JP2008304919A - Optical device using polarizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device using a polarizer having high durability and capable of selecting suitable polarized light. <P>SOLUTION: The optical device has an electro-optical element which modulates luminous flux emitted from a light source according to image information, and the polarizer 42 arranged on the light incident side and/or light outgoing side of the electro-optical element. The polarizer 42 has a polarizer base plate 421 formed of material having light transmittance of 97% or more, and a birefringent portion 422 formed by arranging minute metal convex lines in stripe on the surface of the polarizer base plate. The birefringent portion 422 is provided on the light outgoing side out of two surfaces of the polarizer base plate 421. The birefringent portion 422 is provided with a protective base plate 423 covering the birefringent portion 422. The protective base plate 423 is bonded to the polarizer base plate 421 at the outer peripheral end with an elastic adhesive 424 so that the birefringent portion 422 is sealed and enclosed by the protective base plate 423 and the elastic adhesive 424. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical apparatus using a polarizer that selects a linearly polarized light beam from an incident light beam.

  Conventionally, as an optical device using an electro-optical element, a light source, an electro-optical element that modulates a light beam emitted from the light source according to image information, and projection optics that enlarges and projects the light beam modulated by the electro-optical element Projectors equipped with a system are used. A liquid crystal element is known as the electro-optic element, and the liquid crystal element is sealed and encapsulated with an electro-optic material such as liquid crystal between a pair of transparent substrates, and is disposed between the incident side and the emission side between the pair of transparent substrates. It is comprised including two polarizing plates used as the polarizer arrange | positioned. Conventionally, this polarizing plate is made of an organic material such as PVA (polyvinyl alcohol) containing iodine or a dye, and a film stretched in a certain direction is sandwiched by a support such as a glass substrate or attached to the support. It was configured by.

  However, since such a conventional polarizing plate is made of an organic material, it is vulnerable to high temperatures, and when used continuously in an environment of 70 ° C. or higher, the color is lost and the polarizing function gradually increases. There is a problem of being lost. For this reason, a structural birefringent polarizer has been proposed as a polarizing plate made of an inorganic material. This structural birefringent polarizer is formed by forming a birefringent portion in which a plurality of fine linear ridges are arranged in a stripe shape with a metal such as aluminum on the surface of a transparent substrate such as glass. A linearly polarized light beam can be selected from the incident light beam by utilizing the diffraction phenomenon of the space between the parts.

  However, since such a structural birefringent polarizer absorbs part of the light beam incident on the birefringent portion as heat, the glass substrate is thermally distorted, making it impossible to select an appropriate polarized light. is there. In particular, when the glass substrate is used in such a manner that it is disposed on the exit side, there is a problem in that the polarization axis of the polarized light beam selected by the birefringent portion rotates within the glass substrate, causing a light leakage phenomenon.

  An object of the present invention is to provide an optical apparatus using a polarizer that has high durability and can select appropriate polarized light.

The present invention intends to achieve the above object by appropriately selecting a substrate material and appropriately arranging a polarizer in an optical apparatus using a structural birefringent polarizer.
Specifically, the optical apparatus of the present invention includes an electro-optic element that modulates a light beam emitted from a light source according to image information, and a polarization that is disposed on a light incident side and / or a light emission side of the electro-optic element. And the electro-optic element includes a pair of substrates and an electro-optic material sandwiched between the pair of substrates, and the polarizer is made of a material having a light transmittance of 97% or more. An optical apparatus comprising: a polarizer substrate; and a birefringence portion configured by arranging fine metal protrusions in stripes on a surface of the polarizer substrate, the birefringence Is provided on the light exit side of the two surfaces of the polarizer substrate, the birefringent portion is provided with a protective substrate that covers the birefringent portion, and the protective substrate is used for the polarizer. The substrate and the outer peripheral edge are bonded with an elastic adhesive, and the birefringent portion is connected to the protective substrate and the protective substrate. Characterized in that it is sealed with an elastic adhesive.
Here, as a substrate material for a polarizer having a light transmittance of 97% or more, there are sapphire, LBC3N (manufactured by HOYA Optics), neoceram (manufactured by Nippon Electric Glass), and the like.

Furthermore, the substrate material for the polarizer is preferably a material having a linear expansion coefficient of 4.8 × 10 ⁻⁷ / K or less. Examples of such a material include quartz glass, neo-serum, clear serum (made by OHARA), and the like. Of these, it is more preferable to use crystallized glass or quartz glass. In addition, as the metal ridges constituting the birefringent part, ridges made of aluminum can be adopted, and the polarization characteristics of the polarizer depend on the pitch, height, and duty ratio of the ridges. Determined. For example, a birefringence portion can be formed by arranging a plurality of ridge portions having a width of 65 nm and a height of 120 to 170 nm at a pitch of 144 nm.

