JP4774957B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device capable of controlling the visual field of display.

  The liquid crystal display device includes a liquid crystal display element having a screen region in which a plurality of pixels that control light transmission are arranged in a matrix, and the liquid crystal display element is disposed on a side opposite to the observation side of the liquid crystal display element. And a surface light source for irradiating illumination light.

  By the way, liquid crystal display devices are used in various electronic devices. For example, electronic devices used in various environments, such as mobile phones, display the display in the front direction (near the normal line of the liquid crystal display element). There is a risk of being peeped from other than the user of the electronic device from an oblique direction.

Therefore, a louver element (see Patent Document 1) in which a plurality of light transmission layers and light absorption layers are alternately stacked is disposed on one surface side of the liquid crystal display element, and the visual field of display is set in the front direction by the louver element. It is considered to limit the angle range to a narrow angle range (direction near the normal line of the liquid crystal display element).
JP 2000-137294 A

  However, in the liquid crystal display device including the louver element, the display field of view is limited by the louver element, so that the narrow field display is fixed, and the liquid crystal display element inherently has a wide viewing angle display. I can't.

  The present invention provides a liquid crystal display device capable of performing a wide-field display in which a plurality of people can see the display and a high-security narrow-field display without fear of peeping at the display from an oblique direction. It is intended to provide.

  The liquid crystal display device according to the present invention includes a liquid crystal display element having a screen region in which a plurality of pixels for controlling light transmission are arranged in a matrix, and the liquid crystal display element is disposed on a side opposite to an observation side of the liquid crystal display element. A surface light source for irradiating illumination light toward the element, a plurality of transparent layers and an electrochromic layer have a laminated structure in which the liquid crystal display element is alternately arranged in a direction parallel to the surface of the liquid crystal display element, and the surface of the liquid crystal display element And a pair of electrodes for energizing the plurality of electrochromic layers at both ends in a direction orthogonal to the laminating direction. The liquid crystal display A field-of-view control element disposed on one surface side of the element so that the interface between the transparent layer and the electrochromic layer is substantially parallel to the normal direction of the liquid crystal display element, That.

  In this liquid crystal display device, the thickness of the electrochromic layer of the visual field control element in the stacking direction is preferably set to 10 μm to 100 μm.

  The visual field control element is preferably arranged between the surface light source and the liquid crystal display element.

  The liquid crystal display device of the present invention narrows the visual field of display by energizing a plurality of electrochromic layers of the visual field control element, and when the electrochromic layer is not energized, Light incident from the surface passes through the plurality of electrochromic layers and the transparent layer therebetween and exits from the other surface of the visual field control element, and the display of the liquid crystal display element displays illumination light from the surface light source. It is visible with a wide field of view corresponding to the spread angle.

  On the other hand, when a plurality of electrochromic layers of the visual field control element are energized, the electrochromic layer is colored, and among the light incident on the visual field control element from one surface thereof, the light directly incident on the electrochromic layer and The transparent layer is inclined in a direction larger than the inclination angle corresponding to the thickness of the transparent layer in the stacking direction of the transparent layer and the electrochromic layer with respect to the normal direction of the liquid crystal display element. The light traveling forward is shielded by the colored electrochromic layer, the front light traveling in the direction near the normal line of the liquid crystal display element, and the thickness of the transparent layer in the stacking direction with respect to the normal direction. Light traveling in a tilted direction within the range is transmitted through the plurality of transparent layers and emitted from the other surface of the visual field control element, and the display field of view of the liquid crystal display element is It becomes narrow angular range (direction near the normal line of the liquid crystal display device).

  Therefore, according to this liquid crystal display device, the viewing angle can be divided into a wide-field display in which the display can be viewed by a plurality of people and a high-security narrow-field display in which there is no risk of being peeped at the display from an oblique direction. Can be controlled.

  In this liquid crystal display device, it is preferable to set the thickness of the electrochromic layer of the visual field control element in the stacking direction to 10 μm to 100 μm. By doing so, the light shielding property due to coloring of the electrochromic layer is sufficient. The display of the liquid crystal display element is hardly visible from an oblique direction, and a narrower-field display with higher security is performed, and the line pattern viewed from the front direction due to the color development of the electrochromic layer is made inconspicuous and narrow. A high quality image can be displayed even in the visual field display.

