JP3353948B2 - Beam splitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam splitter.

[0002]

2. Description of the Related Art In general, resin optical parts can be made more complicated, lower in cost and lighter in weight than glass optical parts. It has the advantage that it is easier to process than those made of. For this reason, in recent years, the frequency of using resin parts using optical parts such as lenses, mirrors, and prisms as materials is increasing. However, resin-made beam splitters have not been used so far.

[0003] On the other hand, many conventional proposals have been made for a glass beam splitter.
JP-A-60-28603 discloses that from the glass substrate (prism) side, the first layer is Al ₂ O ₃ , the second layer is Ag, and the third layer is ZrO ₂ , TiO ₂ , CeO _2. , Zn
A beam splitter in which a thin film made of S or the like is formed is disclosed.

[0004]

In order to obtain a beam splitter having sufficient characteristics over a wide wavelength range, a high-refractive-index material is always required. ₂ , TiO ₂ ,
CeO ₂ , ZnS or the like is often used.

However, when a resin substrate is used, ZrO ₂ , TiO _{2 and the} like have a high melting point, and the same apparatus is used as in the case of forming a film on a normal glass substrate. In, the resin substrate is heated by the influence of radiant heat from the evaporation source, and the surface of the resin substrate is damaged and the adhesion with a film formed is weakened, or the surface accuracy which is most important for optical components is deteriorated. There was fear. This is particularly noticeable when a heat-sensitive acrylic resin (PMMA) is used for the substrate. As a countermeasure, a method of increasing the distance from the evaporation source to the resin substrate or providing a shielding plate between the evaporation source and the resin substrate to reduce the influence of radiant heat from the evaporation source can be considered. However, each of the above methods requires a significant modification of a film forming apparatus, and thus has a disadvantage that it cannot be used as it is as a conventional apparatus for forming a film on a glass substrate. In addition, the above method inevitably requires a longer deposition time, which is not preferable in terms of productivity.

The above problem in the case of using a resin substrate can be solved by using a material having a low radiant heat from the evaporation source. Examples of such a material include CeO ₂ and ZnS used in the above-mentioned prior art. Can be. But,
CeO ₂ is disadvantageous in that it is easily damaged, has low moisture resistance, and has large absorption in a short wavelength region. In addition, ZnS is weaker and more easily damaged than CeO ₂ , has low moisture resistance, is water-soluble, and has the disadvantage that its properties change when left in the air after film formation.

Further, when a conventional film configuration used for a glass substrate is applied to a resin substrate as it is, a large stress is applied to the film because the resin substrate has a larger expansion coefficient than the glass substrate, and the formed film has a large stress. There is a problem that cracks are easily generated.

The present invention has been made in view of the above problems, and has high adhesion to a film regardless of whether the substrate is glass or resin, and does not deteriorate the surface accuracy of the substrate.
It is another object of the present invention to provide a beam splitter which can easily form a film using a conventional vapor deposition apparatus without damaging a substrate by heat, has good productivity, and has excellent durability.

[0009]

In order to achieve the above object, a beam splitter according to a first aspect of the present invention comprises a substrate made of glass or resin, and a first dielectric of silicon oxide formed on the substrate. A thin film layer, and MoO ₃ and WO ₃ formed on the first dielectric thin film layer by a PVD method.
And a second dielectric thin film layer including at least one of the following.

The beam splitter according to a second aspect of the present invention is the beam splitter according to the first aspect, wherein the outermost layer of the dielectric thin film layer including the first dielectric thin film layer and the second dielectric thin film layer is This is a layer having a water-repellent effect.

[0011]

In other words, the beam splitter of the first invention uses a silicon oxide layer as the first dielectric thin film layer on the glass or resin substrate, so that it is particularly resistant to heat cycles and does not cause cracks. can do. The second dielectric thin film layer on the first dielectric thin film layer is
Since the layer contains at least one of MoO ₃ and WO ₃ formed by the VD method, it can be easily evaporated with low energy, and does not damage the substrate due to heat. In the beam splitter of the second invention, since the outermost layer of the dielectric thin film layer has a water-repellent effect, the adhesion and the optical characteristics are not deteriorated even under extremely high humidity.

