JP2004145305A - Polarization conversion element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization conversion element with improved heat resistance and weather resistance and to provide its manufacturing method. <P>SOLUTION: In the polarization conversion element, a polarization separation film 8 which transmits P-waves and reflects S-waves in the P-waves and S-waves is formed on an inclined end face 11 of a first light transmitting base material 10. A reflective film 9 is formed on an inclined end face 22 of a second light transmitting base material 20. A half-wave retardation film 30 consisting of a uniaxially stretched single-layer polycarbonate film is joined with a photosetting adhesive 4 between the inclined end face 11 of the first light transmitting base material 10 and the inclined end face 21 of the second light transmitting base material 20. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a polarization conversion element mounted on a liquid crystal projector, an optical pickup device, and the like, and a method for manufacturing the same.

The liquid crystal projector uses a polarization converter (a beam splitter and a λ / 2 retardation plate) to convert natural light emitted from a light source into an S wave (S) to efficiently transmit the light through the liquid crystal panel. (Polarized light) or P-wave (P-polarized light). Specifically, the beam splitter separates outgoing light into S-waves and P-waves, and only the P-wave passes through the λ / 2 retardation plate, whereby the polarization plane of the P-wave is twisted by 90 degrees. Converted to S-wave. Since the S wave and the S wave separated by the beam splitter reach the liquid crystal panel, natural light is efficiently used and the projector can reproduce a bright image. Here, in the conventional polarization conversion element, as shown in FIG. 9, a λ / 2 retardation plate 201 is attached to a light emission side surface of a beam splitter 500 via an adhesive 202 (for example, see Patent Reference 1).
JP-A-2-227901

In the polarization conversion element having such a configuration, since the λ / 2 retardation plate 501 is mounted so as to be exposed on the surface of the beam splitter 500, the λ / 2 retardation plate 501 is made of a polymer film. In the case of using, there is a problem that durability and weather resistance are extremely low. Further, since the λ / 2 retardation plate 501 and the beam splitter 500 are bonded with the adhesive 502, there is a problem that the durability of the adhesive 502 affects the overall durability. Moreover, it is very difficult to greatly improve the weather resistance and durability of the λ / 2 retardation plate 501 and the adhesive 502 made of a polymer. For this reason, the polarization conversion element, even though it is the device closest to the light source, could not improve the heat resistance and the like, and deprived the design freedom of the projector and the like.

In view of the above problems, an object of the present invention is to propose a polarization conversion element having improved heat resistance and weather resistance, and a method for manufacturing the same.

In order to solve the above problems, in the polarization conversion element according to the present invention, the first optical layer and the second optical layer are provided in a light-transmitting base material in which the inclined end faces of the plurality of light-transmitting members are joined. Are arranged parallel to each other and obliquely to the incident optical axis with respect to the light-transmitting substrate, wherein the first optical layer has a first light-transmitting member and a second light-transmitting member sandwiching the first optical layer on both sides. Out of the light-transmitting member, the polarization separation film formed on the inclined end surface of the first light-transmitting member, the inclined end surface of the first light-transmitting member on which the polarization separation film is formed, and And a λ / 2 retardation film (wave plate / retardation plate) bonded and fixed to the inclined end surface of the second light-transmitting member, wherein the second optical layer is a reflective film, The λ / 2 retardation film is characterized by being composed of a uniaxially stretched single-layer polymer film. That is, in the present invention, a λ / 2 retardation film made of a polymer film is sandwiched between light-transmitting substrates, and a single-layer polymer film as a λ / 2 retardation film, that is, uniaxially stretched. It is characterized in that a polymer film is used in a single layer.

According to the present invention, for example, after the incident light is separated into S-waves (S-polarized light) and P-waves (P-polarized light) by a polarization separation film formed on the interface of the first light-transmissive substrate. , S-wave, or P-wave only passes through the λ / 2 retardation film, and the plane of polarization is twisted by 90 degrees. As a result, it is possible to unify the plane of polarization when emitting the polarization conversion element. Further, in the present invention, since the λ / 2 retardation film was sandwiched and adhered to the translucent substrate, the λ / 2 retardation film was not exposed on the surface of the polarization conversion element on the emission light side, Not bonded with adhesive. Therefore, heat resistance and moisture resistance of the polarization conversion element are improved. Therefore, the thermal durability of a device close to the light source can be improved, so that the quietness of the liquid crystal projector (reduction of air noise by a fan) and the durability of the entire apparatus can be extended.

In the polarization conversion element according to another aspect of the present invention, the first optical layer and the second optical layer are parallel to each other in the light-transmitting base material in which the inclined end faces of the plurality of light-transmitting members are joined to each other. The first optical layer is disposed obliquely to an optical axis of incidence with respect to the light-transmitting substrate, the first optical layer is a polarization separation film, and the second optical layer sandwiches the second optical layer on both sides. Of the first light-transmitting member and the second light-transmitting member, the reflection film formed on the inclined end face of the second light-transmitting member and the reflection film of the second light-transmitting member are different. The λ / 4 retardation film, comprising a λ / 4 retardation film (wave plate / retardation plate) adhesively fixed between the formed inclined end face and the end face of the first light transmitting member. Is characterized by comprising a uniaxially stretched single-layer polymer film. That is, in the present invention, a λ / 4 retardation film made of a polymer film is sandwiched in a light-transmitting substrate, and a single-layer polymer film as a λ / 4 retardation film, that is, uniaxially stretched. It is characterized in that a polymer film is used in a single layer.

