JP4792871B2 - Optical reflection member - Google Patents

Description

  The present invention relates to an optical reflecting member, and more particularly to an optical reflecting member provided with a reflecting layer containing Ag as a main component.

  In optical devices such as cameras and projectors, many optical reflecting members are used on the optical path. In these optical devices, since it is necessary to increase the reflectance in order to obtain a bright image, Ag has been widely used as a material for the reflective layer in optical reflecting members used in these optical devices.

  However, the reflective layer containing Ag as a main component has a high reflectivity of 98% in the entire visible light region, but has a problem of poor adhesion and durability to the substrate. In addition, in recent years, plastic members have been widely used in optical instruments in place of glass members. However, when a plastic member is used as a substrate on which a reflective layer is formed, the above problem appears more remarkably.

Therefore, an adhesion layer is formed between the substrate and the reflective layer, and five or more dielectric layers are formed on the reflective layer to prevent the intrusion of moisture, sulfur, and the like, which cause the above problem, into the reflective layer. The technique which performs is proposed (for example, patent document 1).
JP 2004-184703 A (Claims, FIG. 1)

  According to the proposed technique, although the adhesion and durability of the reflective layer to the substrate are improved, a large number of dielectric layers must be formed and productivity is low.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an optical reflecting member in which a reflecting layer mainly composed of Ag is formed on a plastic substrate, and to improve the adhesion and durability of the reflecting layer. The goal is to increase the productivity further.

  Another object of the present invention is to provide an imaging apparatus and a projection apparatus that can capture and project a clear image over a long period of time.

  According to the present invention, an optical reflection formed by forming, on the surface of a plastic substrate, in order from the substrate side, an adhesion layer, a reflective layer mainly composed of Ag, and a protective layer composed of three or more light-transmitting dielectric layers. An optical reflecting member is provided, wherein the outermost layer of the protective layer is a mixture layer of aluminum oxide and lanthanum oxide.

  Here, from the viewpoint of further preventing the entry of sulfur or the like into the reflective layer, the mixing ratio of lanthanum oxide in the mixture layer is preferably 40 mol% or more.

  Also, from the viewpoint of improving the productivity of the optical reflecting member without reducing the adhesion and durability of the reflective layer to the substrate, the protective layer is composed of three layers, and the aluminum oxide layer and the silicon oxide layer are sequentially formed from the substrate side. Alternatively, a mixed layer of silicon oxide and aluminum oxide, or a mixed layer of aluminum oxide and lanthanum oxide is preferable.

  From the viewpoint of further improving the adhesion and durability of the reflective layer to the substrate, the thickness of the aluminum oxide layer is 5 to 45 nm, the thickness of the silicon oxide layer or the mixture layer of silicon oxide and aluminum oxide is 10 to 100 nm, and the oxidation The layer thickness of the mixture layer of aluminum and lanthanum oxide is preferably 15 to 110 nm.

  Similarly, from the viewpoint of improving the adhesion and durability of the reflective layer to the substrate, any one of a titanium oxide layer, a mixture layer of lanthanum oxide and aluminum oxide, and a mixture layer of lanthanum oxide and titanium oxide is used as the adhesion layer. Is preferably used, and the thickness of the adhesion layer is preferably in the range of 15 to 175 nm.

  In addition, according to the present invention, there is provided an imaging apparatus and a projection apparatus using the optical reflecting member.

  In the optical reflecting member according to the present invention, an adhesive layer, a reflective layer mainly composed of Ag, and a protective layer composed of three or more light-transmitting dielectric layers are formed in this order from the substrate side, and the outermost layer of this protective layer Is a mixture layer of aluminum oxide and lanthanum oxide, so that the adhesion between the reflective layer and the substrate is high, and even when a plastic material is used as the substrate, peeling of the reflective layer can be effectively prevented. Moreover, high durability is obtained. Furthermore, since the reflective layer can be protected with a smaller number of layers than in the prior art, productivity is improved. In addition, even when a layer is formed by vapor deposition on a bent or curved substrate such as a pentamirror or a curved reflecting mirror, each layer is firmly attached.

