JP2009175756A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-face display type liquid crystal display in which bright and favorable reflection display with no coloring can be performed whenever either one or another face is used as a display screen. <P>SOLUTION: First and second liquid crystal elements 10A, 10B each having a liquid crystal layer held between a front substrate 11 as the observation side display and a back side substrate 12 are disposed in the opposite directions with the back faces opposing to each other. Absorptive polarizing plates 16 and 17 are disposed in the front side of the first liquid crystal element 10A and in the front side of the second liquid crystal element 10B, respectively, and a reflective polarizing element 18 which reflects one polarization component out of two different polarization components of the incident light and transmits the other polarization component is disposed between the first and second liquid crystal elements 10A and 10B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device that performs reflective display on both sides.

  A liquid crystal display device is basically a liquid crystal that controls the polarization state of transmitted light in accordance with an electric field applied between a front substrate that is an observation side of a display and a rear substrate that faces the front substrate. It consists of a liquid crystal element provided with a layer and a pair of polarizing plates arranged on the front side and the rear side across the liquid crystal element.

  This liquid crystal display device includes a reflective type that performs reflective display using external light that is light from the external environment, and a surface light source called a backlight on the rear side, and uses the light from the surface light source. As a liquid crystal display device that performs transmissive display, one of the two linearly polarized components of incident light that are orthogonal to each other on the front side and the rear side of the liquid crystal element is used. An absorption polarizing plate that absorbs light and transmits the other polarization component is disposed, and a reflective film is disposed behind the absorption polarizing plate on the rear side opposite to the display viewing side. Yes.

  Note that in the liquid crystal display device, the polarizing plate on the rear side of the liquid crystal element transmits one of the two polarization components orthogonal to each other and scatters the other polarization component to reflect or transmit. Either a polarizing plate and a light absorbing layer or a reflector on the rear side for reflection display, or a surface light source on the rear side of the scattering polarizing plate for both reflection display and transmission display In some cases, the display is performed (see Patent Document 1).

  By the way, recently, as an electronic device such as a mobile phone or a mobile terminal having a lid that can be opened and closed with respect to the device main body, the lid can be displayed so that information can be displayed in both the opened state and the closed state. It has become possible to see a display provided on the inner surface (the surface facing the device body when the lid is closed) and the outer surface.

  In this type of electronic device, two liquid crystal elements are arranged in opposite directions with their rear surfaces facing each other, and absorption polarizers are arranged on the front and rear sides of these liquid crystal elements, respectively, A double-sided display type liquid crystal display device in which a surface light source is disposed between a side polarizing plate and the other rear polarizing plate is used. (See Patent Documents 2 and 3).

  In this double-sided display type liquid crystal display device, the display on both sides is a transmissive display using light from a surface light source, but it is reflected between the one rear polarizing plate and the other rear polarizing plate. By disposing a plate, it is also possible to make both sides of the display a reflective display using external light.

JP 2000-75284 A JP-A-10-90678 Japanese Patent Laid-Open No. 2001-290445

  However, an absorption polarizing plate is disposed on each of the front side and the rear side of the two liquid crystal elements arranged in the opposite directions as described above, and the reflection plate is disposed between one rear polarizing plate and the other rear polarizing plate. In the double-sided display type liquid crystal display device that performs reflection display by arranging the first and second surfaces, the light is incident from the front side of the display surface and reflected by the reflecting plate even when the other surface is used as the display surface. Since the light emitted from the display surface is absorbed four times in total by the front and rear absorption polarizing plates in the process, the intensity of the emitted light from the display surface is reduced with respect to the intensity of the light incident from the front side of the display surface. Is large and the display is dark.

  In addition, the double-sided display type liquid crystal display device that performs the reflective display has wavelength dependency in the light absorption characteristics of the absorbing polarizing plate. In the process of passing, a band color is generated in the transmitted light, and the display is banded.

  An object of the present invention is to provide a liquid crystal display device of a double-sided display type that can perform a good reflective display that is bright and has no color even when either one surface or the other surface is used as a display surface. It is a thing.

  In the liquid crystal display device of the present invention, a liquid crystal layer that controls the polarization state of transmitted light according to an applied electric field is provided between a front substrate that is a display viewing side and a rear substrate that faces the front substrate. And first and second liquid crystal elements arranged in opposite directions with their rear surfaces facing each other, and two straight lines arranged on the front side of the first liquid crystal element and orthogonal to each other of incident light Among the polarized components, a first absorbing polarizing plate that absorbs one polarized component and transmits the other polarized component, and two linearly polarized lights arranged on the front side of the second liquid crystal element and orthogonal to each other of incident light Among the components, a second absorbing polarizing plate that absorbs one polarization component and transmits the other polarization component, and two polarizations of incident light that are different from each other and disposed between the first and second liquid crystal elements. One of the components reflects one polarization component, and the other polarization Characterized by comprising a polarization separating element which transmits minute.

  In the liquid crystal display device, the reflective display in which the front surface of the first absorbing polarizing plate on the front side of the first liquid crystal element is one display surface, and the first liquid crystal element are disposed in the opposite direction. When the front surface of the second absorption polarizing plate on the front side of the second liquid crystal element is used as the other display surface, the first liquid crystal element has the one surface as a display surface. The liquid crystal layer is driven by applying an electric field, and the second liquid crystal element is driven by applying an electric field to the liquid crystal layer when the other surface is the display surface.

  When the one surface is used as a display surface, light incident from the front side of the one surface is converted into linearly polarized light by the first absorption polarizing plate, and further, by the liquid crystal layer of the first liquid crystal element. The polarization state is controlled to enter the polarization separation element, and among the light, the light controlled to the polarization reflected by the polarization separation element is reflected by the polarization separation element, and the reflected light is reflected on the one surface. The display that is emitted from the one surface and observed from the one surface becomes a bright display, and the light controlled to the polarized light that is transmitted through the polarization separation element is transmitted through the polarization separation element and is observed from the one surface. The display becomes dark.

  Further, when the other surface is used as a display surface, light incident from the front side of the other surface is converted into linearly polarized light by the second absorbing polarizing plate, and further, by the liquid crystal layer of the second liquid crystal element. The polarization state is controlled to enter the polarization separation element, and among the light, one polarization component light is reflected by the polarization separation element, the reflected light is emitted from the other surface, and the other The display observed from the surface is a bright display, the light controlled to the polarized light transmitting the polarization separation element is transmitted through the polarization separation element, and the display observed from the one surface is a dark display.

  This liquid crystal display device absorbs light by the polarizing plate in both the reflective display using the one surface as a display surface and the reflective display using the other surface as a display surface. Therefore, the decrease in the intensity of the emitted light with respect to the intensity of the light incident from the front side of the display surface is small, and the color of the transmitted light due to the wavelength dependence of the light absorption characteristics of the absorption polarizer is almost all Therefore, even when any one of the one and the other surface is used as a display surface, it is possible to perform bright and good reflective display without any color.

  As described above, the liquid crystal display device according to the present invention includes the first and second liquid crystal elements in which the liquid crystal layer is provided between the front substrate and the rear substrate on the display observation side, and the rear surfaces of the first and second liquid crystal elements are mutually connected. Oppositely arranged in opposite directions, an absorption polarizing plate is disposed on the front side of the first liquid crystal element and on the front side of the second liquid crystal element, respectively, and between the first and second liquid crystal elements. When a polarization separation element that reflects one of the two different polarized light components of incident light and transmits the other polarized light component is disposed, either one or the other surface is used as the display surface. Also, it is possible to perform a good reflective display that is bright and free of band color.

  In the liquid crystal display device according to the present invention, the one of the first and second liquid crystal elements and the one of the polarization separation elements disposed between the first and second liquid crystal elements It is desirable to further include a surface light source that transmits light incident from the liquid crystal element side and the polarization separation element side and emits illumination light toward the polarization separation element.