  According to the present invention, since the polarizer substrate is disposed on the incident side, the light beam after selection of the polarization is affected by the thermal distortion of the polarizer substrate and the polarization axis rotates. Therefore, it is possible to select an appropriate polarization. In addition, by adopting a material with a low coefficient of linear expansion as the substrate material for the polarizer, distortion hardly occurs even if the heat absorbed by the birefringent portion acts on the substrate material for the polarizer. Occurrence of a dropout phenomenon or the like can be prevented. Furthermore, since the birefringent portion is made of metal, sufficient durability can be ensured.

  The substrate material for the polarizer preferably has a thermal conductivity of 6.21 W / (m · K) or more. In this case, sapphire or quartz can be employed as a specific polarizer substrate material.

  According to the present invention, by adopting a material having high thermal conductivity as the substrate material for the polarizer, it is possible to retain the polarizer even if the heat absorbed by the birefringent portion acts on the substrate material for the polarizer. Since heat can be immediately radiated through the frame or the like, thermal distortion is unlikely to occur in the polarizer substrate, and the occurrence of light leakage phenomenon of the polarizer can be prevented in the same manner as described above.

Further, the polarizer substrate material preferably has a photoelastic constant of 0.43 × 10 ⁻¹² / Pa or less. Here, the photoelastic constant is a proportional constant that gives the relationship between the stress acting on the polarizer substrate and the optical path difference due to the birefringence of light transmitted through the polarizer substrate in the state where the stress is applied. Specifically, the optical path difference due to birefringence is δ (nm), the internal stress of the substrate perpendicular to the light traveling direction is Ps (× 10 ⁵ Pa), and the thickness of the polarizer substrate is d (mm). Then, a relationship such as [Equation 1] is established.

[Equation 1]
δ = B · Ps · d / 10

The proportionality constant B in [Equation 1] is a photoelastic constant, and is usually displayed in units of (10 ⁻¹² / Pa).
As the substrate material for a polarizer having the above-described photoelastic constant, for example, LBC3N manufactured by HOYA Optics, which is a low photoelastic glass, can be employed. According to the present invention as described above, the polarizer substrate material is made of a material having a low photoelastic constant, so that the heat absorbed by the birefringent portion can be obtained from [Equation 1]. Even if an internal stress Ps is generated due to thermal strain by acting on the light, the photoelastic constant B is small, and as a result, the optical path difference δ can be kept small, and the occurrence of light leakage phenomenon or the like can be prevented.

In the above, it is preferable that the light incident surface of the polarizer substrate is subjected to an antireflection treatment.
By performing the antireflection treatment in this way, the reflected light can be reduced and the utilization rate of the incident light beam can be improved, so that the loss of light transmitted through the polarizer can be reduced.

  In the above-described polarizer, it is preferable that a protective substrate that covers the birefringent portion is provided. As the material of the protective substrate, it is preferable to employ the same material as the polarizer substrate on which the birefringent portion is formed. Specific examples include crystallized glass, quartz glass, sapphire, and quartz. As described above, since the birefringent portion is configured by arranging strips made of metal such as aluminum in a stripe shape, the strips may be deteriorated in a high temperature and high humidity environment. . Therefore, by providing the protective substrate in this way, it is possible to prevent deterioration of the ridges, and therefore it is possible to further improve the durability of the polarizer, and an optical apparatus including such a polarizer is Even if it is exposed to a high temperature and high humidity environment during transportation or used in a high temperature and high humidity environment, the polarizer does not deteriorate.

As such a protective substrate, it is desirable that the linear expansion coefficient, thermal conductivity, and photoelastic constant are the same as those of the polarizer substrate described above. Furthermore, an appropriate range for the thickness of the protective substrate is specified from the relationship between the linear expansion coefficient, the thermal conductivity, and the photoelastic constant. That is, the protective substrate has a thickness of d (mm), a photoelastic constant of B (10 ⁻¹² / Pa), a Young's modulus of E (Pa), a linear expansion coefficient of α (1 / K), and heat conduction. When the rate is ρ (W / (m · K)), it is desirable to be represented by [Equation 2].

[Equation 2]
B × E × α / ρ × d ≦ 9.8 × 10 ⁻⁵ (m ² / W)

Furthermore, it is preferable that the light incident / exit surface of the protective substrate is also subjected to antireflection treatment.
As described above, the anti-reflection treatment is performed on the light incident / exit surface of the protective substrate as well, so that the light utilization rate can be improved as described above, and unnecessary reflected light on the transmission surface can be prevented. Therefore, the signal S / N can be improved.

  And it is preferable that the protective substrate mentioned above is adhere | attached on the board | substrate for polarizers by the elastic adhesive agent at the outer peripheral edge part, and the birefringent part is sealed with the protective substrate and the elastic adhesive agent. Here, the elastic adhesive is used to absorb the difference in movement between the two substrates and hermetically enclose the birefringent portion, and it is preferable to use a silicone-based material from the viewpoint of durability. It is more preferable to employ an unreacted oil component suppression type.

