Patent Publication Number: US-10782555-B2

Title: Liquid crystal panel

Description:
CROSS REFERENCE 
     This application is the U.S. National Phase under 35 U.S.C § 371 of International Application No. PCT/JP2018/023385, filed on Jun. 20, 2018, which claims the benefit of Japanese Application No. 2017-122841, filed on Jun. 23, 2017, the entire contents of each are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a liquid crystal panel. 
     BACKGROUND ART 
     A liquid crystal panel described in Patent Document 1 includes a liquid crystal layer sealed between a pair of substrates, and an absorption type polarizing plate and a reflection type polarizing plate between which the pair of substrates is interposed, and the liquid crystal panel is switchable between a transmission state and a mirrored state (reflection state). In the transmission state, the liquid crystal panel of Patent Document 1 allows an object (an image display in Patent Document 1) located behind the liquid crystal panel to be visually recognized. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent No. 3419766 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the reflection state, this type of liquid crystal panel preferably has a high total light reflectance in view of the function as a mirror. In contrast, in the transmission state, the liquid crystal panel preferably has a low total light reflectance in view of the visibility of the back side. Therefore, there is a problem in making both compatible. 
     The present invention is made in view of the above circumstance, and an object of the present invention is to provide a liquid crystal panel that compatibly has an appropriate reflectance in a reflection state and an appropriate reflectance in a transmission state. 
     Solution to Problem 
     In order to achieve the above object, a liquid crystal panel in dispense to a first aspect of the present invention is switchable between a transmission state and a reflection state in response to application of voltage. The liquid crystal panel includes, a liquid crystal element including a liquid crystal layer and transparent electrodes to apply voltage to the liquid crystal layer, an absorption type polarizing plate provided at one side of the liquid crystal element, and a reflection type polarizing plate provided at the other side of the liquid crystal element and located opposed via the liquid crystal element to the absorption type polarizing plate. In the reflection state, light incident on the absorption type polarizing plate and transmitted through the liquid crystal element becomes light having a polarizing axis along a reflection axis of the reflection type polarizing plate, and is reflected on the reflection type polarizing plate. In the transmission state, light incident on the absorption type polarizing plate and transmitted through the liquid crystal element becomes light having a polarizing axis along a transmission axis intersecting with the reflection axis of the reflection type polarizing plate, and is transmitted through the reflection type polarizing plate. The absorption type polarizing plate has an average degree of polarization of 60% or greater and 80% or smaller at a wavelength of 450 nm to 650 nm. 
     Effect of the Invention 
     According to an aspect of the present invention, a liquid crystal panel that compatibly has an appropriate reflectance in a reflection state and an appropriate reflectance in a transmission state can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. 
         FIG. 2A  is an explanatory diagram illustrating a reflection state, and  FIG. 2B  is an explanatory diagram illustrating a transmission state. 
         FIG. 3A  is a chart illustrating a degree of polarization of an absorption type polarizing plate of each of liquid crystal panels A to E, a reflectance of each liquid crystal panel in a reflection state, and a reflectance of each liquid crystal panel in a transmission state, and  FIG. 3B  is a diagram illustrating the relationship between the degree of polarization of the absorption type polarizing plate, and the reflectance in the reflection state of the liquid crystal panel and the reflectance of the transmission state of the liquid crystal panel. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     An embodiment of the present invention will be described with reference to the drawings. 
     A liquid crystal panel  100  according to an embodiment of the present invention is a twisted nematic (TN) type liquid crystal panel and is structures as illustrated in a schematic cross-sectional view of  FIG. 1 . The liquid crystal panel  100  is structured to be switchable between a transmission state and a reflection state. As illustrated in  FIG. 2B , the liquid crystal panel  100  in the transmission state allows a displayed image on a display  200  disposed behind the liquid crystal panel to be transmitted and visually recognized by an observer  1 . In contrast, as illustrated in  FIG. 2A , the liquid crystal panel  100  in the reflection state functions as a mirror that reflects external light NL or the like toward the observer  1 . 
     Herein, for facilitating easy understanding of the descriptions, the side of the observer  1  of the liquid crystal panel  100  will be referred to as “the front side” and the opposite side of the observer  1  will be referred to as “the back side”, and components of the liquid crystal panel will be described. Further, in consideration of the visibility of the drawings, in  FIGS. 1 and 2A, 2B , hatching indicating cross sections is omitted as appropriate. Furthermore, in  FIGS. 2A and 2B  illustrating the function of the liquid crystal panel  100 , members are omitted as appropriate. 