  When the mixing ratio of lanthanum oxide in the mixture layer is 40 mol% or more, it is possible to further prevent the entry of sulfur or the like into the reflective layer.

  Further, when the protective layer is composed of three layers, and in order from the substrate side, an aluminum oxide layer, a silicon oxide layer, a mixed layer of silicon oxide and aluminum oxide, or a mixed layer of aluminum oxide and lanthanum oxide, the reflective layer adheres to the substrate. And productivity of an optical reflection member can be improved, without reducing durability.

  From the viewpoint of further improving the adhesion and durability of the reflective layer to the substrate, the thickness of the aluminum oxide layer is 5 to 45 nm, the thickness of the silicon oxide layer or the mixture layer of silicon oxide and aluminum oxide is 10 to 100 nm, and the oxidation The layer thickness of the mixture layer of aluminum and lanthanum oxide is preferably 15 to 110 nm.

  When any one of a titanium oxide layer, a mixture layer of lanthanum oxide and aluminum oxide, or a mixture layer of lanthanum oxide and titanium oxide is used as the adhesion layer, the adhesion and durability of the reflective layer to the substrate are improved. When the thickness of the adhesion layer is in the range of 15 to 175 nm, the adhesion and durability of the reflective layer to the substrate are similarly improved.

  Further, since the optical reflecting member is used in the imaging apparatus and the projection apparatus according to the present invention, a clear image can be taken and projected over a long period of time.

  One embodiment of an optical reflecting member according to the present invention is shown in FIG. 1 has a titanium oxide layer as an adhesion layer, a reflective layer made of Ag, and three light-transmitting dielectric layers as a protective layer, that is, an aluminum oxide layer and a silicon oxide layer, on the surface of a plastic substrate. (A mixture layer of aluminum oxide and lanthanum oxide) is formed in this order from the substrate side.

  In the optical reflecting member of the present invention, it is important that the outermost layer of the protective layer is a mixture layer of aluminum oxide and lanthanum oxide. This is based on the knowledge obtained from the following experimental results conducted by the present inventors. In the optical reflecting member having the layer configuration shown in FIG. 2, the outermost layer (consideration material 1) of the protective layer was changed in various ways and an evaluation test was performed. The results are shown in Table 1.

  In addition, each evaluation item was performed as follows. First, “time-dependent change” is determined by visual observation of the reflective layer of the optical reflecting member for cracks, discoloration, and pinholes after being left in the room for 960 hours (40 days). The determination criteria are as shown in Table 2. In the “cold thermal shock test”, the sample is left for 1 hour in an environment at −30 ° C. and then left for 1 hour in an environment at + 70 ° C. After 10 cycles, the optical reflection is performed in the same manner as described above. The surface of the member is determined visually. Next, the same test is performed by changing the temperature to −40 ° C. and + 85 ° C., and the surface of the optical reflecting member is visually determined. “Sulfur” is obtained by placing 1 kg of corrugated cardboard (containing sulfur) and an optical reflecting member in a desiccator and leaving it in a bath at 80 ° C. for 168 h, and then visually observing the surface of the optical reflecting member. “70 ° C. × 80% 500 h” is obtained by visually observing the surface of the optical reflecting member after being left for 500 hours in an environment of a temperature of 70 ° C. and a humidity of 80%. “60 ° C. × 5% 600 h” is obtained by visually observing the surface of the optical reflecting member after being left for 600 h in an environment of a temperature of 60 ° C. and a humidity of 5%. Then, the above evaluation items were combined to determine whether or not practical use was possible.