  The visual field control element is preferably disposed between the surface light source and the liquid crystal display element. By doing so, the line pattern seen from the front direction due to the color development of the electrochromic layer is almost visible. Can be eliminated.

  1 to 4 show an embodiment of the present invention, and FIG. 1 is an exploded perspective view of a liquid crystal display device.

  As shown in FIG. 1, the liquid crystal display device includes a liquid crystal display element 1 having a screen region 1a in which a plurality of pixels (not shown) for controlling light transmission are arranged in a matrix, and observation of the liquid crystal display element 1. A surface light source 8 disposed on the side opposite to the side (the upper side in FIG. 1) and irradiating illumination light toward the liquid crystal display element 1, and a visual field control element disposed on one surface side of the liquid crystal display element 1 15.

  Although the internal structure of the liquid crystal display element 1 is not shown, a pair of transparent substrates 2 and 3 joined via a frame-shaped sealing material 4 surrounding the screen region 1a and the substrates 2 and 3 are opposed to each other. Liquid crystal sealed in a region surrounded by the sealing material 4 between the pair of substrates 2 and 3 and a transparent electrode which is provided on each inner surface and forms a plurality of pixels arranged in a matrix by regions facing each other. And a pair of polarizing plates 5 and 6 disposed on the outer surfaces of the pair of substrates 2 and 3, respectively.

  The liquid crystal display element 1 includes a plurality of pixel electrodes arranged in a matrix in the row direction and the column direction on the inner surface of one substrate 2, and the arrangement region of the plurality of pixel electrodes on the inner surface of the other substrate 3. An active matrix liquid crystal display element provided with a single film-like counter electrode facing each other, and an inner surface of the one substrate 2 is provided with an active element comprising TFTs respectively connected to the plurality of pixel electrodes, and each row A plurality of scanning lines for supplying gate signals to the TFTs and a plurality of data lines for supplying data signals to the TFTs in each column are provided.

  The one substrate 2 has a driver mounting portion 2a extending outward from the other substrate 3, and the plurality of gate lines and data lines are formed from an LSI mounted on the driver mounting portion 2a. Connected to the display driver 7.

  Further, an alignment film is provided on the inner surfaces of the pair of substrates 2 and 3 so as to cover the electrodes, and the liquid crystal molecules of the liquid crystal layer are defined by the alignment film between the pair of substrates 2 and 3. It is oriented in the orientation state.

  The liquid crystal display element 1 includes a TN or STN type in which liquid crystal molecules are twist-aligned, a vertical alignment type in which liquid crystal molecules are aligned substantially perpendicular to the surfaces of the substrates 2 and 3, and a substrate without twisting the liquid crystal molecules. The liquid crystal display element is either a horizontal alignment type that is aligned substantially parallel to two or three planes or a bend alignment type that bends liquid crystal molecules, or a ferroelectric or antiferroelectric liquid crystal display element. The pair of polarizing plates 5 and 6 are arranged with their transmission axes oriented so as to obtain good contrast characteristics.

  In the liquid crystal display element 1, a vertical electric field (electric field in the thickness direction of the liquid crystal layer) is generated between the electrodes provided on the inner surfaces of the pair of substrates 2 and 3 to change the alignment state of the liquid crystal molecules. For example, a comb-like first and second electrode for forming a plurality of pixels is provided on the inner surface of one of the pair of substrates 2 and 3, and a horizontal electric field ( A lateral electric field control type that changes the alignment state of the liquid crystal molecules by generating an electric field in a direction along the substrate surface may be used.

  Further, the liquid crystal display element 1 may be a normally white mode display element or a normally black mode display element.

  The surface light source 8 is made of a plate-shaped transparent member such as an acrylic resin plate, and is formed with an incident end surface 10 on which light is incident on one end surface thereof, and is opposed to the liquid crystal display element 1 out of two opposing plate surfaces. An exit surface 11 for emitting light incident from the entrance end surface 10 is formed on the plate surface to be reflected, and a reflection surface 12 for reflecting the light incident from the entrance end surface 10 toward the exit surface 11 is formed on the other plate surface. The formed light guide plate 9, a plurality of light emitting elements 13 such as LEDs (light emitting diodes) arranged to face the incident end face 10 of the light guide plate 9, and the output surface 11 of the light guide plate 9. The diffuser plate 14 is arranged.

