer thickness of the low refractive index layer is preferably 8 nm or more from the viewpoint of resetting the columnar growth of the high refractive index layer. The layer thickness is preferably 10 nm or more from the viewpoint of film thickness controllability during film formation, and more preferably 20 nm or more.

The stress per unit layer thickness of the low-refractive index layer and the high-refractive index layer being in the range of 0 to 500 MPa in the compression direction matches the direction of thermal stress of the resin substrate and prevents the occurrence of cracks. It is preferable from the viewpoint. The stress per unit layer thickness is preferably in the range of 0 to 300 MPa from the viewpoint of suppressing changes in the shape of the substrate.

The material contained in the high refractive index layer is at least one selected from Nb ₂ O ₅ , TiO ₂ , Ti ₃ O ₅ , Ta ₂ O ₅ , and LaTiO ₃ , or is selected from these. It is a mixture of materials, and the material contained in the low refractive index layer is at least one selected from SiO ₂ , LaSiO, Al ₂ O ₃ , and La _2x Al _2y O _{3 (x+Y).} It is preferable or a mixture of materials selected from these materials from the viewpoint of controlling the refractive index of the dielectric multilayer film. Among them, Ti ₃ O ₅ and LaTiO ₃ are preferable as the material contained in the high refractive index layer, and SiO ₂ and LaSiO are preferable as the low refractive index material.

When the total thickness of the dielectric multilayer film is 3 μm or more and there are a plurality of the low refractive index layers, the interval between the low refractive index layers is 1.2 μm or less, and the plurality of the high refractive index layers. It is preferable that each layer thickness is 500 nm or less from the viewpoint of suppressing columnar growth of the high refractive index layer.

At the light wavelength of 635 nm, the blue shift amount when the light incident angle changes from 0° to 10° is 6 nm or less, which reduces the wavelength shift of the optical characteristics and improves the visibility. And color unevenness caused by positional deviation of the image display surface is small).

The method for producing a dielectric multilayer film of the present invention is characterized by including a step of forming the dielectric multilayer film by ion assisted vapor deposition.

The image display device of the present invention is an optical see-through type image display device for projecting and displaying an image on an external landscape by projecting it to an observer's eye, and a display element for displaying the image and image light from the display element. It has a combiner that simultaneously guides external light from the external scenery to an observer, and two resin prisms that compose the combiner. The two resin prisms are bonded to each other, and the bonding surface is a prism. The present invention is characterized in that it comprises a convex surface and a concave surface of a prism, and that the dielectric multilayer film of the present invention is formed.

The following is a detailed description of the present invention, its components, and modes and modes for carrying out the present invention. In the present application, "to" is used to mean that the numerical values described before and after it are included as the lower limit value and the upper limit value.

<<Outline of Dielectric Multilayer Film of the Present Invention>>
The dielectric multilayer film of the present invention is a dielectric multilayer film in which at least one low refractive index layer and a plurality of high refractive index layers are formed on a resin substrate, and the total thickness of the dielectric multilayer film is 2 μm. That is, the refractive index at the light wavelength of 550 nm of the plurality of high refractive index layers is different from each other by 1.9 or more, and the plurality of high refractive index layers are alternately laminated to form an alternating laminated portion, and The low refractive index layer having a refractive index of less than 1.9 at a light wavelength of 550 nm is arranged between the alternating laminated portions.

Here, “high” and “low” of each refractive index layer refer to a relative refractive index, and the high refractive index layer may have a refractive index of 1.9 or more at a light wavelength of 550 nm and a low refractive index. The refractive index layer may have a refractive index of less than 1.9 at a light wavelength of 550 nm. Further, since the present invention is characterized in that an alternating laminated portion in which a plurality of high refractive index layers having different refractive indexes are laminated is formed, the high refractive index layer-1, the high refractive index layer-2... The notation of rate-n will be used.

The refractive index is the refractive index at a light wavelength of 550 nm, and each layer of the multilayer film is formed as a single layer, and the optical surface reflectance measurement at a light wavelength of 550 nm is performed using an Olympus microspectroscope USPM-RU III. It is calculated by performing. The refractive index of the layer obtained by adjusting the refractive index so as to fit the actually measured light reflectance data was specified using thin film calculation software (Essential Macleod) (Sigma Koki Co., Ltd.).

FIG. 1 is a schematic diagram showing an example of the structure of the dielectric multilayer film of the present invention. However, it is not limited to this. Further, in the figure, the high-refractive index layers forming the alternately laminated portions are two different layers, that is, the high-refractive index layer-1 and the high-refractive index layer-2, but a plurality of layers may be further provided.

The dielectric multilayer film 1 having a function of controlling the light reflectance is formed on, for example, a substrate 2 used for a resin prism that constitutes a combiner included in a see-through type image display device, for example, a high refractive index having a different refractive index. The alternating laminated portion 3 in which a plurality of layers-1 (H1) and high refractive index layers-2 (H2) are alternately laminated, and the high refractive index layer-1 (H1) and the high refractive index layer-2 (H2) And a low refractive index layer 4 having a lower refractive index. It is preferable to have a multi-layer structure in which alternating layers of these high refractive index layers and low refractive index layers are appropriately laminated between them. In FIG. 1, the low refractive index layers 4-1 and 4-2 are arranged between the alternating laminated portions 3-1, 3-2 and 3-3.