  Further, in this liquid crystal display device, the polarization separation element disposed between the first and second liquid crystal elements has a transmission axis and a reflection axis in directions orthogonal to each other, and two straight lines of incident light orthogonal to each other. Of the polarized light components, a reflective polarizing element that reflects one linearly polarized light component having a vibration surface parallel to the reflection axis and transmits the other linearly polarized light component having a vibration surface parallel to the transmission axis is desirable.

  Further, in this liquid crystal display device, the first and second liquid crystal elements are preferably TN liquid crystal elements in which liquid crystal molecules are twist-aligned between the front and back substrates at a twist angle of substantially 90 °, and the polarization separation element Is the reflective polarizing element, and the first and second liquid crystal elements are the TN liquid crystal elements, respectively, the first and second absorption polarizations on the front side of the first and second TN liquid crystal elements. The plates are arranged with their respective transmission axes substantially orthogonal to each other, and the reflective polarizing element has its transmission axis substantially orthogonal to the transmission axes of the first and second absorption polarizers, It is preferable to arrange it substantially parallel to the transmission axis of the other absorption polarizing plate.

  The first and second liquid crystal elements may be liquid crystal elements other than the TN liquid crystal element. For example, at least one of the first and second liquid crystal elements may be disposed between the front and back substrates of liquid crystal molecules. When the STN type liquid crystal element is twisted with a twist angle of 180 ° to 270 °, the liquid crystal molecules are arranged in the vicinity of the substrate before and after the STN type liquid crystal element and on the front side of the STN type liquid crystal element. The direction of the transmission axis of the absorbing polarizing plate and the direction of the transmission axis of the reflective polarizing element are preferably set so as to form a normally black or normally white display system.

  In the liquid crystal display device of the present invention, the first and second liquid crystal elements in which a liquid crystal layer is provided between the front substrate and the rear substrate on the display viewing side are reversed with their rear surfaces facing each other. An absorbing polarizing plate is disposed on each of the front side of the first liquid crystal element and the front side of the second liquid crystal element, and incident light is transmitted between the first and second liquid crystal elements. Of two different polarization components, a polarization separation element that reflects one polarization component and transmits the other polarization component is arranged, so when either one of the other surfaces is used as a display surface, Bright and good reflective display without band color can be performed.

  In the liquid crystal display device according to the present invention, the one liquid crystal is disposed between one of the first and second liquid crystal elements and the polarization separation element disposed between the first and second liquid crystal elements. It is desirable to further include a surface light source that transmits light incident from the element side and the polarization separation element side and emits illumination light toward the polarization separation element. When the other surface is used as a display surface, both a reflective display using external light and a transmissive display using illumination light from the surface light source can be displayed.

  In the liquid crystal display device of the present invention, the polarization separating element disposed between the first and second liquid crystal elements has a transmission axis and a reflection axis in directions orthogonal to each other, and is orthogonal to incident light. A reflective polarizing element that reflects one linearly polarized light component having a vibration surface parallel to the reflection axis and transmits the other linearly polarized light component having a vibration surface parallel to the transmission axis, out of two linearly polarized light components And the first and second liquid crystal elements are TN liquid crystal elements in which liquid crystal molecules are twist-aligned with a twist angle of substantially 90 ° between the front and rear substrates, and the first and second TN type liquid crystal elements. The first and second absorption polarizers on the front side of the liquid crystal element are arranged so that their transmission axes are substantially perpendicular to each other, and the reflective polarizing element has one of the first and second transmission axes. Substantially perpendicular to the transmission axis of the absorbing polarizer, etc. It is preferable to arrange it substantially in parallel with the transmission axis of the absorbing polarizing plate, and this makes it brighter when one surface is used as a display surface and when the other surface is used as a display surface. In addition, a high contrast display can be obtained without any band color.

  In the liquid crystal display device of the present invention, the first and second liquid crystal elements are at least one of STN type liquid crystal elements in which liquid crystal molecules are twist-aligned at a twist angle of 180 ° to 270 ° between the front and rear substrates. In that case, the polarization separating element is the reflective polarizing element, and the alignment direction of the liquid crystal molecules in the vicinity of the substrate before and after the STN type liquid crystal element and the absorption arranged on the front side of the STN type liquid crystal element When the direction of the transmission axis of the polarizing plate and the direction of the transmission axis of the reflective polarizing element are set so as to form a normally black or normally white display system, and one surface is used as the display surface However, even when the other surface is used as a display surface, a bright display with no band color and high contrast can be obtained.

1 is an exploded perspective view of a liquid crystal display device showing a first embodiment of the present invention. Sectional drawing which abbreviate | omitted hatching of the liquid crystal display device of a 1st Example. The schematic diagram which shows the transmission path | route of incident light when performing the 1st display which uses one surface of the liquid crystal display device of a 1st Example as a display surface. The schematic diagram which shows the permeation | transmission path | route of incident light when performing the 2nd display which uses the other surface of the liquid crystal display device of a 1st Example as a display surface. The perspective view which shows an example of the electronic device which has a display part on both surfaces. Sectional drawing which abbreviate | omitted hatching of the liquid crystal display device which shows 2nd Example of this invention. Sectional drawing which abbreviate | omitted hatching of the liquid crystal display device which shows 3rd Example of this invention. The exploded side view of other polarization separation elements.

  1 to 5 show a first embodiment of the present invention, FIG. 1 is an exploded perspective view of a liquid crystal display device, FIG. 2 is a sectional view in which the hatching of the liquid crystal display device is omitted, and FIGS. FIG. 5 is a schematic diagram showing a transmission path of incident light when one surface of the liquid crystal display device is used as a display surface and when the other surface is used as a display surface, and FIG. 5 shows an electronic device having display portions on both surfaces. It is a perspective view which shows an example.

  First, the electronic device shown in FIG. 5 will be described. This electronic device is a mobile phone, and has a device main body 1 having a plurality of keys 2 on the front surface and one end pivotally supported by the upper edge of the device main body 1. The lid 3 is provided so as to be openable and closable with respect to the device main body 1. When the lid 3 is closed as shown in FIG. 5A, the device main body 1 is closed. Display portions A and B are provided on the surface facing forward when the lid 3 is opened as shown in FIG. 5B and the outer surface of the lid 3, respectively.

  Next, the liquid crystal display device of the first embodiment will be described. As shown in FIG. 1 and FIG. 2, the liquid crystal display device has rear surfaces opposite to the display viewing side facing each other. The first and second liquid crystal elements 10A and 10B disposed in opposite directions, the polarizing plates 16 and 17 disposed on the front side of the first and second liquid crystal elements 10A and 10B, respectively, A polarization separation element 18 disposed between the second liquid crystal elements 10A and 10B, and a surface disposed between one of the first and second liquid crystal elements 10A and 10B and the polarization separation element 18 And a light source 19.

  Each of the first and second liquid crystal elements 10A and 10B is applied between a front transparent substrate 11 that is a display observation side and a rear transparent substrate 12 that faces the front substrate 11. A liquid crystal layer 15 (see FIG. 2) for controlling the polarization state of transmitted light according to the electric field is provided, and the front substrate 11 and the rear substrate 12 are bonded via a frame-shaped sealing material 13. The liquid crystal layer 15 is provided in a region surrounded by the sealing material 13 between the substrates 11 and 12.

  Although not shown in the drawing, a plurality of pixels arranged in a matrix with regions facing each other are provided on the inner surfaces of the substrates 11 and 12 before and after the first and second liquid crystal elements 10A and 10B. A transparent electrode to be formed is provided, and an alignment film is provided thereon.