  When the protective substrate and the polarizer substrate are bonded together with an elastic adhesive between the substrate surfaces, the space between the ridges of the birefringent portion is filled with the elastic adhesive, and the light diffraction ability of the birefringent portion is reduced. As a result, the selection efficiency of polarized light is deteriorated. Therefore, the protective substrate and the polarizer substrate can be prevented from being filled with an adhesive by adhering the elastic substrate at the outer peripheral end portion with an elastic adhesive, Selection of appropriate polarized light can be realized in the space, and an optically excellent polarizer can be obtained. In addition, by using an unreacted oil component-suppressing type silicone adhesive, it is possible to prevent the solvent from seeping into the space between the ridges after bonding, which is further excellent optically. It can be a polarizer.

  Further, the protective substrate described above may be formed in substantially the same shape as the polarizer substrate, or may be formed in a larger shape than the polarizer substrate. By making the protective substrate substantially the same shape as the polarizer substrate, the polarizer can be made to the minimum size necessary for selection of polarized light, so that the polarizer can be miniaturized. In this case, both substrates can be bonded by applying an elastic adhesive to the end surfaces of the protective substrate and the polarizer substrate. On the other hand, by making the protective substrate larger than the polarizer substrate, adhesion with an elastic adhesive can be performed between the end surface of the polarizer substrate and the surface of the protective substrate, which increases the bonding area. It is preferable for improving the internal sealing performance.

  Furthermore, it is preferable that a spacer is interposed between the polarizer substrate and the protective substrate. The spacer is preferably composed of a photo-curing adhesive or a double-sided tape whose front and back surfaces are elastic adhesive surfaces. When using a photo-curing adhesive as a spacer, apply the photo-curing adhesive in a dot-like manner between the polarizer substrate and the protective substrate, overlay the polarizer substrate and the protective substrate, and design the protective substrate. After moving to the intermediate position, the adhesive may be cured by irradiating ultraviolet rays or the like. When a double-sided tape is used as a spacer, an elastic adhesive surface using acrylic resin or silicone can be considered. The double-sided tape is preferably attached to the entire circumference of the birefringent portion.

  By interposing the spacer in this way, the protective substrate can be disposed at the most appropriate position when selecting the polarized light at the birefringent portion, so that an optically superior polarizer can be obtained. In addition, when the double-sided tape is used as a spacer, the spacer can be installed simply by attaching the double-sided tape, so that workability is improved. Furthermore, if a double-sided tape is applied to the entire circumference of the birefringent part, even if an unreacted oil component oozes out from the silicone adhesive that adheres the protective substrate and the polarizer substrate, The birefringent portion is not soiled by the reaction oil component.

Furthermore, the adhesive surface of the spacer is preferably composed of a silicone-based adhesive.
Silicone has good UV resistance of the adhesive surface, so there is no risk of deterioration due to UV rays. Moreover, since heat resistance is also favorable, there is no possibility of being affected by heat absorbed by the birefringent portion and causing deformation or the like.

The spacer has a support made of woven fabric or non-woven fabric, and an adhesive surface coated with a silicone-based adhesive is provided on the front and back surfaces of the support, or the spacer is made of silicone. It is preferable that it consists only of a system adhesive. In the case where the support is provided, the strength of the double-sided tape can be secured by the support, so that the workability when the double-sided tape is applied becomes good.
On the other hand, when the spacer is made of only a silicone-based adhesive, the difference in behavior due to heat between the protective substrate and the polarizer substrate can be absorbed, and the birefringent portion formed on the substrate and the protective substrate are appropriately Can keep a great distance. Moreover, since it consists only of a silicone type adhesive, the thickness of a spacer becomes thin and it can aim at thickness reduction of a polarizer.

  The present invention is established as an optical apparatus including such a polarizer. Specifically, the optical apparatus includes an electro-optical element that modulates a light beam emitted from a light source according to image information. In addition, the electro-optical element includes any of the above-described polarizers, which are sealed and sandwiched between an electro-optical material between a pair of transparent substrates and disposed on the light incident side and / or the light output side. It is characterized by that. And according to such an optical device, since it is equipped with a polarizer that is highly durable and can select appropriate polarized light, it is possible to provide an optical device that is excellent in durability and optical characteristics. it can.

  According to the present invention as described above, since the substrate is arranged on the incident side, the light beam after selection of the polarized light is not affected by the thermal strain of the substrate, and the polarization axis does not rotate. Appropriate polarized light can be selected. In addition, by adopting any one of low linear expansion coefficient, high thermal conductivity, and low photoelastic constant as the substrate material, the light of the polarizer can be used even if the heat absorbed by the birefringence part acts on the substrate material. Occurrence of a dropout phenomenon or the like can be prevented. By using the polarizer for an optical device, it is possible to realize an optical device that operates stably even at a high temperature without any light leakage phenomenon.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the structure of an optical system of a projector 1 that is an optical apparatus according to an embodiment of the present invention. The projector 1 includes an integrator illumination optical system 10, a color separation optical system 20, a relay optical system 30, an electro-optical device 40, a cross dichroic prism 50 that is a color synthesis optical system, and a projection lens 60 that is a projection optical system. Yes.
The integrator illumination optical system 10 includes a light source device 11 and a uniform illumination optical system 15. The light source device 11 is a light source lamp 12 such as a metal halide lamp or a high-pressure mercury lamp, and an emission direction of a light beam emitted from the light source lamp 12. It is comprised from the paraboloid reflector 13 which arranges and parallelizes.
The uniform illumination optical system 15 has a function of dividing the light beam emitted from the light source device 11 into a plurality of partial light beams and aligning the polarization direction of each partial light beam with a P-polarized light beam or an S-polarized light beam. An array 16, a second lens array 17, a PBS array 18, and a condenser lens 19 are included.