The “total layer thickness of the dielectric multilayer film” refers to the high refractive index layer-2 (H2) which is the uppermost layer of the dielectric multilayer film from the surface of the high refractive index layer-1 (H1) in contact with the substrate 2 in FIG. ) Refers to the thickness up to the surface.

The “layer thickness of each of the alternating laminated portions” is the thickness of the high refractive index layer-2 (H2) from the surface of the high refractive index layer-1 (H1) on the substrate side or the low refractive index layer 4 side in FIG. The thickness up to the surface opposite to the substrate.

“When there are a plurality of low-refractive-index layers, the interval between the low-refractive-index layers” refers to the low-refractive-index layer 4-2 from the surface of the low-refractive-index layer 4-1 on the side opposite to the substrate in FIG. The distance to the surface of the substrate side.
A specific layer structure will be described in the section of Examples.

The dielectric multilayer film of the present invention preferably satisfies the following characteristics as required performance from the image display device provided.

(A) Optical characteristics: It has a peak wavelength of a reflection band at 465 nm, 520 nm, and 635 nm (each ±5 nm) at a light incident angle of 10°. It is preferable that the peak reflectance is 60% or more and the luminous transmittance is 70% or more. The shift of the peak wavelength at the incident angle of 0 to 10° is preferably 6 nm or less at 635 nm.

Figure 2 shows a graph of the light reflection characteristics of a dielectric multilayer film that satisfies the above optical characteristics.

(B) Change in shape: It is preferable that the change is 6 μm or less at the end of the resin prism before and after the formation of the dielectric multilayer film.

(C) Initial appearance: No cracking or film lifting of the dielectric multilayer film is observed.

(D) Reliability: No cracking or film floating is observed in high temperature and high humidity (60°C/90%RH, 240h) storage and heat shock test (30 cycles between -20 and 70°C). Is preferable, and the peak wavelength shift is preferably 2 nm or less.

Also, here, as the definition of the film stress, when the substrate warps with the film inside (the film tries to shrink), the sign that there is a tensile stress in the film is +. On the contrary, when the film is warped with the film outside (the film is about to expand), the compressive stress is assumed and the symbol is represented by −. The stress per unit layer thickness of the low refractive index layer and the high refractive index layer according to the present invention is preferably in the range of 0 to 500 MPa in the compression direction, but "0 to 500 MPa in the compression direction" means " It is synonymous with “0 to −500 MPa as film stress”.

Specifically, the film stress can be measured by a method using X-ray diffraction or a method using infrared measurement. Further, it is possible to measure the compressive stress by a method of measuring the warp of the substrate and substituting it in the following equation using a laser beam as described in Non-Patent Document 1. In this case, the measurement is performed using a sample in which each material is formed as a single layer on a thin glass plate having a thickness of 50×10 mm and a thickness of 0.1 mm to form an optical film thickness λ/4 (λ=550 nm). The optical film thickness is the value of nd obtained by multiplying the physical film thickness d by the refractive index n.

For example, the substrate will bend due to the film stress of the formed thin film. At this time, when the displacement δ at the free end is measured, the film stress σ is approximated by the following equation.

σ=(Eb ² )/{3(1-ν)l ² d}×δ
Here, E: Young's modulus of the substrate, b: substrate thickness, l: substrate length, ν: substrate Poisson's ratio, d: thin film thickness.

Using the above measurement method, it is possible to know the direction and magnitude of stress from a sample in which a single layer is formed on a substrate.

The details of the dielectric multilayer film of the present invention will be described below.

[1] Configuration of Dielectric Multilayer Film As described above, the dielectric multilayer film of the present invention is characterized in that it has the alternating laminated portions composed of a plurality of high refractive index layers and the low refractive index layers between them. is there. It is preferable to have a multilayer structure in which these high refractive index layers and low refractive index layers are alternately laminated. The number of layers is not particularly limited, but it is preferably 80 or less from the viewpoint of maintaining high productivity and obtaining a desired antireflection layer. That is, although the number of layers depends on the required optical performance, the reflectance of the specific light wavelength body in the visible region can be increased by stacking the layers of about 20 to 40 layers. It is preferable that the upper limit is 80 layers or less from the viewpoint that the stress of the entire film becomes large and the film can be prevented from peeling off.

The dielectric multilayer film according to the present invention utilizes the spectral transmission and reflection functions within a discrete light wavelength range so that the visible light reflection ability is exhibited in a specific wavelength range of the visible light range. For example, when incident light traverses between two materials having different refractive indices, for example, an interface between the high refractive index layer-1 and the high refractive index layer-2, the incident light path has a refraction of each material. It changes according to the difference in rates. The larger the difference in refractive index, the larger the refraction of incident light. Therefore, by using the layers having different refractive indexes, an excellent reflection effect can be obtained.