  The surface light source 8 guides the light from the plurality of light emitting elements 13 by the light guide plate 9 and emits the light from the emission surface 11, diffuses the light by the diffusion plate 14, and the method of the liquid crystal display element 1. Illumination light having a substantially uniform intensity distribution is emitted toward the liquid crystal display element 1 in the direction normal to the line direction and in the direction inclined from the normal line.

  Note that the reflection surface 12 of the light guide plate 9 is also an internal reflection surface that totally reflects the light incident from the incident end surface 10 at the interface between the light guide plate surface and the outside air (air). It may be a reflective surface that is reflected by a reflective film (not shown) provided on the light guide plate surface.

  Further, the surface light source 8 of this embodiment has a diffuser plate 14 disposed so as to oppose the light exit surface 11 of the light guide plate 9, but between the light exit surface 11 of the light guide plate 9 and the diffuser plate 14. Alternatively, a prism sheet (not shown) is further arranged on the exit surface side of the diffuser plate 14, and the light emitted from the exit surface 11 of the light guide plate 9 is spread at a uniform angle by the diffuser plate 14 and the prism sheet. The liquid crystal display element 1 may be irradiated as distributed illumination light.

  Further, the liquid crystal display device includes the liquid crystal display element 1 having color filters of three colors of red, green, and blue respectively facing a plurality of pixels, and irradiates white illumination light from the surface light source 8. Or a field sequential liquid crystal display device in which the liquid crystal display element 1 is provided with the color filter and the surface light source 8 is selectively irradiated with illumination light of three colors of red, green, and blue. .

  On the other hand, the visual field control element 15 has a laminated structure in which a plurality of transparent layers 16 and electrochromic layers 17 are alternately arranged in a direction parallel to the surface of the liquid crystal display element 1, and the surface of the liquid crystal display element 1. A pair of electrodes 18 and 19 for energizing the plurality of electrochromic layers 17 are provided at both ends in a direction orthogonal to the laminating direction. It consists of optical elements.

  FIG. 2 is an enlarged perspective view of a part of the visual field control element 15. The thickness t of the visual field control element 15 is set to 100 μm to 2 mm, preferably 500 μm to 1000 μm. The thickness d1 in the direction is set to 30 μm to 1 mm, preferably about 1000 μm, and the film thickness d2 of the plurality of electrochromic layers 17 in the stacking direction is set to 10 μm to 100 μm, preferably about 10 μm.

  The visual field control element 15 is formed by thinly applying an electrochromic substance such as viologen on one surface of a polymer film having no light diffusibility, such as polymethyl methyl acrylate, polycarbonate, polypropylene, polyvinyl acetate, and polystyrene. Hundreds of materials are laminated to a thickness about the width of the screen of the liquid crystal display element 1, and the visual field control is performed on the laminate along a plane perpendicular to the polymer film surface. The element 15 is sliced to a thickness t, and electrodes 18 and 19 are formed on both end faces of the sliced body. The transparent layer 16 is formed by the polymer film, and the electrochromic material coating layer is electrochromic. Layer 17 is formed.

  The visual field control element 15 of this embodiment has a pair of electrodes 18 and 19 made of an elongated metal plate having terminal portions 18a and 19a projecting outward from the visual field control element 15 at one end. The pair of electrodes 18 and 19 may be formed of a conductive adhesive coating layer, although they are attached to both end faces with a conductive adhesive (not shown).

  In this liquid crystal display device, the visual field control element 15 is disposed between the surface light source 8 and the liquid crystal display element 1, and the interface between the transparent layer 16 and the electrochromic layer 17 is used as a method of the liquid crystal display element 1. The transparent layer 16 and the electrochromic layer 17 are arranged so as to be substantially parallel to the line direction and to be substantially parallel to the horizontal direction of the screen of the liquid crystal display element 1.

  Further, a visual field control power source (not shown) for applying a DC voltage whose polarity is alternately reversed between the electrodes 18 and 19 is applied to the terminal portions 18a and 19a of the pair of electrodes 18 and 19 of the visual field control element 15. It is connected.

  The visual field control power supply is based on a visual field selection signal supplied from a circuit unit (not shown) of the electronic device by operating a visual field selection key provided in an electronic device such as a mobile phone equipped with a liquid crystal display device. When the controlled and narrow field is selected, the DC voltage is applied between the electrodes 18 and 19 of the field control element 15.