Further, in the experiment, each layer of the optical reflecting member was formed on a polycarbonate substrate by using a vacuum vapor deposition apparatus for the optical reflecting members of Experiment Nos. 1 to 11. The degree of vacuum was about 1 × 10 ⁻² Pa, and the layer thickness was measured by a multiple reflection interferometry with an optical film thickness meter. Further, the optical reflection members of Experiment Nos. 12 to 16 were deposited by an IAD (Ion Assist Deposition) method in order to increase the density of each layer.

As is clear from Table 1, only when a mixture layer of aluminum oxide and lanthanum oxide was used as the outermost layer of the protective layer, it was practically usable. In addition, even when the material is deposited by the IAD method in which the material is more densely attached (experiment numbers 12 to 16), when the outermost layer is other than the mixed layer of (Al ₂ O ₃ + La ₂ O ₃ ), an environmental test is performed. However, it was not durable.

Here, the mixing ratio of La ₂ O ₃ in the mixed layer of Al ₂ O ₃ and La ₂ O ₃ is preferably 40 mol% or more. When the mixing ratio of La ₂ O ₃ is less than 40 mol%, the evaluation result in the sulfur test or the thermal shock test may not be good. The reason for this has not been fully elucidated so far, but La ₂ O ₃ has deliquescence and absorbs water vapor in the air, so one of the causative substances for Ag layer degradation is water-soluble sulfide. It is presumed that La ₂ O ₃ dissolves in the absorbed water and prevents the entry of sulfide into the Ag layer.

Next, as shown in FIG. 3, when a layer is further formed on the mixed layer of Al ₂ O ₃ and La ₂ O ₃ (experiment numbers 17 to 19), as shown in Table 3 below, “sulfur” Cracks, discoloration, and pinholes occurred in the reflective layer during the test and the environmental test of temperature and humidity. From this, it can be seen that a mixed layer of Al ₂ O ₃ and La ₂ O ₃ is preferably the outermost layer of the protective layer as in Experiment No. 1.

In the optical reflecting member of the present invention, the protective layer is composed of three or more translucent dielectric layers. The configuration of the invention is based on the following experimental results. That is, in the optical reflecting member shown in FIG. 1, the third layer and the fourth layer are not formed, but the fifth mixed layer of Al ₂ O ₃ and La ₂ O ₃ is formed on the second Ag layer. The layer thickness of the mixed layer was doubled and halved in the same manner as described above (experiment numbers 20 to 22). In addition, the third layer was not formed and the fourth layer was a mixed layer of SiO ₂ and Al ₂ O ₃ (experiment number 23). The evaluation results are shown in Table 4.

As can be seen from Table 4, when one mixed layer of Al ₂ O ₃ and La ₂ O ₃ is formed as a protective layer on the Ag layer, the layer thickness can be doubled and halved. In an environmental test of “60 ° C. × 5% 500 h”, cracks, discoloration, and pinholes were generated in the reflective layer of the optical reflecting member, which was not practical. When _two layers of a mixed layer of SiO ₂ and Al ₂ O _{3 and} a mixed layer of Al ₂ O ₃ and La ₂ O ₃ are formed on the Ag layer as a protective layer, a thermal shock test, a sulfur test, an environment In the test, cracks, discoloration, and pinholes were generated in the reflective layer of the optical reflecting member, which was not practical.

In the above experiment, no experiment was conducted for the case where there were four or more protective layers, but three or more transparent layers were interposed between the outermost Al ₂ O ₃ and La ₂ O ₃ mixed layer and the Ag layer. Of course, it is possible to provide four or more protective layers by providing an optical dielectric layer. In this case, it is desirable that light-transmitting dielectric layers having a high refractive index and a low refractive index are alternately stacked.

Moreover, as shown in Table 5, in the layer structure of the optical reflecting member shown in FIG. 1, no trouble occurred even when the fourth SiO ₂ layer was replaced with a mixed layer of SiO ₂ and Al ₂ O ₃ ( Experiment number 24).

