Optical device

Abstract

Provided is an optical device capable of switching between a state in which light is reflected and a state in which light is emitted, and capable of suppressing a decrease in display quality of a light reflection image. The optical device includes: a light emitting device having a light emitting surface; an absorption polarizing plate disposed opposite the light emitting surface of the light emitting device; a liquid crystal optical element disposed between the light emitting device and the absorption polarizing plate; a reflection polarizing plate disposed between the light emitting device and the liquid crystal optical element; and a bonding layer provided on a surface of the reflection polarizing plate facing the light emitting device.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical device capable of switching between a state functioning as a mirror and a state functioning as a display device. BACKGROUND

[0002] A device capable of switching between a state functioning as a mirror (also referred to as a state displaying a mirror image or a state reflecting external light) and a state functioning as a display device (also referred to as a state displaying a prescribed image or a state emitting display light) is disclosed in Patent Literature 1. The device is provided with a display device that displays a prescribed image, an absorbing polarizing plate that is disposed opposite the display device, a liquid crystal optical element that is disposed between the display device and the absorbing polarizing plate, and a reflecting polarizing plate that is disposed between the display device and the liquid crystal optical element.

[0003] [Patent Literature]

[0004] [Patent Literature]

[0005] [Patent Literature 1] Japanese Patent No. 3419766 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] In the device disclosed in Patent Literature 1, the display quality of the mirror image can be greatly reduced due to the fixing method of the reflecting polarizing plate.

[0008] The present disclosure was achieved in view of the above problem, and a main object thereof is to suppress reduction in display quality of a light reflection image in an optical device capable of switching between a state reflecting light and a state emitting light.

[0009] [Means for Solving the Problems]

[0010] To solve the above problem, an optical device according to an embodiment of the present disclosure is capable of switching between a state emitting light and a state reflecting light, and includes a light emitting device having a light emitting surface, an absorbing polarizing plate disposed opposite the light emitting surface of the light emitting device, a liquid crystal optical element disposed between the light emitting device and the absorbing polarizing plate, a reflecting polarizing plate disposed between the light emitting device and the liquid crystal optical element, and an adhesive layer provided on a surface of the reflecting polarizing plate facing the light emitting device.

[0011] [Effects of the Invention]

[0012] According to the optical device having the above structure, reduction in display quality of a light reflection image can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a cross-sectional view schematically showing an optical device of a comparative example.

[0014] Figure 2 is a microscope photograph showing a defect that can occur in a light reflection image in the comparative example.

[0015] Figure 3 is a cross-sectional view schematically showing an optical device of a first embodiment.

[0016] Figure 4 is a cross-sectional view schematically showing an optical device of a second embodiment.

[0017] Figure 5 is a cross-sectional view schematically showing an optical device of a third embodiment.

[0018] Figure 6 is a cross-sectional view schematically showing an optical device of a modification of the first embodiment.

[0019] Explanation of Reference Numerals

[0020] 10 light-exit device (organic EL display device)

[0021] 11 light-exit surface (display surface)

[0022] 21 reflection-type polarizing plate

[0023] 22 absorption-type polarizing plate

[0024] 30 liquid crystal optical element

[0025] 31f front substrate

[0026] 31b rear substrate

[0027] 32f front electrode

[0028] 32b rear electrode

[0029] 33f front alignment film

[0030] 33b rear alignment film

[0031] 34 liquid crystal layer

[0032] 40 cover member

[0033] 51 to 54 adhesive layer

[0034] 60 light-transmitting plate

[0035] 70 light-exit device

[0036] 71 liquid crystal display element

[0037] 72 light source

[0038] 73 polarizing film

[0039] 81, 82 optical film

[0040] 100 optical device (comparative example)

[0041] 101 optical device (first embodiment)

[0042] 102 optical device (second embodiment)

[0043] 103 optical device (third embodiment)

[0044] 200 control device DETAILED DESCRIPTION

[0045] (comparative example)

[0046] Before explaining the embodiments of the present disclosure, the basic structure and function of an optical device capable of switching between a state in which it functions as a mirror and a state in which it functions as a display device are described with reference to a comparative example. Note that such an optical device is, for example, generally used as a mirror, and can be used as a vehicle interior mirror, a side mirror, or the like, which displays the vehicle interior temperature, the vehicle speed, or the like, when necessary.

[0047] Figure 1 An optical device 100 of the comparative example is shown. With reference to Figure 1 , the structure of the optical device 100 is first described, and then the function and operation thereof are described.