     As illustrated in  FIG. 1 , the liquid crystal panel  100  includes a liquid crystal element  10 , an absorption type polarizing plate  21  located on the front side of the liquid crystal element  10 , and a reflection type polarizing plate  22  located on the back side of the liquid crystal element  10 . Though not illustrated, the liquid crystal panel  100  is formed, for example, in a substantially rectangular shape in planar view. 
     As illustrated in  FIG. 1 , the liquid crystal element  10  includes a first substrate  11 , a second substrate  12 , and a liquid crystal layer  13 . 
     The first substrate  11  and the second substrate  12  are pair of transparent substrates opposed to each other and are made of, for example, glass, plastic, or the like. The first substrate  11  and the second substrate  12  are arranged to face each other in a state where the liquid crystal layer  13  is interposed between the first substrate  11  and the second substrate  12  and in a state where main surfaces (opposed surfaces) of the first substrate  11  and the second substrate  12  are parallel to each other. The first substrate  11  is located on the front side of the liquid crystal layer  13 . 
     A transparent electrode  11   a  is provided on the liquid crystal layer  13  side of the first substrate  11 . A transparent electrode  12   a  is provided on the liquid crystal layer  13  side of the second substrate  12 . The transparent electrodes  11   a ,  12   a  are formed by a well-known technique such as sputtering, vapor deposition, or the like. In the present embodiment, each of the transparent electrodes  11   a ,  12   a  is formed in a solid shape on the corresponding substrate surface and has a substantially rectangular shape in planar view. The transparent electrodes  11   a ,  12   a  are formed of indiumtinoxide (ITO) films mainly including indium oxide or are formed of another material. Voltage may be applied via the transparent electrodes  11   a ,  12   a  to the liquid crystal layer  13  in a drive method of either a passive method or an active method. 
     Further, an insulating film (not illustrated) and an alignment film (not illustrated) are formed on each of the first substrate  11  and the second substrate  12 . The insulating film is made of a silicon-based insulating film and is formed to cover each of the transparent electrodes  11   a ,  12   a  from the liquid crystal layer  13 . Furthermore, the alignment film is formed between the insulating film and the liquid crystal layer  13 . That is, the transparent electrode  11   a , the insulating film, and the alignment film are stacked in layers on the first substrate  11 . In addition, the transparent electrode  12   a , the insulating film, and the alignment film are stacked in layers on the second substrate  12 . 
     The alignment film is in contact with the liquid crystal layer  13  and define an alignment state of the liquid crystal molecules  13   a  included in the liquid crystal layer  13  (schematically illustrated in  FIGS. 2A and 2B ), and the alignment film is made of, for example, polyimide by a known method (for example, flexographic printing). A rubbing process is applied to the alignment film. In the present embodiment, the rubbing direction of the alignment film on the front side (i.e., the alignment film formed on the first substrate  11 ) is substantially perpendicular (or just perpendicular) to the rubbing direction of the alignment film on the back side (i.e., the alignment film formed on the second substrate) as viewed in a normal direction of the substrates (in a normal direction of the opposed surfaces of the first substrate  11  and the second substrate  12 ). The alignment of the liquid crystal molecules  13   a  is regulated by the alignment films to which the rubbing process is applied as just described. The alignment process applied to the alignment films is not limited to the rubbing process. Alternatively, another known process such as a photo-alignment process, a protrusion alignment process, or the like may be applied to the alignment films. 
     A liquid crystal material is sealed in a sealed space formed by a seal material (not illustrated) adapted to connect the first substrate  11  and the second substrate  12  and by the both substrates, and thus the liquid crystal layer  13  is formed. The thickness (cell gap) of the liquid crystal layer  13  is defined by a spacer (not illustrated) provided between the first substrate  11  and the second substrate  12 . The long axis of the liquid crystal molecules  13   a  of the liquid crystal layer  13  is oriented twisted at 90 degrees (twist angle is 90°) between ends of the first substrate  11  and the second substrate  12  by alignment regulating force of the alignment films, and the long axis of the liquid crystal molecules  13   a  is oriented to gradually rotate (swivel) from one of the substrates toward the other of the substrates (chiral structure). Thus, the liquid crystal layer  13  has chirality when no voltage is applied. 
     The absorption type polarizing plate  21  includes a transmission axis (hereinafter, also referred to as a first transmission axis) and an absorption axis orthogonal to the first transmission axis. Of the incident light, light in a polarizing direction parallel to the first transmission axis is allowed by the absorption type polarizing plate  21  to pass therethrough. 