  The first and second liquid crystal elements 10A and 10B are active matrix liquid crystal elements having TFTs (thin film transistors) as active elements, for example, on the inner surface of one substrate, for example, the rear substrate 12, in the row direction and the column direction. A plurality of pixel electrodes arranged in a matrix, a plurality of TFTs respectively connected to these pixel electrodes, a plurality of gate wirings for supplying gate signals to the TFTs in each row, and a data signal to each TFT in each column A plurality of data wirings (none of which are shown) are provided, and a plurality of colors are formed on the inner surface of the front substrate 11 which is the other substrate so as to alternately face each of the plurality of pixel electrodes, For example, three color filters 14R, 14G, and 14B (see FIG. 2) of red, green, and blue, and the color filters 14R, 14G, and 14B It made a single film-like counter electrode (not shown) is provided.

  In FIG. 2, the pixel pitch of the first and second liquid crystal elements 10A and 10B (the pitch of the color filters 14R, 14G, and 14B) is greatly exaggerated, but the first and second liquid crystal elements are shown. The pixel pitches of 10A and 10B are both extremely small pitches of 100 μm to 200 μm.

  Each of the first and second liquid crystal elements 10A and 10B is of a TN (twisted nematic) type, and the liquid crystal layer 15 is substantially 90 between the front and rear substrates 11 and 12. It consists of nematic liquid crystal with positive dielectric anisotropy twisted at a twist angle of °.

  In FIG. 1, an arrow 11a indicates a liquid crystal molecule alignment direction in the vicinity of the front substrate 11 of the first and second liquid crystal elements 10A, and an arrow 12a indicates a liquid crystal molecule alignment direction in the vicinity of the rear substrate 12. The liquid crystal molecule alignment direction 11a in the vicinity of the front substrate (upper substrate in the figure) 11 of the upper first liquid crystal element 10A is the horizontal axis of the first and second liquid crystal elements 10A and 10B set in parallel to each other ( The direction of the rear substrate (lower substrate in the figure) 12 in one direction with respect to the horizontal axis (x) along the surfaces of the substrates 11 and 12, for example, substantially 45 ° clockwise as viewed from the front side. The liquid crystal molecule alignment direction 12a in the vicinity is substantially 45 ° in the other direction with respect to the horizontal axis x, that is, counterclockwise when viewed from the front side, and the liquid crystal layer 15 of the first liquid crystal element 10A Liquid crystal molecules As indicated by broken line arrows in FIG. 1, the twist direction is from the rear substrate 12 toward the front substrate 11 and is twist-oriented substantially at a twist angle of 90 ° clockwise from the front side.

  On the other hand, the liquid crystal molecule alignment direction 11a in the vicinity of the front substrate (lower substrate in the figure) 11 of the lower second liquid crystal element 10B in FIG. 1 is in the vicinity of the front substrate 11 of the first liquid crystal element 10A. The liquid crystal molecule alignment direction 12a in the vicinity of the rear substrate (upper substrate in the figure) 12 in a direction substantially parallel to the liquid crystal molecule alignment direction 11a is the liquid crystal in the vicinity of the rear substrate 12 of the first liquid crystal element 10A. The liquid crystal molecules in the liquid crystal layer 15 of the second liquid crystal element 10B are in a direction substantially parallel to the molecular orientation direction 12a, and the twist direction of the liquid crystal molecules from the rear substrate 12 is indicated by a broken line arrow in FIG. It faces the front substrate 11 and is twist-oriented substantially at a twist angle of 90 ° clockwise (when viewed from the rear side in FIG. 1) when viewed from the front.

  The liquid crystal molecule alignment direction 11a in the vicinity of the front substrate 11 of each of the first and second liquid crystal elements 10A and 10B and the liquid crystal molecule alignment direction 12a in the vicinity of each rear substrate 12 are opposite to the above. , They may be substantially orthogonal.

  Further, the first polarizing plate 16 disposed on the front side of the first liquid crystal element 10A and the second polarizing plate 17 disposed on the front side of the second liquid crystal element 10B are respectively orthogonal to each other. Of the two linearly polarized light components of the incident light that are orthogonal to each other and having transmission axes 16a, 17a and an absorption axis (not shown), the light of one polarization component having a vibration plane parallel to the absorption axis is absorbed. The absorbing polarizing plate transmits the other polarization component having a vibration plane parallel to the transmission axes 16a and 17a.

  The first absorption polarizing plate 16 has its transmission axis 16a substantially parallel or perpendicular (orthogonal in the drawing) to the liquid crystal molecule alignment direction 11a in the vicinity of the front substrate 11 of the first liquid crystal element 10A. The second absorption polarizing plate 17 is attached to the outer surface of the front substrate 11 of the first liquid crystal element 10A, and the liquid crystal molecule alignment direction of the second absorption polarizing plate 17 has its transmission axis 17a in the vicinity of the front substrate 11 of the second liquid crystal element 10B. 11a is substantially parallel or orthogonal (orthogonal in the figure), and substantially orthogonal to the transmission axis 16a of the first absorption polarizing plate 16, so that the front substrate 11 of the second liquid crystal element 10B is Affixed to the outside.

  That is, the first liquid crystal element 10A and the second liquid crystal element 10B are arranged with the liquid crystal molecule alignment directions 12a in the vicinity of the rear substrate 12 substantially parallel or orthogonal (parallel in FIG. 1). In addition, the first absorption polarizing plate 16 on the first liquid crystal element 10A side and the second absorption polarizing plate 17 on the second liquid crystal element 10B side have the transmission axes 16a and 17a on the first absorption polarizing plate 16a. The liquid crystal element alignment direction 12a in the vicinity of the rear substrate 12 of the liquid crystal element 10A and the second liquid crystal element 10B is substantially parallel or orthogonal, and the transmission axes 16a and 17a are substantially orthogonal to each other. Has been.

  The polarization separating element 18 is a reflective polarizing element that reflects one linearly polarized light component and transmits the other linearly polarized light component, for example, of two linearly polarized light components perpendicular to each other of incident light. In the example, a linearly polarized light component having a transmission axis 18a and a reflection axis 18b in directions orthogonal to each other and having a vibration plane parallel to the reflection axis 18b is reflected, and a vibration plane parallel to the transmission axis 18a is reflected. A reflective polarizing plate that transmits light having a linearly polarized light component is used. Hereinafter, the polarization separating element 18 is referred to as a reflective polarizing element.

  The reflective polarizing element 18 has its transmission axis 18 a substantially the same as the transmission axis 16 a of one of the first and second absorption polarizing plates 16, 17, for example, the first absorption polarizing plate 16. Is disposed between the first and second liquid crystal elements 10A and 10B so as to be substantially parallel to the transmission axis 17a of the second absorption polarizing plate 17, which is the other absorption polarizing plate.

  The surface light source 19 transmits light incident from one surface and the other surface, and makes the incident light from the end surface emit light from the one surface opposite to the end surface of the light guide plate 20. The light emitting element 22 is provided.

  In addition, the surface light source 19 used in this embodiment is one in which a plurality of the light emitting elements 22 made of LEDs (light emitting diodes) are arranged to face the end surface of the light guide plate 20. The light emitting element disposed to face the tube may be a straight tubular cold cathode tube or the like.

  The surface light source 19 transmits light incident from one surface of the light guide plate 20 and emits light from the other surface of the light guide plate 20, and transmits light incident from the other surface of the light guide plate 20. The illumination light emitted from one surface of the light guide plate 20 and emitted from the light emitting element 22 is incident on the light guide plate 20 from its end surface, and the illumination light is incident on one and the other surfaces of the light guide plate 20. The light guide plate 20 is guided in the light guide plate 20 while being totally reflected at the interface between the outside air (air) and emitted from one surface (hereinafter referred to as illumination light exit surface) 20a of the light guide plate 20; The light that has traveled toward the other surface in the light guide plate 20 is reflected on the other surface of the light guide plate 20 in a direction in which the angle with respect to the normal to the light guide plate surface becomes smaller. A plurality of groove-shaped recesses 21 for emitting light The end face of the light guide plate 20 and are formed in parallel.