The first lens array 16 has a function as a light beam splitting optical element that splits a light beam emitted from the light source lamp 12 into a plurality of partial light beams, and is arranged in a matrix in a plane orthogonal to the illumination optical axis A. The aspect ratio of each lens corresponds to the aspect ratio of the image forming area of the liquid crystal panels 41R, 41G, and 41B constituting the electro-optical device 40 described later.
The second lens array 17 is an optical element that condenses the partial light beams divided by the first lens array 16 described above, and is arranged in a matrix in a plane perpendicular to the illumination optical axis A, like the first lens array 16. A plurality of lenses are arranged. The arrangement of the lenses corresponds to the lenses constituting the first lens array 16, but the size thereof is the same as the aspect ratio of the image forming area of the liquid crystal panels 41R, 41G, 41B as in the first lens array 16. There is no need to respond.

The PBS array 18 as a polarization conversion element is an optical element that aligns the polarization direction of each partial light beam divided by the first lens array 16 in one direction, and the incident light beam is one of a P-polarized light beam and an S-polarized light beam. A polarization separation film that transmits the other and reflects the other to separate into two polarized light beams, a reflection mirror that folds the traveling direction of the polarized light beam reflected by the polarization separation film and aligns it with the outgoing direction of the transmitted polarized light beam, The phase difference plate is disposed on the exit side end face of one of the polarized light beams separated by the separation film and performs polarization conversion of the polarized light beam.
The condenser lens 19 condenses a plurality of partial light beams that have passed through the first lens array 16, the second lens array 17, and the PBS array 18, and superimposes them on the image forming regions of the liquid crystal panels 41R, 41G, and 41B. It is a lens that has.

The color separation optical system 20 includes two dichroic mirrors 21 and 22 and a reflection mirror 23, and a plurality of partial light beams emitted from the integrator illumination optical system 10 by these mirrors 21, 22 and 23 are converted into red light. In other words, the red light R and the other color lights G and B are separated by the dichroic mirror 21, and the green light G and blue light are separated by the dichroic mirror 22. The light B is separated.
The relay optical system 30 includes an incident side lens 31, a relay lens 33, reflection mirrors 35 and 37, and an emission side lens 39, and the color light separated by the color separation optical system 20, for example, blue light B in this example. It has a function of leading to the liquid crystal panel 41B.

The electro-optical device 40 includes: liquid crystal panels 41R, 41G, and 41B; polarizing plates 42 and 43 as polarizers disposed on the incident side and the outgoing side of the liquid crystal panels 41R, 41G, and 41B; And a field lens 44 disposed on the incident side.
The liquid crystal panels 41R, 41G, and 41B are obtained by hermetically sealing a liquid crystal that is an electro-optical material between a pair of transparent glass substrates. For example, a polarizing plate according to a given image signal using a polysilicon TFT as a switching element. The polarization direction of the polarized light emitted from 42 is modulated.

  The polarizing plate 42 is an optical element that selectively transmits linearly polarized light from the incident light beam. For example, in this example, the polarizing plate 42 is configured to transmit only the S-polarized light beam among the incident light beams. The polarizing plate 43 is configured to transmit only the P-polarized light beam among the light beams modulated by the liquid crystal panels 41R, 41G, and 41B. The details of the structure of these polarizing plates 42 and 43 will be described later. The field lens 44 is an optical element for making the emitted light beam narrowed down by the condenser lens 19 of the integrator illumination optical system 10 parallel to the illumination optical axis, and is disposed in front of the liquid crystal panels 41R and 41G. In the liquid crystal panel 41B, the exit side lens 39 of the relay optical system 30 also serves as this field lens.

The cross dichroic prism 50 serving as the color combining optical system forms a color image by combining images modulated for each color light emitted from the three liquid crystal panels 41R, 41G, and 41B. In the cross dichroic prism 50, a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a substantially X shape along the interfaces of four right-angle prisms. Three color lights are synthesized by the body multilayer film.
The projection lens 60 is composed of a lens unit composed of a plurality of combined lenses, and has a function of enlarging and projecting a color image synthesized by the cross dichroic prism 50 on a screen.