Next, the result of having examined each layer thickness of the protective layer shown in FIG. 1 is shown. Table 6 shows the results of evaluation by changing the layer thickness of the _third layer (Al ₂ O ₃ layer) in the optical reflecting member of FIG. The layer thickness of the third layer (Al ₂ O ₃ layer) of the optical reflecting member is changed to 1/3 (4.8 nm) and 3 times (43.4 nm) of the layer thickness (14.5 nm) of Experiment No. 1. As a result, in any layer thickness, the formed optical reflecting member had no problem in practical use. This indicates that the thickness of the third layer (Al ₂ O ₃ layer) is preferably in the range of at least 5 to 45 nm.

Next, evaluation was performed by changing the thickness of the fourth layer in the optical reflecting member of FIG. Table 7 shows the evaluation results. As described above, the material of the fourth layer may be either a SiO ₂ layer or a mixed layer of SiO ₂ and Al ₂ O ₃ (see Table 5 and Experiment No. 24). A mixed layer of SiO ₂ and Al ₂ O ₃ is used as the material for the optical reflection member, and the layer thickness of the fourth layer of the optical reflecting member is 1/3 times (10.6 nm) of the layer thickness (31.9 nm) of Experiment No. 1. Evaluation was performed by changing the magnification by 3 times (95.8 nm).

As is clear from Table 7, the formed optical reflecting member has no problem in practical use when the mixed layer thickness of SiO ₂ and Al ₂ O ₃ is 10.6 nm and 95.8 nm. there were. This indicates that the thickness of the fourth layer is preferably in the range of at least 10 to 100 nm.

Subsequently, the thickness of the fifth layer (mixed layer of Al ₂ O ₃ and La ₂ O ₃ ) in the optical reflecting member of FIG. 1 was changed and evaluated. Specifically, the layer thickness of the fifth layer (mixed layer of Al ₂ O ₃ and La ₂ O ₃ ) of the optical reflecting member is 1/3 times (17.8 nm) the layer thickness (53.3 nm) of Experiment No. 1. ) And 2 times (106.7 nm). The evaluation results are shown in Table 8.

As is clear from Table 8, the optical reflecting member formed was free from problems in practical use at any layer thickness. This shows that the thickness of the fifth layer (mixed layer of Al ₂ O ₃ and La ₂ O ₃ ) is preferably in the range of at least 15 to 110 nm.

  Next, the material and the layer thickness of the adhesive layer (first layer) in the optical reflecting member having the layer structure shown in FIG. 4 were examined. First, Table 9 shows the results of evaluation tests performed by changing the material of the adhesion layer (examination material 3) in various ways.

As understood from Table 9, as the material of the adhesion layer, in addition to Ti ₃ O ₅ , a mixture of Al ₂ O ₃ and La ₂ O _3, a mixture of TiO ₂ and La ₂ O ₃ , Ta ₂ O ₅ and TiO Whichever mixture of ₂ was used, the formed optical reflecting member had no problem in practical use.

Next, a mixture of Al ₂ O ₃ and La ₂ O ₃ is used as the material for the adhesion layer, and the layer thickness (56.9 nm, optical film thickness: 0.25) is used as a reference, and 1/3 times (18.9 nm). ) And 3 times (170.7 nm), and the layer thickness was changed for evaluation. The evaluation results are shown in FIG.

  As is apparent from Table 10, the optical reflecting member formed was free from problems in practical use in any layer thickness. This indicates that the layer thickness of the adhesion layer (first layer) is preferably in the range of at least 15 to 175 nm.

  Next, the influence of the shape of the plastic substrate used in the present invention on the durability and environmental resistance of the film was examined. That is, when the substrate shape is flat, the vapor deposition material collides perpendicularly to the substrate surface during vapor deposition, but when the substrate shape is bent or curved, the vapor deposition material is predetermined from the direction perpendicular to the substrate surface. This is because it is known that the collision energy is dispersed because the collision occurs at an angle, and the layer strength is weaker in the case of the latter shape than the former. In this experiment, the layers shown in FIG. 5 were laminated on a planar substrate and a roof substrate, and the same evaluation as described above was performed. The results are shown in Table 11.