     The reflection type polarizing plate  22  includes a transmission axis (hereinafter, also referred to as a second transmission axis) and a reflection axis orthogonal to the second transmission axis. Of the incident light, light in a polarizing direction parallel to the second transmission axis is allowed by the reflection type polarizing plate  22  to pass therethrough and light in a polarizing direction parallel to the reflection axis is allowed by the reflection type polarizing plate  22  to reflect. 
     In the present embodiment, the absorption type polarizing plate  21  and the reflection type polarizing plate  22  are disposed (in a parallel Nicor arrangement) such that the first transmission axis of the absorption type polarizing plate  21  and the second transmission axis of the reflection type polarizing plate  22  are substantially parallel (or just parallel) to each other. In addition, the rubbing direction of the alignment film on the front side (i.e., the alignment film formed on the first substrate  11 ) is set parallel to the direction along the absorption axis of the absorption type polarizing plate  21 . 
     The absorption type polarizing plate  21  is attached via a first transparent adhesive film  31  to the front side surface of the first substrate  11 . The reflection type polarizing plate  22  is attached via a second transparent adhesive film  32  to the back side surface of the second substrate  12 . In addition, an optical element such as a retardation film may be provided between the liquid crystal element  10  and each of the polarizing plates. In such a case, the polarizing plate may be attached to the optical element located between the liquid crystal element  10  and the polarizing plate. 
     Each of the first transparent adhesive film  31  and the second transparent adhesive film  32  is made of, for example, an acrylic transparent adhesive (acrylic polymer) or the like. The first transparent adhesive film  31  is formed by applying a transparent adhesive to the surface of the absorption type polarizing plate  21  to be attached to the first substrate  11 . The second transparent adhesive film  32  is formed by applying a transparent adhesive to the surface of the reflection type polarizing plate  22  to be attached to the second substrate  12 . 
     When being in the transmission state, the liquid crystal panel  100  configured as described above allows transmission of a display light L (light representing a displayed image) of the display  200  as illustrated in  FIG. 2B . The display  200  located on the back side of the liquid crystal panel  100  includes, for example, a liquid crystal display having a backlight, or an organic electro luminescence (EL) display, and displays an image toward the liquid crystal panel  100 . An object to be transmitted visually recognizably by the liquid crystal panel  100  in the transmission state is not limited to the display  200 , and may be a character plate or a signboard, or a landscape. 
     Here, the liquid crystal panel  100  is switchable between the reflection state and the transmission state. 
     Reflection State 
     In a state where no drive voltage is applied, the liquid crystal molecules  13   a  are substantially parallel to the substrate surfaces in the liquid crystal panel  100  as illustrated in  FIG. 2A , and the liquid crystal layer  13  holds the chirality. In such a state, when the external light NL is incident on the front side of the liquid crystal panel  100 , the external light NL passes through the absorption type polarizing plate  21  and becomes linear polarized light parallel to the first transmission axis. Afterward, the external light NL passes through the liquid crystal layer  13  and then the polarizing direction is converted by 90° by the chirality of the liquid crystal layer  13 . Accordingly, the external light NL becomes linear polarized light along the reflection axis of the reflection type polarizing plate  22 , therefore being reflected on the reflection type polarizing plate  22 . The reflected light passes through the liquid crystal layer  13  and then the polarizing direction is again converted by 90° therefore, the light passes through the absorption type polarizing plate  21 . As just described, the liquid crystal panel  100  in the reflection state functions as a minor. Herein, a portion of the liquid crystal panel  100 , which functions as a mirror will be referred to as an active area. 
     On the other hand, when the display light L is incident on the back side of the liquid crystal panel  100 , thereafter the display light L passes through the reflection type polarizing plate  22  and becomes linear polarized light parallel to the second transmission axis. Afterward, the display light L passes through the liquid crystal layer  13  and then the polarizing direction is converted by 90°. Accordingly, the display light L becomes linear polarized light along the absorption axis of the absorption type polarizing plate  21 , therefore may be impossible to pass through the absorption type polarizing plate  21 . As just described, the display light L may be impossible to travel toward the front side of the liquid crystal panel  100 . Therefore, even when the display light L is incident on the liquid crystal panel  100 , a displayed image on the display  200  is not recognized by the observer  1 . In addition, when being output from the display  200 , the display light L may be linear polarized light parallel to the second transmission axis. 