[0048] Here, for convenience, an XYZ orthogonal coordinate system composed of an X axis and a Y axis that constitute a plane parallel to the horizontal plane, and a Z axis orthogonal to the X axis and the Y axis is set. In linearly polarized light (electromagnetic waves) that travel along the X axis, linearly polarized light in which the electric field (or the magnetic field) vibrates along the Y axis is referred to as Y-polarized light, and linearly polarized light in which the electric field (or the magnetic field) vibrates along the Z axis is referred to as Z-polarized light.

[0049] The optical device 100 has a structure in which the following components are sequentially arranged: a display device 10 that displays characters, images, or the like; a reflection-type polarizing plate 21 that reflects, for example, Y-polarized light and transmits Z-polarized light; a liquid crystal optical element 30 that can rotate the vibration direction (polarization direction) of the electric field and the magnetic field in polarized light; an absorption-type polarizing plate 22 that, for example, absorbs Y-polarized light and transmits Z-polarized light; and a cover member 40 composed of a glass member having light-transmitting properties.

[0050] The display device 10 corresponds to a light-emitting device, and is, for example, a display device using an organic EL (electro-luminescence) element. Whether or not an image is displayed on the display surface 11 of the display device 10, that is, whether or not display light Ld is emitted from the display surface 11, is controlled by the control device 200.

[0051] In addition, the display device 10 is sometimes referred to as a light-emitting device that emits display light Ld. In addition, the display surface 11 is sometimes referred to as a light-emitting surface.

[0052] As the reflective polarizing plate 21, for example, a wire grid type, a multilayer film type, or the like can be used. The reflective polarizing plate 21 is disposed, for example, with its reflective axis along the Y axis and its transmissive axis along the Z axis. In a comparative example, the reflective polarizing plate 21 is bonded to the liquid crystal optical element 30 (rear substrate 31b) via the adhesive layer 51.

[0053] The liquid crystal optical element 30 is an optical element that can rotate the polarization direction of polarized light. Specifically, for example, it is an optical element that can transform Z-polarized light into Y-polarized light. Whether or not the polarization direction of polarized light that has passed through the liquid crystal optical element 30 is rotated is controlled by the control device 200.

[0054] The liquid crystal optical element 30 mainly includes: a pair of a rear substrate 31b and a front substrate 31f; a rear electrode 32b and a front electrode 32f provided on respective opposing surfaces of the rear substrate 31b and the front substrate 31f; a rear alignment film 33b and a front alignment film 33f provided on respective opposing surfaces of the rear electrode 32b and the front electrode 32f; and a liquid crystal layer 34 interposed between the rear alignment film 33b and the front alignment film 33f and containing liquid crystal molecules whose refractive index (dielectric constant) differs depending on the direction.

[0055] The rear substrate 31b and the front substrate 31f use, for example, a glass substrate having light-transmitting properties. The rear electrode 32b and the front electrode 32f use, for example, a conductive member containing indium tin oxide and having light-transmitting properties.

[0056] The rear alignment film 33b and the front alignment film 33f use, for example, polyimide and are subjected to uniaxial alignment treatment (e.g., rubbing treatment). The rear alignment film 33b is subjected to uniaxial alignment treatment along, for example, the Y axis, and the front alignment film 33f is subjected to uniaxial alignment treatment along, for example, the Z axis.

[0057] The liquid crystal layer 34 uses, for example, a twisted nematic type liquid crystal material.

[0058] When no voltage is applied to the liquid crystal layer 34 (normal state), liquid crystal molecules located near the rear alignment film 33b are oriented along the Y axis, and liquid crystal molecules located near the front alignment film 33f are oriented along the Z axis. Also, liquid crystal molecules located between the rear alignment film 33b and the front alignment film 33f are oriented in a manner twisted by about 90° from the rear alignment film 33b toward the front alignment film 33f.

[0059] When a voltage is applied to the liquid crystal layer 34 via the rear electrode 32b and the front electrode 32f (driven state), liquid crystal molecules oriented in a manner substantially parallel to the YZ plane are oriented along the X axis. That is, the liquid crystal molecules stand up in a manner substantially perpendicular to the rear electrode 32b and the front electrode 32f.

[0060] In the normal state, the liquid crystal optical element 30 rotates the polarization direction of the transmitted polarized light. That is, for example, when Z-polarized light is incident, Y-polarized light is emitted. Also, in the driven state, the liquid crystal optical element 30 does not rotate the polarization direction of the transmitted polarized light. That is, for example, when Z-polarized light is incident, Z-polarized light is still emitted.