According to the present invention, the incident light is separated into an S-wave (S-polarized light) and a P-wave (P-polarized light) by the polarization separation film formed on the interface of the first light-transmitting substrate, and then the S-wave is separated. Only the light having one of the wave and the P wave passes through the λ / 4 retardation film, the polarization plane is twisted by 45 degrees, and reaches the reflection film formed on the interface of the second light-transmitting substrate. . The light totally reflected by this reflection film passes through the λ / 4 phase difference film again, and the polarization plane is twisted by 45 degrees. As a result, it is possible to unify the plane of polarization when emitting the polarization conversion element. Further, since the λ / 4 retardation film was sandwiched and adhered to the translucent base material, the λ / 4 retardation film was not exposed on the surface of the polarization conversion element on the emission light side, and was adhered with an adhesive. Not combined. As a result, heat resistance and moisture resistance of the polarization conversion element are improved.

In the present invention, in the light-transmitting substrate, the first light-transmitting member and the second light-transmitting member are arranged such that the first light-transmitting member and the second light-transmitting member are alternately arranged. The inclined end faces at both ends of the transparent member are joined to each other, and the first optical layer and the second optical layer are respectively connected to one inclined end face of the first light transmissive member and the second light transmissive member. A first joining interface between the one-side inclined end surface of the member and a second joining interface between the other-side inclined end surface of the first translucent member and the other-side inclined end surface of the second translucent member; It is configured.

に お い て In the present invention, the polymer film is made of, for example, polycarbonate.

In the present invention, it is preferable that the first optical layer and the second optical layer both form an angle of 45 degrees with respect to the incident optical axis. With this configuration, the optical axes of the incident light that enters the polarization conversion element and the emission light that passes through the polarization conversion element and exits can be made parallel.

に お い て In the present invention, it is preferable that the uniaxially stretched single-layer polymer film has a small wavelength dependence in a visible light region, or has a reverse dispersion characteristic having no wavelength dependence.

In the method for manufacturing a polarization conversion element to which the present invention is applied, the polarization separation film is formed on one of the parallel surfaces of the first light-transmitting substrate, while the parallel surfaces of the second light-transmitting substrate are formed. A reflection film is formed on one surface of the first light-transmitting substrate, and one surface of the first light-transmitting substrate on which the polarization separation film is formed, and the reflection film of the second light-transmitting substrate. The surface opposite to the side on which is formed is bonded via a photocurable adhesive, a λ / 2 retardation film composed of a uniaxially stretched single-layer polymer film, and a photocurable adhesive. After that, the photocurable adhesive is irradiated with light to be cured to form a polarization conversion element unit, and then, a plurality of the polarization conversion element units are laminated in the same direction via the photocurable adhesive. At the same time, the photocurable adhesive is cured by irradiating light from a direction substantially parallel to the substrate surface. Allowed to form a polarization converting element stack, thereafter, characterized by cutting the polarization conversion element stack obliquely to the substrate surface.

In the present invention, first, a first light-transmitting substrate, a λ / 2 retardation film, and a second light-transmitting substrate are laminated one by one to form a polarization conversion element unit. Lamination is performed to form a polarization conversion element laminate. That is, a method in which a plurality of first light-transmitting substrates, a λ / 2 retardation film, and a second light-transmitting substrate are sequentially stacked to form a polarization conversion element laminate is not employed. Therefore, the angle of the retardation film does not shift during the lamination process, and the yield of the polarization conversion element is improved. In the present invention, when forming the polarization conversion element laminate, the photocurable adhesive is cured by irradiating light from a direction substantially parallel to the substrate surface. Therefore, the irradiated light reaches the photocurable adhesive without being affected by the polarization separation film, the reflection film, the λ / 2 retardation film, and the like formed on the translucent substrate. Therefore, the curing time can be shortened, the productivity can be increased, and the curing failure does not occur, so that the yield of the polarization conversion element is improved.

According to another method for manufacturing a polarization conversion element of the present invention, a polarization separation film is formed on one of the parallel surfaces of the first light-transmitting substrate, while the parallel surfaces of the second light-transmitting substrate are formed. A reflection film is formed on one surface of the first light-transmitting substrate, and a surface of the first light-transmitting substrate opposite to the surface on which the polarization separation film is formed; and a second light-transmitting substrate. And the surface on the side where the reflective film is formed is bonded via a photocurable adhesive, a λ / 4 retardation film composed of a uniaxially stretched single-layer polymer film, and a photocurable adhesive. After that, the photocurable adhesive is irradiated with light to be cured to form a polarization conversion element unit, and then, a plurality of the polarization conversion element units are laminated in the same direction via the photocurable adhesive. At the same time, light is irradiated from a direction substantially parallel to the substrate surface to cure the photocurable adhesive and change the polarization. Forming a device stack, thereafter, the polarization conversion element stack, characterized in that cut obliquely to the substrate surface.