  In the figure, the pitch of the plurality of groove-like recesses 21 is greatly exaggerated, but the groove-like recesses 21 are formed with a pixel pitch (100 μm to 200 μm) of the first and second liquid crystal elements 10A, 10B. Is formed at a pitch smaller than (about).

  The surface light source 19 is configured to illuminate light from the light guide plate 20 between one of the first and second liquid crystal elements 10A and 10B, for example, between the first liquid crystal element 10A and the reflective polarizing element 18. The exit surface 20a is arranged facing the reflective polarizing element 18. That is, the surface light source 19 transmits light incident from the first liquid crystal element 10 </ b> A side and the reflective polarizing element 18 side, and emits illumination light toward the reflective polarizing element 18. In the liquid crystal display device, for example, in the lid 3 of the electronic apparatus (mobile phone) shown in FIG. 5, the transmission axis 16a of the both surfaces of the liquid crystal display device is substantially the same as the transmission axis 18a of the reflective polarizing element 18. The arrangement side of the first liquid crystal element 10A provided with the orthogonal first absorption polarizing plate 16 is the display portion A on the inner surface side of the lid 3, and the transmission axis 17a is the transmission axis 18a of the reflective polarizing element 18. The second liquid crystal element 10 </ b> A provided with the second absorption polarizing plate 17 that is substantially parallel to the mounting surface is mounted as the display portion B on the outer surface side of the lid 3.

  In this liquid crystal display device, a first display on which one surface on which the first liquid crystal element 10A is disposed is used as a display surface, and the first liquid crystal element 10A is observed from the front side of the first absorbing polarizing plate 16. And the second display in which the other surface on which the second liquid crystal element 10B is disposed is used as a display surface, and the second liquid crystal element 10B is observed from the front side of the second absorption polarizing plate 17. The first liquid crystal element 10A is driven by applying an electric field to the liquid crystal layer 15 during the first display, and the second liquid crystal element 10B is driven by the second liquid crystal element 10B. The display is driven by applying an electric field to the liquid crystal layer 15.

  In addition, the liquid crystal display device is incident from the front side, which is the viewing side of the display, in an environment where sufficient brightness of external light is obtained in both the first display and the second display. Reflective display using external light is performed, and when sufficient external light is not obtained, illumination light is emitted from the surface light source 19 and transmissive display using the illumination light is performed. The display is also observed from the front direction (direction near the normal of the display surface).

  FIG. 3 is a schematic diagram showing a transmission path of incident light when performing a first display with one surface of the liquid crystal display device as a display surface, and FIG. 4 shows a second display with the other surface as a display surface. It is a schematic diagram which shows the transmission path | route of incident light when performing.

  First, a transmission path of incident light in the first display shown in FIG. 3 will be described. In FIG. 3, a transmission path indicated by a solid line is a path for reflective display using outside light, and a transmission path indicated by a broken line is a path for transmission display using illumination light from the surface light source 19. .

  When the first display for observing the first liquid crystal element 10A from the front side of the first absorbing polarizing plate 16 is performed by reflective display, as shown by the solid line in FIG. Of the two linearly polarized light components perpendicular to each other of the external light (non-polarized light) incident from the front side, the light of the polarized light component parallel to the absorption axis of the first absorbing polarizing plate 16 is absorbed by the absorbing polarizing plate 16, Light having a polarization component parallel to the transmission axis 16 a of the absorption polarizing plate 16 is transmitted through the absorption polarizing plate 16 and becomes linearly polarized light S parallel to the transmission axis 16 a of the absorption polarizing plate 16. Incident on 10A.

  The linearly polarized light S incident on the first liquid crystal element 10A is subjected to the birefringence action of the liquid crystal layer 15 according to the alignment state of the liquid crystal molecules changed by the electric field applied between the electrodes of the liquid crystal element 10A. The light is emitted to the rear side of one liquid crystal element 10A.

  That is, the alignment state of the liquid crystal molecules when no electric field is applied between the electrodes of the first liquid crystal element 10A (V = 0) is substantially a twist alignment with a twist angle of 90 °. The linearly polarized light S transmitted through the first absorbing polarizer 16 and incident on the first liquid crystal element 10A is vibrated by the birefringence of the liquid crystal layer 15 as shown by the solid line on the right side of FIG. Becomes linearly polarized light P substantially rotated by 90 ° and is emitted to the rear side of the first liquid crystal element 10A.

  The linearly polarized light P emitted to the rear side of the first liquid crystal element 10A is transmitted through the light guide plate 20 of the surface light source 19, and the transmission axis 18a is substantially the same as the transmission axis 16a of the first absorption polarizing plate 16. Is transmitted through the reflective polarizing element 18 orthogonal to the second liquid crystal element 10B on the other surface side, and enters from the rear side. The second liquid crystal element 10B on the other surface side is in a non-driven state (a state in which the liquid crystal molecules of the liquid crystal layer 15 are twist-aligned) with no electric field (V = 0) during the first display. Therefore, the linearly polarized light P transmitted through the reflective polarizing element 18 and incident on the second liquid crystal element 10B from the rear side thereof is converted into the linearly polarized light S by the birefringence action of the liquid crystal layer 15 of the second liquid crystal element 10B. Then, the light is emitted to the front side of the second liquid crystal element 10B, and the transmission axis 17a is absorbed by the second absorption polarizing plate 17 substantially parallel to the transmission axis 18a of the reflective polarizing element 18.

  Therefore, the display in the absence of an electric field (V = 0) during the reflective display in the first display is a black dark display.

  On the other hand, when an electric field is applied between the electrodes of the first liquid crystal element 10A so that liquid crystal molecules rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 (V> Vth), The linearly polarized light S transmitted through the absorption polarizing plate 16 and incident on the first liquid crystal element 10A passes through the liquid crystal layer 15 as the linearly polarized light S as shown by the solid line on the left side of FIG. Is emitted to the rear side of the liquid crystal element 10A.

  The linearly polarized light S emitted to the rear side of the first liquid crystal element 10 </ b> A passes through the light guide plate 20 and enters the reflective polarizing element 18, and is reflected by the reflective polarizing element 18.

  The linearly polarized light S reflected by the reflective polarizing element 18 is transmitted again through the light guide plate 20 and re-enters the first liquid crystal element 10A from the rear side. Then, the light enters the first absorption polarizing plate 16, passes through the first absorption polarizing plate 16, and exits from the one surface.

  Therefore, the display when the electric field is applied (V> Vth) during the reflective display in the first display is a bright display colored in the colors of the color filters 14R, 14G, and 14B of the first liquid crystal element 10A.

  Further, when the first display is performed by transmissive display, the light emitting element 22 of the surface light source 19 is turned on, and the illumination light (non-polarized light) from the light emitting element 22 is shown by a broken line in FIG. The light enters the light guide plate 20 from its end face and is guided through the light guide plate 20, and most of the light exits from the illumination light exit surface 20 a facing the reflective polarizing element 18.

  Illumination light emitted from the surface light source 19 (light emitted from the illumination light emission surface 20a of the light guide plate 20) is incident on the reflective polarizing element 18, and among the light, the light is incident on the reflective axis 18b of the reflective polarizing element 18. The linearly polarized light S having a parallel polarization component is reflected by the reflective polarizing element 18, passes through the light guide plate 20 of the surface light source 19, and reaches the first liquid crystal element 10 </ b> A on one surface side of the liquid crystal display device. Incident from.

  Of the light emitted from the surface light source 19 and incident on the reflective polarizing element 18, the linearly polarized light P having a polarization component parallel to the transmission axis 18 a of the reflective polarizing element 18 is transmitted through the reflective polarizing element 18. Then, the light enters the second liquid crystal element 10B on the other surface side of the liquid crystal display device from the rear side.