  As can be seen from Table 11, according to the layer configuration defined in the present invention, the durability and environmental resistance equivalent to those of the planar substrate were obtained even with the roof substrate.

  In the embodiment described above, the optical reflecting member according to the present invention is manufactured by the vacuum vapor deposition method. However, the present invention is not limited to such an embodiment. For example, the sputtering method, the ion plating method, the PCVD, and the like. Of course, it does not matter even if it manufactures by etc. As the plastic substrate used in the present invention, conventionally known plastic materials such as polycarbonate and acrylic resin can be used. Therefore, the optical reflecting member according to the present invention can be used as a roof pentamirror used for a single-lens reflex camera or a curved reflecting mirror used for a projector.

  FIG. 6 shows a schematic configuration diagram of a single-lens reflex camera (photographing apparatus) using the optical reflecting member of the present invention as a roof pentamirror. The single-lens reflex camera C shown in FIG. 6 is provided with a focusing plate 3 that extends horizontally above the quick return mirror 2, and the subject image formed on the focusing screen 3 is connected to the viewfinder as upper, lower, left, and right images. A roof pentamirror 1 is provided so that it can be observed from the eye part 4. Conventionally, a pentaprism was used to observe the subject image as a vertical and horizontal image. However, since the pentaprism mirror is heavy, it has recently been replaced with a pentaprism mirror in response to market demands for lighter cameras. The pentamirror 1 has been widely used.

  The roof pentamirror 1 includes a plastic shell-like base body 11. The base body 11 is formed as one member 11b by separating the front wall portion on which the plane mirror 13 is formed from other portions, and the remaining portion is formed. It is formed as another member 11a, and these two members 11a and 11b are joined and integrated. Since the roof pentamirror 1 corresponds to the configuration of a conventional pentaprism mirror, the roof mirror 12 that reflects incident light from the focusing screen 3 and the light reflected by the roof mirror 12 are further reflected to finder eyepiece 4. And a plane mirror 13 leading to The roof mirror 12 is formed on a pair of inward planes of the member 11a that intersect at right angles. On the other hand, the plane mirror 13 is formed on the surface of the member 11b. By joining the members 11a and 11b, the roof mirror 12 and the flat mirror 13 are positioned inside the shell-like base 11, and the subject image formed on the focusing screen 3 is the roof pentamirror 1. Is guided to the viewfinder eyepiece 4 as a vertical and horizontal right and left image. With the layer structure defined in the present invention, even if the substrate 11 is bent at a right angle, each layer is firmly deposited and is excellent in durability and environmental resistance. The roof pentamirror 1 can be suitably used.

  The optical reflecting member according to the present invention can also be used as a curved reflecting mirror used in a projector. FIG. 7 shows a schematic configuration diagram of a rear projection optical system in a rear projection type image projection apparatus (rear projector) using the optical reflecting member of the present invention as a curved reflecting mirror.

  The rear projector optical system of FIG. 7 uses the image display surface of the display panel as a panel display surface (I1) on the reduction side, and enlarges and projects a two-dimensional image of the panel display surface (I1) on a screen surface (not shown). A projection optical system is provided. As the display panel, for example, a display element such as a reflective liquid crystal panel, a transmissive liquid crystal panel, or a DMD (Digital Micromirror Device) is used. The panel display surface (I1) is illuminated with illumination light emitted from a lamp (not shown) and then passed through an illumination optical system (not shown). The projection light emitted from the panel display surface (I1) by the illumination is guided to a screen surface (not shown) by a projection optical system or the like. In the case of colorizing the projected image, a three-plate configuration that uses three display panels to combine colors using a cross dichroic prism, a single-plate configuration that displays images in a time-division manner, or a microlens on the display panel A single plate configuration using an array may be employed.