     Transmission State 
     In a state where drive voltage is applied, the liquid crystal molecules  13   a  are oriented in a direction in which the voltage is applied (in the normal direction of the substrates) in the liquid crystal panel  100  as illustrated in  FIG. 2B , and the liquid crystal layer loses the chirality. In such a state, when the display light L is incident on the back side of the liquid crystal panel  100 , thereafter the display light L passes through the reflection type polarizing plate  22  and becomes linear polarized light parallel to the second transmission axis. However, even when the display light L passes through the liquid crystal layer  13 , the polarizing direction is not converted. Accordingly, the display light L passes through the absorption type polarizing plate  21  having the first transmission axis parallel to the second transmission axis. As just described, the liquid crystal panel  100  allows the display light L to pass, and thus a displayed image on the display  200  is transmitted visually recognizably. In addition, when the external light NL is incident on the front side of the liquid crystal panel  100 , thereafter the external light NL passes through the absorption type polarizing plate  21  and then passes through the liquid crystal layer  13  while remaining as linear polarized light parallel to the first transmission axis. Therefore, the external light NL passes through the reflection type polarizing plate  22  having the second transmission axis parallel to the first transmission axis and is not reflected on the reflection type polarizing plate  22  (excluding reflected light due to leak light). 
     Herein, how to set conditions that allow the liquid crystal panel  100  to compatibly have an appropriate total light reflectance in the reflection state and an appropriate total light reflectance in the transmission state will be described mainly with reference to  FIG. 3 . 
     The inventors of the present application paid attention to the fact that the reflectance of the liquid crystal panel  100  changes in accordance with the degree of polarization of the absorption type polarizing plate  21 , and produced five types of the liquid crystal panel (liquid crystal panels A to E indicated in  FIG. 3A ) in order to find suitable conditions for the degree of polarization. 
     The liquid crystal panels A to E have the same configuration as that of the liquid crystal panel  100 ; however, absorption type polarizing plates of the respective liquid crystal panels have different average degrees of polarization at a wavelength of 450 nm to 650 nm. “The degree of polarization” in  FIG. 3  indicates average degrees of polarization at a wavelength of 450 nm to 650 nm, and more specifically, average values of the degree of polarization for each 5 nm at respective wavelengths ( 450 ,  455 , . . .  645 ,  650 ) in the range of 450 nm to 650 nm. Herein, the average degree of polarization at the wavelength of 450 nm to 650 nm will be simply referred to as “the degree of polarization”. In addition, samples are made of the following materials. The first substrate  11  and the second substrate  12  are made of glass substrates having thickness of 1.1 mm, available from Nippon Sheet Glass Company, Ltd. A liquid crystal material configuring the liquid crystal layer  13  is manufactured by AGC Seimi Chemical Co., Ltd. The first transparent adhesive film  31  and the second transparent adhesive film  32  having film thickness of 25 μm are manufactured by Polatechno Co., Ltd. The absorption type polarizing plate  21  is manufactured by Polatechno Co., Ltd., and the reflection type polarizing plate  22  is made of Dual Brightness Enhancement Film (DBEF), available from 3M Company. 
     Focusing on the degree of polarization, firstly, as indicated in  FIG. 3A , the liquid crystal panel A has a degree of polarization of 57.7%, the liquid crystal panel B has a degree of polarization of 64.6%, and the liquid crystal panel C has a degree of polarization of 72.5%. The liquid crystal panel D has a polarization degree of 85.1%, and the liquid crystal panel E has a polarization degree of 99.9%. 
     The total light reflectance of five types of samples (the liquid crystal panels A to E) prepared as just described was measured. The total light reflectance (herein, simply also referred to as reflectance) is a ratio of the light output toward the front side to all of the light incident on the front side of the liquid crystal panel (from the absorption type polarizing plate  21 ). The reflectance was measured with an ultraviolet-visible-near-infrared spectrophotometer U-4100, available from Hitachi High-Tech Science Corporation. 