  When no electric field is applied between the electrodes of the first liquid crystal element 10A (V = 0), the first liquid crystal element is emitted from the surface light source 19 and reflected by the reflective polarizing element 18. As shown by the broken line on the right side of FIG. 3, the linearly polarized light S incident on 10A is converted into linearly polarized light P by the birefringence action of the liquid crystal layer 15, and is incident on the first absorbing polarizer 16. Absorbed by the absorbing polarizing plate 16.

  Further, the linearly polarized light P emitted from the surface light source 19 and transmitted through the reflective polarizing element 18 and incident on the second liquid crystal element 10B is the liquid crystal layer 15 of the second liquid crystal element 10B in the non-driven state. The linearly polarized light S is incident on the second absorption polarizing plate 17 and is absorbed by the second absorption polarizing plate 17.

  Therefore, the display in the absence of an electric field (V = 0) during the transmissive display in the first display is a black dark display.

  On the other hand, when an electric field is applied between the electrodes of the first liquid crystal element 10A so that liquid crystal molecules rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 (V> Vth), the surface light source 19 is applied. The linearly polarized light S emitted from the light, reflected by the reflective polarizing element 18 and incident on the first liquid crystal element 10A is transmitted through the liquid crystal layer 15 as the linearly polarized light S as indicated by the solid line on the left side of FIG. Further, the light passes through the first absorption polarizing plate 16 and is emitted from the one surface.

  Therefore, the display when the electric field is applied (V> Vth) in the reflective display in the first display is a bright display colored in the colors of the color filters 14R, 14G, and 14B of the first liquid crystal element 10B.

  Note that the linearly polarized light P emitted from the surface light source 19 and transmitted through the reflective polarizing element 18 and incident on the second liquid crystal element 10B is the second driving state in the non-driving state as in the case of no electric field. The liquid crystal layer 15 of the liquid crystal element 10 </ b> B is converted into linearly polarized light S and is incident on the second absorption polarizing plate 17 and is absorbed by the second absorption polarizing plate 17.

  In this way, the first display for observing the first liquid crystal element 10A of the liquid crystal display device from the front side of the first absorbing polarizing plate 16 is the surface light source 19 even in the reflective display using external light. Also in the transmissive display using illumination light from, the display when no electric field (V = 0) is a dark display and the display when an electric field is applied (V> Vth) is a normally black display.

  Note that the display as the first display surface, that is, the display of the display portion A on the inner surface of the lid of the electronic device shown in FIG. 5 is observed with the lid 3 opened as shown in FIG. In the first display, external light is also incident from the display portion B on the outer surface side of the lid 3, and the light is incident from the other surface side of the liquid crystal display device.

  However, during the first display, since the second liquid crystal element 10B on the other surface side is in an undriven state, even if external light is incident from the other surface, the light is not shown in FIG. As indicated by a two-dot chain line on the right side, the second polarizing plate 17 makes the linearly polarized light P, the second liquid crystal element 10B makes the linearly polarized light S, and the reflected polarizing element 18 reflects the second polarized light. Since the liquid crystal element 10B is changed to linearly polarized light P again and emitted from the other surface, the light incident from the other surface does not affect the display of the one surface.

  Next, the transmission path of incident light in the second display shown in FIG. 4 will be described. In FIG. 4, a transmission path indicated by a solid line is a path for reflection display using external light, and a transmission path indicated by a broken line is a path for transmission display using illumination light from the surface light source 19. .

  When the second display for observing the second liquid crystal element 10B from the front side of the second absorption polarizing plate 17 is performed by reflection display, as shown by the solid line in FIG. Of the two linearly polarized light components orthogonal to each other of the external light (non-polarized light) incident from the front side, the light of the polarization component parallel to the absorption axis of the second absorption polarizing plate 17 is absorbed by the absorption polarizing plate 17. Light having a polarization component parallel to the transmission axis 17 a of the absorption polarizing plate 17 is transmitted through the absorption polarizing plate 17 and becomes linearly polarized light P parallel to the transmission axis 17 a of the absorption polarizing plate 17. 10B.

  The linearly polarized light P incident on the second liquid crystal element 10B is subjected to the birefringence action of the liquid crystal layer 15 according to the alignment state of the liquid crystal molecules changed by the electric field applied between the electrodes of the liquid crystal element 10B. The light is emitted to the rear side of the second liquid crystal element 10B.

  That is, when no electric field is applied between the electrodes of the second liquid crystal element 10B (V = 0), that is, when the alignment state of the liquid crystal molecules is substantially twisted with a twist angle of 90 °, The linearly polarized light P transmitted through the second absorption polarizing plate 17 and incident on the second liquid crystal element 10B has a substantially vibrating surface due to the birefringence of the liquid crystal layer 15 as shown by the solid line on the right side of FIG. Thus, the linearly polarized light S rotated by 90 ° is emitted to the rear side of the second liquid crystal element 10B.

  The linearly polarized light S emitted to the rear side of the second liquid crystal element 10B is incident on the reflective polarizing element 18 whose transmission axis 18a is substantially parallel to the transmission axis 17a of the second absorption polarizing plate 17. Reflected by the reflective polarizing element 18.

  The linearly polarized light S reflected by the reflective polarizing element 18 reenters the second liquid crystal element 10B from the rear side thereof, and becomes the linearly polarized light P by the birefringence action of the liquid crystal layer 15, so that the second absorbing polarizing plate. 17, passes through the second absorption polarizing plate 17, and exits from the other surface.

  Therefore, the display in the absence of an electric field (V = 0) in the reflective display in the second display is a bright display colored in the colors of the color filters 14R, 14G, and 14B of the second liquid crystal element 10B.

  On the other hand, when an electric field is applied between the electrodes of the second liquid crystal element 10B so that liquid crystal molecules rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 (V> Vth), The linearly polarized light P transmitted through the absorption polarizing plate 17 and incident on the second liquid crystal element 10B passes through the liquid crystal layer 15 as the linearly polarized light P as shown by the solid line on the left side of FIG. Is emitted to the rear side of the liquid crystal element 10B.

  The linearly polarized light P emitted to the rear side of the second liquid crystal element 10B is transmitted through the reflective polarizing element 18, and further transmitted through the light guide plate 20 of the surface light source 19, and on the one surface side of the liquid crystal display device. The light enters the first liquid crystal element 10A from the rear side.

  The first liquid crystal element 10A on the one surface side is in a non-driven state (state in which the liquid crystal molecules of the liquid crystal layer 15 are twist-aligned) with no electric field (V = 0) in the second display. Therefore, the linearly polarized light P transmitted through the reflective polarizing element 18 and incident on the first liquid crystal element 10A from the rear side thereof is converted into the linearly polarized light S by the birefringence action of the liquid crystal layer 15 of the first liquid crystal element 10A. Then, the transmission axis 16a passes through the first absorption polarizing plate 16 which is substantially orthogonal to the transmission axis 18a of the reflective polarizing element 18, and is emitted from the one surface.

  Therefore, the display in the absence of an electric field (V = 0) in the reflective display in the second display is a black dark display.

  That is, the reflection display in the second display, that is, the display of the display portion B on the outer surface of the lid of the electronic device shown in FIG. 5 is observed with the lid 3 closed as shown in FIG. At this time, the space between the device main body 1 and the lid 3 of the electronic device is a dark portion. Therefore, the display when the electric field is applied (V> Vth) in the reflective display in the second display, that is, the The display when the incident light from the other surface is emitted from the one surface is a black dark display in which the dark part between the device body 1 and the lid 3 of the electronic device is observed from the other surface. .

  Further, when the second display is performed by transmissive display, illumination facing the reflective polarizing element 18 of the light guide plate 20 of the surface light source 19 is performed in the same manner as in the transmissive display with the one surface described above as the display surface. Of the illumination light (non-polarized light) emitted from the light exit surface 20a, linearly polarized light S having a polarization component parallel to the reflection axis 18b of the reflective polarizing element 18 is reflected by the reflective polarizing element 18, and the reflected polarized light is reflected. The linearly polarized light P having a polarization component parallel to the transmission axis 18a of the element 18 passes through the reflective polarizing element 18 and enters the second liquid crystal element 10B on the other surface side from the rear side.