In the projector 1 having such a structure, the polarizing plate 42 disposed on the incident side of the liquid crystal panels 41R, 41G, and 41B is formed on the substrate 421 and the substrate 421 as shown in FIGS. A birefringent portion 422 and a protective substrate 423 arranged to cover the birefringent portion 422 are provided.
The substrate 421 is made of quartz glass having a linear expansion coefficient of 4.8 × 10 ⁻⁷ / K and a thermal conductivity of 1.35 W / (m · K), and a birefringent portion 422 is formed on the light exit surface thereof. Although not shown, an antireflection film is formed on the light incident surface.
By adopting quartz glass as the material of the substrate 421, internal absorption of light can be suppressed to 0.1% or less, and by forming an antireflection film, interface reflection can be suppressed to 0.5% or less. The light transmittance of the substrate 421 is 98.9% (100% −0.1% −0.5% × 2) or more.

  As shown in FIGS. 4 and 5, the birefringent portion 422 formed on the light emitting surface of the substrate 421 is formed on substantially the entire surface of the substrate 421, and the ribs 422 </ b> A serving as fine aluminum protrusions are striped. The polarization conversion is performed in a space between the ribs 422A. The rib 422A constituting the birefringent portion 422 has a width dimension W of approximately 65 nm, a height dimension H of 120 to 170 nm, and an arrangement pitch P of approximately 144 nm. By adjusting these W, H, and P, polarization can be obtained. The polarization characteristics of the plate 42 can be changed.

The protective substrate 423 has substantially the same shape as the substrate 421, and as shown in FIG. 3, the birefringent portion formed on the substrate 421 is bonded to the substrate 421 with a silicone-based adhesive 424 at the periphery thereof. 422 is hermetically sealed with a silicone adhesive 424 and a protective substrate 423. In order to dispose the above-described substrate 421 on the light incident side, the protective substrate 423 is disposed on the light emission side. Although not shown, the protective substrate 423 has antireflection films formed on the light incident surface and the light emitting surface. Here, the thickness d (mm) of the protective substrate through which the luminous flux after selection of the polarized light passes, the photoelastic constant B (10 ⁻¹² / Pa) of the material used as the protective substrate, Young's modulus E (Pa), The relationship between the linear expansion coefficient α (1 / K) and the thermal conductivity ρ (W / (m · K)) is expressed by the above [Equation 2].

For example, when quartz glass is used as the material for the protective substrate, the photoelastic constant of quartz glass B = 3.61 × 10 ⁻¹² / Pa), Young's modulus E = 7.3 × 10 10 Pa, linear expansion coefficient α = 4.8 × 10 ⁻⁷ / K, thermal conductivity ρ = 1.35 W / (m · K), and the thickness d ≦ 1 mm from the [Equation 2], and a protective substrate of up to about 1 mm can be obtained.
Further, the silicone-based adhesive 424 is of the unreacted oil component suppression type, and when the substrate 421 and the protective substrate 423 move differently due to heating or the like, the deformation is absorbed by the silicone-based adhesive 424 portion. .
Further, a spacer 425 is interposed between the substrate 421 and the protective substrate 423, and the protective substrate 423 is disposed in a state of being spaced apart from the birefringent portion 422 by a certain distance. The spacer 425 is obtained by curing an ultraviolet curable adhesive.

Next, a method for manufacturing such a polarizing plate 42 will be described.
First, an ultraviolet curable adhesive is applied to the peripheral portion of the protective substrate 423 in the form of dots, and an ultraviolet curable adhesive is applied to the substrate 421 with the application surface facing the formation surface of the birefringent portion 422 of the substrate 421. Adhere.
Next, after separating the two substrates 421 and 423 to a design distance, the adhesive surface is irradiated with ultraviolet rays and cured to maintain the distance between the substrates 421 and 423.
Finally, a silicone adhesive 424 is applied to the peripheral portions of both substrates 421 and 423 to cure the silicone adhesive 424.

According to this embodiment, there are the following effects.
That is, since the substrate 421 is disposed on the incident side, the light beam after selection of the polarized light is not affected by the thermal distortion of the substrate 421, and the polarization axis does not rotate, so that appropriate polarized light is selected. It can be performed. In addition, by adopting quartz glass having a low linear expansion coefficient as a substrate material, distortion hardly occurs even when heat absorbed by the birefringent portion 422 acts on the substrate material. Can be prevented. Furthermore, since the birefringent portion 422 is made of metal, sufficient durability can be ensured.

In addition, since the protective substrate 423 that covers the birefringent portion 422 is provided and the birefringent portion 422 is hermetically sealed by the silicone adhesive 424 and the protective substrate 423, deterioration of the rib 422A can be prevented. The durability of the plate 42 can be further improved, and the polarizing plate 42 does not deteriorate even when the projector 1 is exposed to a high temperature and high humidity environment during transportation or is used in a high temperature and high humidity environment.
Further, by forming an antireflection film on the light incident surface of the substrate 421 and the light incident / exit surface of the protective substrate 423, the light utilization rate can be improved and unnecessary reflected light on the transmission surface can be prevented. And S / N of the signal can be improved.