[0061] As the absorption-type polarizing plate 22, for example, a dye-based, iodine-based, or the like polarizing plate can be used. The absorption-type polarizing plate 22 is disposed, for example, in a manner that its absorption axis is along the Y axis and its transmission axis is along the Z axis. In the comparative example, the absorption-type polarizing plate 22 is adhered to the liquid crystal optical element 30 (front substrate 31f) via the adhesive layer 52.

[0062] The adhesive layers 51, 52 are composed of an adhesive having light-transmitting properties. The thickness of the adhesive layers 51, 52 is, for example, about 5 to 10 μ m.

[0063] Next, the function and operation of the optical device 100 of the comparative example will be described. First, the case where the optical device 100 functions as a display device will be described, and then the case where it functions as a mirror will be described.

[0064] The optical device 100 causes an image to be displayed on the display surface 11 of the display device 10, and functions as a display device when the liquid crystal optical element 30 is in the driven state by applying a voltage to the liquid crystal layer 34.

[0065] When the display light Ld emitted from the display device 10 is incident on the reflective polarizer 21, only the Z-polarized light in the display light Ld transmits the reflective polarizer 21. When the Z-polarized light that has transmitted the reflective polarizer 21 is incident on the liquid crystal optical element 30 in the driven state, the polarization direction of the Z-polarized light is not rotated, and the Z-polarized light directly transmits the liquid crystal optical element 30. The Z-polarized light that has transmitted the liquid crystal optical element 30 transmits the absorptive polarizer 22 and the cover member 40, and reaches the observer. Thus, the observer can recognize the display light Ld emitted from the display device 10, that is, the image displayed on the display surface 11.

[0066] On the other hand, the optical device 100 functions as a mirror when the image is not displayed on the display surface 11 of the display device 10, and the liquid crystal optical element 30 is in the normal state without applying a voltage to the liquid crystal layer 34.

[0067] When the external light Lo that has transmitted the cover member 40 is incident on the absorptive polarizer 22, only the Z-polarized light in the external light Lo transmits the absorptive polarizer 22. When the Z-polarized light that has transmitted the absorptive polarizer 22 is incident on the liquid crystal optical element 30 in the normal state, particularly the liquid crystal layer 34 thereof, the Z-polarized light is converted into Y-polarized light, and transmits the liquid crystal layer 34.

[0068] When the Y-polarized light that has been converted by the liquid crystal layer 34 is incident on the reflective polarizer 21, the Y-polarized light is reflected by the reflective polarizer 21. When the Y-polarized light that has been reflected by the reflective polarizer 21 is incident on the liquid crystal layer 34, the Y-polarized light is again converted into Z-polarized light. The Z-polarized light that has been converted again by the liquid crystal layer 34 transmits the absorptive polarizer 22 and the cover member 40, and reaches the observer. Thus, the observer can recognize a light reflection image (mirror image) obtained by reflection of the reflective polarizer 21.

[0069] The light reflection image obtained by reflection of the reflective polarizer 21 is preferably free from distortion, defects, and the like. However, when the reflective polarizer 21 is bonded to the liquid crystal optical element 30 via the adhesive layer 51, a foreign matter such as a stain, dust, or the like can sometimes be mixed between the reflective polarizer 21 and the liquid crystal optical element 30 (i.e., between the adhesive layer 51 and the back substrate 31b), and the foreign matter is observed as a defect of the light reflection image.

[0070] Figure 2The state in which a defect of a light reflection image that occurs when a foreign matter is mixed between the reflective polarizing plate 21 and the liquid crystal optical element 30 is shown from the liquid crystal optical element 30 side in the comparative example. If a foreign matter is mixed between the reflective polarizing plate 21 and the liquid crystal optical element 30, a portion in which the adhesive layer 51 is relatively thick or thin, a portion in which the reflective polarizing plate 21 or the liquid crystal optical element 30 is peeled from the adhesive layer 51 (a bubble is mixed), or the like is generated around the foreign matter. As a result, a defect of a size of 10 times or more that of the foreign matter can occur in the light reflection image.

[0071] In the optical device 100, it is preferable to suppress the occurrence of such a defect, and it is preferable to suppress the size of the defect at least to the same degree as the size of the foreign matter so that the defect is not noticeable. Hereinafter, as an embodiment, an optical device in which such a defect of a light reflection image is made unnoticeable is described.

[0072] (First Embodiment)

[0073] Figure 3 The structure of the optical device 101 of the first embodiment is shown. The optical device 101 of the first embodiment has the same configuration and components as the optical device 100 of the comparative example except for the fixing method of the reflective polarizing plate 21.