     Focusing on the reflectance measured as just described, as indicated in  FIG. 3A , the reflectance of the liquid crystal panel A in the reflection state is 45.4%, and the reflectance of the liquid crystal panel A in the transmission state is 12.5%. The reflectance of the liquid crystal panel B in the reflection state is 45.3%, and the reflectance of the liquid crystal panel B in the transmission state is 10.6%. The reflectance of the liquid crystal panel C in the reflection state is 42.5%, and the reflectance of the liquid crystal panel C in the transmission state is 8.6%. The reflectance of the liquid crystal panel D in the reflection state is 38.0%, and the reflectance of the liquid crystal panel D in the transmission state is 7.5%. The reflectance of the liquid crystal panel E in the reflection state is 34.7%, and the reflectance of the liquid crystal panel E in the transmission state is 6.9%. Here, the reflectance of the liquid crystal panel  100  in the reflection state is preferably 40% or greater in order that the liquid crystal panel as a mirror obtains a reflected image having a sufficient brightness. For example, an “automotive mirror” according to JIS D 5705 is defined to have a reflectance of 35% or greater. In addition, the reflectance of the liquid crystal panel  100  in the transmission state is preferably 12% or smaller and more preferably 10% or smaller. As a result of earnest examinations by the inventors, it was revealed that in a case where the back side (for example, a displayed image on the display  200 ) is visually recognized through the liquid crystal panel  100 , the visibility significantly decreases when the reflectance is greater than 12%, and that in a case where the back side (for example, a displayed image on the display  200 ) is transmitted visually recognizably, the visibility with high quality can be obtained when the reflectance is 10% or smaller. 
     Moreover, focusing on the relationship between the measured reflectance and the reflectance in the reflection state, as indicated in  FIG. 3B , when the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is 80% or smaller, the reflectance of the liquid crystal panel  100  in the reflection state is appropriately 40% or greater. Meanwhile, when the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is 60% or greater, the reflectance of the liquid crystal panel  100  in the transmission state is appropriately 12% or smaller. When the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is 67% or greater, the reflectance of the liquid crystal panel  100  in the transmission state is more appropriately 10% or smaller. In other words, in order for the liquid crystal panel  100  to compatibly have an appropriate reflectance in the reflection state and an appropriate reflectance in the transmission state, the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is desirably 60% or greater and 80% or smaller, and more desirably 67% or greater and 80% or smaller. 
     (1) The liquid crystal panel  100  described above is designed such that the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is 60% or greater and 80% or smaller. Therefore, the liquid crystal panel  100  can compatibly have an appropriate total light reflectance in the reflection state and an appropriate total light reflectance in the transmission state. 
     (2) Moreover, the liquid crystal panel  100  is designed such that the average degree of polarization of the absorption type polarizing plate  21  at the wavelength of 450 nm to 650 nm is 67% or greater. Therefore, the liquid crystal panel  100  in the transmission state can be a more appropriate total light reflectance. 
     Note that the present invention is not limited by the foregoing embodiments and the drawings. It will be understood that the embodiments and the drawings may be changed (some of the components may also be omitted). 
     In the description above, an example is illustrated that the liquid crystal panel  100  is structured such that the first transmission axis of the absorption type polarizing plate  21  is set parallel to the second transmission axis of the reflection type polarizing plate  22 , and is designed to be brought into the reflection state when the drive voltage is not applied and to be brought into the transmission state when the drive voltage is applied (normally reflection). However, the liquid crystal panel  100  is not limited to the example. Alternatively, the liquid crystal panel  100  may be structured such that the first transmission axis of the absorption type polarizing plate  21  is set substantially orthogonal to the second transmission axis of the reflection type polarizing plate  22 , and may be designed to be brought into the reflection state when the drive voltage is applied and to be brought into the transmission state when the drive voltage is not applied (normally transmission). In the example of normally transmission, the liquid crystal panel  100  is switchable between the reflection state and the transmission state as follows. 
     Reflection State 
     In a state where the drive voltage is applied, the liquid crystal molecules  13   a  are oriented, as described above, in the direction in which the voltage is applied (in the normal direction of the substrates) in the liquid crystal panel  100 , and the liquid crystal layer  13  loses the chirality. In such a state, when the external light NL is incident on the front side of the liquid crystal panel  100 , thereafter the external light NL passes through the absorption type polarizing plate  21  while remaining as linear polarized light parallel to the first transmission axis. Accordingly, the external light NL becomes the linear polarized light along the reflection axis of the reflection type polarizing plate  22 , which is parallel to the first transmission axis, and then is reflected on the reflection type polarizing plate  22 . Afterward, the reflected light again passes through liquid crystal layer  13  and passes through the absorption type polarizing plate  21  having the first transmission axis substantially orthogonal to the reflection axis. Thus, the liquid crystal panel  100  in the reflection state functions as a mirror. Meanwhile, when the display light L is incident on the back side of the liquid crystal panel  100 , the display light L passes through the reflection type polarizing plate  22  and becomes linear polarized light parallel to the second transmission axis, and then passes through the liquid crystal layer  13 . Accordingly, the display light L may be impossible to pass through the absorption type polarizing plate  21  having the absorption axis parallel to the second transmission axis. Thus, the display light L may be impossible to travel toward the front side of the liquid crystal panel  100 . Therefore, even when the display light L enters the liquid crystal panel  100 , a displayed image on the display  200  is not visually recognized by the observer  1 . 