In the present invention, first, a first light-transmitting substrate, a λ / 4 retardation film, and a second light-transmitting substrate are laminated one by one to form a polarization conversion element unit. Lamination is performed to form a polarization conversion element laminate. That is, a method in which a plurality of first light-transmitting substrates, a λ / 4 retardation film, and a second light-transmitting substrate are sequentially laminated to form a polarization conversion element laminate is not employed. Therefore, the angle of the retardation film does not shift during the lamination process, and the yield of the polarization conversion element is improved. In the present invention, when forming the polarization conversion element laminate, the photocurable adhesive is cured by irradiating light from a direction substantially parallel to the substrate surface. Therefore, the irradiated light reaches the photocurable adhesive without being affected by the polarization separation film, the reflection film, the λ / 4 retardation film, and the like formed on the translucent substrate. Therefore, the curing time can be shortened, the productivity can be increased, and the curing failure does not occur, so that the yield of the polarization conversion element is improved.

According to the present invention, since the λ / 2 retardation film made of a polymer film or the λ / 4 retardation film is provided in the translucent substrate, it is not exposed on the surface of the polarization conversion element. For this reason, the moisture resistance and heat resistance of the polarization conversion element are improved. Moreover, in the present invention, a single-layer retardation film obtained by uniaxially stretching a polymer film is used instead of a retardation film obtained by laminating a plurality of biaxially stretched polymer films with an adhesive, so that the temperature change Even if there is, the films laminated by the adhesive do not cause positional displacement. Therefore, the heat resistance and durability of the polarization conversion element are significantly improved. Therefore, even if the polarization conversion element is arranged at a position close to the light source, no thermal deterioration occurs.

An embodiment of the present invention will be described with reference to the drawings. In the following description, the P wave and the S wave may be exchanged. In the following description, for the polarization conversion element, an integrator lens and a light shielding film are arranged in order to define a light incident area on the polarization conversion element, but illustration and description thereof are omitted.

[Embodiment 1]
1 (a), (b), (c) and (d) are cross-sectional views of a polarization conversion element according to the present embodiment. In this polarization conversion element, a λ / 2 retardation film has first and second translucencies. An enlarged view of a portion A1 showing a state of being sandwiched by members, an enlarged cross-sectional view of the A1 portion further enlarged, and an A2 portion showing that a reflective film is sandwiched by a first and a second translucent members. FIG. FIG. 2 is an explanatory diagram illustrating optical characteristics of the polarization conversion element illustrated in FIG.

As shown in FIGS. 1 (a), 1 (b), 1 (c) and 1 (d), the polarization conversion element 1 of the present embodiment is a rectangular parallelepiped optical element having a parallelogram having a cross-sectional shape having an acute angle of 45 degrees. The translucent base material 6 whose inclined end surfaces on both sides are joined so that the first translucent member 10 made of glass and the second translucent member 20 made of glass are alternately arranged. Have. Therefore, in the translucent substrate 6 of the polarization conversion element 1, the first oblique end face 11 of the first translucent member 10 and the first oblique end face 21 of the second translucent member are first. The bonding interface and the second bonding interface between the other inclined end face 12 of the first light transmissive member 10 and the other inclined end face 22 of the second light transmissive member 20 are each a translucent base material. It is inclined at an angle of 45 degrees with respect to the incident optical axis L with respect to 6, where a first optical layer and a second optical layer are formed.

In the present embodiment, as described below, the first optical layer is formed of the first light-transmitting member 10 and the second light-transmitting member 20 sandwiching the first optical layer on both sides. The polarization separating film 8 formed on the inclined end surface 11 of the first light transmitting member 10, the inclined end surface 11 of the first light transmitting member 10 where the polarization separating film 8 is formed, and the second light transmitting member 20 And a λ / 2 retardation film 30 (retardation plate) fixed with an adhesive 4 between the inclined end face 21 and the inclined end face 21. On the other hand, the second optical layer is constituted by a reflection film 9 (cold mirror) formed on the inclined end face 22 of the second light transmitting member 20, and the second optical layer on which the reflection film 9 is formed is formed. The inclined end surface 22 of the light transmitting member 20 is bonded and fixed to the inclined end surface 12 of the first light transmitting member 10 with the adhesive 4.

That is, in the polarization conversion element 1, the polarization separation film 8 that transmits the P-wave and reflects the S-wave out of natural light (P-wave and S-wave) is provided on the inclined end surface 11 of the first translucent member 10. Is formed. The reflection film 9 made of an aluminum film or the like is formed on the inclined end surface 22 of the second light transmitting member 20. The λ / 2 retardation film 30 is sandwiched between the polarization separating film 8 formed on the inclined end face 11 of the first light transmitting member 10 and the inclined end face 21 of the second light transmitting member 20. I have.

As the λ / 2 retardation film 30, a cyclic polyolefin resin film, a polyarylate film, a polycarbonate film, a polyethersulfone film, an alicyclic polyolefin film, a polyimide film, a polyethersulfone film, or the like can be used. Uses a uniaxially stretched polycarbonate film (polymer film). Such a film has a small wavelength dependence in the visible light region or has an inverse dispersion characteristic having no wavelength dependence. Further, it is preferable that the film has no angle dependence or has a very small angle dependence. Specifically, Pure Ace WR-R-λ / 2 (trade name) manufactured by Teijin Limited can be used, and its refractive index is close to that of the translucent members 10 and 20.