In the present invention, it is preferable that the refractive index difference between the high refractive index layer-1 and the high refractive index layer-2, which are high refractive index layers adjacent to each other, be 0.2 or more. The upper limit is not particularly limited, but is usually preferably 0.6 or less.

The difference in refractive index and the required number of layers can be simulated or calculated by using commercially available thin film calculation software (Essential Macleod) (Sigma Optical Co., Ltd.). For example, in order to obtain a light reflectance of 60% or more at 635 nm, if the refractive index difference is smaller than 0.1, it is necessary to stack 200 layers or more, which not only lowers the productivity but also scatters at the stacking interface. May become large, the transparency may deteriorate, and it may be very difficult to manufacture without failure. Therefore, it is practically necessary to design to have the above-mentioned difference in refractive index.

Since the reflection at the interface between the adjacent layers depends on the refractive index ratio between the layers, the larger the refractive index ratio, the higher the reflectance. Further, when viewed as a single-layer film, if the optical path difference between the reflected light on the layer surface and the reflected light on the layer bottom is represented by n·d=wavelength/4, the reflected light is strengthened by the phase difference. It can be controlled to match and the reflectance can be increased. Here, n is the refractive index and d is the physical layer thickness of the layer. The reflection can be controlled by utilizing this optical path difference. By utilizing this relationship, the refractive index and layer thickness of each layer can be controlled to control the reflection of ultraviolet light, visible light, or near infrared light.

That is, the reflectance in a specific wavelength region can be increased depending on the refractive index of each layer, the layer thickness of each layer, and the stacking mode of each layer.

The average refractive index of the entire dielectric multilayer film at a light wavelength of 550 nm is preferably 1.95 or more.

The refractive index of the high refractive index layer for the light wavelength of 550 nm is preferably in the range of 1.9 to 2.50, and the refractive index of the low refractive index layer for the light wavelength of 550 nm is 1.3 to 1.6. It is preferably within the range.

As the material used for the dielectric multilayer film (high refractive index layer, low refractive index layer) according to the present invention, the materials contained in the high refractive index layer are Nb ₂ O ₅ , TiO ₂ , and Ti ₃ O ₅ , Ta ₂ O ₅ and LaTiO ₃ , or a mixture of materials selected from these, and the material contained in the low refractive index layer is SiO ₂ , LaSiO. , Al ₂ O ₃ , and La _2x Al _2y O _3(x+Y) (wherein x and y each represent a range of 0.3 to 0.7). Or, a mixture of materials selected from these is preferable from the viewpoint of controlling the refractive index of the dielectric multilayer film.

The high refractive index layer may be, for example, a mixture of Ta oxide and Ti oxide, or a mixture of Ti oxide, Ta oxide, La oxide and Ti oxide, and the like. preferable. In the present invention, Ta ₂ O ₅ or TiO ₂ is preferable, and Ta ₂ O ₅ is more preferable.

Further, the low refractive index _layer, SiO 2, MgF _2, or and Al ₂ O _3, it is preferable from the viewpoint of the light reflectance is such as a mixture of SiO ₂ and Al ₂ O _3.

The thickness of the dielectric multilayer film (the total thickness when a plurality of layers are laminated) is 2 μm or more, preferably within the range of 2 to 8 μm. When the thickness is 2 μm or more, antireflection optical characteristics can be exhibited, and when the thickness is 8 μm or less, surface deformation due to film stress of the multilayer film itself can be prevented.

The thickness of the alternate laminated portion in which a plurality of high refractive index layers are laminated is preferably 1.5 μm or less. The individual layer thickness of the high refractive index layer at that time is appropriately determined by the above-mentioned simulation or calculation.

Further, it is preferable that the layer thickness of the low refractive index layer arranged between them is 8 nm or more from the viewpoint of suppressing columnar growth of the high refractive index layer. The range is preferably 10 nm or more.

Further, when the total thickness of the dielectric multilayer film is 3 μm or more, and when there are a plurality of the low refractive index layers, the interval between the low refractive index layers is 1.2 μm or less, and the plurality of the high refractive index layers have a high refractive index. It is preferable that each layer of the index layers has a thickness of 500 nm or less. The distance between the low refractive index layers is preferably 1.0 μm or less. The thickness of each of the plurality of high refractive index layers is preferably in the range of 0 to 300 nm.

[2] Method for Producing Dielectric Multilayer Film First, the resin base material used for the dielectric multilayer film is preferably a transparent resin base material in the visible light range, and is not particularly limited.

The resin that can be used as the transparent resin substrate is not particularly limited, and examples thereof include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and modified polyester, polyethylene (PE), polypropylene (PP), polystyrene ( PS), cycloolefin (COP) and other polyolefin resins, polyvinyl chloride, polyvinylidene chloride and other vinyl resins, polyether ether ketone (PEEK), polysulfone (PSF), polyether sulfone (PES), polycarbonate ( PC), polyamide, polyimide resin, acrylic resin, triacetyl cellulose (TAC) and the like. Of these, cycloolefin (COP), polycarbonate (PC), acrylic resin and the like are preferable. These resins may be used alone or in combination.