     Transmission State 
     In a state where no drive voltage is applied, the liquid crystal molecules  13   a  are substantially parallel, as described above, to the substrate surfaces in the liquid crystal panel  100 , and the liquid crystal layer  13  holds the chirality. In such a state, when the display light L is incident on the back side of the liquid crystal panel  100 , the display light L passes through the reflection type polarizing plate  22  and becomes linear polarized light parallel to the second transmission axis. Afterward, the display light Lpasses through the liquid crystal layer  13  and then the polarizing direction is converted by 90° by the chirality of the liquid crystal layer  13 . Accordingly, the display light Lpasses through the absorption type polarizing plate  21  having the first transmission axis orthogonal to the second transmission axis. As just described, the liquid crystal panel  100  allows the display light L to be transmitted, and thus a displayed image on the display  200  is transmitted visually recognizably. In addition, when the external light NL is incident on the front side of the liquid crystal panel  100 , the external light NL passes through the absorption type polarizing plate  21  and becomes linear polarized light parallel to the first transmission axis. Therefore, the external light NL passes through the liquid crystal layer  13  and then converted by 90° by the chirality of the liquid crystal layer  13 . Accordingly, the external light NL becomes linear polarized light along the second transmission axis substantially orthogonal to the reflection axis of the reflection type polarizing plate  22 , which is parallel to the first transmission axis, and passes through the reflection type polarizing plate  22  having the second transmission axis. Therefore, the external light NL is not reflected on the reflection type polarizing plate  22  (excluding reflected light due to leak light). 
     Further, the liquid crystal panel  100  may be used for any purpose. For example, the liquid crystal panel  100  is applicable in various usages such as a watch or a portable device (for example, the liquid crystal panel  100  in the transmission state allows information to be displayed on the display  200  located on the back side of the liquid crystal panel  100 , and the liquid crystal panel  100  in the reflection state functions as a mirror), transmission/reflection control of a certain window (for example, the liquid crystal panel  100  in the transmission state functions as a window that transmits a scenery, and the liquid crystal panel  100  in the reflection state functions as a mirror), or a side mirror or a room mirror of an automobile (for example, the liquid crystal panel  100  in the transmission state allows vehicle information or a camera image to be displayed on the display  200  located on the back side of the liquid crystal panel  100 ). 
     Furthermore, as described above, the liquid crystal panel  100  is formed in a substantially rectangular shape when viewed in the normal direction of the substrates. Alternatively, the liquid crystal panel  100  may be formed in a circular shape, a polygonal shape, or another shape and may be formed in any shape depending on the application. Likewise, each of the transparent electrodes  11   a ,  12   a  may be formed in any shape when viewed in the normal direction of the substrates. 
     Moreover, the twisted nematic (TN) type liquid crystal element  10  having a twist angle of 90° is described above as an example, but not limited thereto. Alternatively, as long as the aforementioned reflection and transmission states can be realized by applying voltage to the liquid crystal layer  13 , the twist angle may be below 90° or greater than 90°. For example, the liquid crystal element  10  may be a super twisted nematic (STN) type crystal element. In addition, as long as the reflection and transmission states can be realized by applying voltage to the liquid crystal layer  13 , the first transmission axis of the absorption type polarizing plate  21  and the second transmission axis of the reflection type polarizing plate  22  may not be parallel or orthogonal to each other. Each of the optical axes and the rubbing direction of the corresponding alignment film may not be parallel or orthogonal to each other. Each optical axis can be shifted as appropriate in consideration of visual characteristics when the liquid crystal element is in the transmission state or in consideration of reflection characteristics when the liquid crystal element is in the reflection state. 
     In the above description, in order to facilitate understanding of the present invention, the description of known technical matters has been omitted as appropriate. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           100  Liquid crystal panel 
           10  Liquid crystal element 
           11  First substrate,  11   a  Transparent electrode,  12  Second substrate,  12   a  Transparent electrode 
           13  Liquid crystal layer,  13   a  Liquid crystal molecules 
           21  Absorption type polarizing plate 
           22  Reflection type polarizing plate 
           31  First transparent adhesive film 
           32  Second transparent adhesive film