[0012]

Embodiment 1 First, before describing a specific embodiment of the present invention, an outline of the present invention will be described. MoO ₃ and WO
₃ is a material that can be easily evaporated with low energy and can suppress the radiation heat from the evaporation source to a low level, so that the substrate is not damaged by heat.
Further, it is less susceptible to damage than CeO ₂ and ZnS described in the prior art, and has relatively high moisture resistance. Further, if the film is formed in a completely oxidized state, there is no absorption of visible light, and its refractive index is about 1.85 to 2.1 (depending on the film forming conditions). Therefore, a beam splitter can be formed by using MoO ₃ and WO ₃ as high refractive index substances.

The first layer from the substrate is a silicon oxide layer, and at least one of the dielectric thin film layers is PVD.
₃ or W formed by the physical vapor deposition method
By configuring the beam splitter so as to be a layer containing at least one of O ₃ , cracks can be prevented from being particularly strong in a heat cycle. This is because the first silicon oxide layer has an effect of reducing stress applied to the film due to expansion or contraction of the substrate. This effect will be specifically described in a sixth embodiment.

Further, by configuring the beam splitter so that the outermost layer of the thin film layer is a layer having a water repellent effect, adhesion and optical characteristics are not deteriorated even under extremely high humidity, And a beam splitter excellent in quality.

Here, the substrate includes not only glass but also synthetic resin such as acrylic, polycarbonate, amorphous polyolefin, CR-39, and energy curable resin. In addition, a PVD method such as a vacuum evaporation method or a sputtering method can be used for forming the film.

The layer having the water repellent effect can be formed by evaporating only an oil component from a porous material impregnated with a fluorine-based silicone oil, and using a fluorine resin-based target or fluorine gas. Fluorine-containing polymer film obtained by the above method, for example, PTFE, polyfluoroalkyl methacrylate, polytrifluoroethylene, perfluoroalkylsilane polymer, perfluoroalkylacetylene polymer, etc. The method is not limited as long as a film having a sufficient water repellency and durability can be obtained. Further, the thickness of the layer is set to such a level as to perform the function of the optical film (for example, 100 nm).
The thickness may be as thick as possible, or may be such that it does not affect optically (about 10 nm to 1 nm).

Next, a specific embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In this embodiment, a semi-transmissive film 2 is provided on the surface of a plastic substrate 1 made of an amorphous polyolefin resin having a refractive index of n = 1.52 to constitute a beam splitter called a semi-transmissive mirror. The semi-permeable film 2 is made of Si
O ₂ and WO ₃ were alternately formed by laminating 13 layers, and the film configuration was as shown in Table 1.

[0018]

[Table 1]

FIG. 2 is a schematic configuration diagram showing a vacuum evaporation apparatus for forming the semi-transmissive film 2 having the above configuration. Reference numeral 10 denotes a vacuum chamber, and a resistance heating evaporation source 11 and an electron gun evaporation source 12 are provided at lower positions in the vacuum chamber 10, respectively. Reference numeral 13 denotes a melting boat for resistance heating attached to the resistance heating evaporation source 11, and reference numeral 14 denotes a hearth of an electron gun evaporation source.
At an upper position in the vacuum chamber 10, a rotating dome 15 that allows the substrate 1 to be mounted and is rotatable about an axis is provided. Reference numeral 16 denotes a vacuum exhaust pipe connected to a vacuum pump (not shown). The distance from the evaporation source to the substrate is about 520
mm. As can be seen from the above description, this device
There is no difference from a conventional apparatus for forming a semi-permeable film on a glass substrate.