The thickness and type of the resin base material are not particularly limited as long as they are selected within a range that satisfies the characteristics of visible light transmittance of the device including the dielectric multilayer film of the present invention.

The thickness of the resin base material is preferably about 1 to 10 mm. The resin base material may be a resin prism, which is provided in an optical see-through type image display device described later, and in this case, the concave surface joint portion or the convex surface joint portion of the resin prism is the same as the resin substrate used in the present invention. Become.

The resin base material preferably has a transmittance of 85% or more, particularly 90% or more, in the visible light region shown in JIS R 3106:1998. It is preferable that the resin base material has the above transmittance or more from the viewpoint of easily adjusting the luminous transmittance in the normal direction of the dielectric multilayer film to 80% or more.

As a method for forming a dielectric multilayer film by forming a thin film of metal oxide or the like on a substrate, a vapor deposition system includes a vacuum vapor deposition method, an ion beam vapor deposition method, an ion plating method, and a sputtering system includes a sputtering method and an ion beam sputtering. Although a method, a magnetron sputtering method and the like are known, it is preferable to use IAD as a film forming method for forming the dielectric multilayer film of the present invention from the viewpoint of forming a high density thin film.

IAD is a method of applying a high kinetic energy of ions during film formation to form a dense film or enhancing the adhesion of the film. For example, an ion beam method is an ionized gas irradiated from an ion source. This is a method of accelerating the deposition material by molecules and forming a film on the substrate surface. IAD is also called "ion beam assist method".

FIG. 3 is a schematic diagram showing an example of a vacuum vapor deposition apparatus using IAD.

A vacuum vapor deposition apparatus 10 using IAD (hereinafter, also referred to as an IAD vapor deposition apparatus in the present invention) includes a dome 13 inside a chamber 12, and a substrate 14 is arranged along the dome 13. The vapor deposition source 15 includes an electron gun or a resistance heating device that evaporates the vapor deposition material, and the vapor deposition material 16 scatters from the vapor deposition source 15 toward the substrate 14 and is condensed and solidified on the substrate 14. At that time, the ion beam 18 is irradiated from the IAD ion source 17 toward the substrate, and the high kinetic energy of the ions is applied during the film formation to form a dense film or enhance the adhesion of the film.

Here, the substrate 14 is preferably made of polycarbonate resin (PC), cycloolefin resin (COP), acrylic resin, or the like.

A plurality of vapor deposition sources 15 may be arranged at the bottom of the chamber 12. Here, one evaporation source is shown as the evaporation source 15, but the number of the evaporation sources 15 may be plural. The film-forming material (vapor-depositing material) of the vapor-deposition source 15 is generated by an electron gun to generate a vapor-depositing substance 16, and the film-forming material is scattered and adhered to the substrate 14 (for example, a resin-molded prism) installed in the chamber 12, thereby forming the material. A layer made of a film material (for example, a low refractive index material such as SiO ₂ , MgF ₂ or Al ₂ O ₃ layer and a high refractive index material such as LaTiO ₃ , Ta ₂ O ₅ or TiO ₂ ) is a substrate. A film is formed on 14.

Further, the chamber 12 is provided with a vacuum exhaust system (not shown), so that the inside of the chamber 12 is evacuated. The degree of reduced pressure in the chamber is usually in the range of 1×10 ⁻⁴ to 1×10 ⁻¹ Pa, preferably 1×10 ⁻³ to 1×10 ⁻² Pa.

The dome 13 holds at least one holder (not shown) that holds the substrate 14, and is also called a vapor deposition umbrella. The dome 3 has an arcuate cross section, and has a rotationally symmetric shape in which the dome 3 passes through the center of a chord connecting both ends of the arc and rotates about an axis perpendicular to the chord as a rotational symmetry axis. When the dome 13 rotates about the axis at a constant speed, for example, the substrate 14 held by the dome 13 via the holder revolves around the axis at a constant speed.

The dome 13 can hold a plurality of holders arranged side by side in the rotation radius direction (revolution radius direction) and the rotation direction (revolution direction). As a result, it becomes possible to simultaneously form a film on the plurality of substrates 14 held by the plurality of holders, and it is possible to improve the manufacturing efficiency of the element.

The IAD ion source 17 is a device that introduces argon or oxygen gas into the main body to ionize them and irradiates the ionized gas molecules (ion beam 18) toward the substrate 14. Argon gas or oxygen gas has a positive charge accumulated on the substrate in order to prevent the phenomenon that the whole substrate is positively charged (so-called charge-up) due to the accumulation of positive ions irradiated from the ion gun on the substrate. It is also used as a neutralizer that electrically neutralizes.
As the ion source, a Kauffman type (filament), a hollow cathode type, an RF type, a bucket type, a duoplasmatron type, or the like can be applied. By irradiating the substrate 14 with the above-mentioned gas molecules from the IAD ion source 17, for example, molecules of the film forming material that are evaporated from a plurality of evaporation sources can be pressed against the substrate 14, and a film having high adhesion and denseness can be formed on the substrate. A film can be formed on 14. Although the IAD ion source 7 is installed so as to face the substrate 14 at the bottom of the chamber 12, it may be installed at a position offset from the facing axis.