[0074] In the optical device 101, the reflective polarizing plate 21 is adhered to the display surface 11 of the display device 10. The adhesive layer 53 is provided on the surface of the reflective polarizing plate 21 that faces the display device 10, and the reflective polarizing plate 21 and the display device 10 are adhered by the adhesive layer 53.

[0075] In the first embodiment, the polarized light reflected by the reflective polarizing plate 21 does not pass through the adhesive interface of the reflective polarizing plate 21 and the display device 10, or the adhesive layer 53 that adheres them. Therefore, even in the case where a foreign matter is mixed between the reflective polarizing plate 21 and the display device 10, a defect corresponding to the foreign matter, a bubble of the adhesive layer 53 caused by the mixing of the foreign matter, or the like does not occur in the light reflection image.

[0076] Thus, by providing the adhesive layer 53 on the surface of the reflective polarizing plate 21 that faces the display device 10, it is possible to reduce the influence of a foreign matter that can be mixed into the adhesive layer 53 on the light reflection image. As a result, it is difficult to make a defect of the light reflection image that occurs in association with the mixing of the foreign matter noticeable, and it is possible to suppress the reduction in the display quality of the light reflection image.

[0077] (Second Embodiment)

[0078] In the first embodiment, the reflective polarizing plate 21 is attached to the display device 10. However, the reflective polarizing plate 21 can also be attached to a light-transmitting plate prepared separately. Hereinafter, as a second embodiment, an optical device in which the reflective polarizing plate 21 is attached to a light-transmitting plate will be described.

[0079] Figure 4 The configuration of the optical device 102 of the second embodiment will be described. The optical device 102 of the second embodiment has the same configuration and components as the optical device 101 of the first embodiment except for the fixing method of the reflective polarizing plate 21.

[0080] In the optical device 102, the reflective polarizing plate 21 is attached to the light-transmitting plate 60. An adhesive layer 53 is provided on the surface of the reflective polarizing plate 21 facing the display device 10, and the reflective polarizing plate 21 and the light-transmitting plate 60 are attached by the adhesive layer 53.

[0081] The light-transmitting plate 60 is composed of, for example, a glass member having light-transmitting properties. Note that the light-transmitting plate 60 can be any member as long as it has light-transmitting properties and can support the reflective polarizing plate 21.

[0082] The reflective polarizing plate 21 can also be fixed in this way. Note that by using a light-transmitting plate 60 having a relatively large thickness, the rigidity (resistance to deformation or flexure) of the optical device 102 as a whole can be improved.

[0083] (Third Embodiment)

[0084] In the first and second embodiments, the display device 10 using an organic EL element is exemplified as a unit that displays an image desired to be displayed. However, a light-emitting device including a liquid crystal display element can also be used as a unit that displays an image desired to be displayed. Hereinafter, as a third embodiment, an optical device using a light-emitting device including a liquid crystal display element will be described.

[0085] Figure 5 The configuration of the optical device 103 of the third embodiment will be described. The optical device 103 of the third embodiment has the same configuration and components as the optical device 101 of the first embodiment except for the point that the display device 10 is replaced by a light-emitting device 70.

[0086] In the optical device 103, the light-emitting device 70 is used instead of the display device 10. The light-emitting device 70 includes a liquid crystal display element 71 attached to the reflective polarizing plate 21, a light source 72 that irradiates light to the liquid crystal display element 71, and a polarizing film 73 disposed between the liquid crystal display element 71 and the light source 72.

[0087] The liquid crystal display element 71 has an electrode structure of a 7-segment type, a dot matrix type, or the like, and is driven by a driving method of VA (Vertical Alignment), IPS (In Plane Switching), or the like. The polarizing film 73 is disposed, for example, in a manner that crosses the Nicol of the reflective polarizer 21, and the light exit device 70 functions as a unit for displaying an image in combination with the reflective polarizer 21.

[0088] In this way, the light exit device 70 that functions as a unit for displaying an image in combination with the reflective polarizer 21 can be used instead of the display device 10.

[0089] (Modified Example)

[0090] Figure 6 An optical device 104 according to a modified example of the first embodiment is shown. Note that the modified example can also be applied to the second embodiment and the third embodiment.

[0091] In the first embodiment, the reflective polarizer 21 is attached to the display device 10. In this case, an optical film 81 such as a viewing angle compensation film or an antiglare film can be attached to the liquid crystal optical element 30.