Next, a method for forming the semi-transmissive film 2 on the substrate 1 based on the above-mentioned vacuum deposition apparatus will be described. The substrate 1 made of amorphous polyolefin is fixed to the rotating dome 15, and the inside of the vacuum chamber 10 is evacuated to 1 × 10 ⁻⁶ Torr using an oil diffusion pump. Each SiO ₂ layer was formed by putting SiO ₂ into granules and putting it in a hearth 14 and heating it with an electron gun. In addition, each WO ₃ layer contains a small amount (3 wt%) of Al _{2 in} WO _3.
A pellet formed by adding O ₃ was heated and evaporated by an electron gun, and was formed while introducing oxygen gas into the vacuum chamber 10 up to 1 × 10 ⁻⁵ Torr. In this case, _Al 2 _{O 3} is due to the low significant evaporation pressure as compared to WO _3, during WO ₃ film _Al 2 _{O 3} is absent. However, by adding Al ₂ O ₃ , effects of preventing cracking of the pellets, reducing electrification, and preventing splash can be obtained.

According to the beam splitter which is called a semi-transmissive mirror of this embodiment formed as described above, its reflectivity is almost 50% over the entire visible range as shown in FIG.
It had sufficient optical characteristics. Further, when an adhesion test was performed using a cellophane tape, it was confirmed that the semi-permeable membrane 2 did not peel off and had sufficient adhesion.

[0022]

[Embodiment 2] In this embodiment, a water repellent treatment layer is provided on the outermost surface of the beam splitter referred to as the semi-transmissive mirror of Embodiment 1 above.

[0023]

[Table 2]

The SiO ₂ layer and the WO ₂ layer were formed in the same manner as in Example 1, and the water-repellent layer was formed by placing a porous material impregnated with a fluorine-based silicone oil in a melting boat 13 for resistance heating. And heated to evaporate only the impregnated oil component. The film thickness is the optical film thickness n
Although d is about 3 nm, which does not affect the optical characteristics at all, the wetting angle of water is 97 °, and has a sufficient water repellent effect.

The thus-formed beam splitter of this example was confirmed to have sufficient adhesion without peeling off the film by an adhesion test using a cellophane tape. Furthermore, temperature 45 ° C, humidity 95%
After the film was left for 300 hours in the above environment, the adhesion and optical characteristics of the film were examined. As a result, there was no change compared to before the film was left, and it was confirmed that the film had sufficient moisture resistance.

For comparison, the sample of Example 1 without the outermost water-repellent layer was left in an environment of a temperature of 45 ° C. and a humidity of 95% for 300 hours and then subjected to an adhesion test using a tape. The permeable membrane has peeled off. Therefore, it is understood that the moisture resistance is improved by providing the water-repellent treatment layer on the outermost surface as in this example.

[0027]

Third Embodiment FIG. 4 is a configuration diagram showing a third embodiment of the present invention. In the present embodiment, the beam splitter shown in FIG. That is, a triangular prism 3 made of BK optical glass having a refractive index of n = 1.52 is used as a substrate, and an SiO ₂ layer and a WO ₃ layer are alternately formed on the surface of the prism 3 by the same method as in the first embodiment. 1 in
After the film 4 was formed by laminating three layers, a triangular prism 5 made of the same material was bonded on the outermost layer of the film 4. As the adhesive, an ultraviolet-curable adhesive having a viscosity of 300 cps was used, and joined at a thickness of 10 μm.

[0028]

[Table 3]

The beam splitter of this embodiment has optical characteristics as shown in FIG. In the figure,
R _s is the reflectance of S-polarized light wave, R _p denotes reflectance of P-polarized light wave.

[0030]

Embodiment 4 The beam splitter of this embodiment has the film configuration shown in Table 4. That is, an acrylic resin (PMMA) prism is used as the substrate, and the first surface is formed on the surface thereof.
An Ag layer is formed as a layer, a WO ₃ layer is formed as a second layer on the Ag layer, and another PM layer is formed on the WO ₃ layer.
A prism made of MA was joined. The Ag layer is made of Ag
A material obtained by cutting the manufactured wire was formed by resistance heating method put in a tungsten boat, WO ₃ layer Example 1
A film was formed in the same manner as described above. In addition, an ultraviolet curable adhesive having a viscosity of 300 cps was used as the adhesive, and was bonded to a thickness of 10 μm.