  When no electric field is applied between the electrodes of the second liquid crystal element 10B (V = 0), the second liquid crystal element is emitted from the surface light source 19 and transmitted through the reflective polarizing element 18. As shown by the broken line on the right side of FIG. 4, the linearly polarized light P incident on 10B is converted into linearly polarized light S by the birefringence action of the liquid crystal layer 15, and is incident on the second absorbing polarizing plate 17. The light passes through the absorption polarizing plate 17 and exits from the other surface.

  Therefore, the display in the absence of an electric field (V = 0) in the reflective display with the other surface as the display surface is a bright display colored in the colors of the color filters 14R, 14G, and 14B of the second liquid crystal element 10B. It is.

  The linearly polarized light S emitted from the surface light source 19 and reflected by the reflective polarizing element 18 is transmitted through the light guide plate 20 and incident on the first liquid crystal element 10A in a non-driven state. Then, the light passes through the first absorption polarizing plate 16, exits from the one surface, and is absorbed by the dark portion between the device main body 1 and the lid 3 as described above.

  On the other hand, the surface light source 19 is applied when an electric field is applied between the electrodes of the second liquid crystal element 10B so that liquid crystal molecules rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 (V> Vth). The linearly polarized light P emitted from the light, transmitted through the reflective polarizing element 18 and incident on the second liquid crystal element 10B is transmitted through the liquid crystal layer 15 as the linearly polarized light P as shown by the broken line on the left side of FIG. Then, the light is emitted to the rear side of the second liquid crystal element 10 </ b> B and absorbed by the second absorption polarizing plate 17.

  Therefore, the display when the electric field is applied (V> Vth) in the transmissive display in the second display is a bright display colored in the colors of the color filters 14R, 14G, and 14B of the second liquid crystal element 10B.

  At this time as well, the linearly polarized light S emitted from the surface light source 19 and reflected by the reflective polarizing element 18 is emitted from the one surface and enters the dark portion between the device body 1 and the lid 3. Absorbed.

  As described above, the second display of the second liquid crystal element 10B of the liquid crystal display device observed from the front side of the second absorption polarizing plate 17 is a normally white display in a reflective display using external light. In the transmissive display using the illumination light from the surface light source 19, the display is normally black.

  Therefore, it is preferable to reverse the driving electric field applied to the second liquid crystal element 10B between the reflective display and the transmissive display in the second display. And reversal of brightness and darkness in the transmissive display can be eliminated.

  As described above, in this liquid crystal display device, the first and second liquid crystal elements 10A and 10B in which the liquid crystal layer 15 is provided between the front substrate 11 and the rear substrate 12 are arranged with their rear surfaces facing each other. The polarizing plates 16 and 17 are disposed on the front side of the first liquid crystal element 10A and the front side of the second liquid crystal element 10B, respectively, and the first and second liquid crystal elements are arranged in opposite directions. Between 10A and 10B, a reflective polarization element 18 that reflects one of the two linearly polarized components of the incident light that are orthogonal to each other and transmits the other polarized component is disposed. The first display using the surface as the display surface and the second display using the other surface as the display surface can be performed by reflective display using external light.

  That is, in this liquid crystal display device, light incident from the front side of this one surface is used in the reflective display with one surface (the surface observed from the front side of the first absorbing polarizing plate 16) as the display surface. Is converted into linearly polarized light by the first absorbing polarizing plate 16, and the polarization state is controlled by the liquid crystal layer 15 of the first liquid crystal element 10A to enter the reflective polarizing element 18, and among the light, Light controlled by the polarized light reflected by the reflective polarizing element 18 (linearly polarized light parallel to the reflection axis 18b of the reflective polarizing element 18) is reflected by the reflective polarizing element 18, and the reflected light is emitted from the one surface. Thus, the display observed from the one surface is a bright display, and the light controlled to the polarized light transmitting through the reflective polarizing element 18 (linearly polarized light parallel to the transmission axis 18a of the reflective polarizing element 18) is reflected polarized light. Element 18 Filtered, absorbed by the second absorbing polarizer 17 and further transmitted through the second liquid crystal element 10B, displays the observed from one surface becomes dark display.

  When the other surface (the surface observed from the front side of the second absorption polarizing plate 17) is used as the display surface, the light incident from the front side of the other surface is the second absorption polarizing plate 17. Of the second liquid crystal element 10B, the polarization state of which is controlled by the liquid crystal layer 15 of the second liquid crystal element 10B and incident on the reflective polarizing element 18, and the polarized light (reflected by the reflective polarizing element 18). Light that is controlled to be linearly polarized light parallel to the reflection axis 18b of the reflective polarizing element 18 is reflected by the reflective polarizing element 18, and the reflected light is emitted from the other surface and observed from the one surface. The display becomes bright display, and the light controlled to the polarized light that is transmitted through the reflective polarizing element 18 (linearly polarized light parallel to the transmission axis 18a of the reflective polarizing element 18) is transmitted through the reflective polarizing element 18, and the first Transmits through the liquid crystal element 10A Is absorbed by the first absorbent polarizer 16 Te, display is observed from the other surface becomes dark display.

  This liquid crystal display device absorbs light by the polarizing plate in the reflective display with the one surface as the display surface and also in the reflective display with the other surface as the display surface. It is only absorption by the plate 16 or 17, and therefore, the intensity drop of the emitted light with respect to the intensity of the incident light from the front side of the display surface is small, and also due to the wavelength dependence of the light absorption characteristics of the absorption polarizing plates 16 and 17. Since there is almost no band color of transmitted light, it is possible to perform bright and good reflective display without any band color when either one of the surfaces is used as a display surface.

  Further, in this embodiment, one of the first and second liquid crystal elements 10A and 10B, for example, between the first liquid crystal element 10A and the reflective polarizing element 18, the one liquid crystal element 10A side and Since a surface light source 19 that transmits light incident from the reflective polarizing element 18 side and emits illumination light toward the reflective polarizing element 18 is further arranged, either one of the surfaces is used as the display surface. Sometimes, a reflective display using external light and a transmissive display using illumination light from the surface light source 19 can be performed.

  Further, in this embodiment, as the polarization separation element between the first and second liquid crystal elements 10A and 10B, a transmission axis 18a and a reflection axis 18b are orthogonal to each other, and incident light is orthogonal to each other. Of the two linearly polarized light components, one linearly polarized light component having a vibration surface parallel to the reflection axis 18b is reflected, and the other linearly polarized light component having a vibration surface parallel to the transmission axis 18a is transmitted. A TN type liquid crystal element in which a polarizing element 18 is disposed and the first and second liquid crystal elements 10A and 10B are twist-aligned with a twist angle of substantially 90 ° between the front and rear substrates 11 and 12, respectively. The first and second absorption polarizers 16 and 17 on the front side of these TN type liquid crystal elements 10A and 10B are disposed so that their transmission axes 16a and 17a are substantially orthogonal to each other, and the first and second absorption polarizers 16 and 17 are disposed. The reflective polarizing element 18 between the liquid crystal elements 10A and 10B has its transmission axis 18a substantially orthogonal to the first and second ones, for example, the transmission axis 16a of the first absorption polarizing plate 16, and the other Since the second absorption polarizing plate 17 is arranged substantially in parallel with the transmission axis 17a, the high contrast of the one surface can be used as the display surface and the other surface can be used as the display surface. An indication can be obtained.