[0092] Generally, such an optical film 81 is attached to the liquid crystal optical element 30 while overlapping the reflective polarizer 21. The optical film 81 and the reflective polarizer 21 generally have flexibility or softness, and if they are attached while overlapping to the liquid crystal optical element 30, the flatness of the reflective polarizer 21 is impaired, and the light reflection image obtained by reflection of the reflective polarizer 21 can be distorted.

[0093] By attaching the optical film 81 and the reflective polarizer 21 to different members, it is possible to maintain the flatness of the reflective polarizer 21 and prevent distortion of the light reflection image obtained by reflection of the reflective polarizer 21. In addition, as the method of attaching the optical film, it is easier to attach the optical film 81 and the reflective polarizer 21 to different members than to attach them to the same member while overlapping.

[0094] Note that in the first embodiment, the absorptive polarizer 22 is attached to the liquid crystal optical element 30. However, the absorptive polarizer 22 can not be attached to the liquid crystal optical element 30, but can be attached to the cover member 40.

[0095] In this case, the optical film 82 such as a viewing angle compensation film, an antiglare film, or the like can be attached to the liquid crystal optical element 30. As described above, as the method of attaching the optical film, the method of attaching the optical film 82 and the absorption-type polarizing plate 22 to different members is easier than the method of attaching the optical film 82 and the absorption-type polarizing plate 22 to the same member in overlapping relation. Note that the absorption-type polarizing plate 22 can be attached to the liquid crystal optical element 30, and the optical film 82 can be attached to the cover member 40.

[0096] The present disclosure has been described above according to embodiments and modifications thereof, but the present disclosure is not limited to these. Various changes, modifications, combinations, and the like can be made by those skilled in the art.

Claims

1. An optical device capable of switching a state of emitting light and a state of reflecting light and functioning as a mirror, the optical device having: a light emitting device having a light emitting surface; an absorption type polarizing plate disposed opposite to the light emitting surface of the light emitting device; a liquid crystal optical element disposed between the light emitting device and the absorption type polarizing plate, provided with a liquid crystal layer that changes a polarization direction of a polarized light that is transmitted; a reflection type polarizing plate disposed between the light emitting device and the liquid crystal optical element; and a control device, the absorption type polarizing plate is disposed so that an absorption axis thereof is along one direction and a transmission axis thereof is along a direction orthogonal to the one direction in an in-plane direction of the absorption type polarizing plate, the reflection type polarizing plate is disposed so that a reflection axis thereof is along the one direction and a transmission axis thereof is along a direction orthogonal to the one direction in an in-plane direction of the reflection type polarizing plate, the light emitting device is a light emitting device capable of emitting display light containing an image, and when the display light is emitted from the light emitting surface, the light emitting device emits light containing a polarized component of a polarized light having a polarization direction identical to that of the transmission axis of the reflection type polarizing plate, the reflection type polarizing plate is bonded to the light emitting device by a bonding layer provided only on a surface side facing the light emitting device, and is not bonded to the liquid crystal optical element, the control device causes the display light emitted from the light emitting device to be emitted by sequentially passing through the bonding layer, the reflection type polarizing plate, the liquid crystal optical element, and the absorption type polarizing plate when the optical device emits light, the control device causes external light incident on the optical device to sequentially pass through the absorption type polarizing plate and the liquid crystal optical element, and causes light having a polarization component identical to that of the reflection axis of the reflection type polarizing plate to reach the reflection type polarizing plate without passing through the bonding layer and to be reflected, and the reflected light is emitted by sequentially passing through the liquid crystal optical element and the absorption type polarizing plate when the optical device reflects light, the control device controls light emission of the light emitting device and change of the polarization direction of the liquid crystal optical element.

2. The optical device according to claim 1, wherein the light emitting device is a display device using an organic electroluminescence element.

3. The optical device according to claim 1 or 2, wherein the reflection type polarizing plate is a polarizing plate of a wire grid type or a multilayer film type.

4. The optical device according to claim 1 or 2, wherein the optical device further has an optical film attached to a surface of the liquid crystal optical element facing the reflection type polarizing plate.

5. The optical device according to claim 3, wherein the optical device further has an optical film attached to a surface of the liquid crystal optical element facing the reflection type polarizing plate.

6. The optical device according to claim 1 or 2, wherein the optical device is an interior mirror or a side mirror for a vehicle.

7. The optical device according to claim 3, wherein the optical device is an interior mirror or a side mirror for a vehicle.

8. The optical device of claim 4, wherein, the optical device is an interior mirror or a side mirror for a vehicle.

9. The optical device of claim 5, wherein, the optical device is an interior mirror or a side mirror for a vehicle.

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