[0031]

[Table 4]

The beam splitter of this embodiment has optical characteristics as shown in FIG. In the figure,
Ts is the transmittance of S-polarized light wave, T _p represents the transmittance <br/> of P-polarized light wave. In this example, a PMMA resin, which is particularly vulnerable to heat, was used for the substrate, but no deterioration in surface accuracy or other heat damage occurred on the substrate.

[0033]

Embodiment 5 The beam splitter of this embodiment has the film configuration shown in Table 5 . That is, the refractive index n as a substrate
= 1.52, _three layers of WO, an Ag layer, and a layer of ZrO ₂ + TiO ₂ are sequentially laminated on a prism made of BK-based optical glass, and then another layer is formed on the ZrO ₂ + TiO ₂ layer. Prisms made of the same glass material were joined together. As the adhesive, a silicone-based condensation-type adhesive having a viscosity of 300 cps was used, and joined at a thickness of 10 μm.

[0034]

[Table 5]

The WO ₃ layer uses a WO ₃ target, and the ZrO ₂ + TiO ₂ layer uses as a target a mixture of ZrO ₂ and TiO ₂ mixed at a weight ratio of 9: 1 and sintered. In both the WO ₃ layer and the ZrO ₂ + TiO ₂ layer, Ar gas and O ₂ gas are combined to form a vacuum chamber 10.
The film was formed by an RF magnetron sputtering method while introducing the film to 7 × 10 ⁻² Torr. The Ag layer is formed by using an Ag target while introducing Ar gas into the vacuum chamber 10 up to 2 × 10 ⁻² Torr.
The film was formed by a magnetron sputtering method. The beam splitter of the present embodiment configured as described above has a structure shown in FIG.
The optical characteristics as shown in FIG.

[0036]

[Embodiment 6] The beam splitter of this embodiment had the film configuration shown in Table 6. That is, a prism made of an amorphous polyolefin resin is used as a substrate, an SiO ₂ layer is formed as a first layer from the prism side on the prism, and a WO ₃ layer, an Ag layer, and a WO ₃ layer are formed on the SiO ₂ layer.
Layer and an SiO ₂ layer are sequentially formed into five layers, and the outermost layer Si
Another prism made of the same material was joined on the O ₂ layer.

[0037]

[Table 6]

The beam splitter of this embodiment had optical characteristics as shown in FIG. Further, regarding the beam splitter of the present embodiment, -40 ° C. for 1 hour → 20 ° C. 3
A heat cycle test was performed for 30 cycles in which 0 minute → 80 ° C. for 1 hour → 20 ° C. for 30 minutes, but no problems such as cracks and peeling occurred.

For comparison, Table 7 shows the results of the same heat cycle test as described above, except that the thickness of the first layer of SiO ₂ was changed.

[0040]

[Table 7]

According to this, the thickness of the SiO ₂ layer is 2 nm.
It was found that the above film formation had an effect of preventing cracks, and a remarkable effect was recognized by setting the thickness of the SiO ₂ layer to 5 nm or more. This is the same result in the case of another film configuration. Similar effects were obtained by using a SiO _x (x = 1 to 2) layer instead of the SiO ₂ layer of this embodiment.

[0042]

[Embodiment 7] The beam splitter of this embodiment has the film configuration shown in Table 8. That is, SiO 2 is placed on a polycarbonate (PC) prism from the prism side.
_{An X} (x = 1 to 2) layer, a MoO ₃ layer, an Ag layer, and a MoO ₃ layer were sequentially formed, and an amorphous polyolefin prism was bonded to the outermost layer of MoO ₃ .

[0043]

[Table 8]

The beam splitter of this example had the optical characteristics shown in FIG. 9 and also had good heat cycle resistance.

[0045]

[Embodiment 8] The beam splitter of this embodiment was formed so as to have a film configuration shown in Table 9 and to have a transmittance of 20%. In other words, amorphous poly
Using a fin resin prism, WO ₃
Layer, Ag layer, after sequentially forming a third layer of WO ₃ layer was formed by joining the prisms of the same material as the outermost layer of WO ₃ layer on.