Then, since the substrate 421 and the protective substrate 423 are bonded at the peripheral portion where the birefringent portion 422 is not formed, the space between the ribs 422A can be prevented from being filled with an adhesive, Appropriate polarization conversion can be performed in the space, and the polarizing plate 42 can be optically excellent.
Further, since the unreacted oil component suppression type silicone adhesive 424 is used, it is possible to prevent the solvent from seeping out between the ribs 422A after the bonding.
Further, by making the protective substrate 423 substantially the same shape as the substrate 421, the size of the polarizing plate 42 can be made the minimum size necessary for polarization conversion, and therefore the polarizing plate 42 can be miniaturized. Can do.
In addition, since the protective substrate 423 is disposed on the exit side of the polarizer, the light beam selected by the polarizer passes, so that the influence of thermal stress on the light beam after polarization selection is greater than that of the substrate 421. Therefore, by making the thickness d of the protective substrate 423 satisfy the above [Equation 2], the optical distortion due to the thermal stress of the protective substrate can be minimized. In particular, when quartz glass or neo-serum is used, the thickness can be increased to about 1 mm by setting under the condition of [Equation 2], and the protective substrate with sufficient strength without causing the influence of optical distortion. Which is very advantageous. Moreover, what is necessary is just to select board | substrate thickness so that [Equation 2] may be satisfied also about another material.

Next, a second embodiment of the present invention will be described. In the following description, the same parts as those already described are denoted by the same reference numerals and the description thereof is omitted.
In the polarizing plate 42 according to the first embodiment, the protective substrate 423 has substantially the same shape as the substrate 421, and the bonding with the silicone-based adhesive 424 is performed on the end surface portions of both the substrates 421 and 423.

On the other hand, the polarizing plate 52 according to the second embodiment is different in that the protective substrate 523 is set larger than the substrate 521 as shown in FIGS. 6 and 7.
The adhesion between the substrate 521 and the protective substrate 523 is performed by the silicone adhesive 424 on the end surface of the substrate 521 and the surface portion of the protective substrate 523, and the amount of the silicone adhesive 424 increases the amount of application to the protective substrate 523. Can be set arbitrarily.

In the polarizing plate 42 according to the first embodiment, the substrate 421 and the protective substrate 423 are made of quartz glass.
In contrast, the polarizing plate 52 according to the second embodiment is different in that the material of the substrate 521 and the protective substrate 523 is sapphire. Although illustration is omitted, an antireflection film is formed on the light incident surface of the substrate 521 and the light incident / exit surface of the protective substrate 523, and a light transmittance of 97% or more is ensured.

Although sapphire has a high linear expansion coefficient of 53 × 10 −7 / K, it is characterized by a very high thermal conductivity of 42 W / (m · K).
When such a polarizing plate 52 is arranged on the optical path of the projector 1, the polarizing plate 52 is attached to a holding frame such as a metal plate, a heat dissipation path is formed, and the heat absorbed by the birefringent portion 422 is absorbed. It is preferable to radiate heat from the holding frame through the substrate 521 or the protective substrate 523.

According to the second embodiment, in addition to the effects described in the first embodiment, there are the following effects.
That is, by adopting sapphire having a high thermal conductivity as the material of the substrate 521 and the protective substrate 523, even if the heat absorbed by the birefringent portion 422 acts on the substrate 521 and the protective substrate 523, the holding frame or the like is interposed. Therefore, heat distortion is unlikely to occur in the substrate 521 and the protective substrate 523, and the light leakage phenomenon of the polarizing plate 52 can be prevented.

In addition, since the protective substrate 523 has a shape larger than that of the substrate 521, the end surface of the substrate 521 and the surface of the protective substrate 523 can be bonded with the silicone-based adhesive 424. In addition, the two substrates 521 and 523 can be firmly attached, and the amount of the adhesive can be increased to improve the internal sealing performance.
Further, the polarizing plate 52 can be accurately positioned using the outer shape of the protective substrate 523.

Next, a third embodiment of the present invention will be described.
As shown in FIGS. 8 and 9, the polarizing plate 62 of the third embodiment is set so that the protective substrate 623 is larger than the substrate 621, and the second embodiment is that the material of each substrate is sapphire. Although different from the polarizing plate 52, the spacer 625 interposed between the substrate 621 and the protective substrate 623 is a double-sided tape.

The spacer 625 is provided over the entire circumference of the birefringent portion 422 and is attached from the surface of the birefringent portion 422 on the protective substrate 623 side to the light emitting surface of the substrate 621. By disposing the protective substrate 623 on the spacer 625, the protective substrate 623 and the birefringent portion 422 are separated from each other by a certain distance.
Although not shown, the spacer 625, which is a double-sided tape, has a first surface that contacts the protective substrate 623 and a second surface that contacts the substrate 621 formed of a silicone-based adhesive, and the first surface and the second surface (front surface). The back surface is an elastic adhesive surface. A glass cloth support is provided between the first surface and the second surface. This double-sided tape has a thickness of about 0.15 mm, an adhesive strength of 11.77 N / 20 mm, and a shearing adhesive strength of 196.1 N / 4 cm ² .
The double-sided tape is not limited to this configuration, and the first surface and the second surface may be made of an acrylic resin, and the support may be made of a nonwoven fabric. Furthermore, you may use what does not have a support body. If one without a support is used, the thickness of the spacer can be reduced, so that the polarizing plate can be made thinner. Table 1 shows examples of double-sided tapes that can be used as spacers.