  It should be noted that the liquid crystal display device of the above-described embodiment is no matter whether the display having one surface (the surface observed from the front side of the first absorption polarizing plate 16) is a reflective display or a transmissive display. It is a Marie Black display, and the display with the other surface (the surface observed from the front side of the second absorbing polarizing plate 17) as the display surface is a normally white display when reflected display and no display when transmissive display. Although it is a display of the Marie Black display, the display when the reflective display with the one surface as the display surface and the display with the transmissive display is set as the normally white display and the display with the other surface as the display surface is the reflective display. In this case, normally black display and transmission white display may be normally white display. In this case, the first and second absorption polarizing plates 16 and 17 are respectively connected to the transmission axes 16a and 17a of FIG. Direction shown in It may be arranged in a direction substantially perpendicular against.

  In the first embodiment, one reflective polarizing element 18 is arranged between the first and second liquid crystal elements 10A and 10B. However, as in the second embodiment shown in FIG. In addition, two reflective polarizing elements 18 may be laminated between the first and second liquid crystal elements 10A and 10B so that the transmission axes 18a and the reflection axes 18b (see FIG. 1) coincide with each other. In this way, the degree of polarization of the linearly polarized light S reflected by the reflective polarizing element 18 and the linearly polarized light S transmitted through the reflective polarizing element 18 is increased, and one surface is used as a display surface. The contrast of display with the other surface as the display surface can be further increased.

  Further, in the liquid crystal display device of the above embodiment, the first and second liquid crystal elements 10A and 10B are respectively TN type liquid crystal elements, but the liquid crystal elements 10A and 10B are not limited to the TN type, STN type in which the liquid crystal molecules of the liquid crystal layer are twisted with a twist angle of 180 ° to 270 ° (preferably 200 ° to 250 °) between the front and back substrates, and the liquid crystal molecules are aligned homogeneously with the molecular long axis aligned in one direction. It may be a liquid crystal element such as a homogeneous alignment type, homeotropic alignment type, lateral electric field type, ferroelectric or antiferroelectric type, or ECB (birefringence effect) type, and when using a liquid crystal element other than the TN type, the liquid crystal The alignment direction of the liquid crystal molecules in the vicinity of the substrate before and after the element, the direction of the transmission axes 16a and 17a of the absorbing polarizers 16 and 17 disposed on the front side of the liquid crystal element, and the reflective polarizing element 18 A direction of the transmission axis 18a, may be set so as to form a display system of the normally black or normally white.

  One and the other of the first and second liquid crystal elements 10A and 10B may be different types of liquid crystal elements.

  FIG. 7 is a cross-sectional view of the liquid crystal display device according to the third embodiment of the present invention in which hatching is omitted.

  The liquid crystal display device of this embodiment includes a TN-type first liquid crystal element (hereinafter referred to as a TN-type liquid crystal element) 10A and an STN-type second liquid crystal element (hereinafter referred to as an STN-type liquid crystal element) 10Ba. Color correction for compensating for the color band due to the birefringence of the liquid crystal layer 15 of the STN type liquid crystal element 10Ba between the STN type liquid crystal element 10Ba and the second absorption polarizing plate 17 on the front side thereof. The phase difference plate 23 is disposed, and is disposed in the alignment directions 11a and 12a of liquid crystal molecules in the vicinity of the substrates 11 and 12 before and after the TN liquid crystal element 10A and on the front side of the TN liquid crystal element 10A. The relationship between the direction of the transmission axis 16a of the first absorption polarizing plate 16 and the direction of the transmission axis 18a of the reflective polarizing element 18 is set as in the above-described embodiment (see FIG. 1), and the front and rear of the STN type liquid crystal element 10Ba. Substrate 11 The orientation relationship of the liquid crystal molecules in the vicinity of 12, the transmission axis 17 a of the second absorption polarizing plate 17 disposed on the front side of the STN type liquid crystal element 10 Ba, and the direction of the transmission axis 18 a of the reflective polarizing element 18 are as follows: These are set so as to form a normally black or normally white display system.

  In the liquid crystal display device of this embodiment, the first liquid crystal element 10A is a TN type display element and the second liquid crystal element 10Ba is an STN type display element. The liquid crystal molecular alignment of the TN type liquid crystal element 10A is as follows. Directions 11a and 12a, the direction of the transmission axis 16a of the first absorption polarizing plate 16, the liquid crystal molecule alignment direction of the STN type liquid crystal element 10Ba, the direction of the transmission axis 17a of the second absorption polarizing plate 17, and the reflected polarization. Since the direction of the transmission axis 18a of the element 18 is set as described above, even when one of the surfaces is used as a display surface, it is bright, has no color, and has a high contrast. An indication can be obtained.

  In this embodiment, since the band-color compensation phase difference plate 23 is disposed between the STN type liquid crystal element 10Ba and the second absorption polarizing plate 17 on the front side thereof, the STN type liquid crystal element 10Ba side is provided. The display color due to the birefringence of the liquid crystal layer of the STN type liquid crystal element 10Ba when the surface (the surface observed from the front side of the second absorption polarizing plate 17) is used as the display surface can also be compensated. it can.

  In each of the embodiments described above, the color filters 14R, 14G, and 15B are provided in both the first and second liquid crystal elements 10A, 10B, or 10Ba, but the first and second liquid crystal elements 10A, 10B, or One or both of 10Ba may be a monochrome display element that does not include a color filter. Furthermore, both liquid crystal elements 10A, 10B, or 10Ba are monochrome display elements, and the liquid crystal elements 10A, 10B, or 10Ba are used for transmissive display. Alternatively, red, green, and blue monochromatic image data may be sequentially written, and field sequential display may be performed in which red, green, and blue colored light is sequentially emitted from the light emitting element 22 of the surface light source 19.

  In each of the above embodiments, the reflective polarizing element 18 made of a reflective polarizing plate is used as the polarization separating element between the first liquid crystal element 10A and the second liquid crystal element 10B or 10Ba. The separation element is not limited to the reflective polarizing plate as long as it reflects one polarization component of two different polarization components of incident light and transmits the other polarization component.

  FIG. 8 is an exploded side view of another polarization separation element. The polarization separation element 24 reflects one polarization component of two incident linearly polarized light components orthogonal to each other and transmits the other polarization component. It is a reflective polarizing element to be made to operate. Hereinafter, the polarization separating element 24 is referred to as a reflective polarizing element.

  The reflective polarizing element 24 reflects a circularly polarized component of one of two clockwise and counterclockwise circularly polarized components of incident light and transmits the other circularly polarized component (for example, a cholesteric liquid crystal film). A pair of phase difference plates 26 and 27 are formed so that the incident linearly polarized light is made circularly polarized and made incident on the polarization separating film 25, and the circularly polarized light emitted from the polarized light separating film 25 is made linearly polarized light. It is a thing.

  The pair of retardation plates 26 and 27 are λ / 4 retardation plates that give a quarter-wave phase difference between the ordinary light and the extraordinary light of the transmitted light, respectively. 27 are arranged with their respective slow axes substantially orthogonal to each other.

  The reflective polarizing element 24 is one of two directions orthogonal to each other and substantially shifted by 45 ° with respect to the slow axis of the pair of λ / 4 retardation plates 26 and 27, for example, the upper side in the figure. The direction of the phase difference plate (hereinafter referred to as the upper phase difference plate) 26 is 45 ° clockwise when viewed from the upper side (the outer surface side of the upper phase difference plate 26) (the lower phase difference plate 27). Two linearly polarized light beams having a transmission axis in a direction shifted 45 ° counterclockwise with respect to the slow axis and a reflection axis in the other direction orthogonal to the transmission axis, and orthogonal to each other of incident light of incident light Of the components, one linearly polarized light component having a vibration surface parallel to the reflection axis is reflected, and the other linearly polarized light component having a vibration surface parallel to the transmission axis is transmitted.