  The projection optical system shown in FIG. 7 includes first to third mirrors (M1 to M3) in order from the panel display surface (I1) side. Note that the aperture position (ST) in the figure corresponds to the virtual aperture surface. The first to third mirrors (M1 to M3) are all curved reflecting mirrors, and their reflecting surfaces are all free curved surfaces. The projection light emitted from the panel display surface (I1) is reflected by the three curved reflecting mirrors constituting the projection optical system, and then the optical path is refracted twice by the planar reflecting mirror (not shown). To reach the screen surface.

  In this embodiment, the projector has a heating element called a light source unit, and each optical component not only transmits and reflects light but also absorbs light slightly, so that its temperature rises after the lamp is turned on. . Since the environmental temperature is not constant, it is desirable that the rear projection optical system has a stable and good performance against temperature changes. Further, it is generally known that the error sensitivity of a reflective optical component such as a reflection mirror is more than twice as high as that of a normal transmissive optical component. Therefore, glass having a relatively small variation with respect to temperature change has been widely used as a substrate for a curved reflecting mirror. However, the curved reflection mirror closest to the screen surface among these curved reflection mirrors has a low error sensitivity because of its relatively weak optical power. Therefore, for this curved reflecting mirror, a plastic material such as PMMA (polymethyl methacrylate), PC (polycarbonate) or polyolefin resin can be used as the substrate. Therefore, when the optical reflecting member according to the present invention is used as these curved reflecting mirrors, it is possible to obtain an effect of reducing the weight and cost of the apparatus by changing the substrate from glass to plastic, and having excellent durability and environmental resistance. It will be obtained.

It is a schematic diagram which shows an example of the optical reflection member which concerns on this invention. It is a figure which shows the layer structure in experiment. It is a figure which shows the layer structure in experiment. It is a figure which shows the layer structure in experiment. It is a figure which shows the layer structure in experiment. It is a schematic diagram of the single-lens reflex camera using the optical reflection member of this invention. It is a schematic diagram of the projector using the optical reflection member of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roof pentamirror 11 Base | substrate 12 Dach mirror 13 Plane mirror I1 Panel display surface M1-M3 1st-3rd mirror (curved reflective mirror)

Claims (8)

An optical reflecting member in which an adhesive layer, a reflective layer mainly composed of Ag, and a protective layer composed of three or more translucent dielectric layers are formed on the surface of the plastic substrate in this order from the substrate side,
The optical reflecting member, wherein the outermost layer of the protective layer is a mixture layer of aluminum oxide and lanthanum oxide.   The optical reflecting member according to claim 1, wherein a mixing ratio of lanthanum oxide in the mixture layer is 40 mol% or more.   3. The optical reflection according to claim 1, wherein the protective layer is composed of three layers, which are an aluminum oxide layer, a silicon oxide layer, a mixture layer of silicon oxide and aluminum oxide, or a mixture layer of aluminum oxide and lanthanum oxide in order from the substrate side. Element.   The layer thickness of the aluminum oxide layer is 5 to 45 nm, the layer thickness of the silicon oxide layer or the mixture layer of silicon oxide and aluminum oxide is 10 to 100 nm, and the layer thickness of the mixture layer of aluminum oxide and lanthanum oxide is 15 to 110 nm. 3. The optical reflecting member according to 3.   The optical reflection member according to any one of claims 1 to 4, wherein the adhesion layer is any one of a titanium oxide layer, a mixture layer of lanthanum oxide and aluminum oxide, and a mixture layer of lanthanum oxide and titanium oxide.   The optical reflection member according to claim 1, wherein the adhesion layer has a thickness of 15 to 175 nm.   An image pickup apparatus using the optical reflecting member according to claim 1.   A projection apparatus using the optical reflecting member according to claim 1.

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