Next, a method for manufacturing such a polarizing plate 62 will be described.
First, a double-sided tape is attached around the birefringent portion 422 of the substrate 621. At this time, the end portion of the double-sided tape is placed on the surface of the birefringent portion 422 on the protective substrate 623 side.
Next, a protective substrate 623 is attached to the first surface of the double-sided tape.
Further, the end surface of the substrate 621 and the surface portion of the protective substrate 623 are bonded with a silicone-based adhesive 424.

According to the third embodiment, in addition to the effects described in the first embodiment and the second embodiment, there are the following effects.
That is, since the spacer 625 is a double-sided tape, the spacer 625 can be installed simply by attaching the double-sided tape, so that the mounting workability of the spacer 625 is improved.
Further, since the double-sided tape is attached to the entire periphery of the birefringent portion 422, even if the unreacted oil component oozes out from the silicone-based adhesive 424 to which the protective substrate 623 and the substrate 621 are bonded, the double-sided tape is blocked by the double-sided tape. The birefringent portion 422 is not soiled by the reaction oil component.
The first surface and the second surface of the spacer 625 are silicone-based pressure-sensitive adhesives, and since silicone has good UV resistance of the bonding surface, there is no possibility of deterioration due to UV rays.
Further, since the heat resistance is also good, there is no possibility that the heat is absorbed by the birefringent portion 422 and deformation or the like occurs.
Further, a glass cloth support is provided between the first surface and the second surface of the spacer 625, and appropriate rigidity is generated in the spacer 625. Therefore, workability when attaching the spacer 625 is good. Become.

Note that the present invention is not limited to the above-described embodiments, and includes modifications as described below.
In the embodiment, the structural birefringent polarizing plate 42 is used as the polarizing plate disposed on the incident side of the liquid crystal panels 41R, 41G, and 41B. Alternatively, a structural birefringent polarizing plate may be employed. In this case, the rib 422A constituting the birefringent portion 422 is not made of aluminum that reflects a polarized light beam that does not transmit, but is a rib that absorbs light such as black, so that a polarizing plate disposed on the emission side Can be used.

  In the first embodiment, quartz glass is employed as a material having a low linear expansion coefficient. However, the present invention is not limited to this, and optical glass or crystallized glass may be employed. In the third embodiment, sapphire glass is used as the material with high thermal conductivity, but quartz may be used. In short, depending on the degree of heating of the polarizer, the material with low linear expansion coefficient or high thermal conductivity. May be appropriately selected. When optical glass is used for the protective substrate, the thickness dimension of the protective substrate is preferably about 0.1 mm.

Furthermore, in the said embodiment, although the material of the board | substrates 421,521,621 and the protective substrates 423,523,623 was selected from a viewpoint of a low linear expansion coefficient and high thermal conductivity, this invention is not limited to this. That is, an inorganic substance having a low photoelastic constant may be selected as the material of the substrate and the protective substrate, and a material having a photoelastic constant of 0.43 × 10 ⁻¹² / Pa or less is preferably used. Further, LBC3N manufactured by HOYA Optics, which is a low photoelastic glass, can be employed.
By adopting such a low photoelastic constant material, the optical path difference of the transmitted light can be reduced even if heat absorbed by the birefringent portion acts on the substrate, so that the occurrence of light leakage or the like can be prevented. .

  In the third embodiment, the spacer 625 that is a double-sided tape is used for the polarizing plate 62 in which the protective substrate 623 is formed larger than the substrate 621. However, like the polarizing plate 42 of the first embodiment, The spacer 625 may be used when the substrate 421 is substantially the same size.

In the embodiment, the present invention is adopted as the polarizing plates 42, 52, 62 of the liquid crystal panels 41R, 41G, 41B of the projector 1, but the present invention is not limited to this. That is, the polarizers according to the present invention may be used for other optical devices, and even if the polarizer according to the present invention is adopted for a light modulation device other than a liquid crystal device, the functions and effects described in the above embodiment are obtained. Similar actions and effects can be enjoyed.
In addition, the specific structure, material, and the like when implementing the present invention may be other structures as long as the object of the present invention can be achieved.

It is a schematic diagram showing the structure of the projector which concerns on 1st Embodiment of this invention. It is a general | schematic perspective view showing the structure of the polarizer in the said embodiment. It is sectional drawing showing the structure of the polarizer in the said embodiment. It is a front view showing the birefringence part of the polarizer in the said embodiment. It is a fragmentary perspective view showing the structure of the birefringent part of the polarizer in the said embodiment. It is a general | schematic perspective view showing the structure of the polarizer which concerns on 2nd Embodiment of this invention. It is sectional drawing showing the structure of the polarizer in the said embodiment. It is a general | schematic perspective view showing the structure of the polarizer which concerns on 3rd Embodiment of this invention. It is sectional drawing showing the structure of the polarizer in the said embodiment.