In the polarization conversion element 1 configured as described above, as shown in FIGS. 1 and 2, natural light L (random light including P-waves and S-waves) incident from below the translucent substrate 6 is subjected to polarization conversion. After entering the element 1, the P wave is transmitted and the S wave is reflected by the polarization separation film 8 at 90 degrees. Here, when the P wave that has passed through the polarization separation film 8 passes through the adjacent λ / 2 retardation film 30, the polarization plane is twisted by 90 degrees and becomes an S wave. On the other hand, the S wave reflected by the polarization splitting film 8 is totally reflected by the reflection film 9 and is emitted as it is on the optical axis parallel to the optical axis L of the incident light.

(Method of manufacturing polarization conversion element)
With reference to FIG. 3, a method for manufacturing the polarization conversion element 1 of the present embodiment will be described. FIG. 3 is a process sectional view illustrating the method for manufacturing the polarization conversion element illustrated in FIG. 1.

In FIG. 3A, in order to manufacture the polarization conversion element 1 shown in FIG. 1, a polarization separation film 8 is formed on one surface 101 of a first translucent substrate 100 having two parallel substrate surfaces. On the other hand, the reflection film 9 is formed on one surface 201 of the second translucent substrate 200 having two parallel substrate surfaces.

Next, as shown in FIG. 3B, a surface 101 of the first light-transmitting substrate 100 on which the polarization separation film 8 is formed, and a reflection film 9 of the second light-transmitting substrate 200 are formed. The photocurable adhesive 4 (see FIG. 1C), the λ / 2 retardation film 30, and the photocurable adhesive 4 (see FIG. c), the first light-transmitting substrate 100, the λ / 2 retardation film 30, and the second light-transmitting substrate 200 are stacked. Various adhesives such as an acrylic adhesive, a urethane adhesive, an epoxy adhesive, a polyester adhesive, a polyimide adhesive, an isocyanate adhesive, a vinyl chloride adhesive, and a silicone adhesive can be used. Although it can be used, in this embodiment, it is preferable to use an acrylic or silicone adhesive from the viewpoint of the influence on the λ / 2 retardation film 30 and the heat resistance.

Then, as shown by an arrow L11, from a direction substantially perpendicular to the substrate surface of the first light-transmitting substrate 100, or as shown by an arrow L12, on the substrate surface of the first light-transmitting substrate 100. Ultraviolet (UV) light is irradiated from a direction substantially parallel to the light-curing adhesive 4 to cure the light-curable adhesive 4, thereby forming the polarization conversion element unit 150. Here, light may be emitted from the second light-transmitting substrate 200 side. Further, light may be applied to the substrate surface of the first light-transmitting substrate 100 or the second light-transmitting substrate 200 from an oblique direction. Furthermore, by irradiating light from both the side of the first translucent substrate 100 and the side of the second translucent substrate 100 to cure the photocurable adhesive 4, no stress is generated. The adhesive can be cured.

Next, as shown in FIG. 3 (c), after a plurality of polarization conversion element units 150 are laminated in the same direction via the photocurable adhesive 4 (see FIG. 1 (d)). As shown by an arrow L13, the photocurable adhesive is cured by irradiating UV light from a direction substantially parallel to the substrate surface of the first translucent substrate 100 (second translucent substrate 200). Then, the polarization conversion element laminate 160 is formed.

Thereafter, as shown by a cutting line c in FIG. 3 (c), an angle of 45 degrees is formed with respect to the substrate surface of the first light-transmitting substrate 100 (the second light-transmitting substrate 200). After cutting the polarization conversion element laminate 110, the cut surface is polished to produce the polarization conversion element 1 shown in FIG.

(Effect of this embodiment)
As described above, in the present embodiment, the λ / 2 retardation film 30 made of a polymer film is used as the retardation film. Are not exposed on the surface of the polarization conversion element 1. Therefore, the λ / 2 retardation film 30 does not come into contact with the outside air at a high temperature, and thus the moisture resistance and heat resistance of the polarization conversion element 1 are improved.

In the present embodiment, the λ / 2 retardation film 30 is not a retardation film obtained by laminating a plurality of polymer films biaxially stretched with an adhesive, but a single layer obtained by uniaxially stretching a polymer film. Since the phase difference film is used, even when there is a temperature change, the films laminated with the adhesive do not cause positional displacement. Therefore, the heat resistance and durability of the polarization conversion element 1 are significantly improved. Therefore, even if the polarization conversion element 1 is arranged at a position close to the light source, thermal characteristics do not deteriorate, so that the durable period of the entire device such as a liquid crystal projector can be extended, and air noise caused by the fan can be reduced. Therefore, quietness can be improved.

Also, in the present embodiment, the bonding interface between the translucent substrates 10 and 20 is inclined by 45 degrees with respect to the incident optical axis L. Therefore, the incident optical axis L with respect to the polarization conversion element 1 and the emission optical axis from the polarization conversion element 1 can be made coincident and parallel.