The ion beam used in IAD is used at a lower degree of vacuum and the acceleration voltage tends to be lower than the ion beam used in the ion beam sputtering method. For example, an ion beam having an accelerating voltage of 100 to 2000 V, an accelerating current of 100 to 2000 mA, and a neutralizer bias current of 100 to 2000 mA can be used. In the film forming step, the irradiation time of the ion beam can be set to, for example, 1 to 800 seconds, and the irradiation number of particles of the ion beam can be set to, for example, 1×10 ¹³ to 5×10 ¹⁷ particles/cm ² . The ion beam used in the film formation step can be an oxygen ion beam, an argon ion beam, or an oxygen/argon mixed gas ion beam. For example, it is preferable that the oxygen introduction amount is within a range of 20 to 60 sccm and the argon introduction amount is within a range of 0 to 15 sccm. “SCCM” is an abbreviation for standard cc/min, and is a unit indicating how many cc flows per minute at 0° C. and 1 atm (atmospheric pressure 1013 hPa).

The monitor system (not shown) is a system that monitors the wavelength characteristics of the layer formed on the substrate 14 by monitoring the layer evaporated from each evaporation source 15 and attached to itself during vacuum film formation. .. With this monitor system, the optical characteristics of the layer formed on the substrate 14 (for example, spectral transmittance, spectral reflectance, optical layer thickness, etc.) can be grasped. The monitoring system also includes a crystal layer thickness monitor, which can also monitor the physical layer thickness of the layer deposited on the substrate 14. The monitor system also functions as a control unit that controls ON/OFF switching of the plurality of evaporation sources 15 and ON/OFF switching of the IAD ion source 17 according to the monitoring result of the layer.

Further, when the dielectric multilayer film of the present invention is performed by IAD, it can be performed while heating (for example, 300° C. or higher), but from the viewpoint of adjusting the thermal stress of the substrate, heating is not performed at room temperature ( The temperature is preferably adjusted to 25°C).

[3] Image Display Device The image display device of the present invention is an optical see-through type image display device that displays an image by superimposing it on an external landscape and displaying it on an observer's eye, and a display element for displaying the image and the display element. A combiner that simultaneously guides the image light from the outside scene and the outside light from the outside scene to the observer, and two resin prisms that constitute the combiner, and the two resin prisms are joined to each other. The joining surface is composed of a prism convex surface and a prism concave surface, and the dielectric multilayer film of the present invention is formed on the convex surface or the concave surface.

FIG. 4 shows an example of an optical see-through type image display device.

In FIG. 4, the image display device 20 includes a component 25 that reflects the image information input and output from the image display element 21 by the dielectric multilayer film 24 provided on the joint surface of the upper prism 22 and the lower prism 23, and the external scenery. An observer 27 can visually recognize the transmitted light component 26 that is incident from above.

A head-mounted display device (head-mounted display, hereafter HMD) is known as one of the display devices. Although the HMD is compact, it has a merit of being hands-free because it can substantially view an image on a large screen and can be worn on the head. In such an HMD device, light emitted from an image display element is normally transmitted and reflected by a combiner made of a transparent base material including a half mirror material and the like. Therefore, the observer can acquire information as a virtual image displayed at a distance away from the combiner by a certain distance, and at the same time acquire external environment information that is visually recognized through the combiner.

　By utilizing the above-mentioned hands-free property and the feature that virtual images and external information can be acquired at the same time, it can be used as an instruction display during work. Specifically, by outputting instructions such as a work procedure to an HMD screen to an operator who is performing work using both hands, work while confirming the instructions without interrupting work using both hands Will be able to do.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, "parts" or "%" are used, but unless otherwise specified, "parts by mass" or "mass%" are shown.

Specific examples of the dielectric multilayer film according to this embodiment will be described below. A film forming apparatus (BIS-1300) (manufactured by Syncron Co., Ltd.) was used for manufacturing the following dielectric multilayer film.

First, we calculated the relationship between the change in IAD power and the refractive index and stress when a single layer of the material forming the dielectric multilayer film was formed on the glass plate.

From Table I, it was found that changing the IAD power changes the refractive index and stress of each material. Thus, the desired design values of the refractive index and the stress in the example were controlled by changing the IAD power.

[Production of Dielectric Multilayer Film Comparative Example 1]
As a resin substrate, using TiO ₂ and SiO ₂ (both manufactured by Merck Performance Materials, Inc.) on ZEONEX E48R (Nippon Zeon Co., Ltd.) having a thickness of 5 mm as a cycloolefin resin system under the following conditions: The multilayer film shown in Table II was formed into a dielectric multilayer film comparative example 1.

<Film forming conditions>
(Conditions in chamber)
Heating temperature 25℃
Starting vacuum degree 1.5×10 ^-3 Pa
(Evaporation source of film forming material)
Electron Gun <Formation of Material 1 (Layer 1) and Material 2 (Layer 2)>
Material 1: TiO ₂ : Refractive index 2.40
The film forming material was loaded in the first evaporation source and vapor deposition was performed at a film forming rate of 3 nm/sec to form a high refractive index layer having a thickness of 13.7 nm on the substrate. The high refractive index layer was formed by IAD.