Explanation of symbols

1 Projector 41R, 41G, 41B Liquid crystal panel (electro-optic element)
42, 52, 62 Polarizing plate (polarizer)
421, 521, 621 Substrate 422 Birefringent portion 422A Rib (protruded portion)
423, 523, 623 Protective substrate 424 Silicone adhesive (elastic adhesive)
425, 625 spacer

Claims (25)

An electro-optic element that modulates a light beam emitted from a light source according to image information; and a polarizer disposed on a light incident side and / or a light emission side of the electro-optic element,
The electro-optic element includes a pair of substrates and an electro-optic material sandwiched between the pair of substrates,
The polarizer is a birefringence composed of a polarizer substrate made of a material having a light transmittance of 97% or more and fine metal protrusions arranged in a stripe pattern on the surface of the polarizer substrate. An optical instrument comprising a portion,
The birefringence portion is provided on the light exit side of the two surfaces of the polarizer substrate,
The birefringent part is provided with a protective substrate covering the birefringent part,
The optical device, wherein the protective substrate is bonded to the polarizer substrate by an elastic adhesive at an outer peripheral end portion, and the birefringent portion is sealed with the protective substrate and the elastic adhesive. The optical instrument according to claim 1,
The optical substrate, wherein the polarizer substrate is made of a material having a linear expansion coefficient of 4.8 × 10 ⁻⁷ / K or less. The optical apparatus according to claim 2,
The optical device, wherein the polarizer substrate is made of crystallized glass. The optical apparatus according to claim 3.
The optical device, wherein the polarizer substrate is made of quartz glass. The optical instrument according to claim 1,
The optical substrate, wherein the polarizer substrate is made of a material having a thermal conductivity of 6.21 W / (m · K) or more. The optical apparatus according to claim 5, wherein
The optical device, wherein the polarizer substrate is made of sapphire. The optical apparatus according to claim 5, wherein
The optical device, wherein the polarizer substrate is made of quartz. The optical instrument according to claim 1,
The optical substrate, wherein the polarizer substrate is made of a material having a photoelastic constant of 0.43 × 10 ⁻¹² / Pa or less. In the optical apparatus according to any one of claims 1 to 8,
An optical apparatus, wherein an antireflection treatment is applied to a light incident surface of the polarizer substrate. The optical apparatus according to any one of claims 1 to 9,
The optical device, wherein the protective substrate is made of a material having a light transmittance of 97% or more. In the optical apparatus in any one of Claims 1-10,
The optical substrate, wherein the protective substrate is made of a material having a linear expansion coefficient of 4.8 × 10 ⁻⁷ / K or less. In the optical apparatus in any one of Claims 1-10,
The optical device, wherein the protective substrate is made of a material having a thermal conductivity of 6.21 W / (m · K) or more. In the optical apparatus in any one of Claims 1-10,
An optical apparatus, wherein the protective substrate is made of a material having a photoelastic constant of 0.43 × 10 ⁻¹² / Pa or less. In the optical apparatus in any one of Claims 1-10,
The thickness of the protective substrate is d (mm), the photoelastic constant is B (10 ⁻¹² / Pa), the Young's modulus is E (Pa), the linear expansion coefficient is α (1 / K), and the thermal conductivity is ρ ( W / (m · K)), an optical apparatus represented by the following formula: B × E × α / ρ × d ≦ 9.8 × 10 ⁻⁵ (m ² / W) In the optical instrument in any one of Claims 1-14,
An optical apparatus, wherein an antireflection treatment is applied to a light incident / exit surface of the protective substrate. The optical apparatus according to any one of claims 1 to 15,
The optical apparatus is characterized in that the elastic adhesive is a silicone-based adhesive. The optical instrument according to claim 16, wherein
2. The optical apparatus according to claim 1, wherein the elastic adhesive is an unreacted oil component suppression type silicone adhesive. The optical apparatus according to any one of claims 1 to 17,
The optical device, wherein the protective substrate has substantially the same shape as the polarizer substrate. The optical apparatus according to any one of claims 1 to 17,
The optical device, wherein the protective substrate has a shape larger than that of the polarizer substrate. In the optical apparatus in any one of Claims 1-19,
An optical apparatus, wherein a spacer is interposed between the polarizer substrate and the protective substrate. The optical instrument according to claim 20,
The optical device is characterized in that the spacer is made of a photocurable adhesive. The optical instrument according to claim 20,
The optical device according to claim 1, wherein the spacer is a double-sided tape whose front and back surfaces are elastic adhesive surfaces. The optical instrument according to claim 22,
An optical apparatus, wherein an adhesive surface of the spacer is made of a silicone-based adhesive. The optical instrument according to claim 23.
The said spacer has the support body which consists of a woven fabric or a nonwoven fabric, The adhesive surface to which the silicone type adhesive was apply | coated is provided in the front and back of the said support body, The optical apparatus characterized by the above-mentioned. The optical instrument according to claim 23.
The optical device is characterized in that the spacer is made of only a silicone-based adhesive.

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