Further, the λ / 2 retardation film 30 has a small wavelength dependency in the visible light range or has an inverse dispersion characteristic having no wavelength dependency. Thus, a function having no wavelength dependency can be provided.

Moreover, in the present embodiment, the refractive index of the λ / 2 retardation film 30 is close to the refractive index of the translucent substrates 10 and 20, so that the reflection loss is reduced by being sandwiched between the translucent substrates 10 and 20, Light transmittance can be increased. Further, by sandwiching the λ / 2 retardation film 30 between the translucent substrates 10 and 20, the planar accuracy of the translucent substrates 10 and 20 is transferred to both surfaces of the λ / 2 retardation film 30. become. Therefore, the planar accuracy of the λ / 2 retardation film 30 is significantly improved, and light diffusion can be controlled.

In addition, in this embodiment, by using no adhesive, only the heat resistance of the λ / 2 retardation film 30 needs to be considered, and the heat resistance can be increased.

Further, in the present embodiment, when manufacturing the polarization conversion element 1, the first light transmission substrate 100, the λ / 2 retardation film 30, and the second light transmission substrate 200 are laminated one by one to form the polarization conversion element. The unit 150 is formed, and then the polarization conversion element units 150 are stacked to form a polarization conversion element laminate 160. In other words, a method in which the first light-transmitting substrate 100, the λ / 2 retardation film 30, and the second light-transmitting substrate 200 are sequentially stacked in plurals to form the polarization conversion element laminate 160 is not adopted. . For this reason, the angle of the λ / 2 retardation film 30 does not shift during the lamination process, and the yield of the polarization conversion element 1 is improved.

In addition, in the present embodiment, when forming the polarization conversion element laminate 160, the photocurable adhesive 4 is cured by irradiating light from a direction substantially parallel to the substrate surface. Therefore, the irradiated light is reliably applied to the photo-curable adhesive 4 without being affected by the polarization separation film 8, the reflection film 9, the λ / 2 retardation film 30, and the like formed on the translucent substrates 100 and 200. Reach Therefore, the curing time can be shortened, the productivity can be increased, and the curing failure does not occur, so that the yield of the polarization conversion element 1 is improved.

[Modification of First Embodiment]
4A, 4B, 4C, and 4D are cross-sectional views of the polarization conversion device of the present embodiment. In this polarization conversion device, the λ / 2 retardation film has first and second translucencies. FIG. 3 is an enlarged view of an A1 ′ portion showing a state of being sandwiched by members, an enlarged sectional view of the A1 ′ portion further enlarged, and a state of a reflection film being sandwiched between first and second translucent members. It is an enlarged view of A2 'part. FIG. 4 is an explanatory diagram illustrating optical characteristics of the polarization conversion element illustrated in FIG. Note that the polarization conversion element of this embodiment has the same basic configuration as that of the first embodiment, and therefore, portions having common functions are denoted by the same reference numerals and description thereof is omitted. In addition, the method for manufacturing the polarization conversion element 1 of the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

4A, 4B, 4C, and 4D, the polarization conversion element 1 of this embodiment emits natural light as P-polarized light, and the configuration is different from that of the first embodiment. The light incident side and the light exit side are reversed. That is, also in the present embodiment, the polarization conversion element 1 has the first transparent member 10 made of glass and the second transparent member 20 made of glass having a parallelogram having a 45 ° acute angle in cross section. And a light-transmissive base material 6 in which the inclined end faces on both sides are joined so that they are alternately arranged. Further, a first bonding interface between the inclined end face 11 on one side of the first light transmissive member 10 and the inclined end face 21 on one side of the second light transmissive member, and the first light transmissive member 10 The second bonding interface between the other inclined end face 12 and the other inclined end face 22 of the second translucent member 20 has an angle of 45 degrees with respect to the incident optical axis L with respect to the translucent substrate 6. , Where a first optical layer and a second optical layer are formed.

Also in this embodiment, as the first optical layer, the polarization separation film 8 formed on the inclined end face 11 of the first light transmissive member 10 and the polarization separation film 8 of the first light transmissive member 10 are formed. A λ / 2 retardation film 30 (retardation plate) fixed with an adhesive 4 between the inclined end surface 11 and the inclined end surface 21 of the second light transmitting member 20. On the other hand, the second optical layer is constituted by the reflection film 9 formed on the inclined end face 22 of the second light-transmitting member 20, and the second light-transmitting member on which the reflection film 9 is formed is formed. The inclined end surface 22 of the member 20 is bonded and fixed to the inclined end surface 12 of the first translucent member 10 with the adhesive 4.

In the polarization conversion element 1 configured as described above, as shown in FIGS. 4 and 5, natural light L (random light including P and S waves) incident from above the translucent substrate 6 is subjected to polarization conversion. After being incident on the element 1, the light passes through the λ / 2 retardation film 30, the P wave is transmitted by the polarization separation film 8, and the S wave is reflected by 90 degrees. Here, the P wave that has passed through the polarization separation film 8 is emitted as it is, while the S wave that has been reflected by the polarization separation film 8 has a polarization plane of 90 degrees when transmitted through the adjacent λ / 2 retardation film 30. After being twisted to become a P-wave, the light is totally reflected by the reflection film 9 and is emitted as-is as a P-wave with an optical axis parallel to the optical axis L of the incident light.