  In this liquid crystal display device, a surface light source 8 that irradiates illumination light toward the liquid crystal display element 1 is disposed on the opposite side of the liquid crystal display element 1 from the observation side, and the surface light source 8 and the liquid crystal display element 1 are disposed. In order to energize the plurality of electrochromic layers 17 at both ends in a direction perpendicular to the laminating direction, the plurality of elongated film-like transparent layers 16 and the electrochromic layers 17 are alternately stacked. The visual field control element 15 provided with a pair of electrodes 18 and 19 is disposed with its interface between the transparent layer 16 and the electrochromic layer 17 substantially parallel to the normal direction of the liquid crystal display element 1. Therefore, by controlling the energization of the plurality of electrochromic layers 17 of the visual field control element 15, the range of the viewing angle can be controlled in the wide field display and the narrow field display.

  That is, this liquid crystal display device narrows the visual field of display by energizing the plurality of electrochromic layers 17 of the visual field control element 15. When the electrochromic layer 17 is not energized, the surface light source 8 Irradiated light that has entered the visual field control element 15 from one surface thereof passes through the plurality of electrochromic layers 17 and the transparent layer 16 therebetween, and is emitted from the other surface of the visual field control element 15.

  FIG. 3A is a transmitted ray diagram when the electrochromic layer 17 of the visual field control element 15 of the liquid crystal display device is not energized (hereinafter referred to as visual field control OFF), and the electrochromic layer of the visual field control element 15 17 is substantially colorless and transparent in a non-energized state, and therefore, illumination light with a large divergence angle irradiated from the surface light source 8 is transmitted through the visual field control element 15 without being blocked by the electrochromic layer 17. To do.

  Therefore, when this visual field control is OFF, illumination light with a wide divergence angle is incident on the liquid crystal display element 1, and the display on the liquid crystal display element 1 has a wide visual field corresponding to the divergence angle of the illumination light from the surface light source 8. It looks in.

  On the other hand, when the plurality of electrochromic layers 17 of the visual field control element 15 are energized, the electrochromic layer 17 is colored by energization (for example, in the case of an electrochromic layer made of viologen, it is colored amber).

  FIG. 3B is a transmitted ray diagram when the electrochromic layer 17 of the visual field control element 15 of the liquid crystal display device is energized (hereinafter referred to as visual field control ON). Of the light irradiated and incident on the visual field control element 15 from one surface thereof, the light directly incident on the electrochromic layer 17 and the transparent layer 16 are made to be in the normal direction of the liquid crystal display element 1. The light traveling in the direction in which the transparent layer 16 and the electrochromic layer 17 are laminated in a direction inclined more than an inclination angle corresponding to the thickness of the transparent layer 16 in the lamination direction is caused by the colored electrochromic layer 17. In a direction that is shielded and tilted within the range of the thickness of the transparent layer 16 in the stacking direction with respect to the front light that travels in the direction near the normal of the liquid crystal display element 1 and the normal direction Cow light is transmitted through the plurality of transparent layers 16 is emitted from the other surface of the viewing angle control element 15.

  Therefore, when this visual field control is ON, illumination light whose divergence angle is limited to a narrow angle near the normal line of the liquid crystal display element 1 is incident on the liquid crystal display element 1, and the display visual field of the liquid crystal display element 1 is displayed. Is a narrow angle range in the front direction (direction near the normal line of the liquid crystal display element 1).

  In addition, when the visual field control is ON, the entire screen of the liquid crystal display element 1 appears colored in the color of the electrochromic layer 17 when viewed from an oblique direction inclined with respect to the front direction. The display of the liquid crystal display element 1 cannot be visually recognized from the direction.

  Therefore, according to this liquid crystal display device, it is possible to perform a wide-field display in which a display can be viewed by a plurality of persons and a highly secure narrow-field display without fear of being peeped at by another person from an oblique direction. Can do.

  In addition, as described above, the liquid crystal display device is configured so that the visual field control element 15 has the lamination direction of the transparent layer 16 and the electrochromic layer 17 substantially parallel to the horizontal direction of the screen of the liquid crystal display element 1. Due to the arrangement, it is possible to perform a narrow field display with a narrow field of view in the left-right direction of the screen.