As the IAD, an accelerating voltage of 700 V, an accelerating current of 700 mA and a neutralizing current of 700 mA were used, and an apparatus of RF ion source “OIS One” manufactured by Optolan Corporation was used. As for the IAD introduction gas, O ₂ 50 sccm was introduced into the electron gun, and Ar gas 10 sccm was introduced into the neutralizer.

Material 2: SiO ₂ : Refractive index 1.42
Next, the substrate on which the material 1 was deposited was loaded with the material 2 in the second evaporation source, and vapor deposition was performed at a deposition rate of 7 nm/sec with the IAD power set to 0, and a low thickness of 211.9 nm was deposited on the material 1. A refractive index layer was formed.

Subsequently, as shown in Table II, Material 1 and Material 2 were laminated under the same conditions from Layer 3 to Layer 23 to obtain a dielectric multilayer film comparative example 1.

In the dielectric multilayer film comparative example 1, the material 1:TiO ₂ has a total layer thickness of 1378.6 nm, the material 2:SiO ₂ has a total layer thickness of 1256.2 nm, and the dielectric multilayer film 1 has a total layer thickness of 2634.8 nm. The average refractive index was 1.93.

The layer thickness (film thickness) and refractive index of each layer were measured by the following methods.

(Measurement of layer thickness)
(1) TiO ₂ , H 4, and SiO ₂ are formed in advance in a film thickness of ¼λ (λ=550 nm) on a white glass substrate, and the light reflectance is measured.
(2) When formed in (1), each layer is formed on the TiO ₂ , H 4, and SiO ₂ film under the above-mentioned film forming conditions, the light reflectance is measured, and the refractive index of the layer and the layer are calculated from the change amount. Calculate the thickness.
The light reflectance was measured with a microspectrophotometer USPM-RU III manufactured by Olympus at a light wavelength of 550 nm.

H4 is a trade name “H4”: LaTiO ₃ manufactured by Merck Performance Materials, Inc.

(Measurement of refractive index)
The refractive index was calculated by forming each layer of the multilayer film as a single layer and measuring the light reflectance at a light wavelength of 550 nm using a spectrophotometer U-4100 manufactured by Hitachi High Technologies. The refractive index of the obtained layer was specified by adjusting the refractive index so as to fit the actually measured light reflectance data using thin film calculation software (Essential Macleod) (Sigma Optical Co., Ltd.).

The average refractive index of the entire dielectric multilayer film was obtained by the following formula.
Average refractive index=(n ₁ ×d ₁ +n ₂ d ₂ +n ₃ d ₃ ...)/(d ₁ +d ₂ +d ₃ ...)
However, n ₁ , n ₂ , n 3... Represent the refractive index of each layer. _{d 1, d 2, d 3} ·· represents the thickness of the individual layers.

(Measurement of stress)
Regarding the stress obtained by the following measuring method, + represents the tensile direction and − represents the compression direction. Both are stress values per unit layer thickness. The stress measurement was obtained by the method described in Non-Patent Document 1. Each material was formed into a single layer on a thin glass plate having a thickness of 50×10 mm and a thickness of 0.1 mm, and the warp of the thin glass plate was analyzed using laser light to calculate the compressive stress.

The substrate is bent by the film stress of the thin film. At this time, when the displacement δ at the free end is measured, the film stress σ is approximated by the following equation.
σ=(Eb ² )/{3(1-ν)l ² d}×δ
Here, E is the Young's modulus of the substrate, b is the thickness of the substrate, l is the length of the substrate, ν is the Poisson's ratio of the substrate, and d is the thickness of the thin film.

[Fabrication of Comparative Examples 2 to 4 of Dielectric Multilayer Film]
In the preparation of the dielectric multilayer film comparative example 1, the following materials and IAD power were changed, and the dielectric multilayer film comparative examples 2 to 4 having the total number of layers of 23 were prepared with the configurations shown in Table 1.

Comparative Example 2: Material 1: TiO ₂ AD Refractive index 2.4 at 700 power setting.
Material 2: The refractive index is 1.45 by setting the SiO ₂ IAD power to 700.

Comparative Example 3: Material 1: TiO ₂ AD Refractive index 2.2 by setting power 300.
Material 2: H4 (trade name “H4” (LaTiO ₃ ), manufactured by Merck Performance Materials, Inc.) IAD power of 300, and a refractive index of 1.95. The H4 film formation rate was 4 nm/sec.

Comparative Example 4: Material 1: TiO ₂ AD The refractive index was 2.5 when the power was set to 1000.
Material 2: H4 IAD power 1000 setting, refractive index 2.1.

[Production of Dielectric Multilayer Film Example 1]
A dielectric multilayer film Example 1 in which a plurality of high-refractive index layers were formed as alternating laminated portions and a low-refractive index layer was formed between them in the configuration of Table III was produced.