[Embodiment 2]
6A, 6B, 6C, and 6D are cross-sectional views of the polarization conversion device of the present embodiment. In this polarization conversion device, the λ / 4 retardation film has first and second translucencies. An enlarged view of a portion B1 showing a state of being sandwiched between members, an enlarged cross-sectional view of this B1 portion further enlarged, and a view B2 showing a state of a polarization separation film being sandwiched between first and second translucent members. It is an enlarged view of a part. FIG. 7 is an explanatory diagram illustrating optical characteristics of the polarization conversion element illustrated in FIG.

As shown in FIGS. 6A, 6B, 6C, and 6D, the polarization conversion element 1 of the present embodiment is a rectangular parallelepiped optical element, and has a parallelogram having a cross-sectional shape having an acute angle of 45 degrees. A transparent base material 6 having inclined end faces on both sides joined to each other such that a first transparent member 10 made of glass and a second transparent member 20 made of glass are alternately arranged. are doing. Therefore, in the translucent substrate 6 of the polarization conversion element 1, the first oblique end face 11 of the first translucent member 10 and the first oblique end face 21 of the second translucent member are first. The bonding interface and the second bonding interface between the other inclined end face 12 of the first light transmissive member 10 and the other inclined end face 22 of the second light transmissive member 20 are each a translucent base material. It is inclined at an angle of 45 degrees with respect to the incident optical axis L with respect to 6, where a first optical layer and a second optical layer are formed.

In the present embodiment, as described below, the first optical layer is formed of the first light-transmitting member 10 and the second light-transmitting member 20 sandwiching the first optical layer on both sides. The polarization separating film 8 is formed on the inclined end face 11 of the first translucent member 10. The inclined end face 11 on which the polarization separating film 8 is formed is bonded to the inclined end face 21 of the second translucent member 20. It is adhered and fixed by the agent 4. On the other hand, the second optical layer is composed of the reflecting film 9 formed on the inclined end face 22 of the second light transmitting member 20 and the second light transmitting member 20 on which the reflecting film 9 is formed. A λ / 4 retardation film 40 (retardation plate) fixed with the adhesive 4 between the inclined end face 22 and the inclined end face 12 of the first light transmitting member 10.

That is, in the polarization conversion element 1, the polarization separation film 8 that transmits the P-wave and reflects the S-wave out of natural light (P-wave and S-wave) is provided on the inclined end surface 11 of the first translucent member 10. Is formed. The reflection film 9 made of an aluminum film or the like is formed on the inclined end surface 22 of the second light transmitting member 20. The λ / 4 retardation film 40 is sandwiched between the reflection film 9 formed on the inclined end surface 22 of the second light transmitting member 20 and the inclined end surface 12 of the first light transmitting member 10. .

In the present embodiment, the λ / 4 retardation film 40 is made of a uniaxially stretched polycarbonate film (polymer film), and has a small wavelength dependence in the visible light region or a film having a reverse dispersion characteristic having no wavelength dependence. It is. In addition, the refractive index is close to the refractive index of the translucent substrates 10 and 20.

In the polarization conversion element 1 configured as described above, as shown in FIGS. 6A and 7, the natural light L incident on the polarization conversion element 1 from below is transmitted through the polarization separation film 8 as a P wave, and as an S wave. It is reflected 90 degrees. Here, the P wave that has passed through the polarization separation film 8 is emitted as it is as a P wave on the same optical axis as the optical axis of the incident light. On the other hand, the S wave reflected by the polarization separation film 8 is transmitted through the λ / 4 retardation film 40, and the polarization plane is twisted by 45 degrees to be circularly polarized. The light is totally reflected by the reflection film 23 formed on the base material 20. The totally reflected light passes through the λ / 4 phase difference film 40 again, and its polarization plane is twisted by 45 degrees to become a P-wave, and is emitted with the same optical axis as the incident light.

(Method of manufacturing polarization conversion element)
With reference to FIG. 8, a method for manufacturing the polarization conversion element 1 of the present embodiment will be described. FIG. 8 is a process sectional view illustrating the method for manufacturing the polarization conversion element illustrated in FIG. 6.

In FIG. 8A, when manufacturing the polarization conversion element 1 of the present embodiment, the polarization separation film 8 is formed on one surface 101 of a first light-transmitting substrate 100 having two parallel substrate surfaces. The reflective film 9 is formed on one surface 201 of a second light-transmitting substrate 200 having two parallel substrate surfaces.

Next, as shown in FIG. 8B, a surface 102 of the first light-transmitting substrate 100 opposite to the surface 101 on which the polarization separation film 8 is formed, and a second light-transmitting substrate 200 The photocurable adhesive 4 (see FIG. 6C), the λ / 4 retardation film 40, and the photocurable adhesive 4 (between the surface 201 on which the reflective film 9 is formed). The first light-transmitting substrate 100, the λ / 4 retardation film 40, and the second light-transmitting substrate 200 are stacked so as to sandwich (see FIG. 6C).