  FIG. 4 is an intensity distribution diagram of the emitted light when the field of view control of the liquid crystal display device is OFF and when the field of view control is ON. In the figure, the negative angle is the normal direction of the liquid crystal display element 1 (the direction of 0 °). On the other hand, the left angle and the positive angle of the screen as viewed from the viewing side are the right angle of the screen as viewed from the viewing side with respect to the normal direction.

  The intensity distribution of the emitted light when the visual field control is ON shown in FIG. 4 is a distribution in which the emitted light intensity is high in an angle range of about −40 ° to 40 °. The emission angle range corresponds to the pitch of the electrochromic layer 17 of the visual field control element 15 (thickness d1 in the stacking direction of the transparent layer 16) and the thickness t of the visual field control element 15, and the pitch of the electrochromic layer 17 Or the thickness t of the visual field control element 15 is increased, the emission angle range of high-intensity light when the visual field control is turned on becomes narrower.

  Therefore, the visual field of display when visual field control is ON can be arbitrarily set by selecting one or both of the pitch of the electrochromic layer 17 of the visual field control element 15 and the thickness t of the visual field control element 15. .

  Since the thickness t of the visual field control element 15 is related to the thickness of the entire liquid crystal display device, the pitch of the electrochromic layer 17 is reduced when narrowing the visual field range of the narrow visual field display. Is preferred.

  Further, in this liquid crystal display device, since the thickness d2 of the electrochromic layer 17 of the visual field control element 15 is set to 10 μm to 100 μm as described above, the electrochromic layer 17 is colored. The light-shielding property is sufficiently high, the display of the liquid crystal display element 1 is hardly visible from an oblique direction, a more secure narrow-field display is performed, and the line pattern seen from the front direction due to the coloration of the electrochromic layer 17 Can be made inconspicuous and a high-quality image can be displayed even in a narrow-field display.

  The thickness d2 of the electrochromic layer 17 in the stacking direction is preferably set to about 10 μm. By doing so, the light-shielding property due to coloring of the electrochromic layer 17 is sufficiently increased, and The line pattern seen from the front direction due to the color development of the electrochromic layer 17 can be made less noticeable.

  Further, in this liquid crystal display device, since the visual field control element 15 is disposed between the surface light source 8 and the liquid crystal display element 1, the line pattern seen from the front direction due to the color development of the electrochromic layer 17 can be obtained. It is almost invisible, and the display quality during narrow field display can be improved.

  Note that the visual field control element 15 may be arranged on the observation side of the liquid crystal display element 1, and in this case, a wide-field display in which a plurality of people can see the display and a display from another side from an oblique direction. It is possible to perform narrow-field display with high security without fear of being peeped.

1 is an exploded perspective view of a liquid crystal display device showing an embodiment of the present invention. FIG. 3 is an enlarged perspective view of a part of a visual field control element of the liquid crystal display device. FIG. 4 is a transmitted light diagram when visual field control is OFF and visual field control is ON of the liquid crystal display device. FIG. 3 is an intensity distribution diagram of emitted light when visual field control is OFF and visual field control is ON of the liquid crystal display device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element, 1a ... Screen area | region, 8 ... Surface light source, 15 ... Visual field control element, 16 ... Transparent layer, 17 ... Electrochromic layer, 18, 19 ... Electrode.

Claims (3)

A liquid crystal display element having a screen region in which a plurality of pixels for controlling light transmission are arranged in a matrix, and
A surface light source disposed on the opposite side of the liquid crystal display element from the observation side and irradiating illumination light toward the liquid crystal display element;
A plurality of transparent layers and electrochromic layers have a laminated structure in which they are alternately arranged in a direction parallel to the surface of the liquid crystal display element, and are formed in a film shape having an incident / exit surface parallel to the surface of the liquid crystal display element. A pair of electrodes for energizing the plurality of electrochromic layers is provided at both ends in a direction orthogonal to the laminating direction, and the transparent layer and the electro A liquid crystal display device comprising: a visual field control element arranged so that an interface with the chromic layer is substantially parallel to a normal direction of the liquid crystal display element.   The liquid crystal display device according to claim 1, wherein a thickness of the electrochromic layer of the visual field control element is set to 10 μm to 100 μm.   The liquid crystal display device according to claim 1, wherein the visual field control element is disposed between the surface light source and the liquid crystal display element.

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