As the resin substrate, a cycloolefin resin, on 5mm thick of ZEONEX E48R (Nippon Zeon Co., Ltd.), H4 stacked alternately by laminating a plurality of (refractive index 2.1) and TiO ₂ (refractive index 2.4) Part was formed, SiO ₂ which is a low refractive index layer material was formed between the laminated alternating parts, and the film was formed under the layer thickness conditions shown in Table III to prepare a dielectric multilayer film Example 1.

The dielectric multilayer film Example 1 has a total layer thickness of 512.9 nm for TiO _2, a total layer thickness of 1558.4 nm for H 4, and a total layer thickness of 8.0 nm for the low refractive index layer SiO _2. Had a total film thickness of 2079.3 nm and an average refractive index of 2.17.

[Production of Dielectric Multilayer Film Examples 2 to 9]
In the preparation of the dielectric multilayer film Example 1, the dielectric multilayer films Examples 2 to 9 were prepared by IAD so as to have the layer constitutions of Table III, Table IV, Table V and Table VI. The TiO ₂ b used in Example 5 was obtained by setting the IAD power to 300 and changing the refractive index of TiO ₂ to 2.2.

The types of materials used in Comparative Examples 1 to 4 and Examples 1 to 9 of dielectric multilayer film, refractive index, stress, minimum layer thickness of low refractive index layers, and layer thickness of alternate laminated portions of high refractive index layers. Are listed in Table VII below.

The following evaluations were performed on the dielectric multilayer film samples prepared above.

<<Evaluation>>
(1) Visibility Definition: Optical characteristics at an incident angle of 10°. By simultaneously satisfying the requirements for the light reflectance and the light transmittance, it is possible to achieve both visibility of the image and the outside world.
Measurement: Measured with the concave prism formed and the convex prism without film bonded with an adhesive. Transmittance is measured with a multi-channel spectroscope MCPD-3000 manufactured by Otsuka Electronics Co., Ltd.
For the reflectance, the value of (100%-transmittance) was calculated.

Judgment: ◯: The following two items are satisfied x: Either or both items are not satisfied ・The light reflectances at wavelengths of 465 nm, 520 nm, and 635 nm are all 60% or more.
-In the visible light range, the standardized color matching function is multiplied by the transmittance of the dielectric multilayer film at a wavelength of 1 nm pitch.
"Sum of values calculated for each wavelength"/"Sum of color matching functions standardized for each wavelength" has a light transmittance of 70% or more.

(2) Wavelength shift amount Definition: The wavelength shift amount of the light reflectance peak when the incident angle changes from 0° to 10°.
Of the three reflection peaks in the visible light region, the peak on the longest wavelength side (around 635 nm) was evaluated.
Measured with the concave prism formed and the convex prism without film bonded with an adhesive.
In the measurement, the transmittance was measured with a multi-channel spectroscope MCPD-3000 manufactured by Otsuka Electronics Co., Ltd. at any incident angle, and the shift amount was calculated.

Judgment: 6 nm or less x: 6 nm or more

(3) Shape change Definition: The amount of deformation of the tip when a film is formed on the entire concave surface of the resin prism of the image display device. This is an example, and the present invention is not limited to the image display device. The measurement was performed by measuring the prism shape before and after film formation with a high-precision three-dimensional measuring machine UA3P manufactured by Panasonic Corporation, and calculating the amount of deformation.

Judgment ○: Less than 4 μm ×: 4 μm or more

(4) Appearance Definition: The presence or absence of cracks in the dielectric multilayer film or the film generated from the resin substrate was evaluated.
The measurement was visually performed while irradiating a prism formed with a Handylight P5R manufactured by Ledlenser.

Judgment ◯: No cracks Δ: 1 or more cracks, less than 5 cracks X: 5 or more cracks The above evaluation results are shown in Tables VII and VIII.

In Comparative Example 1, the alternating layers in the compression direction and the tensile direction generate stress at the layer interface, and thus cracks occur.

In Comparative Example 2, since the refractive index of SiO ₂ is low, the wavelength shift of the optical characteristics due to the incident angle shift is large.

In Comparative Example 3, when laminated, the film stress is in the tensile direction, and a force acts in the direction opposite to the thermal stress, so cracks occur.

In Comparative Example 4, since the film stress and the thermal stress (IAD becomes high temperature due to high power) strongly act in the compression direction, the shape change of the resin substrate is large. The dielectric multilayer films of Examples 1 to 9 are excellent in visibility, wavelength shift amount, shape change and appearance, and the superiority of the constitution of the present invention is clear.

Further, from Table VIII, in Examples 1 to 9, the light reflectance peaks at 465 nm, 520 nm and 635 nm are 60% or more (>R60%), and the luminous transmittance is 70% or more (>T70). %), which means that the specifications of the dielectric multilayer film of the present invention are satisfied.

FIG. 5 is a graph showing the spectral characteristics of the dielectric multilayer film obtained in Example 2. It can be seen that the visibility of the image and the outside world can be compatible by simultaneously satisfying the specifications of the light reflectance and the light transmittance at an incident angle of 10°. In particular, it is clear that the luminous transmittance is excellent.

In addition, the evaluation that the appearances of Examples 1 and 2 are Δ is because the layer thickness of each of the alternately laminated portions exceeds 1.5 μm, and the invention is achieved by adjusting the layer thickness to 1.5 μm or less. The effect of becomes large.