[0046]

[Table 9]

FIG. 10 shows a beam splitter according to this embodiment.
As shown in the figure, both the S-polarized wave and the P-polarized wave had optical characteristics such that a transmittance of about 20% was obtained.

[0048]

Embodiment 9 The beam splitter of this embodiment is shown in Table 10.
The semi-permeable membrane was constituted by the membrane constitution shown in (1). That is, a semi-transmissive film is formed by alternately stacking 13 layers of SiO ₂ layers and MoO ₃ layers from the plastic substrate side on the surface of a plastic substrate made of an amorphous polyolefin resin having a refractive index of n = 1.52, Further, a water-repellent treatment layer was provided on the outermost SiO ₂ layer. The water-repellent layer and the method of forming the same were the same as those in Example 2.

[0049]

[Table 10]

The beam splitter of this embodiment is similar to that of FIG.
The optical characteristics as shown in FIG. Further, the film was not peeled off by an adhesion test using a cellophane tape, and it was confirmed that the film had sufficient adhesion. Furthermore, the film was left to stand in an environment of a temperature of 45 ° C. and a humidity of 95% for 300 hours, and the adhesion and the optical characteristics of the film were examined. confirmed. As described above, according to the beam splitter of each embodiment, MoO ₃ or WO ₃ formed by the PVD method is used as the high refractive index layer, so that the substrate is made of glass or resin. It has high adhesion, does not degrade the cottoniness of the substrate, and does not damage the substrate due to heat. Therefore, a film can be easily formed using a conventional apparatus, and the productivity can be improved. In addition, a beam splitter having particularly high heat cycle resistance can be obtained by using a silicon oxide having an optical thickness of 2 nm or more as the first layer from the substrate. Further, by making the outermost layer of the thin film layer a layer having a water-repellent effect, a beam splitter having particularly high moisture resistance can be obtained.

[0051]

As described above, according to the present invention, the first dielectric thin film layer on the glass or resin substrate is formed as a silicon oxide layer, and the second dielectric thin film on the first dielectric thin film layer is formed. Since the thin film layer is a layer containing at least one of MoO ₃ and WO ₃ formed by a PVD method, regardless of whether the substrate is glass or resin, the adhesion is high, and the cotton production of the substrate is not deteriorated. Further, a beam splitter that does not damage the substrate due to heat can be provided. Further, according to the present invention, since a silicon oxide is used for the first dielectric thin film layer, a beam splitter having particularly high heat cycle resistance can be obtained. Further, according to the arm invention, a beam splitter having particularly high moisture resistance can be obtained by using the outermost layer of the thin film layer as a layer having a water-repellent effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a vacuum evaporation apparatus used for film formation in each embodiment of the present invention.

FIG. 3 is a graph showing optical characteristics of Example 1 of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a graph showing optical characteristics of Example 3 of the present invention.

FIG. 6 is a graph showing optical characteristics of Example 4 of the present invention.

FIG. 7 is a graph showing optical characteristics of Example 5 of the present invention.

FIG. 8 is a graph showing optical characteristics of Example 6 of the present invention.

FIG. 9 is a graph showing optical characteristics of Example 7 of the present invention.

FIG. 10 is a graph showing optical characteristics of Example 8 of the present invention.

FIG. 11 is a graph showing optical characteristics of Example 9 of the present invention.

[Explanation of symbols]

 Reference Signs List 1 plastic substrate 2 semi-transmissive film 3,5 prism 4 film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 5/08

Claims (2)

(57) [Claims] 1. A substrate made of glass or resin, a first dielectric thin film layer of silicon oxide formed on the substrate, and an M layer formed on the first dielectric thin film layer by a PVD method.
a second dielectric thin film layer containing at least one of oO ₃ and WO ₃ . 2. The device according to claim 1, wherein the outermost layer of the dielectric thin film layer including the first dielectric thin film layer and the second dielectric thin film layer is a layer having a water-repellent effect. Beam splitter.