Then, as shown by an arrow L11, from a direction substantially perpendicular to the substrate surface of the first light-transmitting substrate 100, or as shown by an arrow L12, on the substrate surface of the first light-transmitting substrate 100. Ultraviolet (UV) light is irradiated from a direction substantially parallel to the light-curing adhesive 4 to cure the light-curable adhesive 4, thereby forming the polarization conversion element unit 150. Here, light may be emitted from the second light-transmitting substrate 200 side. Further, light may be applied to the substrate surface of the first light-transmitting substrate 100 or the second light-transmitting substrate 200 from an oblique direction. Furthermore, by irradiating light from both the side of the first translucent substrate 100 and the side of the second translucent substrate 100 to cure the photocurable adhesive 4, no stress is generated. The adhesive can be cured.

Next, as shown in FIG. 8C, after a plurality of polarization conversion element units 150 are laminated in the same direction via the photocurable adhesive 4 (see FIG. 6D). As shown by an arrow L13, the photocurable adhesive is cured by irradiating UV light from a direction substantially parallel to the substrate surface of the first translucent substrate 100 (second translucent substrate 200). Then, the polarization conversion element laminate 160 is formed.

Thereafter, as shown by a cutting line c in FIG. 3 (c), an angle of 45 degrees is formed with respect to the substrate surface of the first light-transmitting substrate 100 (the second light-transmitting substrate 200). After cutting the polarization conversion element laminate 160, the cut surface is polished to produce the polarization conversion element 1 shown in FIG.

(Effect of this embodiment)
As described above, in the present embodiment, the λ / 4 retardation film 40 made of a polymer film is used as the retardation film. However, the λ / 4 retardation film 40 is provided in a light-transmitting substrate. Therefore, it is not exposed on the surface of the polarization conversion element 1. Therefore, the λ / 2 retardation film 40 does not come into contact with the outside air at a high temperature. Further, as the λ / 4 retardation film 40, a single-layer retardation film obtained by uniaxially stretching a polymer film is used instead of a retardation film obtained by laminating a plurality of biaxially stretched polymer films with an adhesive. Therefore, even when there is a temperature change, the films laminated with the adhesive material do not cause displacement. Therefore, the same effects as in the first embodiment are obtained, such as the heat resistance and the durability of the polarization conversion element 1 are significantly improved.

Further, in the present embodiment, when manufacturing the polarization conversion element 1, the first light transmission substrate 100, the λ / 4 retardation film 40, and the second light transmission substrate 200 are laminated one by one to form a polarization conversion element. The unit 150 is formed, and then the polarization conversion element units 150 are stacked to form a polarization conversion element laminate 160. In other words, a method is not adopted in which the first light-transmitting substrate 100, the λ / 2 retardation film 40, and the second light-transmitting substrate 200 are sequentially stacked in plurals to form the polarization conversion element laminate 160. . For this reason, the angle of the λ / 4 retardation film 40 does not shift during the lamination process, so that the same effect as that of the first embodiment, such as an improvement in the yield of the polarization conversion element 1, is obtained.

According to the present invention, since the λ / 2 retardation film made of a polymer film or the λ / 4 retardation film is provided in the translucent substrate, it is not exposed on the surface of the polarization conversion element. For this reason, the moisture resistance and heat resistance of the polarization conversion element are improved. Moreover, in the present invention, a single-layer retardation film obtained by uniaxially stretching a polymer film is used instead of a retardation film obtained by laminating a plurality of biaxially stretched polymer films with an adhesive, so that the temperature change Even if there is, there is no displacement between the films laminated with the adhesive. Therefore, the heat resistance and durability of the polarization conversion element are significantly improved. Therefore, even if the polarization conversion element is disposed at a position close to the light source, thermal characteristics do not deteriorate, so that the durability of the entire device such as a liquid crystal projector can be extended, and air noise from the fan can be reduced. Also, the quietness can be improved.

(A), (b), (c), and (d) are cross-sectional views of a polarization conversion element according to Embodiment 1 of the present invention, in which a λ / 2 retardation film is composed of first and second translucent members. An enlarged view of the portion A1 showing the state of being sandwiched between the first and second transparent members, and an enlarged cross-sectional view of the portion A1 showing the state of being sandwiched between the first and second translucent members. It is an expanded sectional view. FIG. 2 is an explanatory diagram illustrating optical characteristics of the polarization conversion element illustrated in FIG. 1. FIG. 2 is a process cross-sectional view illustrating a method for manufacturing the polarization conversion element illustrated in FIG. 1. (A), (b), (c), and (d) are cross-sectional views of a polarization conversion element using a λ / 2 retardation film according to a modification of the first embodiment of the present invention, and λ / 2 retardation. An enlarged view of an A1 'portion showing a state in which the film is sandwiched between the first and second translucent members, an enlarged sectional view of the A1' portion further enlarged, and a reflection film of the first and second translucent members. It is an expanded sectional view of A2 'part showing signs that it is caught between optical members. FIG. 5 is an explanatory diagram showing optical characteristics of the polarization conversion device shown in FIG. (A), (b), (c), and (d) are cross-sectional views of a polarization conversion element according to Embodiment 2 of the present invention, in which a λ / 4 retardation film is composed of first and second translucent members. , An enlarged cross-sectional view of the B1 portion further enlarged, and a B2 portion showing the polarization separation film sandwiched between the first and second translucent members. FIG. FIG. 7 is an explanatory diagram illustrating optical characteristics of the polarization conversion element illustrated in FIG. 6. FIG. 7 is a process cross-sectional view illustrating a method for manufacturing the polarization conversion element illustrated in FIG. 6. It is explanatory drawing of the conventional polarization conversion element.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Polarization conversion element 4 Adhesive 6 Translucent base material 8 Polarization separation film 9 Reflective films 10, 20 Translucent member 30 λ / 2 retardation film 40 λ / 4 retardation film 100 First translucent substrate 200 Second translucent substrate 150 Polarization conversion element unit 160 Polarization conversion element laminate