In the above example, when a plurality of low refractive index layers are provided for the sake of simplification, all the layers have the same film thickness in the structure. The thickness does not have to be constant. Further, the layer thickness ratios of the material 1 and the material 2 are the same in most of the examples for simplification, but this layer thickness ratio is not limited regardless of the invention.

Further, as a material contained in the high refractive index layer, Nb ₂ O ₅ , Ti ₃ O ₅ or Ta ₂ O ₅ is used instead of TiO ₂ and H 4, respectively, and a material contained in the low refractive index layer. As a substitute for SiO ₂ , LaSiO, Al ₂ O ₃ or La _2x Al _2y O _3(x+y) (wherein x and y each represent a number in the range of 0.3 to 0.7). When each of the above is used, the effects according to the present invention of suppressing the shape change of the dielectric multilayer film, preventing cracks, improving the optical characteristics (oblique light incidence characteristics) and improving the productivity are similarly obtained.

Since the dielectric multilayer film of the present invention is a dielectric multilayer film formed on a resin substrate, which has both shape change suppression, crack prevention, optical characteristics (oblique light incidence characteristics) and productivity, the image can be displayed outside It is preferably used for an optical see-through type image display device that projects and displays it on a viewer's eye by superimposing it on a landscape.

DESCRIPTION OF SYMBOLS 1 Dielectric multilayer film 2 Substrate 3-1 and 3-2 Alternately laminated part 4-1 and 4-2 Low refractive index layer H1 and H2 High refractive index layer 10 IAD vapor deposition apparatus 12 Chamber 13 Dome 14 Substrate 15 Vapor deposition source 16 Vapor deposition Material 17 IAD ion source 18 Ion beam 20 Image display device 21 Image display device 22 Upper prism 23 Lower prism 24 Dielectric multilayer film 25 Light-reflecting component 26 Transmitted light component incident from the outside scene 27 Observer

Claims (11)

1. A dielectric multilayer film comprising at least one low refractive index layer and a plurality of high refractive index layers on a resin substrate,
   The total thickness of the dielectric multilayer film is 2 μm or more,
   The plurality of high refractive index layers have different refractive indices at a light wavelength of 550 nm of 1.9 or more, and have a plurality of high refractive index layers alternately laminated, and
   A dielectric multilayer film, wherein the low refractive index layer having a refractive index of less than 1.9 at a light wavelength of 550 nm is arranged between the alternating laminated portions.
2. The dielectric multilayer film according to claim 1, wherein the layer thickness of each of the alternating laminated portions is 1.5 μm or less.
3. The refractive index difference between the plurality of high refractive index layers is 0.2 or more, and the materials contained in the plurality of high refractive index layers may be the same or different. 2. The dielectric multilayer film according to 2.
4. The dielectric multilayer film according to any one of claims 1 to 3, wherein the average refractive index of the dielectric multilayer film at a light wavelength of 550 nm is 1.95 or more.
5. The dielectric multilayer film according to any one of claims 1 to 4, wherein the layer thickness of the low refractive index layer is 8 nm or more.
6. The stress per unit layer thickness of the low refractive index layer and the high refractive index layer is in the range of 0 to 500 MPa in the compression direction, according to any one of claims 1 to 5. Dielectric multilayer film.
7. The material contained in the high refractive index layer is selected from Nb ₂ O ₅ , TiO ₂ , Ti ₃ O ₅ , Ta ₂ O ₅ and LaTiO ₃ , or a mixture of materials selected from these. ,And,
   The material contained in the low refractive index layer is SiO ₂ , LaSiO, Al ₂ O ₃ , and La _2x Al _2y O _3(x+y) (wherein x and y are 0.3 to 0.7, respectively _). It represents a numeral in the range of 1), or is a mixture of materials selected from these. 7. The dielectric multilayer film according to any one of claims 1 to 6. ..
8. When the total thickness of the dielectric multilayer film is 3 μm or more and the plurality of low refractive index layers are present, the interval between the low refractive index layers is 1.2 μm or less, and the plurality of high refractive index layers are provided. The dielectric multilayer film according to any one of claims 1 to 7, wherein each layer thickness is 500 nm or less.
9. 9. The dielectric according to any one of claims 1 to 8, wherein the amount of blue shift when the incident angle of light changes from 0° to 10° at a light wavelength of 635 nm is 6 nm or less. Body multilayer film.
10. A method of manufacturing a dielectric multilayer film according to claim 1, wherein the dielectric multilayer film is manufactured by ion-assisted vapor deposition. Method for manufacturing multilayer film.
11. An optical see-through type image display device for projecting and displaying an image on an external landscape by projecting it to an observer's eye,
    A display element that displays the image, a combiner that simultaneously guides image light from the display element and external light from the external scene to an observer, and two resin prisms that form the combiner,
    The two resin prisms are bonded to each other, and the bonding surface includes a prism convex surface and a prism concave surface, and
    An image display device, comprising the dielectric multilayer film according to any one of claims 1 to 9 on the bonding surface.

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