  That is, as shown in FIG. 8, the reflective polarizing element 24 converts linearly polarized light S parallel to the reflection axis out of light incident from one surface side thereof, for example, from the upper side in the figure, into the upper retardation plate. 26 is incident on the polarization separation film 25 as circularly polarized light R1 clockwise in the figure, and the linearly polarized light P parallel to the transmission axis is separated as circularly polarized light R2 counterclockwise in the figure by the upper retardation plate 26. Of the light incident on the film 25 and incident from the other surface side, that is, the lower side in the figure, the linearly polarized light S parallel to the reflection axis is converted into the counterclockwise circularly polarized light by the lower phase difference plate 27. R2 is incident on the polarization separation film 25 and linearly polarized light P parallel to the transmission axis is incident on the polarization separation film 25 by the lower retardation plate 27 as clockwise polarized light R1 in the drawing.

  In FIG. 8, for the sake of convenience, the rotational directions (directions of the arrows) of the circularly polarized light R1 and R2 are shown in the same direction as viewed from above in the figure. Of these circularly polarized lights R1 and R2, , The rotation direction seen from the direction toward the traveling direction of the circularly polarized light R1, R2 from the upper side to the lower side is the same direction as in the figure, and the direction from the lower side to the upper side in the figure toward the traveling direction of the circularly polarized light R1, R2 The direction of rotation seen from the direction is the reverse of the figure.

  On the other hand, the polarized light separating film 25 reflects the circularly polarized light R1 clockwise in the figure out of the light incident as circularly polarized light R1 and R2 by the upper phase difference plate 26 from one surface side, for example, the upper side in the figure. Of the light that has been transmitted as circularly polarized light R1, R2 by the lower phase difference plate 27 from the other surface side, that is, the lower side in the figure, is transmitted through the counterclockwise circularly polarized light R2 in the figure. It has a polarization separation characteristic that reflects counterclockwise circularly polarized light R2 and transmits clockwise circularly polarized light R1 in the figure.

  Therefore, among the light incident from the upper side in the figure, the light that is made the circularly polarized light R1 clockwise by the upper phase difference plate 26 and incident on the polarization separation film 25 is reflected by the polarization separation film 25, The reflected light (circularly polarized light counterclockwise in the figure) R2 is converted to linearly polarized light S parallel to the reflection axis by the upper phase difference plate 26 and emitted upward, and the upper phase difference plate 26 counterclockwise in the figure. Light that has entered the polarization separation film 25 as circularly polarized light R2 passes through the polarization separation film 25 and enters the lower retardation film 27, and is parallel to the transmission axis by the lower retardation film 27. It is set as the linearly polarized light P and is emitted downward.

  In addition, among the light incident from the lower side in the figure, the light that has been made the circularly polarized light R2 counterclockwise in the figure by the lower phase difference plate 27 and incident on the polarization separation film 25 is reflected by the polarization separation film 25. The reflected light (clockwise circularly polarized light in the figure) R1 is converted to linearly polarized light S parallel to the reflection axis by the lower phase difference plate 27 and emitted downward, and the lower phase difference plate 27 Light that has entered the polarization separation film 25 as the clockwise circularly polarized light R1 in the figure passes through the polarization separation film 25 and enters the upper retardation plate 26, and the transmission axis is transmitted by the upper retardation plate 26. And is emitted upward.

  As described above, the reflective polarizing element 24 reflects one of the two linearly polarized light components of the incident light that are orthogonal to each other and has a vibration surface parallel to the reflection axis, and is parallel to the transmission axis. The other polarization component having the vibration surface is transmitted. Therefore, even if this reflective polarizing element 24 is used instead of the reflective polarizing element 18 composed of the reflective polarizing plate of each of the above-described embodiments, Similar effects can be obtained.

  Further, the liquid crystal display device of each of the above embodiments includes either one of the first and second liquid crystal elements 10A, 10B, or 10Ba (first liquid crystal element in each of the above embodiments) 10A, and the first and second liquid crystal display devices. The liquid crystal element 10A, 10B or 10Ba between the liquid crystal elements 10A, 10B or 10Ba (the reflective polarizing element 18 made of a reflective polarizing plate or the reflective polarizing element 24 shown in FIG. 8) and the one liquid crystal element 10A side When a surface light source 19 that transmits light incident from the reflective polarizing element 18 side and emits illumination light toward the reflective polarizing element 18 is disposed and one surface is used as a display surface, the other surface is Even when the display surface is used, both the reflective display using outside light and the transmissive display using illumination light from the surface light source 19 can be displayed. Omit one side and display side A display for the display of the display surface and the other surface may be only reflective display utilizing external light.

10A, 10B ... TN type liquid crystal element 10Ba ... STN type liquid crystal element 11, 12 ... Substrate 14R, 14G, 14B ... Color filter 15 ... Liquid crystal layer 16, 17 ... Absorbing polarizing plate 16a, 17a ... Transmission axis 18 ... Reflective polarizing element ( Polarization separation element)
DESCRIPTION OF SYMBOLS 18a ... Transmission axis 18b ... Reflection axis 19 ... Surface light source 20 ... Light guide plate 20a ... Illumination light emission surface 22 ... Light emitting element 23 ... Phase difference plate 24 ... Reflection polarizing element (polarization separation element)
25 ... Cholesteric liquid crystal film 26,27 ... λ / 4 retardation plate

Claims (5)

A liquid crystal layer that controls the polarization state of transmitted light according to the applied electric field is provided between the front substrate that is the viewing side of the display and the rear substrate that opposes the front substrate. First and second liquid crystal elements arranged in opposite directions with their rear surfaces facing each other;
A first absorbing polarizer disposed on the front side of the first liquid crystal element and absorbing one of the two linearly polarized components of incident light orthogonal to each other and transmitting the other polarized component;
A second absorbing polarizer disposed on the front side of the second liquid crystal element and absorbing one of the two linearly polarized light components of incident light orthogonal to each other and transmitting the other polarized light component;
A polarization separation element that is disposed between the first and second liquid crystal elements and reflects one of the two different polarization components of incident light and transmits the other polarization component;
A liquid crystal display device comprising:   Between one of the first and second liquid crystal elements and the polarization separation element disposed between the first and second liquid crystal elements, from the one liquid crystal element side and the polarization separation element side The liquid crystal display device according to claim 1, further comprising a surface light source that transmits incident light and emits illumination light toward the polarization separation element.   The polarization separation element disposed between the first and second liquid crystal elements has a transmission axis and a reflection axis in directions orthogonal to each other, and the reflection axis of two linearly polarized light components of incident light orthogonal to each other. 2. A reflective polarizing element that reflects one linearly polarized light component having a vibration surface parallel to the light beam and transmits the other linearly polarized light component having a vibration surface parallel to the transmission axis. 2. A liquid crystal display device according to 2.   Each of the first and second liquid crystal elements is a TN liquid crystal element in which liquid crystal molecules are twist-aligned with a twist angle of substantially 90 ° between the front and back substrates, and each of the first and second TN liquid crystal elements. The first and second absorption polarizers on the front side are arranged with their transmission axes substantially orthogonal to each other, and the reflective polarizing element between the first and second TN liquid crystal elements has its transmission axis. 4 is arranged so as to be substantially perpendicular to the transmission axis of one of the first and second absorption polarizing plates and substantially parallel to the transmission axis of the other absorption polarizing plate. A liquid crystal display device according to 1.   At least one of the first and second liquid crystal elements is an STN type liquid crystal element in which liquid crystal molecules are twist-aligned with a twist angle of 180 ° to 270 ° between the front and rear substrates, and The orientation direction of the liquid crystal molecules in the vicinity, the direction of the transmission axis of the absorbing polarizing plate arranged on the front side of the STN type liquid crystal element, and the direction of the transmission axis of the reflective polarizing element between the first and second liquid crystal elements The liquid crystal display device according to claim 3, wherein the liquid crystal display device is set so as to form a normally black or normally white display system.

Images