Claims (8)

A first optical layer and a second optical layer are parallel to each other in a light-transmissive substrate in which inclined end surfaces of a plurality of light-transmissive members are joined to each other, and are parallel to an incident optical axis with respect to the light-transmissive substrate. Placed diagonally,
The first optical layer is formed on an inclined end face of the first light-transmissive member among the first light-transmissive member and the second light-transmissive member that sandwich the first optical layer on both sides. And a λ / 2 phase difference adhesively fixed between the inclined end face of the first light transmitting member on which the polarized light separating film is formed and the inclined end face of the second light transmitting member. Composed of film and
The second optical layer is a reflective film,
The polarization converter according to claim 1, wherein the λ / 2 retardation film comprises a uniaxially stretched single-layer polymer film. A first optical layer and a second optical layer are parallel to each other in a light-transmissive substrate in which inclined end surfaces of a plurality of light-transmissive members are joined to each other, and are parallel to an incident optical axis with respect to the light-transmissive substrate. Placed diagonally,
The first optical layer is a polarization separation film,
The second optical layer is formed on an inclined end face of the second light-transmitting member among the first light-transmitting member and the second light-transmitting member sandwiching the second optical layer on both sides. Reflecting film, a λ / 4 retardation film adhesively fixed between an inclined end surface of the second light transmitting member on which the reflecting film is formed and an inclined end surface of the first light transmitting member. Consisting of
The λ / 4 retardation film is a uniaxially stretched single-layer polymer film, and is a polarization conversion element. 3. The light-transmissive base material according to claim 1, wherein the first light-transmissive member and the second light-transmissive member are alternately arranged in the first light-transmissive member and the second light-transmissive member. The inclined end faces at both ends of the light-transmitting member are joined to each other,
Each of the first optical layer and the second optical layer is a first bonding interface between one inclined end surface of the first light transmitting member and one inclined end surface of the second light transmitting member. And a second junction interface between the other inclined end face of the first translucent member and the other inclined end face of the second translucent member. (4) The polarization conversion element according to any one of (1) to (3), wherein the polymer film is made of polycarbonate. (5) The polarization conversion element according to any one of (1) to (4), wherein each of the first optical layer and the second optical layer forms an angle of 45 degrees with the incident optical axis. The method according to any one of claims 1 to 4, wherein the uniaxially stretched single-layered polymer film has a small wavelength dependence in a visible light region or an inverse dispersion characteristic having no wavelength dependence. Characteristic polarization conversion element. A polarized light separating film is formed on one of the parallel surfaces of the first light-transmitting substrate, and a reflective film is formed on one of the parallel surfaces of the second light-transmitting substrate. Every
The one surface of the first light-transmitting substrate on which the polarization splitting film is formed and the surface of the second light-transmitting substrate on the side opposite to the surface on which the reflection film is formed are illuminated. After bonding via a curable adhesive, a λ / 2 retardation film consisting of a uniaxially stretched single-layer polymer film, and a photocurable adhesive, the photocurable adhesive is cured by irradiating light. To form a polarization conversion element unit,
Next, a plurality of the polarization conversion element units are laminated via a photocurable adhesive in the same direction, and the photocurable adhesive is cured by irradiating light from a direction substantially parallel to the substrate surface. To form a polarization conversion element laminate,
Thereafter, the polarization conversion element laminate is cut obliquely to a substrate surface. A polarized light separating film is formed on one of the parallel surfaces of the first light-transmitting substrate, and a reflective film is formed on one of the parallel surfaces of the second light-transmitting substrate. Every
The surface of the first light-transmitting substrate on the side opposite to the side on which the polarization separation film is formed and the surface of the second light-transmitting substrate on the side on which the reflection film is formed are illuminated. After laminating through a curable adhesive, a λ / 4 retardation film consisting of a uniaxially stretched single-layer polymer film, and a photocurable adhesive, the photocurable adhesive is cured by irradiating light. To form a polarization conversion element unit,
Next, a plurality of the polarization conversion element units are laminated via a photocurable adhesive in the same direction, and the photocurable adhesive is cured by irradiating light from a direction substantially parallel to the substrate surface. To form a polarization conversion element laminate,
Thereafter, the polarization conversion element laminate is cut obliquely to a substrate surface.

Images